James N. Zahniser
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I am currently an Entomologist with the USDA-APHIS-PPQ in San Diego, CA. My academic interest is in the systematics of the leafhopper subfamily Deltocephalinae, and I studied and trained in the laboratory of Dr. Chris Dietrich at the Illinois Natural History Survey. Here you can find some information on deltocephaline leafhoppers and can link to an interactive key to tribes of Deltocephalinae or search the database.
What is a leafhopper? CLICK HERE
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 38 tribes, 923 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 38 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. Right now, it appears that almost all of the grass-specializing tribes are closely related to one another, suggesting that the switch to grass specialization was a very 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 just a few recent collections from 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. Pictures courtesy of Zootaxa.
This new species is included in the tribe Chiasmini. I have studied and recently published on the phylogeny and historical biogeography of this grass-specializing tribe, which includes 20 genera and 316 described species, to determine where the group originated and how its members came to be distributed around the world as they are today. Questions include: When did this group arise, and how does that compare with the origin of grasses (~80 million years ago) and the expansion of grasslands in the Oligocene and Miocene (15-30 mya)? How have dispersal, plate tectonics, and historical ecological conditions contributed to the distributional pattern we see today?