Tetraphis switches between clonal and sexual reproduction based on colony density

Evidence

Like a logger in miniature, I sat poised with fine forceps over the old, dense Tetraphis patches. One by one, I plucked out single shoots of Tetraphis, stem by stem, until the density was reduced by half. And then I let them be, returning the next year to observe if they had given me an answer to my question. The unthinned patches of Tetraphis remained male and had started to turn brown. But the patches where I’d opened the moss canopy by thinning were green and vibrant. The holes I’d made in the Tetraphis turf were being filled with thrifty young shoots, bearing gemmae cups at their tips. The mosses had answered, in their own way. Low density is a time for gemmae, high density for spores. The transformation to being male appears to have adverse consequences. Over and over, I observed that the dense male patches were starting to die back, becoming dry and brown. These tired male colonies, spent with reproduction, were then easily invaded by other mosses on the log. — Robin Wall Kimmerer, Gathering Moss, 340

Categorization

• XREF: This field-manipulation experiment — thin the canopy, wait, observe the response — is exactly the kind of minimal intervention observation the whole polyad prizes as method. — connects to: Stable habitats favor clonal asexual reproduction over sexual spore production — Robin Wall Kimmerer, Gathering Moss: A Natural and Cultural…, 317; Mosses evolved two reproductive strategies trading dispersal distance against genetic novelty — Robin Wall Kimmerer, Gathering Moss: A Natural and Cultural…, 323; Diversified flexibility confers resilience in unpredictable environments across scales — Robin Wall Kimmerer, Gathering Moss: A Natural and Cultural…, 343 (+1 more)
• STORYSTEM: The image of a colony that mates itself into local extinction, ‘spent with reproduction,’ while its sparse neighbors stay green, is a ready-made ecological fable about senescence and flexibility.