Factors affecting persistence of Wenatchee Mountains checker-mallow : An exploratory look at a rare endemic

Loss of suitable habitat has historically been the primary threat to Wenatchee Mountains checker-mallow (Sidalcea oregana var. calva), a narrow endemic of Chelan County, Washington. The largest population of this federally listed endangered species is now protected from loss by Natural Area Preserve status, yet the survival of the plant is still in jeopardy. Possible threats to population growth and persistence include seed predation by weevils, succession in meadow habitats due to fire suppression, and loss of pollinator populations. This two-year exploratory study examined these threats in an effort to determine their relative impacts on the species and to guide future study. Macrorhoptus sidalceae, a Sidalcea specialist insect was identified as a primary seed predator. Seed predation by this weevil was severe; only 17% of seeds examined escaped weevil predation across all study sites. Few significant differences were found in prescribed burn experiments designed to determine effects of fire on checker-mallow individuals and on the surrounding herbaceous community. This may indicate that the species is not detrimentally affected by fire, and that prescribed fire may be a valuable management tool for habitat conservation. A second Sidalcea specialist insect, the bee Diadasia nigrifrons, was observed to be a consistent flower visitor and possibly important pollinator of the checker-mallow. These results have implications for future study and management of both the checker-mallow and other endangered species, because it is common for an imperiled species to be threatened by numerous impacts that must all be considered simultaneously for population maintenance.