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Many plant-sap-feeding insects have maintained a single, obligate, nutritional symbiont over the long history of their lineage. This senior symbiont may be joined by one or more junior symbionts that compensate for gaps in function incurred through genome-degradative forces. Adelgids are sap-sucking insects that feed solely on conifer trees and follow complex life cycles in which the diet fluctuates in nutrient levels. Adelgids are unusual in that both senior and junior symbionts appear to have been replaced repeatedly over their evolutionary history. Genomes can provide clues to understanding symbiont replacements, but only the dual symbionts of hemlock adelgids have been examined thus far. Here, we sequence and compare genomes of four additional dual-symbiont pairs in adelgids. We show that these symbionts are nutritional partners originating from diverse bacterial lineages and exhibiting wide variation in general genome characteristics. Although dual symbionts cooperate to produce nutrients, the balance of contributions varies widely across pairs, and total genome contents reflect a range of ages and degrees of degradation. Most symbionts appear to be in transitional states of genome reduction. Our findings support a hypothesis of periodic symbiont turnover driven by fluctuating selection for nutritional provisioning related to gains and losses of complex life cycles in their hosts.

Hamamelistes and Hormaphis aphids of the tribe Hormaphidini are distributed disjunctly in eastern North America and Eurasia. Host-alternating species have life cycles encompassing generations in a gall on witch-hazel (Hamamelis spp.) and generations on leaves of birch (Betula spp.). In Hamamelistes, generations on witch-hazel induce globular pouch galls on flower or leaf buds. Herbarium specimens of a related Hamamelidaceae genus, Fothergilla, contain large galls in place of the seed head. We obtained a fresh sample of these elongate pouch galls collected from F. milleri in Alabama, USA. The galls were formed in place of fruiting structures and contained numerous aphids. Examination of morphology and the cytochrome oxidase subunit I “barcode” DNA sequence confirmed that the aphids are an undescribed species of Hamamelistes. Here, we describe the new species, Hamamelistes blackmani Dederich & von Dohlen sp. n., from the morphology of foundresses, immatures, and winged forms in the gall. The life cycle is presumed monoecious. In addition, we review the evidence for including other genera in Hormaphidini and recommend that this tribe be restricted to Hamamelistes and Hormaphis.

Blanchardaphis was erected for two Argentinian species of aphids very similar to Uroleucon, but distinguished by several characters. Here, we examined morphology and DNA sequences of Blanchardaphis specimens from Argentina and Chile. We further conducted a phylogenetic analysis to determine the relationship of Blanchardaphis to Uroleucon. We found minor morphological and genetic differences between Blanchardaphis samples based on geography, which appear to be population-level variation. On the basis of current evidence, we conclude that B. poikila (Ortego, Nieto Nafría & Mier Durante, 1997) is synonymous with B. capitophoroides (Blanchard, 1942), and that Blanchardaphis Ortego, Nieto Nafría & Mier Durante, 1998 is synonymous with Lambersius Olive, 1965 (subgenus of Uroleucon) sensu Nieto Nafría et al. 2007 or alternatively with the subgenus Uroleucon.

Ageniella is the second-most diverse spider wasp genus in Ageniellini (Pepsinae). The Ageniella (Ageniella) accepta species-group is found from Canada to Panama and is composed of three Nearctic species: A. accepta (Cresson), A. blaisdelli (Fox), and A. conflicta Banks. Within this group, species-level identification is difficult, because diagnostic characters are questionable, and subjective for both males and females. Furthermore, sexes of each species are not reliably associated. Herein, we investigate sex associations and the validity of described species within the A. accepta species-group based on three molecular markers (cytochrome oxidase I, wingless, long-wavelength rhodopsin) by using maximum likelihood and Bayesian phylogenetic analyses, and species-delimitation approaches. Additionally, we mapped 12 morphological traits onto the molecular phylogeny to discuss evolution of diagnostic characters. We concluded that the three species of the A. accepta species-group are actually a single, wide-ranging species with strong geographical signal. Moreover, our results suggest introgression at the mitochondrial level.

Rhus gall aphids (Hemiptera: Aphididae: Eriosomatinae) stimulate the formation of galls on their primary host plants (sumacs: Rhus spp., Anacardiaceae). The shapes of galls are often used as an extended phenotype to identify the aphid species and subspecies. We collected four Rhus galls with conspicuously different shapes formed by Kaburagia rhusicola aphids, whose sequences of the complete mitochondrial genomes (mitogenomes) were obtained by high-throughput sequencing. Each mitogenome was assembled into a circular molecule containing 13 protein-coding genes, two rRNAs, 22 tRNAs and one control region. All the protein-coding genes had a typical ATN initiation codon and TAA termination codon except for cox1 and nad4, which had a single T as stop codon. All the tRNAs could be folded as a typical clover-leaf secondary structure, except for trnS1 lacking a dihydrouridine (DHU) arm. The relative synonymous codon usage and ratio of nonsynonymous to synonymous substitution rates showed that the four K. rhusicola samples were highly similar to the subspecies K. r. ovogallis. The phylogenetic analyses grouped these samples with K. r. ovogallis in a clade sister to K. r. rhusicola. All these molecular analyses demonstrated that our current samples represented one subspecies of Kaburagia rhusicola, i.e., K. r. ovogallis, and the gall shape was variable even at the subspecies level in Kaburagia gall aphids.

Bacterial endosymbionts of sap-sucking insects provide their host with a number of beneficial qualities, including the supply of nutrition, defense against parasitoids, and protection from heat stress. Damage to these bacterial associates can therefore have a negative impact on the fitness of their insect host. We evaluated observational and experimental factors regarding the nonnative hemlock woolly adelgid (Adelges tsugae Annand) (Hemiptera: Adelgidae) to help understand the roles of its three recently identified symbionts, including under heat stress conditions. The prevalence of A. tsugae's facultative symbiont (Serratia symbiotica) was examined at different spatial scales to determine how variable infection rates are for this symbiont. There was no significant difference found in infection rates between adelgids on a tree, within a plot, or within a state. However, significantly more adelgids in Georgia (95%) had S. symbiotica compared to those in New York (68%). Microsatellite genotyping of the adelgids found that this difference was most likely not the result of a second introduction of A. tsugae into eastern North America. Comparison of S. symbiotica proportions between first and fourth instars showed that symbiont absence did not affect the ability of A. tsugae to survive aestivation. Evaluations of symbiont densities within each adelgid found that when S. symbiotica was absent, the density of obligate symbionts was significantly higher. Exposure to heat stress (32.5 °C) was not consistently correlated with changes in symbiont densities over a 4-d period. Overall, we have shown that symbiont prevalence and densities vary within the broad population of A. tsugae in eastern North America, with potentially significant effects upon the ecology of this important pest.

Uroleucon Mordvilko is the largest genus in the Macrosiphini (Hemiptera, Aphididae) and most of its species live on species of Asteraceae. Uroleucon nahuelhuapense Nieto Nafría & von Dohlen sp. n. is described from apterous viviparous females collected on Adesmia boronioides (Fabaceae) in a locality of Neuquén province (Argentina). The morphological characters and the sequence of the tRNAleu-COII mitochondrial locus support the inclusion of the new species in the genus Uroleucon. Apterous viviparous females of Uroleucon adesmiae Mier Durante & Ortego collected in two Argentinean localities have also been studied and ranges of several quantitative features have been modified. The identification key for the Uroleucon species known in South America by Nieto Nafría et al. (2007) has been modified to include the new species.

