Investigating the Relationship between Metabolic Rate and Extinction
Probability for Arthropoda, Brachiopoda, Echinodermata, and Mollusca
Phyla during the Cenozoic Era
Abstract
From extracting nutrients to releasing energy, biological metabolism
plays an integral role in determining evolutionary patterns of organisms
through geologic time. A previous study depicted a positive relationship
between metabolic rate and extinction probability for Mollusca within
the Neogene period. We hypothesized that this relationship extends to
other metazoan phyla during the Cenozoic Era. Using specific respiration
rates measured from living organisms and body size data for fossil taxa,
we estimated metabolic rates of animals across different phyla:
Arthropoda, Brachiopoda, Echinodermata, and Mollusca. This analysis was
performed at the class level by using the classes with the most data
available to represent each phylum: Malacostraca, Ostracoda, Cirripedia,
Rhynchonellata, Echinoidea, Bivalvia, Cephalopoda, and Gastropoda. We
then used logistic regression to estimate the relationship between the
calculated metabolic rates and extinction probability during each epoch
of the Cenozoic Era. Results indicate that while each individual phylum
has a different extinction probability across each epoch, the regression
coefficients for the combination of all studied phyla illustrate no
relationship since there is not enough evidence to reject the null
hypothesis of no relationship between metabolic rate and extinction
probability. Although this means that there is no significant
correlation for most of the phyla, there are some exceptions where
metabolism does affect extinction probability. During the Oligocene
epoch, animals within the Mollusca phylum portray a clear negative
correlation between metabolic rate and extinction probability. A
negative relationship is also observed for Echinoderms during the Eocene
epoch. Despite the crucial role that metabolism plays in species
survival, our results indicate that more information is needed regarding
specific environmental conditions in order to accurately predict the
factors that ultimately affect species survival across marine animals
within the Cenozoic Era.