Time flies, a new molecular time-scale for brachyceran fly evolution without a clock

The insect order Diptera, the true flies, contains one of the four largest Mesozoic insect radiations within its suborder Brachycera. Estimates of phylogenetic relationships and divergence dates among the major brachyceran lineages have been problematic or vague because of a lack of consistent evidence and the rarity of well-preserved fossils. Here, we combine new evidence from nucleotide sequence data, morphological reinterpretations, and fossils to improve estimates of brachyceran evolutionary relationships and ages. The 28S ribosomal DNA (rDNA) gene was sequenced for a broad diversity of taxa, and the data were combined with recently published morphological scorings for a parsimony-based phylogenetic analysis. The phylogenetic topology inferred from the combined 28S rDNA and morphology data set supports brachyceran monophyly and the monophyly of the four major brachyceran infraorders and suggests relationships largely consistent with previous classifications. Weak support was found for a basal brachyceran clade comprising the infraorders Stratiomyomorpha (soldier flies and relatives), Xylophagomorpha (xylophagid flies), and Tabanomorpha (horse flies, snipe flies, and relatives). This topology and similar alternative arrangements were used to obtain Bayesian estimates of divergence times, both with and without the assumption of a constant evolutionary rate. The estimated times were relatively robust to the choice of prior distributions. Divergence times based on the 28S rDNA and several fossil constraints indicate that the Brachycera originated in the late Triassic or earliest Mesozoic and that all major lower brachyceran fly lineages had near contemporaneous origins in the mid-Jurassic prior to the origin of flowering plants (angiosperms). This study provides increased resolution of brachyceran phylogeny, and our revised estimates of fly ages should improve the temporal context of evolutionary inferences and genomic comparisons between fly model organisms.     

Relationships of extant lower Brachycera (Diptera): a quantitative synthesis of morphological characters

With over 80 000 described species, Brachycera represent one of the most diverse clades of organisms with a Mesozoic origin. Larvae of the majority of early lineages are detritivores or carnivores. However, Brachycera are ecologically innovative and they now employ a diverse range of feeding strategies. Brachyceran relationships have been the subject of numerous qualitative analyses using morphological characters. These analyses are often based on characters from one or a few character systems and general agreement on relationships has been elusive. In order to understand the evolution of basal brachyceran lineages, 101 discrete morphological characters were scored and compiled into a single data set. Terminals were scored at the family level, and the data set includes characters from larvae, pupae and adults, internal and external morphology, and male and female terminalia. The results show that all infraorders of Brachycera are monophyletic, but there is little evidence for relationships between the infraorders. Stratiomyomorpha, Tabanomorpha, and Xylophagomorpha together form the sister group to Muscomorpha. Xylophagomorpha and Tabanomorpha are sister groups. Within Muscomorpha, the paraphyletic Nemestrinoidea form the two most basal lineages. There is weak evidence for the monophyly of Asiloidea, and Hilarimorphidae appear to be more closely related to Eremoneura than other muscomorphs. Apsilocephalidae, Scenopinidae and Therevidae form a clade of Asiloidea. This phylogenetic evidence is consistent with the contemporaneous differentiation of the main brachyceran lineages in the early Jurassic. The first major radiation of Muscomorpha were asiloids and they may have diversified in response to the radiation of angiosperms in the early Cretaceous.     

General structure of the mushroom body calyx in brachycera orthorrhapha flies (Diptera)

The mushroom body calyx in Brachycera Orthorrhapha flies is extremely diverse in the degree of development. In general, the calyx has the anterior, posterior, and dorsal lobes, as well as “sleeves” of glomerular neuropil surrounding Kenyon cell fibers. The anterior lobe of the calyx is found in all species studied. The most complex structure of the calyx is characteristic of the families Empididae and especially Bombyliidae, in which it has all the parts listed above. Brachycera Orthorrhapha flies have three fiber bundles of Kenyon cells, in contrast to four bundles in Drosophila. It is assumed that each mushroom body in Brachycera Orthorrhapha flies is formed by descendants of three single neuroblasts.     

