CLONALITY AND POLYPLOIDY CONTRIBUTE TO THE SPREAD OFAVRAINVILLEA LACERATA(BRYOPSIDALES, CHLOROPHYTA) IN HAWAIʻI

Abstract

The relative rates of sexual versus asexual reproduction influence the partitioning of genetic diversity within and among populations. During range expansions, uniparental reproduction often facilitates colonization and establishment. The arrival of the green alga Avrainvillea lacerata has caused shifts in habitat structure and community assemblages since its discovery in 1981 offshore of west Oahu, Hawaii. Field observations suggest this species is spreading via vegetative reproduction. To characterize the reproductive system of A. lacerata in Hawaii, we developed seven microsatellite loci and genotyped 321 blades collected between 2018 and 2023 from two intertidal sites at Maunalua Bay and 'Ewa Beach. We found one to four alleles at multiple loci, suggesting A. lacerata is tetraploid. Each site was characterized by high genotypic richness (R > 0.8). However, clonal rates were also high at both sites, suggesting vegetative spread of A. lacerata plays a significant role. The importance of clonal reproduction for the persistence of A. lacerata in Hawaii is consistent with the ecological data collected for this species, and observations of other abundant macroalgal invaders in Hawaii and other regions of the world. These data demonstrate the necessity for implementing appropriate population genetic methods and provide insights into the biology of this alga that will contribute to future studies on effective management strategies incorporating its reproductive system. This study represents one of the few investigating green algal population genetic patterns and contributes to our understanding of algal reproductive system evolution.

Let's talk about sex: Why reproductive systems matter for understanding algae

“…Vegetative reproduction through fragmentation or patch expansion of holdfasts is known in many Ulvophytes, including Caulerpa taxifolia (Phillips, 2009), Cladophoropsis membrancacea (van der Strate et al, 2002), and, more recently, Avrainvillea lacerata (Thornton et al, 2024). Many taxa are also capable of producing gametes or spores through apomixis, which has been shown using data on population genetics in Ulva sp.…”