COS 189-4 - CANCELLED - The population dynamics of consumer-resource induced spatial patterns: insights from the demographics of the Turing mechanism

Background/Question/Methods

The Turing activator/inhibitor mechanism provides for a qualitative understanding of the self-organization of spatial patterns. In ecology, consumer-resource motifs provide a useful analogy to Turning’s conceptualization, with resources being activators and consumers inhibitors, both diffusing through space. Here we propose the existence of a demographic spatial pattern (DSP) that should be present in spatially clustered consumer-resource systems and structure trends in the demography of resource populations in space. The simple fact that resource populations diffuse spatially (dispersing locally) suggests the existence of a DSP where the oldest resources occur in the center of clusters and youngest on the edge. We show how focusing on the demographic spatial dynamics of the resource population can be used interrogate the spatial population dynamics of both resource (activator) and consumer (inhibitor). To understand this hypothesized fine-scale demographic structure of consumer-resource generated spatial patterns and their implications for the ecological dynamics, we couple a modeling approach with the well-studied consumer-resource system of a tree-nesting ant Azteca sericeasur, and its parasitoid predator, the phorid fly Pseudacteon spp. in a coffee agroecosystem.

Results/Conclusions

First, we develop a test derived from the hypothesized relationships among age classes of nests (resources) in space, and used 13 years of data on ant nest distributions from a 45ha plot to support the existence of a DSP. We then use age-specific mortality rates of the ant nests to show how the DSP structures interactions between the ants and their parasitoids. We find younger ant nests have higher age-specific mortality which corresponds the assumptions of the DSP where youngest nests are the periphery of clusters and should be attacked at higher rates than older nest at the center of clusters. The trend in age-specific mortality is corroborated from field surveys on the arrival time and attack rate of parasitoids on different aged nests. To explore the generality of DSP in pattern forming systems, we then utilize a simple spatially explicit consumer-resource model to illustrate how diffusion rates of both consumers and resources structure the underlying DSP of resource populations and in turn influence trends in the age-specific mortality. Finally, we show how age-specific mortality driven by DSP at the scale of individual clusters influences the large-scale spatial pattern of the whole system.