Heritability of CO2 Tolerance in a Coral Reef Fish

Chair: Philip Munday

Megan J. Welch (1,2)* and Philip L. Munday (2)

1 College of Marine and Environmental Sciences, James Cook University, Townsville, Queensland 4811, Australia
2 ARC Centre of Excellence for Coral Reef Studies, James Cook University, Townsville, Queensland 4811, Australia

Background
Projected future CO2 levels cause severe behavioural impairment in reef fishes. Populations will need to adapt to these changed environmental conditions to persist. In order to evolve through natural selection, a trait must exhibit heritable phenotypic variation. We tested for individual variation in behavioural tolerance to elevated CO2 in the spiny damselfish, Acanthochromis polyacanthus, and then used parent-offspring correlations to assess the heritability of this variation in both field and laboratory populations. This is one of the first studies to test for to adaptive potential of fishes to ocean acidification.

Methods
Adult pairs of A. polyacanthus and their offspring were collected from the Lizard Island region and their tolerance to elevated CO2 was tested by comparing their response to chemical alarm cue (CAC) after four days exposure to high CO2. Parent-offspring correlations were then performed. In the laboratory, breeding pairs of A. polyacanthus were formed based on their behavioural tolerance to high CO2: 1) tolerant male–tolerant female, 2) tolerant male–non-tolerant female, 3) non-tolerant male–tolerant female, and 4) non-tolerant male–non-tolerant female. Offspring from these breeding pairs were split at hatching into control and elevated CO2 treatments and reared for six weeks. Offspring response to CAC was measured at six-weeks and compared to their parents and siblings.

Findings
Both field and laboratory populations exhibited a close correlation between offspring and their fathers for tolerance to acute-CO2 treatments, indicating strong heritability in behavioural tolerance to high CO2. Full and half-sibling analysis provided further insight to heritability of CO2 tolerance.

Conclusions
This study uniquely demonstrates heritability in behavioural tolerance to projected future CO2 levels in both laboratory and wild populations. Our quantitative genetics approach offers a positive outlook to adaptive potential of reef fishes to ocean acidification.