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Abstract Detail


Sosa, Karla [1].

Ferns beyond binaries: Patterns in spores, reproductive mode, and range in the xeric-adapted Australasian species Cheilanthes distans (Pteridaceae).

Biologists have aimed to describe nature into discrete categories: sexual vs. asexual, diploid vs. triploid vs. tetraploid. But was we take closer looks at nature, we find that discrete categories collapse interesting variation exhibited by organisms. In our work, we focus on Cheilanthes distans, a broadly distributed species scattered over much of Australia and extending to Aotearoa-New Zealand, New Caledonia, and other small Pacific islands. Previous work on the species had revealed only apomictic populations (triploids and tetraploids) with 16 spores per sporangium. By counting spore number per sporangium, we located six specimens with 32 spores per sporangium that we hypothesize represent the sexual diploid progenitor of the apomictic polyploids. These presumed sexual diploids occupy a narrow geographic range near the central coast of Queensland. The prevalence of this particular pattern of geographical parthenogenesis in xeric-adapted ferns suggests that, in the face of limited water availability, the benefits of apomixis outweigh the disadvantages, at least in the short term. Our survey, however, also found near continuous variation of spore size-despite our assumption that spore size would cluster by ploidy. We test whether spore size is correlated with range size, and characterise the ploidy of some specimens. We also observed recurring patterns of certain forms of irregular spores. We characterise the variation of these irregular spores and hypothesise that the dynamics that may be leading to their formation are stages along on the path to obligate apomixis in xeric environments (as per Grusz et al. 2021). Thus the ferns are not either sexual or asexual, but often somewhere in between.

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1 - Biological Sciences, PO BOX 90338, Durham, NC, 27708, United States

range size
natural variation

Presentation Type: Oral Paper
Location: Virtual/Virtual
Date: Wednesday, July 21st, 2021
Time: 3:45 PM(EDT)
Number: BIOGIII004
Abstract ID:1016
Candidate for Awards:None

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