Nutritional bacterial symbionts enhance the diets of sap-feeding insects with amino acids and vitamins missing from their diets. In many lineages, an ancestral senior symbiont is joined by a younger junior symbiont. To date, an emergent pattern is that senior symbionts supply a majority of amino acids, and junior symbionts supply a minority. Similar to other hemipterans, adelgids harbor obligate symbionts, but have higher diversity of bacterial associates, suggesting a history of symbiont turnover. The metabolic roles of dual symbionts in adelgids and their contributions to the consortium are largely unexplored. Here, we investigate the symbionts of Adelges tsugae, the hemlock woolly adelgid (HWA), an invasive species introduced from Japan to the eastern United States, where it kills hemlock trees. The response of hemlocks to HWA feeding has aspects of a defensive reaction against pathogens, and some have speculated that symbionts may be involved. We sequenced the genomes of “Ca. Annandia adelgestsuga” and “Ca. Pseudomonas adelgestsugas” symbionts to detail their metabolic capabilities, infer ages of relationship, and search for effectors of plant defenses. We also tested the relationship of “Ca. Annandia” to symbionts of other insects. We find that both symbionts provide nutrients, but in more balanced proportions than dual symbionts of other hemipterans. The lesser contributions of the senior “Ca. Annandia” support our hypothesis for symbiont replacements in adelgids. Phylogenomic results were ambiguous regarding the position of “Ca. Annandia”. We found no obvious effectors of plant defenses related to insect virulence, but hypothetical proteins in symbionts are unknown players.

Ageniella Banks is the second most diverse genus in the tribe Ageniellini (Pompilidae: Pepsinae) with about 200 valid names. Ageniella is known to be paraphyletic; yet, no revision has been made. Lack of a taxonomic catalogue and of identification keys has further delayed taxonomic studies. Additionally, many of the currently valid names should be treated as synonyms. This present study is the first attempt to organize the species of Ageniella, focusing on the species occurring in Brazil. A total of six subgenera and 40 species of Ageniella occur in Brazil. Of these, 25 species are endemic to Brazil. The new synonyms are proposed for (valid names are first): Alasagenia Banks, 1944 =Lissagenia Banks, 1946, syn. nov.; Ageniella (Alasagenia) erichsoni Banks, 1944 =Priophanes major Banks, 1945, syn. nov.; Ageniella (Ameragenia) zeteki (Banks, 1925) =Priophanes marcida Banks, 1946, syn. nov.; Ageniella (Ameragenia) agitata (Smith, 1873), comb. nov. =Salius (Priocnemis) setaceicornis Fox, 1897, syn. nov.; Ageniella (Ameragenia) sanguinolenta (Smith, 1864) =Agenia ruficeps Smith, 1864, syn. nov.; =Ageniella alternata Banks, 1946, syn. nov.; Ageniella (Priophanes) dolorosa (Banks, 1946), comb. nov. =Priophanes plagosa Banks, 1946, syn. nov.; Ageniella (Ameragenia) fabricii (Banks, 1944) =Ameragenia notabilis Banks, 1946, syn. nov. A new combination is proposed for: Ageniella (Alasagenia) cursor (Smith, 1873), comb. nov. (from Agenia Schiødte); Ageniella (Ameragenia) clypeata (Fox, 1897), comb. nov. (from Salius Fabricius), Ageniella (Ameragenia) rutila (Fox, 1897), comb. nov. (from Salius), Ageniella (Priophanes) tegularis (Fox, 1897), comb. nov. (from Salius), Ageniella (Priophanes) rufitarsis (Fox, 1897), comb. nov. (from Salius), Ageniella (Ameragenia) citricornis (Fox, 1897), comb. nov. (from Salius), Ageniella (Ameragenia) serrula (Fox, 1897), comb. nov. (from Salius), Ageniella (Priophanes) cingulata (Fox, 1897), comb. nov. (from Agenia). A new name Ageniella (Ameragenia) banksii Waichert, nom. nov. is proposed for Ameragenia festina Banks, 1946, secondary homonym of Ageniella festina Banks, 1917, and Ageniella (Priophanes) otiosa is reinstate, stat. resurr.

Spider wasps (Hymenoptera: Pompilidae) constitute a monophyletic family supported by numerous morphological and behavioral traits. The subfamilial and tribal classifications, however, have a history of conflicting and confusing designations and nomenclature. Here, we reconstruct a molecular phylogeny of Pompilidae from Bayesian and maximum-likelihood analyses of four nuclear molecular markers (elongation factor– 1 α F2 copy, long–wavelength rhodopsin, RNA polymerase II, and 28S ribosomal RNA). A Bayesian divergence-time estimation was performed using four calibration points. An ancestral-area reconstruction was performed with a Bayesian binary Markov chain Monte Carlo method. New relationships are recovered, and new subfamilial delimitations are proposed and discussed based on the phylogeny. The origin of Pompilidae was ca. 43.3 Ma, probably in the Nearctic region. Most of the extant subfamilies originated during the late Eocene through Oligocene, and their current distributions are the product of various dispersal events that occurred over the course of ~40 Ma. This is the first phylogenetic reconstruction of Pompilidae from molecular characters, with broad geographic and taxonomic sampling. The following subfamilies and relationships are recognized: Ctenocerinae + (Ceropalinae + Notocyphinae) + Pompilinae + Pepsinae. We revalidate Notocyphinae, which contains only Notocyphus, and define a new tribe in Pompilinae: Sericopompilini. Priochilini is reinstated. Sericopompilini contains Sericopompilus as the sole representative; Priochilini contains Priochilus and Balboana. Epipompilus and Chirodamus are now classified as Pepsinae.

For decades, biologists have debated why many parasites have obligate multihost life cycles. Here, we use comparative phylogenetic analyses of aphids to evaluate the roles of ecological optimization and historical constraint in the evolution of life cycle complexity. If life cycle complexity is adaptive, it should be evolutionarily labile, that is, change in response to selection. We provide evidence that this is true in some aphids (aphidines), but not others (nonaphidines)-groups that differ in the intensity of their relationships with primary hosts. Next, we test specific mechanisms by which life cycle complexity could be adaptive or a constraint. We find that among aphidines there is a strong association between complex life cycles and polyphagy but only a weak correlation between life cycle complexity and reproductive mode. In contrast, among nonaphidines the relationship between life cycle complexity and host breadth is weak but the association between complex life cycles and sexual reproduction is strong. Thus, although the adaptiveness of life cycle complexity appears to be lineage specific, across aphids, life cycle evolution appears to be tightly linked with the evolution of other important natural history traits.

