Desert lizard diversity worldwide: effects of environment, time, and evolutionary rate

Abstract

Biodiversity is not uniformly distributed across the Earth's surface, even among physiographically comparable biomes in different biogeographic regions. For lizards, the world's large desert regions are characterized by extreme heterogeneity in species richness, spanning some of the most species-rich (arid Australia) and species-poor (central Asia) biomes overall. Regional differences in species diversity may arise as a consequence of the interplay of several factors (e.g., evolutionary time, diversification rate, environment), but their relative importance for biogeographic patterns remains poorly known. Here we use distributional and phylogenetic data to assess the evolutionary and ecological drivers of large-scale variation in desert lizard diversity. We specifically test whether diversity patterns are best explained by differences in the ages of arid-adapted lineages (evolutionary time hypothesis), by regional variation in speciation rate, by geographic area of the arid systems, and by spatial variation related to environment (climate, topography, and productivity). We found no effect of recent speciation rate and geographic area on differences in desert lizard diversity. We demonstrate that the extreme species richness of the Australian deserts cannot be explained by greater evolutionary time, because species began accumulating more recently there than in more species-poor arid regions. We find limited support for relationships between regional lizard richness and environmental variables, especially temperature, but these effects were inconsistent across deserts. Our results provide evidence against several classic hypotheses for interregional variation in species richness, but also highlight the complexity of processes underlying vertebrate community richness in the world's great arid systems.

Evolutionary time and species diversity in aquatic ecosystems worldwide

“…However, comparisons can be made among geographic regions that are broadly similar in other climatic factors. Such inter‐regional analyses have been performed for deserts (Pianka, 1986; Tejero‐Cicuendez et al ., 2022), moist‐temperate forests (Latham & Ricklefs, 1993), tropical rainforests (Couvreur, 2015), and mediterranean biomes (Rundel et al ., 2016).…”

“…However, comparisons can be made among geographic regions that are broadly similar in other climatic factors. Such inter-regional analyses have been performed for deserts (Pianka, 1986;Tejero-Cicuendez et al, 2022), moist- (A) Pairwise comparison of richness for major invertebrate clades. The five most species-rich clades for both regions include the Amphipoda, Bryozoa, and Gastropoda.…”

A global analysis of viviparity in squamates highlights its prevalence in cold climates

“…For instance, oviparous species richness declines much more rapidly towards lower temperatures than that of viviparous taxa, suggesting stronger selection against oviparity at cold temperatures (Figure 3). Productive environments, in turn, can contain enough vacant niches, food and shelter for the dispersing viviparous lineages to thrive (Tejero‐Cicuéndez et al, 2022). Therefore, such environments are not expected to impose significant costs on the gravid female.…”

“…Productive environments, in turn, can contain enough vacant niches, food and shelter for the dispersing viviparous lineages to thrive (Tejero-Cicuéndez et al, 2022). Therefore, such environments are not expected to impose significant costs on the gravid female.…”

A new lizard species (Scincidae: Ctenotus) highlights persistent knowledge gaps on the biodiversity of Australia’s central deserts

“…Australia's arid lands harbor the most diverse lizard assemblages on Earth (Pianka 1969(Pianka , 1972Roll et al 2017;Tejero-Cicuéndez et al 2022). Nevertheless, new species continue to be described every year.…”