DIVERSITY OF THE LEAFHOPPER (HOMOPTERA, CICADELLIDAE) FAUNA OF NORTHERN CHIHUAHUAN GRASSLANDS, WITH EMPHASIS ON GYPSUM GRASSLANDS AND DESCRIPTION OF A NEW SPECIES OF ATHYSANELLA (CICADELLIDAE, DELTOCEPHALINAE)

Extensive areas of the northern Chihuahuan Desert of southeastern New Mexico and adjacent Texas have gypsum (gyp) outcroppings. The plant co mmunities of these regions contain a mixture of gypsum-tolerant plants characteristic of the semiarid grasslands surrounding the gyp islands , and plants endemic to or characteristic of and attaining highest abu ndance in gyp areas. The insularity of the gyp formations provides an ideal situation for insect as well as plant evolution. Collections wer e made on 37 dominant or subdominant perennial grasses of the region. Twelve generalists and 54 specialist leafhopper species were recorded. The leafhopper diversity of the grasslands is explained by the existe nce of a large number of perennial grass hosts. Two of the hosts, gyp grama (Bouteloua breviseta) and gyp dropseed (Sporobolus nealleyi) acc ount for three of the specialists, which are therefore endemic to gyp grasslands. One of these specialists is Athysanella (Athysanella) bloc keri, n. sp., taken from gyp grama, Bouteloua breviseta, and is descri bed herein. Other leafhopper-grass host relationships in the New Mexic o-Texas grasslands studied, on both gyp and nongyp soils, were similar to those of adjacent vegetational regions.