Biotic and abiotic factors driving the diversification dynamics of Crocodylia

Abstract

Species diversity patterns are governed by complex interactions among biotic and abiotic factors over time and space, but are essentially the result of the diversification dynamics (differential speciation and extinction rates) over the long‐term evolutionary history of a clade. Previous studies have suggested that temporal variation in global temperature drove long‐term diversity changes in Crocodylia, a monophyletic group of large ectothermic organisms. We use a large database of crocodylian fossil occurrences (192 spp.) and body mass estimations, under a taxic approach, to characterize the global diversification dynamics of crocodylians since the Cretaceous, and their correlation with multiple biotic and abiotic factors in a Bayesian framework. The diversification dynamic of crocodylians, which appears to have originated in the Turonian (c. 92.5 Ma), is characterized by several phases with high extinction and speciation rates within a predominantly low long‐term mean rate. Our results reveal long‐term diversification dynamics of Crocodylia to be a highly complex process driven by a combination of biotic and abiotic factors which influenced the speciation and extinction rates in dissimilar ways. Higher crocodylian extinction rates are related to low body mass disparity, indicating selective extinctions of taxa at both ends of the body mass spectrum. Speciation rate slowdowns are noted when the diversity of the clade is high and the warm temperate climatic belt is reduced. Our finding supports the idea that temporal variations of body mass disparity, self‐diversity, and the warm climate belt size provided more direct mechanistic explanations for crocodylian diversification than do proxies of global temperature.

Vertebrae-Based Body Length Estimation in Crocodylians and Its Implication for Sexual Maturity and the Maximum Sizes

“…In the geologic time scale, macroevolutionary analysis of body size in extinct crocodyliforms can illuminate the rate and mode of the evolution and factors responsible for the long-term disparity patterns ( Godoy et al. 2019 ; Gearty and Payne 2020 ; Solórzano et al. 2020 ).…”

Investigating Biotic Interactions in Deep Time

“…During the diversification and decline phases, abiotic forcing is the primary factor controlling the loss and accumulation of species [55]. Further studies have similarly suggested that diversification rate is limited by within-clade diversity (and, by extension, intra-clade biotic interactions), while extinction rate may, most often, be set by abiotic factors [21,42,57,58].…”

“…Inferring the importance of biotic interactions on the basis of statistical rejection of abiotic factors is the most common approach employed by recent publications [24,42,46,58,59]. There are potential limitations to these modeling approaches (Table 1), and continued characterization of their statistical behavior will be important to assess validity.…”

“…As richness nears the carrying capacity of an island, species accumulation (immigration and origination) will slow due to niche saturation and niche incumbency. This is the basis for the concept of negative diversity dependence, wherein higher diversity suppresses origination (or increases extinction) on evolutionary timescales [21,55,58,59].…”

A new caimanine alligatorid from the Middle Eocene of Southwest Texas and implications for spatial and temporal shifts in Paleogene crocodyliform diversity

“…When both extinct and extant crocodyliform taxa are examined together, the clade displays a bimodal diversity distribution that roughly corresponds to the δ 18 O curve for the Cenozoic ( Markwick, 1998 ) and reflect the bimodal changes in global temperature during this time ( Mannion et al, 2015 ). Other factors may be driving this pattern ( Jouve et al, 2017 ; Solórzano et al, 2019 ; Celis, Narváez & Ortega, 2020 ), but climate is nonetheless viewed as a major factor influencing crocodyliform diversity patterns over time.…”