Effects of the evolution of the Serra do Mar mountains on the shape of the geographically isolated populations of Aegla schmitti Hobbs III, 1979 (Decapoda: Anomura)

AbstractTrevisan,A.,Marochi,M.Z.,Costa,M.,Santos,S.andMasunari,S.2014.Effectsof the evolution of the Serra do Mar mountains on the shape of the geographicallyisolated populations of Aegla schmitti Hobbs III, 1979 (Decapoda: Anomura). — ActaZool ogica (Stockholm) 00:000–000The Aeglidae family is a useful model for evaluating the shape variation to pres-ent small geographically isolated populations and present a carapace structurethat allows precise placement of landmarks. We analysed variations of the sizeand shape of the carapace of seven populations of A. schmitti. We used 18 bidi-mensional anatomical landmarks on the c arapace of adult males. Size variationbetween the populations was analysed through a univariate analysis of variance,while the shape variation was analysed througha multivariate analysis of varianceusing the configurations aligned by the gene ralized Procrustesanalysis. The ordi-nation of the populations was investigate d through a canonical variables analysis.Individuals from the populations differed in the carapace size, in this case, weobserved the largest individuals in the Iguac u river basin, followed by Ribeira doIguape and the Coastal basin. Carapace shape also differed between the popula-tions of A. schmitti, with the exception of the Mato Grande and Piraquara rivers:populations from the Iguac u River presented a larger and rounder carapacewhen compared withthe slenderer carapaceofthe Coastal basin,and the Ribeirado Iguape animals presented intermediate shapes. Data from the present studyshow great congruency with the draining pattern and geological history of theregion.Andre Trevisan, Departamento de Zoologia, Programa de P os-Graduac ~aoemZoologia, Universidade Federal do Parana. Centro Politecnico,JardimdasAmericas, Caixa Postal 19020, 81531-980, Curitiba, Parana, Brazil.E-mail: trevisan_andre@yahoo.com.br.IntroductionAlong and across its geographical distribution, a species mayface distinct environments and selective pressures, whichmight generate discontinuities on the genotypic and pheno-typic traits between different populations. In geographicallyisolated populations where there is little or no gene flow,mechanisms of directional selection are expected to be morepronounced, increasing the phenotypic variation (Hoffmannand Shirriffs 2002). Phenotypic differentiation between iso-lated populations may occur as a consequence of the fixationof random characters via genetic drift, through the fixation ofadaptive traits promoted by selection or through phenotypicplasticity in response to differ ent environmental pressures(Avise 2000; Blanckenhorn and Demont 2004; DeWitt andScheiner 2004; Hopkins and Thurman 2010). Thus, pheno-typic variation can be considered a reflex of the mechanismsacting on the populations and, within this context, studies onthe shape variation of individuals might demonstrate the mor-phological pattern generated by these mechanisms along aspecies’ geographical distribution (Hopkins and Thurman2010; Lezcano et al. 2012).One way to study the shape variation between populationsis trough geometrical morphom etry (Rohlf and Marcus 1993;