Evolutionary transformation of the subcutaneous muscle in rodents of Ctenohystrica (Rodentia: Diatomyidae,Ctenodactylidae, and Hystricognathi)

The present study examined the subcutaneous muscle (m. cutaneus trunci) in a relict species Laonastes aenigmamus (Diatomyidae) and in two ctenodactylids (Ctenodactylidae: Ctenodactylus gundi and Pectinator spekei), which are closely related to Laonastes according to current phylogenetic hypotheses. The comparative morphological analysis also included four representatives of Hystricognathi: Echimys sp., Proechimys sp., Cercomys cunicularis, and Hystrix indica. Laonastes and ctenodactylids have a number of common ancestral traits in the morphology of m. cutaneus trunci. This suggests that they are probably related to the ancestral forms of Ctenohystrica. However, the structural similarity of the subcutaneous muscle in Diatomyidae and Ctenodactylidae is based not only on plesiomorphic (presence of the medial head of m. cutaneus trunci), but also on an apomorphic (the development of the thoracoabdominal portion) feature which is common to both branches of Ctenohystrica (Ctenodactiloidea and Hystricognathi). The results of the comparative analysis suggest a new scenario for the evolutionary transformations of m. cutaneus trunci within the clade Ctenohystrica. This scenario differs from earlier suggestions and proposes initial differentiation of the subcutaneous muscle and possibly its secondary simplification, but on a new basis. On this new basis a further secondary increase in complexity of subcutaneous muscle appears possible in response to various adaptations in hystricognaths.     

The phylogenetic affinities of the chaetognaths: a molecular analysis

The chaetognaths, or arrowworms, constitute a small and enigmatic phylum of marine invertebrates whose phylogenetic affinities have long been uncertain. A popular hypothesis is that the chaetognaths are the sister group of the major deuterostome phyla: chordates, hemichordates, and echinoderms. Here we attempt to determine the affinities of the chaetognaths by using molecular sequence data. We describe the isolation and nucleotide sequence determination of 18S ribosomal DNA from one species of chaetognath and one acanthocephalan. Extensive phylogenetic analyses employing a suite of phylogenetic reconstruction methods (maximum parsimony, maximum likelihood, evolutionary parsimony, and two distance methods) suggest that the hypothesized relationship between chaetognaths and the deuterostomes is incorrect. In contrast, we propose that the lineage leading to the chaetognaths arose prior to the advent of the coelomate metazoa.      

Albumin evolution and phylogenetic relationships among Greek rodents of the families Arvicolidae and Muridae

The phylogenetic relationships of seven rodent species Microtus atticus, M. thomasi, M. epiroticus (family Arvicolidae) and Mus domesticus, Rattus norvegicus, Apodemus flavicollis and A. mystacinus (family Muridae) have been studied. In order to define these relationships we study the albumin evolution using the micro-complement fixation test (MC'F). No phylogenetic (immunological) distance between M. atticus and M. thomasi was found, a fact which confirms from the biochemical point of view the opinion that the former taxon is a synonym of the latter one. A molecular time scale relating MC'F immunological distances and geological time was established based on the assumption of a rate of 100 amino acid substitutions per–20 million years. The time of divergence between M. epiroticus and M. thomasi was estimated to be 0.5–0.6 million years ago (Pleistocene). Such a recent divergence corroborates the opinion based on morphological and protein electrophoretic criteria according to which Terricola (formerly Pitymys ) must be considered as a subgenus of the genus Microtus and not as a distinct genus Pitymys , as previously had been accepted. Apodemus flavicollis and A. mystacinus were separated about 0.65–0.8 million years ago (Pleistocene). The Rattus norvegicus lineage was separated–12.5 million years ago (end of Miocene), shortly before the Mus and Apodemus divergence. Our data indicate that the common ancestor of Arvicolidae and Muridae lived–25 million years ago (early Miocene). All these results are in agreement with paleontological and some recent DNA-DNA hybridization and electrophoretic data.     

