Predicting future habitat suitability for the Balfourianae pines in the face of climate change using species distribution modeling

Katherine Alise Van

Biotic Interactions may influence species distribution patterns, particularly at the edge of their range, but remain poorly studied. In particular, we lack understanding of how climate may mediate interactions between species. I studied spatial and temporal associations of Canada lynx (Lynx canadensis) with their primary prey species (snowshoe hare; Lepus americanus) and potential competitors (bobcats; Lynx rufus, and cougars; Puma concolor) along their southern range edge in northern Washington. Although anecdotal evidence of these competitive interaction exists, rigorous research remains absent from the literature. I collected presence/absence data on these species from 2014-2016 across a 551 km2 landscape using camera-traps along an elevation gradient in both snow-on and snow-off seasons. Then, using single and two-species occupancy models, I used the data to examine three predictions: 1) lynx occupancy is related to snowshoe hare availability, 2) distribution overlap between the sympatric felids will be greatest in snow-off time periods, and 3) there will be evidence of spatial or temporal avoidance of bobcats and cougars by lynx. Single-species models revealed probability of occupancy was best modeled using abiotic and prey covariates for Canada lynx and abiotic covariates for bobcats and cougar. The camera-trapping data revealed that spatial overlap of the three felids species increased during snow-off time periods. Based on two-species occupancy models Canada lynx showed a decrease in probability of occupancy when bobcats were present at cameras, although this effect was scale dependent and did not vary between seasons. No effect of cougar occupancy on lynx occupancy was seen during either season. All species had high levels of overlap in activity throughout the year. Taken together, these results suggest that biotic interactions are partly shaping large-scale lynx distribution patterns. The strong relationship of lynx occupancy to snowshoe hare demonstrates the importance of this prey species in shaping lynx habitat use. Observed negative interactions with bobcats at camera sites provides empirical support for interactions between these species from modeling and anecdotal evidence. Given these results, increasing temperatures and loss of snow may result in a combination of habitat isolation and potential for increased competitive interactions for lynx at their southern range edge. suitability maps indicate that the Balfourianae pines are at risk of decreasing levels of habitat suitability throughout their range and within protected areas, that the poor dispersal abilities of these pines will be an additional limiting factor, and that they will face increasing overlap with their two pests in the future. Taken together, these results suggest that Balfourianae pine populations will be increasingly stressed as the climate changes, and that currently protected areas and conservation strategies may not be sufficient. Therefore, in the face of a changing climate, additional conservation strategies, such as assisted migration, additional monitoring for pest species, or "release" of conservation sites may be needed.

Predicting future habitat suitability for the Balfourianae pines in the face of climate change using species distribution modeling

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