Population structure, fluctuating asymmetry and genetic variability in an endemic and highly isolated Astyanax fish population (Characidae)

Abstract

Morphological and chromosomal markers were used to infer the structure and genetic variability of a population of fish of the genus Astyanax, geographically isolated at sinkhole 2 of Vila Velha State Park, Paraná, Brazil. Two morphotypes types were observed, the standard phenotype I and phenotype II which showed an anatomical alteration probably due to an inbreeding process. Fluctuating asymmetry (FA) analysis of different characters showed low levels of morphological variation among the population from sinkhole 2 and in another population from the Tibagi river (Paraná, Brazil). The Astyanax karyotype was characterized in terms of chromosomal morphology, constitutive heterochromatin and nucleolar organizer regions. Males and females presented similar karyotypes (2n = 48, 6M+18SM+14ST+10A) with no evidence of a sex chromosome system. One female from sinkhole 2 was a natural triploid with 2n = 3x = 72 chromosomes (9M+27SM+21ST+15A). The data are discussed regarding the maintenance of population structure and their evolutionary importance, our data suggesting that Astyanax from the Vila Velha State Park sinkhole 2 is a recently isolated population.

Astyanax aff. fasciatus Cuvier, 1819 (Teleostei; Characidae): evidences of a species complex in the upper rio Tibagi basin (Paraná, Brazil)

“…fasciatus karyotype at Furna 2, previously described by Gross et al (2004), was reanalyzed and its karyotypic structure confirmed, corresponding to cytotype A. In truth, according to previous studies of Matoso et al (2002), this cytotype also characterizes the Astyanax aff.…”

Contribution of conservation genetics in assessing neotropical freshwater fish biodiversity

“…In Astyanax scabripinnis (Jenyns, 1842) inhabiting different small streams, besides extensive chromosome divergences observed between populations (Moreira-Filho and Bertollo, 1991), a significant population differentiation has also been reported through a molecular analysis between putative isolated populations, although the mechanisms (selection and/or genetic drift) responsible for such genetic differentiation remain unknown (Sofia et al, 2006). Moreover, sex ratio deviation seems to be a common occurrence among this fish group and is likely related to behavioral and ecological strategies to quickly occupy the headwaters in which they live (Gross et al, 2004), but may reduce genetic variation by reducing the effective population number (Frankham et al, 2002) and lead to population differentiation.…”

“…Populations structured by habitat fragmentation due to barriers such as roads, dams, waterfalls and climate (drought and rain) have their abundance, dispersal and population size reduced, thereby increasing the risk of extinction (Gross et al, 2004;Letcher et al, 2007). This fragmentation can lead to the total or partial isolation of a population, conditioning the response of the individuals.…”

Karyotypic diversity among three species of the genus Astyanax (Characiformes: Characidae)

“…Astyanax have presented an extensive diversity in the chromosome number and karyotype formula, both intra-and interspecifically, besides the occurrence of B chromosomes and natural polyploidy for some populations (Malacrida et al, 2003;Gross et al, 2004;Kantek et al, 2007;Peres et al, 2009;Santos et al, 2012).…”