Scaling and adaptations of incisors and cheek teeth in caviomorph rodents (Rodentia,Hystricognathi)

The South American hystricognath rodents are one of the most diverse mammalian clades considering their occupied habitats, locomotor modes and body sizes. This might have been partly evolved by diversification of their masticatory apparatus' structure and its ecological commitment, for example, chisel‐tooth digging. In this phylogeny‐based comparative study, we test the relationship between ecological behavior and mechanical features of their incisors and molariforms. In 33 species of nine families of caviomorph rodents, we analyze incisor attributes related to structural stress resistance and molar features related with grinding capacity, for example, second moment of inertia and enamel index (EI) (enamel band length/occlusal surface area), respectively. Most of these variables scaled isometrically to body mass, with a strong phylogenetic effect. A principal component analysis discrimination on the EI clustered the species according to their geographic distribution. We presume that selective pressures in Andean–Patagonian regions, on particular feeding habits and chisel‐tooth digging behaviors, have modeled the morphological characteristics of the teeth. Subterranean/burrower ctenomyids, coruros, and plains viscachas showed the highest bending/torsion strength and anchorage values for incisors; a simplified enamel pattern in molariforms would be associated with a better grinding of the more abrasive vegetation present in more open and drier biomes. J. Morphol. 2012. © 2012 Wiley Periodicals, Inc.     

A molecular phylogenetic framework for the Ryukyu endemic rodents Tokudaia osimensis and Diplothrix legata

Diplothrix legata and Tokudaia osimensis are rodent species endemic to the Ryukyu Islands (Okinawa area) of the southern part of Japan. To place them within a phylogenetic framework of Asian rodent species, we examined the molecular relationships among these species and Apodemus, Micromys, Mus, and Rattus, using an analysis of mitochondrial cytochrome b gene (1140 bp) and nuclear IRBP gene (782 bp) sequences. The results indicate that the four main murine genera and Tokudaia diverged at similar evolutionary times, namely at the time of the radiation of Murinae, 14 to 40 million years ago, depending on different concepts for the divergence times of Rattus and Mus. In contrast, Diplothrix separated from the Rattus group more recently. Our results indicate that D. legata and the Rattus group diverged at 20-30% of the divergence time of Rattus and Mus under the assumption of the molecular clock, suggesting that D. legata established its lineage at least by the beginning of the Pleistocene era. It is thus evident that the Okinawa area preserves rare indigenous species with various levels of genetic endemicity.     

Ribosomal DNA: molecular evolution and phylogenetic inference.

Ribosomal DNA (rDNA) sequences have been aligned and compared in a number of living organisms, and this approach has provided a wealth of information about phylogenetic relationships. Studies of rDNA sequences have been used to infer phylogenetic history across a very broad spectrum, from studies among the basal lineages of life to relationships among closely related species and populations. The reasons for the systematic versatility of rDNA include the numerous rates of evolution among different regions of rDNA (both among and within genes), the presence of many copies of most rDNA sequences per genome, and the pattern of concerted evolution that occurs among repeated copies. These features facilitate the analysis of rDNA by direct RNA sequencing, DNA sequencing (either by cloning or amplification), and restriction enzyme methodologies. Constraints imposed by secondary structure of rRNA and concerted evolution need to be considered in phylogenetic analyses, but these constraints do not appear to impede seriously the usefulness of rDNA. An analysis of aligned sequences of the four nuclear and two mitochondrial rRNA genes identified regions of these genes that are likely to be useful to address phylogenetic problems over a wide range of levels of divergence. In general, the small subunit nuclear sequences appear to be best for elucidating Precambrian divergences, the large subunit nuclear sequences for Paleozoic and Mesozoic divergences, and the organellar sequences of both subunits for Cenozoic divergences. Primer sequences were designed for use in amplifying the entire nuclear rDNA array in 15 sections by use of the polymerase chain reaction; these "universal" primers complement previously described primers for the mitochondrial rRNA genes. Pairs of primers can be selected in conjunction with the analysis of divergence of the rRNA genes to address systematic problems throughout the hierarchy of life.     

