The Spatial Distribution of Plant Biodiversity in the Greater Cape Floristic Region of South Africa: Comparing Distribution Models with Expert Range maps

Keywords: Species diversity, Spatial Pattern, South Africa
Session Type: Virtual Paper Abstract
Day: Sunday
Session Start / End Time: 2/27/2022 11:20 AM (Eastern Time (US & Canada)) - 2/27/2022 12:40 PM (Eastern Time (US & Canada))
Room: Virtual 56

Abstract

The Greater Cape Floristic Region (GCFR) of South Africa is well known for its plant biodiversity – it contains nearly 20% of Africa’s plant species in less than 0.5% of Africa’s total area. But, little is known about the spatial pattern of this biodiversity. This research compares the spatial patterns of biodiversity in the GCFR derived from species distribution models (SDM) and expert range maps and evaluates their performance in predicting species occurrence. Focusing on plant species from the Restionacea family, spatial patterns of species biodiversity from expert range maps and SDM predictions were mapped at 1-km resolution and then compared with independent presence/absence plot-level species data. We evaluated performances of expert range maps and SDM predictions in the 10th, 50th, and 75th percentile thresholds in several confusion matrix indices. We obtained spatial patterns of species richness, beta diversity, turnover, and nestedness. Spatial patterns derived from the expert range maps vary smoothly, in contrast, the patterns derived from SDM predictions capture fine-grain variability of the biodiversity hotspot. In beta diversity, lines are highlighted at the boundaries of species ranges because the coarse grain of the expert maps isolates the range boundaries, while from the SDM-derived ranges, areas with high beta value are distributed primarily along the mountain ridges. Combining the balanced accuracy and sensitivity, the predicted results in the 10th percentile threshold are considered more accurate than the 5th percentile threshold; however, we find contrary results in total accuracy and specificity.