Genetic variation in a phylogenetic context: Responses of two specialized leaf beetles (Coleoptera: Chrysomelidae) to host plants of their congeners

This work explores the possibility that constraints on genetic variation guide host shifts and are responsible for the evolutionary conservatism of host affiliation in phytophagous insects. To this end, we used full- and half-sib breeding designs to screen two species of the North American bettle genus Ophraella for genetic variation in larval and adult feeding responses to several host plants of other species of Ophraella. All the plants are in the family Asteraceae. In O. conferta, we observed effectively no feeding response, and hence no genetic variation in response, to three of five test plant species; only those plants related to the species' natural hosts evoked genetically variable responses. In O. artemisiae, adults displayed genetic variation in response to a congener of the natural host, but not to two distantly related plants. However, significant variation among full-sib broods in larval feeding suggests the existence of nonadditive genetic variance in feeding response to all five species of test plants—although survival was very low on most of them. The results suggest that patterns of presence versus apparent absence of detectable genetic variation may be related to the chemical similarity of plants to the insects' natural hosts, but not evidently to the phylogenetic history of host affiliation within the genus. Almost all genetic correlations in responses to host plants were not significantly different from zero; the few significant correlations were positive, and negative correlations that might explain host specificity were not found. Our data do not explain why exclusive shifts to new hosts should occur, but the apparent lack of genetic variation in responses to some plants suggests that the direction of host shifts is genetically constrained.     

GENETIC CONSTRAINTS ON MACROEVOLUTION: THE EVOLUTION OF HOST AFFILIATION IN THE LEAF BEETLE GENUS OPHRAELLA

We hypothesize that the evolution of an ecologically important character, the host associations of specialized phytophagous insects, has been influenced by limitations on genetic variation. Using as a historical framework a phylogenetic reconstruction of the history of host associations in the beetle genus Ophraella (Chrysomelidae), we have employed quantitative-genetic methods to screen four species for genetic variation in larval survival, oviposition (in one species only), and feeding responses to their congeners' host plants, in the Asteraceae. We here report results of studies of one species and evaluate the results from all four. Analysis of half-sib/full-sib families and of progenies of wild females of O. notulata, a specialist on Iva (Ambrosiinae), provided evidence of genetic variation in larval consumption of five of six test plants and in adult consumption of four of six. Larval mortality was complete on five plants; only on Ambrosia, a close relative of the natural host, was there appreciable, and genetically variable, survival. Oviposition on Ambrosia showed marginally significant evidence of genetic variation; a more distantly related plant elicited no oviposition at all. In compiling results from four Ophraella species, reported in this and two other papers, we found no evidence of genetic variation in 18 of 39 tests of feeding responses and 14 of 16 tests of larval survival on congeners' hosts. This result is consistent with the hypothesis that absence or paucity of genetic variation may constrain or at least bias the evolution of host associations. The lower incidence of genetic variation in survival than in feeding behavior may imply, according to recent models, that avoidance is a more common evolutionary response to novel plants than adaptation. The usually great disparity between mean performance on congeners' hosts and the species' natural hosts, and an almost complete lack of evidence for negative genetic correlations, argue against the likelihood that speciation has occurred by sympatric host shift. The presence versus apparent absence of genetic variation in consumption was correlated with the propinquity of relationship between the beetle species tested and the species that normally feeds on the test plant, suggesting that the history of host shifts in Ophraella has been guided in part by restrictions on genetic variation. It was also correlated with the propinquity of relationship between a test plant and the beetle's natural host. The contributions of plant relationships and insect relationships, themselves correlated in part, to the pattern of genetic variation, are not readily distinguishable, but together accord with phylogenetic evidence that these and other phytophagous insects adapt most readily to related plants. In this instance, therefore, the macroevolution of an ecologically important character appears to have been influenced by genetic constraints. We hypothesize that absence of the structural prerequisites for genetic variation in complex characters may affect genetic variation and the trajectory of evolution.     

