Strength Of Mutualistic Interactions Research Articles

Morphological trait-matching in plant-Hymenoptera and plant-Diptera mutualisms across an elevational gradient.

Morphological trait-matching and species abundance are thought to be the main factors affecting the frequency and strength of mutualistic interactions. However, the relative importance of trait-matching and species abundance in shaping species interactions across environmental gradients remains poorly understood, especially for plant-insect mutualisms involving generalist species. Here, we characterised variation in species and trait composition and the relative importance of trait-matching and species abundance in shaping plant-Hymenoptera and plant-Diptera mutualisms in four meadows across an elevational gradient (2,725-3,910m) in Yulong Snow Mountain, Southwest China. We also evaluated the effects of morphological traits of flower visitors and plant composition on their foraging specialisation (d' and normalised degree). There was a high degree of dissimilarity in the composition of Hymenoptera and Diptera visitors and their visited plants between communities. This variation was mainly driven by the spatial replacement of species. Both for plant-Hymenoptera and plant-Diptera networks, trait-matching between nectar tube depth and proboscis length was a stronger predictor of the interactions between temporally co-occurring plants and flower visitors than species abundance. Fourth-corner analyses revealed statistically significant trait-matching between nectar tube depth and proboscis length in plant-Hymenoptera networks at all sites, suggesting that Hymenoptera consistently foraged on plant species with nectar tube depths matching their proboscis lengths. By contrast, significant trait-matching in plant-Diptera networks was only observed at the two lower elevation sites. The species-level specialisation d' of flower visitors increased significantly as the proboscis length and the difference in nectar tube depth between the plant community and the plants visited by flower visitors increased. Our results highlight that the importance of trait-matching in shaping pairwise interactions and niche partitioning depends on the specific features (e.g. species composition and trait availability) of the plant-pollinator system. For specialised plant-Hymenoptera systems, trait-matching is an important determinant of species interactions, whereas for generalist plant-Diptera systems, trait-matching is relatively unimportant.

Population dynamics of mutualism and intraspecific density dependence: How θ-logistic density dependence affects mutualistic positive feedback

Mutualism describes the biological phenomenon where two or more species are reciprocally beneficial, regardless of their ecological intimacy or evolutionary history. Classic theory shows that mutualistic benefit must be relatively weak, or else it overpowers the stabilizing influence of intraspecific competition and leads to unrealistic, unbounded population growth. Interestingly, the conclusion that strong positive interactions lead to runaway population growth is strongly grounded in the behavior of a single model. This model—the Lotka–Volterra competition model with a sign change to generate mutualism rather than competition between species—assumes logistic growth of each species plus a linear interaction term to represent the mutualism. While it is commonly held that the linear interaction term is to blame for the model's unrealistic behavior, we show here that a linear mutualism added to a θ-logistic model of population growth can prevent unbounded growth. We find that when density dependence is decelerating, the benefit of mutualism at equilibrium is greater than when density dependence is accelerating. Although there is a greater benefit, however, decelerating density dependence tends to destabilize populations whereas accelerating density dependence is always stable. We interpret these findings tentatively, but with promise for the understanding of the population ecology of mutualism by generating several predictions relating growth rates of mutualist populations and the strength of mutualistic interaction.

Determinants of the onset and strength of mutualistic interactions between branching corals and associate crabs

MEPS Marine Ecology Progress Series Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsTheme Sections MEPS 493:155-163 (2013) - DOI: https://doi.org/10.3354/meps10525 Determinants of the onset and strength of mutualistic interactions between branching corals and associate crabs Hannah L. Stewart1,3,*, Nichole N. Price2,4, Sally J. Holbrook1,2, Russell J. Schmitt1,2, Andrew J. Brooks1 1Marine Science Institute, University of California, Santa Barbara, California 93101, USA 2Department of Ecology, Evolution and Marine Biology, University of California, Santa Barbara, California 93106, USA 3Present address: West Vancouver Laboratory, Fisheries and Oceans Canada, West Vancouver, British Columbia V7V 1N6, Canada 4Present address: Scripps Institution of Oceanography, La Jolla, California 92093, USA *Email: hannahcriobe@gmail.com ABSTRACT: In mutualisms involving a host and symbiotic resident, the nature and strength of their interactions are unlikely to be constant over time or space. The efficacy of such mutualisms can be crucial to the population dynamics of one or both partners, particularly where survival bottlenecks occur at early life stages. In laboratory and field outplant experiments, we explored determinants of the onset of mutualistic interactions between early stages of branching corals and their trapeziid crab partners. We confirmed that recently settled crabs are capable of providing housekeeping services to their young coral partners (as has been reported for older crabs and corals), and the presence of a crab in areas of high sedimentation conferred growth benefits ~3 times as strong compared with low sediment conditions. We also showed that recruitment of post-larval crabs to very young corals increases with morphological complexity of the coral, which relates to the ability of the host to provide micro-refugia for its crab symbiont, and indicates the potential for selective pressure for traits that attract and retain crabs during this high-mortality bottleneck life stage. These findings provide insight into the recruitment process and ontogenetic constraints that influence the onset of mutualistic interactions between corals and their associated symbionts. KEY WORDS: Mutualism · Interaction strength · Crabs · Symbiosis · Coral morphology · Sediment · Ontogeny · Habitat selection Full text in pdf format PreviousNextCite this article as: Stewart HL, Price NN, Holbrook SJ, Schmitt RJ, Brooks AJ (2013) Determinants of the onset and strength of mutualistic interactions between branching corals and associate crabs. Mar Ecol Prog Ser 493:155-163. https://doi.org/10.3354/meps10525 Export citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 493. Online publication date: November 20, 2013 Print ISSN: 0171-8630; Online ISSN: 1616-1599 Copyright © 2013 Inter-Research.

Estimating the tolerance of species to the effects of global environmental change

Global environmental change is affecting species distribution and their interactions with other species. In particular, the main drivers of environmental change strongly affect the strength of interspecific interactions with considerable consequences for biodiversity. However, extrapolating the effects observed on pair-wise interactions to entire ecological networks is challenging. Here we propose a framework to estimate the tolerance to changes in the strength of mutualistic interaction that species in mutualistic networks can sustain before becoming extinct. We identify the scenarios where generalist species can be the least tolerant. We show that the least tolerant species across different scenarios do not appear to have uniquely common characteristics. Species' tolerance is extremely sensitive to the direction of change in the strength of mutualistic interaction, as well as to the observed mutualistic trade-offs between the number of partners and the strength of the interactions.