Abstract
In order to explore biotic attraction to structure, we examined how the amount and arrangement of artificial biotic stalks affected responses of a shrimp, Palaemon macrodactylus, absent other proximate factors such as predation or interspecific competition. In aquaria, we tested the effect of differing densities of both un-branched and branched stalks, where the amount of material in the branched stalk equaled four-times that of the un-branched. The results clearly showed that it was the amount of material, not how it was arranged, that elicited responses from shrimp. Also, although stalks were not purposefully designed to mimic structural elements found in nature, they did resemble biogenic structure such as hydroids, algae, or plants. In order to test shrimp attraction to a different, perhaps more unfamiliar habitat type, we examined responses to plastic “army men.” These structural elements elicited similar attraction of shrimp, and, in general, shrimp response correlated well with the fractal dimension of both stalks and army men. Overall, these results indicate that attraction to physical structure, regardless of its nature, may be an important driver of high abundances often associated with complex habitats.
Highlights
The physical nature of habitats profoundly shapes resident biotic assemblages
The goal of our work was to examine how the complexity and density of structural elements would drive behavioral responses of P. macrodactylus, while controlling for other proximate factors which might drive shrimp response. This consisted of two experiments, one where shrimp could choose between arrays of structural elements in different configurations, and the other where we examined the response to a single array to assess the degree to which habitat complexity, as assessed with total surface area and fractal dimension, could account for position of shrimp in experimental tanks
For the stalk treatments, it is important to note that the amount of material was very closely related to the fractal dimension of the arrays. These experiments demonstrate that shrimp responded to the presence of structure in the absence of proximate factors such as predation pressure and food supply, and that an excellent predictor of shrimp location was the amount of material available
Summary
Habitatspecies relationships underpin basic ecological dynamics (McCoy & Bell, 1991; Matias et al, 2010; Tokeshi & Arakaki, 2012), and have implications for ecosystem management, conservation, and restoration (e.g., Crooks, 2002; Jimenez & Conover, 2001; Thrush & Dayton, 2002; Byers et al, 2006; St. Pierre & Kovalenko, 2014; Loke et al, 2014). Despite (or perhaps because of) the ubiquity and importance of habitat-species interactions, there are considerable conceptual and terminological issues associated with even the most fundamental aspects of habitat structure (Matias, Underwood & Coleman, 2007; Tokeshi & Arakaki, 2012; Kovalenko, Thomaz & Warfe, 2012; Loke et al, 2014).
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