Tropical Asian species show that the Old World clade of ‘spiny solanums’ (Solanum subgenus Leptostemonum pro parte: Solanaceae) is not monophyletic

The tropical Asian taxa of the species‐rich genus Solanum (Solanaceae) have been less well studied than their highly diverse New World relatives. Most of these tropical Asian species, including the cultivated brinjal eggplant/aubergine and its wild progenitor, are part of the largest monophyletic Solanum lineage, the ‘spiny solanums’ (subgenus Leptostemonum or the Leptostemonum clade). Here we present the first phylogenetic analysis of spiny solanums that includes broad sampling of the tropical Asian species, with 42 of the 56 currently recognized species represented. Two nuclear and three plastid regions [internal transcribed spacer (ITS), waxy, ndhF‐rpL32, trnS‐trnG and trnT‐trnF] were amplified and used to reconstruct phylogenetic relationships using maximum likelihood and Bayesian methods. Our analyses show that Old World spiny solanums do not resolve in a single clade, but are part of three unrelated lineages, suggesting at least three independent introductions from the New World. We identify and describe several monophyletic groups in Old World solanums that have not been previously recognized. Some of these lineages are coherent in terms of morphology and geography, whereas others show considerable morphological variation and enigmatic distribution patterns. Tropical Asia occupies a key position in the biogeography of Old World spiny solanums, with tropical Asian taxa resolved as the closest relatives of diverse groups of species from Australia and Africa.     

Molecular phylogeny of the horse flies: a framework for renewing tabanid taxonomy

Horse flies, family Tabanidae, are the most diverse family‐level clade of bloodsucking insects, but their phylogeny has never been thoroughly explored using molecular data. Most adult female Tabanidae feed on nectar and on the blood of various mammals. Traditional horse fly classification tends towards large heterogeneous taxa, which impede much‐needed taxonomic work. To guide renewed efforts in the systematics of horse flies and their relatives, we assembled a dataset of 110 exemplar species using nucleotide data from four genes—mitochondrial CO1, and nuclear 28S, CAD and AATS. All commonly recognized tribes in Tabanidae are represented, along with outgroups in Tabanomorpha. The phylogeny is reconstructed using Bayesian inference, and divergence times are estimated using Bayesian relaxed clock methods with time constraints from tabanid fossils. Our results show Athericidae strongly supported as the lineage most closely related to Tabanidae, and Pangoniinae and Tabaninae as monophyletic lineages. However, Chrysopsinae is nonmonophyletic, with strong support for both a nonmonophyletic Bouvieromyiini and for Rhinomyzini as sister to Tabaninae. Only the tribes Philolichini, Chrysopsini, Rhinomyzini and Haematopotini are recovered as monophyletic, although Scionini is monophyletic with exclusion of the peculiar genus Goniops Aldrich. Mycteromyia Philippi and Adersia Austen, two enigmatic genera sometimes placed in separate family‐level groups, are recovered inside Pangoniini and Chrysopsini, respectively. Several species‐rich genera are not recovered as monophyletic, including Esenbeckia Rondani, Silvius Meigen, Dasybasis Macquart and Tabanus L. Tabanidae likely originated in the Cretaceous, and all major extant groups were present by the early Palaeogene. This newly revised phylogenetic framework for Tabanidae forms the basis for a new assessment of tabanid diversification and provides context for understanding the evolution of trophic specialization in horse flies.     

The evolutionary pattern of host use in the Bombyliidae (Diptera): a diverse family of parasitoid flies

The larval host associations and mode of parasitism of Bombyliidae (bee flies) are summarized and analysed within an evolutionary framework. We discuss difficulties in extracting information from the (almost 1000) host records, noting that most observations are made by chance, often imprecise, and distributed unevenly across bombyliid taxa. These caveats aside, the vast majority of Bombyliidae are ectoparasitoid; endoparasitoids are known in only three tribes belonging to two distandy related subfamilies, the Toxophorinae (Gerontini and Systropodini) and Anthracinae (Villini). The recorded host range of Bombyliidae spans seven insect Orders and the Araneae; almost half of all records are from bees and wasps (Hymenoptera). No Bombyliidae have evolved structures to inject eggs directly into the host as is the case in many hymenopterous parasitoids. Bombyliid larvae usually exhibit hyper-metamorphosis, and contact their host while it is in the larval stage. Bee fly larvae consume the host when it is in a quiescent stage such as the mature larva, prepupa or pupa. Records of hyperparasitism by Bombyliidae are uncommon, most occurring in genera of the Anthracinae. All bombyliids recorded as hyperparasitoids do not appear to have evolved in any close association with the primary host, and are best termed pseudohyperparasitoids. Both facultative and obligate pseudohyperparasitism has been recorded. Bombyliidae are difficult to place in the koinobiont/idiobiont classification used most extensively in Hymenoptera but they share most features of koinobionts. Provision-directed cleptoparasitism has been recorded in one genus. We propose an evolutionary scenario progressing from an ancestral substrate-zone free-living predator to ectoparasitoid, a broadening of host range to include the consumption of orthopteran egg pods, and the independent development of endoparasitism in two lineages. The suggestion that host range narrows as the intimacy of encounter between female parasitoid and host increases is supported in the Bombyliidae. Amongst the basal subfamilies which are parasitoids, host range is narrowest in the Toxophorinae. In the more derived subfamilies host range is generally broad, and is dictated by ecological context rather than host phylogeny. Bombyliidae violate the prediction of increased species richness in parasitic groups, and the broad host range of most bee flies is a possible explanation.     

