title: The influence of floral traits on specialization and modularity of plant-pollinator networks in a biodiversity hotspot in the Peruvian Andes.
abstract: Modularity is a ubiquitous and important structural property of ecological networks which describes the relative strengths of sets of interacting species and gives insights into the dynamics of ecological communities. However, this has rarely been studied in species-rich, tropical plant-pollinator networks. Working in a biodiversity hotspot in the Peruvian Andes we assessed the structure of quantitative plant-pollinator networks in nine valleys, quantifying modularity among networks, defining the topological roles of species and the influence of floral traits on specialization.
  
  
  
  A total of 90 transects were surveyed for plants and pollinators at different altitudes and across different life zones. Quantitative modularity (QuanBiMo) was used to detect modularity and six indices were used to quantify specialization.
  
  
  
  All networks were highly structured, moderately specialized and significantly modular regardless of size. The strongest hubs were Baccharis plants, Apis mellifera, Bombus funebris and Diptera spp., which were the most ubiquitous and abundant species with the longest phenologies. Species strength showed a strong association with the modular structure of plant-pollinator networks. Hubs and connectors were the most centralized participants in the networks and were ranked highest (high generalization) when quantifying specialization with most indices. However, complementary specialization d' quantified hubs and connectors as moderately specialized. Specialization and topological roles of species were remarkably constant across some sites, but highly variable in others. Networks were dominated by ecologically and functionally generalist plant species with open access flowers which are closely related taxonomically with similar morphology and rewards. Plants associated with hummingbirds had the highest level of complementary specialization and exclusivity in modules (functional specialists) and the longest corollas.
  
  
  
  We have demonstrated that the topology of networks in this tropical montane environment was non-random and highly organized. Our findings underline that specialization indices convey different concepts of specialization and hence quantify different aspects, and that measuring specialization requires careful consideration of what defines a specialist.
authors: Landscape and Biodiversity Research Group, Department of Environmental and Geographical Sciences, University of Northampton, Avenue Campus, St George's Avenue, Northampton NN2 6JD, UK hummingbird_pe@yahoo.com.
authors: Stella
authors: S
authors: Watts
authors: Department of Biometry and Environmental System Analysis, University of Freiburg, Tennenbacher Straße 4, D-79106 Freiburg, Germany.
authors: Carsten F
authors: CF
authors: Dormann
authors: Pacific Ecoinformatics Computational Ecology Lab, 1604 McGee Ave., 94703 Berkeley, CA, USA Center for Macroecology, Evolution and Climate, Natural History Museum of Denmark, University of Copenhagen, DK-2100 Copenhagen Ø, Denmark.
authors: Ana M
authors: AM
authors: Martín González
authors: Landscape and Biodiversity Research Group, Department of Environmental and Geographical Sciences, University of Northampton, Avenue Campus, St George's Avenue, Northampton NN2 6JD, UK.
authors: Jeff
authors: J
authors: Ollerton
mesh_terms: D000818:Animals; D001516:Bees / Q000502:physiology*; D044822:Biodiversity; D058448:Biota; D001717:Birds / Q000502:physiology*; D035264:Flowers; D010568:Peru; D010641:Phenotype; D010944:Plants; D054817:Pollination / Q000502:physiology*
keywords: Apis mellifera; Asteraceae; Baccharis; Bombus funebris; Peruvian Andes; biodiversity hotspot; floral traits; hummingbirds; modularity; plant–pollinator networks; specialization; topological roles