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Contributed Talk

Session: : Restoration Ecology 6

COS 137-6 - Unintentional artificial selection during ex-situ breeding of corals

Tuesday, August 8, 2023
4:45 PM – 5:00 PM PDT
Location: E145
Abstract: Historically, the shallow reefs of the Caribbean were dominated by large stands of branching Acropora palmata. However, A. palmata has declined >80% due to disease and human impacts and is listed as critically endangered. Colpophyllia natans is a brain coral that is comparatively poorly studied and has not experienced severe population losses but is in decline due to stony coral tissue loss disease. Reef restoration is predominantly facilitated through the outplanting of fragmented corals, but sexual propagation of coral is growing in prevalence. Sexual propagation allows for the shuffling of genetic material and maintains the adaptive potential of restored populations. In corals, sexual propagation is typically performed in ex-situ cultures using multi-parent crosses where it is assumed that crosses result in equal parentage. Given the potential for rapid artificial selection to occur in ex-situ settings, it is crucial for us to understand what selective pressures we may be introducing into restoration efforts. Here, we examine the uneven losses of parental contribution in crosses of A. palmata and C. natans in both ex-situ and in-situ cultures using Pool-Seq of larvae at different developmental stages. Four parents per species were crossed in batch during each species’ respective spawning period in Curaçao. Larvae were sampled in bulk at the prawn chip embryo, competent larvae, pre-settlement larvae, and post-settlement larvae life stages in ex-situ lab cultures and in-situ ocean net-pens. DNAs from larvae at each life stage were extracted individually and pooled in equimolar proportions, as well extracted in bulk. Whole genome sequencing of pools, bulk extractions, and parental sperm was performed to monitor shifts in parental alleles. Over the two-week experiment, we observed large shifts in parental contribution to surviving offspring. Additionally, in bulk extracted A. palmata larvae, we observed allele frequency shifts that suggest that some parental combinations generate few, rapidly growing offspring, while others produce many, slower growing offspring. Together, these results suggest that unintentional artificial selection can rapidly take place in ex-situ settings, despite the greatest of care. Further refinement of standard culture methods must take place to ensure that ex-situ sexual propagation resembles natural processes such that we do not unintentionally proliferate maladaptive traits into restored populations.