. The Canadian field-naturalist. Natural history; Sciences naturelles. 2006 Douglas and Ryan: Bikus-i (m/i (jii. 155 idcntial development and have been essentially elimi- nated outside parks or ecological reserves. Direct habi- tat destruction, however, is no longer the most impor- tant threat. It is the loss of suitable sites outside the current occupied area of that severely limits the potential for this species to spread into new areas and therefore, threatens its long-term survival in Canada. Less direct factors which threaten known popula- tions include
. The Canadian field-naturalist. Natural history; Sciences naturelles. 2006 Douglas and Ryan: Bikus-i (m/i (jii. 155 idcntial development and have been essentially elimi- nated outside parks or ecological reserves. Direct habi- tat destruction, however, is no longer the most impor- tant threat. It is the loss of suitable sites outside the current occupied area of that severely limits the potential for this species to spread into new areas and therefore, threatens its long-term survival in Canada. Less direct factors which threaten known popula- tions include the introduction of aggressive European species. These species have resulted in substantial changes to the grass-dominated meadows associated with Quercus garryana and the rocky xeric sites in the Victoria area. One of the most devastating species is Scotch Broom (Cytisus scopariits). This species has become a dominant shrub on xeric, exposed sites throughout much of southeastern Vancouver Island and the Gulf Islands and either competes with native plants such as for resources or pre- vents the establishment of their seedlings. Furthermore, the suppression of natural and unnat- ural periodic fires may have resulted in changes to the vegetation of many sites where this species would be expected to occur. In the past, aboriginal peoples prob- ably set fire to many of these sites to maintain them as an important habitat for food plants and wildlife (Roe- mer 1972). During the past century these sites have experienced little disturbance resulting in increased domination of some sites by trees and shrubs, especially introductions, that effectively eliminate many herba- ceous species. Another limiting factor is grazing. M. Fairbams (personal communication) observed that grazing prior to seed set had greatly limited seed production and caused reduced vigour among established plants on Bentinck Island. Finally, demographic constraints also play a role in the viability
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