The role of dispersal of repetitive DNAs in the diversification of bristlenose plecos (Loricariidae, Hypostominae, Ancistrus) from South Atlantic Coastal drainages.

Abstract

Sea-level changes during the Pleistocene and the geomorphological history have largely molded the intricate shaping of coastal drainages in Eastern South America. Therefore, freshwater fishes from this region are promising models to infer how riverine isolation and reconnections affected their genetic diversification and geographic distribution. In the present study, we provided a detailed cytogenomic analysis of Ancistrus multispinis and Ancistrus brevipinnis, including the physical mapping of repetitive DNA classes, to verify whether chromosome differentiation would be related to the split between two major watersheds in Southern Brazil. Both species of Ancistrus shared the same modal diploid number (2n=52) and karyotype formulae (14 metacentric, 8 submetacentric and 30 subtelo/acrocentric chromosomes), besides single and terminal 18S ribosomal cistrons, (CGG)10 microsatellite sequences interspersed with heterochromatin in nucleolar organizer regions and a dispersed content of (AC)15 and (GT)15 microsatellites. In turn, the patterns of heterochromatin distribution, number of (GAG)10 microsatellites and 5S rDNA clusters diverged between both taxa. Most likely, these microstructural differences were determined by independent evolutionary processes, strongly associated to the geographic isolation between watersheds. Furthermore, the mapping of repetitive DNAs revealed a dynamic reorganization of genomes of Ancistrus, being useful for the taxonomic disambiguation in this complex group of Neotropical fish.