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The following is a curated list of insect systems for which some degree of study has been dedicated to the relationship between host shifting and speciation. This list was first published in: Forbes AA, Devine SN, Hippee AC, Tvedte ES, Ward AKJ, Widmayer HA, Wilson CJ. 2017. Revisiting the particular role of host shifts in initiating insect speciation. Evolution 71:1126-1137link to paper

For each system, the following information has been collected (quote from Forbes et al. 2017): "1) species name, 2) order and family, 3) common name (if applicable), 4) names of host plants, 5) evidence for (or against) host-associated genetic differences indicative of restricted gene flow, 6) evidence suggesting that host use has resulted in the evolution of reproductive isolation, including the specific form(s) of reproductive isolating barriers measured, 7) whether viable, fertile hybrids are possible (as a proxy for current “species” status; see definition of species above), and 8) whether there exists a historical record of the host shift."

Systems are then sorted into categories reflecting what can be definitively said regarding the relationship between the host shift, the evolution of reproductive isolation, and speciation. The following table (also from Forbes et al. 2017) briefly summarizes criteria required for inclusion in each category, though more comprehensive descriptions of criteria and other caveats may be found in the original manuscript

 

 

Host shift has initiated speciation

Host shift has contributed to speciation

Host shift has resulted in evolution of reproductive isolation

Host shift is correlated with genetic structure

No evidence of host-associated genetic structure

Host-associated genetic differences

X

X

X

X

 

Host use is connected to reproductive isolation

X

X

X

 

 

Populations were incompletely isolated

X

X

 

 

 

Reproductively isolated populations did not exist before the host shift

X

 

 

 

 

This wiki is intended as a living document. New publications, new data, or our own incorrect interpretation of previous studies may warrant changes to category assignments. A record of edits subsequent to the 2017 publication may be found herePLEASE send new studies, new evidence relevant to existing systems, or evidence that may disagree with conclusions in the current table to andrew-forbes "at" uiowa.edu. Researchers working in related fields and who are interested are invited to collaborate in this effort.

