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Despite the relevance of chemical communication in vertebrates, comparative examinations of macroevolutionary trends in chemical signaling systems are scarce. Many turtle and tortoise species are reliant on chemical signals to communicate in aquatic and terrestrial macrohabitats, and many of these species possess specialized integumentary organs, termed mental glands (MGs), involved in the production of chemosignals. We inferred the evolutionary history of MGs and tested the impact of macrohabitat on their evolution. Inference of ancestral states along a time-calibrated phylogeny revealed a single origin in the ancestor of the subclade Testudinoidea. Thus, MGs represent homologous structures in all descending lineages. We also inferred multiple independent losses of MGs in both terrestrial and aquatic clades. Although MGs first appeared in an aquatic turtle (the testudinoid ancestor), macrohabitat seems to have had little effect on MG presence or absence in descendants. Instead, we find clade-specific evolutionary trends, with some clades showing increased gland size and morphological complexity, whereas others exhibiting reduction or MG loss. In sister clades inhabiting similar ecological niches, contrasting patterns (loss vs. maintenance) may occur. We conclude that the multiple losses of MGs in turtle clades have not been influenced by macrohabitat and that other factors have affected MG evolution.

Telomeres are nucleoprotein complexes protecting chromosome ends in most eukaryotic organisms. In addition to chromosome ends, telomeric-like motifs can be accumulated in centromeric, pericentromeric and intermediate (i.e., between centromeres and telomeres) positions as so-called interstitial telomeric repeats (ITRs). We mapped the distribution of (TTAGGG)n repeats in the karyotypes of 30 species from nine families of turtles using fluorescence in situ hybridization. All examined species showed the expected terminal topology of telomeric motifs at the edges of chromosomes. We detected ITRs in only five species from three families. Combining our and literature data, we inferred seven independent origins of ITRs among turtles. ITRs occurred in turtles in centromeric positions, often in several chromosomal pairs, in a given species. Their distribution does not correspond directly to interchromosomal rearrangements. Our findings support that centromeres and non-recombining parts of sex chromosomes are very dynamic genomic regions, even in turtles, a group generally thought to be slowly evolving. However, in contrast to squamate reptiles (lizards and snakes), where ITRs were found in more than half of the examined species, and birds, the presence of ITRs is generally rare in turtles, which agrees with the expected low rates of chromosomal rearrangements and rather slow karyotype evolution in this group.

Turtles demonstrate variability in sex determination and, hence, constitute an excellent model for the evolution of sex chromosomes. Notably, the sex determination of the freshwater turtles from the family Chelidae, a species-rich group with wide geographical distribution in the southern hemisphere, is still poorly explored. Here we documented the presence of an XX/XY sex determination system in seven species of the Australasian chelid genera Chelodina, Emydura, and Elseya by conventional (karyogram reconstruction, C-banding) and molecular cytogenetic methods (comparative genome hybridization, in situ hybridization with probes specific for GATA microsatellite motif, the rDNA loci, and the telomeric repeats). The sex chromosomes are microchromosomes in all examined species of the genus Chelodina. In contrast, the sex chromosomes are the 4th largest pair of macrochromosomes in the genera Emydura and Elseya. Their X chromosomes are submetacentric, while their Y chromosomes are metacentric. The chelid Y chromosomes contain a substantial male-specific genomic region with an accumulation of the GATA microsatellite motif, and occasionally, of the rDNA loci and telomeric repeats. Despite morphological differences between sex chromosomes, we conclude that male heterogamety was likely already present in the common ancestor of Chelodina, Emydura and Elseya in the Mesozoic period.

Using up to 2456 bp mtDNA and up to 2716 bp nDNA of fresh samples and short sequences of three mitochondrial genes of historical museum material, we examine the phylogeography of Amyda cartilaginea. This data set provides evidence for the existence of deeply divergent genetic lineages which we interpret as three distinct species, two of which are polytypic. On the Great Sunda Islands, the distribution ranges of the two subspecies of Amyda cartilaginea (Boddaert, 1770) sensu stricto and of an undescribed species match palaeodrainage systems. Amyda cartilaginea cartilaginea occurs in the East Sunda palaeodrainage, with records in eastern Borneo and Java. Also a record from Sulawesi, most probably not representing a native population, refers to A. c. cartilaginea. In the North Sunda palaeodrainage (Sumatra, western Borneo) lives Amyda cartilaginea maculosa subsp. nov., which is described herein. One sample from the Baram river (Sarawak, Malaysia) is genetically highly distinct and represents a new species. We refrain from naming this taxon until more material becomes available for morphological characterization. For the continental populations, we resurrect the species Amyda ornata (Gray, 1861). We identify Asian softshell turtles from the Mekong drainage with the nominotypical subspecies, while the genetically distinct populations from Thailand and Myanmar are assigned to Amyda ornata phayrei (Theobald, 1868). Samples from Bangladesh are also genetically distinct and represent an undescribed subspecies and the first country record for Amyda.