Phylogeny and host-plant association in the leaf beetle genus Trirhabda LeConte (Coleoptera: Chrysomelidae)

The leaf beetle genus Trirhabda contains 26 described species from the United States and Canada, feeding on host plants from the families Asteraceae and Hydrophyllaceae. In this study, we present a phylogeny for the genus that was reconstructed from mitochondrial COI and 12S rRNA fragments, nuclear ITS2 rRNA, and morphological characters. Both parsimony and mixed-model Bayesian likelihood analyses were performed. Under both methods, the mitochondrial and nuclear partitions support the same backbone phylogeny, as do the combined data. The utility of the molecular data is contrasted with the low phylogenetic signal among morphological characters. The phylogeny was used to trace the evolution of the host-plant association in Trirhabda. The recovered phylogeny shows that although the host-plant association is phylogenetically conservative, Trirhabda experienced one shift to a distantly related host-plant family, 6 shifts between host-plant tribes, and 6 between genera within tribes. The phylogeny reveals that Trirhabda were plesiomorphically adapted to tolerate complex secondary compounds of its host plants and this adaptation is retained in Trirhabda species, as evidenced by multiple shifts from chemically simpler host plants back to the more complex host plants.     

GENETIC CONSTRAINTS AND THE PHYLOGENY OF INSECT-PLANT ASSOCIATIONS: RESPONSES OF OPHRAELLA COMMUNA (COLEOPTERA: CHRYSOMELIDAE) TO HOST PLANTS OF ITS CONGENERS

We ask whether patterns of genetic variation in a phytophagous insect's responses to potential host plants shed light on the phylogenetic history of host association. Ophraella communa feeds chiefly, and in eastern North America exclusively, on Ambrosia (Asteraceae: Ambrosiinae). Using mostly half-sib breeding designs, we screened for genetic variation in feeding responses to and larval survival on its own host and on seven other plants that are hosts (or, on one case, closely related to the host) of other species of Ophraella. We found evidence for genetic variation in feeding responses to five of the seven test plants, other than the natural host. We found no evidence of genetic variation in feeding responses to two plant species, nor in capacity for larval survival on six. These results imply constraints on the availability of genetic variation; however, little evidence for constraints in the form of negative genetic correlations was found. These results are interpreted in the context of a provisional phylogeny of, and a history of host shifts within, the genus. Ophraella communa does not present evidence of genetic variation in its ability to feed and/or survive on Solidago, even though it is probably descended from a lineage that fed on Solidago or related plants, possibly as recently as 1.9 million years ago. Genetic variation in performance on this plant may have been lost. Based on evidence for genetic variation and on mean performance, by far the greatest potentiality for adaptation to a congener's host was evinced in responses to Iva frutescens, which not only is related and chemically similar to Ambrosia, but also is the host of a closely related species of Ophraella that may have been derived from an Ambrosia-associated ancestor. Genetic variation in O. communa's capacity to feed and/or survive on its congeners' hosts is less evident for plants that do not represent historically realized host shifts (with one exception) than for those that may (but see Note Added in Proof). The results offer some support for the hypothesis that the evolution of host shifts has been guided in part by constrained genetic variation.     

Histories of host shifts and cospeciation among free‐living parasitoids of Rhagoletis flies

Host shifts by specialist insects can lead to reproductive isolation between insect populations that use different hosts, promoting diversification. When both a phytophagous insect and its ancestrally associated parasitoid shift to the same novel host plant, they may cospeciate. However, because adult parasitoids are free living, they can also colonize novel host insects and diversify independent of their ancestral host insect. Although shifts of parasitoids to new insect hosts have been documented in ecological time, the long‐term importance of such shifts to parasitoid diversity has not been evaluated. We used a genus of flies with a history of speciation via host shifting (Rhagoletis [Diptera: Tephritidae]) and three associated hymenopteran parasitoid genera (Diachasma, Coptera and Utetes) to examine cophylogenetic relationships between parasitoids and their host insects. We inferred phylogenies of Rhagoletis, Diachasma, Coptera and Utetes and used distance‐based cophylogenetic methods (ParaFit and PACo) to assess congruence between fly and parasitoid trees. We used an event‐based method with a free‐living parasitoid cost model to reconstruct cophylogenetic histories of each parasitoid genus and Rhagoletis. We found that the current species diversity and host–parasitoid associations between the Rhagoletis flies and parasitoids are the primary result of ancient cospeciation events. Parasitoid shifts to ancestrally unrelated hosts primarily occur near the branch tips, suggesting that host shifts contribute to recent parasitoid species diversity but that these lineages may not persist over longer time periods. Our analyses also stress the importance of biologically informed cost models when investigating the coevolutionary histories of hosts and free‐living parasitoids.     

