Search

Among numerous concerns, restoration ecologists are routinely plagued with the problem of where to implement conservation efforts to best maintain spatial connectivity and population structure. Knowledge about connectivity within a metapopulation could offer valuable insight to address this issue and could help with the allocation of limited resources more effectively. However, direct estimation of dispersal is challenging because species can disperse widely within a landscape. Here, we developed a novel hierarchical Bayesian model to estimate spatial connectivity from occurrence data of an endangered stream fish, Topeka shiner (Notropis topeka). Our goal was to identify dispersal corridors that are centrally connected to the metapopulation that could be beneficial in decision making about future habitat restorations aimed at maintaining population structure. Connectivity modeling is data intensive and resource managers may not have the necessary data requirements; thus, we also examined the usefulness of graph theory (i.e. network centrality) as a proxy for connectivity. Model selection identified an upstream biased asymmetric dispersal pattern for the species. We were able to quantify and map connectivity and identified over 68 km of stream reaches as highly connected to the metapopulation. Probability of occurrence in dispersal corridors (i.e. streams) increased with connectivity and decreased with drainage area, highlighting the importance of conserving dispersal corridors and preferred habitat patches. Restorations in connected locations would provide critical habitat near important dispersal corridors. Betweenness centrality was positively correlated with connectivity and occurrence in restored habitat. Modeling of metapopulation connectivity and its correlation with graph theory demonstrated the usefulness of these techniques to guide conservation actions, especially in countries where data collection efforts are not common and conservation funding is limited. [Display omitted] • Quantified and mapped metapopulation dispersal corridors • Probability of occurrence increased with connectivity • Graph theory positively correlated to connectivity • Network centrality predicted occurrence in restored habitat [ABSTRACT FROM AUTHOR]

As urban areas continue expanding, major cities become connected forming megacities. Urban encroachment into natural areas transforms the landscape into a built environment with heterogeneously distributed patches of novel habitat. Community structure within novel habitats is influenced by anthropogenic factors including fragmentation and species interactions. Alterations in complex biodiversity patterns may be used to assess how urban stressors impact community assemblages which, ultimately, may inform sustainable management decisions. To manage algal blooms, Aquashade® is applied directly to ponds. We investigated the effects of Aquashade®, nutrient loading and dispersal on local species diversity and compositional turnover of zooplankton communities from suburban ponds in Columbia, MD, USA using a mesocosm approach. We found that Aquashade® acted as an environmental filter by increasing local species diversity and decreasing compositional turnover. This ultimately could have an overall homogenizing effect on the regional species pool (or γ-diversity). The same pattern was observed in mesocosms that received simulated dispersal events of zooplankton. Nutrients, overall, increased autotrophic biomass and while Aquashade® had no effect on autotrophic biomass, the interaction of nutrients and Aquashade® similarly caused a homogenization of the zooplankton community. Additionally, there was an overall increase in cladoceran ephippia in mesocosms receiving Aquashade® compared to those not, suggesting there is a ‘trigger’ switching cladocerans from parthenogenic to sexual reproduction. Taken together, our results show the application of Aquashade®, nutrient loading and dispersal shift biodiversity patterns in urban zooplankton communities. We hypothesize these shifts originate at the resource level through alterations in the phytoplankton community either through composition or nutritive value in ponds receiving Aquashade®. Our study illustrates the importance of investigating multiple-scales of community assemblages when assessing impacts of anthropogenic stressors. Consideration of how to best manage green spaces may include planned un-managed areas to maintain regional biodiversity and heterogenous communities within the urban environment. [ABSTRACT FROM AUTHOR]