Open Collections

Macklin, Rory Donald John

University of British Columbia

Species interactions influence species distributions. Thus, some have suggested that one can work backwards from patterns in a species’ distribution to detect a species interaction without a priori knowledge of its existence. One method of this application – the “natural removal experiment” – tests for patterns consistent with competitive exclusion and release by comparing a species’ habitat relationships in sympatry and allopatry with a potential competitor and inferring the effect of competition. Previously, this approach has been limited by the scales of data required, often stretching across entire regions; however, the expanding datasets available through community science efforts make this application more tractable. We revitalize the natural removal experiment approach by applying it to a case study to ask whether the Chestnut-backed Chickadee (Poecile rufescens; CBCH) is competitively excluded from or hindered in cities by the Black-capped Chickadee (P. atricapillus; BCCH) in the Pacific Northwest of North America. To assess this question, we used data from the community science project eBird, creating two subsets of observations of CBCH, one from a region where BCCH is absent, and another where BCCH is present. A species distribution model for CBCH relative abundance was built from each dataset, and the relationships to indicators of urbanization and natural forest were assessed. We found that, when isolated from BCCH, CBCH had more important, more positive relationships to urban indicators, and less important, less positive relationships to indicators of natural forest. Under an “imagined scenario” where BCCH was imagined to be absent from the entire study region, CBCH were predicted at higher abundances in cities and areas lacking natural forest, supporting the hypothesis that BCCH negatively affects the abundance of CBCH in these urban areas of sympatry. We highlight several critical caveats ensuring comparability of the two regions and eliminating alternate explanations for differences between the two regions. While this approach does not confirm the existence of an interaction in nature, it can be used to efficiently generate hypotheses or predictions to complement field studies. This method presents a significant opportunity for researchers to harness community science to form powerful investigations of species interactions at previously unattainable scales.

Text

2023-12-18

Attribution-NonCommercial-NoDerivatives 4.0 International

http://hdl.handle.net/2429/86966

Zoology

University of British Columbia

UBCV

http://creativecommons.org/licenses/by-nc-nd/4.0/