St. John, D., and S. Desjardins. 2003. Biogeography of Behr’s hairstreak (Satyrium behrii columbia McDunnough 1944) in the South Okanagan. Part 1: inventory survey and mapping. Part 2: mark recapture study. Unpublished report. Okanagan University College, Kelowna, British Columbia. 18 pp. Biogeography of Behr’s Hairstreak, Satyrium behrii columbia (McDunnough 1944) in the South Okanagan (Analysis of data collected in 2003 and earlier) PART 1. Inventory Survey and Mapping Introduction Behr’s Hairstreak (Satyrium behrii W. H. Edwards, 1870) is confined to the south Okanagan Valley of British Columbia in Canada(Guppy & Shepard, 2001). Kondla (2003) estimates the Canadian distribution at less than 1% of the global distribution of this species. The species ranges south to southern California, northern Arizona and New Mexico, and an outlier population is found in northwest Texas. From about the middle of Oregon, north to British Columbia, the species’ range narrows to a thin band terminating in British Columbia south of Penticton. This range follows the eastern boundaries of the Oregon and South Cascades Ecogeographic Provinces into Washington state, and parallels the course of the Columbia eastward to Spokane County, and northward along Okanagan river system into BC (Opler, 1999, Pyle 2002). The subspecies Satyrium behrii columbia(McDunnough,1944) is the taxon found in BC and throughout Cascadia(Pyle, 2002). The type locality is at Fairview near Oliver (Guppy & Shepard, 2001). In Cascadia, including BC, antelope brush (Purshia tridentata (Pursh)) is the only known larval foodplant of Behr’s Hairstreak (Guppy & Shepard 2001, Shepard 2000, Pyle 2002). Previous field work indicates that yarrow (Achillea millefolium L.) is the most widely utilized nectar source. Smooth sumac ( Rhus glabra L.), gray horse-brush (Tetradymia canescens DC), baby’s breath (Gypsophila paniculata L.) sweet clover (Melilotus sp Mill.) and ocean spray(Holodiscus discolor (Pursh)) have also been reported as nectar sources in the Okanagan (pers comm. S. Bunge, Or. Dyer, C.S. Guppy and per obs). Pyle (2002) reports it using buckwheats (Eriogonum sp Michx.) as a nectar source but this has not been observed in the Okanagan to my knowledge. Kondla (2003) comments that research is needed to determine whether Behr’s hairstreak is involved in a mutualist relationship with ants. This is a very cogent suggestion since the larvae of this species possesses a honey gland and dendritic setae, which are indicative of ant association (Ballmer & Pratt 1989). Behr’s Hairstreak larvae also have been found to be highly effective at inducing ant attendance in an experimental study using butterflies and ant species found in California (Ballmer & Pratt 1991). There is apparently no direct field evidence concerning possible ant association in nature. It is important to attempt to assess the relationship with ants in Okanagan populations. Lycaenid butterflies may be found in association with several species of ant. Some of these associations may be beneficial to the fitness of the butterfly involved, while others may have a negative effect on survival, depending on the species of ant attending the larvae ( Fraser et al 2001). The type of relationship, and the ant species involved, may well be an important factor in determining the habitat quality of sites, in addition to the presence of antelope brush and adequate nectar sources. In the Silver Studded Blue (Plebejus argus) presence of its ant mutualist has been found to be more effective than nectar source density in determining dispersal (Seymour et al 2003). Therefore it may be important to assess the ant diversity and abundance, at known and potential habitat sites. 1 St. John, D., and S. Desjardins. 2003. Biogeography of Behr’s hairstreak (Satyrium behrii columbia McDunnough 1944) in the South Okanagan. Part 1: inventory survey and mapping. Part 2: mark recapture study. Unpublished report. Okanagan University College, Kelowna, British Columbia. 18 pp. Methods Surveys for Behr’s Hairstreak were carried out between June 16th and June 27th of 2003 . Surveys ranged from approximately the northern boundary of Osoyoos in the south, to the north end of Vaseux Lake on the east side of the valley, and to about ¼ of the way up the Vaseux Lake on the west side. Samples were conducted by teams of observers traversing the terrain at a slow walking pace maintaining a distance between observers of about 20 m. Particular attention was focused on as it is frequently used by nectaring hairstreaks. Antelope brush plants encountered were scanned for the presence of butterflies and tapped with net poles to encourage any unseen animals to take flight. Any Behr’s Hairstreak detected was recorded along with the time, UTM coordinates and a brief description of its activity (eg nectaring on yarrow) and a crude characterization of the habitat within a 10m radius of the sighting. Start and stop times were also recorded so that Behr’s Hairstreak encounter rates could be expressed as