Sowing shrub species with a steady-state flowering phenology as a more spatially compact approach for biodiversity conservation in tropical agroecosystems

Background/Question/Methods

Plant species with a continuous or steady-state flowering strategy are supported only in aseasonal environments, are rare and have most notably been associated with hummingbird pollination. However, because these plants often produce large quantities of nectar on a daily basis in a predictable location, many other taxonomic groups may opportunistically take advantage of these food resources. Animal species in the neotropics have evolved under a lower spatiotemporal patchiness of food resources compared to the other tropical regions, and plant species with a steady-state flowering phenology may decrease the higher temporal variation in food resource availability caused by the conversion of forests to agriculture. Here, we ask whether plant species with steady-state flowering, by reducing the temporal variation in nectar resource availability, can be used to increase the diversity and abundance of several taxonomic groups in agricultural lands. Six, 1-ha coffee agroforests were selected, and each treatment agroforest received a supplemental patch of a shrub species with a steady-state flowering phenology, Hamelia patens Jacq. Twelve H. patensshrubs were planted in each treatment agroforest, and malaise traps and mist-nets were used to sample arthropods and hummingbirds during two years, following initiation of flowering in patches (approx. 8 months post-planting).  

Results/Conclusions

Generalized linear mixed models, ANOVAs and rarefaction curves were used to compare taxonomic group abundance and species richness between treatments. A total of 112 hummingbirds from 7 species, 939 butterflies from 49 species, 4862 wasps from 160 morphospecies, and 1450 bees from 44 species were captured in both agroforest types. Rarefaction curves constructed from mist-net and Malaise trap data showed 31% more butterfly species and 29% more hummingbird species in coffee agroforests with the supplemental patch. Sixty-five percent more wasps (P = 0.045) and 85% more bees (P = 0.16) were captured in agroforests with the supplemental patch. With the broad array of taxonomic groups observed to use resources of H. patens, its production of resources during times of resource scarcity, and its resource reliability in an otherwise patchy resource environment, H. patens may be a practical solution for biodiversity conservation in agroecosystems where space available for non-crop plantings is limited. The identification of plant species that support a high number of animal species, including important ecosystem service providers, is becoming increasingly important for restoration/conservation applications. Throughout the Neotropics plant species with a steady-state flowering phenology can be found in all aseasonal forests and evaluated for their conservation value.