Evolution of fossil and living spider flies based on morphological and molecular data (Diptera,Acroceridae)

The phylogeny of spider flies is presented based on an analysis of DNA sequence data combined with morphological characters for both living and fossil species. We sampled 40 extant and extinct genera across all major lineages of Acroceridae, which were compared with outgroup taxa from various lower brachyceran families. In all, 81 morphological characters of 60 extant and 10 extinct ingroup species were combined with 7.1 kb of DNA sequences of two nuclear (CAD and 28S rDNA) and two mitochondrial genes (COI and 16S rDNA). Results strongly support the monophyly of Acroceridae, with major clades contained within classified here in five extant subfamilies (Acrocerinae, Cyrtinae stat. rev. , Ogcodinae stat. rev. , Panopinae and Philopotinae) and one extinct subfamily, Archocyrtinae. The evolution of important spider fly traits is discussed, including genitalia and wing venation. The status of the enigmatic Psilodera Gray and Pterodontia Gray as members of the Panopinae is confirmed based on both molecular and morphological data.     

The phylogenetic relationships among infraorders and superfamilies of Diptera based on morphological evidence

Members of the megadiverse insect order Diptera (flies) have successfully colonized all continents and nearly all habitats. There are more than 154 000 described fly species, representing 10–12% of animal species. Elucidating the phylogenetic relationships of such a large component of global biodiversity is challenging, but significant advances have been made in the last few decades. Since Hennig first discussed the monophyly of major groupings, Diptera has attracted much study, but most researchers have used non‐numerical qualitative methods to assess morphological data. More recently, quantitative phylogenetic methods have been used on both morphological and molecular data. All previous quantitative morphological studies addressed narrower phylogenetic problems, often below the suborder or infraorder level. Here we present the first numerical analysis of phylogenetic relationships of the entire order using a comprehensive morphological character matrix. We scored 371 external and internal morphological characters from larvae, pupae and adults for 42 species, representing all infraorders selected from 42 families. Almost all characters were obtained from previous studies but required revision for this ordinal‐level study, with homology assessed beyond their original formulation and across all infraorders. We found significant support for many major clades (including the Diptera, Culicomorpha, Bibionomorpha, Brachycera, Eremoneura, Cyclorrhapha, Schizophora, Calyptratae and Oestroidea) and we summarize the character evidence for these groups. We found low levels of support for relationships between the infraorders of lower Diptera, lower Brachycera and major lineages of lower Cyclorrhapha, and this is consistent with findings from molecular studies. These poorly supported areas of the tree may be due to periods of rapid radiation that left few synapomorphies in surviving lineages.     

Molecular phylogeny of the Calyptratae (Diptera: Cyclorrhapha) with an emphasis on the superfamily Oestroidea and the position of Mystacinobiidae and McAlpine's fly

