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Understanding the origin and maintenance of phenotypic variation, particularly across a continuous spatial distribution, represents a key challenge in evolutionary biology. For this, animal venoms represent ideal study systems: they are complex, variable, yet easily quantifiable molecular phenotypes with a clear function. Rattlesnakes display tremendous variation in their venom composition, mostly through strongly dichotomous venom strategies, which may even coexist within a single species. Here, through dense, widespread population-level sampling of the Mojave rattlesnake, Crotalus scutulatus , we show that genomic structural variation at multiple loci underlies extreme geographical variation in venom composition, which is maintained despite extensive gene flow. Unexpectedly, neither diet composition nor neutral population structure explain venom variation. Instead, venom divergence is strongly correlated with environmental conditions. Individual toxin genes correlate with distinct environmental factors, suggesting that different selective pressures can act on individual loci independently of their co-expression patterns or genomic proximity. Our results challenge common assumptions about diet composition as the key selective driver of snake venom evolution and emphasize how the interplay between genomic architecture and local-scale spatial heterogeneity in selective pressures may facilitate the retention of adaptive functional polymorphisms across a continuous space.

Long-term studies of individual animals in nature contribute disproportionately to our understanding of the principles of ecology and evolution. Such field studies can benefit greatly from integrating the methods of molecular genetics with traditional approaches. Even though molecular genetic tools are particularly valuable for species that are difficult to observe directly, they have not been widely adopted. Here, we used molecular genetic techniques in a 10-year radio-telemetric investigation of the western diamond-backed rattlesnake (Crotalus atrox) for an analysis of its mating system and to measure sexual selection. Specifically, we used microsatellite markers to genotype 299 individuals, including neonates from litters of focal females to ascertain parentage using full-pedigree likelihood methods. We detected high levels of multiple paternity within litters, yet found little concordance between paternity and observations of courtship and mating behavior. Larger males did not father significantly more offspring, but we found evidence for size-specific male-mating strategies, with larger males guarding females for longer periods in the mating seasons. Moreover, the spatial proximity of males to mothers was significantly associated with reproductive success. Overall, our field observations alone would have been insufficient to quantitatively measure the mating system of this population of C. atrox, and we thus urge more widespread adoption of molecular tools by field researchers studying the mating systems and sexual selection of snakes and other secretive taxa.

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African biodiversity hotspots: the reptiles of Mt Nlonako, Cameroon. -The reptiles of Mt Nlonako, a mountain at the southeastern edge of the Cameroon mountain range ("Dorsale camerounaise"), were inventoried continually over a six year period from 1998 to 2004. This area encompasses 150 km 2 of lowland, submontane and montane rainforest with an elevation up to 1,825 m. Accounts of 89 species are provided based on collected and photo-documented material. This inventory proved Mt Nlonako to be the most species rich single-locality area in reptilian fauna in Africa. With 63 snake species Mt Nlonako exhibits the greatest number of species in Africa and possibly worldwide. Analysis showed the reptilian species composition to be most similar within Cameroon with that of Korup National Park followed by the Dja Faunal Reserve in the south. Relative to the snake composition the Korup NP and the Dimonika region in Congo-Brazzaville show the highest resemblance. In an African context the reptile fauna of Mt Nlonako is characterized by species which occur in both West and Central Africa as opposed to the mountain's amphibian species which more closely resemble Central African fauna. The high species richness and endemicity is discussed from a paleoclimatic perspective. Conservation status and threats to the reptiles are noted.

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The phylogenetic relationships of the large Palaearctic vipers (Daboia sensu Obst, 1983) and Eristicophis were investigated using immunological comparisons of blood serum albumin and blood serum electrophoresis. The genus Echis was used for outgroup comparisons. Daboia was found to be polyphyletic. The name Daboia should be restricted to the type species russelli which was found to have the same immunological distance to the lebetina group as the monophyletic Pseudocerastes-Eristicophis group. The lebetina group was found to consist of the four species lebetina, schweizeri, mauritanica and deserti. For this group the generic name Macrovipera is revalidated. The taxa schweizeri and deserti are treated as full species. Vipera palaestinae was found to be the closest relative of the V. xanthina group. Nomenclatural history and distribution of the involved taxa is reviewed. Descriptions and diagnoses for the genus Macrovipera and the included species are given.