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

further recommendations). We talked to residents, describing our survey rationale and meth- ods and asked about yard management. Residents were provided with a one-page fact sheet with information about land snail ecology and urban land snails. Following surveys, we again met with residents to go over the diversity of snails found in their yards (a surprise to many residents). This research project was determined to not be human research by the University of Oklahoma IRB and, consequently, the IRB also waived the need for informed consent. Surveys were conducted between in the spring and early summer (inclusive dates were 28 April to 29 June) during 2017 and 2018 (S1 Table) and consisted of one, 80-minute timed visual survey of each yard. Habitats surveyed included under leaf litter, especially leaf litter under shrubs; under wooden boards, pots on the ground, and debris; along raised edges (e.g., along walls of structures, plant bed edging, and driveways); and beneath ground-covering plants. In addition to visual searching, a surface soil sample, measuring approximately 0.5 l, was collected in at least two areas in each yard with visible accumulations of micro-snail shells or, where such accumulations were not apparent, from habitats where micro-snails or their shells were commonly found (e.g., friable soil at the base of buildings). Visual surveys and soil collections included both front and back yards. Larger live snails were generally provisionally identified, counted and released; empty shells

and unidentified live snails and were retained for definitive identification, and for matching with the provisionally identified live snails. Examples of slugs and most live micro-snails were also collected. Collected soil surface samples were dried and checked for micro-snails under magnification. Occasionally, snails were reared to enable identification (e.g., when only imma- ture polygyrids were found). The following snail identification guides were consulted: Pilsbry [31]; Burch [32]; Hubricht [28 and 33]; Perez and Cordeiro [34]; Nekola and Coles [35]; Grimm, Forsyth [36]; and Hotopp et al. [37]. Difficulties arose in the identification for a few taxa and are summarized as follows: Strobilops spp. included both S. texasiana and S. labyrinthica, Gastrocopta armifera and Gastrocopta abbreviata were combined, as were Vallonia pulchella and V. excentrica (both Fig 2. Climatic gradients across the study area. (A) Total average yearly rainfall (in cm/yr) increases from east to west and (B) winter temperatures (˚C: shown as mean monthly low temperature, which occurred in Jan) decreases from south to north. Small circles show locations of surveyed towns. https://doi.org/10.1371/journal.pone.0234830.g002 PLOS ONE Diversity patterns of yard-dwelling snails across climate gradients PLOS ONE | https://doi.org/10.1371/journal.pone.0234830 August 28, 2020 4 / 18