AssignmentSummary of system and explanation of assignmentSpecies nameOrder: FamilyCommon Name(s) of DescriptionHostsA) Host-associated genetic differences?Explanation and support for AB) Host use results in some reproductive isolation?Explanation / support for BC) Hybrids possible in nature?D) Natural history record of host shift?
2No genetic differences detected using AFLP markers, but allochrony and differences in EAG responses suggest genetic differences (though these could be plastic traits). Mating behaviors observed near host plants, so if EAG response differences indicate host fidelity then host plant association = RIAcrobasis vaccinii Lepidoptera: Pyralidaecranberry fruitworm cranberry and blueberryNot detectedAFLPs; Medina et al. 2014YesAllochrony; EAG responses suggest potential differences in host plant responses (Medina et al. 2014). This latter plus on-host mating = RI caused by host use. Mating-related behaviors (but no copulation) observed on and near cranberry vines (Sharma 2005)No records found100 years ago: start of widespread cultivation of blueberries and cranberries (Hancock et al. 2008) Currently has a wide distribution and also infests beach plums, huckleberries and "dangle-berries:" (Mallampalli and Isaacs 2002)
3Genetic differences between moths on different hosts. RI in the form of ecological hybrid inviability -> hybrids are less fit than parents on either parental host plant. Not yet completely reproductively isolated, at least based on lab studies that show hybrids are possible.Acrocercops transectaLepidoptera: Gracillariidaeleaf-mining mothJapanese walnut and Lyonia ovalifoliaYesmtDNA sorts populations into different clades (Ohshima 2008)YesPhysiological hybrid inviability: hybrids less fit on either host; Ohshima 2008 Maybe (lab hybrids possible; Ohshima 2008)No. Relationship deduced from collections and sequence data (Ohshima 2008)
1Genetic differences between grasshoppers in the two habitats, but no reproductive isolating barriers have been measured.Acrostira bellamyiOrthoptera: PamphagidaeLa Gomera flightless grasshoppershrubland plants vs laurelYesmtDNA  haplotype differences between shrubland and laurel forest ecotypes (Hernandez-Teixidor et al. 2014)No records foundN/ANo records foundPopulation genetics suggest that shrubland was ancestral habitat, but shift not documented. (Hernandez-Teixidor et al. 2014)
3Hybrids possible, but but may be very, very rare. Host use definitely related to RI: immigrant inviability AND habitat isolation.Acyrthosiphon pisumHemiptera: Aphididaepea aphidred clover / alfalfaYes(Via 1991a, Via 1991b, Via 1994)Yes Immigrant inviability -> migrants that feed on alternative host will die (Caillaud and Via 2000). Also habitat isolation: aphids orient to natal hosts (Barrette et al. 1994; Via 1991; Via et al. 2000). Also extrinsic hybrid inviability - hybrids perform poorly on parental hostsYes (Smith and MacKay 1989; Via 1994, 1999; Caillaud and Via 2012)No; Not clear if shift occurred in Europe or N. America (Europe most likely; Simon et al. 2003)
2Several host-related isolating barriers, but it is not even clear that these species are sister to one another, let alone still in the process of speciation. Host use results in RI, but cannot say that it has contributed to speciation here.Altica fragariae / Altica viridicyaneaColeoptera: Chrysomelidaeflea beetlesGeranium nepalens and Duchesnea indicaYesStrongly differentiated at COI, EF1a, ITS2: Xue et al. 2014YesHabitat isolation via host plant preference, immigrant inviability, and some extrinsic hybrid inviability for some crosses (Xue et al. 2009)Possible but unlikely. Lab hybrids can be created but show lower viability (Xue et al. 2007)No
0No evidence of host-associated genetic differences.Aphidius transcaspicusHymenoptera: Braconidaebraconid waspaphids on fruit (prunus) treesNomtDNA and 7 microsatellites. Lots of geographic variation, but no evidence of host associated differences (Lozier et al. 2009)NoDue to lack of HAD between populations gene flow only appears to be limited by geography, not by host use (Lozier et al. 2009)No records foundNo
0No evidence of host-associated genetic differences. Hosts specialize on several different plants however the parisitoids have high gene flow and demonstrate an ability to quickly adapt and oviposit on different aphid host-racesAphidus erviHymenoptera: BraconidaeN/Apea aphids in clover and alfalfa (and other plants)No6 microsatellites, no host associated OR geographic structure across range (Plasman 2016 [dissertation in altoff lab])UnclearAphids have different defenses depending on their host plants. However in the lab  A. ervi has shown an ability to adapt to these defenses well due to high genetic variation (Plasman 2016). It appears that only oviposition, and not mating, occurs on host (Plasman 2016; Henter, H. J. and S. Via. 1995)Yes, although they are the same species. High gene flow between populations (Plasman 2016 [dissertation in altoff lab])Host invaded N.A. in 1800's and specializes on several plants. A. Ervi introduced in the 60's to target aphid and as a result quickly spread to many plants where aphid is present (Mackauer and Finlayson 1967)
1Host-associated structure found for aphids on curcubits vs. other hostsAphis gossypiiHemiptera: Aphididaecotton-melon aphidMany, many hosts. Genetic structure shows lots of host associated patterns.YesEvidence of genetic structure from RAPD data associated with host plant species (Vanlerberghe-Masutti and Chavigny 1998). UnclearReduced fertility if transferred to a different host plant species (Blackman & Eastop 1984). Not really immigrant inviability because these are asexual and already cannot interbreed.Asexual, so no.No. These are just several aphid populations found on different host plants.
1Nine cryptic species, but not known whether host association has affected reproductive isolation or speciaitonApiomorpha minorHemiptera: Eriococcidaescale insectEucalyptus speciesYesKaryotype and mtDNA variation identified 9 lineages, and in some cases these were associated with different host use (Mills and Cook 2014)No records foundN/A No record of host shift. Studies are searches for cryptic diversity.
1Five genetically different lineages, each restricted to a specific set of eucalypt species. No evidence that host shifts were definitiely associated with genetic differences or that they caused speciation.Apiomorpha munitaHemiptera: Eriococcidaescale insectEucalyptus speciesYesKaryotypic variation found in association with host use (Cook 2001). Allozymes identify 5 differentiated groups (Cook and Rowell 2007)Yes Each subspecies is genetically distinct and uses a discrete subset of the eucalypt species with no overlap between them (Cook et al. 2001); Females are sessile and stay within their galls initiated in the crawler stage and the males emerge as adults and look for females to mate--all of this occurs on the host plant (Cook et al. 2000)No records foundNo record of host shift. Studies are searches for cryptic diversity.
2Later decided these were two different speciesArchips argyrospilaLepidoptera: Tortricidaefruittree leafrollerbaldcypress and baldcypressYes (Goyer et al. 1995)Significant genetic differences at four loci (Goyer et al. 1995)YesImmigrant inviability: Low survivability of cypress larvae on oak hosts, but further research needed, noted by (Goyer et al. 1995) Did not test oak larvae on cypress. Maybe in CA, Needs further study in LA (Goyer et al. 1995) No. host shift to baldcypress in Louisiana first reported 1983, but no evidence that it recently happened.
1Some genetic differences that are host related (mtDNA). No work has been performed regarding reproductive isolating barriers, and the host shift(s) predates records.Asphondylia borrichiaeDiptera: Cecidomyiidaestem gall midge2 or 3 native plant hosts: sea oxeye daisy, Borrichia frutescens; marsh elder, Iva frutescens; and dune elder, Iva imbricata Yesmitochondrial haplotypes suggest strong genetic differences (Stokes et al. 2012)No records foundN/ANo records foundNo
1No evidence of HAD based on mtDNA sequences from short mtDNA sequence (Stireman III et al. 2005), but with more data there is evidence of massive radiations involving host switching and interactions with fungi.Asteromyia carboniferaDiptera: Cecidomyiidaegall-making midgeGoldenrodYesNo (Stireman III et al. 2005), then Yes (Stireman III et al. 2012)No records foundN/ANo records foundNo
