Dicranum’s dwarf males are an evolutionarily efficient fertilization solution
Evidence
But from the evolutionary perspective of Dicranum, the asymmetry of the sexual relationship matters a great deal. Dwarf males are an efficient solution to the problem of getting fertilized. The entire species, both sexes, benefits from this arrangement. Afull-size male actually stands in the way of his own genetic success, his leaves and branches increasing the distance between sperm and egg. A dwarf male will produce many more offspring than will a full-size male. He can best contribute to the next generation by delivering sperm and then getting out of the way. The very same impulse that propels sister species to diverge from one another creates the sharp difference between Dicranum males and females. Competition in a family decreases everyone’s potential success. So evolution favors specialization, avoiding competition, and thus increasing the survival of the species. A large female and a dwarf male cannot compete with each other. The male is small, to better deliver sperm. The female is large to nurture the resulting sporophyte, their future, their offspring. Without competition from their mates, females get all of the good habitat, the light and water and space and nutrients, all for the benefit of the offspring. — Robin Wall Kimmerer, Gathering Moss, 165
Categorization
- XREF: Sexual dimorphism as specialization-to-avoid-competition echoes ch10’s habitat-segregation-of-the-sexes thread on sex determination and is a strong model for observational inference. — connects to: Invertebrates act as unwitting couriers of moss sperm beyond water’s reach — Robin Wall Kimmerer, Gathering Moss: A Natural and Cultural…, 265
- SEED: A short piece or lecture bit: evolution favoring specialization means each sex’s body is literally shaped by the other sex’s competition — a striking entry point to sexual selection that generalizes outside bryology.
Broader Connections
- Invertebrates act as unwitting couriers of moss sperm beyond water’s reach
#expands(0.75) — Robin Wall Kimmerer, Gathering Moss, 265