The dipteran clade Calyptratae is comprised of approximately 18 000 described species (12% of the known dipteran diversity) and includes well‐known taxa such as houseflies, tsetse flies, blowflies and botflies, which have a close association with humans. However, the phylogenetic relationships within this insect radiation are very poorly understood and controversial. Here we propose a higher‐level phylogenetic hypothesis for the Calyptratae based on an extensive DNA sequence dataset for 11 noncalyptrate outgroups and 247 calyptrate species representing all commonly accepted families in the Oestroidea and Hippoboscoidea, as well as those of the muscoid grade. DNA sequences for genes in the mitochondrial (12S, 16S, cytochrome c oxidase subunit I and cytochrome b) and nuclear genome [18S, 28S, the carbamoyl phosphate synthetase region of CAD (rudimentary), Elongation factor one alpha] were used to reconstruct the relationships. We discuss problems relating to the alignment and analysis of large datasets and emphasize the advantages of utilizing a guide tree‐based approach for the alignment of the DNA sequences and using the leaf stability index to identify ‘wildcard’ taxa whose excessive instability obscures the phylogenetic signal. Our analyses support the monophyly of the Calyptratae and demonstrate that the superfamily Oestroidea is nested within the muscoid grade. We confirm that the monotypic family Mystacinobiidae is an oestroid and further revise the composition of the Oestroidea by demonstrating that the previously unplaced and still undescribed ‘McAlpine’s fly’ is nested within this superfamily as a probable sister group to Mystacinobiidae. Within the Oestroidea we confirm with molecular data that the Calliphoridae are a paraphyletic grade of lineages. The families Sarcophagidae and Rhiniidae are monophyletic, but support for the monophyly of Tachinidae and Rhinophoridae depends on analytical technique (e.g. parsimony or maximum likelihood). The superfamilies Hippoboscoidea and Oestroidea are consistently found to be monophyletic, and the paraphyly of the muscoid grade is confirmed. In the overall relationships for the calyptrates, the Hippoboscoidea are sister group to the remaining Calyptratae, and the Fanniidae are sister group to the nonhippoboscoid calyptrates, whose relationships can be summarized as (Muscidae (Oestroidea (Scathophagidae, Anthomyiidae))).     

Genetic differentiation associated with host plants and geography among six widespread species of South American Blepharoneura fruit flies (Tephritidae)

Tropical herbivorous insects are astonishingly diverse, and many are highly host‐specific. Much evidence suggests that herbivorous insect diversity is a function of host plant diversity; yet, the diversity of some lineages exceeds the diversity of plants. Although most species of herbivorous fruit flies in the Neotropical genus Blepharoneura are strongly host‐specific (they deposit their eggs in a single host plant species and flower sex), some species are collected from multiple hosts or flowers and these may represent examples of lineages that are diversifying via changes in host use. Here, we investigate patterns of diversification within six geographically widespread Blepharoneura species that have been collected and reared from at least two host plant species or host plant parts. We use microsatellites to (1) test for evidence of local genetic differentiation associated with different sympatric hosts (different plant species or flower sexes) and (2) examine geographic patterns of genetic differentiation across multiple South American collection sites. In four of the six fly species, we find evidence of local genetic differences between flies collected from different hosts. All six species show evidence of geographic structure, with consistent differences between flies collected in the Guiana Shield and flies collected in Amazonia. Continent‐wide analyses reveal – in all but one instance – that genetically differentiated flies collected in sympatry from different host species or different sex flowers are not one another's closest relatives, indicating that genetic differences often arise in allopatry before, or at least coincident with, the evolution of novel host use.     

Phylogeny of the festucoid grasses of subtribe Loliinae and allies (Poeae, Pooideae) inferred from ITS and trnL-F sequences

Analyses of ribosomal ITS and chloroplast trnL-F sequences provide phylogenetic reconstruction for the festucoids (Poeae: Loliinae), a group of temperate grasses with morphological and molecular affinities to the large genus Festuca. Parsimony and Bayesian analyses of the combined ITS/trnL-F dataset show Loliinae to be monophyletic but unresolved for a weakly supported clade of 'broad-leaved Festuca,' a well-supported clade of 'fine-leaved Festuca,' and Castellia. The first group includes subgenera Schenodorus, Drymanthele, Leucopoa, and Subulatae, and sections Subbulbosae, Scariosa, and Pseudoscariosa of Festuca, plus Lolium and Micropyropsis. The second group includes sections Festuca, Aulaxyper, Eskia, and Amphigenes of Festuca, plus Vulpia, Ctenopsis, Psilurus, Wangenheimia, Cutandia, Narduroides, and Micropyrum. Subtribes Dactylidinae and Cynosurinae/Parapholiinae are sister clades and are the closest relatives of Loliinae. Vulpia is polyphyletic within the 'fine-leaved' fescues as revealed by the two genome analyses. Lolium is resolved as monophyletic in the ITS and combined analyses, but unresolved in the trnL-F based tree. Conflict between the ITS and the trnL-F trees in the placement of several taxa suggests the possibility of past reticulation events, although lineage sorting and possible ITS paralogy cannot be ruled out.     

