Endangered Species Recovery Program

Association of San Joaquin woolly-threads with
giant kangaroo rat precincts on the Carrizo Plain

Presented To

Elk Hills Endangered Species Program Review
Bakersfield, CA
1995

by

Ellen A. Cypher

Abstract

The distribution and phenology of San Joaquin woolly-threads (Lembertia congdonii) individuals relative to giant kangaroo rat (Dipodomys ingens) precincts were investigated at three sites on the Carrizo Plain during the growing seasons of 1994 and 1995. Two of the sites (Center Well #1 and #2) were subject to cattle grazing, whereas the third site (Swain) was not grazed by livestock during the study period. In belt transects at each site, all San Joaquin woolly-threads individuals were tallied as on or off precinct as well as by phenological stage. Coverage of the belt by precincts was estimated in order to determine the expected frequencies of San Joaquin woolly-threads on precincts and in interspaces.

The likelihood of San Joaquin woolly-threads plants occurring on precincts varied among sites but did not differ between years on a given site. Relative to the area occupied by precincts, San Joaquin woolly-threads occurred on precincts with greater frequency than expected at Center Well #1, with lesser frequency than expected at Center Well #2, and with the expected frequency at the Swain site. Intrinsic site factors apparently account for the different distribution patterns among sites. Phenology of San Joaquin woolly-threads was affected by giant kangaroo rat precincts only at Center Well #1, where plants on precincts began flowering earlier than those in interspaces. Accelerated flowering may confer a selective advantage to plants on precincts in years when growing seasons are shortened by abbreviated rainfall or unseasonably high temperatures.