Genetic structure and different color morphotypes suggest the occurrence and bathymetric segregation of two incipient species of Sebastes off Argentina

Abstract

Rockfishes of the genus Sebastes are extensively distributed in the Pacific and Atlantic oceans. Although the occurrence of two morphologically similar species in the Southern Hemisphere, Sebastes oculatus and Sebastes capensis, is now clearly established, the taxonomic status and phylogeographic patterns for the genus in the region have not yet been completely resolved. In this study, we provide new insights into the taxonomy and evolutionary relationships of rockfishes inhabiting the Southwestern Atlantic Ocean, off the coast of mainland Argentina, by combining mitochondrial DNA (mtDNA) control region sequences, microsatellite data, and color pattern analyses. Differences in coloration ("dark" and "light" fish) together with bathymetric segregation between color morphotypes were evident from fish collection and literature review. In addition, the mtDNA phylogenetic analysis and Bayesian clustering analysis using microsatellite data separated the fish into two distinct groups (F ST = 0.041), most likely representing incipient species. Our results suggest that speciation-by-depth in the absence of physical barriers could be a widespread mechanism of speciation in Sebastes from both the Northern and Southern Hemispheres. Nevertheless, the degree of genetic differentiation found, added to the large number of individuals displaying high levels of admixture, points to the occurrence of incomplete reproductive barriers between color morphotypes. Beyond the taxonomic and phylogeographic implications of our findings, the occurrence of distinct groups of Sebastes off the coast of Argentina being targeted by different fisheries (angling and trawling) has consequences for the design and implementation of appropriate fishery regulations to avoid overharvest of either group.

Is the ballan wrasse (Labrus bergylta) two species? Genetic analysis reveals within-species divergence associated with plain and spotted morphotype frequencies

“…unrepresentative sampling, selection acting on the marker loci), a long-term study on coastal Atlantic cod combined genetics and extensive capture-mark-recapture to conclude that the low, and yet highly significant, F ST (average 0.0037) was biologically meaningful as it did correspond to separate temporally persistent local populations (Knutsen et al 2011). The degree of differentiation found in the present study was found to be 5-fold higher and matched, for instance, the one reported for color morphotypes of the rockfish Sebastes oculatus assessed with a suite of 24 microsatellites (Venerus et al 2013). In this case, the genetic differentiation added to the bathymetric segregation between color morphotypes ("dark" and "light" fish) suggested the existence of speciation-by-depth in the absence of physical barriers, although the large number of individuals displaying high levels of admixture invoked incomplete reproductive barriers between color morphotypes.…”

Dispersal of a nearshore marine fish connects marine reserves and adjacent fished areas along an open coast

“…Relationships inferred with the microhaplotype data were further evaluated by genotyping putative parents, offspring and siblings at 25 microsatellite loci (Supporting Information Table ). Twenty‐four of these loci were previously used in population genetic studies of S. oculatus (Venerus et al, ) and S. levis (Hess et al, ), and a subset of these loci were used previously to infer paternity of kelp rockfish larvae (Sogard et al, ). The microsatellite genotyping protocols were adapted from Venerus et al () for fragment analysis on an ABI 3730 capillary sequencer and with allele calling in G ene M apper version 4.0 (Applied Biosystems).…”

Otolith shape lends support to the sensory drive hypothesis in rockfishes

“…It is widely accepted that the morphological variation in otolith shape is the consequence of a synergy between genetic and environmental factors (Lombarte & Lleonart, ; Vignon & Morat, ; Vignon, ). Similarly, it is well known that these environmental factors also had profound effects on the evolution of rockfishes (Ebeling et al ., ; Love & York, ; Love et al ., ; Venerus et al ., ). From these premises, we demonstrate here that both phylogeny and main factors responsible for diversification in rockfishes also have strong effects on the otolith shape.…”