Janell Hillman

Constraints on recruitment of a rare serpentine seep endemic, Cirsium fontinale var. campylon (Mt. Hamilton thistle)

I am conducting an autecological study to examine environmental and biological constraints on the recruitment of the rare endemic Mt. Hamilton thistle (Cirsium fontinale var. campylon; CNPS List 1B, Federal Species of Concern) a perennial plant restricted to serpentine seeps in Alameda, Santa Clara and Stanislaus Counties.

My research is designed to test a series of related hypotheses about Mt. Hamilton thistle life history characteristics in Santa Clara County. Through an examination of seed production, dispersal, predation and germination I will examine biological constraints on recruitment of Mt. Hamilton thistle. In addition, I will examine potential environmental limiting factors such as moisture stress and water relations of transplanted seedlings at various moisture gradients in the wetland and surrounding upland habitat.

A demographic study of the life history stages of Mt. Hamilton thistle may be important not only in guiding the management and conservation of this rare taxon, but may also lend valuable information applicable to the life history stages of two closely related varieties which are state and federally listed as endangered, the fountain thistle (Cirsium fontinale var. fontinale) and Chorro Creek bog thistle (C. fontinale var. obispoense).

Janell Hillman at one of her sites.
One of the experimental populations surrounded by serpentine grassland.
Dispersal of the thistle. The pappus falls off almost immediately and seeds mainly end up beneath the parent.
Transplants at transition to grassland site.
Overview of riparian streams where Mt. Hamilton Thistle populations are restricted.
Janell setting up transplants.