Meeting Abstract
28.3 Monday, Jan. 4 Life in leaf boundary layers: how two millimeters of still air affects the performance and ecology of small insects WOODS, H. A.*; POTTER, K. A.; Univ. of Montana; Univ. of Arizona art.woods@mso.umt.edu
An allometric claim: what we know about an animal’s environment scales to its body size with b > 1. That is, we know disproportionately a lot about environments around big things but astonishingly little about environments around small things; for a physiological ecologist, there is plenty of room at the bottom. Here we explore microenvironments occurring on leaf surfaces and ask: how do they affect the physiology and ecology of an insect herbivore, Manduca sexta? M. sexta are common in deserts of the southwestern United States, and females oviposit primarily on two host species, Datura wrightii and Proboscidea parviflora. Eggs develop for several days and produce neonates that hatch and begin to feed nearby. Eggs and neonates are small enough (project ~ 1 mm from the leaf surface) to be immersed in leaf boundary layers most of the time. Using custom-built, field-deployable computers equipped with small sensors, we logged temperatures and humidities in leaf boundary layers of several pairs of host plants near the Chiricahua Mountains, in southeast Arizona. Leaf surface conditions on the two host species were radically different both from ambient macro conditions and from one another: both host species provided cooler, wetter conditions than ambient air, but P. parviflora much more so than D. wrightii. In some cases, leaf temperatures of P. parviflora were 10 °C lower and vapor densities twice as high, compared to D. wrightii. Moreover, these biophysical differences translated into different amounts of water lost by eggs, which we showed by tracking masses of eggs glued onto host plants and control surfaces (paper) for 48 hours. Do these differences in water lost matter for egg performance? A series of lab experiments suggests that they do, but the outcome depends on the evolutionary history of the eggs and on host plant identity.
