Climatic control of trophic interaction strength: the effect of lizards on spiders

Abstract

We investigated how temporal variation in rainfall influences the impact of lizards on spiders inhabiting small islands in Abaco, Bahamas. Annual censuses of web spiders were conducted on nine lizard islands and on eight no-lizard islands 1994-2003. Repeated-measures ANOVA showed that annual variation in spider density (time) and in the lizard effect on spider density (lizard x time) were both significant. Correlation coefficients between the lizard effect (ln ratio of no-lizard to lizard spider densities) and number of rainfall days were generally negative, and strengthened with length of the time period during which rainfall was measured prior to annual spider censuses. Spider density was also negatively correlated with rainfall days and strengthened with length of the prior time period. Longer time intervals included the hurricane season, suggesting that the strong negative correlations were linked to high rainfall years during which tropical storms impacted the region and reduced spider and lizard densities. Split-plot ANOVA showed that rainfall during the hurricane season had a significant effect on the lizard effect and on spider density. Results in this study are opposite to those found in our previous 10-year study (1981-1990) conducted in the Exuma Cays, a moderately xeric region of the Bahamas, where the relation between rainfall and the lizard effect on spider density was positive. Combined data from the Exuma and Abaco studies produce a unimodal relation between trophic interaction strength and rainfall; we suggest that the negative effect of storms associated with rainfall was paramount in the present study, whereas the positive bottom-up effect of rainfall prevailed in our previous study. We conclude that climatic variability has a major impact on the trophic interaction and suggest that a substantial change in precipitation in either direction may weaken the interaction significantly.

Plant community composition determines the strength of top-down control in a soil food web motif

“…Our results support the hypothesis of increased trophic control of prey by predators as productivity increases829. Furthermore, our results show interactive effects of predator density and productivity co-determining changes in prey populations.…”

Animal water balance drives top-down effects in a riparian forest—implications for terrestrial trophic cascades

“…'fear') [28 -31]. Previous research suggests that the magnitude of top-down effects may be influenced by consumer size and metabolic rate, the existence of plant defences, the diversity of herbivores, the choice of plant response metric and environmental conditions such as solar radiation, temperature, rainfall or disturbance [5,26,27,32,33]. Additionally, traitmediated indirect interactions, like anti-predator behaviour, often play a large role in driving these cascades [28,29,31,34], with the strength of these effects, relative to density-mediated indirect interactions (direct consumption), probably driven by predator hunting modality (i.e.…”

Predators determine how weather affects the spatial niche of lizard prey: exploring niche dynamics at a fine scale

“…Anolis sagrei and L. carinatus are similar in habitat use: A. sagrei is one of the most terrestrial anoles (Schoener 1968) and L. carinatus spends most of its time on the ground (Schoener 1975); the latter is known to consume the former (Schoener et al 1982) and A. sagrei greatly modifies its space use in the presence of L. carinatus (Schoener et al 2002, Losos et al 2004, 2006. Because the effect of A. sagrei on spider abundance is related to rainfall (in drier times these lizards may respond to desiccation by spending less time foraging [Spiller and Schoener 2008]), the response of A. sagrei to microclimatic factors could also affect the interaction with its predator. Hence, exploring the Leiocephalus-Anolis interaction under different environmental conditions should increase our knowledge of what processes control fine-scale adjustments in niche use.…”