Inferring evolutionary scenarios with geostatistics and geographical information systems for the viperid snakes Vipera latastei and Vipera monticola

The present study aimed to infer evolutionary scenarios for Vipera latastei and Vipera monticola in the Iberian Peninsula and the Maghreb through the identification of spatial patterns in morphological character variation and biogeographic patterns in morphological variability distribution. Ten morphological traits from 630 vipers were analysed with geostatistic and ecological niche modelling in a geographical information system. Interpolation by Kriging was used to generate surfaces of morphological variation, which were combined with spatial principal components analysis (SPCA). Putative morphological differentiated groups generated by SPCA maps were tested with discriminant function analysis (DFA). Maximum entropy modelling and nine environmental variables were used to identify factors limiting the distribution of groups and areas for their potential occurrence. Groups supported by DFA were: Western Iberia, Eastern Iberia, Rif plus Middle Atlas, Algeria, and High Atlas. Their distribution is influenced by common environmental factors such as precipitation. Areas of probable sympatry between Iberian groups matched the morphological clines observed by geostatistics tools. Geographic variation patterns in V. latastei‐monticola are probably due to vicariant separation of Iberian and African populations during the opening of the Strait of Gibraltar, and population refugia during the Quaternary glaciations with secondary contact. The taxonomic status of northern Morocco and Algerian groups should be further investigated. We conclude that geostatistics and niche‐modelling tools are adequate to infer morphological variability across wide geographic ranges of species. © 2008 The Linnean Society of London, Biological Journal of the Linnean Society, 2008, 95 , 790–806.     

The response of life‐history traits to a new species in the community: a story of Drosophila parasitoids from the Rhône and Saône valleys

In the present study, we investigated the evolution of life‐history traits in the main species of a community, after the arrival of a new competitor. Two parasitoid species, Leptopilina heterotoma and Asobara tabida, are present throughout the Rhône and Saône valleys, whereas a third species, Leptopilina boulardi, is slowly extending its distribution northwards. In the presence of L. boulardi, competing parasitoids experience a higher mortality and lower host availability. Resources should thus be re‐allocated between traits according to these new factors. We compared life‐history traits of populations of L. heterotoma and A. tabida in areas with and without L. boulardi. As predicted by both Price's balanced mortality hypothesis and the theory of life‐history traits, we found that investment in reproduction is higher in southern populations for both native species, coupled with higher travelling abilities. However, only A. tabida paid their higher fecundity by a lower longevity. The absence of a clear trade‐off between these traits in L. heterotoma may be explained by a lower metabolic rate in southern populations. These results highlight the importance of the community change over climate in the evolution of life‐history traits in this parasitoid community. © 2012 The Linnean Society of London, Biological Journal of the Linnean Society, 2012, ?? , ??–??.     

Pelmatozoan arms from the Middle Cambrian of Australia: bridging the gap between brachioles and brachials?

The early Middle Cambrian Monastery Creek Phosphorite (Beetle Creek Formation, Queensland, Australia) contains an assemblage of disarticulated echinoderm ossicles that are exquisitely preserved. Amongst this material we recognize pelmatozoan brachials, radials, basals and holomeric columnals. Although we cannot reconstruct the complete animal with precision, these elements represent the oldest known pelmatozoan with crinoid-like appendages. Key elements include isotomously to heterotomously branched uniserial appendage plates with a tripartite adoral food groove, a longitudinal central canal interpreted as housing entoneural nerve, and differentiated articulation facets. There are also epispire-bearing radials bearing one to four arm insertion-facets, each one pierced by a central neural canal. These canals run internal towards the oral area beneath the external food groove. Co-occuring material includes single truncated cone-shaped basals and holomeric columnals, both with a similar articulation pattern, and irregular, epispire-bearing thecal plates. This mosaic of crinozoan (uniserial isotomous to heterotomous arms with neural canal), blastozoan (epispire-bearing thecal plates, appendage leading to oral thecal food groove without direct connection with body cavity) and apomorphic characters (circumoral instead of basal entoneural plexus) is unexpected and demonstrates that crinoid-like pelmatozoans with uniserial, branched arms appeared significantly earlier than the Tremadocian, when the first articulated crinoid skeletons are found. It also raises questions about the polyphyletic appearance of feeding appendages among pelmatozoan echinoderms.     

Which proximate factor determines sexual size dimorphism in tiger snakes?

Diverse interactions between factors that influence body size complicate the identification of the primary determinants of sexual size dimorphism. Using data from a long‐term field study (1997–2009), we examined the contributions of the main proximate factors potentially influencing sexual size dimorphism from birth to adulthood in tiger snakes (Notechis scutatus). Data on body size, body mass and body condition of neonates, juveniles and adults were obtained by mark–recapture. Frequent recaptures allowed us to monitor reproductive status, diet and food intake, and to estimate survival and growth rates in age and sex classes. Additional data from females held briefly in captivity enabled us to assess reproductive output and the body mass lost at parturition (proxies for reproductive effort). From birth to maturity, individuals of both sexes experienced similar growth and mortality rates. We found no difference in diet, feeding and survival rates between the sexes, nor between juveniles and adults. On maturity, despite comparable diet and food intake by both sexes, the high energy requirements of vitellogenesis and gestation were responsible for a depletion of body reserves and probably resulted in a marked decrease in growth rates. Males were largely exempt from such costs of reproduction, and so could grow faster than females and attain larger body sizes. The absence of niche divergence between the sexes (uniformity of habitat, lack of predators) suggests that the impact of differential energetic investment for reproduction on growth rate is probably the main proximate factor influencing sexual size dimorphism in this species. © 2011 The Linnean Society of London, Biological Journal of the Linnean Society, 2011, 103 , 668–680.     

Combined measurements of egg fatty acids and stable isotopes as indicators of feeding ecology in lake-dwelling birds

1. We examined whether egg fatty acid (FA) profiles and stable isotopes (SIA) could be used in a comparative way to infer the diet of two aquatic bird species with contrasting feeding habits: a surface forager, the pheasant-tailed jacana ( Hydrophasianus chirurgus ), and a pursuit-diving forager, the little cormorant ( Phalacrocorax niger ), at Haleji Lake (Pakistan).
2. The species differed markedly in the overall percentage of saturated and polyunsaturated fatty acids. Moreover, among jacanas, two groups of birds had relatively high or low concentrations of long-chain essential PUFAs (such as 18:2 n-6 and 20:4 n-6), suggesting differing contributions from animal prey and plant material.
3. These trophic differences were corroborated by δ¹⁵N values which indicated both a higher trophic position in cormorants relative to jacanas, and differences in trophic position for the two groups of jacanas. In this latter species δ¹³C values in both groups also pointed to differing diets, involving mainly grazing plants or a contribution from animal resources (aquatic invertebrates or insects).
4. Both lower values of δ¹³C and higher percentages of 18:1 n-7 detected in little cormorants may indicate the influence of the anoxic water, typical of a freshwater system densely covered by macrophytes.
5. These results indicate how both biomarkers offer complementary information in studies of feeding ecology, refining interpretations of trophic pathways which are usually based on FA or SIA alone. Comparisons of FA profiles and SIA among species also proved to be a reliable approach for inferring the diet of species for which information is scarce or contradictory, as is the case for the pheasant-tailed jacana.