RESUMEN
Scolecophidia (worm snakes) are a vertebrate group with high ecomorphological conservatism due to their burrowing lifestyle. The Eurasian or Greek blindsnake Xerotyphlops vermicularis is their only European representative, a species-complex with an old diversification history. However, its systematics and taxonomy has remained untouched. Here, we extend previous work that relied heavily on mitochondrial markers, following a multi-locus approach and applying several species-delimitation methods, including a Bayesian coalescence-based approach (STACEY). Four "species" delimitation analyses based on the mtDNA (ABGD, bGMYC, mPTP, parsimony networks) returned 14, 11, 9 and 10 clusters, respectively. By mitotyping twice as many specimens as before, we have a complete picture of each cluster's distribution. With the exception of the highly-divergent Levantine lineage, the three independent nuclear markers did not help with phylogenetic resolution, as demonstrated in haplotype networks, concatenated and species-trees, a result of incomplete lineage sorting. The prevailing model from the coalescence-based species-delimitation identified two species: the lineage from the Levant and all others. We formally recognize them as distinct species and resurrect Xerotyphlops syriacus (Jan, 1864) to include the Levantine blindsnakes. Finally, X. vermicularis and X. syriacus may represent species-complexes themselves, since they include high levels of cryptic diversity.
Asunto(s)
Tipificación Molecular , Filogenia , Serpientes/clasificación , Serpientes/genética , Animales , Teorema de Bayes , ADN Mitocondrial/genética , Variación Genética , Haplotipos , Mitocondrias/genética , Especificidad de la EspecieRESUMEN
The Aegean region, located in the Eastern Mediterranean, is an area of rich biodiversity and endemism. Its position, geographical configuration and complex geological history have shaped the diversification history of many animal taxa. Mygalomorph spiders have drawn the attention of researchers, as excellent model systems for phylogeographical investigations. However, phylogeographic studies of spiders in the Aegean region are scarce. In this study, we focused on the phylogeography of the endemic ctenizid trap-door spider Cyrtocarenum Ausserer, 1871. The genus includes two morphologically described species: C. grajum (C.L. Koch, 1836) and C. cunicularium (Olivier, 1811). We sampled 60 specimens from the distributions of both species and analyzed four mitochondrial and two nuclear markers. Cyrtocarenum served as an example to demonstrate the importance of natural history traits in the inference of phylogeographic scenarios. The mtDNA substitution rates inferred for the genus are profoundly higher compared to araneomorph spiders and other arthropods, which seems tightly associated with their biology. We evaluate published mtDNA substitution rates followed in the literature for mygalomorph spiders and discuss potential pitfalls. Following gene tree (maximum likelihood, Bayesian inference) and species tree approaches ((*)BEAST), we reconstructed a time-calibrated phylogeny of the genus. These results, combined with a biogeographical ancestral-area analysis, helped build a biogeographic scenario that describes how the major palaeogeographic and palaeoclimatic events of the Aegean may have affected the distribution of Cyrtocarenum lineages. The diversification of the genus seems to have begun in the Middle Miocene in the present west Aegean area, while major phylogenetic events occurred at the Miocene-Pliocene boundary for C. cunicularium, probably related to the Messinian Salinity Crisis. Our results also demonstrate the clear molecular distinction of the two morphologically described species, but possible cryptic lineages may exist within C. cunicularium.
