Biology subjects

Lemer, S.

Publications and source records attributed to Lemer, S..

4 recordsLinked to original sources

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

Photosymbiosis Shaped Animal Genome Architecture and Gene Evolution as Revealed in Giant Clams

Symbioses are major drivers of organismal diversification and phenotypic innovation. However, how long-term symbioses shape whole genome evolution in metazoans is still underexplored. Here, we used a giant clam (Tridacna maxima) genome to demonstrate how symbiosis has left complex signatures in an animals genome. Giant clams thrive in oligotrophic waters by forming a remarkable association with photosymbiotic dinoflagellate algae. Genome-based demographic inferences uncovered a tight correlation between T. maxima global population change and major paleoclimate and habitat shifts, highlighting how abiotic and biotic factors dictate T. maxima microevolution. Comparative analyses revealed unique symbiosis-driven genomic features, including expansion and contraction of immunity-related gene families and a large proportion of lineage-specific genes. Strikingly, about 70% of the genome is composed of repetitive elements, especially transposable elements, most likely resulting from a symbiosis-adapted immune system. This work greatly enhances our understanding of genomic drivers of symbiosis that underlie metazoan evolution and diversification.

genomics↗

bioRxiv2024

Genomic data reveals habitat partitioning in massive Porites on Guam, Micronesia

Corals in marginal reef habitats generally exhibit less bleaching and associated mortality compared to nearby corals in more pristine reef environments. It is unclear, however, if these differences are due to environmental differences, including turbidity, or genomic differences between the coral hosts in these different environments. One particularly interesting case is in the coral genus Porites, which contains numerous morphologically similar massive Porites species inhabiting a wide range of reef habitats, from turbid river deltas and stagnant back reefs to high-energy fore reefs. Here, we generate ddRAD data for 172 Porites corals from river delta and adjacent fore reef populations on Guam to assess the extent of genetic differentiation among massive Porites corals in these two contrasting environments and throughout the island. Phylogenetic and population genomic analyses identify seven different clades of massive Porites, with the two largest clades predominantly inhabiting either river deltas and fore reefs, respectively. No population structure was detected in the two largest clades, and Cladocopium was the dominant symbiont genus in all clades and environments. The perceived bleaching resilience of corals in marginal reef environments may therefore be attributed to interspecific differences between morphologically similar species, in addition to potentially mediating environmental differences. Marginal reef environments may therefore not provide a suitable refuge for many reef corals in a heating world, but instead host additional cryptic coral diversity.

evolutionary biology↗

bioRxiv2023

Synergistic genomic mechanisms of adaptation to ocean acidification in a coral holobiont

Ocean acidification, caused by anthropogenic CO2 emissions, is predicted to have major consequences for reef-building corals, jeopardizing the scaffolding of the most biodiverse marine habitats. However, whether corals can adapt to ocean acidification and how remains unclear. We addressed these questions by re-examining transcriptome and genome data of Acropora millepora coral holobionts from volcanic CO2 seeps with end-of-century pH levels. We show that adaptation to ocean acidification is a wholistic process involving the three main compartments of the coral holobiont. We identified 441 coral host candidate adaptive genes involved in calcification, response to acidification, and symbiosis; population genetic differentiation in dinoflagellate photosymbionts; and consistent transcriptional microbiome activity despite microbial community shifts. Coral holobionts from natural analogues to future ocean conditions harbor beneficial genetic variants with far-reaching rapid adaptation potential. In the face of climate change, these populations require immediate conservation strategies as they could become key to coral reef survival.

evolutionary biology↗