Genetic Diversity in the Homosporous Fern Ophioglossum vulgatum (Ophioglossaceae) from South Korea: Inference of Mating System and Population History

Abstract

It is generally believed that the members of Ophioglossaceae have subterranean, potentially bisexual gametophytes, which favor intragametophytic selfing. In Ophioglossaceae, previous allozyme studies revealed substantial inbreeding within Botrychium species and Mankyua chejuense. However, little is known about the mating system in species of the genus Ophioglossum. Molecular marker analyses can provide insights into the relative occurrence of selfing versus cross-fertilization in the species of Ophioglossum. We investigated allozyme variation in 8 Korean populations of the homosporous fern Ophioglossum vulgatum to infer its mating system and to get some insight into the population-establishment history in South Korea. We detected homozygous genotypes for alternative alleles at several loci, which suggest the occurrence of intragametophytic self-fertilization. Populations harbor low within-population variation (% P = 7.2, A = 1.08, and H (e) = 0.026) and a high among-population differentiation (F (ST) = 0.733). This, together with the finding that alternative alleles were fixed at several loci, suggests that the number and size of populations of O. vulgatum might have been severely reduced during the last glaciation (i.e., due to its in situ persistence in small, isolated refugia). The combined effects of severe random genetic drift and high rates of intragametophytic selfing are likely responsible for the genetic structure displayed by this homosporous fern. Its low levels of genetic diversity in South Korea justify the implementation of some conservation measures to ensure its long-term preservation.

Was Jeju Island a glacial refugium for East Asian warm‐temperate plants? Insights from the homosporous fern Selliguea hastata (Polypodiaceae)

“…The current genetic makeup of the studied populations of S. hastata suggests that mainland Korea populations were established by postglacial immigration from a single refugium, likely located either in the geographically proximate Jeju Island or in southern Japan (e.g., JC‐5), or perhaps in both. Our results may thus help to confirm the significance of Jeju Island from a biogeographical point of view; in addition to its putative role as a refugium for arctic–alpine, boreal, and temperate plants (Chung et al, 2012b, 2013c, d; Dolezal et al, 2012), the island would also harbored important populations of subtropical plants during the cold phases of the Pleistocene, as suggested by the present study. The location of Jeju Island (within the East Asia subtropical climate), together with its wide altitudinal gradient (from sea level to 1950 m a.s.l.)…”

A well-sampled phylogenetic analysis of the polystichoid ferns (Dryopteridaceae) suggests a complex biogeographical history involving both boreotropical migrations and recent transoceanic dispersals

“…They are minute, produced in a large quantity, and resistant to dryness and UV radiations (Gradstein and van Zanten, 1999;Peck et al, 1990;Wolf et al, 2001). Furthermore, for many fern species, an isolated gametophyte is able to produce sporophytes through the intragametophytic selfing (Chung et al, 2013;Klekowski, 1972;Soltis and Soltis, 1992). Consequently, fern biogeography is often viewed as driven by Long-Distance Dispersal (hereafter LDD) http://dx.doi.org/10.1016/j.ympev.2016.02.018 1055-7903/Ó 2016 Elsevier Inc. All rights reserved.…”

Genetic analysis of the threatened American hart's-tongue fern (Asplenium scolopendrium var. americanum [Fernald] Kartesz and Gandhi): Insights into its mating system and implications for conservation

“…The low levels of genetic diversity (h ¼ 0.023; PPL ¼ 6) and high rate of occurrence of individuals with the same genotypes in GC imply lower effective population size (i.e., the potential number of individuals that undergo cross-fertilization), and the same condition applies to all the other genetically depauperate populations of AHTF. Although several approaches have been used in determining the effective population size in various species, the result is that it is always smaller than census population size (Esselman et al, 1999;Charlesworth, 2009;Chung et al, 2012). Therefore, despite the large census population size of GC, it still requires conservation and management intervention similar to the populations with small census sizes because of lower effective population size.…”

“…In comparison, no population-specific locus was observed for NY in spite of their relatively higher genetic diversity. In addition to the slow growth rate of AHTF, the absence of populationspecific loci may be due to exposure to generally similar environmental conditions and relatively recent origins of the populations (Ranker, 1994;Schneller, 1996;Chung et al, 2012). Therefore, genetic variation within and among the populations in NY appear to be mainly due to DNA-fragment frequency differences due to sexual reproduction and/or mutations rather than fixation of locally common loci.…”

“…The lack of isolation-by-distance pattern may be due to the random genetic drift that operated in these populations coupled with minimal spore exchange (Soltis and Soltis, 1990;Chung et al, 2012). There is also no significant correlation between levels of genetic diversity and census population size between and within regions, particularly since the two populations with the largest census sizes (GC and SB) have the most contrasting levels of genetic diversity (Table 4).…”