A network analysis of plant–pollinator interactions in temperate rain forests of Chiloé Island, Chile

Abstract

This study characterizes the structure of a plant-pollinator network in a temperate rain forest of Chiloé Island, southern Chile, where woody species are strongly dependent on biotic pollinators, and analyzes its robustness to the loss of participating species. Degree distribution, nestedness, and expected species persistence were evaluated. In addition, we assessed the roles of predefined subsets of plants (classified by life forms) and pollinators (grouped by taxonomic orders) in the network's structure and dynamics. For this, we simulated the complete removal of each plant and pollinator subset and analyzed the resultant connectivity patterns, as well as the expected long-term species losses by running a stochastic model. Finally, we evaluated the sensitivity of the network structure to the loss of single species in order to identify potential targets for conservation. Our results show that the plant-pollinator network of this Chilean temperate rain forest exhibits a nested structure of interactions, with a degree distribution best described by a power law model. Model simulations revealed the importance of trees and hymenopterans as pivotal groups that maintain the core structure of the pollination network and guarantee overall species persistence. The hymenopterans Bombus dahlbomii and Diphaglossa gayi, the shrubs Tepualia stipularis and Ugni molinae, the vines Mitraria coccinea and Asteranthera ovata, and the entire set of tree species exerted a disproportionately large influence on the preservation of network structure and should be considered as focal species for conservation programs given current threats from selective logging and habitat loss.

Resilient Networks of Ant-Plant Mutualists in Amazonian Forest Fragments

“…Within habitat heterogeneity is hypothesized to have a major influence on network topology [11], [51] via sampling effects [35] and because interaction probabilities will depend on the distribution of individuals across the landscape [11]. Unfortunately, most studies of mutualistic networks have been conducted in a single location [52], so addressing this important issue remains a challenge. In our sites, common species were consistently present but links with less common species were unpredictable.…”

Topological plasticity increases robustness of mutualistic networks

“…S1, Supporting information): (i) the Llao‐Llao network (Llao), containing 11 plant species, 29 pollinators and 52 pollination interactions, which was recorded in a temperate forest of southern Argentina (Aizen, Morales & Morales 2008), (ii) the palm‐swamp network (Palm), containing 28 plants, 53 pollinators and 109 interactions, from the Venezuelan central plains (Ramírez & Brito 1992) and (iii) the Chiloé network (Chil), containing 26 plant species, 128 pollinator species and 311 interactions, which was recorded in the austral rainforests in Chiloé Island, Chile (Smith‐Ramírez et al. 2005; see also Ramos‐Jiliberto et al. 2009).…”

Diptera species and functional diversity across tropical Australian countryside landscapes

“…The implications of reductions in pollinators in ecosystems include lower or more variable rates of pollination, and lower fruit set and seed output for native plants (Wilcock and Neiland, 2002;Pauw, 2007) and nearby agricultural crops (Ricketts, 2004). Such changes may lead to long-term changes in the population dynamic of some plant species, and perhaps plant and insect community dynamics over longer time spans (Ramos-Jiliberto et al, 2009).…”