Cryptic paw (Nephroma occultum) COSEWIC assessment and status report: chapter 7

Population Sizes and Trends

Search effort

Most Canadian populations of Nephroma occultum occur on unprotected Crown Land which is subject to forest harvesting. Fieldwork in 2004 by P. Williston focused on determining the condition of unprotected populations of N. occultum in the Kispiox Valley, a region known to support several documented localities of this lichen, and which also is subject to active forest harvesting. Two days (September 23 and 24, 2004) were spent relocating previously documented localities and searching for new ones. The surveys took place along the Date Creek and Helen Lake Forest Service Roads in the Kispiox Valley, approximately 16 kilometers north of Hazelton, British Columbia. Representative collections and photographs were taken at most sites. Measurements of thallus lengths were recorded at four sites to better understand the population structure and GPS coordinates were recorded wherever cryptic paw lichen was found.

Lichenologists have collected macro-lichens in many parts of British Columbia. Sites visited by lichenologists as part of non-targeted surveys are shown in Figure 6 and are mapped against the CWH and ICH biogeoclimatic zones where potential habitat for the species may exist.

In Canada, where lichen surveys are not required in forest harvesting plans even in areas with habitat for rare species, there have been 24 newly discovered populations of Nephroma occultum since 1994. In Oregon, where lichen surveys have been integrated into forest harvesting practices, 182 populations of N. occultum have been documented in the past 10 years (see Appendix 1, Figure 7).

Populations

The populations listed in Table 1 combine those from the initial report (Goward 1995a) with those discovered after it was published. Included are populations documented during the field work carried out in 2004 by P. Williston, as well as data from additional discoveries by Trevor Goward and Toby Spribille since 1994. Twenty-four new locations have been documented in Canada since 1994 and two populations have been extirpated due to forest harvesting. As of December 2004, there are 45 extant populations of Nephroma occultum in Canada. These are listed in Table 1, arranged by date of the most recent observation at each location. There are also 6 populations known from Alaska, 8 from Washington and 182 from Oregon, for a global total of 241. Populations range in size from 1 to about 40 individuals. With a conservative approximation of 10 individuals (a single thallus represents one individual) per population, we can estimate there to be at least 450 individuals within Canada, and approximately 2,410 worldwide. Given the low search effort throughout most of the Canadian portion of the range, it is highly probable that the actual total number is considerably greater.

Extirpations

Two extirpations of Nephroma occultum populations have been documented and are listed below (dates refer to when the population was first recognized as extirpated). Both extirpations resulted from forest harvesting. It is highly likely that many additional populations have been extirpated in the past from the same cause. Localized extirpations almost certainly continue today throughout much of the Canadian portion of this species’s range wherever harvesting occurs in humid, old growth cedar-hemlock forests.

  1. Hazelton area. Lat./Long. 55°18’N 127°37’W. Elevation 400 m. 24 August 1992. T. Goward. Due to forest harvesting.
  2. Kispiox area, Helen Lake Forest Service Road. Lat./Long. 55°31’18”N 127°58’08”W. Elevation ca 500 m. 24 August 2004. P. Williston. Due to forest harvesting.

Figure 6. General collecting localities for macro-lichens in British Columbia, based on specimen data at the Cryptogamic Herbarium, University of British Columbia. Coloured polygons are CWH and ICH biogeoclimatic zones.

Figure 6. General collecting localities for macro-lichens in British Columbia , based on specimen data at the Cryptogamic Herbarium, University of British Columbia.(See long description below)
Description of Figure 6

Lichenologists have collected macro-lichens in many parts of British Columbia. Sites visited by lichenologists as part of non-targeted surveys are shown in Figure 6 and are mapped against the CWH and ICH biogeoclimatic zones where potential habitat for the species may exist.