Aim Our aim was to determine the age and area of origin of the genera of the Aporini tribe of spider wasps by studying its historical biogeography. We also tested the fit of several hypotheses concerning the processes underlying the widespread distribution of this group. Location The Holarctic and Neotropics. Methods A phylogeny of 44 Aporini taxa was produced through Bayesian inference using four nuclear molecular markers (elongation factor-1 α F2 copy, long-wavelength rhodopsin, wingless and the D2–D3 regions of the 28S ribosomal RNA). A lognormal relaxed molecular clock, calibrated with ages from three fossils, was used to estimate lineage divergence times. Biogeographical processes were studied using three methods: statistical dispersal–vicariance analysis (S-DIVA), dispersal–extinction cladogenesis (DEC) analysis and Bayesian binary Markov chain Monte Carlo (BBM) analysis. Results Our data suggest an origin for the most recent common ancestor of extant Aporini in the Nearctic region in the early Miocene, 22.6 Ma, with a confidence interval (CI) of 17.40–28.83 Ma. All genera originated in the Miocene, four in the Nearctic region. A constrained DEC analysis, where only dispersal to adjacent regions was allowed, produced the highest likelihood and was mostly congruent with the BBM results. Main conclusions Dispersal from the Nearctic region to the Palaearctic region probably occurred across the Bering land bridge in the early Miocene, 15–18 Ma (CI = 11.14, 23.52), while three dispersal events to South America from Mesoamerica took place independently. These dispersals to South America occurred after 18 Ma through the Isthmus of Panama or across the Panama seaway. Three independent over-water dispersal events to the Antilles occurred from Mesoamerica and the Nearctic for two Aporini genera. The patterns inferred within the biogeographical history of Aporini agree with several scenarios proposed for other unrelated taxa.

Bacterial endosymbionts of sap-sucking insects provide their host with a number of beneficial qualities, including the supply of nutrition, defense against parasitoids, and protection from heat stress. Damage to these bacterial associates can therefore have a negative impact on the fitness of their insect host. We evaluated observational and experimental factors regarding the nonnative hemlock woolly adelgid (Adelges tsugae Annand) (Hemiptera: Adelgidae) to help understand the roles of its three recently identified symbionts, including under heat stress conditions. The prevalence of A. tsugae's facultative symbiont (Serratia symbiotica) was examined at different spatial scales to determine how variable infection rates are for this symbiont. There was no significant difference found in infection rates between adelgids on a tree, within a plot, or within a state. However, significantly more adelgids in Georgia (95%) had S. symbiotica compared to those in New York (68%). Microsatellite genotyping of the adelgids found that this difference was most likely not the result of a second introduction of A. tsugae into eastern North America. Comparison of S. symbiotica proportions between first and fourth instars showed that symbiont absence did not affect the ability of A. tsugae to survive aestivation. Evaluations of symbiont densities within each adelgid found that when S. symbiotica was absent, the density of obligate symbionts was significantly higher. Exposure to heat stress (32.5 °C) was not consistently correlated with changes in symbiont densities over a 4-d period. Overall, we have shown that symbiont prevalence and densities vary within the broad population of A. tsugae in eastern North America, with potentially significant effects upon the ecology of this important pest.

Accurate fossil identification has become increasingly relevant with the widespread use of phylogenetic divergence time estimation methods, which rely on fossil data to determine clade hard-minimum ages. Here we revise, diagnose and illustrate known spider wasp (Hymenoptera: Pompilidae) fossil species and place them within the latest Pompilidae phylogenetic hypothesis. Ceropalites infelix Cockerell, from the Florissant Fossil Beds (Priabonian), is no longer recognized as Pompilidae, but as Aulacidae. Agenioideus saxigenus (Cockerell) comb. nov., Deuteragenia wettweri (Statz) comb. nov., Caputelus scudderi (Cockerell, 1906) comb. nov., Pepsinites avitula (Cockerell, 1941) comb. nov., Pepsinites contentus (Theobald, 1937) comb. nov., Pepsinites florissantensis (Cockerell, 1906) comb. nov., Pepsinites laminarum (Rohwer, 1909) comb. nov., Pepsinites scelerosus (Meunier, 1919) comb. nov., Pepsinites cockerellae (Rohwer, 1909) comb. nov., Pompilinites coquandi (Theobald, 1937) comb. nov., Pompilinites depressus (Statz, 1936) comb. nov., Pompilites incertus (Theobald, 1937) comb. nov., Pompilites induratus (Heer, 1849) comb. nov., Pompilites fasciatus (Theobald, 1937) comb. nov., and Pompilites senex comb. nov. are new combinations. Twenty-three fossil species of spider wasps are now recognized in 13 genera. Four new genera are proposed: Caputelus Waichert & Pitts gen. nov., Pompilites Rodriguez gen. nov., Pompilinites Rodriguez & Waichert gen. nov., and Pepsinites Rodriguez & Waichert gen. nov., of which the three latter are collective-group names for fossils with taxonomic uncertainty. One species of fossil spider wasp is described: Deuteragenia catalunyia Rodriguez, Waichert & Pitts sp. nov., from the Bellver deposits in Catalonia, Spain. Five of the 23 known species can be used to determine hard-minimum age for calibrations of genera stem-groups (Agenioideus, Anoplius, Cryptocheilus, Deuteragenia, Priocnemis). The fossil belonging to the stem-group of the tribe Ageniellini (Chubutholites) is not recommended for calibration because of the high uncertainty in its age and taxonomy. The remaining taxa can be assigned to the lineage comprising Pompilinae + Pepsinae (12 species) or crown-group Pompilidae (four species).

Sap-sucking insects typically engage in obligate relationships with symbiotic bacteria that play nutritional roles in synthesizing nutrients unavailable or in scarce supply from the plant-sap diets of their hosts. Adelgids are sap-sucking insects with complex life cycles that involve alternation between conifer tree species. While all adelgid species feed on spruce during the sexual phase of their life cycle, each adelgid species belongs to a major lineage that feeds on a distinct genus of conifers as their alternate host. Previous work on adelgid symbionts had discovered pairs of symbionts within each host species, and unusual diversity across the insect family, but left several open questions regarding the status of bacterial associates. Here, we explored the consistency of symbionts within and across adelgid lineages, and sought evidence for facultative vs. obligate symbiont status. Representative species were surveyed for symbionts using 16S ribosomal DNA gene sequencing, confirming that different symbiont pairs were consistently present within each major adelgid lineage. Several approaches were used to establish whether symbionts exhibited characteristics of long-term, obligate mutualists. Patterns of symbiont presence across adelgid species and diversification with host insects suggested obligate relationships. Fluorescent in situ hybridization and electron microscopy localized symbionts to bacteriocyte cells within the bacteriome of each species (with one previously known exception), and detection of symbionts in eggs indicated their vertical transmission. Common characteristics of long-term obligate symbionts, such as nucleotide compositional bias and pleomorphic symbiont cell shape were also observed. Superimposing microbial symbionts on the adelgid phylogeny revealed a dynamic pattern of symbiont gains and losses over a relatively short period of time compared to other symbionts associated with sap-sucking insects, with each adelgid species possessing an older, “senior” symbiont and a younger “junior” symbiont. A hypothesis relating adelgid life cycles to relaxed constraints on symbionts is proposed, with the degradation of senior symbionts and repeated acquisition of more junior symbionts creating opportunities for repeated colonization of new alternate-conifer hosts by adelgids.