Belonocnema treataeHymenoptera: Cynipidaelive oak gall wasp
1Whiteflies using different plants appear to be genetically different, but they are part of what seems to be a much larger complex of species and biotypes and it is not clear how they are all related to one another.Bemisia tabaciHemiptera: Aleyrodidaewhiteflycassava, okra, and other plants in S.AfricaYesAllozymes and host preference differences (Burban et al. 1992). mtCOI (Esterhuizen et al. 2013)No records foundN/AInitial attempts to make hybrids failed (Burban at al 1992)No. Widespread flies, with no host shift records.
1Genetic differences, but only at local sites.Brevicoryne brassicaeHemiptera: Aphididaecabbage aphid2 Brassica species in Mexico (Chiapas)YesYes, some allozyme frequency differences, but very local, and geographic differences were more pronounced (Ruiz-Montoya et al. 2003)No records foundN/ANo records foundNo
1Genetic differences exist, but populations studied likely part of a larger complex of host forms or host races. Little or no gene flow btw populations studied.Chaetostomella cylindricaDiptera: Tephritidaefruit flyVarious thistle speciesYesRFLPs suggest two host-associated groups (Smith et al. 2009).No records foundN/ANo records foundNo
0Transcriptomes suggest genetic differences, but the experimental setup is such that this differnetiation could reflect environment, not real inherited genetic differences.Chilo suppressalisLepidoptera: Crambidaestriped stem borerrice and the "more delicious" water-oatNoThough "host-associated differentiation" is in the title of their paper, Zhong et al. 2017 show only that RNA transcripts from borers reared on the two hosts are different, and have no control for environmental (host plant) differences. Collections form different hosts were also 300km apart.No records foundN/ANo records foundNo. Insects are described as moving freely between hosts (Zhong et al. 2017)
2bat- and human-associated bedbugs are definitely differentiated. Probably more like sister species at this point. Shared mtCOI may indicate recent introgression but more likely incomplete lineage sorting. Host use does lead to RI because immigrants fair poorly.Cimex lectulariusHemiptera: Cimicidaebed bughumans, batsYesvery different based on 20 microsats (Booth et al. 2015)YesImmigrant inviability (Wawrocka and Bartonicka 2012)No records foundno, and humans have had bedbgs a while (at least since ancient egypt)
1Host-associated genetic differences found among wasps associated with moths on two diff plant hosts. Allozymes and then AFLPs showed differences. Nothing known about mating site or RI for wasps.Copidosoma gelechiaeHymenoptera: Encyritidaeparasitoid waspGnorimoschema moths on two Solidago speciesYes Stireman III et al. 2006, Kolaczan et al. 2009No records foundN/ANo records foundNo
0Differences in fitness on native vs. introduced hosts among larvae collected on the different hosts. No control for developmental plasticity though, so cannot say yet whether this is genetic or plastic. Warrants further investigation, probably with genetic markers.Costelytra zealandicaColeoptera: ScarabaeidaeNew Zealand scarab beetlenative tussock and fescue vs. introduced ryegrass and cloverUnknownDifferences in fitness for beetles with different natal hosts. (Lefort et al. 2014)PossiblyDifferential fitness on alternative hosts (= immigrant inviability). Trait could be plastic (Lefort et al. 2014).No records foundNo
3genetic differences (microsats) between wasps on diff hosts. Several pre and postzygotic barriers related to host use appear to be present, but these also do not seem to be "good species", so RI related to host use is contributing to speciationCotesia congregataHymenoptera: Braconidaeparasitic waspManduca on tobacco vs. Ceratomia on catalpaYes Two distinct distributions based on 7 microsatellite makers (Kester et al. 2015)Yes Differences in courtship of malesin response to female cues. Reduced hybrid viability in one of the hybrid crosses in one host caterpillar type. Did not test male preference (Bredlau and Kester 2015)Most likely, hybrids produced in lab (Bredlau and Kester 2015)No
2Cryptic species within the complex are associated with different host plants. Two biotypes of C. sesamiae are also genetically different, but the authors also suggest they may be distinct species already. Reproductive isolation does appear to exist in the form of mating isolation related possibly to sensory drive. Cotesia flavipes species complexHymenoptera: Braconidaeparasitic wasp of moth larvaevarious families of moths on various host plants, including corn, sugarcane, rice, sorghum.Yes AFLP markers (Joyce et al. 2010)No(Joyce et al. 2013) claims differences in courthsip on plants (because plants transmit different vibrational signals) could potentially lead to behavioral divergence and reproductive isolation.No records foundNo
3These aphids have been previous described as "host races", and that appears to hold up, as they can make hybrids and are isolated primarily by host choice leading to assortative mating, combined with possible reduced hybrid fitness on parental hosts.Cryptomyzus galeopsidisHemiptera: AphididaeaphidTwo different summer hosts, and two different winter Ribes hostsYesallozyme differences (citation?)YesHost preference reduces mating opportunities (Guldemond et al. 1994)Yes, they appear to be able to hybridize (Guldemond et al. 1994)No
0Evidence for host-associated differences is meager. Some evidence of adaptation to different hosts in CA collecctions, but this is not conclusive. Cydia pomonella (= Laspeyresia pomonella)Lepidoptera: TortricidaeCodling mothapples vs. walnut and plumMaybeHost preference for apples vs. walnuts appears to exist, and this preference appears to be partially robust to rearing for several generations in the non-natal fruit host (Phillips and Barnes 1975). Analysis of genetic structure elsewhere (Switzerland), suggests dispersal is extrememly limited. (Chen and Dorn 2010)No records foundN/ANo records foundNo
1genetic structure found, but no specific host-associated reprocutive barriers have been found. Because hosts are sympatric in some sites, there preasumably must be some isolating barriers present, but it is not yet clear what those are.Dalbulus maidisHemiptera:Cicadellidaecorn leafhopperTeosinte and MaizeYes"wild" (teosinte-associated) and "maize" populations are gentically differentiated in some sympatric sites (Davila-Flores 2012, Medina et al 2012)Notests for immigrant inviability and assortative mating both inconsistent, with immigrants even performing apparantly better thatn residents (Ramirez-Romero et al. 2017)Unknown for sure, but no indication that they are not possible (authors working in the system appear to assume that hybrids ARE posisble). Certainly mating occurs between the two groups, but there is no mention of whether those result in progeny (Ramirez-Romero et al. 2017)No, but probably expanded range into maize soon after this crop's domestication
2Gentically different and RI related to host use, but these are already probably different speciesDasineura folliculiDiptera: Cecidomyiidaegall midgetwo species of goldenrod (Solidago rugosa and S. gigantea)YesmtCOI differences - probably cryptic species (Dorchin et al. 2009).YesAssortative mating based on host plant preferences. (Dorchin et al. 2009)Hybrids are viable, but unknown if fitness differs from pure populations (Dorchin et al. 2009)No. Host shift occurred long ago.
1They are quite different (different mtCOI), but they never mate and nothing is known about RI related to host use, so these are best characterized for now as two sister species that use different hosts.Dasineura oxycoccanaDiptera: Cecidomyiidaegall midgeblueberry and cranberryYes mtCOI show that they are probably two species (Cook et al. 2012)unknownthe only work relevant here has been mating tests in the absence of host plants. These show complete sexual isolation (Cook et al. 2011)seems very unlikely, given that they never mate with one another in the lab.No. Most likely the current range results from an introduction of already differentiated midges from elsewhere (Cook et al. 2012)
