Cross-generational heritability analysis of physiological traits in Porites astreoides across an inshore-offshore gradient in the Lower Florida Keys

Abstract

Estimating the heritable genetic variation in fitness-related traits is key to projecting the adaptive evolution of organisms in response to a changing environment. While heritability studies on reef-building corals to date support adaptive capacity, little is known about the dynamics of trait heritability across life stages in which distinct selective pressures can have long-lasting effects both within and across generations. In this study, we obtained heritability estimates for energetic and thermal stress response traits in adult, larval, and recruit Porites astreoides from two populations in the Lower Florida Keys. To induce bleaching phenotypes among individual families, larvae were exposed to a 4-day thermal stress at 32 °C, whereas adults and recruits received the same treatment for 22 days. Origin-dependent tolerance was observed in two life stages where offshore recruits lost more symbiont cells under heat than inshore recruits compared to their respective controls and heat-treated offshore adults suffered a greater loss in total protein content. Surprisingly, larvae appeared to be largely insensitive to heat regardless of origin. Broad sense heritability (H2) estimates varied greatly among traits and life stages, which may reflect changes in the relative importance of genetic and environmental variation throughout development. Over 50% of the variation in all larval traits, adult symbiont density and chlorophyll a concentration, and recruit protein content can be attributable to genetic factors. The overall moderate to high H2 estimates measured here suggest family-level variation can persist across different life stages and these corals may be equipped with considerable potential to adapt to environmental change.