First molecular evidence for reassessing phylogenetic affinities between genets (Genetta) and the enigmatic genet-like taxa Osbornictis, Poiana and Prionodon (Carnivora, Viverridae)

Gaubert, P., Tranier, M., Delmas, A.-S., Colyn, M. & Veron, G. (2004). First molecular evidence for reassessing phylogenetic affinities between genets ( Genetta ) and the enigmatic genet-like taxa Osbornictis , Poiana and Prionodon (Carnivora, Viverridae). — Zoologica Scripta, 33 , 117–129.
The subfamily Viverrinae is a composite group of carnivores comprising the large and plantigrade terrestrial civets ( Civettictis , Viverricula and Viverra ) and the slender and generally more arboreal genets and genet-like taxa ( Genetta , Prionodon , Poiana , Osbornictis ), both having Asiatic and African representatives. The problematic phylogenetic relationships between genets and genet-like taxa are addressed for the first time from a molecular perspective through complete cytochrome b gene sequences. We used a large taxonomic sample set including some very rare and crucial species such as Osbornictis piscivora , Poiana richardsonii (museum specimen material) and Genetta johnstoni . The results from parsimony, distance and maximum likelihood analyses do not support the monophyly of the Viverrinae and contradict previous morphological hypotheses. The Asiatic linsangs ( Prionodon spp.) are excluded from the Viverrinae and represent either a basal Feliformia or Viverridae. The other genet-like taxa constitute a strongly supported monophyletic African group, in which the African linsang (represented by Poiana richardsonii ) is a sister group to the genets. The aquatic genet Osbornictis piscivora is included within the latter clade, and the genus Osbornictis should be considered a junior synonym of Genetta . African and Asiatic terrestrial civets are monophyletic, but their phylogenetic affinities with the genet-like clade are inconclusive using our data set. On the basis of our molecular results, morphological convergences and adaptations to peculiar habitats and ways of life within genets and genet-like taxa are discussed.     

First molecular phylogenetic insights into the evolution of Eriocaulon (Eriocaulaceae,Poales)

Eriocaulon is a genus of c. 470 aquatic and wetland species of the monocot plant family Eriocaulaceae. It is widely distributed in Africa, Asia and America, with centres of species richness in the tropics. Most species of Eriocaulon grow in wetlands although some inhabit shallow rivers and streams with an apparent adaptive morphology of elongated submerged stems. In a previous molecular phylogenetic hypothesis, Eriocaulon was recovered as sister of the African endemic genus Mesanthemum. Several regional infrageneric classifications have been proposed for Eriocaulon. This study aims to critically assess the existing infrageneric classifications through phylogenetic reconstruction of infrageneric relationships, based on DNA sequence data of four chloroplast markers and one nuclear marker. There is little congruence between our molecular results and previous morphology-based infrageneric classifications. However, some similarities can be found, including Fyson’s sect. Leucantherae and Zhang’s sect. Apoda. Further phylogenetic studies, particularly focusing on less well sampled regions such as the Neotropics, will help provide a more global overview of the relationships in Eriocaulon and may enable suggesting the first global infrageneric classification.

     

A molecular analysis of the phylogenetic affinities of Saccoglossus cambrensis Brambell & Cole (Hemichordata).

Traditional approaches to phylogeny reconstruction have not allowed precise resolution of the evolutionary relationships between the major deuterostome phyla (chordates, hemichordates, echinoderms). Here we report the use of a molecular approach to investigate deuterostome phylogeny. We have used a polymerase chain reaction-based strategy to amplify, clone and sequence parts of the genes coding for 18S ribosomal RNA from Saccoglossus cambrensis (Hemichordata), Arbacia sp. (Echinodermata) and, for comparison, Mytilus edulis (Mollusca). We report the results of phylogenetic reconstructions using these, and homologous sequences from other eukaryotes. The results of our analyses are consistent with the hypothesis that S. cambrensis and vertebrates share a common ancestor not shared by echinoderms.     

A new molecular phylogenetic hypothesis for the evolution of freshwater eels

Phylogenetic analysis of a segment of the mitochondrial 16S rDNA of eight Anguilla species from the Indo-Pacific region and from the North Atlantic revealed that the genus Anguilla appears to be surprisingly young, based upon the small observed maximum genetic distance of 4.8% and the high degree of morphological similarity among the species. The placement of A. marmorata as the most ancestral lineage suggests that the genus is likely to have originated in the Indo-Malayian region, from which it quickly spread. Two Pacific species, A. obscura and A. japonica, branched next. A. japonica was placed as sister group to all remaining species, which formed three clades: the first comprising A. australis, the second A. reinhardti and A. mossambica, and the third A. anguilla and A. rostrata. All analyzed specimens of A. rostrata originating from southern New Jersey to Nova Scotia had identical mitotypes, while five mitochondrial genotypes were found in Europe differing by zero to two substitutions. The two Atlantic eel species are very closely related; all surveyed specimens of A. anguilla differ by three to five substitutions from their American allies, corroborating the existence of two distinct biological species. This was also confirmed by restriction analysis of a 350-bp segment of the cytochrome b, in which American specimens were distinct in sharing a single diagnostic restriction site of HinfI. Our results suggest little to no gene flow between the two nominal Atlantic eel species.     

