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Search Results: 1 - 10 of 9917 matches for " Frank Glaw "
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Island Evolution and Systematic Revision of Comoran Snakes: Why and When Subspecies Still Make Sense
Oliver Hawlitschek, Zoltán T. Nagy, Frank Glaw
PLOS ONE , 2012, DOI: 10.1371/journal.pone.0042970
Abstract: Species delimitation and species concepts have been a matter of debate among biodiversity researchers in the last decades, resulting in integrative taxonomy approaches and the use of modern species concepts, such as the phylogenetic, evolutionary or general lineage species concepts. The discussion of subspecies status and concepts has been addressed much less extensively, with some researchers completely refraining from recognizing subspecies. However, allopatric insular populations that are particularly differentiated have traditionally been assigned subspecies status. We studied the molecular phylogeny and morphology of endemic Comoran tree snakes of the genus Lycodryas. Taking an integrative taxonomic approach, we used the concept of independent lines of evidence to discriminate between evidence for specific and subspecific status. Molecular (mtDNA) and morphological data provided sufficient evidence to support four different taxa within Comoran Lycodryas. In a revision of this group, we propose two species, each with two subspecies. We present a discussion of the strong sexual dichromatism unique to Comoran Lycodryas within the genus and related genera that may be explained by sexual selection in combination with the absence of major predators. Then, we discuss the effects of insular evolution and the “island rule” on morphological traits in Comoran Lycodryas and in Liophidium mayottensis, another snake endemic to the Comoros. The absence of larger-bodied snakes may have promoted an increase in body size and the number of dorsal scale rows in these species. Finally, we discuss the subspecies concept, its applications and its significance for integrative taxonomy and for limiting taxonomic inflation. We emphasize that taxon descriptions should be based on an integrative approach using several lines of evidence, preferably in combination with statements on the underlying species concepts or operational criteria, to increase the objectivity and comparability of descriptions.
First Large-Scale DNA Barcoding Assessment of Reptiles in the Biodiversity Hotspot of Madagascar, Based on Newly Designed COI Primers
Zoltán T. Nagy, Gontran Sonet, Frank Glaw, Miguel Vences
PLOS ONE , 2012, DOI: 10.1371/journal.pone.0034506
Abstract: Background DNA barcoding of non-avian reptiles based on the cytochrome oxidase subunit I (COI) gene is still in a very early stage, mainly due to technical problems. Using a newly developed set of reptile-specific primers for COI we present the first comprehensive study targeting the entire reptile fauna of the fourth-largest island in the world, the biodiversity hotspot of Madagascar. Methodology/Principal Findings Representatives of the majority of Madagascan non-avian reptile species (including Squamata and Testudines) were sampled and successfully DNA barcoded. The new primer pair achieved a constantly high success rate (72.7–100%) for most squamates. More than 250 species of reptiles (out of the 393 described ones; representing around 64% of the known diversity of species) were barcoded. The average interspecific genetic distance within families ranged from a low of 13.4% in the Boidae to a high of 29.8% in the Gekkonidae. Using the average genetic divergence between sister species as a threshold, 41–48 new candidate (undescribed) species were identified. Simulations were used to evaluate the performance of DNA barcoding as a function of completeness of taxon sampling and fragment length. Compared with available multi-gene phylogenies, DNA barcoding correctly assigned most samples to species, genus and family with high confidence and the analysis of fewer taxa resulted in an increased number of well supported lineages. Shorter marker-lengths generally decreased the number of well supported nodes, but even mini-barcodes of 100 bp correctly assigned many samples to genus and family. Conclusions/Significance The new protocols might help to promote DNA barcoding of reptiles and the established library of reference DNA barcodes will facilitate the molecular identification of Madagascan reptiles. Our results might be useful to easily recognize undescribed diversity (i.e. novel taxa), to resolve taxonomic problems, and to monitor the international pet trade without specialized expert knowledge.
