Phylogeny of hydradephagan water beetles inferred from 18S rRNA sequences

Morphology and distribution of sensilla on head appendages in the water beetle Hygrobia hermanni (Coleoptera: Adephaga: Hygrobiidae)

Sensilla on head appendages were studied in detail for the first time in a member of the relict family Hygrobiidae (squeak beetles), closely related to Dytiscidae (diving beetles). Adult and third instar larval stage specimens of Hygrobia hermanni (Fabricius, 1775) were examined using scanning electron microscopy, focusing on antennae, palps and larval mandibles. In total, 37 sensilla subtypes are described, including 22 observed in the adult (basiconica: 3; Böhm's bristles: 2; circumvallate sensilla: 2; coeloconica: 10; ovoid placodea: 3; digitiform placodea: 2) and 16 in the larva (basiconica: 4; campaniformia: 1; chaetica: 4; coeloconica: 5; trichodea: 1; unnamed: 1). Only one subtype (of sensilla coeloconica) was shared between the adult and the larva. Autapomorphies of Hygrobiidae and Dytiscidae, and putatively shared derived characters (synapomorphies) of Hygrobiidae + Dytiscidae are discussed. Among the latter, the most remarkable is the acquisition of a special sensory field, located on the apical segment of the adult maxillary palp, subapically and postero-dorsally. This sensory field is made up of ovoid multiporous sensilla placodea otherwise present on the anterior (internal) surface of antennal segments, suggesting that in a common ancestor of Hygrobiidae and Dytiscidae, maxillary palps might have taken over enhanced capacities of longe-range molecule detection.

Data curation and modeling of compositional heterogeneity in insect phylogenomics: A case study of the phylogeny of Dytiscoidea (Coleoptera: Adephaga)

Diving beetles and their allies are an almost ubiquitous group of freshwater predators. Knowledge of the phylogeny of the adephagan superfamily Dytiscoidea has significantly improved since the advent of molecular phylogenetics. However, despite recent comprehensive phylogenomic studies, some phylogenetic relationships among the constituent families remain elusive. In particular, the position of the family Hygrobiidae remains uncertain. We address these issues by re-analyzing recently published phylogenomic datasets for Dytiscoidea, using approaches to reduce compositional heterogeneity and adopting a site-heterogeneous mixture model. We obtained a consistent, well-resolved, and strongly supported tree. Consistent with previous studies, our analyses support Aspidytidae as the monophyletic sister group of Amphizoidae, and more importantly, Hygrobiidae as the sister of the diverse Dytiscidae, in agreement with morphology-based phylogenies. Our analyses provide a backbone phylogeny of Dytiscoidea, which lays the foundation for better understanding the evolution of morphological characters, life habits, and feeding behaviors of dytiscoid beetles.

Phylogenetic placement of the Pacific Northwest subterranean endemic diving beetle Stygoporus oregonensis Larson & LaBonte (Dytiscidae, Hydroporinae)

Stygoporus oregonensis Larson & LaBonte is a little-known subterranean diving beetle, which, until recently, had not been collected since the type series was taken from a shallow well in western Oregon, USA, in 1984. Here we report the discovery of additional specimens collected from a nearby well in the Willamette Valley. Sequence data from four mitochondrial genes, wingless, and histone III place Stygoporus Larson & LaBonte in the predominantly Mediterranean subtribe Siettitiina of the Hydroporini. Morphological support for these results is discussed, and details of the collecting circumstances of the new specimens are presented. We argue that the biogeographic patterns of Nearctic Siettitiina highlight the likelihood of additional undiscovered subterranean dytiscids in North America.

Land management practices interactively affect wetland beetle ecological and phylogenetic community structure

