Sexually antagonistic selection for tolerance to ocean acidification

Louisiana State University, Baton Rouge LA

Investigators

Abstract

Males and females often respond differently to the same environmental challenge. Such differences can hurt chances for population survival by reducing the numbers of one sex but they may enhance population resilience by favoring different genetic variants in each sex, elevating overall genetic variation and the population's capacity to adapt. Ocean waters are becoming more acidic, making it harder for corals to build the tropical reefs that harbor enormous diversity and sustain island economies. This research will test whether the response of a coral to ocean acidification varies between sexes in ways that enhance the coral's ability to cope with acidification. The work will center on a coral species living in the Gulf of California, where a natural gradient in ocean acidity allows comparisons of populations under different levels of stress. Growth rates for this coral in acidic regions can be half those found elsewhere and are especially low for females. The proposed research will compare patterns of how genes are turned off and on between sexes and between regions with different acidity, identify genes tied to growth rates in each sex, and use artificial intelligence to distinguish the skeletons of male and female colonies. Graduate students from the US and Mexico will work together on the project and a new undergraduate teaching lab will take part in the artificial intelligence work. Results will facilitate study of sex-specific traits and suggest whether corals with separate sexes are better prepared to respond to a changing ocean than their hermaphroditic kin. The central hypothesis of the work postulates that the genomic response to ocean acidification in the coral, Porites panamensis, varies between sexes and between populations, with sex-specific genetic adaptations enhancing the coral's ability to cope with acidification, thereby influencing the sex ratio and population viability over time. The first objective is to identify candidate sexual conflict genes that are up-regulated under acidic conditions and show sex-biased expression. The second objective will scan male and female genomes for sex-specific divergent outliers and test whether levels of variability close to candidate sexual conflict loci are enhanced relative to other regions of the genome. The third objective aims to identify sex-specific transcripts and genome regions, allowing for non-histological measurement of the sex ratio. Machine learning will also be used to distinguish male and female colonies using skeletal images. Together, the results will help determine whether sex-specific differences in coping with acidification, in an organism with little obvious sexual dimorphism, contribute to adaptive genetic variation. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.