HOST-PLANT SWITCHES AND THE EVOLUTION OF CHEMICAL DEFENSE AND LIFE HISTORY IN THE LEAF BEETLE GENUS OREINA

Insect-plant interactions have played a prominent role in investigating phylogenetic constraints in the evolution of ecological traits. The patterns of host association among specialized insects have often been described as highly conservative, yet not all specialized herbivorous insect lineages display the same degree of fidelity to their host plants. In this paper, we present an estimate of the evolutionary history of the leaf beetle genus Oreina. This genus displays an amazing flexibility in several aspects of its ecology and life history: (1) host plant switches in Oreina occurred between plant families or distantly related tribes within families and thereby to more distantly related plants than in several model systems that have contributed to the idea of parallel cladogenesis; (2) all species of the genus are chemically defended, but within the genus a transition between autogenous production of defensive toxins and sequestration of secondary plant compounds has occurred; and (3) reproductive strategies in the genus range from oviparity to viviparity including all intermediates that could allow the gradual evolution of viviparity. Cladistic analysis of 18 allozyme loci found two most parsimonious trees that differ only in the branching of one species. According to this phylogeny estimate, Oreina species were originally associated with Asteraceae, with an inclusion of Apiaceae in the diet of one oligophagous species and an independent switch to Apiaceae in a derived clade. The original mode of defense appears to be the autogenous production of cardenolides as previously postulated; the additional sequestration of pyrrolizidine alkaloids could have either originated at the base of the genus or have arisen three times independently in all species that switched to plants containing these compounds. Viviparity apparently evolved twice in the genus, once without matrotrophy, through a retention of the eggs inside the female's oviducts, and once in combination with matrotrophy. We hypothesize that the combination of autogenous defense and a life history that involves mobile externally feeding larvae allowed these beetles to switch host plants more readily than has been reported for highly conservative systems.     

A molecular phylogeny of Basidiophora reveals several apparently host-specific lineages on Astereae

The genus Basidiophora has long been thought to contain only two species, Basidiophora entospora and Basidiophora kellermanii, the latter of which was transferred to a newly described monotypic genus, Benua, at the end of the twentieth century, leaving Basidiophora monotypic, despite its vast host range, including a member of the Eupatoriae and several genera in the subfamily Asteroideae of the Asteraceae. Using historic herbarium specimens, we demonstrate that while Benua kellermanii is genetically highly homogenous, at least seven distinct phylogenetic lineages exist within Basidiophora, which, based on sequence divergence, most likely constitute hitherto overlooked cryptic species. As the specimens from Symphyotrichum novae-angliae formed a well-supported clade with little variation, we consider Peronospora simplex described on this host as an independent species, which is transferred to the genus Basidiophora in this study. The phylogeny of the pathogens corresponds well to the phylogeny of the respective hosts, which is unusual in downy mildews and might hint at clade-limited colonisation and subsequent radiation to closely related hosts of Astereae or even suggest a co-evolution scenario. Our findings provide further evidence that species with assumed broad host ranges should be thoroughly evaluated with respect to their phylogenetic relationships, especially in biotrophic genera with only limited morphological diversity. In some cases, host specificity of genetically divergent lineages might be the only phenotypic trait remaining for species delimitation. Future detailed morphological comparisons are needed to reveal if the seemingly cryptic species of Basidiophora can be distinguished based on subtle morphological characteristics.     

