Global climate change is having devastating effects on the world’s coral reefs, with declines predicted to escalate sharply in the near future. Severe socio-economic impacts accompany reef degradation, including the loss of food security, coastal stability and tourism income for many of the world’s most vulnerable people. The newly-independent Indo-Pacific nation of Timor-Leste hosts one of the most diverse coral assemblage on Earth, with upwards of 500 coral species potentially inhabiting its reefs. Poorly equipped to carry out even basic assessments of reef diversity and health, the government of Timor-Leste is looking to to attract international researchers, providing a unique opportunity to advance our knowledge about coral diversity, ecology and evolution. We know that many coral species undergo hybridization; however little is known of their symbiotic algae, whose microscopic size and elusive life-cycle make them notoriously difficult to study. Direct evidence of sexual reproduction continues to evade researchers, but DNA evidence attests to its infrequent occurrence. If we can show that sexual reproduction occurs between members of different algal lineages, this would constitute a very important milestone for understanding how they evolve and how we might expedite their adaptation if and when the need arises. This project uses high-throughput DNA sequencing and new bioinformatic methods to explore the diversity of symbiotic algae in Timor Leste, and establish whether hybridization events have shaped the evolutionary history of this lineage.