Shaw, D.P. and M. Davis. 2000. Invertebrates from caves on Vancouver Island. pp.121-124 IN: Darling, L. (ed) Proceedings of a conference on the biology and management of species and habitats at risk, Kamloops, BC 15-19 Feb 1999. B.C. Ministry of Environment, Lands and Parks, Victoria, B.C. and University College of the Cariboo, Kamloops, B.C. 490pp.

Patrick Shaw and Martin Davis

Casual observation and collection of invertebrates in caves on Vancouver Island has been conducted since the early 1960s. Two comprehensive and systematic surveys have been carried out; one in the 7 caves of Horne Lake Caves Park in 1986 and a second in 1997 which covered 15 caves of a wider geographic area on the island. A total of 192 taxa have been identified to date, including a number of new species, records or rare species.

INTRODUCTION

The fauna of caves in Canada is quite poorly known. Until recently, it was presumed that the active glacial history in Canada would have led to the extirpation of any obligate troglobites. As such, the present cave fauna would have immigrated from source areas beyond the southern ice limit.

Collections and discoveries in cave areas in the Rockies (Zacharada and Pugsley 1988 , Holsinger 1980 , Bousfield and Holsinger 1981), on Vancouver Island (Holsinger and Shaw 1988) and on Prince of Wales Island, Alaska (Carlson 1995) have proven this not to be the case. However, systematic studies of cave invertebrate communities in Canada have been only rarely conducted (Peck 1988), and the composition of the subterranean fauna in most areas of the country remains relatively unknown. Scudder and Cannings (1994) recognized this lack, and identified caves as a priority for invertebrate inventory.

The composition of cave faunas on Vancouver Island are now relatively well studied compared to other karst areas in Canada. In addition to sporadic collections, 2 concerted studies of cave biota have been conducted. The first was a summer/winter survey of seven caves in Horne Lake Caves Park in 1986. A second survey conducted in during summer and fall of 1997 covered a variety of caves in 3 areas of the island. These covered a range of lengths, elevations and settings but were a tiny sub-set of the potential locations for study. Some preliminary observations are presented here as an introduction to the biology of west-coast caves, with a more complete assessment in preparation.

METHODS

General locations of the surveyed cave systems are shown in Figure 1. Efforts were made to cover a range of both cave size, elevation and geographic locales with collections at regular to semi-regular intervals throughout systems. Field collections used a wide variety of techniques. Careful visual searches with aspirators and brushes. Pitfall traps baited with a variety of attractants, and set for 3-10 days were important in the surveys. Aquatic fauna were collected by searching, surber samplers and drift net sets. Some surface springs were also sampled

RESULTS

• A total of 191 taxa have been identified in collections thus far, including a minimum of 10 new species
• The highest diversity occurs in the entrance area, and the composition is dominated by taxa which would likely be found elsewhere in similar surface environments with conditions such as low-light, high humidity (Figure 2). Near-entrance fauna was dominated by a variety of diptera, and associated predators such as aranae and coleptera
• In deep-cave habitats, collections were dominated by collembola, symphyla and diplura with infrequent captures of other taxa, such as acarina (Robustocheles occulta), diptera or siphonaptera.
• At the order and family level, the composition of fauna caves on Vancouver Island is similar to that found elsewhere in North America (Holsinger and Culver ). In particular, similarities even at the species level between Vancouver Island collections and similar sites in southeast Alaska are remarkable.
• Few endemic troglobites have been found to date in the collections, however many taxa are currently identified to genus or higher levels, and closer examination may yield further discoveries. This is particularly true of the diptera, for which new species are certain, even in the present collections.
• Of particular interest in the collections have been the crustacea, with two certain troglobites known.

Composition of Collections

The general composition of the collections is shown in Figure 3.

Coleptera

Total of 37 species have been identified in the collections. The majority (19 species) belonged to the Staphylinidae, a family of mostly predatory beetles. The next largest group (10 species) are the ground beetles (the Carabidae), common in forest habitats in moist, dark places.

Arachnida

The collections includes 17 species of Aranae, 10 Opilionid species of 1 identified predatory acarine (Robustocheles occulta). Nearly all are probable troglophiles/ trogloxenes. One common opilionid (Nelima paessleri) overwinters in dense hibernating aggregations in mines and caves (Holmberg et al. 1984). The acarine diversity in the collection is grossly underestimated since none of the aquatic taxa have yet been identified.

Collembola

Total of 20 taxa; many still to be identified to species. Collembola are the most common component of the deep-cave habitats. Several may be obligate troglobites; species of the genus Arrhopalites in particular.

Plecoptera/Ephemeroptera/Trichoptera

These orders were represented by a total of 25 species, mostly as aquatic larvae. All of the "EPT" taxa are probably all "accidentals" which wash into the cave through surface streams.

Siphonaptera

Total of 7 species have been collected underground. Most are parasites of wood mice (Peromyscus spp.) which make extended excursions into caves, and were attracted to pitfall trap sets. One species collected from Myotis spp. during bat studies.

Crustacea

Two troglobites; the amphipod Stygobromus quatsinensis (Holsinger and Shaw, 1988) and an undescribed bathynellid of the genus Pacificabathynella. Collections have shown that S. quatsinensis is widely distributed on Vancouver Island, and, suprisingly, has been recently collected from cave habitats in the offshore islands of SE Alaska (Carlson, 1995). In addition, there are several probable new copepod species in the genus Acanthocyclops.

