Ecological, historical and evolutionary determinants of modularity in weighted seed‐dispersal networks

Schleuning, Matthias; Ingmann, Lili; Strauß, Rouven; Fritz, Susanne A.; Dalsgaard, Bo; Dehling, D. Matthias; Plein, Michaela; Saavedra, Francisco; Sandel, Brody; Svenning, Jens‐Christian; Böhning‐Gaese, Katrin; Dormann, Carsten F.

doi:10.1111/ele.12245

Cited by 165 publications

(264 citation statements)

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“…Most interestingly for our study, we found a strong consistent negative association between TS and SRS (figure 2) and, when accounting for the indirect effects of climate on specialization via SRS, a direct positive association of TS on specialization appeared (figure 2b). A similar positive association between modularity and TS has been documented for frugivorous bird-plant networks [49], which was argued to derive from a higher annual turnover in species composition and interactions in more seasonal environments. The combined effects of topography and climate seasonality on SRS (figure 2), together with the much stronger effect of SRS on specialization than vice versa (b ¼ 0.75 versus b ¼ 0.43), is in accordance with the hypothesis that climate stability may increase specialization through reduced annual species range dynamics [30,69], facilitating adaptation to local foraging niches.…”

Section: Discussionsupporting

confidence: 66%

High proportion of smaller ranged hummingbird species coincides with ecological specialization across the Americas

et al. 2016

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Ecological communities that experience stable climate conditions have been speculated to preserve more specialized interspecific associations and have higher proportions of smaller ranged species (SRS). Thus, areas with disproportionally large numbers of SRS are expected to coincide geographically with a high degree of community-level ecological specialization, but this suggestion remains poorly supported with empirical evidence. Here, we analysed data for hummingbird resource specialization, range size, contemporary climate, and Late Quaternary climate stability for 46 hummingbird -plant mutualistic networks distributed across the Americas, representing 130 hummingbird species (ca 40% of all hummingbird species). We demonstrate a positive relationship between the proportion of SRS of hummingbirds and community-level specialization, i.e. the division of the floral niche among coexisting hummingbird species. This relationship remained strong even when accounting for climate, furthermore, the effect of SRS on specialization was far stronger than the effect of specialization on SRS, suggesting that climate largely influences specialization through species' range-size dynamics. Irrespective of the exact mechanism involved, our results indicate that communities consisting of higher proportions of SRS may be vulnerable to disturbance not only because of their small geographical ranges, but also because of their high degree of specialization.

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Section: Discussionsupporting

confidence: 66%

High proportion of smaller ranged hummingbird species coincides with ecological specialization across the Americas

et al. 2016

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“…Many animal species consume similar resources, yet variation in morphology, physiology or behaviour can result in profound differences in ecological interactions [5][6][7]. Our analysis revealed high levels of generalization in seed dispersal networks mediated by fish, birds and mammals.…”

Section: Discussionmentioning

confidence: 80%

Stability and generalization in seed dispersal networks: a case study of frugivorous fish in Neotropical wetlands

Correa¹,

Arujo

Penha

et al. 2016

Proc. R. Soc. B.

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When species within guilds perform similar ecological roles, functional redundancy can buffer ecosystems against species loss. Using data on the frequency of interactions between fish and fruit, we assessed whether co-occurring frugivores provide redundant seed dispersal services in three species-rich Neotropical wetlands. Our study revealed that frugivorous fishes have generalized diets; however, large-bodied fishes had greater seed dispersal breadth than small species, in some cases, providing seed dispersal services not achieved by smaller fish species. As overfishing disproportionately affects big fishes, the extirpation of these species could cause larger secondary extinctions of plant species than the loss of small specialist frugivores. To evaluate the consequences of frugivore specialization for network stability, we extracted data from 39 published seed dispersal networks of frugivorous birds, mammals and fish (our networks) across ecosystems. Our analysis of interaction frequencies revealed low frugivore specialization and lower nestedness than analyses based on binary data (presence-absence of interactions). In that case, ecosystems may be resilient to loss of any given frugivore. However, robustness to frugivore extinction declines with specialization, such that networks composed primarily of specialist frugivores are highly susceptible to the loss of generalists. In contrast with analyses of binary data, recently developed algorithms capable of modelling interaction strengths provide opportunities to enhance our understanding of complex ecological networks by accounting for heterogeneity of frugivore-fruit interactions.

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“…Species with certain morphologies (i.e. combinations of species traits) from one trophic level interact with species of corresponding morphologies from the other trophic level, leading to a compartmentalization of the interaction networks (modularity) [43,44], and also of the trait spaces of the interacting species groups. The congruency in the trait spaces also corroborates the finding that trait matching in individual interactions leads to covariation in the functional diversity of interacting species groups on large spatial scales [5].…”

Section: (E) Relationship Between Morphological and Functional Speciamentioning

confidence: 99%

Morphology predicts species' functional roles and their degree of specialization in plant–frugivore interactions

et al. 2016

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Species' functional roles in key ecosystem processes such as predation, pollination or seed dispersal are determined by the resource use of consumer species. An interaction between resource and consumer species usually requires trait matching (e.g. a congruence in the morphologies of interaction partners). Species' morphology should therefore determine species' functional roles in ecological processes mediated by mutualistic or antagonistic interactions. We tested this assumption for Neotropical plant-bird mutualisms. We used a new analytical framework that assesses a species's functional role based on the analysis of the traits of its interaction partners in a multidimensional trait space. We employed this framework to test (i) whether there is correspondence between the morphology of bird species and their functional roles and (ii) whether morphologically specialized birds fulfil specialized functional roles. We found that morphological differences between bird species reflected their functional differences: (i) bird species with different morphologies foraged on distinct sets of plant species and (ii) morphologically distinct bird species fulfilled specialized functional roles. These findings encourage further assessments of species' functional roles through the analysis of their interaction partners, and the proposed analytical framework facilitates a wide range of novel analyses for network and community ecology.

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Ecological, historical and evolutionary determinants of modularity in weighted seed‐dispersal networks

Cited by 165 publications

References 50 publications

High proportion of smaller ranged hummingbird species coincides with ecological specialization across the Americas

High proportion of smaller ranged hummingbird species coincides with ecological specialization across the Americas

Stability and generalization in seed dispersal networks: a case study of frugivorous fish in Neotropical wetlands

Morphology predicts species' functional roles and their degree of specialization in plant–frugivore interactions

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