M ETHODS: We determined whether S. sitchensis secondary sex ratios varied across disturbance zones created by the eruption and across mesic and hydric habitats within each zone. For one population, we tracked adult mortality, whole-plant reproductive allocation, the number of stems, and plant size for 2 years. In a fi eld experiment, we created artifi cial streams to test whether vegetative reproduction via stem fragments was sex-biased.
K EY RESULTS: We found a consistent 2:1 female bias in S . sitchensis secondary sex ratios across all disturbance zones and habitats. Despite female plants sometimes allocating more resources (in terms of carbon, nitrogen, and phosphorus) to reproduction than males, we found no evidence of sex-biased mortality. The establishment rate of S. sitchensis experimental stems did not diff er between the sexes, indicating that vegetative reproduction was not distorting secondary sex ratios.
CONCLUSIONS: We hypothesize that S . sitchensis secondary sex ratios depend on either early-acting genetic factors aff ecting the seed sex ratio or sexspecifi c germination or survival rates before maturity, as opposed to factors associated with reproduction in adult plants.