Am J Bot. 2022 Jul 21. doi: 10.1002/ajb2.16040. Online ahead of print.
BACKGROUND AND AIMS: Antheridiogen systems are a set of pheromonal mechanisms that control sex expression in fern gametophytes. However, antheridiogen has rarely been studied outside of the laboratory and little is known about its function in natural settings. Combining predictions based on field and laboratory study, we test if the sexual structure of tree fern gametophyte colonies is attributable to antheridiogen.
METHODS: Gametophyte colonies of the antheridiogen-producing tree fern species Cyathea multiflora were collected at La Selva Biological Station in Costa Rica in January 2019. The sex of each gametophyte was determined, mapped, and spatial statistic approaches were used to examine the distribution of sex in each colony.
KEY RESULTS: In all gametophyte colonies, males were most common, representing 62%-68% of individuals. No hermaphroditic gametophytes were identified in any colony. A quadrat-based method showed female gametophytes were not clustered in each colony while male gametophytes were clustered. In two of the colonies, the K(r) test statistic for males was greater than expected compared to random simulations of sex, indicating male sex expression was spatially associated with females.
CONCLUSIONS: This study provides the first documentation of spatial sex expression in natural gametophyte settings of an antheridiogen-producing tree fern species. The profound impact of antheridiogen on gametophyte sex expression in field settings suggests this system is intimately tied to mating system, fitness, and genetic diversity in Cyathea multiflora. This article is protected by copyright. All rights reserved.