Der Nutzen von assistierter Evolution in einer bedrohten Korallenart für die Förderung widerstandsfähiger Riffökosysteme im Angesicht des Klimawandels
Evolution, Anthropologie
Zusammenfassung der Projektergebnisse
The objective of this project was to carry out selective breeding in a threatened coral species, based on thermotolerance and disease resistance, for assessing trait heritabilities and the utility of this approach as a coral reef restoration intervention. The capacity of coral reef species/populations to effectively respond to rapid climate change is of major concern. The rapid widespread degradation of coral reef ecosystems has led to the realization that coral reef populations will not recover on their own; an estimated 70-90% of the world's corals could disappear by 2050 if carbon emissions continue unabated and water quality does not improve. Increased investments in developing novel interventions and innovative strategies have led to new research fields like assisted evolution of corals for building coral reef resilience. There are different approaches to assisted evolution, based on genetic, reproductive and physiological interventions, and one such method ─selective breeding─ represents a viable strategy for increasing adaptive genetic variation within offspring populations. However, reef corals are long-lived, slow-growing organisms that have limited opportunities to sexually reproduce, usually only once a year. Given the degraded state of many populations and environments, sexual cycles are failing for some species, especially in the western Atlantic/Caribbean. This means humans will need to step in to help carry out the sexual cycle so that the benefits of sexual reproduction for maintaining genetic diversity and promoting more rapid adaptation under changing environmental conditions can be realized. Since the first step of selective breeding is to cross sexually mature colonies, which can prove difficult to obtain if corals are stressed, unhealthy, too small, overly fragmented or diseased, alternative strategies will need to be devised, as I have done here using in-situ spawning nurseries, for example. Spawning nurseries can provide easier and more reliable access to sexually mature colonies and nursery conditions may support faster growth, reducing the time needed to reach sexual maturity since it is size-dependent. Additionally, with the potential for worsening spawning asynchronicity to preclude successful breeding of corals, ex-situ spawning systems may need to be established to induce synchronized spawning in the lab. Finally, coral sexual propagation, whether for research or restoration, remains an area of active investigation where each step in the sexual cycle, including spawning, fertilization, larval settlement and sexual recruit rearing, needs to be optimized individually for every species. Despite these challenges and a category 5 hurricane greatly affecting the feasibility and scope of my proposed project, during my DFG fellowship I established the first in-situ spawning nurseries at the host institution and carried out, for the first time at the host institution, the entire sexual cycle in the lab to produce genetically-diverse offspring using the host institution’s coral stocks. Two-parent crosses were carried out as would be done during selective breeding, and I achieved high fertilization, settlement and post-settlement survival rates. While not enough different genotypes spawned on the same night to support selective breeding for evaluating the heritability of targeted traits, my work confirms that corals can be spawned and outplanted in less than 2 years and that once each stage of the sexual cycle is mastered in the lab, the entire process can be manipulated to test specific hypotheses regarding the utility of selective breeding for coral reef restoration. Selective breeding based on thermotolerance has recently been achieved, demonstrating it can be used as an intervention to increase adaptive genetic variation within offspring populations, but other traits, e.g. disease resistance, remain untested in this context. If disease resistance has a heritable component, it may be possible to incorporate multiple traits through selective breeding to generate offspring resilient to both warming seas and disease and maximize the adaptive potential of restored coral populations using modified, resilient stocks. NIGHTSEA (September 2019): https://www.nightsea.com/articles/coral-restoration-mote-marine-laboratory/ Keys Weekly online magazine (October 2019) https://keysweekly.com/42/coral-sex/ Mote Magazine (December 2019): https://mote.org/news/article/coral-spawning Sarasota Scene Magazine (December 2019): http://www.scenesarasota.com/magazine/motes-mission-to-save-coral-reefs/ Podcast (January 2020): https://mote.org/podcasts/item/coral-matchmaker-shares-the-science-of-reef-romance MANG non-profit mangrove restoration company (March 2020): https://www.facebook.com/manggear/videos/236395280866428/