0Appears to be an example of range / host expansion rather than a host shift.Dendroctonus ponderosae / Dendroctonus jeffreyiColeoptera: Curculionidaemountain pine beetleponderosa pine and logepole pineNodifferences are as much geographic as they are host-related (Sturgeon and Mitton 1986; Langor and Spence 1991; Kelley et al. 2000) allozymes and mtDNA only, no evidence of host fidelity (Langor and Spence 1991)NoWest et al. 2016: all beetles prefer ponderosa pine, regardless of natal host. Adults disperse from host to find mates and oviposit. Females select new tree. Not clear in paper if they consistantly choose the natal host. Also, no evidence of host fidelity, but data is not shown. (Langor and Spence 1991)No records foundNo
4Well-documented shift to a new habitat (and, it turns out, a new fly host). Moved from R. mendax in blueberries to R. pomonella in introduced apples. Genetic differences, allochrony, habitat isolationDiachasma alloeumHymenoptera: Braconidaebraconid waspR. pomonella and R. mendax in apples and blueberries YesForbes et al. 2009YesHabitat isolation and Allochronic isolation. Forbes et al. 2009Yes. Have been mated in lab (Hood et al. 2015)Yes. Apples introduced just a few hundred years ago.
4Wasp populations cluster genetically based on host association. Mating occurs on host's host plant and wasps show preferences for natal host. Both Habitat isolation and allochrony isolate wasps on different hostsDiachasmimorpha melleaHymenoptera: Braconidaebraconid waspR. pomonella and R. mendax in apples and blueberries YesHood et al. 2015YesHabitat isolation and Allochronic isolation. Hood et al. 2015Almost certainly. Wasps from different hosts will mate in the lab, share most microsatellite alleles, and timeline since shift is too short to expect complete isolation.Yes. Apples introduced just a few hundred years ago.
1mtCOI does not show differences, though may not be expected to at this scale. Some genetic differences inferred from local adaptation and host preference that is not due to learning or experience, but only shown at a local scale. At large geographic scales no genetic differences found in preference. Potential for RI, but populations still have high gene flow.Diaeretiella rapaeHymenoptera: Aphidiidaeparasitoid of aphidssupposeedly a broad generalist with >60 hostsYessome evidence of local adaptation to different hosts and host plants, and that these differences are not based on learning or experience (Antolin et al. 2006). Geographic scale analyses show no host-associated pattern (Baer et al. 2004)NoThere are differences in fitness from using different hosts but populations are still able to interbreed and exhibit plasticity in response. Potential for RI, however high gene flow between hosts (Antolin et al. 2006)Yes, wasps of different hosts can interbreedAppears to exhibit serial-specialization in host shifting.(Antolin et al. 2006) Several differences in host preference from old world to new world (Baer et al. 2004)
0No current evidence shows any genetic differences, though these are parthenogentic and the only markers used are AFLPs.Diplolepis rosaeHymenoptera: Cynipidaegall waspThree very closely related species of rose (Rosa)No AFLPs showed no differences (Kohnen et. al 2011)No records foundN/AN/A; asexualNo
2This is really a complex of treehoppers, composed of what are probably already completely or mostly diverged species. Reproductive isolation is definitively linked to host plant use. Though it is hard to imagine a scenario by which these could have diverged completely (or nearly so) before any of the contemporary host-related RI barriers emerged, we nevertheless cannot assume that is not the case.Enchenopa binotataHemiptera: Membracidaetreehoppersvarious treesYes(see Rodríguez and Cocroft 2006; Cocroft et al. 2008)YesPart of mate recognition involves vibrational signals with host plant branches as conduits (Wood 1980; Stearns et al. 2013)possible in lab w/o host plants (Wood and Guttman 1982)No
0No signal of differences from COI. No other studies performed.Epiblema scudderianaLepidoptera: Tortricidaestem galling mothSolidago altissima and S. giganteaNomt COI from two sites where hosts are sympatric revealed no pattern (Stireman III et al. 2005)No records foundN/ANo records foundNo
4Weevils have shifted to a new introduced milfoil (introduced in 1940s, shift may be more recent (1970s?). Weevils on native and intro. milfoil show evidence of hybrid inviability but are nevertheless interfertile. Habitat isolation and immigrant inviability inferred because of larval and adult plant preferences - though not explicitly tested.Euhrychiopsis leconteiColeoptera: Curculionidaemilfoil weevilnative and introduced milfoilYesMicrosatellite data suggests host associated differences. Not strong enough to be called sister species (Roketenetz dissertation 2015) "evidence of outbreeding depression between weevils from different hosts, indicating genetic differentiation" (Sheldon and Jones 2001). YesDecreased hybrid fitness. Females produce more eggs and have higher measured fecundity if mated with a male from the same host plant (Sheldon and Jones 2001). Preferential oviposition in one direction and larval performance differences. adults climb to the top of the plant they emerge from to find a mate (Sheldon and Jones 2001) (= immigrant inviability, habitat isolation) Yes, viable eggs produced in all crosses (Sheldon and Jones 2001)Yes. water/pond management tracked the introduction of the introduced plant species into ponds, so there is a record when weevils were first exposed to the new potential host (Sheldon and Jones 2001). Really good tracking of invasive host plant species in the U.S. European milfoil was first introduced in the 1940s.
3Specifically focused on adaptation to Collinsia plants, several phenotypic diffferences associated with adaptation to different plant hosts. These differences likely result in postzygotic isolation. Populations using different hosts seem to be unable to coexist in sympatry. Euphydryas edithaLepidoptera: NymphalidaeEdith's checkerspotPedicularis semibarbata, Collinsia torreyi YesNo distinctive mtDNA (Radtkey and Singer 1995) or AFLP (Wee 2004) differences, but phenotypic differences demonstrate genetic differences, at least locally (Singer and McBride 2010). These differences very likely not learned (Parmesean et al. 1995)ProbablyDifferences in survivorship, oviposition preference, and several other traits. Differences likely result in extrinsic postzygotic reproductive isolation (Singer and McBride 2010, McBride and Singer 2010). Yes; hybrids present in nature, no evidence of decreased fitness of hybrids (McBride and Singer 2010)No
3Genetically different and evidence of RI barriers related to host use. No evidence that those particular barriers were the first to arise. Eurosta solidaginisDiptera: Tephritidaegoldenrod flySolidago altissima and S. giganteaYeshost associated differences in allozyme frequencies (Waring et al. 1990) & mito data (Brown et al. 1996)YesPreferences for natal plants lead to assortative mating. (Craig et al. 1993)def. possible in lab. Probable in nature (Craig et al. 2001)shift occurred long ago, probably during period of glaciation
1These sawflies appear to be different species already. Host associated genetic differences are present, in the sense that each sawfly species is found on a different host.Euura species complexHymenoptera: Tenthredinidaebud-galling willow sawfliesvarious Salix (willow) speciesYesSeveral different putative species, each on a different primary host (Leppänen et al. 2014)No records foundN/APredicted by not shown (Leppänen et al. 2014)no
1mtDNA and other markers suggest genetic differences quite old. No measures of RI or evidence that reproductive isolation is a consequence of host use. No documentation of (presumably old) host shiftGnorimoschema gallaesolidaginisLepidoptera: Gelechiidaegall mothSolidago altissima and S. giganteaYesDifferentiation at several allozyme loci (Nason et al. 2002); Reciprolcal monophyly in mtDNA sequences (Stireman III et al. 2005)No records foundMoths oviposit on stems and leaves and eggs overwinter. Larvae emerge and result in galls on young plants (Leiby 1922).  Do Larvae make host choices? Moths mate and lay eggs in fall, but no record of where they mate or if they favor particular host species for either mating or oviposition. (Leiby 1922; Miller 1963)"...no convincing evidence of gene flow via hybridization or backcrossing..." (Nason et al. 2002)No. Split between two "races" inferred as being ~300,000 years old (Nason et al. 2002), or even older: ~2 MY (Stireman III et al. 2005). Clearly have adopted a new host, but not clear when during speciation this happened.