Priocnemella Banks is a small Neotropical genus within Ageniellini with remarkable morphological variation between species. Some species are small and variable in colour, whereas others are large with black integument and yellow wings. We conducted a phylogenetic analysis of Priocnemella based on the mitochondrial gene cytochrome oxidase I and the nuclear marker long-wavelength rhodopsin. Our results indicated that Priocnemella is a paraphyletic genus. Based on molecular phylogenetic analyses, we discuss the taxonomic validity of Priocnemella, its implications and a new circumscription of genera of Ageniellini. Eragenia Banks is revalidated (stat. rev.) and applied to 16 species, eight of which are newly described: Eragenia bella Waichert & Pitts sp.n., E. carinata Waichert & Pitts sp.n., E. dentata Waichert & Pitts sp.n., E. oliva Waichert & Pitts sp.n., E. pseudomicans Waichert & Pitts sp.n., E. setosa Waichert & Pitts sp.n., E. rotunda Waichert & Pitts sp.n., E. villosa Waichert & Pitts sp.n., E. abdominalis (Smith), E. amabilis (Taschenberg), E. aureicornis (Smith), E. coerulipes (Smith), E. congrua (Fox), E. isolata (Banks), E. micans (Fabricius), and E. tabascoensis (Cameron). Priocnemella fairchildi (Banks), P. insignis (Banks), P. eurytheme Banks, P. hexagona (Fox) and P. hexagona omissa Banks maintain their generic status. Phanochilus Banks is considered a junior synonym of Priocnemella and the following species are newly placed within Priocnemella: P. fuscomarginata (Fox), P. gloriosa (Smith), P. nobilitata (Smith) and P. ornata (Banks). The following nomenclatural changes are proposed: Priocnemella rufothorax (Banks) is synonymized under Eragenia micans (Fabricius) (syn. n.); Priocnemella delila (Banks), Priocnemella bequaerti (Banks) and Priocnemella infelix (Banks) are junior synonyms of Eragenia aureicornis (Smith) (syn.n.) (comb.n). New combinations are proposed for Eragenia aureicornis (Smith) comb.n., Eragenia abdominalis (Smith) comb.n. and Eragenia coerulipes (Smith) comb.n. from Agenia; and Eragenia congrua (Fox) comb.n. from Salius. A neotype is designated for E. coerulipes and for E. tabascoensis. Divergence dates between species of Eragenia, ancestral areas and pattern of dispersal that shaped the current geographic distribution are discussed. The genus is about 9.8 Ma old, originating in Mesoamerica during the Miocene. Finally, newly described male genitalic characters are discussed and illustrated, and illustrated keys for males and females species of Eragenia are provided. This work has been registered in ZooBank, http://zoobank.org/urn:lsid:zoobank.org:pub:8308D00F-E25E-4019-A94B-DCAEDED67D4C.

The taxonomy of the Antillean genus Drepanaporus Bradley (Pompilidae) is problematic because of sexual dimorphism and nearly uniform morphology of males across species. Species limits are not well understood, and sexes are not properly associated in all species. In this study, we reassessed morphology, and collected novel molecular data for the purpose of determining species boundaries and establishing sex-associations for all species. Two genes, cytochrome c oxidase (COI) and long-wavelength rhodopsin (LWRh) were amplified for 20 specimens of Drepanaporus, from both females and males. Using LWRh (including both introns and exons) and COI sequences, the relationships of Drepanaporus samples were reconstructed. Sequences obtained for COI showed unusually high divergences and putative introgression, and thus were not used for taxonomic decisions. Taxonomic changes were made based on the LWRh phylogenetic results. A new species of Drepanaporus— Drepanaporus bachata sp. nov—is described herein based on both molecular and morphological characters for both male and female specimens, and a key is provided for the genus for the three species now recognized. We also discuss the usefulness of mitochondrial and nuclear markers in Pompilidae for species delimitations and sex-associations.

Melaphidina aphids (Rhus-gall aphids; Eriosomatinae: Fordini) comprise five genera from eastern Asia and one monotypic genus from eastern North America. Melaphidina are unique in feeding on plant species of Rhus subgenus Rhus (Anacardiaceae), on which they form galls during the summer. The phylogenetic relationships among some species of Melaphidina aphids remain controversial. In this study, we sought to resolve the backbone phylogeny of Melaphidina aphids by sampling 15 accessions representing all six genera, all species, and all subspecies except Meitanaphis microgallis using 20 gene regions: five nuclear genes as well as 13 protein-coding genes and two rRNA genes of the mitochondrial genome. Phylogenetic analyses included Bayesian and maximum likelihood methods. Independent analyses of nuclear and mitochondrial genes returned congruent topologies, and analyses of all gene regions combined showed well-supported relationships among Melaphidina species. In particular, these were: (1) Nurudea (excluding N. ibofushi) is sister to a clade composed of the five remaining genera; (2) the monotypic North American genus Melaphis is sister to a clade comprising the four remaining genera; and (3) (Schlechtendalia + N. ibofushi) is sister to the clade (Floraphis (Meitanaphis + Kaburagia). Our results support the transfer of Meitanaphis flavogallis to Kaburagia as an additional subspecies or species, and the recognition of Floraphis as a distinct genus. This study provides important molecular resources for subsequent evolutionary studies using more nuclear genes on the Melaphidina aphids and their close allies.

Intercontinental biotic disjunctions have been documented and analyzed in numerous Holarctic taxa. Patterns previously synthesized for animals compared to plants suggest that the timing of animal disjunctions are mostly Early Tertiary and were generated by migration and vicariance events occurring in the North Atlantic, while plant disjunctions are mostly Mid-Late Tertiary and imply migration and vicariance over Beringia. Melaphidina aphids (Hemiptera: Aphididae: Fordini) exhibit host-alternating life cycles comprising an obligate seasonal shift between Rhus subgenus Rhus species (Anacardiaceae) and mosses (Bryophyta). Similar to their Rhus hosts, melaphidines are distributed disjunctly between Eastern Asia and Eastern North America. We examined evolutionary relationships within Melaphidina to determine the position of the North American lineage, date its divergence from Asian relatives, and compare these results to a previous historical biogeographic study of Rhus. We sampled nine species and three subspecies representing all six genera of Melaphidina. Data included sequences of mitochondrial cytochrome c oxidase subunits I and II+leucine tRNA, cytochrome b, and nuclear elongation factor 1α genes. Phylogenetic analyses (Bayesian, maximum-likelihood, parsimony) of the combined data (3282 bp) supported the monophyly of all genera except Nurudea and Schlechtendalia, due to the position of N. ibofushi. While the exact position of the North American Melaphis was not well resolved, there was high support for a derived position within Asian taxa. The divergence of Melaphis from Asian relatives centered on the Eocene-Oligocene boundary (~33-35Ma), which coincides with closure of Beringian Land Bridge I. This also corresponded to the Asian-North American disjunction previously estimated for subgenus Rhus spp. We suggest the late-Eocene Bering Land Bridge as the most likely migration route for Melaphis ancestors, as was also hypothesized for North American Rhus ancestors. Results for the Melaphidina disjunction depart from the modal pattern in animal lineages, and present a case where insect and host-plant taxa apparently responded similarly to Tertiary climate change.

