AsianScientist (Oct. 7, 2016) – Rising temperatures turn up the heat for tiny crustaceans, according to a study that shows how mating behavior changes in response to the warmer waters and more acidic oceans brought about by climate change. It was published in Scientific Reports.
“Climate change most usually comes with predictions of severe negative impacts on population sizes, if not extinctions,” said Dr. Pablo Munguia, an ecologist and evolutionary biologist at the University of Adelaide Environment Institute. “In general, booming populations are not predicted.”
Munguia and PhD student Ms. Katherine Heldt studied the herbivorous amphipod, Cymadusa pemptos, in large tanks under the elevated temperature and carbon dioxide levels (CO2) predicted for 100 years from now. Like other marine amphipods, C. pemptos males have larger claws than females, which they use as a display to attract mates or as a weapon to fend off other males. The study found that the population of shrimp-like crustaceans increased twenty-fold under predicted warmer waters and high CO2.
“It got even more interesting, however, when we dug deeper and found that males were much larger in size than in previous generations under cooler waters and lower CO2, and their bigger claws were disproportionately larger still. Females stayed the same size,” said Munguia.
On top of that, where there had been variation in large claw size throughout the population—suddenly all the males had large claws; this happened within a few generations, according to Munguia. The researchers also discovered that sexual selection for this attractiveness trait could mean that every male was equally attractive to females, resulting in very large numbers of females—almost 80 percent—becoming pregnant, causing a massive population explosion.
Furthermore, because the future climate change conditions also promoted increased growth of the marine algae which amphipods eat, constraints on competition for food were removed, allowing males to support their energy-demanding bigger claws and enabling the population to grow.
“We’ve also shown how mating systems may potentially change. If all males are equals in claw size, then perhaps claws will no longer become a key trait. Our research shows how we can start remapping ideas on how mating systems may become modified under future climate,” said Munguia.
The article can be found at: Heldt et al. (2016) Future Climate Stimulates Population Out-breaks by Relaxing Constraints on Reproduction.
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Source: University of Adelaide; Photo: Katherine Heldt.
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