sightings/observer/hour. Sampling time was expressed as observer-minutes from a calculation based on duration of the transect and record the number of observers. An effort was made to obtain complete coverage of the polygon area being surveyed. Survey personnel included both those with previous field experience and first-time volunteers. In practice sampling distance between observers varied considerably, transect start and stop times were often omitted and polygon coverage varied among sessions. Where session durations were not directly available times of first and last sightings were used to obtain crude biased estimates. Data treated in this way underestimates the sampling times and correspondingly overestimates the encounter rate Surveys for Behr’s and California Hairstreaks were conducted mainly in polygons where antelope brush (Purshia tridentate) was a recognized component (Harper et al., 1996, Lea et al., 1991. A small number of sightings (4)were made in other polygon types in this year’s surveys and a number are included from previous years (8), but most of the surveying was confined to map units AN,AE , and PA(see appendix I for definitions). These map units were used as the basis for drawing habitat islands, composed of networks of contiguous or nearly contiguous (less than 1km separation) antelope brush containing units. The habitat islands resulting from this analysis are meant as heuristic fictions, enabling discussion of the present results and yielding suggestive rationales for future surveys. Present boundaries are intended to highlight the degree of apparent connectivity of existing habitat units in the region and outline the suitable polygons with about a five hundred metre boundary in most of the map. Computer generated mapping was not employed as it made no distinction between different types of intervening habitats whereas the subjective mapping is based on the assumption that cultivated fields high sheer cliffs and riparian areas represent more formidable barriers to butterflies than habitat types which are more like the mapped units in physiographic and floral composition. Maps of the surveyed areas also indicate polygon units that may contain antelope brush although that species is not part of the defining description of the units. These include WB, WS, PS, SS, SW and SN map units. In addition to the mapping provided by Harper et al (1996) mapping provided by Sarell et al(2001) identified polygons which they found to be antelope brush dominant although they had been otherwise identified in the mapping by Harper et al. 2 St. John, D., and S. Desjardins. 2003. Biogeography of Behr’s hairstreak (Satyrium behrii columbia McDunnough 1944) in the South Okanagan. Part 1: inventory survey and mapping. Part 2: mark recapture study. Unpublished report. Okanagan University College, Kelowna, British Columbia. 18 pp. Results The west side of the Okanagan drainage system is characterized by a more fragmented distribution of habitat units mapped as containing antelope brush as well as having a much smaller area of these units (see maps 1a & 1b). Based on the admittedly incomplete sampling accomplished to date the populations of Behr’s Hairstreak are also more fragmented on the west side. Fig 1. below, shows the distribution of minimal distances over 1km between Behr’s sightings. The largest 4 distances between observations are all on the west side and average 8.8km whereas the largest 4 on the east side average 4.8 km. The larger number of smaller distances on the east side of the valley reflects more intensive sampling there. Distances over 1km between Behr's Hairstreak Sightings on the East and West Sides of the Okanagan Drainage 14 12 10 West side 8 distances (km) km 6 East side distances (km) 4 2 0 1 3 5 7 9 11 rank order Fig 1. The distances between the areas identified as habitat islands are also greater on the west than on the east side of the valley’s drainage system (fig 2.) 3 St. John, D., and S. Desjardins. 2003. Biogeography of Behr’s hairstreak (Satyrium behrii columbia McDunnough 1944) in the South Okanagan. Part 1: inventory survey and mapping. Part 2: mark recapture study. Unpublished report. Okanagan University College, Kelowna, British Columbia. 18 pp. Minimum distance between polygons mapped as containing Antelope Brush in adjacent Habitat Islands 5 4.5 4 3.5 3 2.5 Km 2 1.5 West side gaps 1 (km) 0.5 East side gaps 0 (km) 1 3 5 7 9 11 Rank Order Fig 2. Fifty two survey locations were visited during the study. Named locations, times, number of observers, Behr’s seen, and estimated encounter rates can be found in Appendix II. Table 1 presents a summary of the location data with locations assigned to high, moderate, low, and empty abundance classes. The table shows that high and moderate abundance classes are found disproportionately on the east side of the valley, low abundance classes were essentially proportionately found on either side, and the number of empty locations were concentrated on the west side of the valley.