Niche overlap of competing carnivores across climatic gradients and the conservation implications of climate change at geographic range margins

Abstract

1 Co-first authors.There is considerable interest in factors controlling "warm-edge" limitsthe lower elevation and latitudinal edges of a species' range. Understanding whether conservation measures can mitigate anticipated change in climate requires consideration of future climate as well as species interactions. We explored niche relations of martens and fishers at their southern range margins to understand their spatial and temporal dynamics, and how they may be affected by climate change. We used large-scale non-invasive surveys and home range data from radio-marked individuals to explore the spatial dynamics of each species. Marten and fisher were allopatric in the northern/wetter regions but sympatric at intermediate latitudes with lower precipitation. In the driest/southernmost region only fishers occurred. Martens were not detected when annual precipitation was < 900 mm and rare where minimum temperatures exceeded 4ºC. Fishers were absent where spring snow was > 650 mm. Classification trees, accounting for multivariate interactions, supported these results. Where sympatric, ~70% of a marten's home range overlapped with at least one fisher but martens tended to avoid this area. In sympatry, marten expanded their niche into areas with reduced snowpack, warmer temperatures and uncharacteristic lower elevation habitats. Future climate scenarios predict conditions that favor fishers, but our data suggest martens may be capable of shifting their niche somewhat to warmer and less snowy habitats. The conservation of interacting species at their warm range limits will require land managers be aware of interspecific tolerance, how each may respond uniquely to future climates, and how potential climate refugia can be integrated with existing habitat.Understanding the causes of shifts in range limits is a fundamental issue for ecology and conservation (Sexton et al. 2009). Range limits can be a testing ground to understand the environmental conditions to which populations can adapt (Brown et al. 1996, Sexton et al. 2009 and the conditions that we need to preserve and connect as climate changes. "Warm-edge" limits the margins of a species' range that are closest to the equator or at the species' lower elevational limitsare very likely to be affected by climate change and biotic factors such as competition for resources and predation that accompany these changes (Cahill et al. 2014, Louthan et al. 2015. Consequently, predicting how range limits might respond to climate change requires evaluation of both climatic factors and species interactions.North American martens (Martes americana and M.caurina) and the fisher (Pekania pennanti) are good subjects for the study of distributional patterns because important biotic and abiotic effects on their geographic ranges have previously been explored. Additionally, both species are the focus of conservation concerns with the southern Sierra Nevada fisher population under consideration as a threatened species at both the state and federal level, and marten designated a sensitive s...

Interactive range‐limit theory (iRLT): An extension for predicting range shifts

“…Another study found that porcupines Erethizon dorsatum had lower survival in the presence of a recolonizing carnivore (fisher), and this was exacerbated during severe winter weather (Pokallus & Pauli, ). Additionally, the recolonization or reintroduction of martens to historical locales indicates that a combination of factors, including climate, competition with sympatric carnivores and prey availability forms their lower limit (Carlson et al, ; Manlick, Woodford, Zuckerberg, & Pauli, ; Zielinski, Tucker, & Rennie, ). One of the most interesting examples includes wolverines Gulo gulo in North America whose lower limit is positively associated with deep snowpack that is hypothesized to help preserve cached food and provide protection from competitors (Inman, Magoun, Persson, & Mattisson, ).…”

Abiotic conditions mediate intraguild interactions between mammalian carnivores

“…Despite the long history of observations regarding marten–fisher interactions and general acceptance of the idea that fishers limit marten populations through IG interactions, unless they are themselves limited by deep snowpack (Krohn et al, ), this potential exemplar of how asymmetrical IG interactions can lead to species coexistence or competitive exclusion remains poorly documented. In particular, the distributions of marten and fisher have not been assessed at a fine enough spatial resolution across large enough spatial scales to quantify their presence and/or coexistence across broad gradients in abiotic and biotic conditions (but see Fisher et al, ; Zielinski, Tucker, & Rennie, ). Here, we assess the biotic and abiotic drivers of the distribution of these two mesocarnivores and infer relative abundance using spatially explicit used–unused location, age and harvest data across an ecoregional scale (~30,000 km 2 ) that includes areas where fishers and martens co‐occur as well as areas where only fishers are present.…”

Present‐day and future contribution of climate and fires to vegetation composition in the boreal forest of China

“…Zielinski et al. () suggested that competition for resource was a significant control on “warm‐edge” limits based on large‐scale non‐invasive surveys and home range data (Zielinski et al. ).…”

“…() suggested that competition for resource was a significant control on “warm‐edge” limits based on large‐scale non‐invasive surveys and home range data (Zielinski et al. ). Resource competition among PFTs in DGVMs, including water, light, nutrients, and individual response to disturbance (e.g., fire), impacts their relative FPC in each grid cell yearly (Sitch et al.…”