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United States Department of Agriculture

Agricultural Research Service

Title: Floral Trait Associations in Hawkmoth-Specialized and Mixed Pollination Systems

Authors
item Riffell, Jeffery - UNIVERSITY OF ARIZONA
item Alarcon Jr, Ruben
item Abrell, Leif - UNIVERSITY OF ARIZONA

Submitted to: Communicative and Integrative Biology
Publication Type: Other
Publication Acceptance Date: May 28, 2008
Publication Date: September 20, 2008
Citation: Riffell, J.A., Alarcon, R., Abrell, L. Floral trait associations in hawkmoth-specialized and mixed pollination systems. Communicative and Intergrative Biology 1(1):6-8. 2008.

Interpretive Summary: In southern Arizona, Manduca sexta hawkmoths are associated with the "hawkmoth-adapted" Jimsonweed (Datura wrightii) at both the larval and adult stages. Although Manduca prefers Datura's traits, they are flexible enough to learn how to utilize novel resources, such as "bat-adapted" Agave flowers, which they primarily feed on during the summer months. Given that Manduca are frequent visitors to agaves in southern Arizona, we hypothesize that the floral differences between two closely related species may be associated with the importance of hawkmoths relative to bats. The southernmost agave, Agave palmeri (Agavacea), exhibits floral traits typical of bat pollination, whereas the northernmost species, Agave chrysantha (Agavacea), exhibits traits which appear to be more adapted to insects. The differences between these agaves are likely correlated with the geographic overlap in migratory bats and hawkmoth populations.

Technical Abstract: Variation in floral traits including odor, color and morphology, demonstrate the selective pressures imposed by specific pollinator taxa, such as insects and birds. In southern Arizona, Manduca sexta (Sphingidae) hawkmoths are associated with Datura wrightii (Solanaceae) at both the larval (herbivore) and adult (nectar feeding) stages. However, during most of the summer Manduca feeds on "bat-adapted" Agave spp. (Agaveacea) flowers, and only use Datura when it is at peak bloom. Monduca's nectar-host use appears to be mediated through innate odor preferences and olfactory learning; they prefer Datura's "hawkmoth-adapted" traits, which facilitate the maintenance of their coevolutionary relationship, yet they are flexible enough to explore and learn to utilize novel resources, such as agave. This behavioral flexibility is likely responsible for the frequent observation of generalized, or mixed, pollination systems. Given that Manduca visit agave species in southern Arizona, we hypothesize that the differences in flower phenotype between two closely related agave species may be associated with the importance of hawkmoths relative to bats. The southernmost agave, Agave palmeri (Agavacea), exhibits floral traits typical of bat pollination, whereas the northernmost species, Agave chrysantha (Agavacea), exhibits mixed floral traits which appear to be adapted to insects, and to a lesser extent, bats. The differences between these agaves are likely correlated with the geographic overlap in migratory bats from Mexico and resident hawkmoth populations. Thus D. wrightii, A. palmeri and A. chrysantha populations represent a unique system in which to examine the evolution of floral traits in both specialized and mixed pollination systems associated with spatially variable pollinator assemblages.

Last Modified: 4/18/2014