Abstract
Interactions among members of biological communities can create spatial patterns that effectively generate habitat heterogeneity for other members in the community, and this heterogeneity might be crucial for their persistence. For example, stage-dependent vulnerability of a predatory lady beetle to aggression of the ant, Azteca instabilis, creates two habitat types that are utilized differently by the immature and adult life stages of the beetle. Due to a mutualistic association between A. instabilis and the hemipteran Coccus viridis – which is A. orbigera main prey in the area – only plants around ant nests have high C. viridis populations. Here, we report on a series of surveys at three different scales aimed at detecting how the presence and clustered distribution of ant nests affect the distribution of the different life stages of this predatory lady beetle in a coffee farm in Chiapas, Mexico. Both beetle adults and larvae were more abundant in areas with ant nests, but adults were restricted to the peripheries of highest ant activity and outside the reach of coffee bushes containing the highest densities of lady beetle larvae. The abundance of adult beetles located around trees with ants increased with the size of the ant nest clusters but the relationship is not significant for larvae. Thus, we suggest that A. orbigera undergoes an ontogenetic niche shift, not through shifting prey species, but through stage-specific vulnerability differences against a competitor that renders areas of abundant prey populations inaccessible for adults but not for larvae. Together with evidence presented elsewhere, this study shows how an important predator is not only dependent on the existence of two qualitatively distinct habitat types, but also on the spatial distribution of these habitats. We suggest that this dependency arises due to the different responses that the predator's life stages have to this emergent spatial pattern.
Highlights
The vast majority of animal communities are not randomly distributed
There is abundant research that shows that habitat heterogeneity promotes persistence of otherwise unstable systems, for example consumer–resource interactions (Bailey et al 1962; Hassell and May 1974; Hassell et al 1991; Bonsall et al 2002), we know little how stage-structured predator populations, whose life stages have variable responses to different habitat types, are affected by a heterogeneous environment
Ecology and Evolution published by John Wiley & Sons Ltd
Summary
The vast majority of animal communities are not randomly distributed. Rather they tend to have uniform, clustered, or patchy distributions, and the question of how these patterns emerge, as well as the consequences of their existence, is an exciting topic in ecological research. There is abundant research that shows that habitat heterogeneity promotes persistence of otherwise unstable systems, for example consumer–resource interactions (Bailey et al 1962; Hassell and May 1974; Hassell et al 1991; Bonsall et al 2002), we know little how stage-structured predator populations, whose life stages have variable responses to different habitat types, are affected by a heterogeneous environment.
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