Introduction In this exercise we attempted to determine the area one has to sample before adequately representing the community of plants and arthropods in the local biome. This is important in order to measure the biodiversity of the local biome. The Local Biome of the Sonoran Desert Module 2:

Methods We conducted our study within a total plot area of 64 square meters within the Biosphere 2 Campus, which is located in an area referred to by Tony Burgess as the “Apacherian Scrub-Savanna” habitat in the Arizona Upland region of the Sonoran desert biome. We started with a four square meter plot of sloping desert terrain and then doubled the area four times until we covered a total area of 64 square meters. This gave us a total of five plots. Thereby, we examined the rate of increase of plant species and arthropod morphotaxa with increasing plot size. To collect the arthropods we placed a beating sheet underneath plants and used an aluminum rod to expel the arthropods from the plants on to the sheet. We then proceeded to collect the arthropods in vials with aspirators. We also captured arthropods in vials with the use of our hands. We then used dichotomous keys and field reference books to identify the arthropods. To record the plant species we gathered branches and leaves from plant samples and also examined the intact plants on the ground. We used dichotomous keys to identify the cacti and field reference books to identify the other plants. Finally, we examined the data collected using Microsoft Excel spreadsheets and graphs.

Methods (cont’d)

Results of Plant Research The plotted area examined was found to contain a total of 14 different species of woody-stemmed plants and succulents, although one species of Cholla was not conclusively identified. The total plant species were graphed against the area examined to produce a species- area curve, and a logarithmic trend was created. The total species within the plot were compared to the 2000 data graphically. The results are as follows:

List of Collected Plant Morphotaxa in Sample Area Calliandra eriophylla Opuntia chlorotica Mammillaria microcarpa Salsola kali Eriogonum Fouquieria splendens Bebbia juncea Opunita engelmannii Casia covesii Acacia greggii Opuntia acanthocarpa Ambrosia Hibiscus denudatus Unknown small cholla

Discussion: Plant Biodiversity of Sample Area The data collected at the Biosphere 2 Center site during 2001 indicate a logarithmic relationship between plot area and the total number of plant species found within the plots. Within a 64 square meter area, a total of fourteen different plant species were recorded. In comparison, in the year 2000, 19 total species were identified within a 256 square meter plot. The data from the current year showed 8 species that were not found in the data last year, and a total of 13 species that were found in the previous year that were not found this year. The relationship between area and total number of plant species is consistent within the two sets of data despite significant differences in plot size. The collection and comparison of the two datasets within the Sonoran desert biome indicates a rich diversity of plant species despite the size of a small plot sampling. Even though the area examined in the previous year was much greater than the area sampled in 2001, there were species that were not present within the larger plot, but were identified within the smaller. This observation would reinforce the variability of a biome not necessarily being dependent upon the size of the area studied.

Results of Arthropod Research In the four square meter plot, plot 1, we found seven arthropod morphotaxa. In the eight square meter plot we found two more unique arthropod morphotaxa. In the sixteen square foot plot we found eight more arthropod morphotaxa, in the 32 square foot plot we found 12 more arthropod morphotaxa, and in the sixty-four square foot plot we found eight more morphotaxa. The total number of arthropod morphotaxa we found is 37.

List of Collected Arthropod Morphotaxa white Hemiptera, black stripes on back with two orange stripes Very small green six legged with wings and two red dots Small black ant (order Hymenoptera family Formicidae) Larger light brown ant (order Hymenoptera family formicidae) Tan walking stick (order Orthoptera family Phasmatidae) Fly with glossy black abdomen (order Diptera) White moth 1cm (order Lepidoptera) Male Cicada {Western or Apache} orange coloration on wings (order Homoptera family Cicadidae) Reddish brown Homoptera with a black bottom Tiny red ant (order hymenoptera family fomicidae) A black and gray Orthoptera with tan stripes on hind legs Small Hemiptera with black bottom Flying black Termite (order Isoptera) Irridescent green fly Largest Hemipetra with yellow coloration near head and solid green back White Hemipetra, with darker more intense oragne and black Small Fly (order Diptera) Grayish white inch-worm White body black head spider (order Araneida) Wolf spider (order Araneida family Lycosidae) Small ant with white tip Black and red Earwig {Order Dermaptera} Bush cricket (order Orthoptera family Grillidae) Gnat (order Diptera) Orange winged Hemipetra Velvet mite (order Acarina family trombidiidae) Beetle (order Coleoptera) Termite (order Isoptera) Large spider with white body and black head (order Araneida) Homoptera with black body and a white head A large winged green hemiptera Small black, white, and yellow hemitera Dung Beetle {Order Coleoptera; family Scarabaeidae} Flea {Order Siphonaptera} A white wolf spider (order Araneida family Lycosidae) Large flying unkown insect Brown homoptera

Discussion: Arthropod Biodiversity of Sample Area In the 64 square meter area studied at the Sonoran Desert Biome in 2001, a total of 37 arthropod morphotaxa were identified. The 2000 SEE-U group covered a total area of 256 square meters and identified a total of five arthropod morphotaxa. The two studies were conducted at a similar site and time of day, but ten months apart. The 2001 SEE-U class found over seven times as many species in a significantly smaller area. One possible reason for this observation could be the fact that the 2000 SEE-U class did their in the beginning of August, and the 2001 class did their research in the beginning of June. In the summer of 2000 the monsoon season came in the beginning of June, so that although the 2000 group had more recent periods of rain, both studies were done during dry periods. The time seperation from heavy rains could have affected the amount of arthropod morphotaxa found. Additionally, both groups could have erred in their identification of arthropod morphotaxa. Nonetheless, we feel that the main reason behind the discrepancy in the findings of total arthropod morphotaxa between the two years is effort level. Last summer’s group only had two individuals searching for arthropods and they did not search extensively through detritus. This summer’s group had four people searching for and identifying arthropods, and did extensive searching through detritus, and thereby, found many morphotaxa. This difference is most clearly seen upon examining the 32 square meter plots from each study. Last year’s team found 4 morphotaxa, and in this plot this year’s team found 29.

Conclusion to Module 2: Plant and Arthropod Biodiversity for Sample Area in Sonoran Desert Highlands Biome. How much area is necessary to adequately characterize a biome? In particular, in a diverse biome, like the Arizona Highlands of the Sonoran Desert, how much area must be sampled to accurately represent a biological community? It is a well-established principle of community ecology that the number of species discovered in a biome is directly proportional to the area sampled. The purpose of this study was to investigate this relationship. The crux of the matter is that as large as a sample area one may take, there will always be species that are not represented; at what point (even on a graphic scale) does this relationship reach some kind of equilibrium and allow the researcher to categorize the biome? Over the course of this exercise, seven SEE-U students analyzed a 64 square meter area on a south-facing hillside in the Sonoran desert in the area of Biosphere 2. Using the methodology described above, we sampled 37 morphotaxa, and 14 species of plants, plotting the result over the area examined. If one just considers this summer’s arthropod morphotaxa data, one cannot come to a meaningful conclusion as to what area one has to sample before adequately representing the community of plants and arthropods in the local biome. If one extrapolates our curve there is a relative leveling off point of the number of morphotaxa found per area at about 300 square meters, but, because many more morphotaxa were being found with each new plot, clearly, more work needs to be done. However, when one considers the plant species data gathered, one can observe a more conclusive relationship between the species found and the area sampled. Based upon the species composition of the smaller vs. larger area, it would appear that a larger area supports slightly higher number of species. But, this is not to conclude that a smaller area is less diverse, as there were several species represented within the smaller plot that were not identified within the larger area.

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