Meeting Abstract

78.5  Monday, Jan. 6 11:15  A mechanism for extinction: Recruitment failure in a sky-island population of Sceloporus occidentalis ARCHIE, J.W.*; HOOPER, C.; California State Univ., Long Beach; California State Univ., Long Beach James.Archie@csulb.edu

Population extinctions are likely common, but seldom observed in the wild. We document the likely extinction of a sky-island population of western fence lizard, Sceloporus occidentalis, due to failure of annual recruitment of juveniles. Populations of WFL on Ord Mountain in the Mojave Desert have been monitored over a period of 4 years (2010-2013) on two 1-hectare sampling grids, one at 1450m and the other at 1850m. The frequency of captured and marked first-year lizards in the population varied from 13% to 54% of all marked lizards during the first 3 years of study (from 55-83 total lizards captured annually). During 2013, this frequency dropped to 0% as no first-year lizards were found either on the sampling grids or anywhere on the mountain (10 sampling days and 225 person-hours of searching). During the 2011-2012 and 2012-2013 wet seasons (November-March), the Mojave Desert experienced extreme drought conditions which resulted in highly reduced annual and perennial plant production and reduced insect abundance. Adult survivorship on the sampling grids increased during 2013 and may be a result of lack of dispersal from the sampling grids or lack of avian or other predators. A total of 3 hatchling lizards have been seen during July and August 2013. While the high elevation population remains robust, lack of juvenile recruitment is the likely mechanism for extinction of the low elevation population.