Carla Ibañez

Characterization of ten polymorphic microsatellite loci in the Andean pupfish Orestias agassizii , with cross-amplification in the sympatric O. luteus

We describe the isolation and characterization of ten polymorphic microsatellite loci in the Andean pupfish Orestias agassizii. The number of alleles per locus in 25 individuals was high, varying from 5 to 25. Observed and expected mean heterozygosities were 0.750 and 0.767, respectively. The ten loci conformed to the Hardy–Weinberg equilibrium, and we did not detect linkage disequilibrium between loci. Cross-species amplification in O. luteus was entirely successful, and polymorphism was detected in all loci. One locus (A116) showed significant departure from Hardy–Weinberg equilibrium due to homozygote excess. These microsatellites will be useful for assessing the genetic structure and historical demography of Andean pupfishes, which are subject to a global collapse of their stocks.

The Hyalella (Crustacea: Amphipoda) species cloud of the ancient Lake Titicaca originated from multiple colonizations

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.