Invertebrate Distribution and Diversity Assessment at the U. S. Army Pinon Canyon Maneuver Site A report to the U. S. Army and U. S. Fish and Wildlife Service G. J. Michels, Jr., J. L. Newton, H. L. Lindon, and J. A. Brazille Texas AgriLife Research 2301 Experiment Station Road Bushland, TX 79012 2008 Report Introductory Notes The invertebrate survey in 2008 presented an interesting challenge. Extremely dry conditions prevailed throughout most of the adult activity period for the invertebrates and grass fires occurred several times throughout the summer. By visual assessment, plant resources were scarce compared to last year, with few green plants and almost no flowering plants. Eight habitats and nine sites continued to be sampled in 2008. The Ponderosa pine/ yellow indiangrass site was removed from the study after the low numbers of species and individuals collected there in 2007. All other sites from the 2007 survey were included in the 2008 survey. We also discontinued the collection of Coccinellidae in the 2008 survey, as only 98 individuals from four species were collected in 2007. Pitfall and malaise trapping were continued in the same way as the 2007 survey. Sweep net sampling was discontinued to allow time for Asilidae and Orthoptera timed surveys consisting of direct collection of individuals with a net. These surveys were conducted in the same way as the time constrained butterfly (Papilionidea and Hesperoidea) surveys, with 15-minute intervals for each taxanomic group. This was sucessful when individuals were present, but the dry summer made it difficult to assess the utility of these techniques because of overall low abundance of insects. Apiformes that were observed during the surveys were collected in addition to the target groups. This report should be used in conjunction with the 2007 report for detailed descriptions of the habitats, collection techniques and the selection criteria for these habitats. We included information vital to 2008 results, but detailed collection and identification methods have not changed significantly from the 2007 report. This report includes information about changes in the 2008 techniques and the results of the 2008 surveys. Data tables are similar in format to the 2007 report to facilitate comparisions between the years. 2008 Results Low numbers of individuals were collected, even with an increased effort by incorporating Asilidae and Acrididae surveys. Collecting techniques employed in both 2007 and 2008 resulted in a decrease in the abundance and richness of the invertebrates collected. We primarily attribute these differences to the lack of precipitation and overall low availabilty of resources available for invertebrates. Invertebrate communities are resiliant and are adapted to climatic conditions that fluctuate. Dormancy of an insect may occur when conditions are not ideal, which would explain the low numbers collected. We collected or observed 6,715 insects in our five target groups. A list of techniques used is in Table 1. The addition of Acrididae and Asilidae surveys made little impact on the collection techniques. This is attributed to climatic issues and not sampling tehcniques, so we will use the same sampling procedures in 2009. If more food and water resources are available in the 2009 collection year, we will be able to accurately assess the techniques’ utility. Table 1: Quick reference table of collection techniques used in 2008. Collection Techniques Used in the Habitats For each habitat, excluding the saltcedar site, we collected the following samples: 1. Nine pitfall traps collected every two weeks continuously from June 6 to October 11 2. One malaise trap collected every two weeks from June 6 to August 21 3. A butterfly, Orthoptera and Asilidae survey consisting of 3 observers walking a haphazard path through a habitat for 15 minutes once every other week. The saltcedar site was a small, dense area, limiting the sampling invertebrates to pitfall trapping. Taxa Results We observed 356 butterflies in 2008 compared to 1,724 in 2007 during the butterfly surveys. The Orthoptera showed a similar decrease with 2,749 in 2008 compared to 9,509 in 2007, even though observation and identification efforts were increased by hand collecting. Carabidae were less abundant; 2,630 in 2008 compared to 4,694. Apiformes collection increased from 101 to 201 individuals. Even with the effort increase by hand collection, the trapping method that yielded the most individuals was pitfall collection. Pitfall collection accounted for 192 of the individuals collected. It is unusual for Apiformes to be collected by pitfall traps in large numbers, and we are unsure what is attracting them to the traps. An increased number of Asilidae were collected compared with last year; 295 in 2008 compared to 76 in 2007. Pitfalls collected 282 of the Asilidae from 2008. Similar to Apiformes, we increased our sampling effort with surveys, but pitfall trapping collected the most individuals. There are several things that may explain why the Asilid capture increased. First, Asilidae may exhibit a