Conserving Connectivity: Ecological Determinants of Gene Flow in Plants at the Landscape Scale

With intensifying global pressures of habitat loss and fragmentation, there is an increasing need to manage landscapes in a way that maintains gene flow among previously continuous populations. This requires a detailed understanding of the scale of gene flow in nature and of how aspects of the landscape support or inhibit movement. In plants, gene flow occurs through both pollen and seed, each of which may be carried by multiple vectors. This makes it challenging to characterize, and as a consequence, our understanding of the local and landscape drivers of gene flow are limited in plants compared to animals. My thesis addresses this deficiency by quantifying the contributions of landscape structure, individual plant characteristics, and directed seed dispersal to gene flow of plants in fragmented landscapes. First, I used simulations to test if models of pollen flow could be improved by incorporating individual plant characteristics that affect attractiveness to pollinators. The results showed that inter-individual variation in attractiveness explained significantly more variation than inter-mate distance. Second, I took advantage of a network of calcareous grasslands in Germany to quantify the determinants of pollen and seed-mediated gene flow in a specialist herb, Pulsatilla vulgaris. Using 1,449 individuals from 57 populations, genotyped at seven newly developed markers, I tested the efficacy of an ecological shepherding network to maintain seed-mediated gene flow among P. vulgaris populations. I found that (i) shepherding distance explained genetic differentiation better than geographic distance among populations, (ii) populations that were well connected within the network had significantly higher genetic diversity, and (iii) genetic diversity was significantly positively correlated with fitness-related traits. Paternity analysis on a subset of seven populations revealed high rates of self-pollination. Within-population patterns of pollen flow correlated with floral resources measured at the scale of individuals and patches, whereas among-population pollen flow correlated with floral resources measured at the patch scale and landscape context measured at intermediate and large spatial scales. Together my results highlight the importance of using multi-scale and multi-vector approaches when modeling gene flow in plants, and suggests that typical models based on distance alone may be insufficient to capture the complexity of pollination and seed dispersal.

Department dc:contributor.department

Ecology and Evolutionary Biology

Year dc:date.issued

2016

Author dc:creator

• DiLeo, Michelle F.

Advisor dc:contributor.advisor

• Wagner, Helene H

• connectivity
• conservation genetics
• gene flow
• landscape genetics
• plant

Handle dc:identifier.uri

http://hdl.handle.net/1807/76409

OAI identifier oai:identifier

oai:utoronto.scholaris.ca:1807/76409