Tricholochmaea sablensis (Brown)

Tricholochmaea sablensis lateral habitus.

Introduction

Tricholochmaea sablensis (Brown) was described by Brown (1969) on the basis of specimens collected by several expeditions of personnel from the Canadian Entomology Research Institute on Sable Island, Nova Scotia, Canada in 1966 and 1967. The results of these expeditions are summarized in Howden (1970). To date, this has been the only known endemic species of beetle from Nova Scotia, although Klimaszewski and Majka are currently describing a second species in the genus Atheta (Staphylinidae: Aleocharinae).

Bionomics

They are members Tricholochmaea a diverse genus with several species which occur in Atlantic Canada including:

Tricholochmaea alni (Fall) - found on Alder (Alnus spp.).
Tricholochmaea cavicollis (LeConte) - on Cherry (Prunus spp.)
Tricholochmaea decorata decorata (Say) - ?
Tricholochmaea kalmiae (Fall) - found on Sheep Laurel (Kalmia angustifolia)
Tricholochmaea perplexa (Fall) - on Willow (Salix spp.)
Tricholochmaea sablensis (Brown) - on Cranberry (Vaccinium spp.)
Tricholochmaea spiraeae (Fall) - on Meadowsweet Spirea spp.
Tricholochmaea tuberculata (Say) - on Willow (Salix spp.)
Tricholochmaea vaccinii (Fall) - on Blueberry (Vaccinium spp.)

Each species has very specific requirements in terms of its host plant requirments.

Tricholochmaea sablensis dorsal habitus.

Evolutionary History

This species appears to be a post-glacial relict species. Various authors (see Bousfield and Thomas (1975), Howden et al. (1970), and Roland (1982)) have proposed discussed animals and plants which survived the Pleistocene glaciation in glacial refugia on the continental shelf, subsequently re-colonizing selected areas of the mainland after 11,000 years BP when the glaciers retreated. In some cases these represent species which currently have distributions further to the south of Atlantic Canada in New England. In the case of T. sablensis it appears that the population was isolated for a sufficiently long period of time for it to have evolved into a separate species.

Tricholochmaea sablensis on Sable Island

In 1966-67 they we're found on the bog cranberry (Vaccinmium macrocarpon) restricted to a cranberry bog near a small freshwater lake just east of the West Light. The lake, which had a salinity of 25 ppm was less saline than any of the surrounding lakes. Wright (1989) collecting on Sable Island in 1976-77 failed to find any on Sable Island and recent work in 2004 has also failed to turn up any specimens, casting some doubt on whether the species is still extant.

References

Bousfield, E.L. and M. L. H. Thomas. 1975. Postglacial change in distribution of littoral marine invertebrates in the Canadian Atlantic region. Proceedings of the Nova Scotia Institute of Science Supplement 3: 47-60.

Brown, W. J. 1969. A new species of Pyrrhalta from Sable Island (Coleoptera: Chrysomelidae). Canadian Entomologist 101: 109.

Howden, H.F., J.E.H. Martin, E.L. Bousfield, and D.E. McAllister. 1970. Fauna of Sable Island and its zoogeographic affinities - a compendium. National Museums of Canada, Publications in Zoology 4. 45 pp.

Roland, A.E. 1982. Geological Background and Physiography of Nova Scotia. Nova Scotian Institute of Science. Halifax, NS. 311 pp.

Wright, B.H. 1989. The Fauna of Sable Island. Nova Scotia Museum Curatorial Report 68. 93 pp.