Molecular systematics reveals the origins of subsociality in tortoise beetles (Coleoptera,Chrysomelidae, Cassidinae)

Subsocial behaviour is known to occur in at least 19 insect orders and 17 families of Coleoptera. Within the leaf beetle family, Chrysomelidae, extended maternal care is reported in only 2 of 15 subfamilies: Cassidinae and Chrysomelinae. Although the emergence of subsociality in insects has received much attention, extensive analyses on the evolution of this behaviour based on phylogenetic approaches are missing. Subsociality is recorded in 33 species of tortoise beetles belonging to the tribes Mesomphaliini and Eugenysini. A molecular phylogenetic reconstruction of these tribes and the remaining five Neotropical tribes of cassidine tortoise beetles was used to investigate the evolution of maternal care and to elucidate the phylogenetic relationships among Neotropical cassidine tribes. A phylogeny was constructed using 90 species and three loci from both mitochondrial and nuclear genes (COI, CAD and 28S). Bayesian inference and maximum likelihood analyses based on a concatenated dataset recovered two independent origins, with no evidence of reversal to solitary behaviour. One origin comprises three Mesomphaliini genera tightly associated with Convolvulaceae, and the other consists of the genus Eugenysa Chevrolat (Eugenysini), a small clade embedded within a group feeding exclusively on Asteraceae. A previous hypothesis suggesting dual origins on different host plants was confirmed, whereas other hypotheses based on a phylogenetic reconstruction of Cassidinae could not be sustained. Our analysis also revealed that the tribe Mesomphaliini is a monophyletic taxon if Eugenysini is included, and for this reason, we re-establish synonymy of both tribes. We also provide nine new records of subsociality for tortoise beetles species.     

Host range of Secusio extensa (Lepidoptera: Arctiidae), and potential for biological control of Senecio madagascariensis (Asteraceae)

Secusio extensa (Lepidoptera: Arctiidae) was evaluated as a potential biological control agent for Madagascar fireweed, Senecio madagascariensis (Asteraceae), which has invaded over 400 000 acres of rangeland in the Hawaiian Islands and is toxic to cattle and horses. The moth was introduced from southeastern Madagascar into containment facilities in Hawaii, and host specificity tests were conducted on 71 endemic and naturalized species (52 genera) in 12 tribes of Asteraceae and 17 species of non‐Asteraceae including six native shrubs and trees considered key components of Hawaiian ecosystems. No‐choice feeding tests indicated that plant species of the tribe Senecioneae were suitable hosts with first instars completing development to adult stage on S. madagascariensis (78.3%), Delairea odorata (66.1%), Senecio vulgaris (57.1%), Crassocephalum crepidioides (41.2%), and at significantly lower rates on Emilia fosbergii (1.8%) and Erechtites hieracifolia (1.3%). A low rate of complete larval development also was observed on sunflower, Helianthus annuus (11.6%), in the tribe Heliantheae. However, sunflower was rejected as a potential host in larval‐feeding and adult oviposition choice tests involving the primary host S. madagascariensis as control. Although larvae died as first instars on most test species, incomplete development and low levels of feeding were observed on nine species in the tribes Heliantheae, Cardueae and Lactuceae. Larvae did not feed on any non‐Asteraceae tested, including species with similar pyrrolizidene alkaloid chemistry, crops, and six ecologically prominent native species. Because all species of Senecioneae are non‐native and weedy in Hawaii, these results indicate that S. extensa is sufficiently host‐specific for introduction for biological control. High levels of feeding damage observed on potted plants indicate that S. extensa can severely impact the target fireweed as well as D. odorata, a noxious weed in native Hawaiian forests.     

IS SPECIALIZATION A DEAD END? THE PHYLOGENY OF HOST USE IN DENDROCTONUS BARK BEETLES (SCOLYTIDAE)

