Christopher Sutherland Chris Bernier Kimberly Royar Jillian R. Kilborn Catherine Callahan Rachel Cliche Leighlan S. Prout Toni Lyn Morelli Alexej P. K. Siren 2021 <h3 id="jbi14112-sec-0001-title" class="article-section__sub-title section1">Aim</h3><p>In the face of global change, understanding causes of range limits are one of the most pressing needs in biogeography and ecology. A prevailing hypothesis is that abiotic stress forms cold (upper latitude/altitude) limits, whereas biotic interactions create warm (lower) limits. A new framework – Interactive Range-Limit Theory (iRLT) – asserts that positive biotic factors such as food availability can ameliorate abiotic stress along cold edges, whereas abiotic stress can have a positive effect and mediate biotic interactions (e.g., competition) along warm limits.</p><h3 id="jbi14112-sec-0002-title" class="article-section__sub-title section1">Location</h3><p>Northeastern United States</p><h3 id="jbi14112-sec-0003-title" class="article-section__sub-title section1">Taxon</h3><p>Carnivora</p><h3 id="jbi14112-sec-0004-title" class="article-section__sub-title section1">Methods</h3><p>We evaluated two hypotheses of iRLT using occupancy and structural equation modeling (SEM) frameworks based on data collected over a 6-year period (2014–2019) of six carnivore species across a broad latitudinal (42.8–45.3°N) and altitudinal (3–1451&nbsp;m) gradient.</p><h3 id="jbi14112-sec-0005-title" class="article-section__sub-title section1">Results</h3><p>We found that snow directly limits populations, but prey or habitat availability can influence range dynamics along cold edges. For example, bobcats (<i>Lynx rufus</i>) and coyotes (<i>Canis latrans</i>) were limited by deep snow and long winters, but the availability of prey had a strong positive effect. Conversely, snow had a strong positive effect on the warm limits of Canada lynx (<i>Lynx canadensis</i>), countering the negative effect of competition with the phylogenetically similar bobcat and with coyotes, highlighting how climate mediates competition between species.</p><h3 id="jbi14112-sec-0006-title" class="article-section__sub-title section1">Main conclusions</h3><p>We used an integrated dataset that included competitors and prey species collected at the same spatial and temporal scale. As such, this design, along with a causal modeling framework (SEM), allowed us to evaluate community-wide hypotheses at macroecological scales and identify coarse-scale drivers of species' range limits. Our study supports iRLT and underscores the need to consider direct and indirect mechanisms for studying range dynamics and species' responses to global change.</p> application/pdf 10.1111/jbi.14112 en Wiley Abiotic stress and biotic factors mediate range dynamics on opposing edges article