Joss R. Wertz and Dr. C. Riley Nelson, Biology
Mongolia is as large as the eastern United States with the lowest population density in Asia. This has kept development and its effects at a minimum. Thus, Mongolia retains much of the biota that has been lost in the surrounding countries. In the past 15 years, Mongolia has begun the difficult process of transitioning to a free market system. With this transition have come many pressures to exploit Mongolia’s extensive natural resources, while the number of scientists to monitor the effects of these developments is small. These pressures make an immediate need for biomonitoring methods to be developed. In addition, little research has been done to catalogue and monitor fly species in Mongolia.
We traveled to Mongolia for one month during July of 2008 as part of an expedition with the Mongolia Aquatic Insect Survey team (MAIS). The MAIS is an organization dedicated to cataloging the insect biodiversity of Mongolia and training native researchers in these methods.
Materials and Methods
We collected insects at 33 sites over 20 days in the Bayan Olgii Aimag, the westernmost province in Mongolia. An hour and a half was spent at each selected site, and each site was in conjuncture with the MAIS sites. Specimens were captured using pan-traps. “Pan-traps” are plastic, florescent-yellow bowls filled with water and soap. 22 pans were laid along the shore of a stream or river at five meter intervals and left for one hour. At the end of the hour, insects were retrieved from the pans and specimens from each pan preserved in a vial containing 70% ethanol solution. Each site produced one vial per pan-trap. At each sampled location levels of erosion and grazing were also taken by MAIS researchers.
Data Analysis
Flies were identified to family. To evaluate if the number of samples were sufficient enough, an accumulation curve was run with Sobs Mau Tau and estimators Sobs 95% Lower and Upper, ACE, ICE, and Chao 1 using the program EstimateS (Colwell, 2005). Shannon-Wiener (H) and Simpson’s (1-D) indices were used to calculate diversity. Ubiquitous and singleton groups were removed. Ubiquitous group consisted of Chironomidae and Muscidae while singletons were Conopidae, Heleomyzidae, Lonchopteridae, Pipunculidae, Tabanidae, and Trichoceridae. These groups were removed to provide a greater resolution on the groups which are affected by grazing and erosion. The ubiquitous families were at each site while the singletons were only each at one site. These groups don’t represent any statistical significance to the effects of pressures we are examining. The abundance data of the remaining families were square root transformed to attain normality. Community similarity between sites was assessed using Bray-Curtis similarity. Correlations (the explanatory power of various classifications) were analyzed using MDS, ANOSIM, and Cluster analysis using the program Primer. Erosion and grazing measurements from the sites were averaged into a single variable “impact.” Values from one to one and a half were placed into a “low impact” category while values from two to three were placed into a “high impact” category. To evaluate if the number of samples were sufficient, an accumulation curve was run with Sobs Mau Tau and estimators Sobs 95% Lower and Upper, ACE, ICE, and Chao 1 using the program EstimateS (Colwell, 2005).
Results
In total, 7,325 flies from 714 pan-traps were identified to 38 families using the “Manual of Nearctic Diptera” (McAlpine et al., 1981). Accumulation and estimator curves approached saturation after ten sites. The estimator with the highest value was Sobs Upper 95% at 45. There were 23 low impact sites and nine high impact sites. Low and high impact sites were significantly different at a p-value of 01. Compared to low impact sites, high impact sites showed less diversity than low impacted sites.
Discussion
The traps approached saturation after ten sites, indicating that the study exceeded the necessary traps by three times the needed amount. Efficiency was maximized at fewer than eleven sites. In future studies, where time is a significant factor, researchers may choose to use ten sites when studying the diversity of an area and capture the majority of the fauna capable with the pan-trapping method.
Sites less affected by erosion and grazing have greater diversity compared to locations altered by such activities. One hypothesis is that grazing potentially depresses Diptera diversity by removing habitat niches. This affects less tolerant groups that cannot handle the added stress.
There was no data on the level of grazing and erosion before we explored these areas. With the current data available, another study could be conducted with equal numbers of high and low impacted sites. The impact of the environmental and human pressures could be evaluated in a more quantitative way, in which correlations could be drawn to certain groups which are common in low impact sites but drop out at high impact sites. These groups could be used as bioindicators. Currently, there is a significant push to use aquatic insects in Mongolia to measure stream health and train Mongolians to identify and manage water quality in a self- sustaining way. These same volunteers could also learn to identify terrestrial insects, such as the bioindicator fly groups that the proposed study would provide. These tools, in addition to many others that are being provided, will help in the effort to assist Mongolia in becoming self- sufficient in their goal of sustaining their natural resources.
References
- Colwell, R. K. (2005). EstimateS: Statistical estimation of species richness and shared species from samples. Version 7.5. User’s Guide and application published at: http://purl.oclc.org/estimates.
- McAlpine, J. F., B. V. Peterson, G. E. Shewell, H. J. Teskey, J. R. Vockeroth, and D. M. Wood (1981) Manual of Nearctic Diptera. Hull, Quebec Canadian Government Publishing Center.