A study of Pliocene to recent bivalves and gastropods from the Western Atlantic suggests laziness might be a fruitful strategy for survival of individuals, species and even communities of species.
Strotz et al focused on the high-resolution record of Pliocene to recent mollusks from the Western Atlantic.
For the study, University of Kansas researcher Luke Strotz and co-authors analyzed the metabolic rates (amount of energy the organisms need to live their daily lives) of 299 mollusk species.
“We wondered, ‘could you look at the probability of extinction of a species based on energy uptake by an organism’,” Dr. Strotz said.
“We used mollusks to study the phenomenon of metabolism’s contribution to extinction rates because of ample available data about living and extinct species,” he added.
“You need very large data sets with a lot of species and occurrences. Many of these bivalves and gastropod species are still alive, so a lot of the data we needed to do this work can come from what we know about living bivalve and gastropod physiology.”
“The reason we picked the Western Atlantic as a study area is because we have excellent large datasets recording distribution of both fossil and living mollusks from this region. I used a lot of fossil material from collections around the U.S.”
“We found a difference for mollusk species that have gone extinct over the past 5 million years and ones that are still around today,” he said.
“Those that have gone extinct tend to have higher metabolic rates than those that are still living. Those that have lower energy maintenance requirements seem more likely to survive than those organisms with higher metabolic rates.”
The scientists found that a higher metabolic rate was a better indicator of extinction probability, especially when the species were confined to a smaller habitat, and less so when a species was spread over a wide geographic area of the ocean.
“We find the broadly distributed species don’t show the same relationship between extinction and metabolic rate as species with a narrow distribution,” Dr. Strotz said.
“Range size is an important component of extinction likelihood, and narrowly distributed species seem far more likely to go extinct. If you’re narrowly distributed and have a high metabolic rate, your probability of extinction is very high at that point.”
The team also found that cumulative metabolic rates for communities of species remained stable, even as individual species appear and disappear within the community.
“We find if you look at overall communities, and all the species that make up those communities, the average metabolic rate for the community tends to remain unchanged over time,” Dr. Strotz said.
“There seems to be stasis in communities at the energetic level. In terms of energy uptake, new species develop — or the abundance of those still around increases — to take up the slack, as other species go extinct.”
“This was a surprise, as you’d expect the community level metabolic rate to change as time goes by. Instead, the mean energy uptake remains the same over millions of years for these bivalves and gastropods, despite numerous extinctions.”
The research is published in the journal Proceedings of the Royal Society B.
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Luke C. Strotz et al. Metabolic rates, climate and macroevolution: a case study using Neogene mollusks. Proc. R. Soc. B 285 (1885); doi: 10.1098/rspb.2018.1292