Management practices can disturb ecological communities in grazing lands, which represent one-quarter of land surface. But three knowledge gaps exist regarding disturbances: disturbances potentially interact but are most often studied singly; experiments with multiple ecosystems as treatment units are rare; and relatively new metrics of phylogenetic community structure have not been widely applied. We addressed all three of these needs with a factorial experiment; 40 seasonal wetlands embedded in a Florida ranch were treated with pasture intensification, cattle exclosure, and prescribed fire. Treatment responses were evaluated through four years for aquatic beetle (Coleoptera: Adephaga) assemblages using classic ecological metrics (species richness, diversity) and phylogenetic community structure (PCS) metrics. Adephagan assemblages consisted of 23 genera representing three families in a well-resolved phylogeny. Prescribed fire significantly reduced diversity one year post-fire, followed by a delayed pasture X fire interaction. Cattle exclosure significantly reduced one PCS metric after one year and a delayed pasture x fence x fire interaction was detected with another PCs metric. Overall, effects of long-term pasture intensification were modified by cattle exclosure and prescribed fire. Also, PCS metrics revealed effects otherwise undetected by classic ecological metrics. Management strategies (e.g., "flash grazing," prescribed fires) in seasonal wetlands may successfully balance economic gains from high forage quality with ecological benefits of high wetland diversity in otherwise simplified grazing lands. Effects are likely taxon specific; multiple taxa should be similarly evaluated.

Catalogue of Geadephaga (Coleoptera, Adephaga) of America, north of Mexico

All scientific names of Trachypachidae, Rhysodidae, and Carabidae (including cicindelines) recorded from America north of Mexico are catalogued. Available species-group names are listed in their original combinations with the author(s), year of publication, page citation, type locality, location of the name-bearing type, and etymology for many patronymic names. In addition, the reference in which a given species-group name is first synonymized is recorded for invalid taxa. Genus-group names are listed with the author(s), year of publication, page citation, type species with way of fixation, and etymology for most. The reference in which a given genus-group name is first synonymized is recorded for many invalid taxa. Family-group names are listed with the author(s), year of publication, page citation, and type genus. The geographical distribution of all species-group taxa is briefly summarized and their state and province records are indicated.One new genus-group taxon, Randallius new subgenus (type species: Chlaenius purpuricollis Randall, 1838), one new replacement name, Pterostichus amadeus new name for Pterostichus vexatus Bousquet, 1985, and three changes in precedence, Ellipsoptera rubicunda (Harris, 1911) for Ellipsoptera marutha (Dow, 1911), Badister micans LeConte, 1844 for Badister ocularis Casey, 1920, and Agonum deplanatum Ménétriés, 1843 for Agonum fallianum (Leng, 1919), are proposed. Five new genus-group synonymies and 65 new species-group synonymies, one new species-group status, and 12 new combinations (see Appendix 5) are established.The work also includes a discussion of the notable private North American carabid collections, a synopsis of all extant world geadephagan tribes and subfamilies, a brief faunistic assessment of the fauna, a list of valid species-group taxa, a list of North American fossil Geadephaga (Appendix 1), a list of North American Geadephaga larvae described or illustrated (Appendix 2), a list of Geadephaga species described from specimens mislabeled as from North America (Appendix 3), a list of unavailable Geadephaga names listed from North America (Appendix 4), a list of nomenclatural acts included in this catalogue (Appendix 5), a complete bibliography with indication of the dates of publication in addition to the year, and indices of personal names, supraspecific names, and species-group names.

Geographic location and phylogeny are the main determinants of the size of the geographical range in aquatic beetles

Background

Why some species are widespread while others are very restricted geographically is one of the most basic questions in biology, although it remains largely unanswered. This is particularly the case for groups of closely related species, which often display large differences in the size of the geographical range despite sharing many other factors due to their common phylogenetic inheritance. We used ten lineages of aquatic Coleoptera from the western Palearctic to test in a comparative framework a broad set of possible determinants of range size: species' age, differences in ecological tolerance, dispersal ability and geographic location.

Results

When all factors were combined in multiple regression models between 60-98% of the variance was explained by geographic location and phylogenetic signal. Maximum latitudinal and longitudinal limits were positively correlated with range size, with species at the most northern latitudes and eastern longitudes displaying the largest ranges. In lineages with lotic and lentic species, the lentic (better dispersers) display larger distributional ranges than the lotic species (worse dispersers). The size of the geographical range was also positively correlated with the extent of the biomes in which the species is found, but we did not find evidence of a clear relationship between range size and age of the species.

Conclusions

Our findings show that range size of a species is shaped by an interplay of geographic and ecological factors, with a phylogenetic component affecting both of them. The understanding of the factors that determine the size and geographical location of the distributional range of species is fundamental to the study of the origin and assemblage of the current biota. Our results show that for this purpose the most relevant data may be the phylogenetic history of the species and its geographical location.

