Mito-nuclear discordance in the degree of population differentiation in a marine goby

Abstract

An increasing number of phylogeographic studies on marine species shows discordant patterns in the degree of population differentiation between nuclear and mitochondrial markers. To understand better which factors have the potential to cause these patterns of discordance in marine organisms, a population genetic study was realized on the sand goby Pomatoschistus minutus (Pallas 1770; Gobiidae, Teleostei). Sand gobies from eight European locations were genotyped at eight microsatellite markers. Microsatellites confirmed the global phylogeographical pattern of P. minutus observed with mitochondrial DNA (mtDNA) markers and nuclear allozyme markers. Three groups consistent with the mitochondrial lineages were defined (the Mediterranean, Iberian and North Atlantic groups) and indications of a recent founder event in the northern Baltic Sea were found. Nevertheless, differences in the degree of population differentiation between the nuclear and mitochondrial markers were large (global F ST -values for microsatellites ¼ 0.0121; for allozymes ¼ 0.00831; for mtDNA ¼ 0.4293). Selection, sex-biased dispersal, homoplasy and a high effective population size are generally accepted as explanations for this mitonuclear discrepancy in the degree of population differentiation. In this study, selection on mtDNA and microsatellites, male-biased dispersal and homoplasy on microsatellite markers are unlikely to be a main cause for this discrepancy. The most likely reason for the discordant pattern is a recent demographical expansion of the sand goby, resulting in high effective population sizes slowing down the differentiation of nuclear DNA.

Environmental variables, habitat discontinuity and life history shaping the genetic structure of Pomatoschistus marmoratus

“…The studied populations showed high genetic diversity, with values of expected heterozygosity ranged from 0.67 to 0.79. These levels of genetic variability were also similar to those found in a congeneric species, P. minutus, analyzed with microsatellites markers: 0.74-0.86 , 0.74-0.78 (Larmuseau et al 2010a) and 0.58-0.63 (Boissin et al 2011).…”

“…Departures from Hardy-Weinberg equilibrium (HWE) were found in all Pomatochistus samples, such as were found in P. minutus and P. microps populations by other authors Larmuseau et al 2010a;Marques et al 2012). The most probable causes of HWE departures may be attributed to Wahlund effect due to the recruitment of genetically variable cohorts of larvae (González-Wangüemert et al 2007), inbreeding, null alleles (Horne et al 2011;Milana et al 2012), cryptic species, groupings of relatives, scoring errors or selection against heterozygotes ).…”

“…However, as it was indicated above, other factors as a restricted gene flow, selection events or some mating systems such as polygyny could favor the genetic structuring of fishes. In fact, evidence of genetic differentiation across large and small spatial scales has been reported in a great number of marine fishes using microsatellites Larsson et al 2007;Bradbury et al 2009;Earl et al 2010;González-Wangüemert et al 2010Larmuseau et al 2010a;Horne et al 2011;. These nuclear markers are especially useful to study the fine geographical variation of marine populations because they tend to be highly variable and can discern even subtle genetic differences (Waples 1998;Hedgecock et al 2007), resolving population structures that are not detected by mitochondrial DNA and allozyme markers (De Innocentiis et al 2001;Pampoulie et al 2004;Bisol et al 2007;Canino et al 2010).…”

Invasion genetics of Pacific oyster Crassostrea gigas shaped by aquaculture stocking practices

“…Strong discrepancy between genetic differentiation measured with mitochondrial markers and genetic differentiation measured with nuclear markers has previously been observed for marine species (Larmuseau et al, 2010) demonstrating that processes like sex biased dispersal can influence differentiation estimates. Although mitochondrial discontinuities have been reported for American oysters C. virginica (Reeb and Avise, 1990) selectively neutral autosomal markers are unlikely to reveal different patterns of genetic differentiation, because oysters are hermaphrodites making sex-biased dispersal unlikely for Pacific oysters.…”

Multi-marker estimate of genetic connectivity of sole (Solea solea) in the North-East Atlantic Ocean

“…Although a number of population genetic studies found evidence for structure even in species with high dispersal potential (Jørgensen et al 2005;Knutsen et al 2003;Larmuseau et al 2009b;Nielsen et al 2004;Pampoulie et al 2004), measuring genetic connectivity in marine environments without any obvious physical barriers remains a challenge. Besides high levels of gene Xow, other factors such as recent recolonization events and high eVective population size could explain the lack of detectable genetic diVerentiation at neutral loci (Buonaccorsi et al 2001;Larmuseau et al 2010a). On the other side, many marine species with type III survival curves show a more chaotic pattern in their genetic constitution, termed genetic patchiness, resulting from a large variance in reproductive success among parents (Pujolar et al 2006;Selkoe et al 2010).…”