Southern Monarchs do not Develop Learned Preferences for Flowers With Pyrrolizidine Alkaloids

Abstract

Danaus butterflies sequester pyrrolizidine alkaloids (PAs) from nectar and leaves of various plant species for defense and reproduction. We tested the hypothesis that the southern monarch butterfly Danaus erippus shows innate preferences for certain flower colors and has the capacity to develop learned preferences for artificial flowers presenting advantageous floral rewards such as PAs. We predicted that orange and yellow flowers would be innately preferred by southern monarchs. Another prediction is that flowers with both sucrose and PAs would be preferred over those having sucrose only, regardless of flower color. In nature, males of Danaus generally visit PA sources more often than females, so we expected that males of D. erippus would exhibit a stronger learned preference for PA sources than the females. In the innate preference tests, adults were offered artificial non-rewarding yellow, orange, blue, red, green, and violet flowers. Orange and yellow artificial flowers were most visited by southern monarchs, followed by blue and red ones. No individual visited either green or violet flowers. For assessing learned preferences for PA flowers over flowers with no PAs, southern monarchs were trained to associate orange flowers with sucrose plus the PA monocrotaline vs. yellow flowers with sucrose only; the opposite combination was used to train another set of butterflies. In the tests, empty flowers were offered to trained butterflies. Neither males nor females showed learned preferences for flower colors associated with PAs in the training set. Thus, southern monarchs resemble the sister species Danaus plexippus in their innate preferences for orange and yellow flowers. Southern monarchs, similarly to temperate monarchs, might not be as PA-demanding as are other danaine species.

Plant secondary metabolites in nectar: impacts on pollinators and ecological functions

“…For some of these potential mechanisms there is little information available for pollinators compared with herbivores . For example, we could find only one example of a pollinator sequestering nectar toxins: the adult danaid butterflies that feed on milkweeds as larvae sequester pyrrolizidine alkaloids from nectar (de Oliveira, Trigo & Rodrigues 2015). Biotransformation processes used to avoid self-poisoning by pyrrolizidine alkaloids are summarized by Hartmann et al (2004).…”

Learning in two butterfly species when using flowers of the tropical milkweed Asclepias curassavica: No benefits for pollination

“…Danaus erippus constantly searched for nectar in the petals, while H. erato learned to avoid these parts as the trials progressed. Although D. erippus is able to associate colors with rewards in the context of feeding (de Oliveira et al, 2015; Rodrigues, 2016), innate preferences for orange may have influenced searching for nectar in the orange‐reddish petals. A similar result was found in Pieris napi (Linnaeus, 1758) when using artificial flowers.…”

“…Danaus erippus and H. erato have long life spans, and adults are large and medium‐sized, respectively (Ehrlich and Gilbert, 1973; Brown, 1981; Ackery and Vane‐Wright, 1984; DeVries, 1987; Rodrigues and Moreira, 2004). Both species have innate preferences for orange, red, and yellow (Swihart and Swihart, 1970; Barp, 2006; de Oliveira et al, 2015). They visit a wide range of angiosperms when foraging for nectar (Ackery and Vane‐Wright, 1984; Corrêa et al, 2001; Slager and Malcolm, 2015).…”

“…Butterflies are active foragers (Lewis and Lipani, 1990; Bauder et al, 2015), and their cognitive abilities allow them to select profitable nectar sources, exploit complex flowers (Lewis and Lipani, 1990; Weiss, 1995), and find suitable hosts for oviposition and larval feeding (McNeely and Singer, 2001; Weiss and Papaj, 2003; Snell‐Rood and Papaj, 2006; Silva et al, 2014). Danaus erippus and H. erato associate flowers with feeding rewards (Barp et al, 2011; de Oliveira et al, 2015; Dell'Aglio et al, 2016; Rodrigues, 2016) and have different diets; H. erato feeds on pollen as well as nectar (Gilbert, 1972). These features make this system a promising model to evaluate the effect of learning on the pollination success of a plant species with complex flowers.…”

Innate and learnt color preferences in the common green-eyed white butterfly (Leptophobia aripa): experimental evidence

“…The innate preference experiment was comprised of two phases: (1) The 5-min priming phase allowed butterflies to hand-feed on a black color artificial flower in order to enhance their association between artificial flower models and the presence of a sugar reward ( i.e ., by carefully unrolling the proboscis into 5 μl of 25% sugar solution); (2) The testing phase evaluated an individual’s preference for a specific flower color. The use of artificial black flowers to stimulate butterfly’s interest in foraging prior to the start of a given training or testing session is frequent in the literature ( e.g ., Swihart & Swihart, 1970 ; Rodrigues, Goodner & Weiss, 2010 , Blackiston, Briscoe & Weiss, 2011 ; Rodrigues & Weiss, 2012 ; Cepero, Rosenwald & Weiss, 2015 , de Oliveira, Trigo & Rodrigues, 2015 ; Rodrigues, 2016 ; Esmaile & Rodrigues, 2020 ). Previous studies have shown that butterflies do not visit artificial flowers of this color during foraging trials ( e.g ., Swihart & Swihart, 1970 ; Esmaile & Rodrigues, 2020 ).…”