Monophyly of terrestrial adephagan beetles as indicated by three nuclear genes (Coleoptera: Carabidae and Trachypachidae)

The beetle suborder Adephaga is traditionally divided into two sections on the basis of habitat, terrestrial Geadephaga and aquatic Hydradephaga. Monophyly of both groups is uncertain, and the relationship of the two groups has implications for inferring habitat transitions within Adephaga. Here we examine phylogenetic relationships of these groups using evidence provided by DNA sequences from all four suborders of beetles, including 60 species of Adephaga, four Archostemata, three Myxophaga, and ten Polyphaga. We studied 18S ribosomal DNA and 28S ribosomal DNA, aligned with consideration of secondary structure, as well as the nuclear protein-coding gene wingless. Independent and combined Bayesian, likelihood, and parsimony analyses of all three genes supported placement of Trachypachidae in a monophyletic Geadephaga, although for analyses of 28S rDNA and some parsimony analyses only if Coleoptera is constrained to be monophyletic. Most analyses showed limited support for the monophyly of Hydradephaga. Outside of Adephaga, there is support from the ribosomal genes for a sister group relationship between Adephaga and Polyphaga. Within the small number of sampled Polyphaga, analyses of 18S rDNA, wingless, and the combined matrix supports monophyly of Polyphaga exclusive of Scirtoidea. Unconstrained analyses of the evolution of habitat suggest that Adephaga was ancestrally aquatic with one transition to terrestrial. However, in analyses constrained to disallow changes from aquatic to terrestrial habitat, the phylogenies imply two origins of aquatic habit within Adephaga.

Infrequent and unidirectional colonization of hyperdiverse Papuadytes diving beetles in New Caledonia and New Guinea

We present a molecular phylogenetic analysis of 2808 aligned bp of rrnL, cox1, cob, H3 and 18S rRNA of all major morphological groups of Papuadytes diving beetles (Coleoptera: Dytiscidae) which are diverse in running water habitats throughout the Australian region. We focus on the origin of the fauna of the megadiverse islands of New Guinea and New Caledonia. Parsimony as well as Bayesian analyses suggest a basal position of Australian species in a paraphyletic series, with more recent nested radiations in New Caledonia and New Guinea. According to molecular clock analyses, both landmasses were colonized during the Miocene, which matches geological data and corroborates similar findings in other taxonomic groups. Our analyses suggest that dispersal played an important role in the formation of these large insular faunas, although successful colonization appears to be a rare event, and, in this case, is unidirectional. Whether or not a lineage is present on an island is due to chance: Papuadytes are absent from Fiji, where related Copelatus have radiated extensively in the same habitats occupied by Papuadytes in New Caledonia and New Guinea, while Copelatus are absent from New Caledonia. Lineages of Papuadytes apparently colonized New Caledonia twice, around 14 and 9 MYA according to the molecular calibration, and both lineages are derived from an Australian ancestor. The older clade is represented only by two apparently relictual mountain species (one morphologically strongly adapted to highly ephemeral habitats), while the younger clade contains at least 18 species exhibiting a great morphological diversity. The 150+ species in New Guinea are monophyletic, apparently derived from an Australian ancestor, and constitute a morphologically rather homogenous group. The tree backbone remains insufficiently supported under parsimony and Bayesian analyses, where shorter branches suggest a rapid sequence of major branching events.

MtDNA phylogeny and biogeography of Copelatinae, a highly diverse group of tropical diving beetles (Dytiscidae)