0No evidence of host-associated genetic differencesGretchena bolianaLepidoptera: Tortricidaepecan bud mothpecan and water hickoryNoRFLPs and STRUCTURE analysis show no HAD (Dickey and Medina 2010)No records foundN/ANo records foundNo
1These two sister species do have differences in host plant use but there do not appear to be any data linking host plant use to the evolution of RI, now or in the past.Heliconius cydno / Heliconius melpomeneLepidoptera: NymphalidaeCydno Longwing, Postman ButterflyH. melopmene is more or less a specialist on Passiflora oerstedii, H. cydno is more of a generalist (Smiley 1978)YesMerrill et al. 2013No records foundN/AYes, hyrbids are found in nature (though rarely), and there is a low level of gene flow (Bull et al. 2006)No
4Derived host introduced, and introduction documented. Shift recent. Preference and performance differences on the two host plants. Beetles mate on plants so preference likely results in RI. Initiation of Speciation by host shift appears to be most parsimonius explanation.Henosepilachna diekei Coleoptera: Coccinellidaeladybird beetlesMikania micrantha and Leucas lavandulifoliaYesDifferences at ND2 and ITS2 (Matsubayashi et al. 2011),  differences at ND2 gene (Fujiyama et al. 2013)YesPreferences for natal plants lead to assortative mating. (Matsubayashi et al. 2013; Fujiyama et al. 2013). Very strong feeding preferences for natal host plants. Preferences correspond to performance differences in different hosts (Fujiyama et al. 2013)Yes, and they survive and perform as well as parental species (Matsubayashi et al. 2011)Yes. One of the two host plants was introduced to West Java in 1950s. (Whitten et al. 1996)
3Not yet distinct species and isolated by two or more host-related RI barriers.Henosepilachna niponica / H. yasutomiiColeoptera: Coccinellidaethistle-feeding ladybeetleCirsium and CaulophyllumYesInferred from hybrid studies.YesHost fidelity (habitat isolation; Katakura 1997); ecological hybrid inviability (Kuwajima et al. 2010). Random mating in absence of host plants (Katakura and Hosogai 1994)Yes (Kuwajima et al. 2010)No
2Hoppers on Solidago and Gutierrezia are genetically different and reproductive isolation arises from host association because they show host fidelity and mate on hosts. Unknown if they are already completely isolated or not because no hybridization studies. Fairly strong differentiation in AFLP data suggest they have been separated for some time and may not still experience gene flow, but mtDNA suggest possible introgression. (Apple et al. 2011)Hesperotettix viridisOrthoptera: Acrididaesnakeweed grasshopperGutierrezia sarothrae and Solidago mollisYesAFLPs support two clades, each on a different host plant - Gutierrezia and Solidago (Sword et al. 2005). Outlier analysis suggests host-related divergent selection (Apple et al. 2011)YesSome host performance differences and also some host preference differences in choice tests (Traxler and Joern 1999). Mating occures on host plant (Parker 1984), so good evidence for habitat isolation.No records foundNo, but possible that recent increase in abundance of one of the plant hosts (G. sarothrae) - caused by livestock overgrazing - led to a relatively recent host shift. (Sword et al. 2005). MtDNA suggest single glacial refugium with later divergence in host use resulting in race formation (Apple et al. 2011)
0two different forms with different colored heads. These appear to be different species, and do not have host-associated differences. HAD also does not appear to occur within either species.Hyphantria cuneaLepidoptera: ArctiidaeFall webwormblack cherry and black walnutNoJaenike and Selander 1980No records foundN/ANo records foundNo
4adaptive evolution on introducted host plant has affected several traits, including mouthpart length, which is critical for feeding. These are genetically different populaitons, RI barriers are immigrant inviability and host plant mating (habitat isolation).Jadera haemotolomaHemiptera: Rhopalidaesoapberry bugbaloon vine -> goldenrain treeYesBased on cross-rearing and morphological measurements and development comparisons (Carroll et al. 1997)Yes Bugs show host plant preferences and mate on plants (habitat isolation; Carroll and Boyd 1992; Carroll et al. 1997) and beak lengths result in performance tradeoffs (immigrant inviability)Plants and associated insects are allopatric (Carroll et al. 2001), but hybrids seem easy enough to make in the lab (Carroll et al 2001), so if they were to encounter one another it seems that hybrids could occur.Recorded on introduced plants, 1950's-- "flat-podded" goldenrain tree Koelreuteria elegans from southeast Asia(Carroll et al. 1997)
3Re-introduction of an endangered native plant is claimed to have led to a host-plant shift and rapid HAD. While host-related RI does appear to be present, there is a distinct alternative to a recent shift - that being that the butterflies on the endangered plant were present in very small numbers until the reintroduction.Junonia iphita iphitaLepidoptera: NymphalidaeChocolate pansy (butterfly)Hygrophila pogonocalyx and Strobilanthes penstemonoidesYesHybrid survival indicates genetic differences. (Tan et al. 2014)YesHybrids have decreased survival rate (Tan et al. 2014). Larvae survive better on the natal host plant (Tan et al. 2014).Yes, but the survival rate is low (Tan et al. 2014)Host plant restoration started in 1997, which increased sympatric zones and availability of the second host plant. Not clear evidence of abundance of each host plant before restoration or when butterflies started using the new host. (Tan et al. 2014)
0Studies are on adaptation to individual trees within the same species. Just a host genotype / pest genotype interactionKaltenbachiella japonicaHemiptera: Aphididaegalling aphidJapanese elm tree (Ulmus davidiana)NoDoes not evaluate a host shift. Measures host differences between host trees of the same species. (Komatsu and Akimoto 1995)MaybeWingless aphids are only transported via wind, so gene flow is limited between trees (Komatsu and Akimoto 1995), but studies focus on trees of the same species. The sexual generation remains on the natal host plant for mating (Komatsu and Akimoto 1995).No records foundNo
4Bugs have shifted from native Alectryon to C. grandiflorum, introduced ~1920s to Australia. As with North American soapberry bugs, there has been a rapid evolution of beak length, resulting in differnetial fitness on the two hosts. Immigrant inviability is implicit barrier here.Leptocoris tagalicus tagalicus / Leptocoris tagalicus vulgarisHemiptera: RhopalidaeAustralian soapberry bugAlectryon -> Cardiospermum grandiflorumYesNot detected with AFLPs (Andres et al. 2013), but beak length differences have a clear genetic basis (Carroll et al 2005)YesMore efficient at obtaining seeds from natal host, which results in increased / decreased fitness (immigrant inviability). Population feeding on introduced species has longer beak (Carroll et al. 2005)Most likely, crosses done in lab (Carroll et al. 2005)Balloon vine, Cardiospermum grandiflorum was introduced to Australian around 1920's (Carroll 2008).
0Insects collected from three different introduced Brassica hosts at a single site. Produced diff. # of mines on diff hosts in the lab. Not clear that this is really preference or performance, or whether there is any genetic basis. Differences in performance or preference could just refect rearing effects (effects of learning, e.g.). References to this being an example of genetically based habitat preference (Berlocher and Feder 2002, Nosil 2012) are not well justified.Liriomyza brassicaeDiptera: Agromyzidaeleaf-mining flyThree hosts in the family Cruciferae,  Barbarea vulgaris,  Brassica nigra, and Thlaspi arvenseNoNo genetic data collectedUnclear(Tavormina 1982) showed possible preferences by females for natal host plants as oviposition sites, but it is not clear that these are genetic differences or that they result in RI. Mating in this expt was in vials away from host plants.Yes. Mate freely in lab and produce fertile offspring (Tavormina 1982)No
