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

which are much larger than Oklahoma). With the addition of sites in Kansas to increase the temperature range, we captured a relatively large climatic range within a relatively small area. The twelve selected towns formed a 3 x 4 grid pattern (Fig 1) and encompassed an East- West rainfall gradient (Fig 2A and S1 Table) and a North-South temperature gradient (Fig 2B). Town populations ranged from about 6,500 to 122,000 (S1 Table). Climate data for towns were characterized by the mean annual rainfall and the mean monthly low temperature of the coldest month (January) over a 20-year period (1999–2018). Climate data were obtained using the NOWData database [NOAA on-line Weather Data; 29], where data were available for all towns except Ardmore, for which data from the Oklahoma Mesonet [30] were used. Selection of survey yards We relied on three methods to find yards to survey: previous contacts, contacting the local branch of state agricultural extension program prior to our visit and asking them post a Face- book message eliciting participants, and snowballing (asking contacts or participants for Fig 1. Map of the 12 surveyed towns in Kansas (KS) and Oklahoma (OK). https://doi.org/10.1371/journal.pone.0234830.g001 PLOS ONE Diversity patterns of yard-dwelling snails across climate gradients PLOS ONE | https://doi.org/10.1371/journal.pone.0234830 August 28, 2020 3 / 18