Ecological explanations for the prevalence of resource specialists are abundant, whereas phylogenetic evidence on their origins is scarce. In this paper, we provide a molecular phylogenetic study of the 19 specialist or generalist species in the bark beetle genus Dendroctonus, which collectively attack species in four different genera in the conifer family Pinaceae. Given substantial variation in diet breadth, we asked two general questions concerning the evolution of resource use in this group. How conservative is the evolution of host use in these insects? Does specialization tend to be derived (i.e., a “dead end”)? To answer these questions, we estimated the phylogeny of Dendroctonus using mitochondrial DNA sequences and mapped transitions in resource use on the resulting phylogeny estimate. The evolution of affiliations with Pinus and Picea hosts in Dendroctonus was conservative among beetle species (PTP test; P < 0.012), but there was no significant correspondence between the phylogeny of these beetles and the phylogeny among their Pinaceae hosts (among genera, P = 0.28; among Pinus species, P = 0.82). Degree of specialization, as measured in the proportion of hosts used, was bimodally distributed with “generalist” species utilizing < 60% of the congeneric hosts within their range and six specialist species utilizing < 40% of the available hosts. Among the generalists, we found a strong correlation between the number of hosts encountered and the number of hosts utilized (R = 0.97, P < 0.0001), whereas there was no significant correlation among the specialists (R = 0.27, P = 0.59). The evolution of specialization in Dendroctonus proved highly labile—specialists arose from generalists at least six separate times (without reversal) all in derived positions, and closer examination of some specialists revealed instances where they appear to have lost particular host species from their diet. However, evidence from the ecological literature also suggests that several Dendroctonus generalists may have increased their range of host genera within the Pinaceae.     

Evolution of host-parasite relationships of Golovinomyces (Ascomycete: Erysiphaceae) inferred from nuclear rDNA sequences

To understand the evolution of host-parasite relationships in the genus Golovinomyces (Ascomycete: Erysiphaceae), which are obligate parasitic fungi of plants, we investigated the phylogenetic relationships of the genus based on 60 internal transcribed spacer (ITS) and 41 28S rDNA sequences. Five major groups, each represented by isolates from a single tribe of the Asteraceae, were identified in the taxa analyzed in this study. Host plants of four groups were strictly restricted to the Asteraceae. The fifth group, the Lactuceae group, is a large group composed of isolates collected from the tribe Lactuceae of the Asteraceae and all other plant families, which suggests a close affinity between Golovinomyces and the Asteraceae in the early stages of their evolution. Tree topology comparisons between the asteraceous hosts and their parasites suggest that Golovinomyces diverged along with the phylogeny of host tribes Carsueae, Astereae, Heliantheae, and Lactuceae of the Asteraceae. However, a conflict of branching order between the tribe Anthemideae and their parasites suggests that host-jumping has occurred in the tribe Anthemideae. Consequently, we suggest that there are two different phases in the evolutionary history of the host-parasite relationships of Golovinomyces. One phase is divergence in accord with the phylogeny of their hosts, which occurred within the Asteraceae. The another phase is host-jumping, which occurred from the Asteraceae to other families and within the Asteraceae.     

A test of adaptive divergence in a newly discovered host association of the soapberry bug Jadera haematoloma on Mexican buckeye,Ungnadia speciosa

Host races represent an important step in the speciation process of phytophagous insects as they reflect the maintenance of genetically divergent host-associated populations in the face of appreciable gene flow. The red-shouldered soapberry bug, Jadera haematoloma (Herrich-Schäffer) (Hemiptera: Rhopalidae), is an oligophagous seed predator with a history of host race evolution on plant associations in the (soapberry) family Sapindaceae. Soapberry bugs are a model group for understanding rapid ecological adaptation to their hosts, and hence good candidates for investigating evolutionary divergence in host associations over short timescales. Here, we describe the recent discovery of Mexican buckeye, Ungnadia speciosa Endl., as a host of J. haematoloma in a region of the Chihuahuan desert including west Texas and southeastern New Mexico, USA. This host differs from J. haematoloma’s previously recorded hosts in the Sapindaceae in seed chemistry, ecology, and phylogeny. The tendency toward rapid, host-associated adaptations by populations of J. haematoloma and the unique biology of the newly discovered Ungnadia host create the opportunity for potential host race formation, as it overlaps geographically with two previously recorded host plants in this region – the native western soapberry tree, Sapindus saponaria var. drummondii (Hook & Arn.), and the non-native goldenrain tree, Koelreuteria paniculata Laxm. We explore the possibility of host race formation on Ungnadia-associated insects by testing for host-associated differentiation in morphology and feeding behaviors. We find evidence of differentiation in the length of the mouth parts, which is an ecologically relevant feeding trait between host plant species with larger or smaller seed capsules. This divergence is maintained in the face of potential gene flow by reproductive isolation in the form of habitat isolation, which we detect in host preference trials. Together, our results demonstrate that soapberry bugs associated with this newly discovered host exhibit morphological and behavioral traits consistent with host race formation, but additional work is required to confirm its state along the speciation continuum.     

