Phylogenetic community ecology needs to take positive interactions into account

Abstract

Phylogenetic community ecology uses phylogenetic relationships among species to infer the dominant processes that shape community ecological structure. This field has particularly focused on habitat filtering and competition, the latter driving divergence and competitive exclusion. However, the effects of positive interactions among species of the same guild have rarely been considered in either empirical studies or theoretical models. We have recently documented a pervasive influence of mutualism in driving adaptive convergence in ecological niche. Müllerian mimicry in butterflies is one of the best studied examples of mutualism, where unpalatable species converge in wing pattern locally to advertise their toxicity to predators. We showed that species that share similar wing patterns are more similar in their ecology than expected given the phylogeny and co-exist at a fine spatial scale, thereby maximizing the warning signal to local predators. Evidence for competition was detected only among species with distinct wing patterns, implying that mutualistic interactions outweigh the effects competition.  Positive interactions among potential competitors are common among plants and animals. We argue that such forces should be considered in the field of phylogenetic community ecology, alongside neutral processes, habitat filtering and competition.

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Acknowledgements

We thank Olivier Hardy and Cam Webb for useful comments on this paper.

Figures and Tables

Figure 1 The eight mimicry rings of the study community, illustrated by several species (eurimedia: Ithomia salapia, Pteronymia primula, Napeogenes inachia; hermias: Tithorea harmonia, Mechanitis polymnia, Melinaea satevis; lerida: Oleria gunilla, O. onega, Hyposcada illinissa; aureliana: Pseudoscada florula, Napeogenes sylphis, Hypoleria lavinia; agnosia: I. agnosia, Heterosais nephele, Pseudoscada timna; mamercus: Hypothyris mamercus, N. larina, H. moebiusi; confusa: Methona confusa, M. curvifascia, Callithomia lenea; mothone: Melinaea marsaeus, Mechanitis messenoides). Species with transparent wings are presented against a dark background.

Figure 2 Relationships between phylogenetic and ecological distances, and mimicry. (A) Mean and standard error of phylogenetic distances among co-mimics and non-co-mimics. (B) Multidimensional ecological distances (Euclidean distances in the 5-dimension space formed by the five ecological variables measured) plotted against phylogenetic distances for all species, showing the correlation coefficient r and significance p (Mantel test). (C) Multidimensional ecological distances plotted against phylogenetic distances for co-mimics and non-co-mimics. Ecological distances observed among co-mimics are smaller than expected given the phylogeny (method controlling for phylogeny based on simulations: p = 0.030; method based on regression p < 0.0001), while ecological distances among non-co-mimics are greater that expected given the phylogeny (method based on simulations: p = 0.0013; method based on regression p = 0.0012).

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