Climate connectivity of the bobcat in the Great Lakes region

Abstract

The Great Lakes and the St. Lawrence River are imposing barriers for wildlife, and the additive effect of urban and agricultural development that dominates the lower Great Lakes region likely further reduces functional connectivity for many terrestrial species. As the climate warms, species will need to track climate across these barriers. It is important therefore to investigate land cover and bioclimatic hypotheses that may explain the northward expansion of species through the Great Lakes. We investigated the functional connectivity of a vagile generalist, the bobcat, as a representative generalist forest species common to the region. We genotyped tissue samples collected across the region at 14 microsatellite loci and compared different landscape hypotheses that might explain the observed gene flow or functional connectivity. We found that the Great Lakes and the additive influence of forest stands with either low or high canopy cover and deep lake‐effect snow have disrupted gene flow, whereas intermediate forest cover has facilitated gene flow. Functional connectivity in southern Ontario is relatively low and was limited in part by the low amount of forest cover. Pathways across the Great Lakes were through the Niagara region and through the Lower Peninsula of Michigan over the Straits of Mackinac and the St. Marys River. These pathways are important routes for bobcat range expansion north of the Great Lakes and are also likely pathways that many other mobile habitat generalists must navigate to track the changing climate. The extent to which species can navigate these routes will be important for determining the future biodiversity of areas north of the Great Lakes.

Where and why are species' range shifts hampered by unsuitable landscapes?

“…There is relevant research on dispersal and inter‐population connectivity in long‐occupied landscapes (e.g., Fletcher et al, 2016; Gilbert‐Norton et al, 2010; Hartfelder et al, 2020; Resasco, 2019; Wright et al, 2020) which could be extrapolated to a multi‐generation, range‐shifting context. For example, landscape elements that are hostile may act to either retard or re‐route range expansion, and linear or stepping‐stone‐like configurations may act as conduits (Marrotte et al, 2020). Modelling has suggested that landscape “conductance” could be a useful summary metric of the speed of range shifts achievable, based on both the amount and the configuration of breeding habitat (Hodgson et al, 2012; Hodgson et al, 2016; Poniatowski et al, 2016).…”

Effects of cost surface uncertainty on current density estimates from circuit theory

“…The second output, current density, is a localized measure of movement probability at a spatially-referenced point that can be interpreted as the probability of a location being used during a random walk between a source and destination node. Current density can be mapped and is thus particularly useful for applications where mapped routes are of interest, such as in natural heritage planning (Koen et al, 2014), modeling animal movement routes (Walpole et al, 2012;Marrotte, Bowman & Wilson, 2020), or forecasting migration arising from shifts in climate (Lawler et al, 2013). Recently, Marrotte et al (2017) used current density to estimate at-site genetic connectivity of sampled nodes.…”

Seven decades of southern range dynamics of Canada lynx

“…In fact, Parker et al (1983) found that after several years of low snow the bobcat invaded the lowlands of Cape Breton while the Canada lynx left the area. Marrotte, Bowman, and Wilson (2020) found that deep winter snow in the Great Lakes region limited bobcat expansion northward, suggesting that greater expansion will result from additional climate warming. Recently, Peers et al (2020) found that while snow depth has decreased across their study area in the boreal forest, snowshoe hare survival decreased while predation by coyotes increased in areas with shallow snow.…”