Mixed-vertebrate pollination traits and pollinators of Haageocereus acranthus (Cactaceae) in a Lomas desert ecosystem of coastal Peru

(1) Cacti are key components of arid ecosystems and, being mostly self-incompatible, rely on animal pollination. Although bee pollination is ancestral, systems supported by birds, moths, bats, and mixed strategies have evolved. Despite the ecological uniqueness and extreme seasonality of the fog-dependent Lomas of coastal Peru, cacti pollination remains unstudied. This work examines Haageocereus acranthus, a characteristic columnar cactus of this ecosystem, in a population where individuals produce either white or pink-red flowers. It was hypothesized that white flowers would be associated with bat pollination and pink-red flowers with hummingbird pollination, reflected in differences in floral morphology, phenology and pollinator visitation. (2) Year-round monitoring of the population was conducted to characterize flowering phenology. Floral morphology, daily anthesis patterns, and nectar production were quantified and compared between color morphs. Floral visitor frequency and behavior were recorded using camera traps to test for pollinator preference. (3) Floral phenology, morphology, and nectar characteristics were broadly consistent with vertebrate pollination, showing traits associated primarily with bat pollination but also compatible with hummingbird pollination. These floral traits did not differ between color morphs. Hummingbirds were the most frequent visitors, followed by bats; yet, neither group showed preference for a specific flower color. (4) Findings support a mixed pollination system involving both hummingbirds and bats in an ecosystem where the availability of pollinators can shift over geographic or temporal scales. This pollinator unpredictability may ensure consistent reproductive success and reduce vulnerability to the absence or decline of specific pollinator groups. Key messageIn a Lomas desert ecosystem of coastal Peru, the columnar cactus Haageocereus acranthus shows traits and interactions consistent with a mixed-vertebrate pollination system (hummingbirds and bats), with no detectable differences between flower color morphotypes in either traits or interactions.