RESUMO
Ancient lakes are renowned for their exceptional diversity of endemic species. As model systems for the study of sympatric speciation, it is necessary to understand whether a given hypothesized species flock is of monophyletic or polyphyletic origin. Here, we present the first molecular characterization of the Hyalella (Crustacea: Amphipoda) species complex of Lake Titicaca, using COI and 28S DNA sequences, including samples from the connected Small and Large Lakes that comprise Lake Titicaca as well as from a broader survey of southern South American sites. At least five evolutionarily distant lineages are present within Lake Titicaca, which were estimated to have diverged from one another 12-20 MYA. These major lineages are dispersed throughout the broader South American Hyalella phylogeny, with each lineage representing at least one independent colonization of the lake. Moreover, complex genetic relationships are revealed between Lake Titicaca individuals and those from surrounding water bodies, which may be explained by repeated dispersal into and out of the lake, combined with parallel intralacustrine diversification within two separate clades. Although further work in deeper waters will be required to determine the number of species present and modes of diversification, our results strongly indicate that this amphipod species cloud is polyphyletic with a complex geographic history.
Assuntos
Anfípodes/fisiologia , Lagos , Anfípodes/genética , Animais , Teorema de Bayes , Biodiversidade , Intervalos de Confiança , Especiação Genética , Geografia , Funções Verossimilhança , Filogenia , Especificidade da Espécie , Simpatria , Fatores de TempoRESUMO
We present new records of Boeckella bergi at several water bodies in Argentina and Brazil. Within these records the northernmost and southernmost limits of occurrence of B. bergi in South America are included. The ample range of distribution is consistent with former studies, but it is more extensive than previously known. Observations on habitat preferences are also made. This species is tolerant to temperate climate conditions in this region of South America, with wide amplitude of temperature between summer and winter seasons, and irregular patterns of precipitation.
No presente artigo são apresentados novos registros de Boeckella bergi em vários corpos de água na Argentina e no Brasil. Dentro desses registros estão incluídos os limites setentrionais e meridionais de ocorrência de B. bergi na América do Sul. A ampla gama de distribuição é consistente com estudos anteriores, mas se mostra muito mais extensa do que conhecida anteriormente. Observações sobre a taxonomia e os habitats também são feitas. Esta espécie é tolerante a condições de clima temperado na região da América do Sul, com uma grande amplitude de temperatura entre o verão e inverno, e padrões irregulares de precipitação.
RESUMO
The copepod family Centropagidae is widely distributed and occurs in marine, estuarine, freshwater, and inland saline settings. Molecular phylogenies based upon the 16S and 28S genes demonstrate a complex biogeographic history, involving at least five independent invasions of continental waters from the sea. The first colonization was ancient, likely into part of Gondwanaland, and resulted in an inland radiation in southern genera via both vicariance and subsequent habitat shifting among different types of continental waters. Species occupying saline lakes are nested within freshwater clades, indicating invasion of these habitats via fresh waters rather than directly from the ocean or from epicontinental seas. In contrast with the great southern clade, all of the remaining continental invasions are northern, species poor, and quite recent, perhaps even Pleistocene. Long-lived evolutionary euryhalinity, a high propensity for inland invasion, continental vicariance, and in situ radiation within single continents have all played major roles in the diversification of the centropagids.