Asunto(s)
ADN Mitocondrial/genética , Tasa de Mutación , Filogenia , Arañas/genética , Animales , Teorema de Bayes , Núcleo Celular/genética , Clima , Grecia , Mitocondrias/genética , Filogeografía , TurquíaRESUMEN
The majority of the family Typhlopidae occurs in the Neotropic, Australasian, Indo-Malayan and Afrotropic ecoregions. They show a restricted distribution in the western Palearctic, where they include few native species, i.e. Rhinotyphlops simoni, R. episcopus and Typhlops vermicularis. A unique species among typhlopids is T. socotranus, found in Socotra, one of the most endemic-rich archipelagoes. In this study we determine the phylogenetic position of the above mentioned species and discuss their systematics, origin and biogeography. For this purpose we use three protein-coding nuclear markers (AMEL-amelogenin, BDNF-brain-derived neurotrophic factor and NT3-neurotrophin 3) to construct a time-calibrated phylogeny of the family Typhlopidae. Our results show that T. socotranus is a sister-species to T. vermicularis, while R. simoni and R. episcopus are sister-species to each other and are found within the African clade of the family, although they are geographically distributed in west Asia. Additionally we discuss several hypotheses on their origin, as well as the occurence of typhlopids in Eurasia.
Asunto(s)
Núcleo Celular/genética , Filogenia , Serpientes/clasificación , África , Amelogenina/clasificación , Amelogenina/genética , Animales , Asia , Teorema de Bayes , Factor Neurotrófico Derivado del Encéfalo/clasificación , Factor Neurotrófico Derivado del Encéfalo/genética , Núcleo Celular/química , Especiación Genética , Neurotrofina 3/clasificación , Neurotrofina 3/genética , Filogeografía , Serpientes/genéticaRESUMEN
Typhlops vermicularis is the only extant scolecophidian representative occurring in Europe. Its main distribution area, the eastern Mediterranean, has a complicated geological and climatic history that has left an imprint on the phylogenies and biogeography of many taxa, especially amphibians and reptiles. Since reptiles are sensitive indicators of palaeogeographical and palaeoclimatic events, we investigated the intraspecific genealogy of T. vermicularis in a phylogeographical framework. A total of 130 specimens were analyzed, while the use of formalin and ethanol as preservatives called for a special treatment of the samples. Partial sequences of two mitochondrial (12S and ND2) and one nuclear (PRLR) marker were targeted and the results of the phylogenetic analyses (NJ, ML and BI) and the parsimony-network revealed the existence of 10 evolutionary significant units within this species. In combination with the results of the dispersal-vicariance analysis, we may conclude that the Eurasian blindsnake has encountered a sequence of extinction events, followed by secondary expansion from refugia. Estimation of divergence times showed that severe climatic changes between significantly wetter and drier conditions in the Late Neogene have played a key role on the evolutionary and biogeographical history of T. vermicularis. Additionally, both markers (mtDNA and nDNA) distinguished a largely-differentiated evolutionary lineage (Jordan and south Syria), which could even be reckoned as a full species. Our study reveals the existence of cryptic evolutionary lineages within T. vermicularis, which calls for further attention both on the protection of intraspecific varieties and the respective geographic areas that hold them.
Asunto(s)
Serpientes/genética , Animales , ADN Mitocondrial , Evolución Molecular , Variación Genética , Datos de Secuencia Molecular , NADH Deshidrogenasa/genética , Filogenia , Filogeografía , ARN Ribosómico , Serpientes/clasificaciónRESUMEN
We analyze geographic genetic variation in C. ocellatus to evaluate the influences of major climatic, paleogeographic and anthropogenic factors in its biogeographic history. Ninety four specimens from 61 populations were collected across all of its geographical range and analyzed based on partial mitochondrial sequences (cyt b, 12S, and ND1). Our results demonstrate that an ancestral form of C. ocellatus, which expanded in northwestern Africa at the end of Miocene, diverged in at least three separate evolutionary lineages approximately 4.57Ma: C. humilis spread south of the Sahara, while the other two (C. ocellatus sensu stricto) were restricted in the coastal North African region. The complicated history of the ocellated skink is a result of multiple vicariant phenomena followed by multiple active or passive dispersals. The Messinian salinity crisis and the re-flooding of the Mediterranean basin, the climatic transition from Middle to Upper Pliocene, and the hyperarid phase of the Sahara, affected the distribution and diversification of C. ocellatus, while in historical times it was introduced in the central Mediterranean islands and eastern Mediterranean region from Tunisia and Cyrenaica, respectively.