James N. Zahniser
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I am currently an Entomologist with USDA-APHIS-PPQ in Washington, DC. My research interest is mainly on the systematics of the leafhopper subfamily Deltocephalinae. Here you can find some information on deltocephaline leafhoppers and can link to an interactive key to tribes of Deltocephalinae or search the database.
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Based on the number of described species, Deltocephalinae is currently the largest subfamily of leafhoppers (Cicadellidae), itself one of the 10 largest families of insects, containing ~22,000 described species. Deltocephalinae contains 39 tribes, 926 genera, and ~6700 valid species. It is an important group of insects because it contains many species that transmit pathogenic diseases to economically important plants. Some important vector species include the corn leafhopper, Dalbulus maidis (DeLong and Wolcott), the green rice leafhoppers, Nephotettix Matsumura spp., and the beet leafhopper, Neoaliturus tenellus (Baker).
Deltocephalinae feed on the phloem sap of a wide variety of vascular plants. Nearly all members of 14 of the 39 tribes feed only on grasses or sedges. These tribes are diverse, are all relatively closely related, and make Deltocephalinae one of the most diverse and abundant groups of herbivores in grassland ecosystems. Grassland deltocephalines are sometimes used as indicators of ecosystem quality.
I study various aspects of the systematics of Deltocephalinae, including descriptive and revisionary taxonomy, phylogenetic analysis, and historical biogeography. One of my main goals is to come up with hypotheses of relationships among the major lineages of this group. I use morphological and molecular (DNA) data gathered from representatives throughout the lineage to do this and I use results from these analyses to revise classifications to reflect well-supported relationships. Interesting patterns sometimes emerge from these phylogenetic analyses. Analyses to date suggest that almost all of the grass-specializing tribes are closely related to one another, suggesting that the switch to grass specialization was a rare evolutionary event in the history of the lineage. What enabled this innovation- morphlogical or physiogical adapatations, newly acquired microbial symbionts, or behavioral changes? And did this change in feeding mode increase the success of this lineage or promote a rapid radiation? These are some interesting questions raised by these results and might be addressed in the future.
I am also very interested in finding and describing new species of leafhoppers. There are untold thousands of undiscovered species just waiting for attention! While there are about ~22,000 described species of leafhoppers, estimates of their actual diversity reach well over 100,000 species! In addition to describing and naming new species and higher taxa, I work to develop improved identification keys, taxonomic revisions, and revised classifications that will facilitate further work.
Grasslands are one of the most highly threatened ecosystems in the world, yet their biodiversity remains very poorly known. Based on our discoveries of many new grassland deltocephaline species from recent collections in understudied regions, there appears to lie a rich fauna of leafhoppers (and probably other grassland arthropods and associated species) waiting to be discovered. To the left is a plate of the species Icaia straminea Zahniser & Hicks that we described from Peruvian grasslands. Some of the structures that we use to diagnose species include the shapes of the head and other body parts, coloration, and internal characters of the male and female genitalia. Image courtesy of Zootaxa.
This species is included in the tribe Chiasmini. Using molecular data from four gene regions I reconstructed the phylogeny of this tribe in order to examine its historical biogeographical patterns. These analyses recovered two strongly supported clades of Chiasmini. One of these clades, containing the genera Leofa, Nephotettix, and Exitianus, shows a clear pattern of origin in the Old World, and a long-distance, trans-oceanic dispersal to the New World by a species group within Exitianus. This species group first colonized the New World in South America and subsequently diversified and colonized North America, accounting for the current worldwide distribution of the genus. The area of origin biogeographic patterns of the other main clade of Chiasmini is less clear. To date, there are no clear, consistently recovered biogeographic patterns of grassland-associated insects. This might be because the causes and conditions affecting their distributions vary widely, thus producing the idiosyncratic patterns observed in particular lineages.