Fast Spatial Species Accumulation Curves // High-performance spatial species accumulation curves using nearest-neighbor algorithms. Implements 'kNN' and 'kNCN' sampling methods with a 'C++' backend for speed. Supports Hill numbers (q=0,1,2), beta diversity partitioning (turnover/nestedness), coverage-based rarefaction and extrapolation, phylogenetic diversity (Faith's PD, mean pairwise distance, mean nearest taxon distance), functional diversity accumulation, diversity-area relationships (DAR), endemism-area curves, sampling-effort correction and fragmentation analysis, and species-area relationship (SAR) models based on extreme value theory (EVT). Multiple starting points (seeds) provide uncertainty quantification. Methods are described in 'Chao' et al. (2014) doi:10.1890/13-0133.1, 'Baselga' (2010) doi:10.1111/j.1466-8238.2009.00490.x, 'Chao' and 'Jost' (2012) doi:10.1890/11-1952.1, 'Faith' (1992) doi:10.1016/0006-3207(92)91201-3, 'Ma' (2018) doi:10.1002/ece3.4526, 'Borda-de-Agua' et al. (2025) doi:10.1038/s41467-025-59239-7, 'Hanski' et al. (2013) doi:10.1073/pnas.1311190110, and 'Jost' (2007) doi:10.1890/06-1736.1.