Molecular phylogeny of sea snakes reveals a rapidly diverged adaptive radiation

Evolutionary relationships within and between the marine hydrophiine sea snake groups have been inferred primarily using morphological characters, and two major groups traditionally are recognized. The Aipysurus group comprises nine species in two genera, and the taxonomically chaotic Hydrophis group comprises as many as 40 species, of which 27 are generally allocated to the genus Hydrophis and 13 to ten additional genera. In addition to these two major groups are three putatively ‘primitive’ monotypic genera, Hydrelaps darwiniensis, Ephalophis greyi and Parahydrophis mertoni. The present study investigated the evolutionary relationships of 23 representative species of marine hydrophiines, comprising 15 species from the Hydrophis group, six species from the Aipysurus group, and H. darwiniensis and P. mertoni, to address two broad aims. First, the aim was to provide a robust phylogeny for sea snakes to test previous phylogenetic hypotheses based on morphology, and thus provide some taxonomic stability to the group. Second, there was interest in evaluating the hypothesis that the Hydrophis group might represent a rapidly diverged adaptive radiation. A large mitochondrial DNA data set based on the cytochrome b gene (1080 bp, 401 parsimony informative) and the 16S rRNA gene (510 bp, 57 parsimony informative) was assembled and these data were analysed using parsimony, maximum‐likelihood and Bayesian approaches. All analyses yielded virtually the same optimal tree, confirming that hydrophiine sea snakes comprise at least three lineages. The Aipysurus group formed a strongly supported and well‐resolved monophyletic clade. The Hydrophis group also formed a strongly supported clade; however, resolution among the genera and species was very poor. Hydrelaps darwiniensis and P. mertoni formed a sister clade to the Hydrophis lineage. Our phylogeny was used to test the validity of previous taxonomic and phylogenetic hypotheses, and to demonstrate that the genus Hydrophis is not monophyletic. Genetic diversity relative to phenotypic diversity is four to seven times greater in the Hydrophis lineage compared with the Aipysurus lineage. The topology of our phylogenetic hypothesis, combined with the levels of genetic divergence relative to morphological diversity, demonstrate that the Hydrophis lineage represents a rapidly diverged adaptive radiation. The data are consistent with the hypothesis that this adaptive radiation may be due to historical sea level fluctuations that have isolated populations and promoted speciation. © 2006 The Linnean Society of London, Biological Journal of the Linnean Society, 2006, 89 , 523–539.     

Multilocus phylogeny and a new classification for Southeast Asian and Melanesian forest frogs (family Ceratobatrachidae)

We present a near comprehensive, densely sampled, multilocus phylogenetic estimate of species relationships within the anuran family Ceratobatrachidae, a morphologically and ecologically diverse group of frogs from the island archipelagos of Southeast Asia and the South‐West Pacific. Ceratobatrachid frogs consist of three clades: a small clade of enigmatic, primarily high‐elevation, semi‐aquatic Sundaland species currently assigned to Ingerana (for which we erect a new genus), which is the sister taxon of two large, monophyletic radiations, each situated on islands on either side of Wallace's Line. One radiation is composed of Philippine species of Platymantis and the other contains all taxa from the eastern Indonesian, New Guinean, Solomon, Bismarck, and Fijian archipelagos. Several additional genera (Batrachylodes, Discodeles, Ceratobatrachus, and Palmatorappia) are nested within Platymantis, and of these Batrachylodes and Discodeles are nonmonophyletic. To address the widespread paraphyly of the genus Platymantis and several additional nomenclatural issues, we undertook a wholesale nomenclatural reorganization of the family. Given our partially unresolved phylogeny, and in order to impart a conservative, stable taxonomy, involving a minimal number of genus‐species couplet changes, we propose a conservative classification representing a few compromises. These changes are designed to preserve maximally the presumed original intent of taxonomy (widely used group names associated with morphological and ecological diversity of particular species or groups of species) while implementing a hierarchical system that is consistent with the estimate of phylogeny based on new molecular data. © 2015 The Linnean Society of London     

Did geckos ride the Palawan raft to the Philippines?

