O. Totland, INFLUENCE OF CLIMATE, TIME OF DAY AND SEASON, AND FLOWER DENSITY ON INSECT FLOWER VISITATION IN ALPINE NORWAY, Arctic and alpine research, 26(1), 1994, pp. 66-71
This study examines the influence of environmental factors (temperatur
e, light intensity, wind speed, time of day and flowering season, and
flower density) on flower visitation activity of insects in a middle a
lpine area in southwestern Norway. Data were obtained by measuring the
environmental factors and simultaneously observing the visitation act
ivity to flowers within squares (1 x 1 m) for 10-min periods. Flies (D
iptera) were the only flower visitors. In a simple linear regression a
nalysis, mean daily temperature best explained the variation in mean d
aily visitation activity within the squares (R2 = 0.66). R2 increased
to 0.74 in a multiple regression with all factors included. An unimoda
l progression in visitation activity was measured through the day, wit
h peak visitation at 1200 h (solar time). Visitation activity was high
est early in the flowering season (early July) and decreased as the se
ason progressed (R2 = 0.21). Visitation was positively correlated with
the daily mean flower density (R2 = 0.18). The flower density of indi
vidual species also affected visitation activity. Visitation reached a
maximum level at medium flower densities, whereafter it stabilized, s
uggesting that the local visitor pool was saturated. The relationship
between visitation activity and environmental factors at Finse, Norway
, is similar to that found in alpine U.S.A., Chile, and Australia.