Publication Date: 2016.
Demographic and genetic connectivity of fragmented plant populations will depend on effective propagule flow across the landscape. We analyze functional connectivity in a holm oak (Quercus ilex) fragmented landscape by considering three important stages driving recruitment: effective pollination, acorn production and acorn dispersal. We used a network approach to (1) determine if pollen-mediated gene exchange across the landscape was spatially structured; (2) estimate the effects of limited acorn dispersal on functional connectivity; (3) identify which landscape traits could drive source-sink dynamics of gene flow. Although long distance dispersal was relatively frequent, most effective pollen flow occurred over short distances (<100 m). This resulted in a significantly modular structure of the mating network, yielding higher gene flow among nearby fragments. Limited mouse acorn hoarding activity had a strong impact on landscape connectivity, decreasing male gametic immigration rates into forest patches by one order of magnitude Besides, our results show that big forest fragments (>10 ha) are the main pollen sources, while small ones (<1 ha) are important pollen sinks. Thus, big fragments are critical to maintain functional connectivity, while small forest fragments may provide acorn crops better representing regional genetic diversity. In addition to area effects, less isolated and more central fragments showed higher migration rates and exchanged effective pollen with more fragments. Hence, we expected that landscapes with uniform or clumped distribution of big forest fragments would show optimal connectivity traits. However, despite that simulated gene flow was more evenly distributed across the landscape, connectance and migration rates decreased. Our results call for caution before translating patch-level management guidelines to the landscape scale. They also show that the level of functional connectivity may change throughout the recruitment process, suggesting that large-scale conservation strategies may fail if local effective seed establishment is disregarded.
Author affiliation: Morán López, Teresa. Consejo Superior de Investigaciones Cientificas. Museo Nacional de Ciencias Naturales; España
Author affiliation: Robledo Arnuncio, Juan José. Centro de Investigación Forestal; España
Author affiliation: Díaz, Mario. Consejo Superior de Investigaciones Cientificas. Museo Nacional de Ciencias Naturales; España
Author affiliation: Morales, Juan Manuel. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Patagonia Norte. Instituto de Investigaciones en Biodiversidad y Medioambiente. Universidad Nacional del Comahue. Centro Regional Universidad Bariloche. Instituto de Investigaciones en Biodiversidad y Medioambiente; Argentina
Author affiliation: Lázaro Nogal, Ana. Centro de Investigación Forestal; España
Author affiliation: Lorenzo, Zaida. Centro de Investigación Forestal; España
Author affiliation: Valladares, Fernando. Consejo Superior de Investigaciones Cientificas. Museo Nacional de Ciencias Naturales; España
Repository: CONICET Digital (CONICET). Consejo Nacional de Investigaciones Científicas y Técnicas