Aim We examine the genetic diversity within the lizard genus Gekko in the Philippine islands to understand the role of geography and geological history in shaping species diversity in this group. We test multiple biogeographical hypotheses of species relationships, including the recently proposed Palawan Ark Hypothesis. Location Southeast Asia and the Philippines. Methods Samples of all island endemic and widespread Philippine Gekko species were collected and sequenced for one mitochondrial gene (NADH dehydrogenase subunit 2) and one nuclear gene (phosducin). We used maximum likelihood and Bayesian phylogenetic methods to derive the phylogeny. Divergence time analyses were used to estimate the time tree of Philippine Gekko in order to test biogeographical predictions of species relationships. The phylogenetic trees from the posterior distribution of the Bayesian analyses were used for testing biogeographical hypotheses. Haplotype networks were created for the widespread species Gekko mindorensis to explore genetic variation within recently divergent clades. Results Both maximum likelihood and Bayesian phylogenetic analyses indicated that Philippine Gekko species are a diverse clade with a long history in the archipelago. Ancestral range reconstruction and divergence time analyses suggest a Palawan microcontinental origin for this clade, coinciding with Palawan’s separation from Asia beginning 30 Ma, with subsequent diversification in the oceanic Philippine islands. The widespread species G. mindorensis and G. monarchus diversified in the late Miocene/early Pliocene and are potentially complexes of numerous undescribed species. Main conclusions The view of the Philippine islands as a ‘fringing archipelago’ does not explain the pattern of species diversity in the genus Gekko. Philippine Gekko species have diversified within the archipelago over millions of years of isolation, forming a large diverse group of endemic species. Furthermore, the Philippine radiation of gekkonid lizards demonstrates biogeographical patterns most consistent with stochastic colonization followed by in situ diversification. Our results reveal the need to consider deeper time geological processes and their potential role in the evolution of some Philippine terrestrial organisms.     

Molecular phylogeny of the Forcipulatacea (Asteroidea: Echinodermata): systematics and biogeography

We present a comprehensively sampled three‐gene phylogeny of the monophyletic Forcipulatacea, one of three major lineages within the crown‐group Asteroidea. We present substantially more Southern Hemisphere and deep‐sea taxa than were sampled in previous molecular studies of this group. Morphologically distinct groups, such as the Brisingida and the Zoroasteridae, are upheld as monophyletic. Brisingida is supported as the derived sister group to the Asteriidae (restricted), rather than as a basal taxon. The Asteriidae is paraphyletic, and is broken up into the Stichasteridae and four primary asteriid clades: (1) a highly diverse boreal clade, containing members from the Arctic and sub‐Arctic in the Northern Hemisphere; (2) the genus Sclerasterias; (3) and (4) two sister clades that contain asteriids from the Antarctic and pantropical regions. The Stichasteridae, which was regarded as a synonym of the Asteriidae, is resurrected by our results, and represents the most diverse Southern Hemisphere forcipulatacean clade (although two deep‐sea stichasterid genera occur in the Northern Hemisphere). The Labidiasteridae is artificial, and should be synonymized into the Heliasteridae. The Pedicellasteridae is paraphyletic, with three separate clades containing pedicellasterid taxa emerging among the basal Forcipulatacea. Fossils and timing estimates from species‐level phylogeographic studies are consistent with prior phylogenetic hypotheses for the Forcipulatacea, suggesting diversification of basal taxa in the early Mesozoic, with some evidence for more widely distributed ranges from Cretacous taxa. Our analysis suggests a hypothesis of an older fauna present in the Antarctic during the Eocene, which was succeeded by a modern Antarctic fauna that is represented by the recently derived Antarctic Asteriidae and other forcipulatacean lineages. © 2011 The Linnean Society of London, Zoological Journal of the Linnean Society, 2011, 162 , 646–660.     

