Recent advances in ecological niche modeling (ENM) algorithms, in conjunction with increasing availability of geographic information system (GIS) data, allow species' niches to be predicted over broad geographic areas using environmental characteristics associated with point localities for a given species. Consequently, the examination of how niches evolve is now possible using a regionally inclusive multivariate approach to characterize the environmental requirements of a species. Initial work that uses this approach has suggested that niche evolution is characterized by conservatism: the more closely related species are, the more similar are their niches. We applied a phylogenetic approach to examine niche evolution during the radiation of Cuban trunk-ground anoles (Anolis sagrei group), which has produced 15 species in Cuba. We modeled the niche of 11 species within this group using the WhyWhere ENM algorithm and examined the evolution of the niche using a phylogeny based on ;1500 base pairs of mitochondrial DNA. No general relationship exists between phylogenetic similarity and niche similarity. Examination of species pairs indicates some examples in which closely related species display niche conservatism and some in which they exhibit highly divergent niches. In addition, some distantly related species exhibit significant niche similarity. Comparisons also revealed a specialist-generalist sister species pair in which the niche of one species is nested within, and much narrower than, the niche of another closely related species.

Change in body size within an evolutionary lineage over time has been under investigation since the synthesis of Cope's rule, which suggested that there is a tendency for mammals to evolve larger body size. Data from the fossil record have subsequently been examined for several other taxonomic groups to determine whether they also displayed an evolutionary increase in body size. However, we are not aware of any species-level study that has investigated the evolution of body size within an extant continental group. Data acquired from the fossil record and data derived from the evolutionary relationships of extant species are not similar, with each set exhibiting both strengths and weaknesses related to inferring evolutionary patterns. Consequently, expectation that general trends exhibited in the fossil record will correspond to patterns in extant groups is not necessarily warranted. Using phylogenetic relationships of extant species, we show that five of nine families of North American freshwater fishes exhibit an evolutionary trend of decreasing body size. These trends result from the basal position of large species and the more derived position of small species within families. Such trends may be caused by the invasion of small streams and subsequent isolation and speciation. This pattern, potentially influenced by size-biased dispersal rates and the high percentage of small streams in North America, suggests a scenario that could result in the generation of the size-frequency distribution of North American freshwater fishes.

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Characterizing the impacts of climatic change on hydrologic processes is critical for managing freshwater systems. Specifically, there is a need to evaluate how the two major components of streamflow, baseflow and stormflow, have responded to recent trends in climate. We derive baseflow and stormflow for 674 sites throughout the United States from 1980 to 2010 to examine their associations with precipitation, potential evapotranspiration, and maximum/minimum temperature. The northeastern (NE) and southwestern (SW) United States display consistent trends in baseflow and stormflow: increasing during fall and winter in the NE and decreasing during all seasons in the SW. Trends elsewhere and at other times of the year are more variable but still associated with changes in climate. Counter to expectations, baseflow and stormflow trends throughout the United States tend to change concurrently. These trends are primarily associated with precipitation trends, but increases in PET are influential and likely to become important in the future.