3Inference of low levels of ongoing gene flow, so speciation ongoing but probably incomplete. Host preferences leading to habitat isolation, plus unidirectional immigrant inviability.Lochmaea capreaeColeoptera: Chrysomelidaewillow leaf-beetlebirch and willowYesinferred from inability of willow-origin beetles to survive on birch, but also from crossing expts (Soudi et al. 2016)YesHost preferences leading to habitat isolation, plus unidirectional immigrant inviability (Soudi et al. 2016)Possible in lab, but rates much lower in presence of host plants.No; these are two races on two native host trees.
3Females show host preference and mating on trees (Habitat isolation), and larvae have performance differences (immigrant inviability). Not yet diff species; probably in fairly early stages of divergence. Mitoura gryneusLepidoptera: Lycaenidaejuniper hairstreak butterflyVarious junipersYes Genetic differences based on analyses on mtDNA for COI and COII regions. (Downey and Nice 2013)Yes Show natal host fidelity and mate on hosts, plus show some larval performance differences (Downey and Nice 2011)Almost certainly. They can mate in lab.No
2host associated genetic differences and immigrant inviability. Would be a category 3 except we don't know if there is any possiblity of gene flow at all. Monelliopsis pecanisHemiptera: Aphididaeyellow pecan aphidhickory and pecanYesAFLPs (Dickey and Medina 2010)YesStrong Immigrant inviability (Dickey and Medina 2011)No records foundNo
3Genetically differeniated, barriers are habitat isolation and allochronic isolation. Host shift occurred long ago.Mordellistena convictaColeoptera: Mordellidaestem boring beetleSolidago altissima and S. giganteaYesAllozyme frequency data (Blair et al. 2005)YesAllochronic isolation (Eubanks et al. 2003), Oviposition preferences on natal host (Eubanks et al. 2003). Spend majority of reproductive life in vicinity of natal host (Abrahamson and Weis 1997). Evidence for assortative mating (Eubanks et al. 2003) but where mating occurs not known for sure (Blair et al. 2005)Yes, interbreeding observed in lab (Eubanks et al. 2003)No.
2Immigrant inviability in one direction. Other mate recognition and mate acceptance behaviors that may isolate populations are not explicitly linked to host use but could be result of reinforcement. Record of colonization of tobacco in Greece, but this is not the only place where this aphid lives and so a more global investigation is warranted. Also, while the host-associated genetic differences are conflated by geography, other measures of RI imply that host-related genetic differences are relevant and exist.Myzus persicae nicotianaeHemiptera: Aphididaetobacco aphid/peach-potato aphid tobacco vs. other plantsYesmicrosat data (Margaritopoulos et al. 2007)YesImmigrant inviability in both directions during parthenogenic stage (Nikolakakis et al. 2003). Both mate on peach, one just feeds on tobacco during parthenogenic stageYes (Bass et al. 2013)Some record. Tobacco cultivated in Greece in 1600s, aphid first noticed on tocacco in 1970s.
3genetic differences found between beetles on diff hosts. Host is important in several forms of RI. Neochlamisus bebbianaeColeoptera: Chrysomelidaeleaf beetle maple, oak, birch, hazel, willow, alderYesDifferences in mitochondrial loci (Funk 1998) and genome-level differentiation (Egan et al. 2008)YesOviposition preference, feeding behavior, larval performance, assortative mating were all stronger for natal host (Funk 1998)Yes, host ranges overlap (Funk 1998) but no  documentation of hybrid formation. Hybrids can form in lab (Funk 1998). Mito DNA polyphyletic among/within host associated populations (Funk 1999)No
0No conclusive evidence of genetic differences, just some morphometric differences among leafhoppers found resistant vs. susceptible rice.Nephotettix virescens Hemiptera: Cicadellidaegreen leafhopperDifferent strains of cultivated riceNot clearSome leafhoppers in TAPL-resistant rice have differently-shaped heads. (Ascano II et al. 2010) No records foundN/ANo records foundNo
2A well known pest of rice. A second population was found on a weedy grass in ditches. host associated populations isolated by mating calls, host plant preferences, and poor survival on non-natal hosts. Hybrids, while possible are probably quite unfit in nature as they have intermediate mating calls (borne through plant substrate). Probably already different species, because they are also morphologically distinct.Nilaparvata lugensHemiptera: Delphacideabrown planthopperRice (Oriza) and Leersia hexandraYesInferred from experimental work--strong host and food preferences from the plant which they derive. Further behavioral isolation as well as very little hybridization indicated strong possibility of genetic differences. (Claridge et al. 1985a)YesPlanthoppers show host plant preferences, host plants result in differences in mating call transmission, and planthoppers do not survive well on non-natal plants (Claridge et al. 1985b)Yes, though possibly rare (Claridge et al. 1985a)No. Probably already different species (Latif et al. 2013)
0Beetle does not feed on A. trifida in N.Am, but it does in Japan where both plant and beetle have been introduced. Really a host range expansion story at this point, and not a host shifting story.Ophraella communaColeoptera: Chrysomelidaeragweed leaf beetleAmbrosia artemisiifolia and A. trifida (in Asia)NoAlthough (Futuyma et al. 1993) describes a different host range expansion, no genetic differences were found and in (Fukano et al. 2016) both types of beetle were able to utilize both types of hosts, indicating little or no genetic differencesNoIt seems that while introduced beetles prefer introduced A. Trifolia, they are still able to eat and oviposit on other hosts (Fukano et al. 2016). (Fukano et al. 2016) & (Yamazaki et al. 2000) describe ovipositing on hosts but do not reference mating behavior in particularNo records foundBeetle spread to china in 1996 and then to Japan in 1997-98 around which time host shifting occured (Yamazaki et al. 2000) (Fukano et al. 2016)
1"Ecotypes" living on different vegetation along an elevational gradient. AFLPs show genetic structure related to host plant use (host plants are actually groups of plants, not individual species). Shift probably at last glacial maxima. No reproductive isolation has been measured yet, so for the moment this is a description of host-associated genetic differences.Oreina speciosissimaColeoptera: Chrysomelidaealpine leaf beetleDifferent plant assemblagesYes AFLPS (Borer et al. 2011)No records foundN/ANo records foundNo. Shift inferred to be at last glacial maxima, but this is just presented as a hypothesis based on shallowness of genetic differences.
2Refers to the mugwort and corn populations in Europe. Genetic data suggests little to no gene flow, and they are often givven different species names. Some isolaiton is probably host-related, while other isolation may not be (sexual isolation). There are also two other "borers", and it has been suggested that they hybridize in nature and RI is incomplete. The taxonomy that separates ECB and borers on other plants is based on host plant association.Ostrinia nubilalis / O. scapulatisLepidoptera: CrambidaeEuropean corn borerMaize (corn), other dicots (ABB)YesDifferentiated to the point that they have been called sibling species (Malausa et al. 2007)Yessome evidence of host-associated allochrony (Thomas et al. 2003) and host preference behaviors (Bethenod et al 2005; Malausa et al 2008)Yes, including direct evidence of hybrids in nature (Bourguet et al. 2014)No
0Experimental system; host plant CHCs translate into assortative mating. There is a system with a similar species (P. armoraciae) that shows phenotypic plasticity based upon CHCs from different hosts. Definite potential for reproductive isolation and speciation but no genetic evidencePhaedon cochleariaeColeoptera: Chrysomelidaemustard leaf beetlewatercress and bittercressUnknownNo study has examined the genetic basis of differences in this systemYesMales prefer females with CHC's indicative of the same host plant (Geiselhardt et al. 2012). Both (Gieslhardt et al. 2012) and (Otte et al. 2016) both show intra and interspecies mating based almost entirely on host.Yes. Beetles of a similar species that use different hosts can be mated with if raised on the same host. (Otte et al. 2016)N/A
