Abstract Detail


Sosa, Karla [1], Windham, Michael D. [2].

Geographic patterns in ploidy and reproductive mode in the xeric-adapted Australasian species Cheilanthes distans (Pteridaceae).

Are there certain characteristics that facilitate establishment of populations in novel environments? Regarding ferns, a turn to asexuality (apomixis) could be beneficial in seasonally xeric habitats, allowing them to produce new sporophytes in the absence of the film of water needed for sexual reproduction. However, there are negative long-term genetic consequences to asexuality, such as Muller’s ratchet, that should place limits on the evolutionary success of organisms pursuing this option. In our work, we are focusing on a well-supported clade of Australasian ferns belonging to the genus Cheilanthes (Pteridaceae). Cheilanthes distans is a broadly distributed species, scattered over much of Australia and extending to New Zealand, New Caledonia, and other small Pacific islands. Previous cytogenetic work on the species has revealed only apomictic populations (triploids and tetraploids) with 16 spores per sporangium. For this study, we searched for cryptic sexual diploids of C. distans by determining spore number per sporangium in 279 collections scattered across its known distribution. 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, and appear to favour wetter environments. These observations seem to support the long-standing hypothesis that apomixis in ferns is evolutionarily advantageous in drier habitats. 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.

1 - Biological Sciences, PO BOX 90338, Durham, NC, 27708, United States
2 - Duke University, Biology Department, Box 90338, Durham, NC, 27708, USA


Presentation Type: Oral Paper
Session: PTER1, Pteridology I
Location: Virtual/Virtual
Date: Monday, July 27th, 2020
Time: 10:30 AM
Number: PTER1003
Abstract ID:184
Candidate for Awards:Edgar T. Wherry award

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