Molecular systematics of flyingfishes (Teleostei: Exocoetidae): evolution in the epipelagic zone

The flyingfish family Exocoetidae is a diverse group of marine fishes that are widespread and abundant in tropical and subtropical seas. Flyingfishes are epipelagic specialists that are easily distinguished by their enlarged fins, which are used for gliding leaps over the surface of the water. Although phylogenetic hypotheses have been proposed for flyingfish genera based on morphology, no comprehensive molecular studies have been performed. In the present study, we describe a species‐level molecular phylogeny for the family Exocoetidae, based on data from the mitochondrial cytochrome b gene (1137 bp) and the nuclear RAG2 gene (882 bp). We find strong support for previous morphology‐based phylogenetic hypotheses, as well as the monophyly of most currently accepted flyingfish genera. However, the most diverse genus Cheilopogon is not monophyletic. Using our novel flyingfish topology, we examine previously proposed hypotheses for the origin and evolution of gliding. The results support the progressive transition from two‐wing to four‐wing gliding. We also use phylogenetic approaches to test the macroecological effects of two life history characters (e.g. egg buoyancy and habitat) on species range size in flyingfishes. © 2010 The Linnean Society of London, Biological Journal of the Linnean Society, 2011, 102, 161–174.     

Molecular systematics of peppermint and cleaner shrimps: phylogeny and taxonomy of the genera Lysmata and Exhippolysmata (Crustacea: Caridea: Hippolytidae)

Shrimps from the ecologically diverse genera Lysmata and Exhippolysmata are rare among marine invertebrates because they are protandric simultaneous hermaphrodites: shrimps initially mature and reproduce solely as males, and later in life become functional simultaneous hermaphrodites. Considerable progress on the reproductive ecology of members from these two genera has been achieved during the last decade. However, several outstanding issues of systematic nature remain to be addressed. Here, a molecular phylogeny of these two genera was used to examine the overall evolutionary relationship within and between species and genera, and to answer various questions related to the systematic status of several species. The present phylogenetic analysis, including 53 sequences and 26 species of Lysmata and Exhippolysmata, indicates that semiterrestrial shrimps from the genus Merguia represent the sister group to a second natural clade composed by shrimps from the genera Lysmata and Exhippolysmata. Also, the phylogenetic analysis confirmed that the genus Lysmata is paraphyletic, and includes the genus Exhippolysmata, as noted in a preliminary study. The tree partially supports the separation of species with or without a developed accessory branch into two different genera or subgenera (i.e. Lysmata and Hippolysmata having a well‐developed accessory branch, or not, respectively). The genetic distance between the cleaner shrimps Lysmata amboinensis and Lysmata grabhami was smaller than has been observed between other sister species. On the other hand, the topology of the tree indicates that these two entities are reciprocally monophyletic. Thus, this latter result, together with minor but constant differences in the colour pattern reported for these two entities, indicates that there is no reason to stop treating them as different valid species. This study enabled the long overdue resolution of standing taxonomic questions in shrimps from the genera Lysmata and Exhippolysmata. In the future, this phylogeny will help to reveal the conditions favouring the origins of several behavioural and morphological novelties in these unique shrimps. © 2010 The Linnean Society of London, Zoological Journal of the Linnean Society, 2010, 160 , 254–265.     

Patterns of morphological evolution of the cephalic region in damselfishes (Perciformes: Pomacentridae) of the Eastern Pacific

Pomacentridae are one of the most abundant fish families inhabiting reefs of tropical and temperate regions. This family, comprising 29 genera, shows a remarkable diversity of habitat preferences, feeding, and behaviours. Twenty‐four species belonging to seven genera have been reported in the Eastern Pacific region. The present study focuses on the relationship between the diet and the cephalic profile in the 24 endemic damselfishes of this region. Feeding habits were determined by means of underwater observations and the gathering of bibliographic data. Variations in cephalic profile were analyzed by means of geometric morphometrics and phylogenetic methods. The present study shows that the 24 species can be grouped into three main trophic guilds: zooplanktivores, algivores, and an intermediate group feeding on small pelagic and benthic preys. Shape variations were low within each genus except for Abudefduf. Phylogenetically adjusted regression reveals that head shape can be explained by differences in feeding habits. The morphometric phylogeny recovered the subfamily Stegastinae and the relationship between Abudefduf troschelii and Chromis species. The cephalic profile of damselfishes contains a clear and strong phylogenetic signal. © 2011 The Linnean Society of London, Biological Journal of the Linnean Society, 2011, 102 , 593–613.     

