AMY VANDERGAST^1,4, DAVID WEISSMAN², MICHAEL CATERINO³, TOD REEDER⁴, AND ROBERT FISHER<sup>1

1</sup> USGS, Western Ecological Research Center, San Diego Field Station, San Diego, CA 92123
² California Academy of Sciences, Department of Entomology, San Francisco, CA 94118
³ Santa Barbara Museum of  Natural History, Santa Barbara, CA 93105
⁴ San Diego State University, Department of Biology, San Diego, CA 92182
  avandergast@usgs.gov

The Jerusalem crickets (genus Stenopelmatus; Orthoptera Stenopelmatidae) of California are poorly known taxonomically, and have remained virtually unstudied.  Until recently, the group was thought to be represented by only 7 species, due to high phenotypic similarity.  However, ongoing behavioral research by Dr. David Weissman (California Academy of Sciences) has uncovered many populations with unique mating songs.  Based on his work, Weissman estimates that there may be as many as  30 to 50 “song species” throughout California, suggesting that Stenopelmatus has in fact undergone an extensive species radiation.  One such song species (Stenopelmatus n. sp. “mahogany”) is found exclusively in Southern California on sandy soil substrates (oak woodland, riparian, chaparral and coastal sage scrub), ranging north to the Santa Monica Mountains, east to the San Gabriel, San Bernadino and San Jacinto Mountains and south to Torrey Pines State Park.  The mahogany Jerusalem is physically quite distinct; it is the second largest insect species known in California, and lacks the abdominal striping pattern found in all other Stenopelmatus species.

Mahogany Jerusalem Cricket (photo by David Weissman)

Scope of the Project

Researchers at USGS San Diego Field Station are conducting a population genetic study of the mahogany Jerusalem cricket throughout its range, in collaboration with Dr. David Weissman and Dr. Michael Caterino (Santa Barbara Natural History Museum).  The reasons behind this study are twofold.  First, a genetic study will allow us to determine historical gene flow linkages throughout the southern California landscape, adding to the current understanding of diversification and speciation within Stenopelmatus. Second, a genetic study will allow insight into how anthropogenic landscape changes (habitat destruction and fragmentation) have impacted the population structure of this species.  The fairly wide distribution of the mahogany Jerusalem cricket (see Distribution Map) and song cohesion throughout its range suggest that, historically, mahogany Jerusalem cricket populations have maintained high levels of gene flow.  However, remaining populations in many coastal and montane areas are now highly fragmented.  Fragmentation and isolation of the coastal sage scrub has increased dramatically over the last 60 to 100 years.  It is likely that fragmentation has severely limited the movement of these large flightless insects among remaining habitat patches. This reduction in dispersal and gene flow should manifest itself in reduced genetic variation within populations and increased differentiation among populations.
 

Individual crickets have been collected throughout the species range in conjunction with the extensive herpetofaunal monitoring program also being conducted at USGS BRD.  All genetic lab work is being conducted in Dr. Tod Reeder's laboratory in the Dept. of Biology at San Diego State University.  We are gathering sequences from the Mitochondrial Cytochrome Oxidase I gene, a commonly used molecular marker for both population genetic and species-level phylogenetic studies.  Preliminary results suggest that there is a high level of genetic population differentiation among the populations sampled.

Once completed, this genetic data set will be incorporated into a larger study in which we will compare the distribution of genetic variation within several species of diverse evolutionary lineages that inhabit Southern California.  This comparative phylogeographic analysis will identify important physical landscape features that have shaped patterns of variation and diversification throughout the region.  Ultimately, we hope to incorporate information on regional evolutionary processes into conservation planning.

This research is funded by NSF Grant # DBI-0204447

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