Daphnia vertical position and implications for the impact of the invasive Spiny Water Flea, Bythotrephes longimanus, on plankton communities
The introduction of the Spiny Water Flea (Bythotrephes longimanus) in North American lakes has reduced zooplankton abundance and diversity, especially for cladocerans such as Daphnia. Studies have shown that in some invaded lakes Daphnia occupy a deeper vertical in the water column during the day, thereby reducing overlap with Bythotrephes, a visual predator restricted to shallow, light penetrating regions. However, Daphnia daytime vertical position is also influenced by a number of factors including resource availability and UV exposure. The goal of my PhD research was to assess if abiotic factors influence Daphnia vertical position response to Bythotrephes and determine if differences in Daphnia vertical position influence the impact of this predator on plankton communities. My results suggest that Daphnia vertical position in invaded lakes is influenced by water clarity and that Daphnia vertical position mediates Bythotrephes impact on plankton communities.
Besides climate, soils are the major driver of terrestrial plant diversity. In this talk, I will present results from our long-term research program about edaphic drivers of plant taxonomic and functional diversity. Much of our field-based research was conducted along long-term soil chronosequences in south-western Australia. These chronosequences are of particular interest because they occur in a global biodiversity hotspot and provide exceptionally strong natural gradient of soil nutrient availability. Our field studies have allowed us to make important new discoveries about the ecological importance of plant-soil interactions in driving plant biodiversity patterns across soil fertility gradients.
Reproductive and genetic interactions between domesticated and native apple (Malus): a case study of agricultural effects on biological diversity
Agricultural intensification can influence biological diversity multiple ways, from decline of native species via habitat loss and degradation to formation of novel diversity by enhancing reproductive interactions between otherwise isolated congeners. My lab has been studying the potential for such interactions across the Ontario landscape through an analysis of the reproductive biology and population genetics of Maluscoronaria, a native crabapple, and Malus domestica, the introduced and commercially grown apple species. Domestic apple is mostly diploid and obligately outcrossing whereas M. coronaria is tetraploid and has a complex breeding system with asexually and sexually-derived offspring. We assess the potential for reproductive interactions and hybrid fertilization between these species via naturalized populations of domestic apple which have established in open or marginal habitats. The research has led us to better understand the origins of feral apple populations themselves and their role as conduits for the movement of genes across species boundaries.
From Darwin to DNA: evolution, genomics and conservation of the Galapagos giant tortoises
When Charles Darwin arrived on the Galapagos Islands the remarkable morphology of the native breeds of giant tortoise unique to each island struck him as significant. Later on, these thoughts contributed to his ideas about the theory of evolution through natural selection. By the 20th century, some of these species were reduced to the brink of extinction, but today, are a symbol of hope and #ConservationOptimism. In this talk, I will discuss the history of decline and recovery in the Galapagos tortoises, and how conservation programmes informed by phylogenetic and population genetic techniques have contributed to dramatic recoveries of some populations.
The advent of next generation sequencing of entire bacterial communities has allowed for a previously unavailable perspective on animal ecology, wherein we can now view changes in the host’s associated bacterial community as a stressor, or response to stress, that has its own dynamic ecology within that of the host. Arctic char (Salvelinus alpinus) is a traditionally important salmonid species in the Canadian Arctic, with a complex and variable life history strategy. As conditions in the Arctic change rapidly due to climate change, how S. alpinus and other salmonid populations will respond behaviorally and physiologically is of key interest from both a conservation and commercialization perspective, and attempts to understand the effects of environmental pressures on the species may need to include a model of their associated community of microflora, and how it interacts with its environment. My research uses 16S ribosomal RNA sequence data collected from gastro-intestinal tracts of individuals from populations in the Kitikmeot region of Nunavut, to explore the microbial community structure and key bacterial species associated with the gut of S. alpinus, how the composition of this community changes during migration, and how its diversity may be related to various demographic factors. The trends identified provide evidence that the dependency of gut community on the host’s environment, a phenomenon previously observed in salmonids in aquaculture, is something that holds true for wild salmonids living in relatively pristine natural environments.
The evolution of body size in endotherms and ectotherms; or, why they might not be giants
Strong selection and abundant genetic variation appear to be widespread in nature. Adaptive phenotypic evolution should therefore be common. Yet, stasis tends to dominate the temporal dynamic of traits in natural populations. This is the paradox of stasis. Additionally, for body size, not only is selection strong, it is typically positive. There is therefore an additional dimension to the paradox of stasis for body size: not only should we expected widespread adaptive evolution, we should expect a trend towards the evolution of larger size. Contrary to this expectation, body size does not respond to directional selection in contemporary populations. Drawing from the principles of life-history evolution, I outline a potential resolution to the size paradox. I test this hypothesis by reanalyzing phenotypic selection data, and by performing phylogenetically explicit analyses in the Amphibia. A new understanding of body-size evolution emerges, one that depends critically on life-history trade-offs, maternal effects, and oxygen limitation. The sum of this work underlines the importance of life-history and maternal effects in understanding patterns of body-size evolution at micro- and macro-evolutionary timescales.
This we welcome Manisha Kulkarni, in Biosciences room 3110.
Disease ecology in action: focus on vector-borne pathogens
Lyme disease and West Nile virus are transmitted to humans by the bite of an infected tick or mosquito, respectively. The ecology of these diseases is complex, with a number of vertebrate host species serving as disease reservoirs. Environmental factors largely determine their distribution and dynamics through impacts on host and vector populations. Dr. Kulkarni’s research at the Interdisciplinary Spatial Informatics for Global Health (INSIGHT) lab combines field and laboratory studies with spatial and statistical modelling in order to better understand vector-borne disease ecology and epidemiology in Canada and abroad. These studies help to identify spatiotemporal patterns in vector populations and disease transmission to inform vector-borne disease surveillance and control strategies at the local scale.