Amaia Autor has recently finished her MSc in Zoology at Complutense University of Madrid. She is giving the first step toward research by trying to publish a work about extra-pair paternity in blue tits (directed by Santiago Merino and Elisa Perez of MNCN-CSIC) and by the work presented here about the inter-specific differences between two species of clams
Clams (genus Ruditapes) constitute one important component of infaunal macrobenthic communities in coastal areas. Coexistence of two species–the native clam (R. decussatus) and the Manila clam (R. philippinarum) introduced some decades ago for commercial purposes in the intertidal zone along the Atlantic coast, poses the question of resource partitioning among populations of both species since these clams share a common filter – feeding mechanism. In this study, two main physiological components of the individual energy balance–filtration and metabolic rates were determined in these clams in order to ascertain whether differences in physiological behavior accounted for higher rates of growth reported in the introduced species (FAO reports). To cover growth trajectories, measurements were performed for a wide size-range of clams and physiological rate determinations formalized through allometric size-scaling relationships. Comparisons of allometric equations using ANCOVA showed lack of significant inter-specific differences in size exponents for either filtration or metabolic rates. Concerning the intercepts, differences were found no-significant for metabolic rates while intercept for filtration rates was significantly higher in R. decussatus. Thus, results do not support the expectation of higher filtration in the introduced species as inferred from their higher rates of growth reported. However, present filtration rates were based on active filtering individuals and complementary information concerning cycles of activity in both species is needed in order to achieve environmentally realistic assessments of energy acquisition
Carlos de la Cruz is a student of the 4th year of Biology Degree at the Complutense University in Madrid. The research on phylogeography of plant colonisation processes is the subject of his TFM (Graduation Thesis)
Hypochaeris glabra (Asteraceae) is a plant species originary from Eurasia and North Africa, adapted to the Mediterranean climate. The American colonization by Europeans in the 15th century occasioned the introduction of several herbaceous wild species. Some of these species naturalized in certain areas of Mediterranean climate, establishing mixed pasturelands together with native species – the Chilean “Espinal”. This work is a phylogeographic analysis of several populations from Spain and central Chile using two types of molecular DNA markers: ITS rDNA spacer sequences, and ISSR markers – genomic sequences flanked by tandem repeats. Only one SNP variation was found in the ITS sequences and the polymorphism was present in both continents. Both, the ITS sequences and the ISSR markers reflect a reduction in variability after colonization. Three main groups were defined according to geographical origin: Populations from northern Spain, populations from southern Spain, and Chilean populations (Chile). AMOVA analyses using different partitions indicate a certain degree of genetic differentiation between continents, and between groups, although most variation lies within populations and between populations within groups. Structure analysis of the ISSR markers indicated also a differentiation between continents, although certain Spanish populations show a close relationship with Chilean ones. No significant correlation between geographical and genetic distances was found when Mantel tests were applied, however, significant positive correlations were found between genetic distances and distances calculated from different ecological parameters. This supports a pattern of differentiation by environment rather than by distance.