Philip-Sebastian Gehring

Hiding deep in the trees: discovery of divergent mitochondrial lineages in Malagasy chameleons of the Calumma nasutum group

We conducted a comprehensive molecular phylogenetic study for a group of chameleons from Madagascar (Chamaeleonidae: Calumma nasutum group, comprising seven nominal species) to examine the genetic and species diversity in this widespread genus. Based on DNA sequences of the mitochondrial gene (ND2) from 215 specimens, we reconstructed the phylogeny using a Bayesian approach. Our results show deep divergences among several unnamed mitochondrial lineages that are difficult to identify morphologically. We evaluated lineage diversification using a number of statistical phylogenetic methods (general mixed Yule-coalescent model; SpeciesIdentifier; net p-distances) to objectively delimit lineages that we here consider as operational taxonomic units (OTUs), and for which the taxonomic status remains largely unknown. In addition, we compared molecular and morphological differentiation in detail for one particularly diverse clade (the C. boettgeri complex) from northern Madagascar. To assess the species boundaries within this group we used an integrative taxonomic approach, combining evidence from two independent molecular markers (ND2 and CMOS), together with genital and other external morphological characters, and conclude that some of the newly discovered OTUs are separate species (confirmed candidate species, CCS), while others should best be considered as deep conspecific lineages (DCLs). Our analysis supports a total of 33 OTUs, of which seven correspond to described species, suggesting that the taxonomy of the C. nasutum group is in need of revision.

The influence of riverine barriers on phylogeographic patterns of Malagasy reed frogs (Heterixalus).

We analyzed the influence of large rivers on the phylogeography of endemic widespread amphibians along Madagascars east coast, using as models various species and species complexes of Malagasy reed frogs (Heterixalus spp.) that are specialized to either highland or lowland habitats. We assembled a dense sampling across the full species ranges and used mitochondrial (cob) as well as nuclear (Rag-1) DNA sequences to assess their phylogeographies. A multigene mtDNA phylogeny of each species was constructed to establish the relationships among the main phylogroups, in order to understand the geographical regions of clade origins and possible directions of historical range expansions. Distinct intraspecific lineages as diagnosed by mitochondrial haplotype clades were found in highlands and lowlands. Most geographical boundaries among these phylogroups did not coincide with rivers, indicating that the influence of rivers on the primary divergence of phylogroups is probably minor in these frogs. Nevertheless, we found evidence for the influence of one riverine barrier in the lowland species complex, where the most important genetic discontinuity (the border between Heterixalus madagascariensis and H. alboguttatus) coincides with the geographical position of the Mangoro River on Madagascars central east coast. Analyses of the highland species H. betsileo revealed the existence of six deep haplotype lineages, separated in two major subpopulations which differ largely in altitudinal distribution and do not overlap with the geographical settings of rivers in the highlands. Furthermore, our analyses indicated that most of the major intraspecific lineages of reed frogs show signs of a rather recent population expansion.

Weak divergence among African, Malagasy and Seychellois hinged terrapins (Pelusios castanoides, P. subniger) and evidence for human-mediated oversea dispersal

Using phylogenetic and haplotype network analyses of 2036 bp of mitochondrial DNA, we compare samples of the two hinged terrapin species Pelusios castanoides and P. subniger from continental Africa, Madagascar and the Seychelles to infer their biogeography. Owing to the long independent history of Madagascar and the Seychelles, the populations from those islands should be deeply divergent from their African conspecifics. Seychellois populations of the two species are currently recognized as Critically Endangered endemic subspecies. However, even though we found within P. subniger evidence for a cryptic species from the Democratic Republic of the Congo, all other samples assigned to this species were undifferentiated. This suggests that Malagasy and Seychellois populations of P. subniger were introduced by humans and that the Seychellois subspecies P. s. parietalis is invalid. This has implications for current conservation strategies for the Critically Endangered Seychellois populations and suggests that measures should rather focus on endemic species. The situation of P. castanoides could be different. Samples from Madagascar and the Seychelles are weakly, but consistently, differentiated from continental African samples, and Malagasy and Seychellois samples are reciprocally monophyletic in maximum likelihood analyses. However, due to a lack of samples from central and northern Mozambique and Tanzania, we cannot exclude that identical continental haplotypes exist there.

