Evolution of Novel Ovipositional Behavior in Neotropical Leafhopper Tribe Proconiini

Dietrich, C. H., Rakitov, R. A. , Takiya D. M.
Support: NSF DEB­0089671 (to C. H. Dietrich)

Female Acrogonia sp. from Guatemala displays reserves of brochosomes to be used in oviposition on its forewings.

The discovery of a unique oviposition behavior in certain Neotropical leafhoppers of the tribe Proconiini provides an opportunity to examine the evolutionary steps involved in the acquisition of a complex set of correlated behavioral, morphological, and physiological traits within a phylogenetic context. Unlike other leafhoppers, which insert their eggs into plant tissues without covering the ovipositional scars, some proconiine species cover the scars or exposed egg masses with brochosomes, ultramicroscopic excretory particles produced by specialized cells of the Malpighian tubules (MT). In other leafhoppers brochosomes are used only as a protective coat of the integument; thus, the use of this secretory material in oviposition seems to be an evolutionary novelty. Three ontogenetically independent structures involved in this novel behavior— brochosomes, hindlegs, and tegmina (forewings)–show corresponding modifications that are markedly expressed in females and poorly, or not expressed in males, suggesting that sexual dimorphism was derived by modification of originally monomorphic traits. Each trait exhibits gradient-like variation from unspecialized to highly specialized conditions among proconiine taxa, possibly reflecting a temporal succession in the evolution of the syndrome.

The project has two main objectives: 1. To estimate the phylogenetic relationships among proconiine leafhoppers using DNA sequence data. 2. To examine the evolution of various behavioral, morphological and physiological traits associated with the unique ovipositional syndrome.

Development of a robust estimate of proconiine phylogeny based on molecular data will enable us to address several questions including: (1) Have the syndrome and its individual components arisen more than once in the group? (2) Did acquisition of all components of the syndrome coincide, or were they acquired in a stepwise progression? (3) What was the key innovation, if any? (4) Did acquisition of the new syndrome facilitate speciation?