Evolution and phylogenetic utility of CAD (rudimentary) among Mesozoic-aged Eremoneuran Diptera (Insecta)

We sequenced nearly the entire carbomoylphosphate synthase (CPS) domain of CAD, or rudimentary, (ca. 4 kb) from 29 species of flies representing all major clades within Eremoneura, or higher flies, and several orthorrhaphous brachyceran outgroups. We compared these sequences with orthologs from Anopheles gambiae and Drosophila melanogaster to assess structure, compositional bias, and phylogenetic utility. CAD is large (6.6+ kb), complex (comprised of three major and myriad minor functional domains) and relatively free of introns, extreme nucleotide bias (except third codon positions), and large hypervariable regions. The CPS domain possesses moderate levels of nonsynonymous divergence among taxa of intermediate evolutionary age and conveys considerable phylogenetic signal. Phylogenetic analysis of CPS sequences under varying methods and assumptions resulted in well-resolved, strongly supported trees concordant with many traditional ideas about higher dipteran phylogeny and with prior inferences from 28S rDNA. The most robustly supported major eremoneuran clades were Cyclorrhapha, Platypezoidea, Eumuscomorpha, Empidoidea, Atelestidae, Empidoidea exclusive of Atelestidae, Hybotidae s.l., Microphoridae+Dolichopodidae, and Empididae s. str. Because CAD is ubiquitous, apparently single copy (at least within holometabolous insects), readily obtained from several insect orders using primers described herein, and exhibits considerable phylogenetic utility, it should have wide applicability in insect molecular systematics.     

Long‐proboscid brachyceran flies in Cretaceous amber (Diptera: Stratiomyomorpha: Zhangsolvidae)

The monophyletic family Zhangsolvidae comprises stout‐bodied brachyceran flies with a long proboscis and occurring only in the Cretaceous, originally known in shale from the Early Cretaceous Laiyang Formation (Fm.) in China (Zhangsolva Nagatomi & Yang), subsequently from limestones of the Early Cretaceous Crato Fm. of Brazil. Cratomyoides Wilkommen is synonymized with Cratomyia Mazzarolo & Amorim, both from the Crato Fm.; Cratomyiidae is synonymized with Zhangsolvidae. Two genera and three species of Zhangsolvidae are described: Buccinatormyia magnifica Arillo, Peñalver & Pérez‐de la Fuente, gen. et sp.n. and B. soplaensis Arillo, Peñalver & Pérez‐de la Fuente, sp.n. , in Albian amber from Las Peñosas Fm. in Spain; and Linguatormyia teletacta Grimaldi, gen. et sp.n. , in Upper Albian–Lower Cenomanian amber from Hukawng Valley in Myanmar. Buccinatormyia soplaensis and Linguatormyia teletacta are unique among all Brachycera, extant or extinct, by their remarkably long, flagellate antennae, about 1.6× the body length in the latter species. A phylogenetic analysis of 52 morphological characters for 35 taxa is presented, 11 taxa being Cretaceous species, which supports placement of the family within Stratiomyomorpha, although not to any particular family within the infraorder. This published work has been registered in Zoobank, http://zoobank.org/urn:lsid:zoobank.org:pub:F32CF887‐7C37‐45D5‐BD6B‐135FE9B729A7 .     

The backbone of the post-synaptic density originated in a unicellular ancestor of choanoflagellates and metazoans

Background  

Comparative genomics of the early diverging metazoan lineages and of their unicellular sister-groups opens new window to reconstructing the genetic changes which preceded or accompanied the evolution of multicellular body plans. A recent analysis found that the genome of the nerve-less sponges encodes the homologues of most vertebrate post-synaptic proteins. In vertebrate excitatory synapses, these proteins assemble to form the post-synaptic density, a complex molecular platform linking membrane receptors, components of their signalling pathways, and the cytoskeleton. Newly available genomes from Monosiga brevicollis (a member of Choanoflagellata, the closest unicellular relatives of animals) and Trichoplax adhaerens (a member of Placozoa: besides sponges, the only nerve-less metazoans) offer an opportunity to refine our understanding of post-synaptic protein evolution.     

Phylogenetic relationships of annelids,molluscs, and arthropods evidenced from molecules and morphology

Annelids and arthropods have long been considered each other's closest relatives, as evidenced by similarities in their segmented body plans. An alternative view, more recently advocated by investigators who have examined partial 18S ribosomal RNA data, proposes that annelids, molluscs, and certain other minor phyla with trochophore larva stages share a more recent common ancestor with one another than any do with arthropods. The two hypotheses are mutually exclusive in explaining spiralian relationships. Cladistic analysis of morphological data does not reveal phylogentic relationships among major spiralian taxa but does suggest monophyly for both the annelids and molluscs. Distance and maximum-likelihood analyses of 18S rRNA gene sequences from major spiralian taxa suggest a sister relationship between annelids and molluscs and provide a clear resolution within the major groups of the spiralians. The parsimonious tree based on molecular data, however, indicates a sister relationship of the Annelida and Bivalvia, and an earlier divergence of the Gastropoda than the Annelida–Bivalvia clade. To test further hypotheses on the phylogenetic relationships among annelids, molluscs, and arthropods, and the ingroup relationships within the major spiralian taxa, we combine the molecular and morphological data sets and subject the combined data matrix to parsimony analysis. The resulting tree suggests that the molluscs and annelids form a monophyletic lineage and unites the molluscan taxa to a monophyletic group. Therefore, the result supports the Eutrochozoa hypothesis and the monophyly of molluscs, and indicates early acquisition of segmented body plans in arthropods. Received: 25 September 1995 / Accepted: 15 March 1996     

