terHorst, C.P. and M.A. Coffroth. 2022. Individual variation in growth and physiology of
symbionts in response to temperature. Ecology & Evolution 12:e9000. https://doi.org/10.1002/ece3.9000 PDF
Abstract
In many cases, understanding species’ responses to climate change requires understanding
variation among individuals in response to such change. For species with
strong symbiotic relationships, such as many coral reef species, genetic variation
in symbiont responses to temperature may affect the response to increased ocean
temperatures. To assess variation among symbiont genotypes, we examined the population
dynamics and physiological responses of genotypes of Breviolum antillogorgium
in response to increased temperature. We found broad temperature tolerance
across genotypes, with all genotypes showing positive growth at 26, 30, and 32°C.
Genotypes differed in the magnitude of the response of growth rate and carrying
capacity to increasing temperature, suggesting that natural selection could favor different
genotypes at different temperatures. However, the historical temperature at
which genotypes were reared (26 or 30°C) was not a good predictor of contemporary
temperature response. We found increased photosynthetic rates and decreased respiration
rates with increasing contemporary temperature, and differences in physiology
among genotypes, but found no significant differences in the response of these
traits to temperature among genotypes. In species with such broad thermal tolerance,
selection experiments on symbionts outside of the host may not yield results sufficient
for evolutionary rescue from climate change.
K E Y W O R D S
acclimation, adaptation, climate change, coral reefs, genetic variation, symbiosis