Geometric morphometrics of the scapula of South American caviomorph rodents (Rodentia: Hystricognathi): Form, function and phylogeny

The scapula of the ecomorphologically diverse South American caviomorph rodents was studied through geometric morphometric techniques, using landmarks and semilandmarks to capture the shape of this complex morphological structure. Representatives of 33 species from all caviomorph superfamilies, as well as Hystrix cristata for comparisons, were analyzed. Marked differences in scapular shape were found among the major caviomorph lineages analyzed, particularly in the shape and length of the scapular spine and development of the great scapular notch. Shape differences were not influenced by body size, and only partially influenced by locomotor mode. Thus, at this scale of analysis, phylogenetic history seems to be the strongest factor influencing scapular shape. The scapular shape of erethizontids, chinchillids and Cuniculus paca could represent the less specialized state with respect to the highly differentiated scapula of octodontoids and most cavioids. In this sense, the characteristic scapular morphologies of octodontoids and cavioids could reflect particular functional capabilities and constraints associated with the evolution of prevalent locomotor modes within each lineage.     

The phylogenetic affinities of the Socotra Bunting Emberiza socotrana

The monophyly of the African ‘brown bunting’ complex was corroborated by a recent molecular study. However, the little-known Socotran endemic Emberiza socotrana, which is morphologically similar to the other taxa in this complex, was not included. Here we present a hypothesis of the phylogenetic relationships of the Socotra Bunting based on one mitochondrial gene and one nuclear intron. We found the Socotra Bunting to be deeply nested within the African ‘brown bunting’ complex and, although morphologically most similar to E. capensis, it proved to be more closely related to the E. striolata/sahari and E. tahapisi/goslingi species groups. The phylogenetic uniqueness of the Socotra Bunting underpins once more the evolutionary importance of the Endemic Bird Area of Socotra, which is often considered the ‘Galápagos of the Indian Ocean’.     

c-mos variation in songbirds: molecular evolution, phylogenetic implications, and comparisons with mitochondrial differentiation

Nucleotide sequences from the c-mos proto-oncogene have previously been used to reconstruct the phylogenetic relationships between distantly related vertebrate taxa. To explore c-mos variation at shallower levels of avian divergence, we compared c-mos sequences from representative passerine taxa that span a range of evolutionary differentiation, from basal passerine lineages to closely allied genera. Phylogenetic reconstructions based on these c-mos sequences recovered topologies congruent with previous DNA-DNA hybridization-based reconstructions, with many nodes receiving high support, as indicated by bootstrap and reliability values. One exception was the relationship of Acanthisitta to the remaining passerines, where the c-mos-based searches indicated a three-way polytomy involving the Acanthisitta lineage and the suboscine and oscine passerine clades. We also compared levels of c-mos and mitochondrial differentiation across eight oscine passerine taxa and found that c-mos nucleotide substitutions accumulate at a rate similar to that of transversion substitutions in mitochondrial protein-coding genes. These comparisons suggest that nuclear-encoded loci such as c-mos provide a temporal window of phylogenetic resolution that overlaps the temporal range where mitochondrial protein-coding sequences have their greatest utility and that c-mos substitutions and mtDNA transversions can serve as complementary, informative, and independent phylogenetic markers for the study of avian relationships.     

Morphology reinforces proposed molecular phylogenetic affinities: a revised classification for Gelechioidea (Lepidoptera)

