Population Structure of the SW Atlantic Estuarine Crab Neohelice granulata Throughout Its Range: a Genetic and Morphometric Study

Abstract

Phylogeographic patterns of the SW Atlantic estuarine crab Neohelice granulata were examined using mitochondrial DNA cytochrome oxidase I sequences and analyzed together with morphometric data. Specimens were sampled during a 4-year period (2001)(2002)(2003)(2004) from 11 localities encompassing the full distributional range of this species along the SW Atlantic (22°57′ S to 42°25′ S). DNA sequences were obtained from 69 individuals belonging to seven localities, and morphometric variation in 12 continuous characters was analyzed for 646 crabs from ten localities. Strong genetic differentiation, consistent with a pattern of isolation-by-distance, was detected among all localities indicating that gene flow occurs mainly between neighboring populations. Analyses of molecular variance showed genetic subdivision between the southern (Argentina) and the northern (Brazil) sites, suggesting restricted gene flow at a regional scale. The genetic structure of this species could be divided into two distinct groups due to a limited gene flow between southern and northern regions as a consequence of larval dispersal patterns. Coastal currents in the vicinity of the Rio de la Plata likely act as a barrier to dispersal within the species range. Moreover, genetic data indicate that populations of N. granulata might have undergone a northward demographic expansion since the late Pleistocene. The morphometric analysis showed no geographical pattern of morphological differentiation, although there were differences among sampling sites.

Intraspecific variation in carapace morphology among fiddler crabs (Genus Uca) from the Atlantic coast of Brazil

“…Studies on other crab species also suggest that marine populations along the southern coast of Brazil are intimately connected by gene flow (Oliveira-Neto et al 2007, Laurenzano et al 2012. However, other brachyuran species along this coast may exhibit strong genetic differentiation in patterns that indicate isolation-by-distance over about the same length of coastline (Ituarte et al 2012). For fiddler crabs, at least, the absence of demonstrated genetic structure across populations implies that intraspecific variation results from phenotypic plasticity attributed to either epigenetic change (Miner at al.…”

“…Connectivity in turn can influence intraspecific variation both within and among marine populations (Kelly & Palumbi 2010, Sanford & Kelly 2011, Ituarte et al 2012. The division of the major currents at the Ponta do Calcanhar, in particular, may significantly control gene exchange between the northern and southern populations of individual fiddler crab species.…”

Predation risk modifies behaviour by shaping the response of identified brain neurons

“…Moreover, compared with interspecific comparisons, interpopulation comparisons more easily allow the separation of genetic variations from phenotypic plasticity. Populations of N. granulata are restricted to salt marshes separated by hundreds of kilometres and their larvae are unlikely to travel long distances through the ocean (Bas et al, 2010;Ituarte et al, 2012). Thus, the differences found in the intensity of responses to VDS could be genetically determined.…”

Effect of different protein supply on growth of three populations of a crab adapted to low energy diets

“…Adults inhabit intertidal mudflats and marshes, from oligohaline to hyperhaline environments, where they feed mainly on leaves and sediment [3]; its life cycle includes a typical marine planktonic larval development (four zoeae and a megalopa stage). The genetic and morphometric pattern of the species was studied by Ituarte et al [8] in populations along its complete geographical distribution. They found strong genetic differentiation consistent with an isolation-by-distance pattern, with gene flow occurring mainly between neighbor populations.…”

“…1); both habitats differ mainly in vegetation [6] and in granulometry and organic matter content of sediments: substrate was hard in SAO with a high proportion of gravel and scarce organic matter whereas it was soft in RSJ, with twice as silt and clay and higher organic matter content [26]. Both populations appeared as genetically homogeneous but with clear morphological differences [8]. SAO population has been previously studied [2] and compared to Mar Chiquita lagoon (MC, Fig.…”