Phylogenetic convergence and multiple shell shape optima for gliding scallops (Bivalvia: Pectinidae)

An important question in evolutionary biology is how often, and to what extent, do similar ecologies elicit distantly related taxa to evolve towards the same phenotype? In some scenarios, the repeated evolution of particular phenotypes may be expected, for instance when species are exposed to common selective forces that result from strong functional demands. In bivalved scallops (Pectinidae), some species exhibit a distinct swimming behaviour (gliding), which requires specific biomechanical attributes to generate lift and reduce drag during locomotive events. Further, a phylogenetic analysis revealed that gliding behaviour has independently evolved at least four times, which raises the question as to whether these independent lineages have also converged on a similar phenotype. Here, we test the hypothesis that gliding scallops display shell shape convergence using a combination of geometric morphometrics and phylogenetic comparative methods that evaluate patterns of multivariate trait evolution. Our findings reveal that the gliding species display less morphological disparity and significant evolutionary convergence in morphospace, relative to expectations under a neutral model of Brownian motion for evolutionary phenotypic change. Intriguingly, the phylomorphospace patterns indicate that gliding lineages follow similar evolutionary trajectories to not one, but two regions of morphological space, and subsequent analyses identified significant differences in their biomechanical parameters, suggesting that these two groups of scallops accomplish gliding in different ways. Thus, whereas there is a clear gliding morphotype that has evolved convergently across the phylogeny, functionally distinct morphological subforms are apparent, suggesting that there may be two optima for the gliding phenotype in the Pectinidae.J. M. Serb, E. Sherratt, A. Alejandrino & D. C. Adam

Echinodermata das praias de Salvador (Bahia, Brasil) The Echinoderms of Salvador beaches (Bahia, Brazil)

<abstract language="eng">This paper presents 28 species of Echinoderms collected on 5 beaches of Salvador (12º54' to 13º01' S and 38º26' to 38º33' W), Brazil, which are distributed in 19 families. Ophiuroidea represented 53,6% of the collected species, followed by Echinoidea (28,6%), Asteroidea (7,1%), Holothuroidea (7,1%), and Crinoidea (3,6%). Ophiuroidea and Echinoidea were the most frequent groups, occurring at all the studied beaches while Crinoidea occurred only on 20% of them. Most of the species are characterized as belonging to the tropical warm waters, some to the shallow coastal areas and some having a broad bathymetric distribution. The richness of species values on beaches ranged from 7 to 24, at Itapua Beach, and from 2 to 14 among different kinds of habitats, where protected ones showed higher values