Differential effects of climate and species interactions on range limits at a hybrid zone: potential direct and indirect impacts of climate change

Abstract

The relative contributions of climate versus interspecific interactions in shaping species distributions have important implications for closely related species at contact zones. When hybridization occurs within a contact zone, these factors regulate hybrid zone location and movement. While a hybrid zone's position may depend on both climate and interactions between the hybridizing species, little is known about how these factors interact to affect hybrid zone dynamics. Here, we utilize SDM (species distribution modeling) both to characterize the factors affecting the current location of a moving North American avian hybrid zone and to predict potential direct and indirect effects of climate change on future distributions. We focus on two passerine species that hybridize where their ranges meet, the Black‐capped (Poecile atricapillus) and Carolina (P. carolinensis) chickadee. Our contemporary climate models predict the occurrence of climatically suitable habitat extending beyond the hybrid zone for P. atricapillus only, suggesting that interspecific interactions primarily regulate this range boundary in P. atricapillus, while climatic factors regulate P. carolinensis. Year 2050 climate models predict a drastic northward shift in suitable habitat for P. carolinensis. Because of the greater importance of interspecific interactions for regulating the southern range limit of P. atricapillus, these climate‐mediated shifts in the distribution of P. carolinensis may indirectly lead to a range retraction in P. atricapillus. Together, our results highlight the ways climate change can both directly and indirectly affect species distributions and hybrid zone location. In addition, our study lends support to the longstanding hypothesis that abiotic factors regulate species' poleward range limits, while biotic factors shape equatorial range limits.

Implications of future bioclimatic shifts on Portuguese forests

“…The most economically relevant species, such as E. globulus and P. pinaster, can be relocated and/or progressively substituted by more suitable and environmentally sustainable species, or, in some occasions, by ameliorated hybrids or new genetically bred species that can provide similar economic incomes (Chhin 2015;McQuillan and Rice 2015). In this regard, it is worth mentioning the successful breeding programme of P. pinaster from a Portuguese seed source, improved for drought tolerance and dry-land afforestation in Western Australia (Butcher 2007).…”

Potential distribution of Notopterygium incisum Ting ex H. T. Chang and its predicted responses to climate change based on a comprehensive habitat suitability model

“…In its natural habitats, N. incisum is not the dominant species and is usually an associated species that grows in alpine shrublands, alpine meadows, and woodlands (Mcquillan & Rice, ). Hence, the vegetation types are the important limiting factors, reflecting the limitations of the species' migration ability, and here, according to the literature, we conducted binary conversion of the vegetation type data.…”

Incorporating movement in species distribution models

“…These conceptualizations of M within the BAM framework have led to an increased understanding of model interpretation, (Barve et al 2011;Saupe et al 2012;Qiao et al 2015), with a number of studies explicitly acknowledging M when defining modelling extent, pseudo-absence selection or model validation (Belaire et al 2014;Escobar et al 2104;Strubbe et al 2015;McQuillan and Rice 2015;Mateo et al 2015;Bradley et al 2015).…”