Browsing by Author "Viard, Frederique"

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    Microsatellite evidence for sperm storage and multiple paternity in the marine gastropod Crepidula coquimbensis
    (ELSEVIER SCIENCE BV, 2011) Brante, Antonio; Fernandez, Miriam; Viard, Frederique
    In gregarious species with copulation and internal fertilization, male-male competition and female cryptic choice may affect reproductive success of both sexes. We carried out a molecular analysis to study paternity and sperm use by females in the protandrous marine brooding gastropod Crepidula coquimbensis. In the field, a single female inhabits an empty hosting shell with up to six males. This gregarious behavior may promote intra-brood multiple paternity if females can store sperm from several consecutive copulations with the surrounding males. To study female sperm usage, the males sharing shelters with five different adult females were collected and preserved for paternity analysis. Females were transported alive to the laboratory and isolated for six months. After that, an additional male was offered to each of the five study females. Once the females had laid capsules, a total of 528 embryos from the five females were assigned paternity based on five microsatellite loci. Paternity analysis showed that every male sharing the empty hosting shell of a female as well as the additional male were assigned fatherhood of embryos laid by this specific female. Females can thus use sperms from multiple males including sperms stored for at least six months. In addition, in four out of the five offspring arrays, a similar contribution of each male to the brood was observed, a pattern associated with the close relationship between the number of fathers observed and the effective paternity index calculated. These results contrast with those of paternity analyses carried out in another species of the same genus. C. fornicata which is characterized by a stacking behavior in which the closest male to the female achieves the highest reproductive success. Male reproductive success may be largely influenced by the aggregation pattern and male mating opportunities in the Crepidula complex, a hypothesis to be examined further by studying other species exhibiting different grouping behavior. (C) 2010 Elsevier B.V. All rights reserved.
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    Phylogeography and Biogeography Concordance in the Marine Gastropod Crepipatella dilatata (Calyptraeidae) along the Southeastern Pacific Coast
    (OXFORD UNIV PRESS INC, 2012) Brante, Antonio; Fernandez, Miriam; Viard, Frederique
    The biogeography and phylogeography concordance hypothesis suggests that the same factors, for instance physical barriers or environmental gradients, shape both species assemblages and intraspecific genetic structure. In the marine realm, previous studies have however suggested that phylogeographic patterns are also explained by the life-history strategy of the species. However, evidence is contradictory and comes mainly from the northern hemisphere, which is characterized by specific environmental conditions and evolutionary histories of species. In this work, we evaluated the concordance hypothesis in the southern Pacific using the marine gastropod Crepipatella dilatata as a case study. This intertidal species with direct development exhibited a restricted dispersal potential, a feature that contrasts with previous species studied in the same area. Using the gene cytochrome oxidase I, we analyzed 253 individuals sampled at 10 locations covering 543 km of the coast of Chile. The study sites also incorporated 2 biogeographic regions separated by a well-studied biogeographic break (at 30 degrees S). Populations of C dilatata displayed a high degree of genetic structure and a perfect match between phylogeographic and biogeographic breaks at 30 degrees S. When comparing our data with previous research over the same geographic range, life history traits related to dispersal ability seem to be a good proxy for explaining the concordance between biogeography and phylogeography along the southeastern pacific coast. In addition, in this and other marine invertebrate species, gene flow limitations across both sides of the 30 degrees S break may act as a driver of the speciation process.