Past connection and isolation of Rineloricaria (Siluriformes: Loricariidae) across southeastern Brazilian coastal drainages: evidence for palaeodrainage connectivity and description of a new species

Abstract

Abstract Pleistocene marine transgressions and regressions repeatedly inundated and exposed the Southeastern Brazilian coast, creating alternating phases of connectivity and isolation among adjacent river drainages, that may have structured freshwater fish diversification. We integrate mitochondrial (COI, CytB) and nuclear (RAG1) sequence data with multivariate morphometrics to evaluate the phylogeographic relationships among populations historically identified as Rineloricaria steindachneri across the lower Paraíba do Sul basin and neighboring coastal drainages of Espírito Santo; and to evaluate whether patterns are consistent with the hypothesis that Pleistocene sea-level oscillations were the primary driver of genetic diversification. Molecular analyses recovered two well-supported, allopatric lineages that are independently diagnosable by morphology: R. steindachneri restricted to the Paraíba do Sul basin, and Rineloricaria capixaba n. sp.occurring in the Itabapoana, Itapemirim, and Benevente basins. The two lineages show a mean COI divergence of 2.0%, with largely basin-specific mitochondrial haplotypes, including a COI haplotype shared between Itapemirim and Benevente. Nuclear haplotype sharing is consistent with incomplete lineage sorting. Our findings support a history of intermittent inter-basin connectivity during marine regressions followed by vicariant isolation associated with subsequent transgressions, yielding the present allopatric distributions.