Conservation assessment for Parish’s daisy (Erigeron parishii, Asteraceae) in Joshua Tree National Park

Fraga, Naomi; La Doux, Tasha; Prince, Linda; Harding, Mitzi; Hoines, Josh

Parish’s daisy (Erigeron parishii) is a perennial herb in endemic to southern California. It occurs in the San Bernardino and Little San Bernardino Mountains. In the western part of its range it occurs on calcareous substrates, on alluvium in washes and canyon bottoms. In the eastern part of its range it occurs on gneiss, granodiorite, and monzogranite, often on rocky slopes. E. parishii was listed as threatened by the federal government in 1994 due to habitat destruction associated with mining and threats from off-highway vehicle use and energy and urban development. At the time, E. parishii was thought to be restricted to calcareous soils in the San Bernardino Mountains. Little was known about populations in the eastern part of its range (off limestone), including in Joshua Tree National Park (JOTR). This report provides a review of species biology, ecology, distribution, taxonomy, conservation status, and provides management recommendations for JOTR populations. We present research on seed germination, reproductive biology, demographics, habitat preference and population genetics for E. parishii, with emphasis on plants occurring within JOTR. Germination trials between 1990-2013 indicate that plants have a high germination rate (75–100%) and do not require special treatment to break dormancy. Seeds stored for 25 years at low humidity (12–15%) and 20°C remain viable and showed high germination rate (100%). Demographic studies established long-term plots to track individuals over time. Reproductive biology data address flowering phenology and reproduction as related to size class. Plants in smallest size class (<50 cm3) had low survivorship and did not produce flowers. The population genetic study inter simple sequence repeat data found populations in the San Bernardino Mountains on calcareous substrates were more genetically diverse than populations on other substrates (in JOTR). However, each population had unique genetic diversity. The GIS habitat model used elevation, slope, aspect, soil type, and vegetation type to assign probability values of potential habitat to the landscape. These datasets characterized occupied habitat for E. parishii. Conservation efforts for E. parishii should focus on building on baseline data by supporting research, field surveys, and long-term monitoring. Proposed research includes expanding current population genetic study to determine levels of genetic diversity across the range and further evaluate genetic diversity between central and peripheral populations. Other useful research for future conservation would include a phylogenetic study to determine the closest relative of E. parishii and its phylogenetic uniqueness as well as an ecophysiological study on drought tolerance across the the species range. Management practices should include implementation of a standardized monitoring protocol as presented in this report and continued surveys to map occurrences. Future field surveys should use the habitat model to search for new populations as well as to improve the habitat model.

Conservation assessment for Parish’s daisy (Erigeron parishii, Asteraceae) in Joshua Tree National Park

Series

Collections