We analyse phylogeny, systematics and biogeography of slider turtles (Trachemys spp.) using sequence data of four mitochondrial genes (3242 bp) and five nuclear loci (3396 bp) of most South American and southern Central American taxa and representatives of northern Central American, West Indian and North American slider species (16 species and subspecies) and allied North American species (genera Chrysemys, Deirochelys, Graptemys, Malaclemys, Pseudemys). By applying maximum likelihood, relaxed molecular clock and ancestral range analyses, we provide evidence for two successive colonizations of South America by slider turtles. In addition, we show that the current species delineation of Central and South American slider turtles is incorrect. Our data suggest that Trachemys grayi is a distinct polytypic species that embraces, besides the nominotypical subspecies, T. g. emolli and T. g. panamensis. Trachemys ornata is also polytypic with the subspecies T. o. ornata, T. o. callirostris, T. o. cataspila, T. o. chichiriviche and T. o. venusta. Moreover, T. adiutrix should be regarded as a subspecies of T. dorbigni. All studied Trachemys species are inferred to have originated in the Late Miocene to Early Pliocene. The ancestor of the two subspecies of T. dorbigni colonized South America most probably prior to the establishment of the land bridge connecting Central and South America, whereas the two South American subspecies of T. ornata represent a younger independent immigration wave from Central America.

European pond turtles represent a phylogeographically deeply structured complex of distinct taxa. Here, we use mitochondrial DNA sequences (cytochrome b gene) and eight polymorphic microsatellite loci to investigate genetic differentiation and gene flow of Sicilian, Corsican and Sardinian pond turtles and of subspecies involved in two secondary contact zones in the Pyrenean region and Southern Italy. Mitochondrial and microsatellite differentiation is largely concordant in populations from the core regions of the distribution ranges of the studied taxa. Both marker systems provide no evidence for gene flow between Sicilian pond turtles (Emys trinacris) and Southern Italian subspecies of E. orbicularis. By contrast, in the contact zones limited gene flow occurs between distinct subspecies of E. orbicularis. Although the Southern Italian contact zone is significantly older than the Pyrenean contact zone of Holocene age, patterns of asymmetric introgression are similar. Introgressive hybridization leads to the exchange of mitochondria, but microsatellite data indicate only a few individuals with mixed ancestry. This suggests that incipient isolating mechanisms maintain largely discrete nuclear genomic gene pools. Furthermore, this implies that Southern Italy acted as a hotspot rather than as a melting pot of genetic diversity during the last glacial. Pond turtles from Corsica and Sardinia are not differentiated from continental populations of the subspecies E. o. galloitalica, neither in the mitochondrial nor in the quickly evolving microsatellite markers. As the fossil record argues for a continuous presence of pond turtles on both islands since the Middle Pleistocene, this suggests that the native island populations became extinct and the extant turtles were later introduced by prehistoric settlers. The lack of genetic differentiation of pond turtles from Corsica and Sardinia supports the view that the subspecies described from these islands are not valid.

An international initiative takes conservation planning into the deep ocean to inform environmental management of deep-sea mining.

rfer, A. K. (2010). Molecular phylogeny of African hinged and helmeted terrapins (Testudines: Pelomedusidae: Pelusios and Pelomedusa). -Zoologica Scripta, 40, 115-125.With 18 currently recognised species, Pelusios is one of the most speciose chelonian genera worldwide, even though the taxonomy of some species is contentious. Recent investigations suggested that the closely related, but morphologically distinct genus Pelomedusa is paraphyletic with respect to Pelusios, and that Pelomedusa consists of nine deeply divergent lineages. Using three mitochondrial and three nuclear DNA fragments (2054 bp mtDNA, 2025 bp nDNA), we examined for the first time the phylogeny of Pelusios by molecular means. Our analyses included all Pelusios species, except the probably extinct P. seychellensis, as well as the nine Pelomedusa lineages. The results showed that Pelusios and Pelomedusa are reciprocally monophyletic. Limited sampling of Pelusios species and homoplasy introduced by remote outgroups most likely explain the paraphyly of Pelomedusa in previous studies. The distinctiveness of most Pelusios species was confirmed, but none of the currently recognised species groups within Pelusios was monophyletic. In Pelusios rhodesianus and P. sinuatus distinct genetic lineages were discovered, suggestive of cryptic taxa. In contrast, the recognition of the weakly differentiated P. castaneus and P. chapini as full species is doubtful, as is the validity of the Malagasy and Seychellois subspecies of P. castanoides. GenBank sequences of P. williamsi were nested within P. castaneus, but the morphological distinctiveness of the two species makes it likely that the GenBank sequences (derived from a turtle from the pet trade) are misidentified. Divergence among the distinct genetic lineages of Pelomedusa equals or exceeds the differences among Pelusios species, supporting the view that Pelomedusa is a species complex.