Unravelling a tangle of Mexican serpents: a systematic revision of highland pitvipers

As most recently recognized, the name Cerrophidion barbouri Dunn, 1919, refers to a highland species of pitviper endemic to Guerrero, Mexico, of which Agkistrodon browni Shreve, 1938, is considered a junior synonym. This species is rarely collected and prior to recent decades it was known from only a few specimens. A careful re‐examination of nearly all known specimens of C. barbouri and the type series of A. browni reveals that both names represent valid species and we therefore resurrect A. browni. Both species are extremely variable with respect to cephalic scalation and colour pattern, which has previously confounded efforts to identify them. We provide phylogenetic analyses using both Bayesian and maximum parsimony criteria of New World pitvipers to investigate the phylogenetic position of A. browni and C. barbouri. Our phylogenetic tree, based on 2235 bp of mitochondrial data [12S, 16S, cytochrome b (cyt b), NADH dehydrogenase subunit 4 (ND4)], strongly supports a clade consisting of A. browni, C. barbouri, and Ophryacus melanurus, which has a distant sister relationship to Ophryacus undulatus. Based on the deep phylogenetic divergences amongst these species and distinctive morphology we recommend that a new genus be recognized for A. browni, C. barbouri, and O. melanurus. Finally, we revise the genera Cerrophidion and Ophryacus in accordance with our new classification. © 2011 The Linnean Society of London, Zoological Journal of the Linnean Society, 2011, 163 , 943–958.     

Phylogenetics and morphological evolution of coral‐dwelling barnacles (Balanomorpha: Pyrgomatidae)

Pyrgomatid barnacles are a family of balanomorphs uniquely adapted to symbiosis on corals. The evolution of the coral‐dwelling barnacles is explored using a multi‐gene phylogeny (COI, 16S, 12S, 18S, and H3) and phenotypic trait‐mapping. We found that the hydrocoral associate Wanella should be excluded, while some archaeobalanids in the genus Armatobalanus should be included in the Pyrgomatidae. Three well supported clades were recovered: clade I is the largest group and is exclusively Indo‐West Pacific, clade II contains two plesiomorphic Indo‐West Pacific genera, while clade III is comprised of East and West Atlantic taxa. Some genera did not form reciprocally monophyletic groups, while the genus Trevathana was found to be paraphyletic and to include members of three other apomorphic genera/tribes. The highly unusual coral‐parasitic hoekiines appear to be of recent origin and rapidly evolving from Trevathana sensu lato. Pyrgomatids include six‐, four‐, and one‐plated forms, and exhibit convergent evolutionary tendencies towards skeletal reduction and fusion, loss of cirral armature, and increased host specificity. © 2014 The Linnean Society of London, Biological Journal of the Linnean Society, 2014, 113 , 162–179.     

Complete mitochondrial genome sequence and phylogenetic position of the Amu Darya sturgeon,Pseudoscaphirhynchus kaufmanni (Acipenseriformes: Acipenseridae)

In this study, we successfully assembled the complete mitochondrial genome of the Amu Darya sturgeon Pseudoscaphirhynchus kaufmanni. Based on this mitochondrial genome and previously published mitochondrial genomes of members of the Acipenseridae family, we assessed the phylogenetic position of P. kaufmanni using maximum likelihood and Bayesian inference for phylogeny reconstruction. The resultant phylogenetic trees were well-resolved, with congruence between different phylogenetic methods. This robust phylogenetic analysis elucidated the relationship among the four acipenserid genera and strongly supported the division of the family into three main clades. Evaluation of molecular phylogeny using maximum likelihood and Bayesian analysis led to the following conclusions: (a) the most basal position within the Acipenseridae remains in the clade containing Acipenser oxyrinchus and Acipenser sturio; (b) the genus Scaphirhynchus belongs to the Atlantic clade and is a sister group of the remaining species of the clade; and (c) the close relationship between P. kaufmanni and Acipenser stellatus is well supported.     