SummaryThe smallest reported bacterial genome belongs to Tremblaya princeps, a symbiont of Planococcus citri mealybugs (PCIT). Tremblaya PCIT not only has a 139 kb genome, but possesses its own bacterial endosymbiont, Moranella endobia. Genome and transcriptome sequencing, including genome sequencing from a Tremblaya lineage lacking intracellular bacteria, reveals that the extreme genomic degeneracy of Tremblaya PCIT likely resulted from acquiring Moranella as an endosymbiont. In addition, at least 22 expressed horizontally transferred genes from multiple diverse bacteria to the mealybug genome likely complement missing symbiont genes. However, none of these horizontally transferred genes are from Tremblaya, showing that genome reduction in this symbiont has not been enabled by gene transfer to the host nucleus. Our results thus indicate that the functioning of this three-way symbiosis is dependent on genes from at least six lineages of organisms and reveal a path to intimate endosymbiosis distinct from that followed by organelles.

Summary Knowledge of intraspecific variation in symbioses may aid in understanding the ecology of widespread insects in different parts of their range. We investigated bacterial symbionts of Adelges tsugae, a pest of hemlocks in eastern North America introduced from Asia. Amplification, cloning, and sequencing of bacterial 16S rDNA, in situ hybridizations, and electron microscopy revealed that A. tsugae harbours up to five bacterial phylotypes, according to population. Three Gammaproteobacteria species are maternally transmitted. The first, designated ‘Ca. Pseudomonas adelgestsugas’ resides in the haemocoel, and was detected in all populations except Taiwan. The second phylotype, ‘Ca. Serratia symbiotica’, resides in bacteriocytes of populations on Tsuga sieboldii in Japan and in E. North America. The third phylotype, designated ‘Ca. Annandia adelgestsuga’, clustered within a lineage of several insect endosymbionts that included Buchnera aphidicola. It was detected in bacteriocytes in all populations, and in salivary glands of first instars. Two Betaproteobacteria phylotypes were detected in some Japanese T. sieboldii and eastern North America populations, and were observed only in salivary glands with no evidence of maternal transmission. Our results support the ideas that symbiont gain and loss has been volatile in adelgids, and that symbionts may help to trace the source of invasive species.

Aphis intybi Koch is recorded for the first time in North and South America. Measurements for the identification of this species in comparison with Aphis craccivora Koch are given. Aphis cytisorum Hartig is recorded for the third time in Argentina. Data on morphological variation, geographical distribution, and host plants of these species in Argentina are provided. Their morphological identification is supported by comparison of DNA sequences of the mitochondrial cytochrome oxidase subunit 1 (DNA barcode) and subunit 2. Aphis intybi Koch se cita por primera vez tanto en América del Sur como del Norte. Se aportan características métricas para la identificación de la especie en comparación con Aphis craccivora Koch. Aphis cytisorum Hartig se cita por tercera vez en la Argentina. Se aportan datos sobre la variación morfológica, así como sobre la distribución geográfica y las plantas hospedadoras en Argentina de esas especies. Las identificaciones morfológicas han sido corroboradas mediante comparaciones de las secuencias de la citocromo oxidasa I (DNA barcode) y de la citocromo oxidasa II del DNA mitocondrial. EEA Mendoza Fil: Mier Durante, Milagros Pilar. Universidad de León. Departamento de Biodiversidad y Gestión Ambiental (área de Zoología); España Fil: Foottit, Robert. Agriculture and Agri-Food Canada. Canadian National Collection of Insects. Invertebrate Biodiversity; Canadá Fil: Dohlen, Carol D. Von. Utah State University. Department of Biology; Estados Unidos Fil: Ortego, Jaime. Instituto Nacional de Tecnología Agropecuaria (INTA). Estación Experimental Agropecuaria Mendoza; Argentina

The libellulid dragonfly genus Sympetrum has been recognized since 1833, but lacks any morphological synapomorphies to unite the taxon. Previous researchers have disagreed over which species belong in Sympetrum, bringing the monophyly of the genus into question. We use DNA sequence data from 6 genetic loci (16S, tRNA-valine, 12S, elongation factor 1 alpha, cytochrome oxidase subunit I, and the second internal transcribed spacer region) and 25 morphological characters (mainly genitalic) to test the monophyly of Sympetrum with Bayesian inference and maximum likelihood analyses. Under Bayesian inference, all Sympetrum species included in this study form a clade, which also contains the Hawaiian monotypic genus Nesogonia, often considered a close relative of Sympetrum. Phylogenetic analyses also reveal at least six strongly supported clades (treated as species groups) within Sympetrum, but relationships between these species groups remain unresolved or unsupported. Although the relationships between Sympetrum species groups remain unresolved, several species groups include taxa from multiple biogeographic regions/continents, and the species group sister to the rest of Sympetrum contains migratory species from the New World and Africa. This pattern suggests a complex biogeographic history in Sympetrum shaped by vicariance and dispersal. Preliminary estimates of the divergence dates of Sympetrum species groups outline a rapid radiation of the groups approximately 32-38 million years ago, possibly influenced by cooling and drying climates of the late Eocene and early Oligocene.

This study examines the validity of the ten species and eight subspecies composing the Dasymutilla bioculata species group. Four lines of evidence are examined: morphological data derived from both sexes; behavioural data derived from the study of mating pairs; geographic distribution; and molecular data derived from the internal transcribed spacers 1 and 2 of the nuclear ribosomal RNA cistron (ITS1 and ITS2). Morphological studies reveal that none of the taxa in question can be consistently diagnosed by any synapomorphies or unique combinations of characters. Mating studies reveal that males of single nominal taxa are attracted to females of multiple nominal taxa, and that females of single nominal taxa attract multiple males. None of the nominal taxa are geographically isolated from the others. Genetic distances between these taxa are significantly lower than those seen in interspecific comparisons of other Dasymutilla species. Based on this evidence, we infer that the taxa in question share a recent common ancestor, and cannot be adequately differentiated using any of the available data sources. Therefore, employing the phylogenetic species concept, Dasymutilla bimaculata Manley & Pitts, Dasymutilla chiron chiron (Blake), Dasymutilla chiron ursula (Cresson), Dasymutilla creusa creusa (Cresson), Dasymutilla creusa bellona (Cresson), Dasymutilla lepeletierii (Fox), Dasymutilla medea (Cresson), Dasymutilla melanippe melanippe Mickel, Dasymutilla melanippe conformis Mickel, Dasymutilla praegrandis praegrandis Mickel, Dasymutilla praegrandis russata Mickel, Dasymutilla pyrrhus (Fox) and Dasymutilla sulcatulla Mickel must be considered junior synonyms of Dasymutilla bioculata (Cresson). We also discuss the identification of this species, as well as subspecific relationships and species-group implications.

