This week EEB welcomes Drs. Colautti & Eckert as a double header with both speakers hailing from our own multifaceted Department of Biology.
Invasions and extinctions ‘through the looking-glass’ of evolutionary ecology.
Strong genetic differentiation but not local adaptation towards a geographical range limit.
Speaker 1: Rob Colautti
Human activity is increasing rates of invasion and extinction, resulting in a homogenization of global biodiversity that may be mitigated by two distinct but complementary goals: (i) suppress long-term viability of invasive populations and (ii) increase population growth rates of endangered native species. Although eradication and enhancement are opposite conservation goals, invasions and extinctions represent two extreme outcomes along a single gradient of ecological success and therefore may be determined by the same core set of ecological and genetic factors. In other words, invasions and extinctions of closely related species may be like reflections in Lewis Carroll’s looking glass, with similar elements reflecting opposite realities. Both invasive and endangered species are challenged by strong demographic bottlenecks, hybridization with divergent lineages, and the demands of surviving and reproducing in novel and changing environments. Yet these common elements can lead to drastically different ‘realities’ or ecological outcomes, with invasive species expanding rapidly and endangered species spiralling towards extinction. Taking an eco-evolutionary perspective, I would like to discuss some of the key differences between invasive and endangered species that can account for the opposite ecological trajectories.
Speaker 2: Chris Eckert
The ecological and evolutionary mechanisms limiting species’ distributions are largely unknown. Stable range limits are expected if populations at the range edge have limited potential to adapt to extreme conditions. We tested this hypothesis by combining experimental transplants with population genetic analysis of the Pacific coast dune endemic Camissoniopsis cheiranthifolia (Onagraceae). Contrary to expectations, fitness increased towards the limit with highest fitness at and beyond the range edge. Genetic diversity did not decline towards the limit nor was there evidence for gene swamping of edge populations. Together, these results suggest range limitation via dispersal constraints. However, only at the broadest scale did we detect evidence of local adaptation, and edge populations were not best suited for expanding beyond the species’ range. These results challenge the commonly held assumption that stable range limits match niche limits, and also raise questions about the value of peripheral populations for expanding species’ geographical ranges.
The EEB Seminars run weekly, on Thursdays, in the EEB Lounge of the BioSciences Complex, Room 4338, from 12:30-1:30pm. Light refreshments are served starting at 12:15.