Torrado, H. | Search bioRxiv

bioRxiv2024

Evolutionary genomics of two co-occurring congeneric fore reef coral species on Guam (Mariana Islands).

Population structure provides essential information for developing meaningful conservation plans. This is especially important in remote places, such as oceanic islands, where limited population sizes and genetic isolation can make populations more susceptible and self-dependent. In this study, we assess and compare the relatedness, population genetics and molecular ecology of two sympatric Acropora species, A. surculosa sensu Randall & Myers (1983) and A. cf. verweyi Veron & Wallace, 1984 around Guam, using genome-wide sequence data (ddRAD). We further contrast our findings with the results of a recent study on back reef A. cf. pulchra (Brook, 1891) to assess the impact of habitat, colony morphology and phylogenetic relatedness on these basic population genetic characteristics and generate testable hypotheses for future studies. Both target species were found to have small effective population sizes, low levels of genetic diversity, and minimal population structure around Guam. Nonetheless, A. cf. verweyi had significantly higher levels of genetic diversity, some population structure as well as more clones, close relatives and putative loci under selection. Comparisons with A. cf. pulchra indicate a potentially significant impact by habitat on population structure and genetic diversity while colony morphology seems to significantly impact clonality. This study revealed significant differences in the basic population genetic makeup of two sympatric Acropora species on Guam. Our results suggest that colony morphology and habitat/ecology may have a significant impact on the population genetic make-up in reef corals, which could offer valuable insights for future management decisions in the absence of genetic data.

evolutionary biology↗

bioRxiv2024

Population genomics for coral reef restoration - a case study of staghorn corals in Micronesia

Staghorn Acropora corals are ecological keystone species in shallow lagoons and back reef habitats throughout the tropics. Their widespread decline coupled with their amenability for asexual propagation propelled them to the forefront of global coral restoration efforts - albeit frequently without much scientific input. To guide these efforts and as a blueprint for similar projects, we conducted a comprehensive population genomic study of Acropora cf. pulchra, a major restoration target species in the Indo-Pacific. Our results revealed that A. cf. pulchra populations in the Mariana Islands are characterized by large clonal clusters and extremely low levels of genetic diversity. Differentiation among populations followed a significant isolation-by-distance pattern and delineated two distinct metapopulations on Guam. Our investigation identified critical population genetic parameters, necessitating targeted management strategies, and provides actionable guidelines for effective conservation efforts. For management and conservation, two populations emerged as pivotal connectivity hubs with elevated genetic diversity. For restoration, we show that A. cf. pulchra populations demonstrated a suitability for extensive asexual propagation and provide guidelines how to best apply that. To preserve and augment genetic diversity, strategies to mitigate inbreeding are crucial until sexual reproduction can be fully integrated into restoration protocols. Critical sites for restoration include local connectivity hubs, fringing lagoons that connect metapopulations, and back reefs around a particularly isolated population. These findings offer crucial insights into the genetic landscape of a keystone coral species and provide actionable recommendations for coral conservation and restoration. By advocating for the preservation of population connectivity and the promotion of genotypic, genetic, and symbiont diversity in coral restoration, our study serves as a blueprint for leveraging population genomic studies to enhance the efficacy and resilience of restoration projects on remote islands.

evolutionary biology↗