UMR BGPI équipe 6; UMR CBGP; Aphids are intimately linked with their host plants that constitute their only food resource and habitat, and thus impose considerable selective pressure on their evolution. It is therefore commonly assumed that host plants have greatly influenced the diversification of aphids. Here, we review what is known about the role of host plant association on aphid speciation by examining both macroevolutionary and population-level studies. Phylogenetic studies conducted at different taxonomic levels show that, as in many phytophagous insect groups, the radiation of angiosperms has probably favoured the major Tertiary diversification of aphids. These studies also highlight many aphid lineages constrained to sets of related host plants, suggesting strong evolutionary commitment in aphids' host plant choice, but they fail to document cospeciation events between aphid and host lineages. Instead, phylogenies of several aphid genera reveal that divergence events are often accompanied by host shifts, and suggest, without constituting a formal demonstration, that aphid speciation could be a consequence of adaptation to new hosts. Experimental and field studies below the species level support reproductive isolation between host races as partly due to divergent selection by their host plants. Selected traits are mainly feeding performances and life cycle adaptations to plant phenology. Combined with behavioural preference for favourable host species, these divergent adaptations can induce pre- and post-zygotic barriers between host-specialized aphid populations. However, the hypothesis of host-driven speciation is seldom tested formally and must be weighed against overlooked explanations involving geographic isolation and non-ecological reproductive barriers in the process of speciation.

Brammer, C. A. & von Dohlen, C. D. (2010). Morphological phylogeny of the variable fly family Stratiomyidae (Insecta, Diptera). —Zoologica Scripta, 39, 363–377. Stratiomyidae is a dipteran family distributed worldwide and containing 2800 species classified into 12 subfamilies. Previous phylogenetic work on the Stratiomyidae consisted of a 20-character morphological analysis of the subfamilies [World Catalog of the Stratiomyidae (Insect: Diptera). Leiden: Backhuys Publishers, 2001], and a molecular study using 69 taxa and two gene regions [Molecular Phylogenetics and Evolution, 43, 2007, 660]. In this study, we present an expanded morphological cladistic analysis using 92 characters and 80 taxa, representing 36 of 39 described genera and all 12 Stratiomyidae subfamilies, as well as Xylomyidae and Pantophthalmidae outgroups. Data are analysed under maximum parsimony with all characters unordered and weighted equally; nodal support is assessed with the bootstrap and Bremer index. The strict consensus of all shortest trees is well resolved, and many of the deeper nodes are supported, although the root is ambiguous. Antissinae, Stratiomyinae, Sarginae and the diverse Clitellariinae are not monophyletic. Clitellariinae are positioned across several lineages, with most species grouped into a single, unsupported clade. Many of the well-supported relationships are consistent with several aspects of the previous studies. The position of Exodontha remains elusive. Character support for subfamilies and other major clades is discussed.

Sand dunes in the Mojave and Great Basin Deserts are unique habitats that often harbor distinct and endemic taxa (Ricketts et al., 1999). Epps et al. (1998) compared sand dunes to ‘‘habitat islands’’ in the desert, which provide habitat for many sand-obligate organisms. Because many of these dunes are distant from other dunes, and often flanked by mountain ranges or alkaline hardpan, isolated populations of dune-restricted organisms are often genetically distinct (e.g., Britten and Rust, 1996; Epps et al., 1998). We attempted to discover phylogeographic patterns among populations of Colletes stepheni Timberlake, a sand dune restricted, oligolectic solitary bee. Colletes stepheni nests solely in loose sandy substrates and provisions its nest with pollen only from a limited number of plant species (Hurd and Powell, 1958; Minckley et al., 2000; Andrus, 2003). Populations of C. stepheni in the Mojave Desert use pollen only from Larrea tridentata (creosote bush; Zygophylaceae), which is a common shrub in the hot deserts of North America, while populations in the Great Basin Desert, a cold desert, use pollen from Psorothamnus (indigo bush; Fabaceae) (Andrus, 2003). Andrus (2003) attempted to find phylogeographic patterns among populations of C. stepheni from 13 dune sites across the Mojave and Great Basin Deserts using mtDNA. These attempts uncovered the presence of nuclear mitochondrial pseudogenes (NUMTS), which are mitochondrial genes that have been incorporated into the nuclear genome (Margulis, 1970). The presence of these pseudogenes in C. stepheni made the use of mtDNA for phylogeographic analyses difficult, if not impossible. While the majority of phylogeographic analyses use mtDNA, particularly the gene COI, to investigate phylogeographic patterns, several recent studies employ various nuclear genes to uncover intraspecific variation. For example, a phylogeographic study of sea urchins found that the internal transcribed spacer region 2 was more variable at the population level than COI (Iuri et al., 2007). Studies on several other taxa have also shown that the internal transcribed spacer regions 1 and 2 (ITS1 & ITS2) are variable at the population level (e.g., Mavarez et al., 2002; Gomez-Zurita and Vogler, 2003; Holderegger and Abbott, 2003). While nuclear genes are not widely used in phylogeographic studies of Hymenoptera, several recent studies have found population-level variation in various hymenopterans. For example, variation has been found among populations of stingless bees (De la Rua et al., 2007), an encyrtid wasp (Alvarez and Hoy, 2002), an oak gallwasp (Rokas et al., 2001), and several velvet ant species (Wilson and Pitts, 2008, 2009). Other studies on velvet ants (Hymenoptera: Mutillidae), while not specifically investigating intraspecific variation, showed that such variation exists in both the ITS1 and ITS2 sequences (Pilgrim and Pitts, 2006; Pitts et al., 2007; Pilgrim et al., 2008). Another nuclear gene, Long-wavelength rhodopsin (opsin), has not been widely used in population-level analyses, but has three introns (167 total bp in C. stepheni), which have been informative in differentiating between isolated populations of mutillid wasps (Wilson and Pitts, unpubl. data). Also, Almeida and Danforth (2009) in a phylogenetic analysis of colletid bees found that the introns of opsin were too variable to be used in a species-level analysis. This would suggest that the introns might be informative at the intraspecies level. Kuhlmann et al. (2007) found population-level differences in the introns of another nuclear gene Elongation Factor 1-Alpha for Colletes halophilus as well. In this study, we attempted to find phylogeographic patterns using three nuclear genes, the two rDNA internal transcribed spacer regions (ITS1 & ITS2), and the long-wavelength rhodopsin gene (Opsin).

Sympetrinae is the largest subfamily of the diverse dragonfly family Libellulidae. This subfamily, like most libellulid subfamilies, is defined currently by a few wing venation characters, none of which are synapomorphies for the taxon. In this study, we used DNA sequence data from the nuclear locus elongation factor-1a and the mitochondrial loci 16S and 12S rRNA, together with 38 wing venation characters, to test the monophyly of the Sympetrinae and several other libellulid subfamilies. No analysis recovered Sympetrinae as mono- phyletic, partly because of the position of Leucorrhinia (of the subfamily Leucorrhininae) as a strongly supported sister to Sympetrum (of Sympetrinae) in all analyses. The subfamilies Brachydiplactinae, Leucorrhininae, Trameinae and Trithemistinae were also found not to be monophyletic. Libellulinae was the only subfamily supported strongly as monophyletic. Consistency indices and retention indices of wing venation characters used to define various subfamilies were closer to zero than unity, showing that many of these characters were homoplasious, and therefore not useful for a classification scheme within Libellulidae.