2populations on pecan and hickory are quite different (AFLPs), and this is robust to geographic structure. Host plant preferences likely to result in habitat isolation for sexual part of life history. Because of rather big genetic difference it is possible that these are completely isolated already, but really no evidence either way, so we can't say for sure that host plants are contributing to speciaiton because they may already be "good species"Phylloxera notabilisHemiptera: Phylloxeridaepecan leaf phylloxeraPecan, hickoryYesAFLPS show strong host associated genetic differences, even when sampled form diverse geographic sites (Dickey and Medina 2012)YesHost plant preference in one direction (hickory-origin bugs prefer hickory) (Dickey and Medina 2012)Unknown. AFLPs show fairly robust differences, and bacterial diversity is quite different (Medina et al. 2011)No
2Populations on different hosts are quite different (AFLPS) and isolated by at least one host-related RI barrier (immigrant inviability). Preliminary work suggests that hybrids may not be possible, but the host shift appears to be at least somewhat recent because no HAD is found in mtDNA. Because we are being conservative, for the moment we cannot say that a shift to a new host has contributed to speciation, because isolation may have been complete or near complete at the time of the shift (though this is unlikely).Phytomyza glabricolaDiptera: Agromyzidaeholly leafminerhollies: Ilex coriacea and I. glabra.YesAFLPs show differences, COI does not (Scheffer and Hawthorne 2007)Yes I. coriacea-origin fly less likely to produce offpring on non-natal host (immigrant inviability) (Hébert et al. 2013). Genome scan demonstrates that some outlier loci are experiencing host-associated selection (Hébert et al. 2016).In a greenhouse study, inter-host mate pairs produced no offspring, so its likely that hybrids are inviable (Hébert et al. 2013). No, but Sheffer and Hawthorne (2007) say the lack of structure in mtCOI data suggest that host shift is "likely very recent"
3genetic differences and some evidence of RI based on host usePlatycampus luridiventrisHymenoptera: TenthredinidaesawflyAlnus glutinosa, Alnus incanaYesallozyme differences in sympatric sites (Herbst and Heitland 1994)YesSmall amount of allochronic isolation (Herbst and Heitland 1994); possible immigrant inviability (Heitland and Pschorn-Walcher 1992)No records foundNo
1Host associated genetic differences of a magnitude that suggest these are different, but closely related species. No studies of RI have been performed.Platygaster variabilisHymenoptera: Platygastridaeparasitoid waspGalling Rhopalomyia on two different Solidago speciesYesUnique mtDNA haplotypes for wasps associated with hosts on different plants (Stireman III et al. 2006)
1These sawflies appear to be different species already. Host associated genetic differences are present, in the sense that each sawfly species is found on a different host.Pontania species complexHymenoptera: Tenthredinidaeleaf-galling willow sawfliesSalix (willow) speciesYesSeveral different putative species, each on a different primary host (Leppänen et al. 2014)No records foundN/APredicted but not shown (Leppänen et al. 2014)no
0No evidence of HAD based on mtDNA sequencesProcecidochares atraDiptera: Tephritidaegall-making fly Solidago altissima and S. Gigantea. Sympatric goldenrod populationsNoThere was no evidence of genetic differentiation based on mtDNA (Stireman III et al. 2005)No records foundN/ANo records foundNo
3Evidence of host associated differences from various different marker types. Isolation arises from temporal isolation (development of insects matches differences in host plant phenology), and probably also immigrant inviability. Speciation appears to be ongoing.Prodoxus decipiensLepidoptera: Prodoxidaebogus yucca mothYucca aloifolia and Y. filamentosaYes?Previous work suggested genetic structure related to host use (Groman and Pellmyr 2000), but newer study suggests this is restricted to (or at least strong on) some barrier islands, and suggests that founder effect may promote HAD (Darwell et al. 2014)YesAllochrony in emergence and differences in ovipositor morphology both linked to host use, so temporal isolation and possible immigrant inviability (Groman and Pellmyr 2000). Tradeoffs in survival may also contribute to immigrant inviability (Althoff et al. 2014)No records foundNo
1Some host associated genetic differences identified on the various hosts, but no RI studies have been performed.Pseudatomoscelis seriatusHemiptera: Miridaecotton fleahoppervarious plant hosts, including cotton Yes and No (Barman et al. 2012)Collections from 5 sites in Texas demonstrate geographic mosaic of HAD. Possibly dependent on regional rainfall and the resulting abundance of each host plantNo records foundN/AUnknown (probably)No
2Shift is to a different life stage of elm trees (seedling vs adults). Host preferences (habitat isolation) and performance (immigrant inviability) both found. mtDNA and field collections suggest hybridization is rare or absent, so we cannot say that host-associated RI has contributed to speciation because other barriers may have completely isolated the two groups before II and HI evolved.Pyrrhalta maculicollis / P. aenescensColeoptera: Chrysomelidaeelm leaf beetlesseedling and adult elm treesYes mtDNA (COI and COII) and nuclear (ITS2) markers show the two groups are deeply divergent, both reciprocally monophyletic  (Nie et al. 2012)YesHost preferences (habitat isolation) and performance (immigrant inviability) both found (Zhang et al. 2014, Zhang et al. 2015)Rare hybridizations cannot be ruled out. Evidence suggests that the beetle species rarely interact and when they do come together on a host plant, that hybrids are unlikely to form.  (Zhang et al. 2015)No but phylogenetic analysis shows P. maculicollis and P. aenescens separated in the Miocene, at around 7.5 Ma (95% CI, 9.5–5.6 Ma) (Nie et al. 2012)
010 microsatellites showed no evidence of host associated genetic differencesRhagoletis cingulataDiptera: Tephritidaecherry fruit flyNative: black cherry (Prunus serotina) Introduced: Sweet (Prunus avium) and tart (Prunus cerasus) cherryNo(Smith et al. 2014) used 10 microsatellites and resolved no evidence of host associated genetic differencesNo records foundN/ANot studied, but likely YesYes, known to have occured over a century ago, though in this case, host expansion may be a more appropriate term
0Microsatellites did not show differences between flies on different cherry hostsRhagoletis indifferensDiptera: Tephritidaewestern cherry fruit flysweet (Prunus avium) and bitter (Prunus cerasus) cherryNoNo evidence for genetic differentiation for host varieties using microsattelite markers (Maxwell et al. 2014)NoEmergence times did not significantly differ between bitter/sweet cherry varieties (Yee et al. 2015) and thus would be able to interbreed.Yes (Maxwell et al. 2014)shift to sweet cherry ~100 years ago (Wilson & Lovett 1913)
4Documented shift of flies from hawthorns to apples, before which there was a single population of flies on hawthorns (the origin of some important variation in diapause timing may have been during last glaciation but that is immaterial to the question, and of course also is a result of host differences [two diff species of Craetagus]). Documented forms of RI include habitat isolation (host preference, non-host avoidance), temporal isolation (allochony), lowered hybrid fitness (hybrids appear to dislike both parental fruit odors). Rhagoletis pomonellaDiptera: Tephritidaeapple maggotHawthorn and introduced applesYesFeder et al. 1988; McPheron et al. 1988; Michel et al. 2010)YesAssortative mating driven by fruit odor preferences and on-fruit mating. (Feder et al. 1993, 1994; Smith 1988; Forbes et al. 2005)Yes (Linn et al. 2004)Yes (Walsh 1867)
3Some (rather preliminary) evidence of host associated genetic differences between cherry- and honeysuckle-associated flies, coupled with differences in host preferences (habitat isolation) and eclosion timing (temporal isolation), suggest that host use contributes to RI.Rhagoletis cerasiDiptera: TephritidaeEuropean cherry fruit flyLonicera (honeysuckle) and prunus (cherry)Maybe29 allozyme loci, no overall signal but Fst for one locus did suggest HAD. (Schwarz et al. 2003)YesEmergence time (diapause length) differences (Boller and Bush 1974), and habitat isolation (Boller et al. 1998)Yes. Crosses in the lab produce a normal number of eggs in most cases.(Boller and Bush 1974)No. Both host plants are indiginous to Europe
