Island Syndrome Research
From 2013 to 2016, we studied several populations of rodents living on island or mainland sites, along the Winnipeg River system (Minaki, northwestern Ontario). Our objective was to test the island syndrome hypothesis, which states that individuals living on islands share several characters that differentiate them from their mainland conspecifics. In particular, they are expected to be larger, more docile, less active, and more thorough in their exploration. The island syndrome hypothesis was constructed with very isolated oceanic islands in mind, but we wanted to know if the effects of insularity could also be detected on islands where the movements of individuals are limited but still possible, like those in river and lake systems. We also wanted to see how behaviour affected the metapopulation structure of these rodents by influencing the probabilities of dispersal. Finally, we wanted to see whether spatial variation in rodent gut microbiota reflected the genetic structure of the rodent metapopulation.
Although we found differences between insular and continental populations that are consistent with the island syndrome hypothesis, our results do not strongly support its application to these populations. Island deer mice are far less aggressive, more thorough explorers, and island males were larger than mice living on the mainland. Red-backed voles, however, showed very little phenotypic differentiation. Using genomic tools, we found a genetic structure in the deer mouse metapopulation that was linked to connectivity between populations. Mass, tail length, exploration, and docility showed moderate to strong heritability. Thanks to these tools, we could also identify immigrants or their close descendants and link their status to some of their phenotypes for the traits studied.
Finally, we found that the structure of the intestinal bacterial meta-metacommunity depends on the connectivity between host populations, and that intestinal microbiota influences the behaviour and life history traits of rodents.
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According to our results, island and continental populations show different evolutionary trajectories with their ecological particularities. They have implications for the study of the effects of natural and anthropogenic habitat fragmentation.
Collaborators : Dany Garant, Louis Bernatchez, Steven Kembel
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Students : Joël Jameson (PhD), Tristan Juette (PhD), Josh Miller (PDF)
Metapopulations
With its many lakes and islands the Winnipeg River system offers an ideal location to address questions on population differentiation in a naturally fragmented habitat.
Insularity syndrome
Our results indicate that island mice are less aggressive and more thorough in their exploration, and males are larger, than those from mainland populations. These results only partially support the predictions associated with the insularity syndrome hypothesis. We propose a model more adapted to island populations where the islands are not very isolated from the mainland.
Genomics
We have also shown that these phenotypic differences are associated with a marked genomic differentiation between the two types of populations. We also show particularities of microbiota associated with the different ecological conditions.