This study combines morphological and molecular data to address several questions of species validity within the dragonfly genus Sympetrum. We compared morphological characters (genitalia and other putatively diagnostic characters) and DNA sequences from mitochondrial cytochrome oxidase I (COI) and nuclear internal transcribed spacer (ITS) regions between these disputed taxa and their close relatives. Specimens of Sympetrum nigrescens Lucas shared COI haplotypes with Sympetrum striolatum (Charpentier), and no morphological characters consistently diagnosed S. nigrescens, which therefore becomes a junior synonym of S. striolatum. Similarly, Sympetrum occidentale Bartenev shared identical COI and ITS sequences with Sympetrum semicinctum (Say), and the supposed diagnostic morphological characters overlapped with the intraspecific variation within S. semicinctum. Sympetrum occidentale becomes a junior synonym of S. semicinctum. In a third case, the genetic distance between Sympetrum signiferum Cannings & Garrison and Sympetrum vicinum (Hagen) was lower than that found between most undisputed species. However, the morphological characters that distinguish S. signiferum from S. vicinum were distinct and consistent, and they supported the retention of S. signiferum as a valid species. In the fourth case, neither morphological nor genetic data were able to distinguish Sympetrum janeae Carle consistently from Sympetrum internum Montgomery, or Sympetrum rubicundulum (Say); in addition, genetic distances between individuals of S. internum and S. rubicundulum were small or nonexistent. Further studies are necessary to test the species status of S. janeae and its close relatives.

Pompilinae is one of the largest subfamilies of spider wasps (Pompilidae). Most pompilines are generalist spider predators at the family level, but some taxa exhibit ecological specificity (i.e., to spider-host guild). Here we present the first molecular phylogenetic analysis of Pompilinae, toward the aim of evaluating the monophyly of tribes and genera. We further test whether changes in the rate of diversification are associated with host-guild shifts. Molecular data were collected from five nuclear loci (28S, EF1-F2, LWRh, Wg, Pol2) for 76 taxa in 39 genera. Data were analyzed using maximum likelihood (ML) and Bayesian inference (BI). The phylogenetic results were compared with previous hypotheses of subfamilial and tribal classification, as well as generic relationships in the subfamily. The classification of Pompilus and Agenioideus is also discussed. A Bayesian relaxed molecular clock analysis was used to examine divergence times. Diversification rate-shift tests accounted for taxon-sampling bias using ML and BI approaches. Ancestral host family and host guild were reconstructed using MP and ML methods. Ancestral host guild for all Pompilinae, for the ancestor at the node where a diversification rate-shift was detected, and two more nodes back in time was inferred using BI. In the resulting phylogenies, Aporini was the only previously proposed monophyletic tribe. Several genera (e.g., Pompilus, Microphadnus and Schistonyx) are also not monophyletic. Dating analyses produced a well-supported chronogram consistent with topologies from BI and ML results. The BI ancestral host-use reconstruction inferred the use of spiders belonging to the guild "other hunters" (frequenting the ground and vegetation) as the ancestral state for Pompilinae. This guild had the highest probability for the ML reconstruction and was equivocal for the MP reconstruction; various switching events to other guilds occurred throughout the evolution of the group. The diversification of Pompilinae shows one main rate-shift coinciding with a shift to ground-hunter spiders, as reconstructed by the BI ancestral character-state analysis.

Spider wasps had long been proposed to originate in the Late Cretaceous based on the Burmese amber fossil Bryopompilus interfector. We performed a morphological examination of this fossil and determined that it does not belong to Pompilidae or any other described hymenopteran family. Instead, we place it in the new family Bryopompilidae. The oldest verifiable member of the Pompilidae is from Baltic amber, which suggests that the crown group of the family probably originated in the Eocene, not in the Late Cretaceous as previously proposed. The origin of spider wasps appears to be correlated with an increase in spider familial diversity in the Cenozoic. We also add two genera to the extinct pompilid fauna: Tainopompilus Rodriguez and Pitts gen. nov. and Paleogenia Waichert and Pitts gen. nov., and describe three new species of fossil spider wasps: Anoplius planeta Rodriguez and Pitts sp. nov., from Dominican amber (Burdigalian to Langhian); Paleogenia wahisi Waichert and Pitts sp. nov., from Baltic amber (L...

Phragmatopoma spp. are marine, reef-building polychaetes that inhabit the intertidal and shallow subtidal zones of both coasts of the Americas. Phragmatopoma californica is found in the Pacific Ocean along the California coast south to Mexico, while Phragmatopoma caudata inhabits the Caribbean islands and Atlantic Ocean from the Florida coast south to Brazil. Although apparently geographically isolated, P. californica and P. caudata have been found to interbreed (Pawlik 1988a) and thus their specific taxonomic relationship has been unclear. In this study, two genes, cytochrome c oxidase subunit I (COI) and the first internal transcribed spacer region (ITS-1), were sequenced to assess the specific status of P. californica and P. caudata as well as Phragmatopoma virgini. Comparison of sequences revealed that samples of P. californica shared no COI haplotypes or ITS-1 sequences with P. caudata. Phylogenetic analyses, including maximum parsimony and Bayesian methods, clustered each species in separate, well-supported clades with genetic distances between them being greater than between either contested species or the uncontested, valid species, P. virgini. Thus, the molecular data support that P. californica and P. caudata are separate species. However, the sample of individuals of P. virgini included one genetically divergent individual, whose morphology was found to match that of a species formerly recognized as P. moerchi but since synonymized with P. virgini. Divergences among lineages were dated using the COI sequences, after adjustment for non-clock-like behavior. Consequently, we suggest that P. virgini and P. caudata are sister taxons and that P. californica diverged from the P. virgini/P. caudata clade ∼5.7 mya with P. virgini diverging from P. caudata ∼3 mya.

No qualitative cladistic analysis has been performed previously for the subfamily classification of Pompilidae (Hymenoptera). In 1994 Shimizu proposed six subfamilies, but their validity and relationships remain inconclusive. The objective of this study was to perform a quantitative analysis of phylogenetic relationships of the Pompilidae, with emphasis on testing the validity of proposed subfamilies. Two cladistic analyses were performed based on morphological evidence. First, a maximum-parsimony analysis of Shimizu's original morphological data matrix (72 taxa by 54 characters) was conducted, with the data subjected to a heuristic search for the first time with phylogenetic software. The resulting strict-consensus cladogram yielded a monophyletic Ceropalinae that was sister group to a large polytomy containing members of the remaining five subfamilies. In a second analysis, several of Shimizu's characters were re-examined, and new characters and more taxa were added to the data set. Terminal taxa were coded as species rather than as generic abstractions, and 20 additional morphological characters were introduced. The analysis was based on 77 morphological characters derived from the adults of 84 taxa. This second analysis suggested that Notocyphinae sensu Shimizu (1994) was nested within Pompilinae and that Epipompilinae sensu Shimizu (1994) was nested within Ctenocerinae; neither should retain their status as a separate subfamily. Lastly, Chirodamus s.s., which historically has been a member of the Pepsinae, is placed within the Pompilinae with reservations rather than erecting a new subfamily. After these allowances were made, a strict consensus tree gave the following relationships: (Ceropalinae + (Pepsinae + (Ctenocerinae + Pompilinae))).