1Genetic differences are associated with differences in host plant use - 7 different host plant associated lineages. Possibly / probably these are already different species because of large mtDNA differences. No host-associated RI has been measured, but lineages are partially isolated by sexual isolation. Experiments were conducted on female's natal host, so it is not clear if host plant plays a role in isoaltion here.Rhinusa antirrhiniColeoptera: Curculionidaeweevilvarious plants in genus LinariaYesreciprocal monophyly in COI, less so in ef1alpha (Hernandez-Vera et al. 2010)Yes Hosts show strong preference for weevils raised on the same host plant. (Hernandez-Vera et al. 2010) Hernandez-vera et al. 2010 do not explicitly specify if mating happens on host. Unlikely in nature due to several pre and post mating reproductive barriers in behavior as a result of host preference, but possible in cross copulation experiments (Hernandez-Vera et al. 2010)Earliest divergence 4.26mya (Hernandez-Vera et al. 2010)
1Strong evidence of HAD, but uncertain whether lineages mate on host plant. Didn't find research about RI of R. solidaginis/capitata. Originally thought to be sister species, R. solidaginis and R. capitata are defined as distinct species by Stireman III et al, 2005; each species found on a different species of Goldenrod (R. solidaginis on S. altissima and R. capitata on S. gigantea)Rhopalomyia solidaginis / Rhopalomyia capitataDiptera: Cecidomyiidaegall midgeGoldenrod (Solidago altissima and S. gigantea)Yes Stireman III et al. 2008"Rhopalomyia gall midges exhibit even greater genetic divergence between host plants...Sympatric host-associated populations also exhibited highly significant allozyme differentiation" Stireman III et al. 2005.No records foundN/AHybrids possible in lab. No evidence of hybrids in the field (at least based on mtDNA)No
2Described as an example of locally adapted populations, the nymphs (though not the adults) appear to be dietary specialists. Immigrant inviability seems to be quite strong, and the mtDNA data suggests that these are already pretty strongly divergent.Schistocerca emarginata Orthoptera: Acrididaebird-winged grasshopperPtelea trifoliata and Rubus trivialis (primary nymphal hosts)YesmtDNA sorts grasshoppers into two reciprocally monophyletic clades (Dopman et al. 2002)YesImmigrant inviability: (some) nymphs do poorly on non-natal plants. The color differents between morphs also suggest predation-mediated selection, al la Timema (Sword and Dopman 1999).unknown, though some putative hybrids observed in the field (Dopman et al. 2002)No
1Genetically different, probably to the extent that they should be considered sibling species. Definitiely reproductively isolated, but there does not appear to be a definititve conection between host plant and any RI barrier.Spodoptera frugiperdaLepidoptera: NoctuidaeFall armywormcorn and riceYesPashley 1986UnclearTemporal isolation (time of night) and sexual isolation have both been demonstrated, but the relationship of these barriers to host plant use is tenuous.In lab, Yes, but also some evidence of hybrid sterility (Pashley at al. 1992)No
3This system has several measured RI barriers, all three related to host plant use. The "races" some some differences in alleles at various sites but apparent hybrids may be found in the field (the authors speculate that hybridization helps reinforce differences). Clear case of host use contributing to RI and to speciationTephritis conuraDiptera: Tephritidaetephritid fly - thistlesCirsium oleaceum and C. heterophyllumYesBased on allelic frequencies associated with different plants  (Diegisser et al. 2009; Johannesen et al. 2010)YesHost plant preference (habitat isolation; Diegisser et al. 2006; Eschenbacher 1982), allochrony in sexual development and immigrant inviability (Diegisser et al. 2008)Probably: flies that are very likely to be hybrids have been captured in the field, and are enriched in areas with hybrid plants (Diegisser et al. 2007).No, though a direction for the shift has been inferred (C.h to C. o)
2mtDNA evidence suggests that there are different types that are associated with specific host plants. Authors also suggested that habitat isolation was strong between these groups. Due to the reproductive mode, these types are not able to mate, which suggests that maybe this should be classified as a group 2. However, different types have different reproductive modes and the mechanism seems unclear.Thrips tabaciThysanoptera: Thripidaeonion thripsOnions, Tobacco, Potatoes, Leek, many crop plants that vary by geographyYesBased on COI sequences and ML trees comparing the tobacco group to the leek group in Europe (Brunner et al. 2004). They find two distinct groups on leek and a third group on tobacco.YesVery strong habitat isolation patterns are described in Brunner et al. 2004, but some thrips were found on the wrong hosts based on the haplotype data. Both types can survive on leek, but leek types cannot survive if moved to tobacco (Brunner et al. 2004 - they don't present data for this conclusion). Additional isolation could be a result of different reproductive modes (Toda and Murai 2007). They found more haplotypes than Brenner et al. when sorting mtCOI by reproductive mode.No data found, but unlikely due to reproductive mode.No
3genetic differentiation coupled with several host-related RI barriers. Shift / start of use of both hosts not in natural history record.Timema cristinaePhasmatodea: Timematidaewalking sicksAdenostoma and CeanothusYesNosil et al. 2008, Nosil 2012YesImmigrant inviability and habitat isolation both, plus sexual isolation that has a host-associated component (Nosil et al. 2007)Yes. No reduction in viability for F1 hybrids (Nosil et al. 2007)No
0No evidence of HAD based on mtDNA sequencesTrirhabda convergensColeoptera: Chrysomelidaeleaf chewing beetlesSolidago altissima and S. giganteaNoNo evidence for HAD based on mtDNA sequences  (Stireman III et al. 2005)NoNo host associated differences, very little divergence. Indicates high gene flow (Stireman III et al. 2005)No records foundNo
0No evidence of HAD based on mtDNA sequences, thought there is some evidence for habitat isolation if host preferences can be shown to have a genetic basis.Trirhabda virgataColeoptera: Chrysomelidaeleaf chewing beetlesSolidago altissima and S. giganteaNoNo evidence for HAD based on mtDNA sequences  (Stireman III et al. 2005)PossiblyBeetles show preferences for some hosts, but adults can fly to any plant they choose for mating, although they show preference for optimal hosts (Blatt et al. 1999). Males emerge in mid july, slightly before females and then mate on vegetation shortly after emergence. (Blatt et al. 1999)No records foundNo
4Wasp populations cluster genetically based on host association. Mating occurs on host's host plant and wasps show preferences for natal host. Both Habitat isolation and allochrony isolate wasps on different hostsUtetes canaliculatusHymenoptera: Braconidaebraconid waspR.pomonella in haw and appleYesHood et al. 2015YesHabitat isolation and Allochronic isolation. Hood et al. 2015Almost certainly. Wasps from different hosts will mate in the lab, share most microsatellite alleles, and timeline since shift is too short to expect complete isolation.Yes. Apples introduced just a few hundred years ago.
0Evidence for any host associated differences is just not very strong.Yponomeuta padellusLepidoptera: Yponomeutidaesmall ermine mothHawthorn and PrunusMaybeevidence is weak (Raijmann and Menken 2000)NoNo evidence at this time. All moths appear to prefer and perform better on Prunus (Menken et al. 1992). Lab and field expts demonstrate they mate on many other substrates, including non-host plants (Bakker et al. 2008)No records foundNo
3Very likely incompletely isolated based on genomic work. Host-related barriers currently contribute to isolation.Zeiraphera dinianaLepidoptera: Tortricidaelarch budmothLarch and PineYesEmilianov et al. 1995, Emeilianov et al. 2004YesAllochrony (Day 1984); differences in host plant choice that lead to assortative mating (Emilianov et al. 2001)Yes: cross freely in lab (Emelianov et al. 2001)No

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