Palaeocene origin of the Neotropical lineage of cleptoparasitic bees Ericrocidini‐Rhathymini (Hymenoptera,Apidae)

Cleptoparasitic bees abandoned pollen‐collecting for their offspring and lay their eggs in other bees' provisioned nests. Also known as cuckoo bees, they belong to several lineages, but are especially diverse in Apinae. We focused on a lineage of apine cleptoparasitic bees, the clade Ericrocidini + Rhathymini, which attack nests of oil‐collecting bees. We sequenced five genes for 20 species in all genera of this clade plus a large outgroup to reconstruct the phylogeny and estimate divergence times. We confirmed the monophyly of the clade Ericrocidini + Rhathymini and its position inside the ericrocidine line together with the tribes Protepeolini, Isepeolini, Osirini and Coelioxoidini. Our results corroborated the current taxonomic classification. Ericrocis is sister to all Ericrocidini and the position of Acanthopus and the most diverse genus Mesoplia were inconclusive. Ericrocidini + Rhathymini diverged from other apine cleptoparasitic lineages 74 Ma in the Cretaceous and from each other in the Palaeocene at 61 Ma. Considering the robust molecular evidence of their sister relationships, the striking differences in the morphology of first‐instar larvae of the two groups may represent adaptations to the nesting biology of their hosts. As other cleptoparasites in the ericrocidine line, Ericrocidini and Rhathymini possess larvae which are adapted to kill the immature host and to feed on floral oil provided by the host female. The evolution of host specialization in the line Ericrocidini + Rhathymini retroceded to the Eocene when they differentiated synchronously with their hosts, Centris and Epicharis .     

Divergence before the host shift? Prezygotic reproductive isolation among three varieties of a specialist fly on a single host plant

1. Although divergence via host‐plant shifting is a common theme in the speciation of some phytophagous insects, it is not clear whether host shifts are typically initiators of speciation or if they instead contribute to divergence events already in progress. While host shifts appear to be generally associated with speciation events for flies in the genus Strauzia, three sympatric varieties of the sunflower fly [Strauzia longipennis (Wiedemann)] co‐occur on the same host plant in the Midwestern United States and may have evolved reproductive barriers without a host shift. 2. The strength of two prezygotic reproductive barriers was compared among the three S. longipennis varieties: one barrier that is often associated with divergent ecological selection (allochronic isolation), and another that is more likely to be independent of ecological selection (pre‐copulatory sexual isolation). The presence and relative strength of each barrier between fly varieties were evaluated using microsatellites, no choice mating experiments, studies of allochronic isolation, and field collection data. 3. Evidence for both allochronic isolation and pre‐copulatory sexual isolation was detected between the three varieties of S. longipennis. The measure of isolation calculated for each barrier between the three varieties was lower than measures calculated between different species of Strauzia found on different hosts, suggesting that subsequent host shifts may increase the degree of reproductive isolation. For Strauzia and other specialist insects, some reproductive isolation may evolve prior to, and indeed may facilitate, host shifts.     

Phylogeny of the parasitic wasp subfamily Euphorinae (Braconidae) and evolution of its host preferences

