Palaeontology meets metacommunity ecology: the Maastrichtian dinosaur fossil record of North America as a case study

Abstract

Documenting the patterns and potential associated processes of ancient biotas has always been a central challenge in palaeontology. Over recent decades, intense debate has focused on the organization of dinosaur-dominated communities, yet no general consensus has been reached on how these communities were organized in a spatial context. Here, we used analytical routines typically applied in metacommunity ecology to provide novel insights into dinosaurian distributions across the latest Cretaceous of North America. To do this, we combined fossil occurrences with functional, phylogenetic and palaeoenvironmental modelling, and adopted the perspective that more reasonable conclusions on palaeoecological reconstructions can be gained from studies that consider the organization of biotas along ecological gradients at multiple spatial scales. Our results showed that dinosaurs were restricted in range to different parts of the Hell Creek Formation, prompting the recognition of discrete and compartmentalized faunal areas during the Maastrichtian at fine-grained scales, whereas taxa with the broadest ranges included those with narrower distributions when combining data from various geological formations across the Western Interior of North America. Although groups of dinosaurs had coincident range boundaries, their communities responded to multiple ecologically-important gradients when compensating for differences in sampling effort. Metacommunity structures of both ornithischians and theropods were correlated with climatic barriers and potential trophic relationships between herbivores and carnivores, thereby suggesting that dinosaurian faunas were shaped by physiological constraints, limited food resources abundance, and a combination of bottom-up and top-down forces across multiple spatial grains and extents.

Size-driven preservational and macroecological biases in the latest Maastrichtian terrestrial vertebrate assemblages of North America

“…As the Hell Creek Formation and equivalent beds provide a fossiliferous, accessible, and meter-scale framework for detailed diversity studies, these deposits have served as the model for understanding the tempo and mode of terrestrial vertebrate extinctions at the K/Pg for well over three decades (Pearson et al 2002; Russell and Manabe 2002; Horner et al 2011; Lyson et al 2011; Tobin et al 2014; Wilson et al 2014a; Sprain et al 2015; Fastovsky and Bercovici 2016; DePalma et al 2019; García-Girón et al 2021). Meter-scale analyses of the diversity/richness, taxonomic composition, and relative abundances of individual taxa leading up to and through the K/Pg boundary include mammals (Wilson 2005, 2014; Wilson 2013; DeBey and Wilson 2014, 2017), amphibians (Wilson et al 2014b), turtles and lizards (Longrich et al 2012; Holroyd et al 2014), and dinosaurs (Sloan et al 1986; Sheehan et al 1991, 2000; Fastovsky and Sheehan 2005; Fastovsky and Weishampel 2005; Horner et al 2011; Longrich et al 2011; Lyson et al 2011; Stein 2019), as well as the entire fauna (Pearson et al 2002; DePalma et al 2019).…”

Shifts in food webs and niche stability shaped survivorship and extinction at the end-Cretaceous

“…S1 and S2). In this study, nodes represent different trophic guilds according to the ecology, body size, and habitat preferences of taxa (34,37,48,49), and links (i.e., edges) represent the empirical dependencies between β-diversities of certain paleocommunity types (see Materials and Methods). Briefly, (A) our dataset represents the record of North American tetrapod faunas, in which taxa were assigned to different trophic guilds using three ecological parameters (broad habitat-use types, body size, and feeding habits).…”

“…On the other hand, trophic habits refer to the diet and food processing strategies of an animal, and it generally includes three primary categories, i.e., herbivores, faunivores, and omnivores. In the present study, we assigned body size (i.e., large, medium, small, and very small) and feeding habit (i.e., herbivore, faunivore, and omnivore) divisions integrating data from several comprehensive datasets [e.g., (10,34,37,73,97,98)]. Following Mitchell et al (37), we assigned taxa to trophic guilds based on adult representatives, which allowed us to represent the complete potential dietary suite of members, thereby producing complex but realistic interaction networks (see table S1 for examples).…”

“…These questions can be addressed by modeling long-term patterns in food webs (31,32) and ecospace occupancy dynamics (i.e., the multidimensional combination of paleoenvironmental conditions under which species developed) (29,33). Direct fossil evidence of trophic interactions is still limited (32,34), but methodological advances in network theory (35) and ecological niche partitioning (36) might hold the key to long-standing questions about food web stability and the functional roles of species in ancient ecosystems, both of which are at the core of modern evolutionary and ecological research (34,(37)(38)(39). Although the application of these emerging approaches is not yet commonplace in paleontology, a few studies have demonstrated that they are ideal tools for revealing species habitat distributions in deep time (6,29,33,40) and the tempo and mode of ecological reorganization after mass extinctions (37)(38)(39).…”

Metacommunity analyses show an increase in ecological specialisation throughout the Ediacaran period

“…Because the connectivity of these Ediacaran communities via dispersal has been established, here we define metacommunities as sets of fossil localities (communities), which are connected by the dispersal of many species [ 29 ]. The EMS framework is a hierarchical analysis that identifies properties in site-by-taxa presence/absence matrices, which are related to the underlying processes shaping taxa distributions [ 31 ], but to date has limited application to the fossil record [ 36 ]. Three metacommunity metrics are calculated to determine the structure: coherence, turnover, and boundary clumping [ 29 – 31 ], which are hierarchical rather than independent of each other.…”