Pollination, plant reproduction, and population genetics in fragmented habitats: facing theory with evidence

AGUILAR,R., QUESADA, M., ASHWORTH, L., HERRERIAS DIEGO, Y., GALETTO, L., LOBO, J., AIZEN, M.A.

Morelia, Mexico

Simposio; Annual Meeting Association for Tropical Biology and Conservation (ATBC); 2007

Association for Tropical Biology and Conservation

The loss and fragmentation of natural habitats by human activities are pervasive phenomena in terrestrial ecosystems across the Earth and the main drivers of current biodiversity loss. Throughout the last two decades fragmentation studies on plant populations have mainly focused on plant fecundity and plant-pollinator interactions. More recently, population genetic parameters have also been investigated in fragmented and degraded habitats. We quantitatively reviewed the results from fragmentation studies, with the aim of testing (I) whether pollination and reproduction of plant species are differentially susceptible to habitat fragmentation depending on certain reproductive traits that typify the relationship with and the degree of dependence on their pollinators, and (II) whether fragmentation is eroding the genetic composition of fragmented populations. We found an overall large and negative effect of fragmentation on pollination and on plant reproduction. The compatibility system of plants, which reflects the degree of dependence on pollinator mutualism, was the only reproductive trait that explained the differences among the species’ effect sizes. Self-incompatible plants showed strong negative effects of habitat fragmentation on reproduction, whereas self-compatible plants were not significantly affected. Contrary to theoretical expectations, the effect sizes of plants with different degree of pollination specialization did not differ between them. Both, pollination specialist and generalist had large and negative effects of fragmentation. The overall genetic diversity of plants is negatively affected by fragmentation. No significant effects were found on inbreeding parameters in fragmented population. Allelic richness, in particular, decreased more strongly in self-incompatible species as a consequence of fragmentation. Surprisingly, most papers evaluating genetic effects of fragmentation have evaluated adult individuals in relatively new fragmented landscapes. We evaluate these results in the face of theory and propose possible explanations for the observed trends. Finally we discuss the conservation implications of these findings and give suggestions for future research on this area.