The braconid subfamily Euphorinae is a large, cosmopolitan group of endoparasitoid wasps. The majority of species attack adult hosts, a strategy that is rare among parasitic wasps, but there are also many species that attack nymphs and larval stages. Euphorine hosts may belong to a variety of insect orders (Coleoptera, Hemiptera, Hymenoptera, Neuroptera, Psocoptera, Orthoptera and Lepidoptera) although most euphorine tribes are confined to Coleoptera. Here we investigate the phylogenetic relationships of the Euphorinae based on molecular data (3 kb of nucleotide data from four markers: 18S, 28S, CAD and COI) and propose a higher‐level classification based upon the resulting phylogeny. We also infer the evolution of host associations and discuss the diversification of the Euphorinae. Results from both Bayesian inference and maximum‐likelihood analysis show that the subfamily, as previously circumscribed, is paraphyletic. We propose that the subfamily be expanded to include the tribes Meteorini and Planitorini (Mannokeraia + Planitorus), so that it corresponds to a clade that is strongly supported as monophyletic in our analyses. Based on our results, a revised higher classification of the Euphorinae is proposed, in which 52 extant genera and 14 tribes are recognized. We reinstate the genus Microctonus belonging to the tribe Perilitini, and synonymize Ussuraridelus with Holdawayella, Sinuatophorus with Eucosmophorus. Furthermore, we propose the following tribal rearrangements: Spathicopis and Stenothremma are transferred to Perilitini; Tuberidelus, Eucosmophorus and Plynops to Cosmophorini; Ecclitura to Dinocampini; Chrysopophthorus, Holdawayella and Wesmaelia to Helorimorphini; Proclithroporus and Heia to Townesilitini. The monotypic tribe Cryptoxilonini is synonymized with Cosmophorini. The genera Pygostolus and Litostolus are placed in a separate tribe, Pygostolini, previously recognized as a subtribe among the Centistini. Parsimony‐based ancestral state reconstructions suggest that the ancestor of Euphorinae was a parasitoid of lepidopteran larvae, and that a host shift to larval Coleoptera occurred only in one clade of the Meteorini, some members of which secondarily shifted back to larval lepidopteran hosts. In the remainder of the subfamily, there was an initial shift from larval to adult coleopterans, followed by subsequent shifts to adults or larvae of Hemiptera, Hymenoptera, Neuroptera, Orthoptera and Psocoptera.     

An aphid lineage maintains a bark‐feeding niche while switching to and diversifying on conifers

Lachnine aphids are unusual among phytophagous insects because they feed on both leafy and woody parts of both angiosperm and conifer hosts. Despite being piercing‐sucking phloem‐feeders, these aphids are most speciose on woody parts of coniferous hosts. To evaluate the significance of this unusual biology on their evolution, we reconstructed the ancestral host and feeding site of the lachnine aphids and estimated important host shifts during their evolution. We sampled 78 species representing 14 of the 18 genera of Lachninae from Asia and North America. We performed parsimony, Bayesian and likelihood phylogenetic analyses of combined mitochondrial Cox1, Cox2, CytB and nuclear EF1a1 DNA sequences. We dated the resulting phylogram's important nodes using Bayesian methods and multiple fossil and secondary calibrations. Finally, we used parsimony and Bayesian ancestral state reconstruction to evaluate ancestral feeding ecology. Our results suggest the lachnine common ancestor fed on a woody part of an angiosperm host in the mid‐Cretaceous. A shift to conifer hosts in the Late Cretaceous is correlated with a subsequent increased diversification in the Palaeogene, but a switch to leafy host tissues did not engender a similar burst of diversification. Extant lachnine lineages exhibit the full range of historical association with their hosts: some appeared before, some concomitant with and some after the appearance of their hosts. We conclude our study by placing all the lachnine genera in five tribes.     

Phylogenetic analyses of DNA and allozyme data suggest that Gonioctena leaf beetles (Coleoptera; Chrysomelidae) experienced convergent evolution in their history of host-plant family shifts

A phylogenetic analysis of the genus Gonioctena (Coleoptera, Chrysomelidae) based on allozyme data (17 loci) and mitochondrial DNA sequence data (three gene fragments, 1,391 sites) was performed to study the evolutionary history of host-plant shifts among these leaf beetles. This chrysomelid genus is characteristically associated with a high number of different plant families. The diverse molecular data gathered in this study are to a large extent congruent, and the analyses provide a well-supported phylogenetic hypothesis to address questions about the evolution of host-plant shifts in the genus Gonioctena. The most-parsimonious reconstruction of the ancestral host-plant associations, based on the estimated phylogeny, suggests that the Fabaceae was the ancestral host-plant family of the genus. Although most of the host-plant shifts (between different host species) in Gonioctena have occurred within the same plant family or within the same plant genus, at least eight shifts have occurred between hosts belonging to distantly related and chemically dissimilar plant families. In these cases, host shifts may have been simply directed toward plant species available in the environment. Yet, given that two Gonioctena lineages have independently colonized the same three new plant families (Salicaceae, Betulaceae, Rosaceae), including four of the same new genera (Salix, Alnus, Prunus, Sorbus), some constraints are likely to have limited the different possibilities of interfamilial host-plant shifts.     