Molecules, Morphology, Fossils, and the Relationship of Angiosperms and Gnetales

Morphological analyses of seed plant phylogeny agree that Gnetales are the closest living relatives of angiosperms, but some studies indicate that both groups are monophyletic, while others indicate that angiosperms are nested within Gnetales. Molecular analyses of several genes agree that both groups are monophyletic, but differ on whether they are related. Conflicts among morphological trees depend on the interpretation of certain characters; when these are analyzed critically, both groups are found to be monophyletic. Conflicts among molecular trees may reflect the rapid Paleozoic radiation of seed plant lines, aggravated by the long branches leading to extant taxa. Trees in which angiosperms are not related to Gnetales conflict more with the stratigraphic record. Even if molecular data resolve the relationships among living seed plant groups, understanding of the origin of angiosperm organs will require integration of fossil taxa, necessarily using morphology.     

The contribution of multiple barriers to reproduction between edaphically divergent lineages in the Amazonian tree Protium subserratum (Burseraceae)

Disentangling the strength and importance of barriers to reproduction that arise between diverging lineages is central to our understanding of species origin and maintenance. To date, the vast majority of studies investigating the importance of different barriers to reproduction in plants have focused on short‐lived temperate taxa while studies of reproductive isolation in trees and tropical taxa are rare. Here, we systematically examine multiple barriers to reproduction in an Amazonian tree, Protium subserratum (Burseraceae) with diverging lineages of soil specialist ecotypes. Using observational, molecular, distributional, and experimental data, we aimed to quantify the contributions of individual prezygotic and postzygotic barriers including ecogeographic isolation, flowering phenology, pollinator assemblage, pollen adhesion, pollen germination, pollen tube growth, seed development, and hybrid fitness to total reproductive isolation between the ecotypes. We were able to identify five potential barriers to reproduction including ecogeographic isolation, phenological differences, differences in pollinator assemblages, differential pollen adhesion, and low levels of hybrid seed development. We demonstrate that ecogeographic isolation is a strong and that a combination of intrinsic and extrinsic prezygotic and postzygotic barriers may be acting to maintain near complete reproductive isolation between edaphically divergent populations of the tropical tree, P. subserratum.     

Phylogeographic structure in the chromosomally polymorphic rodent Cricetulus barabensis sensu lato (Mammalia,Cricetidae)

Striped hamsters (Cricetulus barabensis sensu lato) represent a complex of chromosomally distinct allopatric lineages/taxa of either species or subspecies rank. They are widely distributed across the steppes of eastern and central Palearctic. Phylogenetic analysis of cytochrome b gene sequences based on 496 specimens from 112 localities revealed five well‐supported lineages divergent at 2%–4%. Two of them correspond to “griseus” (2n = 22) and “pseudogriseus” (2n = 24) karyomorphs and are placed as sister taxa. The “barabensis” (2n = 20) karyomorph is represented by three other branches and appears non‐monophyletic. All mtDNA lineages are distributed allopatrically or parapatrically; no indications of gene flow between populations of different chromosomal races were found. The results of the molecular clock analysis suggest that the main lineages diverged in the late Middle Pleistocene. The inferred evolutionary scenario implies that the common ancestor of the recent lineages belonged to the 2n = 20 karyomorph and originated in the eastern part of the contemporary range.     

Phylogenetic position of the acariform mites: sensitivity to homology assessment under total evidence

Background  

Mites (Acari) have traditionally been treated as monophyletic, albeit composed of two major lineages: Acariformes and Parasitiformes. Yet recent studies based on morphology, molecular data, or combinations thereof, have increasingly drawn their monophyly into question. Furthermore, the usually basal (molecular) position of one or both mite lineages among the chelicerates is in conflict to their morphology, and to the widely accepted view that mites are close relatives of Ricinulei.