Current Research Projects

The Evolution of Selfing     

           

Current models predict that selfing should be advantageous for plants experiencing unreliable pollination (selfing increases reproductive assurance and decreases pollen and seed discounting) and low inbreeding depression. To test these models, we are comparing functional aspects of the mating system among populations of Collinsia parviflora (Blue-eyed Mary) from Vancouver Island that differ in flower size.  We’ve found that autonomous selfing ability decreases as flower size increases; that pollinator visit rates increase with flower size;  that selfing provides greater reproductive assurance in small-flowered populations and less in large-flowered populations; and that although inbreeding depression is low overall it tends to be higher in large-flowered populations.  

Why is Collinsia flower size so variable in BC?  All BC populations of Collinsia are tetraploid, as are some populations of different flower sizes in the US;  diploid populations in the US are either large- or small-flowered (never intermediate) and ploidy provides barriers to interbreeding.  We hypothesize that among-population variation in flower size is due to divergent selection, both by pollinators (as noted above) and by abiotic factors.  Rainfall is significantly lower in locations where Collinsia populations are small-flowered, and these populations reach reproductive maturity earlier, perhaps because time to complete the life cycle is limited in ephemeral environments.  Ongoing experiments aim to evaluate local adaptation due to flower size variation, and contemporary selection due to pollinators (which should select for larger flowers when present) and rainfall (which should select for faster reproduction when in short supply).  

Determinants and Impacts of Pollinator Diversity

Classic island biogeography theory predicts that biodiversity and abundance should increase with island size;  we make similar predictions for fragmented ecosystems.  We’ve shown that pollinator biodiversity tends to be higher in larger fragments of the Garry Oak Ecosystem, but this is largely due to the response of some (but not all) nesting guilds of bees.  Pollen limitation of at least some wildflowers is lower in fragments that support greater diversity.  Currently, we are investigating how pollen limitation of multiple wildflower species varies among years and fragments that differ in bee diversity, and we are building plant-pollinator interaction webs to investigate how connectance varies with plant and bee diversity.  

Human impacts go beyond fragmentation of habitat to other modifications.  Agroecosystems replace natural habitats and yet may rely on ecosystem services (such as pollination) that accrue from natural habitats, suggesting that agriculture and conservation could be linked.  In 2010 the lab is initiating research in the South Okanagan, investigating the wild-agroecosystem interface in a landscape context (and the contribution of native pollinators to food production).  We are also asking how rangeland practices affect pollinator diversity and abundance, expecting both positive (nest site creation) and negative (removal of forbs) impacts.  In future we plan to investigate the effects of different farming practices (ie organic vs conventional;  mixed use vs monoculture) on pollinator biodiversity and crop yields.  

Multi-trophic Interactions

                                 

Interactions between members of a community can be important determinants of fitness, and when one of the players is a plant we need to transcend the “trophic” part of those interactions and include mutualisms in our conceptual framework.  JC Cahill of the U. of Alberta and I showed that disrupting plant-mychorrhizal interactions affected the composition of floral visitors, due to shifts in the floral display of the interactors.  Former postdoc Alida Janmaat (currently at UFV) and I are investigating whether spittlebugs, which reduce flower size in large- but not small-flowered Collinsia, affect pollinator visit rates.  And at some point the lab needs to follow up on the observation that small-flowered populations of Collinsia produce more extra-floral nectar than mid- or large-flowered populations (is it due to differences in ant or herbivore communities?  Simple re-allocation of resources?), and ant protection, and plant fitness, is correlated with extra-floral nectar production.