Integrating nocturnal and diurnal interactions in a Neotropical pollination network

Plants establish pollination interactions with different groups of
animals, including nocturnal ones that establish interactions with
economically valuable and culturally important crops, as well as wild
plants of conservation concern. Despite the considerable number of studies
addressing the structure and dynamic of pollination networks, nocturnal
interactions have been relatively overlooked. Using a multilayer network
approach and considering diurnal and nocturnal interactions, we aimed to
understand how interactions at different periods of the day are integrated
and contribute to the network structural pattern. We also aimed to
highlight how multilayer networks may give a more nuanced assessment of
species importance across layers. We assembled a pollination network of an
intensively studied Neotropical area by standardizing interaction data
from 16 previous studies into a presence/absence (binary) network. Then we
used a multilayer network approach to evaluate the network modularity and
plant species' roles in these different temporal layers. Plants were
classified as nocturnal or diurnal according to the onset of floral
opening and pollinators were classified according to their foraging
period. The network consisted of 178 pollinator species and 158 plant
species, with 870 links. Among plant species, 135 species have diurnal
floral opening while 23 species are nocturnal. The multilayer network was
significantly modular, and these modules differed in the composition of
pollinator groups (e.g., hawk moths, bats, bees, hummingbirds), as well as
of diurnal and nocturnal plants. We show that diurnal and nocturnal
interactions are organized into interconnected modules in the multilayer
network. Nocturnal plants had higher values of versatility and multidegree
than diurnal plants, due to their role in connecting the two temporal
layers. Synthesis. Our study highlights the importance of integrating
different pollination systems to understand the importance of distinct
components that structure pollination networks. We also illustrate the
value of tapping into existing information, particularly species
interaction data, from well studied biodiversity hotspot areas, to gain a
better understanding of how communities are structured. Finally, despite
the relative scarcity of nocturnal pollination network studies, we showed
nocturnal plants, which often make complementary use of diurnal
pollinators, to be important in connecting the temporal layers.