@article {50548, title = {Desert grassland canopy arthropod species richness: temporal patterns and effects of intense, short-duration livestock grazing}, journal = {Journal of Arid Environments}, volume = {60}, number = {4}, year = {2005}, month = {March 1, 2005}, pages = {627-646}, abstract = {

Arthropods living in the canopies of two woody shrub species (a sub-shrub (Gutierrezia sarothrae) and a large shrub (Prosopis glandulosa)) and perennial grasses plus associated herbaceous species, were sampled on 18, 0.5 hectare plots in a Chihuahuan Desert grassland for five consecutive years. Mesquite shrubs were removed from nine plots, six plots were grazed by yearling cattle in August and six plots were grazed in February for the last 3 years of the 5 year study. Arthropod species richness ranged between 154 and 353 on grasses, from 120 to 266 on G. sarothrae, and from 69 to 116 on P. glandulosa. There was a significant relationship between the number of families of insects on grass and G. sarothrae and growing season rainfall but species richness was not a function of growing season rainfall on any of the plants. Several of the arthropod families that were the most species rich in this grassland were found on all of the plants sampled, i.e. Salticid spiders, Bruchid and Curculionid beetles, Cicadellid and Psyllid homopterans, and ants (Formicidae). There were more species rich families that were shared by grasses and the sub-shrub G. sarothrae than with mesquite. The absence of a relationship between growing season rainfall and species richness was attributed to variation in life history characteristics of arthropods and to the non-linear responses of annual and perennial desert grassland plants to rainfall.

There were no significant differences in insect family or species richness on any of the plant types as a result of removal of mesquite (P. glandulosa) from selected plots. Intense, short duration (24\ h) grazing by livestock during in late summer resulted in reduced species richness in the grass-herb vegetation layer but had no effect on insect species richness on snakeweed or mesquite shrubs. Livestock grazing in winter had no effect on insect species richness on any of the vegetation sampled.

}, keywords = {arthropods, canopy, Chihuahuan Desert, desert grassland, livestock grazing, species richness}, doi = {10.1016/j.jaridenv.2004.07.004}, url = {/files/bibliography/05-020.pdf}, author = {Gregory S. Forbes and Justin Van Zee and W. E. Smith and Walter G. Whitford} } @mastersthesis {52030, title = {Systematic and ecological studies of the Apodemia mormo complex (Lepidoptera: Riodinidae) in southern Arizona and southern New Mexico}, year = {1981}, note = {//LOCAL//NONE//}, month = {1981}, pages = {83}, school = {New Mexico State University}, type = {M.S. Thesispp}, address = {Las Cruces, New Mexico}, abstract = {Population samples of the polytypic riodinid butterfly Apodemia mormo from the southwestern United States and northern Mexico were studied to determine the distribution of phenotypic variation. In all, 1,813 specimens from 103 locales were examined; 464 specimens were used in cluster and discriminant analysis procedures. The study revealed a highly diverse assemblage consisting of latitudinal and attitudinal clines, polytopic races, complex intergrade zones, and extensive individual variation. Variation present in the study area (southern Arizona to western Texas) was compared with variation patterns on California, Colorado, and Baja California populations. Intergrade zones are interpreted as possibly the result of local intermediacy in selective factors rather than physical contact of adjoining races. Gene flow appears to be greatly restricted among neighboring populations in the region of intergradation. Variation in A. mormo may be determined by such factors as thermoregulation, cryptic coloration, and foodplant associations. The role of historical selective factors is also acknowledged, as is the possibly nonadaptative nature of the color patterns due to pleiotropy. The polytopic nature of the insect, in which distant populations produce the some phenotypes, is evidence against the complex consisting of more than one species throughout most of the range. In a few cases, it is possible that local temporally or ecologically isolated populations (such as those seperated by foodplant preference) may be reproductively isolated species or sibling species.}, keywords = {Apodemia,ecology of, Apodemia,phenotypic variation, butterfly,SEE , dissertation, dissertations, invertebrate, Apodemia,systematics, Lepidoptera,Apodemia, theses, thesis}, author = {Gregory S. Forbes} }