preditor lag effect, driven by the assumed subterranian preditory habit of the larvae. Larval habits of most Asilids have not been studied because of their subterranian habitat. The increase in the collection of adults in 2008 may reflect this increase in larval food supply in the 2007 larval development period. Also, drier conditions may allow Asilids to pupate and emerge more sucessfully. Finally, like the Apiformes, Asilidae may be attracted to the pitfall traps for some reason we do not fully understand. With water in short supply, the insects may mistake the propylene glycol for water. Statistical analyses were performed for each target group. Butterflies appeared to be the most senstive to the drought. The frequency of no butterflies recorded per collection period greatly increased, shifting the distribution of data toward zero. The frequency of no Orthoptera recorded also increased, slightly shifting the distribution of data toward zero. In both cases the total numbers collected, the total species and the total diversity collected decreased. Evenness of species was also changed with 2007 being more even than 2008 for both butterflies and Orthoptera, indicating that the communities were less stable. The skewdness of the 2008 data reduces the ability to statistically compare 2007 to 2008 with traditional statistical methods because the populations are very different. Shifts in the composition of the community are evident in the order of porportional species abundances (Fig. 1-9). Both Orthoptera and butterflies are dependent on primary plant production to carry out their life cycle and may remain dormant in periods like 2008 where adequate plant supplies are not available. The species composition of the communities also changed drastically. The species that dominated a community shifted with the general trend being a more diverse group of species making up the top 75% of individuals collected. Even in groups with little increase in the number of species contained in the top 75%, there was a change in ranking of the most dominant species. Apiformes, Asilidae, Carabidae and butterflies all had a very different community structure in 2007 than in 2008 (Fig. 10-15). Orthoptera had a very similar structure, but tended to be dominated exclusively by crickets or camel cricket species (Fig. 14). Acrididae (grasshoppers) showed a similar trend to the other taxa when compared without other members of Orthoptera (Fig. 15). The drastic extremes in climate may allow all these closely related species to co-exist, allowing certain species to prosper at a time when conditions are detrimental to another. Fig. 1 Most abundant Apiformes species calculated as a proportion of the total abundance of Apiformes in the collection period. Pinon Canyon Maneuver Site, 2008. Fig. 2 Least abundant Apiformes species calculated as a proportion of the total abundance of Apiformes in the collection period. Pinon Canyon Maneuver Site, 2008. Fig. 3 Most abundant Carabidae species calculated as a proportion of the total abundance of Carabidae in the collection period. Pinon Canyon Maneuver Site, 2008. Fig. 4 Least abundant Carabidae species calculated as a proportion of the total abundance of Carabidae in the collection period. Pinon Canyon Maneuver Site, 2008. Fig. 5 Asilidae species abundance calculated as a proportion of the total abundace of Asilidae in the collection period. Pinon Canyon Maneuver Site, 2008. Fig. 6 Butterfly species abundance calculated as a proportion of the total abundance of butterflies in the collection period. Pinon Canyon Maneuver Site, 2008. Fig. 7 Most abundant Orthoptera species calculated as a proportion of the total abundance of Orthoptera in the collection period. Pinon Canyon Maneuver Site, 2008. Fig. 8 Moderately abundant Orthoptera species calculated as a proportion of the total abundance of Orthoptera in the collection period. Pinon Canyon Maneuver Site, 2008. Fig. 9 Least abundant Orthoptera species calculated as a proportion of the total abundance of Orthoptera in the collection period. Pinon Canyon Maneuver Site, 2008. Fig. 10 Apiformes dominant species comparison between 2007 and 2008. Each species as a percentage of the entire taxa. Pinon Canyon Maneuver Site, 2008. Fig. 11 Carabidae dominant species comparison between 2007 and 2008. Each species as a percentage of the entire taxa. Pinon Canyon Maneuver Site, 2008. Fig. 12 Asilidae dominant species comparison between 2007 and 2008. Each species as a percentage of the entire taxa. Pinon Canyon Maneuver Site, 2008. Fig. 13 Butterfly dominant species comparison between 2007 and 2008. Each species as a percentage of the entire taxa. Pinon Canyon Maneuver Site, 2008 Fig. 14 Orthoptera dominant species comparison between 2007 and 2008. Each species as a percentage of the entire taxa. Pinon Canyon Maneuver Site, 2008. Fig. 15 Acrididae dominant species comparison between 2007 and 2008. Each species as a percentage of the entire taxa. Pinon Canyon Maneuver Site, 2008. The only species of concern observed in 2007, Euphilotes rita (Mattoni, [1966]) was not observed in 2008.