Foliar Extrafloral Nectar of Humboldtia brunonis (Fabaceae), a Paleotropic Ant‐plant, is Richer than Phloem Sap and More Attractive than Honeydew

Abstract

The ant-plant Humboldtia brunonis secretes extrafloral nectar (EFN) despite the lack of antiherbivore protection from most ants. EFN was richer in composition than phloem sap and honeydew from untended Hemiptera on the plant, suggesting that EFN could potentially distract ants from honeydew, since ants rarely tended Hemiptera on this plant.

Morpho–anatomical and ultrastructural analysis of extrafloral nectaries in Inga edulis (Vell.) Mart. (Leguminosae)

“…(Sinisterra et al 2016), I. goldmanii Pittier (Coley et al 2005), Humboldtia brunonis Wall. (Chanam et al 2015), Chamaecrista debilis (Vogel) Irwin & Barneby (Nascimento and Del-Claro 2010) and Vicia faba L. (Katayama and Suzuki 2004).…”

Why are flowers sweeter than fruits or buds? Variation in extrafloral nectar secretion throughout the floral ontogeny of a myrmecophile

“…, Chanam et al . ), and the interaction between several ontogenetic factors (Miller ). These studies all indicate that EFN secretion increases with plant size or age, and that nectaries associated with reproductive parts (buds, flowers and fruits) are more productive than their vegetative counterparts.…”

“…For example, Chanam et al . () suggest that Humboldtia brunonis might have evolved an ant‐catered EFN composition in order to distract ants from tending aphids. They demonstrate that EFN is different to and more attractive to ants than phloem sap and honeydew.…”

“…Many studies have shown that plant defenses vary throughout plant and leaf development (Kursar & Coley 2003, Barton & Koricheva 2010, Quintero et al 2013. In particular, for ant-plant associations, ontogeny plays a key role regulating EFN secretion: quantity and quality changes with leaf age (Heil et al 2000, Miller et al 2010, plant structure size (Falcão et al 2014), plant size (Trager & Bruna 2006), plant ontogenetic stages (Villamil et al 2013, Ochoa-L opez et al 2015, vegetative and reproductive structures (W€ ackers & Bonifay 2004, Shenoy et al 2012, Chanam et al 2015, and the interaction between several ontogenetic factors (Miller 2014). These studies all indicate that EFN secretion increases with plant size or age, and that nectaries associated with reproductive parts (buds, flowers and fruits) are more productive than their vegetative counterparts.…”

“…EFN catering is more specialized and complex than was once recognized and is known to be more than simply collateral phloem sap exudate. For example, Chanam et al (2015) suggest that Humboldtia brunonis might have evolved an ant-catered EFN composition in order to distract ants from tending aphids. They demonstrate that EFN is different to and more attractive to ants than phloem sap and honeydew.…”