Genetic analysis of four populations resulted in the mean number of alleles per locus ranging from 10.25 to 14.58 and mean expected heterozygosity from 0.78 to 0.88. Cross-amplification of all 12 loci was attempted in six additional yucca species.\n\nConclusions: These loci should

prove useful for population genetic research in Yucca brevifolia, and cross-amplification of these loci in related species suggests that they may be useful in studies of hybridization and introgression between species.”
“Studies of food webs suggest that limited nonrandom dispersal Histone Methyltransf inhibitor can play an important role in structuring food webs. It is not clear, however, whether density-dependent dispersal fits empirical patterns of food webs better than density-independent dispersal. Here, we study a spatially distributed food web, using a series of population-dispersal models that contrast density-independent and density-dependent dispersal in landscapes where sampled sites are either homogeneously or heterogeneously distributed. These models are fitted to empirical

data, allowing us to infer mechanisms that are consistent with the data. Our results show that models with density-dependent dispersal fit the , , and tritrophic richness observed in empirical data best. Our results also show that density-dependent dispersal leads to a critical distance threshold beyond Quisinostat in vivo which site similarity (i.e., tritrophic richness) starts to decrease much faster. Such a threshold can also be detected in the empirical data. In contrast, models with density-independent dispersal do not predict such a threshold. Moreover, preferential dispersal from more centrally located sites to peripheral sites does not provide a better fit to empirical data when compared with

symmetric dispersal between sites. AG-881 Our results suggest that nonrandom dispersal in heterogeneous landscapes is an important driver that shapes local and regional richness (i.e., and tritrophic richness, respectively) as well as the distance-decay relationship (i.e., tritrophic richness) in food webs.”
“Increases in mortality of trembling aspen (Populus tremuloides Michx.) have been recorded across large areas of western North America following recent periods of exceptionally severe drought. The resultant increase in standing, dead tree biomass represents a significant potential source of carbon emissions to the atmosphere, but the timing of emissions is partially driven by dead-wood dynamics which include the fall down and breakage of dead aspen stems. The rate at which dead trees fall to the ground also strongly influences the period over which forest dieback episodes can be detected by aerial surveys or satellite remote sensing observations.