The relationship between chlorophyllous spores and mycorrhizal associations in ferns: evidence from an evolutionary approach

Abstract

Premise Approximately 14% of all fern species have physiologically active chlorophyllous spores that are much more short‐lived than the more common and dormant achlorophyllous spores. Most chlorophyllous‐spored species (70%) are epiphytes and account for almost 37% of all epiphytic ferns. Chlorophyllous‐spored ferns are also overrepresented among fern species in habitats with waterlogged soils, of which nearly 60% have chlorophyllous spores. Ferns in these disparate habitat types also have a low incidence of mycorrhizal associations. We therefore hypothesized that autotrophic chlorophyllous spores represent an adaptation of ferns to habitats with scarce mycorrhizal associations. Methods We evaluated the coevolution of chlorophyllous spores and mycorrhizal associations in ferns and their relation to habitat type using phylogenetic comparative methods. Results Although we did not find support for the coevolution of spore type and mycorrhizal associations, we did find that chlorophyllous spores and the absence of mycorrhizal associations have coevolved with epiphytic and waterlogged habitats. Transition rates to epiphytic and waterlogged habitats were significantly higher in species with chlorophyllous spores compared to achlorophyllous lineages. Conclusions Spore type and mycorrhizal associations appear to play important roles in the radiation of ferns into different habitat types. Future work should focus on clarifying the functional significance of these associations.

A new record of green spore in Lomaria (Blechnaceae, Polypodiospida)

“…Approximately 70% of fern species that produce chlorophyllous spores grow as epiphytes, making up almost 37% of all epiphytic fern species. The most common families for these ferns are Polypodiaceae (subfamily Grammitioideae) and Hymenophyllaceae, with a collective representation of over 100 species reported to have green spores (Mellado-Mansilla et al 2022). Fern species with chlorophyllous spores, which constitute almost 60% of those present in waterlogged soils, are overrepresented in these environments.…”

“…Fern species with chlorophyllous spores, which constitute almost 60% of those present in waterlogged soils, are overrepresented in these environments. (Mellado-Mansilla et al 2022). Lomaria spannagelii, a terrestrial fern species commonly found in Araucaria forests and areas with flooded soils, is particularly abundant along streams at higher altitudes (Dittrich et al 2018).…”

Fern mycorrhizae do not respond to fertilization in a tropical montane forest

“…This can be linked in part to the high proportion of ferns growing epiphytically (about 27% versus about 9% in angiosperms; Zotz et al., 2021) since overall mycorrhizal fungi are soil‐bound (Brundrett & Tedersoo, 2018; Willis et al., 2013). Mycorrhizae are also largely absent in fern species associated with swampy habitats, because arbuscular mycorrhizal fungi cannot tolerate the anoxic conditions of inundated soils (Helgason & Fitter, 2009; Mellado‐Mansilla et al., 2022; Tedersoo, 2017). Still, even among terrestrial ferns growing in forests, a considerable proportion of species has few or no AMF partners (Lehnert et al., 2017).…”

Comparative analysis of mycorrhizal communities associated with Struthiopteris spicant (L.) Weiss across Europe and North America

“…Consequently, ferns can provide valuable information about the diverse strategies developed by plants to overcome the challenges of the colonization of land ( Page, 2002 ). Although some of these strategies have been studied to some degree, others such as their biotic interactions have not received much attention yet ( Page, 2002 ; Mehltreter et al., 2010 ; Mellado-Mansilla et al., 2022 ). In particular, the ability of ferns to form partnerships with mycorrhizal fungi is one of the least studied aspects of their ecology ( Lehnert et al., 2017 ; Strullu-Derrien et al., 2018 ).…”