Biodiversity across the Greater Cape Floristic Region

Aim: With plant biodiversity under global threat, there is an
urgent need to monitor the spatial distribution of multiple axes of
biodiversity. Remote sensing is a critical tool in this endeavor. One
remote sensing approach in detecting biodiversity is based on the
hypothesis that the spectral diversity of plant communities is a surrogate
of multiple dimensions of biodiversity. We investigated the generality of
this “surrogacy” for spectral, species, functional, and phylogenetic
diversity across 1,267 plots in the Greater Cape Floristic Region (GCFR),
a hyper-diverse region comprising several biomes and two adjacent global
biodiversity hotspots. Location: The GCFR centered in
southwestern and western South Africa. Time Period: All data were
collected between 1978–2014. Major taxa studied: Vascular plants
within the GCFR. Methods: Spectral diversity was calculated using
leaf reflectance spectra (450–950 nm) and was related to other dimensions
of biodiversity via linear models. The accuracy of
different spectral diversity metrics was compared using ten-fold
cross-validation. Results: We found that a distance-based
spectral diversity metric was a robust predictor of species, functional,
and phylogenetic biodiversity. This result serves as a
proof-of-concept that spectral diversity is a potential surrogate of
biodiversity across a hyper-diverse biogeographic region. While our
results support the generality of spectral diversity as a biodiversity
surrogate, we also find that relationships vary between different
geographic subregions and biomes, suggesting that differences in
broad-scale community composition can affect these relationships. Main
Conclusions: Spectral diversity was shown to be a robust
surrogate of multiple dimensions of biodiversity across biomes and a
widely varying biogeographic region. We also extend these
surrogacy relationships to ecological redundancy to demonstrate the
potential for additional insights into community structure based on
spectral reflectance.