Spatial behavior: the impact of global and local geometry.

Humans and other animals use the global geometry of the surrounding environment in order to orient and determine which direction they are facing. Accordingly, the impact of environment geometry on spatial behavior is reflected in the paths of progression in the environment. When the perception of the global geometry is limited, such as in large or dark environments, the global geometry of the environment has to be constructed gradually as the accumulated geometry of locales. In the present study, we progressively altered the form of a dark square test arena by means of local alterations to its corners and walls, in order to differentiate the impact of the global arena geometry from that of the local arena geometry sectors on spatial behavior in rats. We found that as long as the local alterations did not distort the global square geometry of the dark environment, the rats' behavior did not significantly change. In contrast, distortion of the square shape of the arena resulted in significant changes in the spatial distribution of the rats' activity. Accordingly, we suggest that the perceived global geometry affects spatial behavior, overriding the impact of the local geometry.

Phenotypic plasticity and variation in morphological and life-history traits of antlion adults across a climatic gradient.

We report here on two complementary experiments examining the effect of climate on morphological and life-history traits of antlion adults. We first examined whether body size and wing loading of emerging adults are plastic by raising larvae, collected from five antlion populations along Israel's sharp climatic gradient, in two environmental chambers simulating temperature and humidity of desert and Mediterranean climates. The variance in adult morphology was mostly related to body size, with adults of Mediterranean populations being larger than those of desert populations. Wing-to-thorax ratio was negatively correlated with temperature, compensating for the decrease in wing-beat frequency in colder environments. Differences between climatic treatments were significant for body size but not for the wing-to-thorax ratio, suggesting that body size is more plastic than the ratio between different body components. We next investigated how the exposure of antlion pupae to different climatic conditions influences the emerging adults. Adult body mass increased with final larval body mass at a faster rate when exposed to Mediterranean rather than desert conditions. Duration of the pupa stage was positively correlated with final larval mass, but only under Mediterranean conditions. Adult survival increased with initial mass (after eclosion), but was lower under desert conditions. Similarly, adults lost mass at a faster rate when exposed to desert conditions. Notably, the exposure of the pupae to varying climatic conditions had no effect on adult morphology. Climate is a major factor affecting insect life span and body size. Since body size is strongly linked to fecundity and survival, climate thus has a twofold effect on fitness: directly, and indirectly through body size.