30 Jan Daily niche overlap of a hummingbird-plant network in the southeastern Atlantic Forest, Brazil (contributed by Andrea Nieto, MS student with Isabela )
For my master’s research, I evaluated short-term temporal niche partitioning of a plant-hummingbird network in the Atlantic Forest from southeastern Brazil (Figure 1). The Atlantic Forest harbors many bromeliads species, which are mainly pollinated by hummingbirds.
Some of these plant species share the same pollinator species, bloom at the same time and have flowers that last only a single day. Here, time is crucial for plant pollination and for hummingbird nectar acquisition. Under this scenario, where plant species may be competing for pollinators and hummingbirds for nectar, I explored temporal patterns of nectar production and hummingbird visits throughout the day. If competition is strongly structuring this plant-hummingbird network, then plant species should produce nectar at different times throughout the day, especially when many other species are blooming at the same time (co-flowering) and are visited by the same hummingbird species. Hummingbird species should visit plant species during different times of the day to avoid competition if resources are limited.
During eight months from November 2018 to July 2019, I recorded 488 plant-hummingbird interactions between four hummingbird species (Phaethornis eurynome, P. squalidus, Ramphodon naevius, and Thalurania glaucopis) and 12 plant species. Plants visited by hummingbirds belonged to Bromeliaceae (88%), followed by Acanthaceae (12%). Nectar was available throughout the day, and it was mainly offered by Bromeliaceae, indicating that plant species of this family were the most important nectar source for hummingbirds. Across all plant species there was considerable overlap in temporal nectar production; however there were some exceptions where pairs of plant species produced nectar at different times. Total pairwise overlap in temporal nectar production (mg sugar) did not vary when plant species flowered at the same time as other species (co-flowering; Figure 2A) or when they shared at least one hummingbird species. (Figure 2). The hummingbirds not only visited the same plant species, but also foraged on them at the same time throughout the day. They fed more actively between 06h00 and 10h00, during which 56% of the visits occurred. My results suggest that competition was limited between both plant and hummingbird species. Instead, positive interactions, such as facilitation, might be structuring this mutualistic network. For plants, co-flowering or sharing a hummingbird species may have a benefit. By blooming together, plants attract more pollinators and may avoid heterospecific pollen transfer by depositing pollen on different body parts of their pollinators. Hummingbirds may facilitate each other as their constant visits to plants promotes pollination and, thus, population stability in their resource plants.
These results serve to better understand niche partitioning within hummingbird-plant networks at a temporal scale that is rarely considered in pollination systems – a daily scale. Also, my findings suggest facilitation is a possible mechanism influencing the plant and hummingbird community in this area in the Atlantic Forest.