Hybridisation is a process where eggs and sperm from two different species cross-fertilise to produce viable young.
In coral, this process occasionally occurs in nature. It increases genetic diversity and creates novel genetic combinations that may be beneficial for adaptation and confer resilience to changing climate conditions.
We can increase the rate of natural hybridisation by crossing the eggs and sperm of different species in the laboratory.
At AIMS, we have crossed the eggs and sperm of different pairs of species and trialled the resulting hybrids under stressful conditions in the National Sea Simulator (SeaSim) and in the ocean. Our early results are promising.
Some hybrids grow and survive better than purebreds under today’s and predicted future climate conditions. We also have a population of hybrid corals successfully growing in the ocean.
During the upcoming spawning season, we will be generating hybrids for further testing that will hopefully provide us with critical insights as to whether interspecific hybridisation might be a useful tool for producing resilient material for reef restoration initiatives.
We are also monitoring hybrids that were born in the SeaSim in 2015 through crossing Acropora loripes eggs with Acropora tenuis sperm.
From dissections we have conducted on a small number of branches from these hybrids,it is clear they are capable of producing eggs. This is significant as hybrids can sometimes be infertile.
If coral hybrids are fertile, then they may be able to propagate on reefs, generating offspring that contain more novel genetic combinations and further assisting reef restoration.
Sometimes, the enhanced performance seen in first generation hybrids is lost in the second generation due to mismatches between the genomes of the original parental species. It is important to test whether second generation coral hybrids show enhanced performance compared with their grandparents.
If multiple hybrids spawn during the upcoming season, we will collect their eggs and sperm and try crossing them to generate a second generation of hybrids.
We will also try to cross the first-generation hybrids with purebred A. loripes and A. tenuis corals. If viable, next-generation coral larvae result from these crosses, they will be settled and grown for further study.