Document Detail

Escalation and extinction selectivity: morphology versus isotopic reconstruction of bivalve metabolism.
MedLine Citation:
PMID:  11926496     Owner:  NLM     Status:  MEDLINE    
Studies that have tested and failed to support the hypothesis that escalated species (e.g., those with predation-resistant adaptations) are more susceptible to elimination during mass extinctions have concentrated on the distribution and degree of morphological defenses in molluscan species. This morphological approach to determining level of escalation in bivalves may be oversimplified because it does not account for metabolic rate, which is an important measure of escalation that is less readily accessible for fossils. Shell growth rates in living bivalves are positively correlated with metabolic rate and thus are potential indicators of level of escalation. To evaluate this approach, we used oxygen isotopes to reconstruct shell growth rates for two bivalve species (Macrocallista marylandica and Glossus markoei) from Miocene-aged sediments of Maryland. Although both species are classified as non-escalated based on morphology, the isotopic data indicate that M. marylandica was a faster-growing species with a higher metabolic rate and G. markoei was a slower-growing species with a lower metabolic rate. Based on these results, we predict that some morphologically non-escalated species in previous tests of extinction selectivity should be reclassified as escalated because of their fast shell growth rates (i.e., high metabolic rates). Studies that evaluate the level of escalation of a fauna should take into account the energetic physiology of taxa to avoid misleading results.
Gregory P Dietl; Patricia H Kelley; Reese Barrick; William Showers
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Publication Detail:
Type:  Comparative Study; Journal Article    
Journal Detail:
Title:  Evolution; international journal of organic evolution     Volume:  56     ISSN:  0014-3820     ISO Abbreviation:  Evolution     Publication Date:  2002 Feb 
Date Detail:
Created Date:  2002-04-02     Completed Date:  2002-09-27     Revised Date:  2008-06-04    
Medline Journal Info:
Nlm Unique ID:  0373224     Medline TA:  Evolution     Country:  United States    
Other Details:
Languages:  eng     Pagination:  284-91     Citation Subset:  IM    
Department of Zoology, North Carolina State University, Raleigh 27695-7617, USA.
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MeSH Terms
Geologic Sediments
Mollusca / anatomy & histology*,  classification,  growth & development,  metabolism
Oxygen Consumption
Species Specificity

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