Aphids (Hemiptera: Sternorrhyncha: Aphididae) are most diverse in the temperate northern hemisphere, with only a few lineages native to the southern hemisphere. The highly diverse subfamily Aphidinae probably gained its dominance from a successful northern hemisphere radiation in the Tertiary. A few species in the tribe Aphidini, however, are indigenous to Gondwanan regions, including New Zealand and Australia. The conventional view is that these species dispersed to the south from the northern hemisphere after the main Tertiary radiation. We tested this hypothesis in a phylogenetic context by reconstructing relationships among New Zealand indigenous Aphidini, as well as their relationships to several northern taxa. Phylogenies were reconstructed from molecular data using independent and combined analyses of mitochondrial tRNA leucine + cytochrome oxidase II and nuclear elongation factor-1α (EF1α) sequences, with both parsimony and maximum likelihood methods. These analyses recovered a highly sup...

A conspicuous biogeographic pattern of the Northern Hemisphere is the disjunct occurrence of related taxa on different continents. Perhaps best studied in plants, this pattern includes disjunct distributions of genera in eastern Asia and eastern North America. Such continental disjunctions are thought to be the remnants of a mostly continuously distributed, mixed mesophytic forest dating to the Miocene, which subsequently became fragmented by geological and climatic changes. Some highly host-specific insects, namely aphids, live on descendants of the mixed mesophytic forest taxa and exhibit the same disjunct distributions as that of their host plants. We estimated the phylogeny of Hormaphidini aphids, which host-alternate between witch-hazel (Hamamelis; an eastern Asian-eastern North American disjunct genus) and birch (Betula). Based on partial nuclear elongation factor 1alpha and mitochondrial tRNA leucine/cytochrome oxidase II sequences, trees inferred from maximum-parsimony and maximum-likelihood showed strong support for two monophyletic genera (Hamamelistes and Hormaphis), each containing a clade of Japanese and a clade of North American species. The estimated divergence dates of Asian and North American clades in both genera was 20-30 million years ago, consistent with the idea that aphids may have experienced the same vicariance events as those of their host plants.

For decades, biologists have debated why many parasites have obligate multihost life cycles. Here, we use comparative phylogenetic analyses of aphids to evaluate the roles of ecological optimization and historical constraint in the evolution of life cycle complexity. If life cycle complexity is adaptive, it should be evolutionarily labile, that is, change in response to selection. We provide evidence that this is true in some aphids (aphidines), but not others (nonaphidines)-groups that differ in the intensity of their relationships with primary hosts. Next, we test specific mechanisms by which life cycle complexity could be adaptive or a constraint. We find that among aphidines there is a strong association between complex life cycles and polyphagy but only a weak correlation between life cycle complexity and reproductive mode. In contrast, among nonaphidines the relationship between life cycle complexity and host breadth is weak but the association between complex life cycles and sexual reproduction is strong. Thus, although the adaptiveness of life cycle complexity appears to be lineage specific, across aphids, life cycle evolution appears to be tightly linked with the evolution of other important natural history traits.

A fungal endophyte of wheat causing seedling necrosis when plants are grown under stressed conditions was identified as a Fusarium proliferatum (Matsushima) Nirenberg isolate (NRRL 31017). The wheat isolate grew rapidly on potato dextrose agar as lanose to cottony colonies and rarely produced macroconidia under ultraviolet light. Microconidia were produced both in false heads and chains; sporodochia and chlamydospores were not found. Phylogenetic analysis of the nucleotide sequences of the genes for β-tubulin, mitochondrial small subunit ribosomal DNA, calmodulin, and elongation factor 1-α from the wheat isolate showed affinity with other F. proliferatum isolates. The closest relationship was with an isolate with ligninolytic potential obtained from forest litter in Spain (F. proliferatum MUCL 31970). Nucleotide sequences of genes encoding laccases, which are quite divergent between fungal species, showed 99% identity between the wheat and the forest litter isolates.Key words: Fusarium proliferatum, laccase, phylogeny, genetic variability.

Some insects have cultivated intimate relationships with mutualistic bacteria since their early evolutionary history. Most ancient 'primary' endosymbionts live within the cytoplasm of large, polyploid host cells of a specialized organ (bacteriome). Within their large, ovoid bacteriomes, mealybugs (Pseudococcidae) package the intracellular endosymbionts into 'mucus-filled' spheres, which surround the host cell nucleus and occupy most of the cytoplasm. The genesis of symbiotic spheres has not been determined, and they are structurally unlike eukaryotic cell vesicles. Recent molecular phylogenetic and fluorescent in situ hybridization (FISH) studies suggested that two unrelated bacterial species may share individual host cells, and that bacteria within spheres comprise these two species. Here we show that mealybug host cells do indeed harbour both beta- and gamma-subdivision Proteobacteria, but they are not co-inhabitants of the spheres. Rather, we show that the symbiotic spheres themselves are beta-proteobacterial cells. Thus, gamma-Proteobacteria live symbiotically inside beta-Proteobacteria. This is the first report, to our knowledge, of an intracellular symbiosis involving two species of bacteria.

Eubacterial 16S rDNAs were sequenced from endosymbionts of seven psyllids (Psylloidea) and one whitefly (Aleyrodoidea), to investigate the evolution of endosymbionts and their hosts. Primary endosymbionts from all psyllids formed a highly supported clade, tentatively placed as the sister to whitefly primary endosymbionts, and showing several points of congruence with the host morphological phylogeny. Almost all host taxa yielded an additional eubacterial sequence, related either to known psyllid secondary endosymbionts or to other insect endosymbionts or parasites. The relationships of some secondary endosymbionts also suggested cospeciation with psyllid hosts, or ancient horizontal transfers. All primary endosymbionts, and some secondary endosymbionts, exhibited molecular genetic effects of a long-term, intracellular existence in their biased nucleotide content and decreased stability of rRNA secondary structure.

Many aphids display a remarkably complex life cycle of host alternation, in which cyclical parthenogenesis is combined with the obligate use of two unrelated host plants. We used mitochondrial ribosomal DNA (partial 12S and 16S) sequences to reconstruct the phylogeny of aphids, to determine how many origins of host alternation and correlated major host-plant shifts have occurred. Our results agreed with previous morphological studies in that species clustered with good support at the level of tribes. There was little well-supported phylogenetic structure at levels deeper than tribes, however, except for the monophyly of two subfamilies, Aphidinae and Lachninae. We argue that aphids experienced a rapid radiation at the tribal level, after host shifting from gymnosperms to angiosperms. A rapid radiation is consistent with aphid fossils, which record the presence of few subfamilies in the late Cretaceous, but most extant tribes by the early Tertiary. Plant fossils also record host plants of aphid tribes diversifying during this time. A hypothesized mechanism by which host alternation has evolved (fundatrix specialization), coupled with the rapid radiation, implies that this life cycle may have originated as often as in the ancestor of each tribe that displays it. We also consider, however, an alternative hypothesis of fewer origins. The basal radiation of Aphididae was dated from molecular sequences to have occurred at approximately 80–150 Mya.