Coherence of Terrestrial Vertebrate Species Richness with External Drivers Across Scales and Taxonomic Groups

Abstract

Disentangling contributions from co-varying environmental variables is likely crucial for understanding the drivers of biodiversity patterns, including latitudinal diversity gradients. Here, we describe a novel use of wavelet power spectra to separate wavelength-dependent trends as a function of position on Earth's surface. Spectra reveal scale- and location- dependent coherence between species richness and topography (E), mean annual precipitation (Pn), temperature (Tm) and annual temperature range (ΔT). Greater than 97% of species richness of carnivorans, bats, songbirds, hummingbirds and amphibians (which encompass 2/3 of terrestrial vertebrate species) are generated at large scales, i.e. wavelengths ≥ 103 km. 30-69% is generated at scales ≥ 104 km. At these scales, richness across the Americas, the longest transect examined, tends to be highly coherent and anti-phase with E and ΔT (i.e. one high, the other low), and in-phase with Pn and Tm (e.g. both high or both low). Coherence between carnivorans and ΔT is low across all scales, which suggests insensitivity to seasonal temperature variations. By contrast, amphibian richness is strongly anti-correlated with ΔT at large scales. At scales ≤ 103 km, examined taxa, except carnivorans, show highest richness within the tropics. Terrestrial plateaux (e.g. Colorado, Altiplano) are foci of high coherence between carnivorans and E at scales ~ 103 km, which is consistent with the notion that large-scale tectonic processes contribute to local biodiversity, even for carnivorans. These results are similar to those obtained from transects across Africa, Eurasia, Australia and average global latitudinal transects. They highlight scale-dependent sensitivities of mammal, bird and amphibian populations to local environments and global climate.

Diversity gradients of terrestrial vertebrates – substantial variations about a common theme

“…Most studies that examined richness–environment relationship of terrestrial vertebrates were confined to one or two tetrapod classes (Allen et al., 2002; Araújo et al., 2008; Barreto et al., 2019; Costa et al., 2007; Evans et al., 2005; Foody, 2004; Fritz et al., 2016; Hawkins & Porter, 2003; Kerr & Packer, 1997; Qian et al., 2007; Rahbek & Graves, 2001; Rodríguez et al., 2005), or involve birds, mammals, and amphibians (Belmaker & Jetz, 2011; Bohdalková et al., 2021; Buckley & Jetz, 2007; Davies et al., 2007; Gouveia et al., 2013; Grenyer et al., 2006; Gudex‐Cross et al., 2022; Hawkins et al., 2007, 2012; Hortal et al., 2008; O'Malley et al., 2023; Wu & Liang, 2018). Studies that incorporate all tetrapods (including reptiles) have usually been confined to one region (Currie, 1991; Lewin et al., 2016; Powney et al., 2010; Tallowin et al., 2017; Whittaker et al., 2007).…”