Molecular phylogeny of hinge‐beak shrimps (Decapoda: Caridea: Rhynchocinetes and Cinetorhynchus) and allies: a formal test of familiar and generic monophyly using a multilocus phylogeny

The Rhynchocinetidae (‘hinge‐beak’ shrimps) is a family of marine caridean decapods with considerable variation in sexual dimorphism, male weaponry, mating tactics, and sexual systems. Thus, this group is an excellent model with which to analyse the evolution of these important characteristics, which are of interest not only in shrimps specifically but also in animal taxa in general. Yet, there exists no phylogenetic hypothesis, either molecular or morphological, for this taxon against which to test either the evolution of behavioural traits within the Rhynchocinetidae or its genealogical relationships with other caridean taxa. In this study, we tested (1) hypotheses on the phylogenetic relationships of rhynchocinetid shrimps, and (2) the efficacy of different (one‐, two‐, and three‐phase) methods to generate a reliable phylogeny. Total genomic DNA was extracted from tissue samples taken from 17 species of Rhynchocinetidae and five other species currently or previously assigned to the same superfamily (Nematocarcinoidea); six species from other superfamilies were used as outgroups. Sequences from two nuclear genes (H3 and Enolase) and one mitochondrial gene (12S) were used to construct phylogenies. One‐phase phylogenetic analyses (SATé‐II) and classical two‐ and three‐phase phylogenetic analyses were employed, using both maximum likelihood and Bayesian inference methods. Both a two‐gene data set (H3 and Enolase) and a three‐gene data set (H3, Enolase, 12S) were utilized to explore the relationships amongst the targeted species. These analyses showed that the superfamily Nematocarcinoidea, as currently accepted, is polyphyletic. Furthermore, the two major clades recognized by the SATé‐II analysis are clearly concordant with the genera Rhynchocinetes and Cinetorhynchus, which are currently recognized in the morphological‐based classification (implicit phylogeny) as composing the family Rhynchocinetidae. The SATé‐II method is considered superior to the other phylogenetic analyses employed, which failed to recognize these two major clades. Studies using more genes and a more complete species data set are needed to test yet unresolved inter‐ and intrafamilial systematic and evolutionary questions about this remarkable clade of caridean shrimps. © 2014 The Linnean Society of London     

Molecular phylogeny of the Korean Rivellia species (Diptera: Tephritoidea: Platystomatidae) based on 16S rDNA sequences: Testing morphological hypotheses using molecular data

The phylogeny of the genus Rivellia Robineau‐Desvoidy was inferred from mitochondrial 16S ribosomal (r)DNA gene sequences of 13 Korean Rivellia species and six species representing other platystomatid genera and the family Tephritidae. We compared the inferred molecular phylogeny with the previously published morphological cladogram. As a result, the following phylogenetic relationships were recognized: (i) monophyly of the genus Rivellia; (ii) monophyly of the R. syngenesiae species group; (iii) R. depicta and R. apicalis (which were not previously placed in any species group) were recognized as a sister group of the R. syngenesiae species group; and (iv) monophyly of the R. basilaris species group was recognized to a limited extent. These results, even though geographically limited, provide a new insight into the phylogeny of the genus Rivellia. They clearly show the utility of 16S rDNA for phylogenetic analysis of the genus Rivellia. Additional study involving samples from different geographical areas will be needed to gain a better understanding of the adaptive radiation of this species‐rich genus.     

Affinities in C3Cyperus lineages (Cyperaceae) revealed using molecular phylogenetic data and carbon isotope analysis

