Connectivity, neutral theories and the assessment of species vulnerability to global change in temperate estuaries

One of the main adaptation strategies to global change scenarios, aiming to preserve ecosystem functioning and biodiversity, is to maximise ecosystem resilience. The resilience of a species metapopulation can be improved by facilitating connectivity between local populations, which will prevent demographic stochasticity and inbreeding. The objective of this investigation is to estimate the degree of connectivity among estuarine species along the north-eastern Iberian coast, in order to assess community vulnerability to global change scenarios. To address this objective, two connectivity proxy types have been used based upon genetic and ecological drift processes: 1) DNA markers for the bivalve cockle (Cerastoderma edule) and seagrass Zostera noltei, and 2) the decrease in the number of species shared between two sites with geographic distance; neutral biodiversity theory predicts that dispersal limitation modulates this decrease, and this has been explored in estuarine plants and macroinvertebrates. Results indicate dispersal limitation for both saltmarsh plants and seagrass beds community and Z. noltei populations; this suggests they are especially vulnerable to expected climate changes on their habitats. In contrast, unstructured spatial pattern found in macroinvertebrate communities and in C. edule genetic populations in the area suggests that estuarine soft-bottom macroinvertebrates with planktonic larval dispersal strategies may have a high resilience capacity to moderate changes within their habitats. Our findings can help environmental managers to prioritise the most vulnerable species and habitats to be restored

Genetic variation within Symbiodinium clade B from the coral genus Madracis in the Caribbean (Netherlands Antilles)

The internal transcribed spacer (ITS) region was sequenced in symbiotic dinoflagellates (zooxanthellae) from five morphospecies in the genus Madracis. The phylogeny of the symbionts is congruent with a companion phylogeny of the coral host. Comparison with known clade B symbiont ITS types reveals that M. mirabilis contains the B13 symbiont and that the other morphospecies contain the B7 symbiont. Madracis formosa also contains a previously undescribed type. The B7 and B13 symbionts appear to be highly specific to morphospecies in the genus Madracis. The host specificity between the B13 symbionts and its coral host may be the result of co-evolution of the coral-symbiont association and suggests that the brooding species, M. mirabilis, is reproductively isolated. Microhabitat differentiation associated with light utilization independent of depth is discussed

La stampa cattolica e il fascismo a Venezia negli anni del consenso: «la Settimana Religiosa» di Venezia (1929-38)

Symbiotic dinoflagellates belonging to the genus Symbiodinium (zooxanthellae) play an important role in ecological specialization and physiological adaptation in corals, We examined the diversity and depth distribution of zooxanthellae in 5 morphospecies of Madracis at the Buoy I study-reef on Curacao, Netherlands Antilles, Following earlier studies, we examined length and sequence variation in the D1 and D2 domains of the nuclear rDNA, large subunit (LSU) of Madracis-associated zooxanthellae. Both RFLP and sequence comparisons showed that all 5 Madracis morphospecies host a single type of Symbiodinium belonging to phylogenetic Group B sensu Rowan. No correlation was found between zooxanthellae and habitat depth, The presence of the single, Type-B zooxanthellae in all Madracis morphospecies at Buoy I (and from 3 other biogeographic locations in the Caribbean) suggests that 'generalist' zooxanthellae-coral associations are equally successful over a range of habitats and that adaptations to different light and nutrient regimes are not necessarily dependent on the mix of zooxanthellae types or zonation with depth, as has been shown in the well-studied Montastraea annularis complex and Acropora cervicornis. A review of the current literature on zooxanthellae diversity in scleractinians (including biogeographic sampling for some species) shows that most species appear to harbor only 1 zooxanthellae type and that the 3 types of Symbiodinium (A, B, C sensu Rowan) are found at all depths and are thus potentially always available for acquisition

Shallow genetic divergence and species delineations in the endemic Labeobarbus species flock of Lake Tana, Ethiopia

To assess whether the species distinctions of Lake Tana’s Labeobarbus spp. are supported by genetic information, microsatellite markers were used. A total of 376 Labeobarbus spp., belonging to 24 populations of 11 species from three regions of the lake (north, south and east), were sampled. Eight microsatellite markers were analysed. In general, differences between conspecific populations were smaller than differences between populations of different species. For six species, conspecific populations from different regions in the lake were consistently more similar than populations of other species from the same region. For four species this was not the case, while for one species two populations were similar, but different from the third population. River-spawning species appeared to be more distinct than presumed lake spawners. On the species level, there was a significant correlation between genetic and morphological differentiation, especially in morphological aspects associated with ecological functioning. This suggests that genetic differentiation arose together with adaptive radiation, although the overall genetic differentiation among the Lake Tana Labeobarbus spp. is small