Abstract
With a glance, even the novice naturalist can tell you something about the ecology of a given ecosystem. This is because the morphology of individuals reflects their evolutionary history and ecology, and imparts a distinct ‘look’ to communities—making it possible to immediately discern between deserts and forests, or coral reefs and abyssal plains. Once quantified, morphology can provide a common metric for characterizing communities across space and time and, if measured rapidly, serve as a powerful tool for quantifying biotic dynamics. Here, we present and test a new high-throughput approach for analysing community shape in the fossil record using semi-three-dimensional (3D) morphometrics from vertically stacked images (light microscopic or photogrammetric). We assess the potential informativeness of community morphology in a first analysis of the relationship between 3D morphology, ecology and phylogeny in 16 extant species of planktonic foraminifera—an abundant group in the marine fossil record—and in a preliminary comparison of four assemblages from the North Atlantic. In the species examined, phylogenetic relatedness was most closely correlated with ecology, with all three ecological traits examined (depth habitat, symbiont ecology and biogeography) showing significant phylogenetic signal. By contrast, morphological trees (based on 3D shape similarity) were relatively distantly related to both ecology and phylogeny. Although improvements are needed to realize the full utility of community morphometrics, our approach already provides robust volumetric measurements of assemblage size, a key ecological characteristic.
Highlights
Speciation and extinction are population-level processes with global effects on biodiversity
Questions of biodiversity dynamics and their drivers are typically addressed at the species level in one of two ways [2]: (i) fitting models of diversification to modern and, rarely, fossil phylogenies (e.g. [3,4,5,6,7]) and (ii) assessing correlates of global diversity dynamics from fossil compilations and databases, like the Paleobiology Database (PBDB) (e.g. [8,9,10,11])
We use the computed tomography (CT) scans as a reference point to test the relationship between 3D morphology, ecology and phylogeny, and to test the relative information captured with the rapid semi-3D methods that we develop and introduce here
Summary
Speciation and extinction are population-level processes with global effects on biodiversity. A species ceases to be when the last individual of the last population dies, and a new species arises when two previously connected populations become sufficiently isolated [1] This being the case, assemblage dynamics should provide the most direct test of various regulators of biodiversity—be they environmental, biological or neutral—but this is almost never done in deep time. The role of various regulators is inferred from their endeffect on phylogenetic structure or standing diversity, with varying degrees of theoretical robustness to the inference (as discussed in [6,12]) For those few taxa that do have excellent fossil records, like marine microfossils [13], assemblage-level studies of populations through time offer the exciting possibility of testing evolutionary mechanisms hypothesized from other data types (see [14,15] for a macrofossil example)
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