Copelatinae is a diverse lineage of diving beetles (Dytiscidae) frequently encountered in wet tropical and subtropical forests, but phylogenetic relationships are very poorly understood. We performed a phylogenetic and biogeographic analysis of this worldwide distributed group based on 50 species including a representative sample of major taxonomic groups and biogeographical regions. DNA sequences were obtained for the mitochondrial genes cytochrome oxidase I, cytochrome b, and 16S rRNA, for a total of 1575 aligned nucleotide positions. We found Copelatinae to be monophyletic, placed in a derived position and not sister to all remaining dytiscids, as had been suggested by earlier authors. The largest genus, Copelatus with some 460 known species was paraphyletic with respect to the smaller genera Lacconectus and Aglymbus. Among the major lineages of Copelatus, the subgenus Papuadytes was consistently recovered as sister to all other species (including Lacconectus and Aglymbus) with the possible exception of two western Palearctic taxa. We propose that the subgenus Papuadytes is removed from Copelatus and assigned generic status. Likewise, the two western Palearctic Copelatus are removed from this genus, and assigned the available genus name Liopterus. Our best phylogenetic hypothesis retrieved Afrotropical and New Guinean plus Australian species of Copelatus as monophyletic. Asian species were paraphyletic with respect to a species from Sulawesi which grouped with the species from New Guinea. Asian species were also paraphyletic with respect to Oriental Lacconectus, which was grouped with a clade of Neotropical species. Neotropical Copelatus form at least two separate lineages. The biogeographical evolution of Papuadytes is consistent with the relative age of the landmasses in the Austral region. Basal species are Australian, and successively derived ones are from New Caledonia and New Guinea. One species apparently dispersed from New Caledonia to China. Assuming a molecular clock and using a standard calibration of 2% divergence/MY the origin of Copelatinae is estimated to be between 85 and 95 MY.

On the constitution and phylogeny of Staphyliniformia (Insecta: Coleoptera)

The Staphyliniformia is one of the most diverse lineages of Coleoptera, with representatives occupying every conceivable non-marine niche. Phylogenetic relationships among its varied families and lower taxa have defied resolution. The problem has been further complicated by the recent suggestion that another major coleopteran series, Scarabaeiformia, is derived from within it. Here we present the first phylogenetic analyses, based on 18S rDNA sequences and morphological data, to explicitly examine this possibility. Thorough evaluation of alternative alignments and tree construction methods support the contention that Scarabaeiformia is derived from within Staphyliniformia. Though the analyses yielded strong support for few family level groupings within the expanded Staphyliniformia, they conclusively support a close relationship between Hydraenidae and Ptiliidae, which has often been debated. The primary factor hindering additional resolution appears to be the inconsistent rate of divergence in 18S among these taxa.

Phylogeny and historical biogeography of Agabinae diving beetles (Coleoptera) inferred from mitochondrial DNA sequences

The Agabinae, with more than 350 species, is one of the most diverse lineages of diving beetles (Dytiscidae). Using the mitochondrial genes 16S rRNA and cytochrome oxidase I we present a phylogenetic analysis based on 107 species drawn mostly from the four main Holarctic genera. Two of these genera (Ilybius and Ilybiosoma) are consistently recovered as monophyletic with strong support, Platambus is never recovered as monophyletic, and Agabus is found paraphyletic with respect to several of the species groups of Platambus. Basal relationships among the main lineages are poorly defined, although within each of them relationships are in general robust and very consistent across the parameter space, and in agreement with previous morphological analyses. In each of the two most diverse lineages (Ilybius and Agabus including part of Platambus) there is a basal split between Palearctic and Nearctic clades, estimated to have occurred in the late Eocene. The Palearctic clade in turn splits into a Western Palearctic clade and a clade containing mostly Eastern Palearctic species, and assumed to be ancestrally Eastern Palearctic but with numerous transitions to a Holarctic or Nearctic distribution. These results suggest an asymmetry in the colonization routes, as there are very few cases of transcontinental range expansions originating from the Nearctic or the Western Palearctic. According to standard clock estimates, we do not find any transcontinental shift during the Pliocene, but numerous speciation events within each of the continental or subcontinental regions.

Discovery of Aspidytidae, a new family of aquatic Coleoptera

The six extant aquatic families of Hydradephaga (Coleoptera) known so far represent a diverse group of beetles morphologically highly modified for life in the water. We report the discovery of a new genus with two species from South Africa and China, which differ greatly from all extant families, but resemble the Jurassic-Cretaceous dagger Liadytidae (the dagger symbol indicates that the taxa are known only as fossils). Based on a combined phylogenetic analysis of molecular and morphological data we erect a new family, Aspidytidae, which is the sister group of Dytiscidae plus Hygrobiidae. We propose a new scenario for the evolution of swimming behaviour in adephagan beetles, in which the transition into the aquatic environment is followed by complex and repeated changes in lifestyles, including the secondary complete loss of swimming ability in Aspidytidae.