Plant and Microbial Biology Program, College of Biological Sciences, University of Minnesota Twin Cities, St. Paul, MN, 55108, USA.
Biology Department, Hope College, Holland, MI, 49423, USA.
Am J Bot. 2022 Aug;109(8):1313-1325. doi: 10.1002/ajb2.16040. Epub 2022 Aug 18.
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 tested whether the sexual structure of gametophytic colonies of a tree fern were attributable to antheridiogen.
Gametophytic colonies of the antheridiogen-producing tree fern 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.
In all gametophytic 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 expression, indicating male sex expression was spatially associated with females.
This study provides the first documentation of spatial sex expression in natural settings of gametophytes of an antheridiogen-producing tree fern species. The profound impact of antheridiogen on gametophytic sex expression in field settings suggests this system is intimately tied to mating system, fitness, and genetic diversity in Cyathea multiflora.
雄配子体生殖腺系统是一套控制蕨类配子体性别表达的信息素机制。然而，除了实验室研究之外，人们对其在自然环境中的功能知之甚少。我们结合基于野外和实验室研究的预测，测试了一种树蕨的配子体群体的性别结构是否归因于雄配子体生殖腺系统。
2019 年 1 月，在哥斯达黎加的拉塞尔瓦生物站收集了产生雄配子体生殖腺系统的树蕨 Cyathea multiflora 的配子体群体。确定每个配子体的性别，进行绘图，并使用空间统计方法来检查每个群体中性别分布。
在所有的配子体群体中，雄性最为常见，占个体的 62-68%。在任何一个群体中都没有发现两性配子体。基于四分体的方法表明，雌性配子体在每个群体中没有聚集，而雄性配子体则聚集在一起。在两个群体中，雄性的 K(r)检验统计量大于随机模拟的性别表达，这表明雄性的性别表达与雌性的空间存在关联。
本研究首次提供了自然环境中产生雄配子体生殖腺系统的树蕨物种配子体空间性别表达的证据。在野外环境中，雄配子体生殖腺系统对配子体性别表达的深远影响表明，该系统与交配系统、Cyathea multiflora 的适应性和遗传多样性密切相关。
