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Murphy J.C.,Field Museum of Natural History
Integrative and Comparative Biology | Year: 2012

Few species of snakes show extensive adaptations to aquatic environments and even fewer exploit the oceans. A survey of morphology, lifestyles, and habitats of 2552 alethenophidian snakes revealed 362 (14%) that use aquatic environments, are semi-aquatic, or aquatic; about 70 (2.7%) of these are sea snakes (Hydrophiinae and Laticaudinae). The ancient and aquatic family Acrochordidae contains three extant species, all of which have populations inhabiting brackish or marine environments, as well as freshwater. The Homalopsidae have the most ecologically diverse representatives in coastal habitats. Other families containing species exploiting saline waters with populations in freshwater environments include: the Dipsadidae of the western hemisphere, the cosmopolitan Natricidae, the African Grayinae, and probably a few Colubridae. Species with aquatic and semi-aquatic lifestyles are compared with more terrestrial (fossorial, cryptozoic, and arboreal) species for morphological traits and life histories that are convergent with those found in sea snakes; this may provide clues to the evolution of marine snakes and increase our understanding of snake diversity. © 2012 The Author. Source

Patterson B.D.,Field Museum of Natural History
Molecular Ecology | Year: 2010

To use the 'lessons of the Pleistocene' to forecast the biotic effects of climate change, we must parse the effects of history and ecology in the Quaternary record. The preponderance of Northern Hemisphere studies of biotic responses to climate change provides a limited set of players and environmental circumstances with which to decouple these drivers. In this issue Lessa et al. (2010) examine population structure in 14 species of mice distributed across Patagonia and Tierra del Fuego in southern South America. In the Southern Cone, glacial ice was alpine, not polar; major habitats were (and are) oriented N-S, not E-W; and habitable land area actually increased, not decreased, at the height of the last glacial maximum (LGM). Despite these differences, there is evidence for poleward demographic expansion in 10 of the 14 species, and phylogeographic breaks in these are likewise stepped by latitude (and presumably history) rather than by biome. Nevertheless, high latitude endemism and the antiquity of these lineages point to an extended presence in the region that very likely predates the Pleistocene. © 2010 Blackwell Publishing Ltd. Source

Terrell J.E.,Field Museum of Natural History
Annals of Human Genetics | Year: 2010

Social network analysis (SNA) is a body of theory and a set of relatively new computer-aided techniques used in the analysis and study of relational data. Recent studies of autosomal markers from over 40 human populations in the south-western Pacific have further documented the remarkable degree of genetic diversity in this part of the world. I report additional analysis using SNA methods contributing new controlled observations on the structuring of genetic diversity among these islanders. These SNA mappings are then compared with model-based network expectations derived from the geographic distances among the same populations. Previous studies found that genetic divergence among island Melanesian populations is organised by island, island size/topography, and position (coastal vs. inland), and that similarities observed correlate only weakly with an isolation-by-distance model. Using SNA methods, however, improves the resolution of among population comparison, and suggests that isolation by distance constrained by social networks together with position (coastal/inland) accounts for much of the population structuring observed. The multilocus data now available is also in accord with current thinking on the impact of major biogeographical transformations on prehistoric colonisation and post-settlement human interaction in Oceania. © 2010 The Author Journal compilation © 2010 Blackwell Publishing Ltd/University College London. Source

Roopnarine P.D.,California Academy of Sciences | Angielczyk K.D.,Field Museum of Natural History
Biology Letters | Year: 2012

The fossil record presents palaeoecological patterns of rise and fall on multiple scales of time and biological organization. Here, we argue that the rise and fall of species can result from a tragedy of the commons, wherein the pursuit of self-interests by individual agents in a larger interactive system is detrimental to the overall performance or condition of the system. Species evolving within particular communities may conform to this situation, affecting the ecological robustness of their communities. Results from a trophic network model of Permian-Triassic terrestrial communities suggest that community performance on geological timescales may in turn constrain the evolutionary opportunities and histories of the species within them. © 2011 The Royal Society. Source

Lucking R.,Field Museum of Natural History
Biodiversity and Conservation | Year: 2012

A numerical approach is presented to predict the number of potentially undiscovered species in groups of species that exhibit a 'modular' combination of character states, that is, nearly 'free' combination that is not random but allows for a wide range of cross-combination of character states. The method uses a character correlation index (CCI) based on observed versus expected frequencies of pairwise character state combinations in known species of a group to estimate the degree of potentially positive and negative evolutionary constraints in the co-occurrence of character states. For instance, if a character state combination, such as 'muriform ascospores' and 'presence of norstictic acid', occurs less frequently than expected by chance, it indicates the presence of a negative evolutionary constraint. If no such constraint is detected, but a particular character combination has not yet been observed in a described species, it can be predicted that yet undescribed species will exhibit that combination. The method can therefore be used to detect 'gaps' in the taxonomic record, i. e. character combinations that have not been detected in known species but are likely to occur in undiscovered species. Modular combination of character states appears to be particularly common in Fungi, including lichens, and the method was here used to predict species richness in the lichen genus Graphis, specifically the Graphisscripta group. A total of 42 species is known in this group and, out of a total of 240 possible character state combinations, a further 48 were found likely to represent undiscovered species, suggesting that the real species number in this group is close to 90 or about twice the number now known. This agrees well with previous estimates for undiscovered diversity of tropical lichen species and for the first time gives a taxonomic prediction of how such 'missing' species are expected to look like. © 2012 Springer Science+Business Media B.V. Source

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