Genetic differentiation among populations of the blackfin goodea Goodea atripinnis (Cyprinodontiformes: Goodeidae): implications for its evolutionary history.

Central Mexico is characterized by a complex topography that is the result of historic and contemporary tectonic and climatic factors. These events have influenced the evolutionary history of numerous freshwater fishes in the region. Nonetheless, recent studies have shown that life-history traits and ecological characteristics of species may influence dispersal capabilities and the degree of genetic connectivity. Goodea (Cyprinodontiformes: Goodeidae) is one of the most widely distributed and environmentally tolerant genera of goodeids. In this study, the authors analysed variation in the mitochondrial cytochrome b gene to evaluate the phylogeographic relationships, genetic structure, genetic diversity and demographic history of Goodea from across its distribution range. They found low genetic differentiation and identified shared haplotypes among several regions. Geographic segregation was found in samples southwest and northeast of the Lower Lerma region, with some internal isolated groups showing phylogeographic differentiation and unique haplotypes. The AMOVA best explained genetic structure when grouped by haplogroups rather than when grouped by recognized biogeographic regions. Several regions showed null genetic diversity, raising the possibility of dispersal mediated by humans. Finally, Bayesian Skyline Plot analysis showed a population expansion for the Southwest haplogroup, except for the Armería population and sub-group II of the Northeast haplogroup. All this suggests a recent colonization of Goodea atripinnis throughout some of the biogeographic regions currently inhabited by this species.

Diversification of the genus Apogon (Lacepède, 1801) (Apogonidae: Perciformes) in the tropical eastern Pacific.

We examined the role of geographic barriers and historical processes on the diversification of Apogon species within the tropical eastern Pacific (TEP). Mitochondrial and nuclear DNA sequences were used in Bayesian and Maximum likelihood analyses to generate a phylogenetic hypothesis for Apogon species. Bayesian inferences were used to date the cladogenetic events. Analyses with BioGeoBEARS were conducted to reconstruct the biogeographic history and ancestral ranges. The phylogenetic results show a monophyletic clade of TEP Apogon species with A. imberbis from the eastern Atlantic as sister species. The two lineages diverged during the Miocene. Within the TEP clade, two subclades diverged at around 11.1 million years ago (Mya): one clusters the coastal continental species (A. pacificus, A. retrosella and A. dovii), and the second clusters the oceanic island species (A. atradorsatus, A. atricaudus and A. guadalupensis). The estimated diversification times of these subclades were 9.8 and 7.1 Mya, respectively. Within each subclade, species divergences occurred during the Pliocene-Pleistocene epochs. The divergent event between the Atlantic A. imberbis and Apogon TEP clade corresponds to the first closure event of the Central American Seaway. The biogeographic history of Apogon within the TEP appears to be the result of vicariant, dispersal and founder events that occurred during the last 11 million years. The vicariant and dispersal events occurred along the mainland and were associated with the origin of the Central American Gap. The founder events could have allowed the invasion of Apogon to TEP island areas and could have been driven by ancient warming oceanic waters, changes in circulation of marine currents, and the presence of seamounts in ancient marine ridges that allowed the settlement of marine biota. These factors may have allowed Apogon lineages to cross the TEP biogeographic barriers at different times, with subsequent genetic isolation.

Evolving in the highlands: the case of the Neotropical Lerma live-bearing Poeciliopsis infans (Woolman, 1894) (Cyprinodontiformes: Poeciliidae) in Central Mexico.

BACKGROUND: Volcanic and tectonic activities in conjunction with Quaternary climate are the main events that shaped the geographical distribution of genetic variation of many lineages. Poeciliopsis infans is the only poeciliid species that was able to colonize the temperate highlands of central Mexico. We inferred the phylogenetic relationships, biogeographic history, and historical demography in the widespread Neotropical species P. infans and correlated this with geological events and the Quaternary glacial-interglacial climate in the highlands of central Mexico, using the mitochondrial genes Cytochrome b and Cytochrome oxidase I and two nuclear loci, Rhodopsin and ribosomal protein S7. RESULTS: Populations of P. infans were recovered in two well-differentiated clades. The maximum genetic distances between the two clades were 3.3% for cytb, and 1.9% for coxI. The divergence of the two clades occurred ca. 2.83 Myr. Ancestral area reconstruction revealed a complex biogeographical history for P. infans. The Bayesian Skyline Plot showed a demographic decline, although more visible for clade A, and more recently showed a population expansion in the last 0.025 Myr. Finally, the habitat suitability modelling showed that during the LIG, clade B had more areas with high probabilities of presence in comparison to clade A, whereas for the LGM, clade A showed more areas with high probabilities of presence in comparisons to clade B. CONCLUSIONS: Poeciliopsis infans has had a complex evolutionary and biogeographic history, which, as in other co-distributed freshwater fishes, seems to be linked to the volcanic and tectonic activities during the Pliocene or early Pleistocene. Populations of P. infans distributed in lowlands showed a higher level of genetic diversity than populations distributed in highlands, which could be linked to more stable and higher temperatures in lowland areas. The fluctuations in population size through time are in agreement with the continuous fluctuations of the climate of central Mexico.