Thermoregulatory abilities of Alaskan bees: effects of size, phylogeny and ecology

Abstract

Summary 1.The thermoregulatory capabilities of 18 species of Alaskan bees spanning nearly two orders of magnitude of body mass were measured. Thoracic temperature, measured across the temperature range at which each species forages, was regressed against operative (environmental) temperature to determine bees' abilities to maintain relatively constant thoracic temperatures across a range of operative temperatures (thermoregulatory performance). 2. Previous studies on insect thermoregulation have compared thoracic temperature with ambient air temperature. Operative temperature, which integrates air temperature, solar radiation and effects of wind, was estimated by measuring the temperature of a fresh, dead bee in the field environment. It is suggested that this is a more accurate measure of the thermal environment experienced by the insect and also allows direct comparisons of insects under different microclimate conditions, such as in sun and shade. 3. Simple regression analysis of species and family means, and analysis of phylogenetically based independent contrasts showed thermoregulatory capability, ability to elevate thoracic temperature, and minimum thoracic temperature necessary for initiating flight all increased with body size. 4. Bumble-bees were better thermoregulators than solitary bees primarily as a consequence of their larger body size. However, their thermoregulatory abilities were slightly, but significantly, better than predicted from body size alone, suggesting an added role of pelage and/or physiology. Large solitary bees were better thermoregulators than small solitary bees apparently as a result of body-size differences, with small bees acting as thermal conformers.

Can green roofs provide habitat for urban beeds (Hymenoptera: Apidae)?

“…Given their ability to fly long distances (Osborne et al 2008) and withstand cool temperatures and windy conditions (e.g. Bishop and Armbruster 1999), larger bees are expected to use suitable green roofs for foraging. Rarefaction curves also indicate there is likely a higher diversity of bees at both site types (Figure 2).…”

Temperature regulation in burying beetles (Nicrophorusspp.:Coleoptera: Silphidae): effects of body size, morphology and environmental temperature

“…We also measured hourly the operative temperatures of null temperature models placed in positions that represented other behaviors a beetle could adopt in response to its thermal environment: (1) on bare ground, 1-2·cm below the ground surface, and (2) beneath foliage (at the base of short grasses or under fresh leaves resting upon a soil substrate). Operative temperatures, also known as Te, take into account the effects of radiative and convective heat gain and loss in addition to ambient temperatures on the body temperature of a nonthermoregulating organism (Bakken, 1992;Heinrich, 1993) and more closely approximate the thermal environment that beetles actually experience (Bakken, 1992;Bishop and Armbruster, 1999). Differences between Te and actual body temperature (Tb) can indicate some form of thermoregulation by the animal (i.e.…”

“…We further investigated whether wing loading or body mass affected thermoregulatory ability, as well as whether the thermal environment influences the daily activity patterns of burying beetles. We assess thermoregulatory ability using two measures: (1) the relationship between thoracic temperature during flight and ambient temperature and (2) the relationship between thoracic temperature during flight and the effective (operative) temperature of a dead beetle in the flight position (index of thermoregulatory performance; Bishop and Armbruster, 1999). Additionally, we describe daily activity patterns for the three species over two 24-h observation periods and investigate how these patterns could be explained in part by the thermal environment that Nicrophorus experiences and by differential thermoregulatory abilities among species.…”

Metamorphosis is induced by food absence rather than a critical weight in the solitary bee,Osmia lignaria

“…For the reasons described above, bee size variation is expected to have a strong role in pollination efficacy of individuals and in the reproductive dynamics of pollinator populations. Many performance traits covary with body size and morphology, including better flight ability (43,44), vision (45), and thermoregulation (46,47). Larger bees typically gather more pollen in fewer trips to provision for their offspring, suggesting reproductive advantages.…”