Significance: Why biological complexity evolves is a major question in the life sciences, but the specific selection pressures favoring simple or complex traits remain unclear. Using high-resolution measurements of venom complexity in North American pitvipers, we link changes in complexity to natural history via phylogenetic diversity of snake diets. The results indicate that venom complexity evolves in response to phylogenetic diversity in a community of species, likely reflecting divergence in the physiological targets of venom. The nature of a species community, rather than their richness alone, is an important feature in the evolution of complex traits.

We analysed mandible shape of the orders Dasyuromorpha, Didelphimorphia, and Carnivora using two-dimensional geometric morphometrics, in order to exp

Cerradomy's is a monophyletic genus that includes four known species, Cerradomys subflavus, C maracajuensis, C. marinhus, and C. scotti, distributed throughout the open vegetation belt across South America, from northeastern Brazil to southeastern Bolivia, and from eastern to northwestern Paraguay. We revised the status of the species currently assigned to this genus by analyzing skins, skulls, karyotypes, and cytochrome b DNA sequences. We also described two novel species, one distributed in the Brazilian states of Minas Gerais, Bahia, and Sergipe, and the other in the states of Paraiba, Pernambuco, Piaui, Ceara, and Maranhao. Molecular analysis suggested the following phylogenetics arrangement: (((C. subflavus-C. sp.n.2) C. sp.n.1) C scotti)(C. marinhus-C. maracajuensis)). Apparently, both novel species inhabit the Caatinga domain and penetrated the coastal Atlantic rainforest, differing from the remaining congeneric species that are typical open-area inhabitants.American Museum of Natural HistoryField MuseumSmithsonian InstitutionMuseum of Comparative ZoologyConselho Nacional de Pesquisa e Desenvolvimento-CNPq[309978/2003-3]Conselho Nacional de Pesquisa e Desenvolvimento-CNPq[477842/2004-6]Fundacao de Amparo a Pesquisa do Estado de Sao Paulo-FAPESP[98/12273-0]Fundacao de Amparo a Pesquisa do Estado de Sao Paulo-FAPESP[98/05075-7]Fundacao de Amparo a Pesquisa do Estado de Sao Paulo-FAPESP[01/0752-5

The ways in which the taxonomic differences in morphology, behavior or life history relate to each other have been used regularly to test ideas about the selective forces involved in their evolution. Canid species vary significantly in diet, hunting techniques, sociality and cranial morphology. The main goal of this study is to test and explore the possible correlation between bite force and brain volume in canids. For that, we calculated the bite force based on the beam theory, and the brain volume based on three cranial measurements. The species with biggest values of bite force quotient (BFQ) wereSpeothos venaticus(162.25),Cuon alpinus(129.24) andLycaon pictus(124.41) due to several adaptations acquired along with hypercarnivory. Species with the highest values of brain volume quotient (BVQ) wereS. venaticus,Cu. alpinusandL. pictuswith, respectively, 141.35, 139.01 and 131.61, possibly due to the same adaptations that resulted in their biggerBFQ. The highest values of bite force belonged toCanis lupus(830.51 Pa),L. pictus(719.03 Pa) andCa. rufus(530.52 Pa) and the smallest values belong toUrocyon littoralis(98.14 Pa),Vulpes macrotis(92.53 Pa) andV. zerda(72.6 Pa).Ca. lupus,L. pictusandChrysocyon brachyuruspossess the largest brain volumes with respectively 159.29, 146.94 and 120.84 mm³and the smallest values belong toNyctereutes procyonoides(28.2 mm³),V. rueppelli(27.86 mm³) andV. zerda(20.65 mm³). The independent contrasts correlation showed that there is no correlation betweenBVQandBFQ(r = 0.14/P= 0.46), as well as no correlation betweenBFQandBF(r = 0.22/P= 0.26), which indicates the efficiency of the size correction. Bite force and brain volume estimates are much higher in the group hunting hypercarnivores (Lycaon,CuonandSpeothos) and only these showed correlation betweenBFQandBVQ. Our results indicate that cranial adaptations for hypercarnivory also influence braincase size.

Rhamdiopsis krugi is a highly specialized troglobitic (exclusively subterranean) catfish from phreatic water bodies of caves located within two separated metasedimentary basins in the region of Chapada Diamantina, Bahia state, Brazil. In order to test the hypothesis of isolation with differentiation of the groups from the Una-Utinga and Irecê metasedimentary basins, we compared five populations among themselves and with an epigean species of Rhamdiopsis. This was accomplished using geometric morphometrics, a powerful tool for detecting differences in body shape at population and species levels. All studied samples differed significantly from each other, the epigean sample being the most distinct and the Una Basin populations clustering together. Geological and hydrological barriers explain the differences among the subterranean populations. We discuss our results together with the autapomorphies found in R. krugi, which validate its monophyly. These results imply an old age for the R. krugi clade, more than 10 Myr; alternative hypotheses are also presented. We propose a two-step vertical colonization model of the subterranean habitat through the hyporheic zone by an epigean ancestral, with a progressive acquisition of the autapomorphies characterizing R. krugi. For conservation purposes, the two differentiated sets of populations should be considered and referred to as R. krugi ‘Una morphotype’ and R. krugi ‘Irecê morphotype’.