Temporal genetic variation in subpopulations of bicolor damselfish (Stegastes partitus) inhabiting coral reefs in the Florida Keys

Abstract

Abstract. In 1986 we observed significant genetic heterogeneity among samples of bicolor damselfish (Stegastes partitus) from geographically proximate coral reefs in the Florida Keys. This result was in contrast to results of virtually all previous studies of coral reef fishes. To assess temporal stability of localized genetic differentiation, we resampled reefs in 1989. Within approximately two generations, allele frequencies at the most differentiated locus, ACO-I*, had changed by as much as 0.65, resulting in almost complete homogeneity between previously differentiated subpopulations. Estimates of 10.78 migrants per generation suggested that high gene flow is the most likely factor responsible for the significant change in allele frequencies. We attribute the original genetic differentiation to a population bottleneck, possibly caused by environmental perturbations such as hurricanes and consequent genetic drift. For reef fishes with pelagic egg and/ or larval stages, a growing body of data suggests that: (1) populations are geographically extensive gene pools, and (2) rates of dispersal appear to be high enough to allow for continual repopulation of isolated and/or perturbed coral reef communities.

Variability in connectivity indicated by chaotic genetic patchiness within and among populations of a marine fish

“…Lacson (1992) found no genetic structure across the entire Caribbean using allozyme markers and OspinaGuerrero et al (2008) found similar results using microsatellite markers in the Colombian-Caribbean. However, other studies found genetic heterogeneity among populations of S. partitus in the Florida Keys (Lacson et al 1989), but the differentiation was attributed to population bottlenecks (Lacson & Morizot 1991). Furthermore, recent microsatellite analyses showed weak population structuring within the Caribbean Antilles (Purcell et al 2009), the Bahamas (Christie et al 2010) and within the western Caribbean (Salas et al 2009).…”

“…However, Hedgecock (1994) compiled evidence across a variety of taxa that supports the sweepstakes hypothesis. Finally, pre-settlement variation in recruit composition driven by the mixing of sub-populations in the plankton (evidence for the variable source hypothesis) was suggested to explain temporal patchiness in haddock (Purcell et al 1996), as well as to explain small-scale variation in Stegastes partitus populations using allozyme and microsatellite markers (Lacson & Morizot 1991, Roberts 1997, Hepburn et al 2009). …”

“…Genetic structure and stability of S. partitus populations has been assessed using variable allozyme markers, and both fine-scale population structuring and temporal instability were demonstrated (Lacson et al 1989, Lacson & Morizot 1991. However, this population structuring was driven by a single allozyme locus that appeared to be under selection and structuring was attributed to a previous bottleneck event (Lacson & Morizot 1991). Using microsatellite markers, studies have shown both weak population structuring (Hepburn et al 2009, Purcell et al 2009, Salas et al 2009) and panmixia (OspinaGuerrero et al 2008).…”

“…S. partitus is a demersally spawning damselfish common throughout the Caribbean with a larval duration of approximately 30 d. It thus has a moderate to high dispersal capacity and is expected to show limited or no spatial genetic structure. Genetic structure and stability of S. partitus populations has been assessed using variable allozyme markers, and both fine-scale population structuring and temporal instability were demonstrated (Lacson et al 1989, Lacson & Morizot 1991. However, this population structuring was driven by a single allozyme locus that appeared to be under selection and structuring was attributed to a previous bottleneck event (Lacson & Morizot 1991).…”

Experimental induction of neurofibromatosis in bicolor damselfish

“…This is suggested by the lack of significant differences observed in development rates of induced tumors in fish from low compared to high tumor prevalence reefs. Furthermore, studies of population genetics of bicolor damselfish in Florida as well as this and other manne fish species in the Southeast Atlantic region have shown a complete lack of any detectable population substructure throughout the entire Caribbean basin, Florida and the Bahamas (Lacson & Morizot 1991). Thus, there is no evidence to support the involvement of any genetic factors (heritable mechanisms) in DNF.…”