The interaction between the Linnean and Darwinian shortfalls affects our understanding of the evolutionary dynamics driving diversity patterns of New World coralsnakes

Abstract

In this study, we sought to understand how the Linnean shortfall (i.e., the lack of knowledge about species taxonomy) interacts with the Darwinian shortfall (i.e., the lack of knowledge about phylogenetic relationships among species), potentially jeopardizing geographical patterns in estimates of speciation rates, using New World coralsnakes as a case study. For this purpose, we created an index of taxonomic uncertainty that measures the likelihood of current species being split after undergoing future taxonomic revisions. Next, we conducted simulations in which branches of species with high taxonomic uncertainty are split in the phylogenetic trees to generate new hypothetical species along their geographic ranges. We found that a high number of coralsnake species display substantial taxonomic uncertainty, positively correlated with the latitude of the species’ geographical range centroid. The estimated speciation rates based on currently available data have a weak relationship with latitude. However, after incorporating taxonomic uncertainty into the phylogeny, we detect a higher positive correlation between speciation rate and latitude. This shift demonstrates that taxonomic uncertainty can undermine empirical evaluation of the geographical pattern estimates in speciation rates, revealing an interaction between the latitudinal taxonomic gradient and the latitudinal diversity gradient. Given that taxonomic changes can alter the number of species recognized as valid over time, our study highlights the need to incorporate taxonomic uncertainty into macroecological and macroevolutionary studies, enhancing the robustness of patterns inferred from these data.