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

Abstract

Sex is a crucial process that has molecular, genetic, cellular, organismal, and population‐level consequences for eukaryotic evolution. Eukaryotic life cycles are composed of alternating haploid and diploid phases but are constrained by the need to accommodate the phenotypes of these different phases. Critical gaps in our understanding of evolutionary drivers of the diversity in algae life cycles include how selection acts to stabilize and change features of the life cycle. Moreover, most eukaryotes are partially clonal, engaging in both sexual and asexual reproduction. Yet, our understanding of the variation in their reproductive systems is largely based on sexual reproduction in animals or angiosperms. The relative balance of sexual versus asexual reproduction not only controls but also is in turn controlled by standing genetic variability, thereby shaping evolutionary trajectories. Thus, we must quantitatively assess the consequences of the variation in life cycles on reproductive systems. Algae are a polyphyletic group spread across many of the major eukaryotic lineages, providing powerful models by which to resolve this knowledge gap. There is, however, an alarming lack of data about the population genetics of most algae and, therefore, the relative frequency of sexual versus asexual processes. For many algae, the occurrence of sexual reproduction is unknown, observations have been lost in overlooked papers, or data on population genetics do not yet exist. This greatly restricts our ability to forecast the consequences of climate change on algal populations inhabiting terrestrial, aquatic, and marine ecosystems. This perspective summarizes our extant knowledge and provides some future directions to pursue broadly across micro‐ and macroalgal species.

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

“…Outcrossing should favor the diploid life cycle while inbreeding and asexual reproduction should favor prolonged haploid phases in the life cycle (Otto & Marks, 1996). Yet, there were too few data to test this hypothesis and this has not improved substantially in the past ∼30 years (see as an example, Krueger-Hadfield et al, 2021; Krueger-Hadfield, 2024).…”

Single-cell transcriptomics highlights sexual cues among reproductive life stages of uncultivated Acantharia (Radiolaria)

“…Perpetuation by reproduction is a common and essential feature of all living beings on Earth (Fusco and Minelli, 2019). Among prokaryotes, binary fission is the dominant mode of reproduction, while eukaryotic microorganisms (protists) can present diverse sexual cycle strategies during their reproduction (Rizos et al, 2024 in press; Krueger-Hadfield, 2024). Up to now, the description of protist asexual (i.e., replicative) and sexual (i.e., recombinative) processes remain fairly limited and incomplete (Margulis and Sagan, 1986; Lahr et al, 2011).…”