EVOLUTION AND HISTORICAL ECOLOGY OF THE PROCONIINI SHARPSHOOTERS

• Author(s): Dietrich, Christopher; Rakitov, Roman;
• Abstract: The tribes Proconiini and Cicadellini, commonly referred to as sharpshooters (Cicadellinae sensu Young 1968), together form the largest group of xylem-feeding leafhoppers and include most of the known vectors of xylem-born phytopathogenic organisms. Proconiini is a strictly New World group with most of its diversity confined to the tropical regions. Among ca. 350 described proconiine species, currently grouped into 56 genera, less than 10% (4 genera) occur north of Mexico, and only one genus (Cuerna) has substantially radiated in the temperate parts of the U.S. and Canada. In spite of its largely tropical distribution, the group is of significant economic importance in the U.S. because several Homalodisca, Oncometopia, and Cuerna species are able to transmit Xylella fastidiosa (Xf) (Nielson 1968), and two of them recently invaded new areas in the southern U.S. (Pollard et al. 1959; Sorensen & Gill 1996). Species of Oncometopia and Acrogonia are also principal vectors of Xf causing the citrus variegated chlorosis in South America (Gravena et al. 1998). Except for a few economically important species, the data on the ecology and bionomics of proconiines are virtually absent, although this picture is beginning to change. In particular, recent studies suggest that in at least 13 proconiine genera females display a unique type of maternal care by powdering their egg nests with brochosomes, specific Malpighian tubule products unique to leafhoppers (Rakitov 1999, 2000, and unpublished; Hix 2001). Although the exact adaptive significance of this behavior is not yet clear, its occurrence in several of the most speciose proconiine genera, including Homalodisca, Oncometopia, and Acrogonia , which contain principal vectors of Xf, suggests that its advantages may have facilitated speciation and contributed to the pest status of some species, perhaps by increasing their capability to colonize a wide range of vegetation. Building a robust estimate of the evolutionary relationships among Proconiini is important to provide a framework in which ecological and bionomical features, and the patterns of distribution of the group can be better understood. In the absence of fossil evidence this can be achieved by the phylogenetic analysis of the distribution of morphological, molecular, and other characters among modern species. Unfortunately, the only such analysis of Proconiini performed so far (Mejdalani 2000) focused on only one group of presumably related genera and therefore has not completely elucidated the relationships within the tribe.
• Publication Date: Dec 2001
• Journal: 2001 Pierce's Disease Research Symposium