Based on 2354 bp of mitochondrial DNA (12S rRNA, ND4, cyt b) and 2573 bp of nuclear DNA (C-mos, ODC, R35), we re-examine the phylogenetic relationships of Nilssonia species. Individual and combined analyses of mitochondrial and nuclear DNA using Maximum Likelihood and Bayesian approaches confirm the monophyly of the genus. While mitochondrial data alone could not resolve the phylogenetic position of N. formosa, nuclear data support a sister group relationship of N. formosa and the remaining Nilssonia species. Combined analyses of mitochondrial and nuclear DNA suggest the following branching pattern, with N. formosa as the sister taxon of the remaining species: N. formosa + ((N. gangetica + N. leithii) + (N. hurum + N. nigricans)). Among the samples we studied is the first record of N. formosa for Yunnan, China, and the first record of wild-living N. nigricans for Bangladesh. In N. gangetica, each of the studied major river basins harbours a genetically distinct population, suggesting that at least three distinct management units should be distinguished: (1) Brahmaputra River; (2) Indus and Ganges Rivers plus Ganges Delta; and (3) Mahanadi River.

We investigated relationships among Asian fl apshell turtles by using 2286 bp of mitochondrial DNA for phylogenetic reconstructions and relaxed molecular clock calculations. Currently three taxa are recognized, the unspotted species Lissemys scutata and L. punctata, with the unspotted subspecies L. p. punctata and the spotted subspecies L. p. andersoni. However, we found fi ve deeply divergent clades, two of which correspond to L. scutata (Myanmar; perhaps also adjacent Thailand and Yunnan, China) and L. p. andersoni (Indus, Ganges and Brahmaputra drainages; western Myanmar), respectively. Within L. p. punctata from peninsular India and Sri Lanka three distinct clades were identifi ed, two from peninsular India and one from Sri Lanka. The two clades from peninsular India are more closely related to L. p. andersoni than to fl apshell turtles from Sri Lanka. Due to a genetic divergence resembling L. scutata, we propose to separate Sri Lankan populations as the distinct species L. ceylonensis (Gray, 1856) from L. punctata. Furthermore, we suggest to restrict the name L. p. punctata (Lacepède, 1788) = L. p. punctata (Bonnaterre, 1789) to populations from southern peninsular India, whereas the name L. p. vittata (Peters, 1854) should be applied to unspotted fl apshell turtles from northern peninsular India. We classify all three taxa from the Indian subcontinent as subspecies because (1) there is morphological and genetic evidence that L. p. andersoni intergrades with L. p. vittata, and (2) the genetic divergence among L. p. punctata, L. p. andersoni and L. p. vittata resembles the degree of differentiation as observed between the latter two subspecies, whereas the differences between L. ceylonensis and L. scutata and among these species and the subspecies of L. punctata are about twice the values as observed among the subspecies of L. punctata. The formation of the subspecies of L. punctata was dated to have occurred between the uppermost Miocene and the Early Pleistocene (mean split ages of approx. 4.5 and 4.2 million years); the origin of L. ceylonensis and L. scutata, to a range between the Early Miocene and the Lower Pliocene (mean split ages of approx. 8 and 11 million years, respectively).

The systematic position of the rare Indian turtle Geoemyda silvatica Henderson is examined by a phylogenetic analysis of mtDNA sequence data (cytochrome-b gene) of most species of Geoemydidae. Geoemyda silvatica represents a basal and isolated taxon within Geoemydidae, definitely not a close relative of any species of Geoemyda or Heosemys, the genera in which G. silvatica has been placed in the past. Therefore, the new genus Vijayachelys is proposed for G. silvatica. Cranial morphology and some other osteological characters of Vijayachelys silvatica are described and illustrated. Differential diagnoses are given for the type species of Melanochelys and the respective type species of the superficially similar genera Geoemyda, Heosemys, and Leucocephalon. According to Bayesian analysis of mtDNA data, Melanochelys trijuga could be distantly related to V. silvatica, whereas the morphological similarity of the other species probably is the result of a similar mode of life. The discovery of the phylogenetically isolated position of V. silvatica highlights the importance of the Western Ghats as a biodiversity hotspot rich in higher-level endemics.

Estuarine Batagur are among the most critically endangered chelonian species. We assess the taxonomic status of the recently discovered Cambodian relic population of Batagur by phylogenetic analyses of three mitochondrial (2096 bp) and three nuclear DNA fragments (1909 bp) using sequences from all other Batagur species and selected allied geoemydids. Furthermore, we calculated haplotype networks of the mitochondrial cytochrome b gene for Cambodian terrapins, B. affinis, B. baska, and B. kachuga and compare external morphology of estuarine Batagur populations. Genetically, Cambodian Batagur are closely related with, but distinct from B. affinis from Sumatra and the west coast of the Malay Peninsula. Morphologically, Cambodian Batagur resemble the distinctive B. affinis populations from the eastern Malay Peninsula that were not available for genetic study. We suggest that the Batagur populations from the eastern Malay Peninsula and Cambodia represent a new subspecies of B. affinis that once was distributed in estuaries surrounding the Gulf of Thailand (Batagur affinis edwardmolli subsp. nov.). Its patchy extant distribution is most probably the result of large-scale habitat alteration and century-long overexploitation. In addition, our phylogenetic analyses suggest repeated switches between riverine and estuarine habitats during the evolution of the extant Batagur species.