Aim Body size variation in animal assemblages is a widely addressed pattern in biogeographical studies, and is affected by both environmental gradients and phylogenetic constraints. However, no study has yet explored to what extent the association between body size variation and environmental gradients across broad spatial scales is influenced by the biogeographical distribution of different phylogenetic lineages. In this study, we discriminate the influences of environmental variables and phylogenetic community composition on body size variation in South American sigmodontine rodents.Location South America.Methods We computed the mean body mass of sigmodontine species cooccurring in 1 9 1°cells across South America. For each cell we recorded mean values for three environmental variables. We characterized the phylogenetic composition of sigmodontine assemblages within each cell using phylogenetic fuzzy-weighting and principal coordinates of phylogenetic structure (PCPS). We then partitioned out the influence of environmental factors and the phylogenetic community composition on mean body size.Results Mean body size variation was mostly explained by shared influence of phylogenetic community composition (PCPS) and environmental factors (68%), while exclusive influence of PCPS was low (19%), and of environment was even lower (0.47%). Increases in body size were related to increases in annual mean temperature, and the influence of environment on body size was mediated by the distribution of sigmodontine lineages across South America.Main conclusions Environment alone was not sufficient to explain body size variation in sigmodontine assemblages. Rather, environmental gradients interacted with historical processes to determine body size variation in the Neotropical assemblages. These results have implications for the way we think of body size gradients across species assemblages, because any gradient in a trait may be a result of differences in the biogeographical distribution of lineages across space, which should be considered in an explicit context.

Fine-scale habitat selection of Chilean dolphins was studied between January and April 2002 through shore-based theodolite tracking in order to investigate the environmental and behavioural determinants of habitat use, and to evaluate the interactions between this species and aquaculture activities in Yaldad Bay, southern Chile. During 293.5 h of effort, movement and habitat selection patterns of dolphins exhibited a significantly concentrated use of only 21% of the entire study area. Correspondence analysis showed that shallow waters (5–10 m), proximity to coast and rivers were the most significant environmental parameters determining fine-scale dolphin distribution patterns, with foraging the most frequently observed activity. Aquaculture activities in the area were observed to affect dolphin habitat use patterns by restricting space available for biologically important dolphin behaviours.

The Southern lapwing (Vanellus chilensis) is endemic to America and is well-known because of the vast expansion of its geographical distribution and its involvement in air accidents. Despite its popularity, there is no information concerning the genomic organization and karyotype of this species. Hence, because other species of the genus Vanellus have variable diploid numbers from 2n = 58 to 76, the aim of this report was to analyze the karyotype of V. chilensis by means of classical and molecular cytogenetics. We found that 2n = 78 and chromosome painting using probes of Gallus gallus (GGA) and Leucopternis albicollis revealed an organization similar to the avian putative ancestral karyotype, except for the fusion of GGA7 and GGA8, also found in Burhinus oedicnemus, the only Charadriiforme species analyzed by FISH so far. This rearrangement may represent a cytogenetic signature for this group and, in addition, must be responsible for the difference between the diploid number found in the avian putative ancestral karyotype (2n = 80) and V. chilensis (2n = 78).

The melanocortin 1 receptor (MC1R) is involved in the control of melanogenesis. Polymorphisms in this gene have been associated with variation in skin and hair color and with elevated risk for the development of melanoma. Here we used 11 computational tools based on different approaches to predict the damage-associated non-synonymous single nucleotide polymorphisms (nsSNPs) in the coding region of the human MC1R gene. Among the 92 nsSNPs arranged according to the predictions 62% were classified as damaging in more than five tools. The classification was significantly correlated with the scores of two consensus programs. Alleles associated with the red hair color (RHC) phenotype and with the risk of melanoma were examined. The R variants D84E, R142H, R151C, I155T, R160W and D294H were classified as damaging by the majority of the tools while the r variants V60L, V92M and R163Q have been predicted as neutral in most of the programs The combination of the prediction tools results in 14 nsSNPs indicated as the most damaging mutations in MC1R (L48P, R67W, H70Y, P72L, S83P, R151H, S172I, L206P, T242I, G255R, P256S, C273Y, C289R and R306H); C273Y showed to be highly damaging in SIFT, Polyphen-2, MutPred, PANTHER and PROVEAN scores. The computational analysis proved capable of identifying the potentially damaging nsSNPs in MC1R, which are candidates for further laboratory studies of the functional and pharmacological significance of the alterations in the receptor and the phenotypic outcomes.

Aim We describe patterns of skull size and shape variation in an Atlantic forest endemic rodent to test the influence of genetic structure, historical and environmental variables upon intraspecific morphological variability. Location South America, Brazil, Atlantic forest. Methods We analyse subtle differences in skull morphology of Akodon cursor through geometric morphometrics applied to 324 individuals from 12 localities distributed throughout the species range. Using cytochrome‐b gene (cyt‐b) sequences from 125 individuals (38 localities), we describe underlying patterns of genetic structure and transform them into distance measures that are included in our morphological analyses. We estimate the relative importance of genetic structure, historical variables and environmental variables on skull size and shape through mixed model selection and Akaike's information criterion. Results Geographical patterns in skull size are mainly explained by non‐random factors related to primary productivity and precipitation, whereas spatial shifts in shape correlate with mitochondrial divergence. Cytochrome‐b data revealed a phylogeographic break around the Jequitinhonha River, yet striking morphological shifts were observed further south. Differences in palaeostability between regions, and the configuration of rivers, appear as secondary sources of explanation for observed patterns. Main conclusions Multiple forces explain morphological variation within A. cursor. Teasing apart the effects of local adaptation and gene flow may be difficult, but is a key to improve our understanding of the drivers of intraspecific morphological variation. Our findings support the view that size is a more labile feature than shape, and that it may more easily break away from constraints imposed by gene flow. The combination of random and non‐random factors, together with documented breaks in the distribution of the Atlantic forest over the Late Quaternary, accounts for the majority of morphological differences observed in A. cursor.

No abstract

Subterranean rodents of the genus Ctenomys usually present an allopatric or parapatric distribution. Currently, two cases of sympatry have been recognized for the genus in the coastal dunes of southern Argentina and southern Brazil. In this context, they are ideal models to test hypotheses about the factors that delimit the patterns of space use and to understand interspecific interactions in small mammals. We investigated the vegetation structure, plant biomass and soil hardness selected by two species of subterranean rodents (Ctenomys flamarioni and C. minutus) when distributed in sympatry and allopatry from nine different areas along the line of coastal dunes in southern Brazil. In addition, our work presents a new record of a third area of sympatry for the genus Ctenomys. Ctenomys flamarioni and C. minutus show habitat segregation in the area where they occur in sympatry. These species show segregation in their selection of microhabitats, differing in relation to soil hardness, plant biomass, and plant cover. Ctenomys flamarioni showed a distinction in habitat selection when occurring in allopatry and sympatry, whereas C. minutus selected the same habitat characteristics under both conditions. A possible explanation to the observed pattern is that these species have acquired different adaptations over time which allows them the ability to exploit different resources and thus avoid competitive interactions all together.

We investigated the demographic parameters and the relationships between population density and extrinsic factors (temperature, rainfall, humidity and insolation) of two sigmodontine rodents (