Using virtually range-wide sampling for three pond turtle taxa (Emys orbicularis galloitalica,\ud E. o. hellenica, E. trinacris), we analyse gene flow across their southern Italian contact zone.\ud Based on population genetic analyses of 15 highly polymorphic microsatellite loci and a\ud mitochondrial marker, we show that the general genetic pattern matches well with the current\ud taxon delimitation. Yet, single individuals with conflicting genetic identity suggest\ud translocation of turtles by humans. In addition, we identify in south-western France and the\ud vicinity of Rome populations being heavily impacted by introduced turtles. Cline analyses\ud reveal that the major genetic break between E. o. galloitalica and E. o. hellenica corresponds\ud well with the currently accepted intergradation zone in southern Italy. However, introgression\ud is largely unidirectional from E. o. galloitalica into E. o. hellenica. In the distribution\ud range of the latter subspecies, genetic footprints of E. o. galloitalica are evident along most\ud of the Italian east coast. Our results corroborate that E. o. galloitalica was introduced long\ud ago in Corsica and Sardinia and naturalized there. Gene flow between E. orbicularis and\ud E. trinacris is negligible, with the Strait of Messina matching well with the narrow cline centre\ud between the two species. This contrasts with other Mediterranean freshwater turtle species\ud with extensive transoceanic gene flow. Compared to the two subspecies of E. orbicularis,\ud the Sicilian E. trinacris shows an unexpectedly strong population structuring, a finding\ud also of some relevance for conservation. The differences between the two taxon pairs\ud E. orbicularis/E. trinacris and E. o. galloitalica/E. o. hellenica support their current taxonomic\ud classification and make them attractive objects for follow-up studies to elucidate the\ud underlying mechanisms of speciation by comparing their propertie

The European pond turtle (Emys orbicularis) is a Nearctic element in the African fauna and thought to have invaded North Africa from the Iberian Peninsula. All North African populations are currently identified with the subspecies E. o. occidentalis. However, a nearly range-wide sampling in North Africa used for analyses of mitochondrial and microsatellite DNA provides evidence that only Moroccan populations belong to this taxon, while eastern Algerian and Tunisian pond turtles represent an undescribed distinct subspecies. These two taxa are most closely related to E. o. galloitalica with a native distribution along the Mediterranean coast of northern Spain through southern France to western and southern Italy. This group is sister to a clade comprising several mitochondrial lineages and subspecies of E. orbicularis from Central and Eastern Europe plus Asia, and the successive sisters are E. o. hellenica and E. trinacris. Our results suggest that E. orbicularis has been present in North Africa longer than on the Iberian Peninsula and that after an initial invasion of North Africa by pond turtles from an unknown European source region, there was a phase of diversification in North Africa, followed by a later re-invasion of Europe by one of the African lineages. The differentiation of pond turtles in North Africa parallels a general phylogeographic paradigm in amphibians and reptiles, with deeply divergent lineages in the western and eastern Maghreb. Acknowledging their genetic similarity, we propose to synonymize the previously recognized Iberian subspecies E. o. fritzjuergenobsti with E. o. occidentalis sensu stricto. The seriously imperiled Moroccan populations of E. o. occidentalis represent two Management Units different in mitochondrial haplotypes and microsatellite markers. The conservation status of eastern Algerian pond turtles is unclear, while Tunisian populations are endangered. Considering that Algerian and Tunisian pond turtles represent an endemic taxon, their situation throughout the historical range should be surveyed to establish a basis for conservation measures.

While secondary contact between Mytilus edulis and Mytilus trossulus in North America results in mosaic hybrid zone formation, both species form a hybrid swarm in the Baltic. Despite pervasive gene flow, Baltic Mytilus species maintain substantial genetic and phenotypic differentiation. Exploring mechanisms underlying the contrasting genetic composition in Baltic Mytilus species will allow insights into processes such as speciation or adaptation to extremely low salinity. Previous studies in the Baltic indicated that only weak interspecific reproductive barriers exist and discussed the putative role of adaptation to environmental conditions. Using a combination of hydrodynamic modelling and multilocus genotyping, we investigate how oceanographic conditions influence passive larval dispersal and hybrid swarm formation in the Baltic. By combining our analyses with previous knowledge, we show a genetic transition of Baltic Mytilus species along longitude 12°-13°E, that is a virtual line between Malmö (Sweden) and Stralsund (Germany). Although larval transport only occurs over short distances (10-30 km), limited larval dispersal could not explain the position of this genetic transition zone. Instead, the genetic transition zone is located at the area of maximum salinity change (15-10 psu). Thus, we argue that selection results in weak reproductive barriers and local adaptation. This scenario could maintain genetic and phenotypic differences between Baltic Mytilus species despite pervasive introgressive hybridization.

No abstract