Using a theoretical ecospace to quantify the ecological diversity of Paleozoic and modern marine biotas

Abstract

The process of evolution hinders our ability to make large-scale ecological comparisons—such as those encompassing marine biotas spanning the Phanerozoic—because the compared entities are taxonomically and morphologically dissimilar. One solution is to focus instead on life habits, which are repeatedly discovered by taxa because of convergence. Such an approach is applied to a comparison of the ecological diversity of Paleozoic (Cambrian–Devonian) and modern marine biotas from deep-subtidal, soft-substrate habitats. Ecological diversity (richness and disparity) is operationalized by using a standardized ecospace framework that can be applied equally to extant and extinct organisms and is logically independent of taxonomy. Because individual states in the framework are chosen a priori and not customized for particular taxa, the framework fulfills the requirements of a universal theoretical ecospace. Unique ecological life habits can be recognized as each discrete,n-dimensional combination of character states in the framework. Although the basic unit of analysis remains the organism, the framework can be applied to other entities—species, clades, or multispecies assemblages—for the study of comparative paleoecology and ecology. Because the framework is quantifiable, it is amenable to analytical techniques used for morphological disparity. Using these methods, I demonstrate that the composite Paleozoic biota is approximately as rich in life habits as the sampled modern biota, but that the life habits in the modern biota are significantly more disparate than those in the Paleozoic; these results are robust to taphonomic standardization. Despite broadly similar distributions of life habits revealed by multivariate ordination, the modern biota is composed of life habits that are significantly enriched, among others, in mobility, infaunality, carnivory, and exploitation of other organisms (or structures) for occupation of microhabitats.

The multidimensionality of the niche reveals functional diversity changes in benthic marine biotas across geological time

“…This region was chosen because it represents one of the exceedingly few modern analogues for the tropical, epeiric (epicontinental) seaways in which the Palaeozoic samples were deposited. In order to have a similar scope of coverage between the three intervals, only commonly fossilized taxa were included here (Novack‐Gottshall 2007). Finally, because many fossil occurrences can only be identified to genus level, all analyses were conducted at this taxonomic level.…”

“…The combinatorial flexibility of multiple modes within each functional trait allows a rich number of even subtly distinct functional entities to be characterized. As an example, consider the enormous variety of algae‐eaters, all of which share a microbivorous diet (Novack‐Gottshall 2007); depending on how additional traits are classified, the new framework allows distinctions between byssate mussels (facultatively mobile, attached, supported, particle‐feeding, filter‐feeders on typically hard lithic substrates), algal‐mat‐grazing limpets [intermittently mobile, free‐living, bulk‐feeding (because ingest intact food), mass‐feeders (defined by ingesting food en masse ) on typically hard lithic substrates], burrowing deposit‐feeding nuculoid bivalves (intermittently mobile, free‐living, particle‐feeding mass‐feeders living within soft lithic substrates), and kelp‐browsing gastropods [intermittently mobile, free‐living, supported, bulk‐feeding, raptorial feeders (because actively seize and manipulate individual food items) living on biotic substrates]. Additional details and examples of the versatility of the classification framework are available in Novack‐Gottshall (2007): especially pp.…”

“…2007; Bush et al. 2007; Novack‐Gottshall 2007) but quantitative assessments of temporal trajectories for both alpha and beta components of functional diversity are still missing.…”

Modelling the ecological–functional diversification of marine Metazoa on geological time scales

“…Ecological complexity increased during the evolutionary radiations of the Ediacaran and Phanerozoic [1][2][3][4][5][6][7] as animals began to interact with the environment and each other in diverse ways. Here, we discuss several models of ecological-functional diversification that may describe the history of the marine Metazoa.…”

Community ecology of the Middle Miocene primates of La Venta, Colombia: the relationship between ecological diversity, divergence time, and phylogenetic richness

“…Studies of primate communities over the past decade have used multivariate ''ecospace'' to describe the ecological diversity that characterizes a given community (e.g., Fleagle and Reed 1996;Godfrey et al 1997;Gilbert 2005; see also Novack-Gottshall 2007). A community's ecospace can be defined as the space it takes up on multivariate axes that represent a variety of ecological variables (including diet, locomotor and positional behavior, activity pattern, and body size) and describe the niche of each species present in the community (see Fleagle and Reed 1996).…”