James N. Zahniser
Illinois Natural History Survey
1816 S. Oak St.
Champaign, IL 61820 USA
zahniser "at" uiuc.edu
James N. Zahniser
Illinois Natural History Survey |
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I recently graduated from the Department of Entomology at the University of Illinois at Urbana/Champaign. As a student in Dr. Chris Dietrich's lab, I studied the systematics of the leafhopper subfamily Deltocephalinae and related subfamilies. Here you can find some information on deltocephalines and can link to an interactive key to tribes of Deltocephalinae.
What is a leafhopper? CLICK HERE
The interactive key to tribes of Deltocephalinae and related subfamilies was created with the software package 3I by Dmitri Dmitriev. In addition to the many useful features of 3I, it includes dorsal and lateral habitus pictures of a member of each tribe, figures for many of the characters, and a short diagnosis and basic information "Remarks" section (see Remarks on taxon pages below figures). This key recognizes recent broader interpretations of the subfamily (Deltocephalinae sensu lato) that include Eupelicinae, Koebeliinae, Penthimiinae, and Selenocephalinae (Dietrich and Raktiov, 2002; Dietrich and Dmitriev, 2003). All tribes in those subfamilies are treated as tribes of Deltocephalinae. Some other related subfamilies are also included in the key. Note that the very large and poorly defined tribe Athysanini will be difficult to separate from some other tribes because it encompasses a lot of morphological diversity and is not defined by any unique characters.
Based on the number of described species Deltocephalinae s.l. is currently the largest subfamily of leafhoppers (Cicadellidae), itself one of the 10 largest families of insects, containing ~20,000 described species. Deltocepahlinae s.l. contains 36 tribes, ~850 genera, and ~6200 described species. It's an important group of insects because it contains many species that transmit pathogens to economically important plants. Some pests include the corn leafhopper, Dalbulus maidis (DeLong and Wolcott), the green rice leafhoppers, Nephotettix Matsumura spp., and the beet leafhopper, Circulifer tenellus (Baker).
Deltocephalines feed on the phloem sap of a wide variety of vascular plants, and the most obvious host-use pattern is evident in about 14 tribes in which all members feed only on grasses or sedges. These tribes make Deltocephalinae one of the most diverse and abundant groups of herbivores in grassland ecosystems, and grassland deltocephalines are often used as indicators of ecosystem quality.
I study various aspects of the systematics of Deltocephalinae. 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. I currently have a data set including 114 leafhopper taxa, ~2800 bp of the 28S rDNA gene, 352 bp of the histone H3 nuclear protein coding gene, and 119 morphological characters. Analyses of these were the basis for one chapter of my Ph.D. dissertation (deposited in December, 2008!).
I will use the phylogeny resulting from these analyses to revise the classification to reflect well-supported relationships. This will be the first classification of the group based on a phylogenetic analysis. I will also use the results to look at the evolution of grass specialization. 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 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. Because this is such a large group, you might imagine that there are many undescribed species out there, and there are! While there are about ~20,000 described species of leafhoppers, estimates of their actual diversity reach over 100,000 species! 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, 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 and Hicks from Peruvian grasslands. Some of the structures that we use to diagnose species include external 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 am looking closely at the phylogeny and historical biogeography of this grass-specializing tribe, which includes 15 genera and 323 described species, to determine it's area of origin and how it's members came to be distributed in the areas of the world as they are. Most genera are confined particular biogeographic areas, but some are much more widespread. Questions include: When did this group arise, and how does that compare with the origin of grasses (>65 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? |