Abstract Detail


Hornych, Ondrej [1], Testo, Weston [2], Sessa, Emily [3], Watkins, James [4], Campany, Courtney [5], Pittermann, Jarmila [6], Ekrt, Libor [7].

Pheromones largely control sex expression in ferns: a meta-analysis of fern mating via antheridiogens.

Homosporous ferns can form unisexual or bisexual gametophytes. Sex expression is affected by many factors, including antheridiogens. Antheridiogens are pheromones released by female or bisexual gametophytes. Nearby asexual gametophytes have the potential to sense antheridiogens and turn precociously male, rather than following the typical protogynous development pathway. The antheridiogen system increases the availability of free-swimming sperm and facilitates outcrossing; this system is also capable of inducing germination of subterranean gametophytes. However, not all fern species produce or respond to antheridiogens. The production of or response to antheridiogens has been tested in many species since the discovery of the pheromone in 1950 and several chemically distinct antheridiogen systems have been described across the leptosporangiate ferns. This study presents a detailed synthesis combining the results of our cultivation experiments with a thorough review of available literature (88 papers). The dataset is based on a list of interactions between antheridiogen-producing and responsive species and their outcome. The effect of dark germination is recorded separately, and species are coded as apomictic or sexual and diploid or polyploid. Our final dataset contains a total of 498 interactions involving 208 species (ca. 2% of global fern diversity) from 26 families of leptosporangiate ferns. About 65% of all recorded species respond to some type of antheridiogen. Two well-established antheridiogen types were confirmed and one to two other types require more study. Data were sufficient to evaluate the capability of antheridiogens to promote germination in darkness for 32 taxa. With three exceptions, the results for dark germination match those of regular antheridium promotion. The percentage of antheridiogen responsive species is not significantly affected by apomixis or polyploidy. The present study is the most comprehensive review of antheridiogen research to date. It is clear that antheridiogens play a key role in fern reproduction. The pheromone has likely evolved multiple times indicating a recurring need for a system promoting outcrossing in gametophyte populations but allowing selfing for single individuals. The dark germination effect is tightly correlated with antheridium promotion, enabling aboveground gametophytes to mine genetic diversity of spore banks below. Despite the indications that polyploid species are more tolerant of selfing, polyploid taxa are not less likely to respond to antheridiogens. Possibly, the benefits of selfing outweigh any potential negatives, or the pheromone sensitivity is inherited and hard to remove.

1 - University of South Bohemia, Department of Botany, Branisovska 1760, Ceske Budejovice, CZ-370 05, Czechia
2 - University Of Florida, 313 NW 2nd St, Gainesville, FL, 32601, United States
3 - University Of Florida, Biology, Box 118525, 521A Bartram Hall, Gainesville, FL, 32611, United States
4 - Colgate University, Department Of Biology, 13 Oak Drive, Hamilton, NY, 13346, United States
5 - Shepherd University , Department of Biology, 301 N King St, Shepherdstown, WV, 25443, USA
6 - University Of California, Ecology And Evolutionary Biology, 1156 High Street, Santa Cruz, CA, 95064, United States
7 - University Of South Bohemia, Faculty Of Science, Department Of Botany, Branisovska 1760, Ceske Budejovice, JC, CZ-37005, Czech Republic

dark germination
antheridiogen evolution

Presentation Type: Oral Paper
Session: PTER2, Pteridology II
Location: Virtual/Virtual
Date: Monday, July 27th, 2020
Time: 1:45 PM
Number: PTER2002
Abstract ID:117
Candidate for Awards:Edgar T. Wherry award

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