Unexpected distribution patterns of Carduiceps feather lice (Phthiraptera: Ischnocera: Philopteridae) on sandpipers (Aves: Charadriiformes: Scolopacidae)

The louse genus Carduiceps Clay & Meinertzhagen, 1939 is widely distributed on sandpipers and stints (Calidrinae). The current taxonomy includes three species on the Calidrinae (Carduiceps meinertzhageni, Carduiceps scalaris, Carduiceps zonarius) and four species on noncalidrine hosts. We estimated a phylogeny of four of the seven species of Carduiceps (the three mentioned above and Carduiceps fulvofasciatus) from 13 of the 29 hosts based on three mitochondrial loci, and evaluated the relative importance of flyway differentiation (same host species has different lice along different flyways) and flyway homogenization (different host species have the same lice along the same flyway). We found no evidence for either process. Instead, the present, morphology‐based, taxonomy of the genus corresponds exactly to the gene‐based phylogeny, with all four included species monophyletic. Carduiceps zonarius is found both to inhabit a wider range of hosts than wing lice of the genus Lunaceps occurring on the same group of birds, and to occur on Calidris sandpipers of all sizes, both of which are unexpected for a body louse. The previously proposed family Esthiopteridae is found to be monophyletic with good support. The concatenated dataset suggests that the pigeon louse genus Columbicola may be closely related to the auk and diver louse genus Craspedonirmus. These two genera share some morphological characters with Carduiceps, but no support was obtained for grouping these three genera together. Based on mitochondrial data alone, the relationships among genera within this proposed family cannot be properly assessed, but some previously suggested relationships within this proposed family are confirmed.     

Molecular phylogenetic and divergence time estimation analyses of the sawfly subfamily Selandriinae (Hymenoptera: Tenthredinidae)

Selandriinae, a subfamily of family Tenthredinidae (Hymenoptera: Symphyta), comprises multiple tribes, each of which has a relationship with specific plant group. The host specificity of the Selandriinae taxa provides a good model to examine the coevolution between hosts and insects. However, few phylogenetic studies for the Selandriinae obscure the evolutionary scenario with their host‐plants. The present study is a molecular phylogenetic analysis of 19 selandriine species based on mitochondrial genes (12S: 461 sites, 16S: 262sites and COI: 495 sites) and nuclear genes (18S: 773 sites and 28S: 495 sites). The results suggested three of six studied tribes are genetically isolated. Moreover, estimation of the time of molecular divergence showed that the Selandriinae clearly diverged at the same time as their host‐plants (monocots and ferns). These results suggested that the Selandriinae species might have codiversified with their hosts.     

You stay,but I Hop: Host shifting near and far co‐dominated the evolution of Enchenopa treehoppers

The importance and prevalence of phylogenetic tracking between hosts and dependent organisms caused by co‐evolution and shifting between closely related host species have been debated for decades. Most studies of phylogenetic tracking among phytophagous insects and their host plants have been limited to insects feeding on a narrow range of host species. However, narrow host ranges can confound phylogenetic tracking (phylogenetic tracking hypothesis) with host shifting between hosts of intermediate relationship (intermediate hypothesis). Here, we investigated the evolutionary history of the Enchenopa binotata complex of treehoppers. Each species in this complex has high host fidelity, but the entire complex uses hosts across eight plant orders. The phylogenies of E. binotata were reconstructed to evaluate whether (1) tracking host phylogeny; or (2) shifting between intermediately related host plants better explains the evolutionary history of E. binotata. Our results suggest that E. binotata primarily shifted between both distant and intermediate host plants regardless of host phylogeny and less frequently tracked the phylogeny of their hosts. These findings indicate that phytophagous insects with high host fidelity, such as E. binotata, are capable of adaptation not only to closely related host plants but also to novel hosts, likely with diverse phenology and defense mechanisms.