Antheridiogen Production and Response in Gymnocarpium dryopteris ssp. disjunctum

Abstract

Although most species of homosporous pteridophytes investigated to date are highly outcrossing, there is little conclusive evidence of the mechanisms promoting intergametophytic matings in natural populations. The hormone antheridiogen, produced by meristematic and usually archegoniate gametophytes, has been implicated as an effective promoter of intergametophytic matings in natural populations. In this study, antheridiogen production and response were analyzed in laboratory‐cultured gametophytes from five outcrossing populations of Gymnocarpium dryopteris ssp. disjunctum. The numbers of antheridia present in gametophytes grown on antheridiogen‐enriched and control nutrient agar were recorded over an 84‐day period; approximately 4200 gametophytes were observed. Contingency table analyses indicated a statistically significant positive response to treatment medium in the majority of cultures analyzed. However, consistently insignificant responses to treatment medium in two gametophyte cultures suggest intrapopulational variation in gametophytic response to antheridiogen. Antheridiogen production and response in gametophytes of G. dryopteris ssp. disjunctum suggest that this antheridiogen system effectively promotes intergametophytic matings in natural populations. The selection pressures under which antheridiogen systems may have evolved are also discussed.

Insights into the evolutionary history and widespread occurrence of antheridiogen systems in ferns

“…A recent estimate puts the number of fern species at 10 578 (PPG 1, 2016), meaning that 2% of all known fern species have now been tested for AG activity. This is a substantial increase from the < 1% tested that was estimated by Kirkpatrick & Soltis (1992). However, the vast majority of fern diversity remains unstudied.…”