Speciation in little: the role of range and body size in the diversification of Malagasy mantellid frogs
Katharina C Wollenberg, David R Vieites, Frank Glaw, Miguel Vences
BMC Evolutionary Biology , 2011, DOI: 10.1186/1471-2148-11-217
Abstract: We reconstructed a molecular phylogeny based on nuclear and mitochondrial DNA for 257 species and candidate species of the mantellid frog radiation. Based on this phylogeny we identified 53 well-supported pairs of sister species that we used for phylogenetic comparative analyses, along with whole tree-based phylogenetic comparative methods. Sister species within the Mantellidae diverged at 0.2-14.4 million years ago and more recently diverged sister species had geographical range centroids more proximate to each other, independently of their current sympatric or allopatric occurrence. The largest number of sister species pairs had non-overlapping ranges, but several examples of young microendemic sister species occurring in full sympatry suggest the possibility of non-allopatric speciation. Range sizes of species included in the sister species comparisons increased with evolutionary age, as did range size differences between sister species, which rejects peripatric speciation. For the majority of mantellid sister species and the whole mantellid radiation, range and body sizes were associated with each other and small body sizes were linked to higher mitochondrial nucleotide substitution rates and higher clade diversity. In contrast, small range sizes were unexpectedly associated with a slow-down of mitochondrial substitution rates.Based on these results we define a testable hypothesis under which small body sizes result in limited dispersal capabilities and low physiological tolerances, causing smaller and more strongly fragmented ranges. This can be thought to facilitate reproductive isolation and thus favor speciation. Contrary to the expectation of the faster speciation of such microendemic phenotype species, we only found small body sizes of mantellid frogs to be linked to higher diversification and substitution rates, but not small range sizes. A joint analysis of various species-rich regional anuran radiations might provide enough species with all combinations
Advertisement call and tadpole morphology of the clutch-guarding frog Mantidactylus argenteus from eastern Madagascar
Silvia Vejarano,Meike Thomas,Frank Glaw,Miguel Vences
African Zoology , 2011,
Abstract: We provide the first descriptions of the tadpole and advertisement call ofMantidactylus argenteus. Calls consist of 6–15 short and rather melodious notes, with a dominant frequency at 4100–4400 Hz and are emitted from arboreal positions during the day. The larva is an Orton type IV tadpole, with oval body shape and dorsally positioned eyes. The oral disc is bordered with papillae, the labial tooth row formula is 2(2)/3(1–3), the upper jaw sheath is strongly curved and M-shaped, and the lower jaw is strongly curved in the middle and V-shaped, and jaw sheaths are largely unpigmented. Specimens from different series present little variation of this general morphology, except some specimens with a labial tooth row formula of 2(2)/2(1–2) but the same general and oral disc morphology. Based on larval features, the position of M. argenteus within the subgenus Blommersia cannot be confirmed since only few characters are shared with other known tadpoles of this subgenus.
A new species of Heterixalus (Amphibia: Hyperoliidae) from western Madagascar
Miguel Vences,Frank Glaw,Riccardo Jesu,Giovanni Schimmenti
African Zoology , 2011,
Abstract: A new species of hyperoliid frog,Heterixalus carbonei n.sp., is described from the Antsingy forest in western Madagascar. It is characterized by an advertisement call consisting of long and regular note series. The only other Heterixalus with a similar call structure, H. betsileo from higher altitudes in eastern Madagascar, has distinctly shorter notes. After recent discoveries of the occurrence of H. luteostriatus and H. tricolor in western Madagascar, the new species brings the number of Heterixalus known from western Madagascar to three.
Molecular and bioacoustic divergence in Mantidactylus granulatus and M. zavona n.sp. (Anura: Mantellidae): bearings for thebiogeography of northern Madagascar
Miguel Vences,Franco Andreone,Frank Glaw,Jasmin E. Randrianirina
African Zoology , 2011,
Abstract: We analysed the genetic and bioacoustic variability inMantidactylus granulatus, a semi-arboreal frog species endemic to the northern portion of Madagascar. Advertisement calls had a longer note duration in northeastern as compared to northwestern populations. Specimens from mid-altitudes in the Tsaratanana Massif (Northern Central Region) showed distinct call differences. They also had a high sequence differentiation in a fragment of the mitochondrial 16S rRNA gene (pairwise divergence 8.6 %), while all other populations were genetically rather uniform. This Tsaratanana population is described as the new species Mantidactylus zavona; it is also morphologically distinct from the sympatric M. granulatus in that it has a smaller body and a shorter, wider head. The relatively small differences between M. granulatus from different sites in northern Madagascar (pairwise 16S divergences up to 1.4 %), including the isolated Montagne d’Ambre, supports a biogeographic scenario in which the lowland rainforests in this area were connected in Pliocene–Pleistocene times. By contrast,the presence of endemic species at higher altitudes of the Tsaratanana Massif may be seen as evidence for a longer isolation of the habitats at these elevational levels.
A new Gephyromantis (Phylacomantis) frog species from the pinnacle karst of Bemaraha, western Madagascar
Angelica Crottini,Frank Glaw,Maurizio Casiraghi,Richard Jenkins
ZooKeys , 2011, DOI: 10.3897/zookeys.81.1111
Abstract: We describe a new mantellid frog of the subfamily Mantellinae from the karstic Bemaraha Plateau, western Madagascar. The new species belongs to the genus Gephyromantis, subgenus Phylacomantis, which previously included G. azzurrae, G. corvus and G. pseudoasper. Gephyromantis atsingy sp. n. has a snout-vent length of 35–43 mm and is a scansorial frog living among the Tsingy de Bemaraha pinnacles and inside the caves present in the area. A morphological analysis and biomolecular comparison revealed the degree of differentiation between these four species of the Phylacomantis subgenus. The new species seems to be endemic to Tsingy de Bemaraha.
