Interploidy gene flow via a ‘pentaploid bridge’ and ploidy reduction in Cystopteris fragilis fern complex (Cystopteridaceae: Polypodiales)

Ptáček, Jan; Ekrt, Libor; Hornych, Ondřej; Urfus, Tomáš

doi:10.1007/s00497-023-00476-5

Cited by 2 publications

(3 citation statements)

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“…Gametophytes of both ploidy levels proceeded to create sporophytes apogamously (Lin et al, 1992). Recently, pentaploid (5 x ) individuals of the partially apomictic Cystopteris fragilis were found to form reduced (mostly triploid and diploid) as well as unreduced spores, with triploid (3 x ) gametophytes, specifically, producing sporophytes via sexual reproduction (Ptáček et al, 2023). In contrast, Ekrt and Koutecký (2016) discovered individuals of the pentaploid (5 x ) apo‐sex hybrid D .…”

Section: Discussionmentioning

confidence: 99%

“…It is well‐known that these spore‐bearing plants transition between the gametophytic and sporophytic stages using two different mechanisms, sexuality and apomixis (Haufler et al, 2016). Unlike in angiosperms (Krahulcová et al, 2014; Lepší et al, 2019; Doležal et al, 2020), these two strategies rarely manifest together in a single species (Kawakami et al, 2016; Ptáček et al, 2023); the choice is all or nothing, raising an important question of how fern evolution “selects” between these two.…”

Section: Figurementioning

confidence: 99%

“…In parallel with apogamous sporophyte formation, viable diploid sperm may also be created by apomictic ferns. These gametes permit hybridization with nearby archegoniate gametophytes of sexual species, resulting in primary apo‐sex hybrids—hybrids of sexual and apomictic taxa (Hornych et al, 2022; Ptáček et al, 2023).…”

Section: Figurementioning

confidence: 99%

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An adventurous journey toward and away from fern apomixis: Insights from genome size and spore abortion patterns

Ekrt,

Férová,

Koutecký

et al. 2024

American J of Botany

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PremiseApomixis in ferns is relatively common and obligatory. Sterile hybrids may restore fertility via apomixis at a cost of long‐term genetic stagnation. In this study, we outlined apomixis as a possible temporary phase leading to sexuality and analyzed factors relating to transitioning to and away from apomixis, such as unreduced and reduced spore formation in apomict and apo‐sex hybrid ferns.MethodsWe analyzed the genome size of 15 fern species or hybrids (“taxa”) via flow cytometry. The number of reduced and unreduced gametophytes was established as a proxy for viable spore formation of either type. We also calculated the spore abortion ratio (sign of reduced spores) in several taxa, including the apo‐sex hybrid Dryopteris × critica and its 16 apomictically formed offspring.ResultsFour of 15 sampled taxa yielded offspring variable in genome size. Specifically, each variable taxon formed one viable reduced plant among 12–451 sampled gametophytes per taxon. Thus, haploid spore formation in the studied apomicts was very rare but possible. Spore abortion analyses indicated gradually decreasing abortion (haploid spore formation) over time. In Dryopteris × critica, abortion decreased from 93.8% to mean 89.5% in one generation.ConclusionsOur results support apomixis as a transitionary phase toward sexuality. Newly formed apomicts hybridize with sexual relatives and continue to form haploid spores early on. Thus, they may get the genomic content necessary for regular meiosis and restore sexuality. If the missing relative goes extinct, the lineage gets locked into apomixis as may be the case with the Dryopteris affinis complex.

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Section: Discussionmentioning

confidence: 99%