Clones on the run: The genomics of a recently expanded partially clonal species

Abstract

This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited.

Genetic structure and diversity of the seagrass Zostera marina along a steep environmental gradient, with implications for genetic monitoring

“…A recent genomic assessment over the entire distribution of eelgrass, in both the Pacific and Atlantic, only detected a small percentage of clonemates (9%; Yu et al, 2023), as well as previous genetic assessments, based on microsatellites, along the Kattegat, Skagerrak and Southern Baltic Sea (Jahnke et al, 2018(Jahnke et al, , 2020Martínez-García et al, 2021). A high incidence of clonality in the Baltic Sea has previously been shown in other species (e.g., macroalgae; Bergström et al, 2003;Johannesson and André, 2006;Pereyra et al, 2023). A potential explanation for the high incidence of clonality in multiple facultative sexual species in the Baltic Sea is that under extreme conditions, environmental factors may be unsuitable for one or several stages of sexual reproduction.…”

“…Indeed, although flowering eelgrass and seed germination have been observed at as low as 5 psu in the Baltic Sea (Boström, 1995;Salo, 2014;Salo et al, 2014), this salinity level might be too low for successful seed ripening or seedling establishment. In such a scenario, clonality might increase survival in these extreme environments (Edgeloe et al, 2022), and be especially competitive during colonization and range expansions into such environments (Rafajlović et al, 2017;Pereyra et al, 2023). Indeed, the Baltic Sea turned marine only recently (∼8,000 years ago) and has been colonized since then by marine species such as eelgrass (Snoeijs-Leijonmalm et al, 2017).…”

“…Moreover, flowering shoots are rarely seen in the northern part of the Baltic Sea (Boström, 1995;Möller and Martin, 2007). Clonality may be advantageous when colonizing a new area and during range expansions (Rafajlović et al, 2017;Pereyra et al, 2023) and might favor survival in extreme environments (Edgeloe et al, 2022), but in terms of conservation a high dominance of clonal reproduction is generally seen as a disadvantage, particularly under global change (Pipithkul et al, 2021). Nevertheless, some ancient clones have persisted for centuries to millennia, and due to their presumed high fitness in the local environment are referred to as all-purpose-genotypes.…”

A somatic genetic clock for clonal species

“…4d), 1 in Estonia (352 years), 2 in Norway (271 and 847 years) and 1 in Finland (1,403 years). All genets >270 years of age were located in higher latitudes (>50° N) in the North Atlantic, indicating that marginal populations were more likely to maintain old genets 4,11,36 and supporting the established geographic parthenogenesis pattern 37 . Although the evolutionary history in the Pacific is much longer than that in the Atlantic 35 , Pacific eelgrass genets were young (<40 years).…”

Precise age estimation in clonal species using a somatic genetic clock

“…Often, the contribution of sexual and clonal reproduction to local population structure varies among species and localities [3][4][5] , resulting in asexual populations of ramets that are nested within the "classical" population of genets 2,6 . Coral, algae, seagrass, or poplar genets, for example, can reach considerable size and therefore age with linear extents of >1 km [7][8][9][10][11] . The apparent persistence and resilience of asexual ramet populations is astonishing in light of the considerable temporal and spatial variation they may experience over their lifetimes despite little genetic variation (but see refs 10,12 ) and raises questions about these species' adaptability in a rapidly changing climate 13 .…”