Heritable differences in fitness-related traits among populations of the mustard hill coral, Porites astreoides

Abstract

A population's potential for rapid evolutionary adaptation can be estimated from the amount of genetic variation in fitnessrelated traits. Inshore populations of the mustard hill coral (Porites astreoides) have been shown to be more tolerant to thermal stress than offshore populations, but it is unclear whether this difference is due to long-term physiological acclimatization or genetic adaptation. Here, we evaluated variation in growth rate and survival among 38 families of juvenile recruits of P. astreoides spawned by colonies originating from inshore and offshore locations. Recruits were reared in a common garden for 5 weeks and then subjected to two thermal treatments (28 and 31°C) for 2.5 weeks. The most significant effects were detected during the first 5 weeks, before thermal stress was applied: 27-30% of variance in growth and 94% of variance in recruit survival was attributable to parental effects. Genotyping of eight microsatellite loci indicated that the high early mortality of some of the recruit families was not due to higher inbreeding. Post treatment, parental effects diminished such that only 10-15% of variance in growth rate was explained, which most likely reflects the dissipation of maternal effects. However, offshore-origin recruits still grew significantly less under elevated temperature compared with inshore-origin recruits. These differences observed in naive juvenile corals suggest that population-level variation in fitness in response to different thermal environments has a genetic basis and could represent raw material for natural selection in times of climate change.

Site-specific variation in gene expression from Symbiodinium spp. associated with offshore and inshore Porites astreoides in the lower Florida Keys is lost with bleaching and disease stress

“…If acclimatization were an important means of counteracting bleaching susceptibility, zooxanthellae gene expression patterns would have likely changed in the transplant experiment. Instead, gene expression may be genetically determined by adaptation, as was also proposed for the coral host [15]. The lack of acclimatization demonstrated in gene expression parallels previous research demonstrating a lack of change in zooxanthellae subclade type populations associated with P .…”

“…While chronic moderate stress is commonly experienced by zooxanthellae on reefs in the Florida Keys [16,23], acute stress is a more transient phenomenon poorly described in the literature. Most studies report a response of the coral host and imply that such effects also impact the metabolism of the symbionts [15,61]. To evaluate the influence of acute stress on zooxanthellae gene response we exposed the same coral from Acer24 and Birthday reefs to a high temperature (32°C) stress, and the same high temperature combined with LPS from S .…”

“…However, the role of zooxanthellae in bleaching susceptibility variation in inshore and offshore P . astreoides of the Florida Keys is relatively unknown [15]. …”

Maternal effects and Symbiodinium community composition drive differential patterns in juvenile survival in the coral Acropora tenuis

“…Therefore, larval dispersal may be sufficiently high between Wilkie and Orpheus populations for gene flow to lead to fairly well-mixed populations. A similar study of Porites astreoides also concluded that population origin had little to no impact on juvenile survival [6]. Interestingly, southern GBR juveniles appear to be locally adapted [85], a finding in line with microsatellite data showing that the southern GBR represents a distinct region according to population structure analyses [83].…”

“…In corals, the parental identity of larvae influences up to 47% of settlement success in the spawning coral A. millepora in aquaria [5]. Recent tank experiments with brooding corals found that 94% of the variability in juvenile survivorship and 27–30% of variability in juvenile growth in aquaria were due to familial genotypes [6]. Parental combinations also impact other early life-history traits in corals, such as protein content, affinity to settlement cues, fertilization success and larval heat tolerance [2,4,27].…”