Mapping diversification metrics in macroecological studies: Prospects and challenges

Abstract

The intersection of macroecology and macroevolution is one of the most active research areas today. Macroecological studies are increasingly using phylogenetic diversification metrics to explore the role of evolutionary processes in shaping present-day patterns of biodiversity. Evolutionary explanations of species richness gradients are key for our understanding of how diversity accumulated in a region. For instance, the present-day diversity in a region can be a result of in situ diversification, extinction, or colonization from other regions, or a combination of all of these processes. However, it is unknown whether these metrics capture well these diversification and dispersal processes across geography. Some metrics (e.g., mean root distance -MRD-; lineage diversification-rate -DR-; evolutionary distinctiveness -ED-) seem to provide very similar geographical patterns regardless of how they were calculated (e.g., using branch lengths or not). The lack of appropriate estimates of extinction and dispersal rates in phylogenetic trees can limit our conclusions about how species richness gradients emerged. With a review of the literature and complemented by an empirical comparison, we show that phylogenetic metrics by itself are not capturing well the speciation, extinction and dispersal processes across the geographical gradients. Furthermore, we show how new biogeographic methods can improve our inference of past events and therefore our conclusions about the evolutionary mechanisms driving regional species richness. Finally, we recommend that future studies include several approaches (e.g., spatial diversification modelling, parametric biogeographic methods) to disentangle the relative the role of speciation, extinction and dispersal in the generation and maintenance of species richness gradients.

Tracing the diversification history of a Neogene rodent invasion into South America

“…A complex scenario arises from the multiple processes that determine species distributions across space, including speciation, extinction, and species dispersal as fundamental macroevolutionary processes, mediated at the assemblage level by vicariant events, niche evolution, and ecological filtering and competition, among other factors (Webb et al 2002, Wiens and Donoghue 2004, Fritz and Rahbek 2012. Understanding how these various processes contribute to any individual outcome necessarily involves the integration of both ecological and historical perspectives (Ricklefs 2004, Maestri et al 2018a, Velasco and Pinto-Ledezma 2018.…”

Effects of evolutionary time, speciation rates and local abiotic conditions on the origin and maintenance of amphibian montane diversity

“…The calculation of this metric considers the number of splitting events and the internode distances along the root‐to‐tip path of the phylogeny while giving greater weight to branches closer to the present (Jetz et al., 2012). We estimated this metric using a function implemented by Velasco and Pinto‐Ledezma (2018). Based on the tip speciation rates from the DR metric, we estimated the mean speciation rate for each mountain range based on their corresponding species assemblages.…”