A tiny new species of Platypelis from the Marojejy National Park in northeastern Madagascar (Amphibia: Microhylidae)
Frank Glaw,J?rn K?hler,Miguel Vences
European Journal of Taxonomy , 2012, DOI: 10.5852/ejt.2012.9
Abstract: We describe a tiny new frog species of the genus Platypelis (Anura: Microhylidae: Cophylinae) from Marojejy National Park, northeastern Madagascar. Platypelis ravus sp. nov. differs from all other known Platypelis and Cophyla species by its small size (17-19 mm snout-vent length) and a combination of other morphological and bioacoustic characters. The new species seems to be most closely related to P. milloti with which it shares the principal colour pattern, but exhibits a yellow rather than red posterior venter. Uncorrected pairwise sequence divergence in a 16S rRNA gene fragment to all other known species of the genus (except P. cowanii for which no genetic data is available) is greater than 6%. We suggest the inclusion of the new species in the IUCN threat category “Data Deficient”.
Reliable DNA Barcoding Performance Proved for Species and Island Populations of Comoran Squamate Reptiles
Oliver Hawlitschek, Zoltán T. Nagy, Johannes Berger, Frank Glaw
PLOS ONE , 2013, DOI: 10.1371/journal.pone.0073368
Abstract: In the past decade, DNA barcoding became increasingly common as a method for species identification in biodiversity inventories and related studies. However, mainly due to technical obstacles, squamate reptiles have been the target of few barcoding studies. In this article, we present the results of a DNA barcoding study of squamates of the Comoros archipelago, a poorly studied group of oceanic islands close to and mostly colonized from Madagascar. The barcoding dataset presented here includes 27 of the 29 currently recognized squamate species of the Comoros, including 17 of the 18 endemic species. Some species considered endemic to the Comoros according to current taxonomy were found to cluster with non-Comoran lineages, probably due to poorly resolved taxonomy. All other species for which more than one barcode was obtained corresponded to distinct clusters useful for species identification by barcoding. In most species, even island populations could be distinguished using barcoding. Two cryptic species were identified using the DNA barcoding approach. The obtained barcoding topology, a Bayesian tree based on COI sequences of 5 genera, was compared with available multigene topologies, and in 3 cases, major incongruences between the two topologies became evident. Three of the multigene studies were initiated after initial screening of a preliminary version of the barcoding dataset presented here. We conclude that in the case of the squamates of the Comoros Islands, DNA barcoding has proven a very useful and efficient way of detecting isolated populations and promising starting points for subsequent research.
Rivaling the World's Smallest Reptiles: Discovery of Miniaturized and Microendemic New Species of Leaf Chameleons (Brookesia) from Northern Madagascar
Frank Glaw, J?rn K?hler, Ted M. Townsend, Miguel Vences
PLOS ONE , 2012, DOI: 10.1371/journal.pone.0031314
Abstract: Background One clade of Malagasy leaf chameleons, the Brookesia minima group, is known to contain species that rank among the smallest amniotes in the world. We report on a previously unrecognized radiation of these miniaturized lizards comprising four new species described herein. Methodology/Principal Findings The newly discovered species appear to be restricted to single, mostly karstic, localities in extreme northern Madagascar: Brookesia confidens sp. n. from Ankarana, B. desperata sp. n. from Forêt d'Ambre, B. micra sp. n. from the islet Nosy Hara, and B. tristis sp. n. from Montagne des Fran?ais. Molecular phylogenetic analyses based on one mitochondrial and two nuclear genes of all nominal species in the B. minima group congruently support that the four new species, together with B. tuberculata from Montagne d'Ambre in northern Madagascar, form a strongly supported clade. This suggests that these species have diversified in geographical proximity in this small area. All species of the B. minima group, including the four newly described ones, are characterized by very deep genetic divergences of 18–32% in the ND2 gene and >6% in the 16S rRNA gene. Despite superficial similarities among all species of this group, their status as separate evolutionary lineages is also supported by moderate to strong differences in external morphology, and by clear differences in hemipenis structure. Conclusion/Significance The newly discovered dwarf chameleon species represent striking cases of miniaturization and microendemism and suggest the possibility of a range size-body size relationship in Malagasy reptiles. The newly described Brookesia micra reaches a maximum snout-vent length in males of 16 mm, and its total length in both sexes is less than 30 mm, ranking it among the smallest amniote vertebrates in the world. With a distribution limited to a very small islet, this species may represent an extreme case of island dwarfism.
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