Summarizing Visitation and Conservation Actions for Two Federally Listed Plant Taxa (Malacothrix indecora and M. squalida, Asteraceae)

Abstract

The California Floristic Province is recognized as a global biodiversity hotspot due to the large proportion of endemic taxa in the region. Nestled along the coast of California, the Channel Islands archipelago also supports a large number of endemic vascular plant taxa and thus could be considered a biodiversity hotspot within a hotspot. One of the best examples of vascular plant endemism and diversification on the Channel Islands is the Malacothrix foliosa complex (Asteraceae), which comprises 6 or possibly 7 insular endemics. Of the 7 island-endemic taxa in the complex, 2 are listed as federally endangered: M. indecora and M. squalida. Both annual herb species were listed as endangered under the federal Endangered Species Act in 1997 and are restricted to coastal forblands and rock outcrops. Here, we present a comprehensive summary of 139 years of knowledge about the distribution, population sizes, and seed collections related to these endangered species. At the time of listing, M. indecora was known from 6 occurrences; presently, in 2024, the species is known from 8 occurrences, one of which is potentially extirpated. In 1997, M. squalida was known from 4 occurrences; in 2024, the species is known from 5. Of the 5 occurrences, 4 are likely extirpated and 1 population is extant. In addition to summarizing the status of these species, we also address ongoing conservation challenges and future recovery needs.

Citation

Ayers, A., Schneider, H.E., Knapp, J., Hasenstab-Lehman, K.E. and Guilliams, C.M., 2025. Summarizing visitation and conservation actions for two federally listed plant taxa (Malacothrix indecora and M. squalida, Asteraceae). Western North American Naturalist, 85(2), pp.341-358.