I’ve returned from two weeks of work in the field and two weeks of vacation, but here is another entry from Taisha today while I continue to catch up on correspondence. Taisha writes:
Thanks to Eric Hunt.@Flickr for this photograph of Castilleja lemmonii, or Lemmon’s Indian paintbrush. It was taken in July of 2009 in an alpine meadow between California’s Greenstone Lake and Saddlebag Lake, located in the Inyo National Forest of Mono County. Thanks, Eric!
Castilleja lemmonii is perennial species native to California. It is found in moist meadows in the southern Cascades and the Sierra Nevada at elevations of 1550-3700 m. Grey-green lanceolate leaves are held on an unbranched stem that can reach up to 20 cm in height. The inflorescence consists of a collection of pink to purple-red bracts that surround green tubular flowers.
Members of Castilleja are placed in the Orobanchaceae, but many older texts had them classified in the Scrophulariaceae. They are hemiparasitic, i.e., photosynthetic, but also receiving some nutrition from host plants. Castilleja species are noted to parasitize a wide range of plant species, and can also parasitize multiple hosts simultaneously. More specifically, Castilleja species are facultative root hemiparasites. Their roots grow until they touch the roots from another plant, whereupon they penetrate the roots with haustoria. The Castilleja receive water, fixed carbon compounds, nitrogen, other nutrients, and even secondary metabolites from the host.
Hemiparasites influence plant community dynamics and other trophic levels by a distinct suite of ecological traits. Most people may initially suspect that parasitic plants have mainly negative affects within a community, particularly with respect to their hosts. This is true to some degree where the parasitic plant competes with both host and non-host plants for light, water, nutrients, pollinators, and seed dispersers. However, according to some ecologists, parasites may actually increase the diversity within a community depending on whether or not the preferred host is the competitive, dominant species. If dominant, then its suppression of the dominant species may allow for other species’ populations to increase. Hemiparasites are also sometimes considered mutualists. The litter of hemisparasites is considered to be nutrient rich, and as this high-quality litter rapidly decomposes it provides nutrients for co-occurring plants. It also supports a more diverse and active soil biota.
To read more, you may wish to look over a paper by Phoenix and Press from the University of Sheffield where they discuss several aspects of the influence of Orobanchaceae on community dynamics (see: Phoenix, G., Press, M. (2005). Linking physiological traits to impacts on community structure and function: the role of root hemiparasites Orobanchaceae (ex-Scrophulariaceae). Journal of Ecology. 93(1): 67-78). You can also read a summary of their paper written by a graduate student from the University of Washington last year.