Gelechioidea are one of the most species rich and least studied superfamilies of Lepidoptera. We examine the interrelationships within the superfamily using the densest taxon sampling to date, combined with the most extensive ever morphological and molecular character data. We perform partitioned and combined analyses using maximum likelihood, Bayesian and parsimony approaches. The combined dataset consists of 155 exemplar species of Gelechioidea, representing nearly all subfamilies recognized in recent classifications. Parsimony analyses are performed with a dataset including 28 additional terminal taxa with only morphological data available. We use eight genes with a total of 6127 bp, and morphological data with 253 characters derived from larval, pupal, and adult morphology. The analyses of combined data yield more resolved trees and significantly better‐supported groupings than either dataset when analysed alone. The recurrent monophyletic groupings in all our model‐based analyses support a revision of the family classification. Deeper relationships vary between analyses and data partitions, leaving them ambiguous. The place of the root remains a challenge for future research. We propose a revised classification and suggest the division of Gelechioidea into 16 families. We redefine Depressariidae Meyrick, 1883 for a monophylum that includes Acriinae, Aeolanthinae, Cryptolechiinae, Depressariinae, Ethmiinae, Hypercalliinae, Hypertrophinae, Peleopodinae, Oditinae, Stenomatinae, Carcina, and a diversity of predominantly New World taxa previously excluded from Lypusidae (Amphisbatidae s. authors) but left without family position. A monophyletic Oecophoridae s. s., including Deuterogoniinae and Pleurotinae, is obtained for the first time with significant support. Elachistidae s. l. is found to be polyphyletic, and Elachistidae is restricted to comprise Agonoxeninae, Elachistinae, and Parametriotinae. Batrachedridae are polyphyletic, with several genera pending further study. Apart from the core Batrachedra, the taxa previously included in this family are grouped in an expanded Pterolonchidae, together with Coelopoetinae and Syringopainae. Lypusidae s. s. and Chimabachidae form a monophylum; Chimabachinae is united with Lypusidae as a subfamily, stat. n. Our results contradict the subfamily classifications of several families, notably Lecithoceridae and Autostichidae, but due to insufficient sampling of taxa we refrain from comprehensive taxonomic conclusions on the subfamily level, and encourage focused studies to resolve these groups.     

Morphology agrees with molecular data: phylogenetic affinities of Euptychiina butterflies (Nymphalidae: Satyrinae)

Euptychiina is the most species‐rich subtribe of Neotropical Satyrinae, with over 450 known species in 47 genera (14 monotypic). Here, we use morphological characters to examine the phylogenetic relationships within Euptychiina. Taxonomic sampling included 105 species representing the majority of the genera, as well as five outgroups. A total of 103 characters were obtained: 45 from wing pattern, 48 from genitalia and 10 from wing venation. The data matrix was analysed using maximum parsimony under both equal and extended implied weights. Euptychiina was recovered as monophyletic with ten monophyletic genera, contrasting previous DNA sequence‐based phylogenies that did not recover the monophyly of the group. In agreement with sequence‐based hypotheses, however, three main clades were recognized: the ‘Megisto clade’ with six monophyletic and three polyphyletic genera, the ‘Taygetis clade’ with nine genera of which three were monophyletic, and the ‘Pareuptyhia clade’ with four monophyletic and two polyphyletic genera. This is the first morphology‐based phylogenetic hypothesis for Euptychiina and the results will be used to complement molecular data in a combined analysis and to provide critical synapomorphies for clades and genera in this taxonomically confused group.     

Morphological vs. molecular evolution: ecology and phylogeny both shape the mandible of rodents

What actually is the expected pattern relating to molecular and morphological divergence? A phylogenetic correlation is expected; however, natural selection may force morphological evolution away from this expected correlation. To assess this relationship and the way it is modulated by selection, we investigated the radiation of the murine rodents, also called as Old World rats and mice. Regarding their diet, they are diversified as they include many omnivorous as well as specialist taxa. The size and shape of the mandible, a morphological character involved in the feeding process, was quantified and compared with an estimate of molecular divergence based on interphotoreceptor retinoid binding protein (IRBP) sequences. Size and shape of the mandible appeared to be related by an allometric relationship whatever the ecology of the taxa. Small size characterizes most murines, causing a dominance of low size distances; still, the frequency of important size differentiation increases with molecular distances. Regarding shape changes, the pattern is much contrasted between omnivores and specialists. A pattern of phenotypic drift characterizes the mandible evolution of taxa sharing an omnivorous diet. Little saturation occurs over more than 10 million years with regard to the shape of the mandible that appears as a valuable marker of phylogenetic history in this context. In contrast, important morphological distances can occur when specialist taxa are involved, even when the molecular divergence is small. Ecological specialization thus triggers an uncoupling of molecular and phenotypic evolution, and the departure from a phenotypic drift pattern.