Maximum likelihood and Bayesian analyses of nrDNA (ETS1f) and plastid DNA (rpl32‐trnL, trnH‐psbA) sequence data are presented for ‘C₃Cyperus’ (Cyperaceae). The term ‘C₃Cyperus’ indicates all species of Cyperus s.l. that use C₃ photosynthesis linked with eucyperoid vegetative anatomy. Sampling comprises 77 specimens of 61 different taxa, representing nearly all previously recognized subdivisions of C₃Cyperus and the segregate genera Courtoisina, Kyllingiella and Oxycaryum. According to our results, the Cyperus clade is divided in six well‐supported clades. The first of these clades (clade 1) forms three subclades largely corresponding to Cyperus sections Haspani, Incurvi and Diffusi. Clade 2 comprises the entirely New World C. section Luzuloidei sensu Denton (1978). Clade 3 is a highly diverse clade including two subclades: clade 3a, C. sections Pseudanosporum and Anosporum plus the segregate genera Courtoisina and Oxycaryum; and clade 3b, C. section Fusci. Clade 4 corresponds to C. section Alternifolii and clade 5 to C. section Leucocephali plus the segregate genus Kyllingiella. The sixth clade is a well‐supported monophyletic clade encompassing all C₄Cyperus s.l. species (‘C₄Cyperus’). This study establishes a phylogenetic framework for future studies. © 2011 The Linnean Society of London, Botanical Journal of the Linnean Society, 2011, 167 , 19–46.     

Diversification and biogeographical history of Neotropical plethodontid salamanders

The Neotropical bolitoglossine salamanders represent an impressive adaptive radiation, comprising roughly 40% of global salamander species diversity. Despite decades of morphological studies and molecular work, a robust multilocus phylogenetic hypothesis based on DNA sequence data is lacking for the group. We estimated species trees based on multilocus nuclear and mitochondrial data for all major lineages within the bolitoglossines, and used our new phylogenetic hypothesis to test traditional biogeographical scenarios and hypotheses of morphological evolution in the group. In contrast to previous phylogenies, our results place all Central American endemic genera in a single clade and suggest that Central America played a critical role in the early biogeographical history of the group. The large, predominantly Mexican genus Pseudoeurycea is paraphyletic, and analyses of the nuclear data place two lineages of Pseudoeurycea as the sister group of Bolitoglossa. Our phylogeny reveals extensive homoplasy in morphological characters, which may be the result of truncation or alteration of a shared developmental trajectory. We used our phylogenetic results to revise the taxonomy of the genus Pseudoeurycea. © 2015 The Linnean Society of London     

Phylogenetic relationships and rate of early diversification of Australian Sphenomorphus group scincids (Scincoidea, Squamata)

The Australian Sphenomorphus group is a morphologically and ecologically diverse clade of lygosomine scincids, collectively comprising more than one‐half of the Australian scincid fauna. A previous phylogenetic analysis of mitochondrial 12S and 16S rRNA, and ND4 and adjacent tRNA sequences for a series of Australian Sphenomorphus group scincids recovered several well‐supported, major clades, although these were generally separated by relatively short branches associated with low support values. Applying a recently described methodology for inferring lineage‐level polytomies, I employ ATP synthetase‐β subunit intron sequences and the existing mitochondrial (mt)DNA data set (with sequences for additional taxa) to assess the hypothesis that the poorly resolved basal relationships within the Australian Sphenomorphus group are a consequence of the major clades having originated essentially simultaneously. Phylogenetic analyses of the separate mtDNA and intron sequence data reveal a number of congruent clades, including Anomalopus, Calyptotis, Ctenotus, Lerista, the Eulamprus quoyii group, the Glaphyromorphus crassicaudis group (including Glaphyromorphus cracens, Glaphyromorphus darwiniensis, and Glaphyromorphus fuscicaudis), Glaphyromorphus gracilipes + Hemiergis, Coeranoscincus reticulatus + Ophioscincus truncatus + Saiphos, and Eulamprus amplus + Eulamprus tenuis + Gnypetoscincus + Nangura. The relationships among these clades indicated by the two data sets, however, are generally incongruent. Although this may be partially ascribed to error in estimating phylogenetic relationships due to insufficient data, some incongruence is evident when uncertainty in inferred relationships is allowed for. Moreover, the congruent clades are typically separated by very short branches, several having a length insignificantly different from zero. These results suggest that initial diversification of Australian Sphenomorphus group scincids was rapid relative to the substitution rates of the mtDNA and intron fragments considered, if not essentially simultaneous. © 2007 The Linnean Society of London, Biological Journal of the Linnean Society, 2007, 92 , 347–366.     

