RESULTS 



Discus brunsoni and Oreohelix elrodi 



Presence at different sites: Three talus sites within the general type locality of both species were 



examined during four different visits (Table 1). All sites were at 1 128 m along the trail paralleling 



McDonald Lake on its north side. On 10 June and 4 July, weather was sunny and warm (21- 



23°C) at the time of the searches (10:15-12:00); no precipitation had fallen in the previous 48 



hours. On both dates only Site 1 was checked. Four live estivating Oreohelix elrodi and no 



Discus brunsoni were found during 75 mm of searching by two persons on 10 June. The 4 July 



visit was devoted to study of the rocks and no live snails of either species were noted. 



On 1 July weather was wet and cool (10°C) during the search period (10:00-13:00); the 

 area received steady precipitation during the previous 48 h. At Site 1 I found 20 live Oreohelix 

 elrodi and 5 live Discus brunsoni in 120 min. At Site 2 I found 1 1 O. elrodi and no D. brunsoni 

 during 60 min. Under similar conditions on 10 July (wet, 14-17°C) I found 19 live O. elrodi and 

 3 live D. brunsoni at Site 1 during 120 min (1 1:00-13:00). At Site 2 I found 7 live O. elrodi and 

 no D. brunsoni in 30 min (13:30-14:00). At Site 3 I found 7 live O. elrodi and no D. brunsoni in 

 15min(15:35-15:50). 



Substrate selection within talus: Substrate of occurrence (rock, organic litter) for live snails 

 found at all three sites was documented on 1 and 10 July. All (n = 8) live Discus brunsoni were 

 found on bare or lichen-covered rock. Nine of 64 live Oreohelix elrodi were found on similar 

 substrate, 55 were found on organic litter accumulations (bark, twigs, leaf fragments, needles) or 

 live moss among the talus. The difference between the two species in frequency of substrate 

 occurrence was statistically significant (G = 26.724, df = 1, P < 0.001). 