Diptera

A total of 50 taxa have been collected, many of which have as yet been identified only to genus. In the collections is a particularly strong dominance (19 taxa) of Mycetophilidae and closely related families. One mycetophilid genus alone (Speolepta) is probably represented by 2-3 undescribed species (Borkent, pers. comm.). A key discovery in 1997 was that of an extremely rare simuliid ( Parasimulium meleanderi; Borkent and Currie, in prep) which probably has a groundwater dwelling larva. Most species are, apparently, restricted to the entrance to twilight areas. There are probably few true troglobites, although study of the life-history of some of the mycetophilids would probably yield some important information.

Other Taxa

Amongst the remaining 15 taxa are representatives of 10 orders or phyla. Two species of common lepidoptera (Triphosa haesitata, Scoliopteryx libatrix) are represented, a species of symphyla, 3+ species of aquatic oligochaetes. At least 4 species of millipeds were collected, including two new species of Conotylidae (Shear, pers comm).

CLOSING REMARKS AND RECOMMENDATIONS

• These are very preliminary studies, and the observations thus far are suggestive of the potential for further discoveries.
• Collections thus far have focussed on coastal karst, and there needs to be further (or similar) effort in karstic terrains elsewhere in British Columbia, and Canada.
• Both high endemicity and extreme scarcity of some fauna collected in caves on Vancouver Island (such as P. meleanderi) may be a function of collection effort, and additional collections need be done to establish the full geographic and extent of many of these species
• Surface environs in karst areas, particularly in coastal areas, are subject to massive change through timber harvesting. While this probably affects most strongly the entrance zone, particularly with respect to humidity and temperature regimes, the influence may extend deep into the cave through water flow and evapotranspiration changes. Careful environment and faunal studies of caves before and after timber harvest could assess the effect of these changes
• There is a surprisingly high faunal similarity between cave taxa collected on Vancouver Island and in similar environs on coastal islands in Alaska. Genetic studies of local populations on Vancouver Island and Alaska (and probably the Queen Charlotte Island) populations would establish the time of dispersal, and provide important information on colonization of offshore islands.

LITERATURE CITED

Bousfield, E.L. and J.R. Holsinger. 1981. A second new subterranean amphipod crustacean of the genus Stygobromus (Crangonyctidae) from Alberta, Canada. Canadian Journal of Zoology 59:1827-1830

Carlson, K.E. 1995. Inventory and assessment of ecological relationships between cavernicolous (cave-associated) invertebrate species and their interactions in representative karst ecosystems on carbonate terrain in the Ketchican Area Tongas National Forest. Unpublished report to U.S. Forest Service, Alaska. 60 pp +App.

Holmberg, R.G., N.P.D. Angerilli and L.J. LaCasse. 1984. Overwintering aggregartions of Leiobunum paessleri in caves and mines (Arachnida, Opiliones). Journal of Ararchnology 12:195-204

Holsinger, J.R. 1980. Stygobromus canadensis, a new subterranean amphipod crustacean (Crangonyctidae) from Canada, with remarks on Wisconsin refugia. Canadian Journal of Zoology 58:290-297

Holsinger, J.R. and D.P. Shaw. 1988. Stygobromus quatsinensis, a new amphipod crustacean (Crangonyctidae) from caves on Vancouver Island. Canadian Journal of Zoology 65: 2002-2009

Holsinger, J.R. and D.C. Culver. 1988. The invertebrate cave fauna of Virginia and a part of eastern Tennessee: zoogeography and ecology. Brimleyana 14: 1-162

Peck, S.B. 1988. A review of the cave invertebrate fauna of Canada, and the composition of the invertebrate fauna of caves and mine in Ontario. Canadian Journal of Zoology 66:1197-1213

Scudder, G. G. and S. Cannings. 1994. British Columbia terrestrial and freshwater invertebrates: inventory priorities for and status of rare and endangered species. British Columbia Conservation Data Centre. 8 pp.

Zacharada, M. and C.W. Pugsley. 1988. Robustocheles occulta sp. n. A new troglobitic mite from North American caves. Canadian Journal of Zoology 66: 646-650

Acknowledgements

Special thanks to the many enthusiastic cavers who volunteered both their time and inspiration during field work. A special thanks to Alisa Vanderberg who was instrumental in the 1997 collections. Their support was and will continue to be invaluable. Many taxonomists contributed their expertise to this work. In particular, Dr. Art Borkent (Royal BC Museum Associate), Dr. Jan Klimachewski, Dr. Ken Christiansen (Grinnel College, Ohio), Rod Crawford (Burke Museum, University of Washington), Dr. Bill Shear (Hampden-Sydney College), Dr. Steve Marshall (Guelph University), Dr. Robert Holmberg (Athabasca University), Dr. Frank Radovsky (Oregon State University), Dr Matthias Buck (Guelph University), Pam Dymond (University of British Columbia), Laura Rempel (University of British Columbia) are particularly thanked. Theirs is a seriously undervalued and essential skill in the proper assessment of biodiversity. This work was supported by funds from BC Parks (1986) and from the BC Conservation Data Centre (1997).

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