Calumma vohibola, a new chameleon species (Squamata: Chamaeleonidae) from the littoral forests of eastern Madagascar

Abstract We describe Calumma vohibola sp. nov., a morphologically distinct chameleon species of the Calumma nasutum species group from littoral forest fragments of the north-central east coast of Madagascar. Males and females of this species differ from all other species of the Calumma nasutum group by an almost absent rostral appendage, by a characteristic stress colouration in the female consisting of a dark reddish ground colouration with many irregular light blue spots, and by significant sequence divergence in the mitochondrial ND2 gene (10.5–19.4% pairwise distance) and no haplotype sharing in the nuclear C-mos gene compared with other members of the C. nasutum group. A molecular survey of C. nasutum populations occurring near the type locality of the new species reveals an extraordinarily high genetic diversity within this morphologically conservative chameleon group. We suspect that C. vohibola might be restricted to a rather small and fragmented distribution range within the last littoral forest fragments along the coast. Owing to the unsolved taxonomic situation of the C. nasutum group, no reliable distribution data of any member of this group are available at present, and hence we cannot ascertain whether the extent of occurrence of C. vohibola is indeed as restricted as suspected. Intensive surveys and field studies are necessary to clarify the distribution limits of this new species and to assess its conservation status reliably.

Northern origin and diversification in the central lowlands? – Complex phylogeography and taxonomy of widespread day geckos (Phelsuma) from Madagascar

Day geckos of the Phelsuma lineata group are widespread in Madagascar and have been historically split into numerous species and subspecies based almost exclusively on differences in coloration and body size. We apply phylogenetic and phylogeographic methods to examine the biogeography and taxonomy of these lizards, including explicit tests of various biogeographic predictions and based on a molecular data set covering much of the distribution ranges of all species and subspecies of P. lineata, P. dorsivittata, P. comorensis, P. hoeschi, P. kely, and P. pusilla in Madagascar (and the Comoros archipelago for P. comorensis). Sequences of the mitochondrial 16S rRNA and the nuclear RAG-1 gene fragment were determined from 376 samples, and a multigene mtDNA phylogeny of the species group was constructed for the main phylogroups identified in the 16S haplotype network. We used the 16S sequences to estimate the geographic location of the ancestor of each major mtDNA clade and to infer their demographic history using a variety of statistical tools. Our phylogeny separates the taxa analyzed into two well-supported major subclades mainly occurring in the north respectively east of the island. Mismatch distribution of samples together with rejection of neutrality, the results of Bayesian Skyline Plots analysis, and a star-like network suggests a recent demographic expansion for the P. l. lineata lineage into the eastern lowlands, while the highland (P. l. elanthana) and northern clades (P. dorsivittata and P. l. punctulata) show signatures of rather stable populations. A major genetic discontinuity observed coincided with a northern lowland stretch that separates mid-altitude rainforests in the north from those in the center and south. Our analysis points to numerous unsolved taxonomic problems in this group of geckos, especially in the small-sized taxa (P. hoeschi, P. kely, P. pusilla), and provides a basis for a future comprehensive taxonomic revision, which will require integrative analysis of molecular, morphological and chromatic data as well as careful examination of type specimens.

The Kingdom of the Frogs: Anuran Radiations in Madagascar

The island of Madagascar harbors one of the world’s most diverse amphibian faunas with an outstanding degree of 100% endemism at species level among the over 270 native species of frogs. The high research activity of recent years, together with the use of integrative taxonomic approaches, combining molecular genetics, comparative morphology, and bioacoustics, has led to the identification of many morphologically cryptic but evolutionarily highly divergent species of Malagasy frogs, leading to estimates of over 200 yet undescribed species. Ongoing phylogenetic and phylogeographic studies aim to understand the processes that might have generated this unique species diversity and microendemism. By now the larval stages of many Malagasy frogs are tremendously underexplored, although their relevance for the evolution, ecology, and conservation of animals with a biphasic lifestyle is apparent. Habitat destruction and fragmentation are the most important factors threatening amphibian diversity in Madagascar.

Two new species of leaf-tailed geckos ( Uroplatus ) from the Tsaratanana mountain massif in northern Madagascar

The Tsaratanana Massif is the highest mountain massif of Madagascar and is characterized by a high species-level endemism of its biota. Here we describe two new small-sized species of leaf-tailed geckos of the Uroplatus ebenaui group from this region. Named in a preliminary way as confirmed candidate species Uroplatus ebenaui [Ca1] and [Ca2] in previous studies, we here provide detailed data on their molecular and morphological differentiation and describe them as Uroplatus fotsivava sp. nov. and Uroplatus kelirambo sp. nov. Their closest relatives are U. fiera and U. finiavana, respectively, as revealed by a phylogeny based on DNA sequences of four mitochondrial genes. However, integration of various lines of evidence confirms that the new species are independent evolutionary lineages, differing from other Uroplatus by high mitochondrial divergences, lack of haplotype sharing in the nuclear CMOS gene, and shape and relative size of the tail. While U. fotsivava is known from multiple sites at elevations between 1100-1538 m above sea level, U. kelirambo was found only at high elevations between 2000-2200 m a.s.l.; it therefore is the only known forest-dwelling nocturnal gecko reaching such high elevations in Madagascar, and might be narrowly endemic to montane forests of the Tsaratanana Massif.