Figure 1 – Contribution of each lemur genus to the overall cophylogenetic signal in (A) frugivory, (B) folivory, (C) florivory, and (D) granivory, measured as Procrustean residuals. Colors highlight differences among (1) feeding guilds and (2) activity pattern. Silhouettes were built by the authors. Procrustean residuals measure the variation in the topological fit that is not explained by the cophylogenetic structure of the interaction matrix. Interactions with small values contribute the most to CS, whereas those deviating more from the shared phylogenetic history contribute the less to CS.
To more accurately demonstrate coevolution, we also need evidence that phylogenetic distances and the dissimilarity between species in sets of interacting partners co-vary for both plants and lemurs (PSI). Contrary to our expectation of the existence of phylogenetic signal in species interactions for both plants and lemurs, we found that cophylogenetic patterns observed for frugivory, florivory and granivory emerged from similar lemurs (in terms of the between-species dissimilarities in sets of interacting partners) interacting with phylogenetic-related plants, with no reciprocal trend (i. e. plant diversification was unaffected by lemurs). In the case of folivory, however, phylogenetic congruence was associated with significant phylogenetic signals for both plants and lemurs. Nectarivores were the only group that did not show any evidence of PSI for either plants or lemurs (Table 2).
Although the observed cophylogenetic patterns for frugivory do not appear to reflect strong coevolution, we further investigated this possibility by taking advantage of the existence of functionally relevant morphological traits for both plants and lemurs. We found that, in addition to the congruence between plant and lemur phylogenies (significant CS), there was also congruence between lemur phylogeny and plant morphology, and between plant phylogeny and lemur morphology (Table 2). This result suggests that, to some extent, plant speciation shaped lemur morphology (notably body size), at the same time that lemur speciation somehow affected diaspore morphology (fruit and/or seed sizes).
Table 2 – Cophylogenetic signal (CS) and Phylogenetic signal in the interactions (PSI) between plants and lemurs