Abstract
During the Pleistocene and Holocene, the southwest Andean Altiplano (17°-22°S) was affected by repeated fluctuations in water levels, high volcanic activity and major tectonic movements. In the early Holocene the humid Tauca phase shifted to the arid conditions that have lasted until the present, producing endorheic rivers, lakes, lagoons and wetlands. The endemic fish Orestias (Cyprinodontidae) represents a good model to observe the genetic differentiation that characterizes an incipient speciation process in allopatry since the morphospecies described inhabit a restricted geographic area, with present habitat fragmentation. The genetic diversity and population structure of four endemic morphospecies of Orestias (Cyprinodontidae) found in the Lauca National Park (LNP) analyzed with mitochondrial markers (Control Region) and eight microsatellites, revealed the existence of genetic groups that matches the fragmentation of these systems. High values of genetic and phylogeographic differentiation indices were observed between Chungará Lake and Piacota lagoon. The group composed of the Lauca River, Copapujo and Chuviri wetlands sampling sites showed a clear signal of expansion, with a star-like haplotype network. Levels of genetic differentiation were lower than in Chungará and Piacota, suggesting that these localities would have differentiated after the bottlenecks linked to the collapse of Parinacota volcano. The Parinacota sample showed a population signal that differed from the other localities revealing greater genetic diversity and a disperse network, presenting haplotypes shared with other LNP localities. A mixing pattern of the different genetic groups was evident using the microsatellite markers. The chronology of the vicariance events in LNP may indicate that the partition process of the Orestias populations was gradual. Considering this, and in view of the genetic results, we may conclude that the morphospecies from LNP are populations in ongoing differentiation process.
Highlights
Speciation is a continuous process during which differentiation and reproductive isolation are established [1]
Our results showed the existence of various genetic groups in the localities of the Lauca National Park (LNP) that coincide with the fragmentation of the aquatic systems due to the volcanic and climate events that originated closed systems such as Lago Chungaraand the Piacota lagoon [37, 38]
In spite of the genetic and phylogeographic differentiation detected in this study, up to now there is no evidence of reproductive isolation
Summary
Speciation is a continuous process during which differentiation and reproductive isolation are established [1]. The family Cichlidae is the classical model to study an adaptive radiation and diversification in lake systems [20,21] One example of this group is haplochromine cichlids from the Lake Victoria region in Africa, where there are species with low genetic differentiation but with different morphological characteristics. Barluenga & Meyer [7] studied the speciation processes of the Midas cichlid in the lakes of Nicaragua; they found that the large lakes had genetically more ancestral populations, while species ensembles that inhabit crater lakes were younger and had less genetic variation. In spite of their recent origin (
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