Microhabitat use and diet of 0+ cyprinid fishes in a lentic, regulated reach of the River Great Ouse, England

In the River Great Ouse, 0+ roach, bream, chub, bleak and gudgeon were each divided into three' ecospecies' on the basis of their morphology: young larvae, old larvae and juveniles. Ecologically similar species were positively associated and dissimilar species were negatively associated. All ecospecies, except juvenile bleak preferred water < 1 m deep, within 6 m of the bank with some plant cover. Habitat use was similar for all species. It is suggested that this habitat offers increased growth rate, reduced predation risk and increased food abundance to all species, and that species overlap is due to complementary habitat use rather than aggregation. During the early larval period all species fed predominantly upon rotifers and diatoms. During the late larval period there was a switch to Cladocera, primarily Chydoridae and Ceriodaphnia sp., and chironomid larvae. Species-specific dietary selection was evident during the juvenile period, with roach feeding primarily upon aufwuchs, bream upon Cladocera, chub upon Diptera, and gudgeon upon Copepoda.     

Influence of learning on range expansion and adaptation to novel habitats

Learning has been postulated to ‘drive’ evolution, but its influence on adaptive evolution in heterogeneous environments has not been formally examined. We used a spatially explicit individual‐based model to study the effect of learning on the expansion and adaptation of a species to a novel habitat. Fitness was mediated by a behavioural trait (resource preference), which in turn was determined by both the genotype and learning. Our findings indicate that learning substantially increases the range of parameters under which the species expands and adapts to the novel habitat, particularly if the two habitats are separated by a sharp ecotone (rather than a gradient). However, for a broad range of parameters, learning reduces the degree of genetically‐based local adaptation following the expansion and facilitates maintenance of genetic variation within local populations. Thus, in heterogeneous environments learning may facilitate evolutionary range expansions and maintenance of the potential of local populations to respond to subsequent environmental changes.     

Expanded thermal niche for a diving vertebrate: A leatherback turtle diving into near-freezing water

The global distribution of extant reptiles is more limited than that of mammals or birds, with low reptilian species diversity at high latitudes. Central to this limited geographical distribution is the ectothermic nature of reptiles, which means that they generally become torpid at cold temperatures. However, here we report the first detailed telemetry from a leatherback turtle (Dermochelys coriacea) diving in cold water at high latitude. An individual equipped with a satellite tag that relayed temperature-depth profiles dived continuously for many weeks into sub-surface waters as cold as 0.4 °C. Global warming will likely increase the foraging range of leatherback turtles further into temperate and boreal waters.     

Environment versus dispersal in the assembly of western Amazonian palm communities

Aim It is a central issue in ecology and biogeography to understand what governs community assembly and the maintenance of biodiversity in tropical rain forest ecosystems. A key question is the relative importance of environmental species sorting (niche assembly) and dispersal limitation (dispersal assembly), which we investigate using a large dataset from diverse palm communities. Location Lowland rain forest, western Amazon River Basin, Peru. Methods We inventoried palm communities, registering all palm individuals and recording environmental conditions in 149 transects of 5 m × 500 m. We used ordination, Mantel tests and indicator species analysis (ISA) to assess compositional patterns, species responses to geographical location and environmental factors. Mantel tests were used to assess the relative importance of geographical distance (as a proxy for dispersal limitation) and environmental differences as possible drivers of dissimilarity in palm species composition. We repeated the Mantel tests for subsets of species that differ in traits of likely importance for habitat specialization and dispersal (height and range size). Results We found a strong relationship between compositional dissimilarity and environmental distance and a weaker but also significant relationship between compositional dissimilarity and geographical distance. Consistent with expectations, relationships with environmental and geographical distance were stronger for understorey species than for canopy species. Geographical distance had a higher correlation with compositional dissimilarity for small‐ranged species compared with large‐ranged species, whereas the opposite was true for environmental distance. The main environmental correlates were inundation and soil nutrient levels. Main conclusions The assembly of palm communities in the western Amazon appears to be driven primarily by species sorting according to hydrology and soil, but with dispersal limitation also playing an important role. The importance of environmental characteristics and geographical distance varies depending on plant height and geographical range size in agreement with functional predictions, increasing our confidence in the inferred assembly mechanisms.     

Detection of coccidioidal antibodies in serum of a small rodent community in Baja California,Mexico

Coccidioidomycosis (Valley Fever) represents a serious threat to inhabitants of endemic areas of North America. Despite successful clinical isolations of the fungal etiological agent, Coccidioides spp., the screening of environmental samples has had low effectiveness, mainly because of the poor characterization of Coccidioides ecological niche. We explored Valle de las Palmas, Baja California, Mexico, a highly endemic area near the U.S.–Mexico border, where we previously detected Coccidioides via culture-independent molecular methods. By testing the serum from 40-trapped rodents with ELISA, we detected antibodies against Coccidioides in two species: Peromyscus maniculatus and Neotoma lepida. This study comprises the first report of wild rodent serum tested for coccidioidal antibodies, and sets the basis to analyze this pathogen in its natural environment and explore its potential ecological niche.