A. Buse et al., Arthropod distribution on an alpine elevational gradient: the relationshipwith preferred temperature and cold tolerance, EUR J ENTOM, 98(3), 2001, pp. 301-309
The distribution of arthropod species on a 400 in elevational gradient (equ
ivalent to a temperature decrease of 2.5 degreesC) on Snowdon, North Wales,
was examined and compared with the British distribution. Preferred tempera
ture, an indication of optimal body temperature (T-b), and supercooling poi
nt (SCP), an indication of cold tolerance, of several species on the gradie
nt were determined experimentally. The alpine beetle species Patrobus assim
ilis and Nebria rufescens had low preferred T-b, of 5.6 and 7.1 degreesC re
spectively, whereas the more widespread upland species had higher preferred
T-b, between 12.9 and 15.5 degreesC. The SCP of both alpine and widespread
beetles were similar, being between -6.9 and -5.8 degreesC. The alpine spe
cies, which were smaller, were freeze intolerant, whereas the widespread sp
ecies, which were larger, were freeze tolerant. On the national scale there
was significant correlation between preferred T-b and species elevation, b
ut no correlation with SCP. It is concluded that the alpine species survive
on Snowdon because their optimal T-b is close to the ambient temperature a
t the time of day and year when they are active and because they are able t
o tolerate winter temperatures, by a combination of cold tolerance and shel
ter. Although a species' optimal niche will tend to shift upwards as mean t
emperatures rise with global climatic change, complex microclimatic and bio
tic factors make changes in distribution difficult to predict.