Understanding How Life-history Traits and Environmental Gradients Structure Diversity

Determining how diversity is distributed through space and time is a fundamental goal of ecology. My research tested how speciesâ life-history traits structure diversity at landscape and broader scales and over time. I first asked how traits related to seed dispersal shape plant diversity in a naturally fragmented landscape by testing the relationship between diversity and patch characteristics (size and isolation) for species with different dispersal modes. Dispersal mode altered outcomes predicted from theory â while fragment isolation had a negative effect on wind-dispersed species, it did not influence the diversity of animal-dispersed species. I then examined how zooplankton traits (body size and dormancy) correlate with species distributions at a large scale using lakes across an 1800 km north-south gradient in western Canada. Despite predictions that body size should decrease with latitude and low temperatures, I found only weak evidence for any effect of latitude on inter- and intra- specific body size. Zooplankton dormancy dynamics are virtually impossible to test through sampling, yet dormancy underpins seasonal fluctuations in abundance and long term persistence, and it is expected to vary with climate. I therefore used an experimental approach to test how temperature and photoperiod affect hatching rates of dormant eggs from lakes across the latitudinal gradient. My results suggest that mismatches between temperature and photoperiod, as predicted to result from climate change, could drive latitude-dependent shifts in zooplankton emergence. Finally, I examined the temporal stability of diversity across the same latitudinal gradient by examining species colonization and extinction over 50 years. I found that low-latitude communities are increasingly diverse and comprised of small-bodied species despite more rapid temperature change at higher latitudes. Overall, my research has implications for how global changes, such as fragmentation and climate change, alter diversity by changing the viability of specific life-history strategies.Ph.D