2014 GSA Annual Meeting in Vancouver, British Columbia (19–22 October 2014)

Paper No. 22-9
Presentation Time: 10:00 AM



, dsf88@cornell.edu

Species may be placed on a spectrum of specialization and those that have relatively tightly defined niches and a narrow range of environmental tolerance - are thought to be highly adapted to very specific circumstances. Traits influencing degree of specialization are inferred to potentially have a great influence on species’ evolutionary dynamics, patterns, and trends. A number of studies by both paleontologists and neonatologists investigate the macroevolutionary effects of ecological traits and although vocabulary is shared, neo- and paleo- specialization are admittedly different but assumed to be related. The types of evidence available dictate the limits of our understanding the terms. Neontologists frequently use specialization to mean a high degree of biotic ecological niche depth or breadth. Meanwhile, paleontologists’ specialists are frequently defined by abiotic variables, such as facies dependence, geographic range, and environmental tolerance. In some instances, generalists and specialists more specifically refer to the dichotomous concepts of eurotopy and stenotopy, respectively. But to what degree do these concepts overlap?

Previous work quantified specialization in fossil clades using the range of facies occurrences as a proxy for niche breadth. A sliding scale termed the Eurytopy Index (EI) represents the number of recorded facies for each species. The EI of a clade is the mean number of facies occupied by the species within a clade. Species with a wide range of facies occurrences were assumed to have had wide niche breadth and, thus, were more or less generalist species. EI is a way to quantify a certain kind of specialization but it remains to be seen if paleontological specialists equal in any meaningful way to neontological specialists.

To test the degree to which these concepts overlap, EI was calculated for extant neogastropod clades. Subsequently, an extensive literature review provided information on the diets of the same clades. Preliminary results suggest facies dependence may be an abiotic proxy for tropic specialization but because other influences (refugia from predators, physiological restraints, basinal containment of endemics, latitudinal clines of competition) cannot be ruled out. Implications for paleontologists and neonatologists are discussed.