A comparative study of cultured and field plants provides evidence for the shy male hypothesis in tropical genotypes of Bryum argenteum Hedw.

ABSTRACTIntroduction The female-biased sex ratio is recurrently observed in bryophyte populations, although the sex ratio of spores is usually balanced. The results of several studies have suggested explanations for this observation, one of which is the shy male hypothesis. The shy male hypothesis predicts that the sex ratio of populations is balanced in the field, but due to a low or lack of sex expression of male plants, the populations present a female bias when the sex ratio is based on observations of sex-expressing plants.Methods We tested the shy male hypothesis using samples of the moss Bryum argenteum collected from Brazilian seasonally dry tropical forests and the Brazilian Atlantic Forest. Field sex ratios were determined by classifying shoots as male, female, or non–sex-expressing. Non–sex-expressing shoots were further analysed for sex expression after culture regeneration.Results and discussion Our results showed that populations of Bryum argenteum in the field had a low rate of sex expression, and that most of the shoots expressed were female. However, when shoots without sex expression were cultured, a greater number of male shoots were observed compared with in the field plants. Because more males appeared in the shoots cultured from non–sex-expressing field plants, our data for tropical B. argenteum tend to support the shy male hypothesis. Some genotypes from the wet forest were synoicous (i.e. had male and female gametangia in the same gametoecia), suggesting polyploidy.KEYWORDS: Dioicygametangia productionlabile sexmosssex expressionsex ratio AcknowledgementsWe thank Raimundo Guaraci do Carmo Cardoso for allowing us to collect samples of Bryum argenteum in Parque Pedra do Cachorro, and the management of Parque das Neblinas for allowing us to collect in that park. We also thank the researchers Bianca Kalinowski Canestraro and Lucas Matheus da Rocha for confirming the identification of the collected samples.Disclosure statementNo potential conflict of interest was reported by the authors.Supplemental materialSupplemental material for this article can be accessed here: https://doi.org/10.1080/03736687.2023.2251776.Supplemental Table 1. Summary of data for samples collected from 52 populations of Bryum argenteum in dry and wet forest in Brazil.Additional informationFundingThis work was supported by the American Bryological and Lichenological Society (ABLS) through the Anderson & Crum Field Bryology Research Award; the Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) under Grant [2021/09506-0], [2018/24397-0] and [2020/02150-3]; and the Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) under Grant [CNPq: 302849/2021-1]. This study was also financed in part by the Coordenação de Aperfeiçoamento de Pessoal de Nível Superior – Brasil (CAPES) – Finance Code 001.Notes on contributorsWagner Luiz dos SantosWagner Luiz dos Santos is a Ph.D. candidate enrolled in the Ecology Graduate Programme at the University of Campinas, Brazil.Kátia Cavalcanti PôrtoKátia Cavalcanti Pôrto is Professor of Plant Biology at the University of Pernambuco, Brazil.Joshua GreenwoodJoshua Greenwood is a postdoctoral researcher at the University of Nevada, Las Vegas, USA.Andie DavisAndie Davis is an undergraduate student of biology at the University of Nevada, Las Vegas, USA.Fábio PinheiroFábio Pinheiro is Professor of Plant Biology at the University of Campinas.Lloyd R. StarkLloyd R. Stark is Professor of Ecology at the University of Nevada, Las Vegas, USA (https://www.researchgate.net/profile/Lloyd-Stark).