Hidden Diversity in an Antarctic Algal Forest: Metabolomic Profiling Linked to Patterns of Genetic Diversification in the Antarctic Red Alga Plocamium sp.

Abstract

The common Antarctic red alga Plocamium sp. is rich in halogenated monoterpenes with known anticancer and antimicrobial properties and extracts of Plocamium sp. have strong ecological activity in deterring feeding by sympatric herbivores. Plocamium sp. collected near Anvers Island, Antarctica showed a high degree of secondary metabolite diversity between separate individuals. GC/MS results revealed 15 different combinations of metabolites (chemogroups) across individuals, which were apparent at 50% or greater Bray–Curtis similarity and also clearly distinguishable by eye when comparing chromatographic profiles of the secondary metabolomes. Sequencing of the mitochondrial cox1 gene revealed six distinct haplotypes, of which the most common two had been previously reported (now referred to as Haplotypes 1 and 2). With the exception of one individual, three of the chemogroups were only produced by individuals in Haplotype 1. All the other 12 chemogroups were produced by individuals in Haplotype 2, with five of these chemogroups also present in one of the four new, less common haplotypes that only differed from Haplotype 2 by one base pair. The functional relevance of this metabolomic and genetic diversity is unknown, but they could have important ecological and evolutionary ramifications, thus potentially providing a foundation for differential selection.

Marine natural products

“…The functional role of the genetic and metabolic diversity remains to be resolved, but it could explain Natural Product Reports Review chemoecological roles for the metabolites in deterring herbivory or encroachment. 410 6 Sponges…”

Tetrasporophytic bias coupled with heterozygote deficiency in Antarctic Plocamium sp. (Florideophyceae, Rhodophyta)

“…The red macroalga Plocamium sp. is an abundant and widespread species which has been extensively studied near Anvers Island (western Antarctic Peninsula) for its secondary metabolite diversity (Heiser, Shilling, et al, 2023;Shilling et al, 2019Shilling et al, , 2021Young et al, 2013). Shilling et al (2021) described 15 chemogroups-which are signature mixtures of secondary metabolites that differ in relative abundance among chemogroups-in Plocamium sp.…”

Microsatellite locus development in the seaweed Plocamium sp.

“…Winn et al 2011) and sexual vs asexual reproduction (e.g. Vallejo-Marín et al 2010), but studies have been restricted largely to angiosperms or animals, with far fewer investigations in macroalgae (Krueger-Hadfield et al 2021). Plocamium sp., like many macroalgae, has a haploid-diploid life cycle, with free-living diploid tetrasporophytes and free-living haploid gametophytes, which are morphologically indistinguishable unless they are reproductive (Fig.…”

“…It supports among the highest amphipod and gastropod densities and is protected from predation through highly diverse chemical defences (Heiser et al 2020). Haplotypic diversity, based on the mitochondrial cox 1 barcode, showed some evidence of geographical structure as well as correlation with specific chemical defences (Shilling et al 2021). These coarse patterns of genetic diversity are insufficient to understand the processes structuring populations of Plocamium sp.…”