A phylogenetic study of the neotropical catfish family Cetopsidae (Osteichthyes, Ostariophysi, Siluriformes), with a new classification

A hypothesis on the phylogenetic relationships of the neotropical catfish family Cetopsidae is proposed on the basis of the parsimony analysis of 127 morphological characters and most of the species currently recognized. The family and its two recognized subfamilies, the Cetopsinae and Helogeninae, are corroborated as monophyletic, in agreement with recent studies. Previously proposed classifications of the Cetopsinae, however, were found to be poorly representative of the phylogenetic relationships within the subfamily. Major generic rearrangements are implemented in order that the classification of the Cetopsinae reflects the phylogenetic hypothesis. Pseudocetopsis Bleeker (1862) was found to be polyphyletic and to include several disjunct lineages. One of these lineages, recently named as the genus Cetopsidium Vari, Ferraris, and de Pinna (2005), is the sister group to the rest of the Cetopsinae. Denticetopsis Ferraris (1996) is the next sister group to the remainder of the Cetopsinae. The remaining species of the Cetopsinae belong to one of two sister genera, Paracetopsis Bleeker (1862) and Cetopsis Spix and Agassiz (1829). The latter genus includes species formerly assigned to Hemicetopsis Bleeker (1862), Bathycetopsis Lundberg and Rapp Py‐Daniel (1994) and Pseudocetopsis Bleeker (1862). Continued recognition of Hemicetopsis and Bathycetopsis would have required the creation of several additional new genera for various species previously in Pseudocetopsis that form a series of sister groups to a clade composed of Cetopsis oliveirai (Lundberg and Rapp Py‐Daniel, 1994), C. coecutiens (Lichtenstein, 1819) and C. candiru (Spix and Agassiz, 1829). Cetopsis oliveirai is a highly paedomorphic species that displays surprising similarities with conditions in juvenile specimens of C. coecutiens, a species that attains a large body size. Such similarities are not evident in adult specimens of the latter species. A new classification is proposed, within which the subfamily Cetopsinae consists of three tribes, the Cetopsidiini, the Cetopsini and the Denticetopsini. The results of the study form the basis for a discussion of the phylogenetic position of the family within the Siluriformes, the phylogenetic biogeography of the Cetopsidae, paedomorphosis and gigantism in the family, and the effect of different semaphoronts on the intrafamilial phylogeny. Journal compilation © 2007 The Linnean Society of London, Zoological Journal of the Linnean Society, 2007, 150 , 755–813. No claim to original US government works.     

Phylogeny of Mesoamerican freshwater mussels and a revised tribe‐level classification of the Ambleminae

Evolutionary and ecological hypotheses of the freshwater mussel subfamily Ambleminae are intensely geographically biased—a consequence of the complete exclusion of Mesoamerican taxa in phylogenetic reconstructions of the clade. We set out to integrate a portion of the Mesoamerican freshwater mussel assemblage into existing hypotheses of amblemine classification and evolution by generating a molecular phylogeny that includes four previously unsampled Mesoamerican genera and nine species endemic to that region. Given the traditionally hypothesized affinity to Nearctic mussels and the understanding that classification should reflect common ancestry, we predicted that (a) Mesoamerican genera would be recovered as members of the recognized tribes of the Ambleminae, and (b) genera would be supported as monophyletic. The mutilocus phylogeny (COI + 28S + 16S) reported herein does not fully support either of those hypotheses. Neither Cyrtonaias nor Psorula were supported as monophyletic and we predict several other Mesoamerica genera are also non‐monophyletic. The reconstructed phylogeny recovered four independent lineages of Mesoamerican freshwater mussels and these clades are distributed across the phylogeny of the Ambleminae, including the tribe Quadrulini (Megalonaias), Lampsilini (two lineages: Cyrtonaias explicata/Sphenonaias microdon, and Pachynaias), and a previously unrecognized, exclusively Mesoamerican and Rio Grande clade consisting of the genera Psoronaias, Psorula and Popenaias. The latter clade possesses several morphological characteristics that distinguish it from its sister taxon, tribe Lampsilini, and we recognize this newly identified Mesoamerican clade as a fifth tribe of the Ambleminae attributable to the Popenaiadini Heard & Guckert, 1970. This revised classification more completely recognizes the suprageneric diversity of the Ambleminae.