Seaside bone (Hypogymnia heterophylla) COSEWIC assessment and status report: chapter 7

Search effort

In the field, two person-days of search effort were expended at each of the four locations previously surveyed in the 1996 status report (Goward 1996) on southern Vancouver Island (May 18 and 19 at East Sooke Regional Park and May 20, 2006 at Sheringham Point); Hypogymnia heterophylla was found at all four locations (Figure 3) (Appendix 1).In addition, the coastlines along French Beach Provincial Park and the Qualicum coast area were surveyed for H. heterophylla without success (May 20, 2006). Bentinck Island, DND property, was surveyed September 18, 2006. Other locations in the region that were recently surveyed for lichens (2004-2006), including H. heterophylla, are Saltspring Island, Tofino and the shore forest to the south, Ucluelet coast, Mt. Washington, Cathedral Grove, Cowichan Bay Canyon, Sechelt Peninsula, Campbell River/Elk Falls and other areas on the south centre and east coast (S. Harris, pers. comm. 2007). Other British Columbia lichen collectors known to have collected lichens on Vancouver Island and/or the mainland were contacted by email regarding element occurrences of H. heterophylla in Canada (C. Bjork, T. Goward, T. Spribille pers. comm. 2007). None reported any element occurrences of H. heterophylla after 1996. Total search effort for British Columbia lichens is shown in Figure 4. The intense search effort in southern Vancouver Island is evident by the number of sites indicated by the high density of black dots representing sites searched for lichens.

Figure 4.Non-targeted search effort for lichens in British Columbia.

Figure 4.Non-targeted search effort for lichens in British Columbia.

Herbarium database search at the University of British Columbia (UBC) and the British Columbia Conservation Data Centre (CDC) indicate no collection of Hypogymnia heterophylla has been accessioned after 1996. The University of Washington Herbarium reports six accessions of H. heterophylla since 1996 in Washington State (K. Glew, pers. comm. 2007). Web searches of herbarium databases at the University of California at Riverside (UCR) and Santa Barbara Botanic Garden (SBBG) indicate that H. heterophylla occurs as far south as the Channel Islands and along the Pacific Ocean coast to the Los Angeles area (Figure 2). This range has been extended south due to extensive lichenological collections on the Channel Islands in the early 1990s. Search of the Mycological Herbarium database at Oregon State University (OSU) revealed several recent collections of H. heterophylla in Oregon and California.

Abundance

Goward (1996) reported that Hypogymnia heterophylla was relatively abundant within its range on Vancouver Island. Populations are listed in Appendix 1, and indicate that the most abundant sites had > 100 thalli while the least abundant sites had > 10 thalli. These estimates may be low as branches higher up in the trees could not be assessed.

Hypogymnia heterophylla is abundant on coastal conifers and hardwoods in northern California and Oregon, but less common in Washington and British Columbia.

Fluctuations and trends

Search effort in May and September 2006 show that population sizes of Hypogymnia heterophylla appear to be stable (Appendix 1). The lichen was found again at the Sheringham location where it had been absent in the 1996 status report (Goward 1996). As indicated in Appendix 1, population sizes appear not to have changed since the 1996 survey, as it was observed that populations of this species were fairly abundant at most locations. However, the recent 2006/2007 severe winter storms may have reduced the populations of H. heterophylla in East Sooke Regional Park, as many individual shore pine trees along the coast were toppled or damaged (J. Miskelly pers. comm. 2007)

Rescue effect

In the past ten years populations of Hypogymnia heterophylla have been found in nearby Puget Sound, Washington state, located south (across Georgia Strait) of the Canadian populations on the southwest coast of Vancouver Island. These populations may provide a source for H. heterophylla populations in Canada.

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