Opportunity and taxon pulse: the central influence of coastal geomorphology on genetic diversification and endemism of strict estuarine species

Abstract

Aim Sea‐level changes and coastal geomorphology (extension of continental shelves) have affected the pattern of diversification of brackish/freshwater fish populations due to the confluence of basins/estuaries during low sea‐level periods (opportunity) and isolation during high sea‐level periods. It is hypothesized that populations from estuaries in extensive continental shelves, which have greater potential for confluence, should have more opportunities for gene exchange than those in narrow continental shelves. To test this, we assessed the distribution of the genetic diversity and the patterns of diversification of the estuarine silverside, Atherinella brasiliensis, from the Brazilian coast. Location Eight estuaries along the southern and north‐eastern portions of the Brazilian coast. Materials and methods Sequences of the mitochondrial control region (D‐loop) and the cytochrome B were used to assess the distribution of genetic diversity, and these mitochondrial fragments and two nuclear introns were used to assess the patterns of diversification of A. brasiliensis. The palaeochannels that were exposed along the Brazilian coast during the Last Glacial Maximum were reconstructed using bathymetry data and the GIS method. Results The populations of A. brasiliensis from the estuaries of the north‐eastern Brazilian coast (narrower and shallower continental shelf) showed higher levels of genetic differentiation and larger (more haplotypes) endemic lineages than the populations in the southern coast (broader and deeper continental shelf). Furthermore, south coast lineages showed more evidence of genetic exchange among populations, which have resulted in a reticulated relationship between lineages and estuaries. The reconstruction of palaeochannels revealed more connections among southern than north‐eastern basins. Main conclusions Our results support the hypothesis that continental shelf extension and sea‐level changes have influenced the diversification of A. brasiliensis. By extension, they also support the hypothesis of diversification by taxon pulse, which makes predictions based on the opportunities for expansion during periods of low sea level and the width of the continental shelf. We suggest this as a model for the genetic diversification and distribution of estuarine species along the Brazilian coast and other regions of the world.

Population genetics reveals global and regional history of the apex predator Galeocerdocuvier (carcharhiniformes) with comments on mitigating shark attacks in north‐eastern brazil

“…Global temperature increasing events are indicated during the Holocene (11.300 years until present) in tropical zones (Marcott et al, 2013), and their effects can cause significantly important oscillations in the demography and in the population genetics of many species including tiger sharks as observed herein. These signs of Ne oscillations over time have been demonstrated at several different species (Torres & Ribeiro, 2009;Von der Heyden et al, 2011;der Heyden et al, 2013;Teske et al, 2013;Lima et al, 2016;Baggio et al, 2017;Machado et al, 2017). Despite the occasional capability on reaching temperatures below 15°C, tiger sharks seem to prefer warmer waters.…”

Flowing into the unknown: inferred paleodrainages for studying the ichthyofauna of Brazilian coastal rivers

“…For example, using a paleodrainage reconstruction for the southeastern coast of Brazil, it was demonstrated that paleodrainages and its properties account for most of the genetic variation and diversity observed for the characid genus Hollandichthys based on mitochondrial DNA (Thomaz et al, 2015) and next generation sequencing data (Thomaz et al, 2017). Likewise, analyses that took into consideration fluctuations on sea level suggests its role in structuring genetic divergence and demographic history of other members of the coastal ichthyofauna (Baggio et al, 2017;Hirschmann et al, 2017;Lima et al, 2017;Ramos-Fregonezi et al, 2017;Tschá et al, 2016Tschá et al, , 2017.…”

“…Here we provide reconstructions of paleodrainages using GIS technologies for the eastern coast of Brazil, and for a few basins in the northeast and south. Together they represent a significant expansion over the information to date, which is limited to a local analysis of paleodrainages (Dias et al, 2014;Thomaz et al, 2015; and of proposed paleo-connections among a set of specific Brazilian river basins (Baggio et al, 2017;Lima et al, 2017). We also characterize general properties of the inferred paleodrainages, including the geographic area spanned by each paleodrainage and the number of contemporary river basins associated with individual paleodrainages.…”

Getting somewhere with the Red Queen: chasing a biologically modern definition of the hypothesis

“…Evidence from a variety of sources [45][46][47][48][49][50][51] uphold abiotic factors as important drivers of evolution and speciation. This has led to proposed alternatives to the RQH which focus on the physical environment as the main driver of evolution.…”