The effect of water on the ground nesting habits of the giant tropical ant, Paraponera clavata
Abstract The large predatory ant, Paraponera clavata, exerts measurable top-down effects in wet and moist Neotropical forests, and therefore its distribution has potential ecological implications. To determine how water affects the presence of this important predator, the ground nesting ecology of P. clavata was examined with respect to various habitat characteristics. Four hectares of disturbed Costa Rican lowland rain forest were surveyed for ant colonies to determine nest distribution patterns in wet and dry habitat; significantly more colonies were found in dry habitat. Seventeen of 19 nests built on slopes of > 5° inclination were positioned on the downward side of the tree, possibly using the trunk as a shield against runoff during rain showers. Moisture and pH inside nests were significantly different from adjacent soil. These results suggest that water influences the ground nesting habits of P. clavata, thus ecological differences between comparatively wet and dry portions of tropical forests may arise from the relative abundance of this ant species.
Desiccation resistance in arboreal and terrestrial ants
ABSTRACT Arboreal and terrestrial ants were exposed to 0, 25, 50, 75 and 100 (control)% r.h., at 30oC. Desiccation resistance increased with body size (as dry weight0.55), but not as quickly as expected from the consequences of the surface area and volume relationship (as dry weight0.67). Arboreal ants took 8 times longer to die than terrestrial ants of comparable size. Even after size effects were removed, desiccation resistance differed between various terrestrial species and showed a correlation with foraging patterns.
Computer simulations and theory of oceanographic fluorescence lidar signals: effect of sea surface structure.
A 3-D computer simulation model has been developed using geometrical optics suitable for analyzing the effect of sea surface structure on oceanographic fluorescence lidar signals. Depth-resolved and depth-integrated signals reveal a considerable dependence on the surface structure. The results obtained by simulation are confirmed by a theoretical approach based on the transformation of solid angles by curved boundaries. Using statistical assumptions about the distribution of curvatures of the ocean surface, a general expression for this influence is found.