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Electric fields in terrestrial environments are used by caterpillars to detect their predators, as foraging cues by pollinators, and facilitate ballooning by spiders. This study shows that electric fields facilitate transportation and detection of hummingbirds in a guild of tropical phoretic mites. Hummingbird flower mites feed on nectar and pollen and complete their life cycle inside flowers. Mites colonize new flowers by hitching rides on hummingbird beaks. Flower mites emerge from hummingbird nostrils and disembark when the beak touches a flower. We tested whether flower mites are attracted to unmodulated electrostatic, or to modulated electric fields with amplitudes and frequencies in the range of those previously reported for hummingbirds. In a laboratory setup, mites were only attracted to modulated electric fields. In a choice experiment between positive or negative polarities, mites almost instantaneously chose positive charges, but only when the field was modulated. Mites display questing behavior, moving their front legs toward an electrostatic source. In experiments where we removed one or both front leg tarsi, we show that modulated fields are detected by sensory structures present in the front legs. We also show that flower mites use electrostatic attraction to bridge the gap to the beaks of hummingbirds, for a few milliseconds becoming one of the fastest terrestrial organisms. Our results confirm that hummingbird flower mites evolved an additional sensory modality — electroreception — to quickly detect hummingbirds and use electrostatics to facilitate transportation onto their hosts. 

ABSTRACT Most plant communities worldwide include exotic plants, which did not evolve with local organisms. The central goal of this study is to test if native organisms expanding their interactions to novel hosts are usually generalists or specialists. Here we studied new associations between hummingbirds, flower mites andMusa velutina(Musaceae), an exotic plant native to northeast India currently invading lowland forests in Costa Rica. Hummingbirds are pollinators, but flower mites feed on nectar without contributing to pollen transfer. Flower mites hitch rides on hummingbird beaks to colonize new flowers. To determine the original diet breadth of hummingbird and flower mite species, we assembled hummingbird and flower mite interactions at La Selva Biological Station. We identified four hummingbird species visitingMusa velutina. DNA barcode analyses identified only one species of flower mite colonizing flowers ofM. velutina. All new associations withM. velutinainvolved generalist hummingbird and flower mite species.Musa velutinadisplays both male and female flowers. Although flowers of both sexes were equally visited by hummingbirds, mites were 15 times more abundant in male than in female flowers. We hypothesize that this is the result of constant immigration coupled with mite population growth. Only half of the mites hitching rides on hummingbird beaks emigrate to newly opened flowers. Our results show thatM. velutinaintegration to a plant community occurs mainly by establishing interactions with generalists. 

Projecting ecological and evolutionary responses to variable and changing environments is central to anticipating and managing impacts to biodiversity and ecosystems. Current modeling approaches are largely phenomenological and often fail to accurately project responses due to numerous biological processes at multiple levels of biological organization responding to environmental variation at varied spatial and temporal scales. Limited mechanistic understanding of organismal responses to environmental variability and extremes also restricts predictive capacity. We outline a strategy for identifying and modeling the key organismal mechanisms across levels of biological organization that mediate ecological and evolutionary responses to environmental variation. A central component of this strategy is quantifying timescales and magnitudes of climatic variability and how organisms experience them. We highlight recent empirical research that builds this information and suggest how to design future experiments that can produce more generalizable principles. We discuss how to create biologically informed projections in a feasible way by combining statistical and mechanistic approaches. Predictions will inform both fundamental and practical questions at the interface of ecology, evolution, and Earth science such as how organisms experience, adapt to, and respond to environmental variation at multiple hierarchical spatial and temporal scales. 

Abstract Determining the factors affecting the structure of insect herbivore communities is a major challenge in ecology. Previous research demonstrated that plant defenses determine plant‐herbivore associations. However, non‐defensive variables may also explain why some plant species are associated with more diverse insect herbivore assemblages than others. Neotropical rolled‐leaf beetles (CephaloleiaandChelobasis) complete their life cycle inside the young rolled leaves of their host plants in the order Zingiberales. The diet breadth of each species in this assemblage is particularly well‐known at our study site, La Selva Biological Station in Costa Rica. This study focused on the following non‐defensive variables: host plant elevational and geographic range size, soil type, habitat, local abundance, plant size, and leaf size. Because plant characteristics among closely related plants are not independent, we analyzed these variables in a phylogenetic context. We detected a positive effect of leaf width on rolled‐leaf beetle species richness (explaining 55% of the variation), abundance (28% of the variation and 57% when habitat is included in the model), diversity (37% of the variation), and community structure (6% of the variation, and 21%–26% when taxonomic family is included in the model). Our study demonstrates that Zingiberales leaf width influences positively rolled‐leaf beetle species richness, abundance, and diversity. This effect varies among plant families. Our study shows that plant architecture plays an important role in structuring insect herbivore assemblages in Zingiberales. Our results highlight the importance of including variables beyond plant defenses to understand the ecology and evolution of plant‐herbivore interactions.