adaptive traits are maintained on steep selective gradients despite gene flow and hybridization in the intertidal zone自适应特征是维护在陡峭的选择性梯度尽管基因流动和杂交在潮间带.pdfVIP

Adaptive Traits Are Maintained on Steep Selective Gradients despite Gene Flow and Hybridization in the Intertidal Zone . . ˜ Gerardo I. Zardi , Katy R. Nicastro* , Fernando Canovas, Joana Ferreira Costa, Ester A. Serrao, Gareth A. Pearson ´ CCMAR-CIMAR Laboratorio Associado, Universidade do Algarve, Gambelas, Faro, Portugal Abstract Gene flow among hybridizing species with incomplete reproductive barriers blurs species boundaries, while selection under heterogeneous local ecological conditions or along strong gradients may counteract this tendency. Congeneric, externally- fertilizing fucoid brown algae occur as distinct morphotypes along intertidal exposure gradients despite gene flow. Combining analyses of genetic and phenotypic traits, we investigate the potential for physiological resilience to emersion stressors to act as an isolating mechanism in the face of gene flow. Along vertical exposure gradients in the intertidal zone of Northern Portugal and Northwest France, the mid-low shore species Fucus vesiculosus, the upper shore species Fucus spiralis, and an intermediate distinctive morphotype of F. spiralis var. platycarpus were morphologically characterized. Two diagnostic microsatellite loci recovered 3 genetic clusters consistent with prior morphological assignment. Phylogenetic analysis based on single nucleotide polymorphisms in 14 protein coding regions unambiguously resolved 3 clades; sympatric F. vesiculosus, F. spiralis, and the allopatric (in southern Iberia) population of F. spiralis var. platycarpus. In contrast, the sympatric F. spiralis var. platycarpus (from Northern Portugal) was distributed a