Table 1. Extant locations of Nephroma occultum in Canada, arranged by date of the most recent observation at each location
Location number Locality Elevation Collection date Collector
1. Hazelton area 730 m 19 August 1981 T. Goward 81-1876
2. New Aiyansh area 60 m 24 August 1981 T. Goward 81-2003
3. Taku River 150 m 10 July 1982 T. Goward
4. Sayward area 100 m 7 July 1991 T. Goward 91-704
5. Kispiox area, near Date Creek 450 m 23 August 1991 T. Goward 91-932
6. Terrace area 375 m 25 August 1991 T. Goward 91-1064
7. Terrace area 200 m 26 August 1991 T. Goward
8. Kitimat Village 0-10 m  28 August 1991 T. Goward 91-1240
9. Shames Creek 700 m 31 August 1991 T. Goward 91-1392
10. Kispiox area 510 m 19 July 1992 T. Goward
11. Azure Lake 650 m 5 August 1992 T. Goward
12. Upper Fraser Rivernorth of McBride, Slim Creek 750 m 17 August 1992 T. Goward 92-1224
13. Upper Fraser Rivernorth of McBride 800 m 17 August 1992 T. Goward 92-1246
14. Upper Fraser Rivernorth of McBride 750 m 17 August 1992 T. Goward 92-1210
15. Upper Fraser Rivernorth of McBride 800 m 18 August 1992 T. Goward 92-1305
16. Chilliwack Lakearea 650 m 25 August 1992 T. Goward
17. Murtle Lake 1100 m 9 September 1992 T. Goward 92-1396
18. Murtle Lake 1170 m 10 September 1992 T. Goward
19. Upper Adams River 900 m 17 September 1992 T. Goward 92-1432
20. Upper Adams River 700 m 22 September 1992 T. Goward 92-1474
21. Upper Adams River 750 m 23 September 1992 T. Goward 92-1516
22. Robson Valley 875 m 4 June 1995 T. Goward 95-99a
23. Kispiox area, near Carrigan Creek 785 m 2 July 1995 T. Goward 95-228
24. Kispiox area, near Skeena River 745 m 3 July 1995 T. Goward 95-300
25. Kispiox area, near Helen  Lake 550 m 4 July 1995 T. Goward 95-390
26. Cranberry Junction, near Octopus Lake 680 m 4 July 1995 T. Goward 95-399
27. White Swan Lakearea 515 m 5 July 1995 T. Goward 95-450
28. Cranberry Junction, near Octopus Lake 680 m 4 July 1995 T. Goward 95-399
29. Meziadin Lakearea 660 m 6 July 1995 T. Goward 95-457
30. Meziadin Lakearea. 650 m 7 July 1995 T. Goward 95-530
31. Mt. Bell-Irving area 445 m 8 July 1995 T. Goward 95-576
32. Hazelton area 645 m 9 July 1995 T. Goward 95-605
33. Seymour Rivernear Blais Creek 875 m 7 August 1995 T. Goward 95-831
34. Seven Sisters area 240 m 21 June 1996 T. Goward 96-47
35. Cummins River Valley 825 m 23 July 1997 T. Goward 17792
36. Selkirk Mountains, along Incomappleux River, near confluence with Battle Brook ca 600-50 m 14 September 2002 T. Spribille 12293
37. Selkirk Mountains, near upper end of Duncan Lake, along Hall Creek just above confluence with Duncan River, just above main upper forestry Duncan Road ca 690 m 15 September 2002 T. Spribille 12418
38. Kispiox area, Date Creek Forest Service Road, 1200 Branch 664 m 23 September 2004 P. Williston 4686
39. Kispiox area, Date Creek Forest Service Road, near interpretive parking area 487 m 23 September 2004 P. Williston
40. Kispiox area, Date Creek Forest Service Road, creek at Km 19 528 m 23 September 2004 P. Williston
41. Kispiox area, Botrychium Basin Sensitive Area, Date Creek Forest Service Road 537 m 23 September 2004 P. Williston 4702, 4719
42. Kispiox area, Helen Lake Forest Service Road 496 m 24 September 2004 P. Williston 4722
43. Kispiox area, Helen Lake Forest Service Road 505 m 24 September 2004 P. Williston 4715
44. Kispiox area, Helen Lake Forest Service Road ca 500 m 24 September 2004 P. Williston
45. Kispiox area, Helen Lake Forest Service Road ca 500 m 24 September 2004 P. Williston 4707

Rescue effect

In the event of extirpation, Canadian populations would not likely benefit from the rescue effect (immigration from an outside source) for three reasons: 1) Canadian populations (particularly inland localities) are spatially distant from neighbouring populations in the United States; 2) populations in neighbouring states are few in number (Alaska has 6 and Washington 8); and 3) Nephroma occultum is recognized as having poor dispersal capabilities.

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