Consistent differences in fitness traits across multiple generations of Olympia oysters

Abstract

Adaptive evolution and plasticity are two mechanisms that facilitate phenotypic differences between populations living in different environments. Understanding which mechanism underlies variation in fitness-related traits is a crucial step in designing conservation and restoration management strategies for taxa at risk from anthropogenic stressors. Olympia oysters (Ostrea lurida) have received considerable attention with regard to restoration, however there is limited information on adaptive population structure. Using oysters raised under common conditions for up to two generations (F1s and F2s), we tested for evidence of divergence in reproduction, larval growth, and juvenile growth among three populations in Puget Sound, Washington. We found that the population with the fastest growth rate also exhibited delayed and reduced reproductive activity, indicating a potential adaptive trade-off. Our results corroborate and extend upon a previous reciprocal transplant study on F1 oysters from the same populations, indicating that variation in growth rate and differences in reproductive timing are consistent across both natural and laboratory environments and have a strongly heritable component that cannot be entirely attributed to plasticity.

Carryover effects of temperature and pCO2 across multiple Olympia oyster populations

“…, Silliman et al. , Bible et al. ), the Olympia oyster may be more capable than other marine bivalve species to withstand and adapt to unprecedented ocean change.…”

“…These populations are considered phenotypically distinct subpopulations (Heare et al 2017, White et al 2017. The fourth cohort (O-2, 21.9 AE 3.3 mm) was second-generation, hatchery-produced in 2015 from the aforementioned Oyster Bay F1 cohort, from a single larval release pulse and thus likely one family (Silliman et al 2018). The O-2 cohort was included to examine whether reproductive and offspring traits were consistent across generations of a population, with the O-2 cohort being closely related to each other (siblings) and 2 yrs younger than the other cohorts.…”

“…, Silliman et al. ), which were hatchery‐reared in common conditions to adulthood, to account for intraspecific variation while controlling for within‐generation carryover effects (Hettinger et al. , ).…”

“…Furthermore, testing genetically diverse organisms could reveal cryptic genetic variation, alleles that confer stress resilience only under certain settings (Paaby and Rockman 2014, Bitter et al 2019), which has implications for how wild populations are restored. Therefore, we tested three phenotypically distinct Puget Sound populations (Heare et al 2017, Silliman et al 2018, which were hatchery-reared in common conditions to adulthood, to account for intraspecific variation while controlling for within-generation carryover effects (Hettinger et al 2012(Hettinger et al , 2013.…”

Population structure, genetic connectivity, and adaptation in the Olympia oyster (Ostrea lurida) along the west coast of North America

“…The weak population structure within Puget Sound and the overall low genetic diversity in northern sites are likely due to recent genetic bottlenecks and range expansion after the last glacial maximum, which reached just north of Willapa Bay, WA (49°N latitude), until 12–13 kya (Dyke & Prest, ). Despite such low genetic differentiation, experimental assessments of local adaptation for populations within Puget Sound have detected heritable differences in fitness traits such as reproductive timing, growth rate, and gene expression in response to stress (Heare, Blake, Davis, Vadopalas, & Roberts, ; Heare, White, Vadopalas, & Roberts, ; Silliman, Bowyer, & Roberts, ). These results, coupled with experimental evidence for local adaptation to salinity among Northern California populations (Bible & Sanford, ), suggest that adaptive divergence in this species can occur in the face of high gene flow.…”