Climate gradients, and patterns of biodiversity and biotic homogenization in urban residential yards

RESEARCH ARTICLE Climate gradients, and patterns of biodiversity and biotic homogenization in urban residential yards Elizabeth A. BergeyID*, Benjamin E. Whipkey Oklahoma Biological Survey and Department of Biology, University of Oklahoma, Norman, Oklahoma, United States of America * lbergey@ou.edu Abstract Residential yards constitute a substantive biodiverse greenspace within urban areas. This biodiversity results from a combination of native and non-native species and can contribute to biotic homogenization. Geographical climatic patterns affect the distribution of native spe- cies and may differently affect non-native species. In this study, we examined biodiversity and biotic homogenization patterns of yard-dwelling land snails across 12 towns in Okla- homa and Kansas (USA). The 3 x 4 array of towns incorporated a N-S winter temperature gradient (mean low January temperature range = -8.4 to 0.1˚C) and an E-W annual rainfall gradient (annual rainfall range = 113.8 to 61.3 cm/yr). Ten yards per town were surveyed. We hypothesized that mild winter temperatures and greater annual rainfall would be associ- ated with greater snail abundance and richness, and that the presence of non-native spe- cies would contribute to biotic homogenization. Non-native snails were present and often abundant in all towns. Snail communities varied with both rainfall and cold temperature. Contrary to our prediction, snail abundance was inversely related to annual rainfall–likely because drier conditions resulted in greater yard watering that both augmented rainfall and

maintained moist conditions. Sørensen similarity between towns for the entire land snail community and for only non-native species both showed distance-decay patterns, with snail composition becoming less similar with increasing distance—patterns resulting from spe- cies turnover. The biotic homogenization index also showed a distance-related pattern, such that closer towns were more likely to have biotic homogenization whereas more distant towns tended to have biotic differentiation. These results support the concept that biotic homogenization is more likely regionally and that climatic changes over distance result in species turnover and can reduce spatially broad biotic homogenization. Introduction Biotic homogenization occurs when biotas become more similar through the processes of the loss or expansion of native species and the establishment of non-native species [1] and is con- sidered a global phenomenon [1, 2]. Urbanization has a high potential for producing biotic PLOS ONE PLOS ONE | https://doi.org/10.1371/journal.pone.0234830 August 28, 2020 1 / 18 a1111111111 a1111111111 a1111111111 a1111111111 a1111111111 OPEN ACCESS Citation: Bergey EA, Whipkey BE (2020) Climate gradients, and patterns of biodiversity and biotic homogenization in urban residential yards. PLoS ONE 15(8): e0234830. https://doi.org/10.1371/ journal.pone.0234830 Editor: Thor-Seng Liew, Universiti Malaysia Sabah, MALAYSIA Received: May 22, 2020 Accepted: August 9, 2020 Published: August 28, 2020 Peer Review History: PLOS recognizes the benefits of transparency in the peer review

process; therefore, we enable the publication of all of the content of peer review and author responses alongside final, published articles. The editorial history of this article is available here: https://doi.org/10.1371/journal.pone.0234830 Copyright: © 2020 Bergey, Whipkey. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. Data Availability Statement: All relevant data are within the manuscript and its Supporting Information files. Funding: Funding was provided by the University of Oklahoma: SRI funds, Oklahoma Biological