Bat pollination in the NE Brazilian endemic Mimosa lewisii: an unusual case and first report for the genus

Abstract

AbstractMimosa lewisii (Section Batocaulon), a shrub of the NE‐Brazilian Caatinga, presents huge (pseudo‐)racemes that form a separate storey overtopping the foliage. Racemes persist, developing intermittently pedunculate capitula over a period of more than one year. The brush‐type, whitish flower heads are nocturnal in anthesis and active only a single night. Florets are relatively large and stout for the genus, hermaphroditic, with stiff filaments and style, and converge towards the periphery of the raceme. When expanding at dusk, the heads produce large nectar drops (up to 173 μl per head), that averages 25–29% sucrose. Production starts sequentially among florets of a capitulum. The drops are freely exposed, held between the filaments. The glossophagine bat Lonchophylla mordax was observed as the only legitimate visitor; hummingbirds exploited worn capitula at daytime, but did not pollinate. The bats lapped the nectar while hovering without apparently putting out their tongues. Pollen transmission was by the snout and probably by touching neighbouring flower heads with the wings. The blossoms, of a genus predominantly entomophilous, reveal habitual adaptation to bat pollination in most of their features. Small size (14 mm in diam.) and lack of a perceptible scent suggest that an evolutionary shift towards chiropterophily is still incomplete. A brief survey of the known distribution of bat pollination in Mimosaceae is appended.