Cryptic speciation in the vermilion rockfish (Sebastes miniatus) and the role of bathymetry in the speciation process

Abstract

A recent phylogenetic review of the genus Sebastes suggested the existence of a cryptic species of vermilion rockfish (Sebastes miniatus). To evaluate the geographical and bathymetric range of the Type 1 and Type 2 forms reported in that study, cytochrome b sequences were examined from 548 fish. Type 1 fish were found primarily south of Point Conception on reefs deeper than 100 m. Type 2 fish were common range-wide at sites shallower than 100 m. Reproductive isolation between the two types was tested using nine microsatellite loci. Estimates of genetic divergence were made using the fixation index (F(ST)) and correspondence between haplotype and genotype was tested by Bayesian population assignment and multivariate plotting of individual genotypes. Microsatellite analyses gave strong support for the presence of two distinct groups of genotypes. All fish with Type 1 haplotypes and fish with Type 2 haplotypes from < 100 m depth had genotypes unique to their haplotype group. However, most (68%) fish with Type 2 haplotypes from > 100 m depth assigned strongly to the Type 1 genotype group. Morphometric comparisons between the two genotypic groups revealed significant differences at three of the six examined measurements. Differences in both genetics, depth of occurrence, and morphology suggest these are separate species. This observation along with evidence of depth segregation in many recent species pairs led us to hypothesize a speciation model for Sebastes spp. by which the loss or truncation of a depth-related ontogenetic migration can lead to the creation of reproductively isolated populations.

Pleistocene genetic legacy suggests incipient species of Sebastes mentella in the Irminger Sea

“…In this way, reproductive isolation between the redfish morphotypes could have evolved, or at least been initiated as a byproduct of genetic drift and the pleiotropic effects of adaptation within different glacial refuges (Dobzhansky, 1937). These results, which suggest historical separation, seems to contrast with findings on vermilion rockfish (S. miniatus) in which differentiation arising from loss of ontogenetic depth migration is hypothesized (Hyde et al, 2008).…”

How many species of goliath grouper are there? Cryptic genetic divergence in a threatened marine fish and the resurrection of a geopolitical species

“…Failure to recognize these cryptic partitions, which often reflect reduced demographic connectivity, can impact the way in which populations are managed (Rocha et al 2007). In the marine environment, unforeseen genetic structure has been elucidated across enumerable taxa from rockfishes (Hyde et al 2008) to copepods (Goetz 2003) to bryozoans (Davidson & Haygood 1999). Our results add another layer to this complexity by adding an exceptionally large and well-studied marine fish to the list of genetically partitioned species.…”

Speciation along a depth gradient in a marine adaptive radiation

“…Divergence in depth may result from multiple, not mutually exclusive processes. Rockfishes recruit from the plankton to shallow [18]. Individuals may also recruit to new depth habitats created by sea level fluctuations [16].…”

“…Species occupy characteristic depth habitats ranging from the intertidal to more than 600 m [17], and the relatively low overlap of sister species' depth distributions (figure 1) is suggestive of parapatric speciation on a depth gradient [18]. Rockfish species also show extensive a-niche diversity, some feeding primarily on zooplankton and others consuming mostly benthic invertebrates or fish [17].…”