Nitrogen and amino acids in nectar modify food selection of nectarivorous bats

Abstract

Summary1. Chiropterophilic flowers secrete sugar nectar with low-Nitrogen (N hereafter) content and small amounts of amino acids, which may function to attract animals; nevertheless, the role that micronutrients have on the foraging decisions of Neotropical nectarivorous bats is unknown. 2. We offered the nectar specialist Leptonycteris yerbabueanae and the omnivore Glossophaga soricina pairs of experimental diets mimicking either the N content or the relative abundance of 17 amino acids found in the floral nectar from the main plant species visited by these bats in a tropical dry forest. We addressed the following research questions: (i) Do bats select N-containing or sugar-only nectar differently based on bats' N nutritional status? (ii) Does the presence of N in nectar affect the capacity of bats to discriminate and select other nectar traits such as sugar concentration? and (iii) Are bats able to distinguish among the flavours generated by the amino acid relative abundance present in the nectar from plants they typically encounter in nature? 3. Our results showed that: (i) bats did not consider nectar N content regardless of their N nutritional condition, (ii) the nectar specialist L. yerbabuenae showed a preference for the most concentrated sugar-only nectar but changed to be indifferent when nectar contained N, and (iii) L. yerbabuenae preferred diets without amino acids and preferred the taste of the amino acids present in the nectar of Pachycereus pecten (Cactaceae) over those present in the nectar of Ceiba aesculifolia (Bombacaceae). 4. Our results suggest that regardless of the low concentrations at which N and amino acids are present in floral nectar, their presence affects bats' food selection by interfering with the bats' ability to detect differences in sugar concentrations, and by offering particular flavours that can be perceived and selected by nectarivorous bats. We discuss the ecological implications of the presence of N and amino acids in nectar on bats' foraging decisions.

Phenotypic selection on nectar amino acid composition in the Lepidoptera pollinated orchid species Gymnadenia conopsea

“…Positive and negative selection on nectar AA composition can occur as specific AAs attract or deter pollinators, most likely through nectar taste and scent (Petanidou et al , González‐Teuber and Heil , Nepi ). Although behavioural responses to nectar AAs were demonstrated for many different pollinator types (Bertazzini et al , Zhang et al , Rodríguez‐Peña et al ), still very little is known regarding the specific neurological or phago‐stimulating effects of different nectar AAs on pollinators in general and Lepidoptera in particular (González‐Teuber and Heil , Nepi ). Furthermore, we demonstrated phenotypic selection gradients which are likely pollinator‐mediated, but may also be influenced by multiple factors such as resource acquisition, antagonist selection or abiotic conditions (Sletvold et al ).…”

“…Furthermore, nectar sugars not only supply energy, they also aff ect the viscosity of nectar, and by extent the rate at which Lepidoptera can consume nectar (Pivnick and McNeil 1985). Th erefore, nectar sugar concentration corresponds to optimal rates of Suc linator types (Bertazzini et al 2010, Zhang et al 2011, Rodr í guez-Pe ñ a et al 2013, still very little is known regarding the specifi c neurological or phago-stimulating eff ects of diff erent nectar AAs on pollinators in general and Lepidoptera in particular (Gonz á lez-Teuber and Heil 2009, Nepi 2014). Furthermore, we demonstrated phenotypic selection gradients which are likely pollinator-mediated, but may also be infl uenced by multiple factors such as resource acquisition, antagonist selection or abiotic conditions .…”

Experimental fertilization increases amino acid content in floral nectar, fruit set and degree of selfing in the orchid Gymnadenia conopsea

“…Additionally, AAs such as Gln could provide pollinators with a beneficial addition for energetically expensive flight (Gardener and Gillman 2002). AA composition can affect the taste and scent of nectar, and therefore the different AA profiles obtained between treatments could have changed pollinator behaviour through specific neurological or phago-stimulating pathways (Nicolson and Thornburg 2007;Bertazzini et al 2010;Rodríguez-Peña et al 2013). A previous study showed that two AAs (Ser and Ala) were under phenotypic selection in G. conopsea, and could therefore be involved in the regulation of pollinator behaviour (Gijbels et al 2015).…”

Amino acid and carbohydrate tradeoffs by honey bee nectar foragers and their implications for plant-pollinator interactions

“…In addition to honey bees, AA preferences are reported for tropical stingless bees (Gardener et al, 2003; Roubik et al, 1995b), solitary bees (Weiner et al, 2010), butterflies (Erhardt and Rusterholz, 1998), ants (Bluthgen and Fiedler, 2004a, b; Wada et al, 2001), flies (Potter and Bertin, 1988), and nectivorous bats (Rodriguez-Pena et al, 2013). Differences in taste perception between diverse pollinators likely affect nectar perception and may be a factor in how plants bias pollinator visits, thereby affecting gene flow within and amongst plant populations (Nepi et al, 2012).…”