Shainker-Connelly Sarah J, Crowell Roseanna M, Stoeckel Solenn, Vis Morgan L, Krueger-Hadfield Stacy A
Department of Biology, University of Alabama at Birmingham, Birmingham, Alabama, USA.
Department of Environmental and Plant Biology, Ohio University, Athens, Ohio, USA.
J Phycol. 2024 Dec;60(6):1420-1436. doi: 10.1111/jpy.13510. Epub 2024 Oct 28.
Life cycles with a prolonged haploid phase are thought to be correlated with greater rates of selfing and asexual reproduction. In red algae, recent population genetic studies have aimed to test this prediction but have mostly focused on marine species with separate sexes. We characterized the reproductive system of the obligately monoicous (i.e., hermaphroditic) freshwater red alga Batrachospermum gelatinosum and predicted that we would find genetic signatures of uniparental reproduction because of its haploid-diploid life cycle. We sampled 18 sites and genotyped 311 gametophytes with 10 polymorphic microsatellite loci to describe the reproductive system. Genotypic richness was low (<0.5) and pareto β values (describing clonal membership) were <0.7 for most sites. In taxa with separate sexes, these patterns are typically indicative of asexual reproduction. However, the genetic consequences of selfing in monoicous gametophytes are indistinguishable from those caused by asexual processes. Since we sampled gametophytes and have not yet genotyped the chantransia (i.e., the diploid phase), we interpreted low diversity as a signature of intragametophytic selfing. Additionally, to understand the factors that drive selfing, we tested latitude and several other environmental variables, but none was significantly correlated with the genetic variation we observed. Nevertheless, future studies should genotype the chantransia to measure observed heterozygosity among other summary statistics to disentangle the effects of selfing versus asexual reproduction. Together, these data, coupled with further characterization of abiotic factors that influence population genetic patterns, will allow us to test potential drivers of reproductive system evolution.
具有延长单倍体阶段的生命周期被认为与更高的自交率和无性繁殖率相关。在红藻中，最近的群体遗传学研究旨在检验这一预测，但大多集中在具有分开性别的海洋物种上。我们对专性雌雄同体（即雌雄同株）的淡水红藻胶串珠藻的生殖系统进行了特征描述，并预测由于其单倍体 - 二倍体生命周期，我们会发现单亲繁殖的遗传特征。我们在18个地点进行了采样，并使用10个多态微卫星位点对311个配子体进行基因分型，以描述生殖系统。大多数地点的基因型丰富度较低（<0.5），帕累托β值（描述克隆成员关系）<0.7。在具有分开性别的分类群中，这些模式通常表明无性繁殖。然而，雌雄同体配子体自交的遗传后果与无性过程所导致的后果无法区分。由于我们对配子体进行了采样，尚未对钱氏藻阶段（即二倍体阶段）进行基因分型，我们将低多样性解释为配子体内自交的特征。此外，为了了解驱动自交的因素，我们测试了纬度和其他几个环境变量，但没有一个与我们观察到的遗传变异显著相关。尽管如此，未来的研究应该对钱氏藻进行基因分型，以测量观察到的杂合度以及其他汇总统计数据，以区分自交与无性繁殖的影响。总之，这些数据，再加上对影响群体遗传模式的非生物因素的进一步特征描述，将使我们能够测试生殖系统进化的潜在驱动因素。
