A general framework for effectiveness concepts in mutualisms

Abstract

A core interest in studies of mutualistic interactions is the 'effectiveness' of mutualists in providing benefits to their partners. In plant-animal mutualisms it is widely accepted that the total effect of a mutualist on its partner is estimated as (1) a 'quantity' component multiplied by (2) a 'quality' component, although the meanings of 'effectiveness,' 'quantity,' and 'quality' and which terms are applied to these metrics vary greatly across studies. In addition, a similar quantity 9 quality = total effect approach has not been applied to other types of mutualisms, although it could be informative. Lastly, when a total effect approach has been applied, it has invariably been from a phytocentric perspective, focussing on the effects of animal mutualists on their plant partner. This lack of a common framework of 'effectiveness' of mutualistic interactions limits generalisation and the development of a broader understanding of the ecology and evolution of mutualisms. In this paper, we propose a general framework and demonstrate its utility by applying it to both partners in five different types of mutualisms: pollination, seed dispersal, plant protection, rhizobial, and mycorrhizal mutualisms. We then briefly discuss the flexibility of the framework, potential limitations, and relationship to other approaches.

The timing of frugivore‐mediated seed dispersal effectiveness

“…We also calculated the overall effectiveness across periods (SDE ik = Qt ik × Ql k ), where Qt ik is the sum of Qt ijk across periods for each “bird species group–microhabitat” combination, and Ql k is the weighted mean of Ql jk across periods (weighted by Qt ijk ); the reason for weighting is that the cumulative probabilities of recruitment represented by Ql jk were associated with different fractions of seeds arriving to each microhabitat. We used the package effect.lndscp (v. 0.2.8) (by P. Jordano; see Schupp et al., ) to represent “quantity × quality” effectiveness landscapes.…”

“…Mutualistic interactions constitute an essential element of biodiversity that provides key ecological functions, from mycorrhizal‐mediated mineral nutrition to animal‐mediated pollination and seed dispersal (Jordano, ; Schupp, Jordano, & Gómez, ). A major challenge in understanding the role of mutualistic interactions in community dynamics lies in assessing not only the immediate outcome , but also the delayed effect that interacting species have on their partners (Schupp et al., ). The immediate outcome is the successful occurrence of interactions and can be largely assessed as a quantity component (number of events; for example, number of seeds dispersed).…”

“…The delayed outcome is the “per capita” effect a species has on the demography of its interacting partner and can be assessed as a quality component (e.g., probability of recruitment of a dispersed seed). This framework allows the total effect of interactions to be estimated for both sides of the mutualism as the product of quantity and quality (quantity × quality), which results in a measure of effectiveness (Schupp et al., ).…”

Diet complementation as a frequency‐dependent mechanism conferring advantages to rare plants via dispersal

“…The spatial configuration of the seed rain then serves as the template for positive density‐dependent mortality effects when generating a community of seedlings. Our main model outputs are seed dispersal effectiveness of focal species (SDE, number of seeds dispersed x probability of postdispersal survival; Schupp et al., ) and resource provisioning effectiveness of foraging birds (RPE, number of fruits consumed x energy gain per gram of fruit consumed; Schupp, Jordano, & Gómez, ).…”

Does beak size predict the pollination performance of hummingbirds at long and tubular flowers? A case study of a Neotropical spiral ginger

“…The hummingbird‐pollinated system of C. spiralis does not appear to depend on the matching of its morphological characteristics with the behavioral traits of either trochilines or phaethornithines, factors which would be expected to interfere with the effectiveness of an interactive network (Bartomeus et al ., ). Our results indicate that the effectiveness of the pollinators – that is, the total contribution of the pollinator to the plant's fitness (Schupp, Jordano & Gómez, ) – may be mediated more closely by the abundance of pollinators (hummingbirds) than the compatibility of the trait‐matching. These novel results provide important insights for one of the core topics in the current debate on floral specialization (Thomson, ; Aguilar et al ., ; Ollerton et al ., ; Bartomeus et al ., ).…”