Sagehen Creek Field Station

14 May, 04 AM - 29 Jun, 05 PM

Butterfly community composition and habitat factors in montane meadows ABSTRACT The purpose of this study is to identify patterns of butterfly community composition predicted by local and landscape habitat attributes of mountain meadows in the Truckee Ranger District, Tahoe National Forest, in the northern Sierra Nevada, California. Previously, patterns of butterfly community composition and individual butterfly species abundance have been attributed to a variety of habitat characteristics. I propose to examine the importance of relationships of total, resident and non-resident butterfly richness and abundance with local resource attributes (host plant attributes, nectaring plant attributes, vegetation structure) and landscape attributes (vegetation matrix, distance to nearest meadow, and distance to nearest meadow of similar type) in a correlative study using a multiple regression approach. Significant relationships of habitat attributes could indicate the importance of local or landscape attributes in determining butterfly community composition, suggesting directions for future experimental work as well as conservation goals. INTRODUCTION Mobile species are presumed to select habitats based on local attributes of resource availability, competition, and predation, thus shaping the community composition of these organisms. Local resources that provide food and reproduction sites or opportunities have been suggested as important characteristics in habitat selection. However, position of habitat patches in the landscape, such as size of patch, isolation from other patches, and resistance of the vegetation matrix surrounding patches, may have an equally strong effect on shaping community composition. The specific local and regional factors that affect a community are likely particular to the ecology of each taxonomic group. Due to amateur and professional study, much is known about butterfly ecology. For example, the relationship of individual butterfly species to specific food plant species is widely established (Vane-Wright and Ackery 1984, Scoble 1992). Further, a rich resource of natural history data exists on individual species, such as flight periods, species ranges, and life stage of overwintering, readily accessible in field guides. However, less is known about how factors that influence individual species play out in community patterns. Recent work has shown that the composition of butterfly communities is related to local habitat characteristics, in particular plant community characteristics (Erhardt 1985, Erhardt and Thomas 1991, Kremen 1992, Scoble 1992, Simonson et al 2001). Other studies show little or no association between butterfly species richness and plant richness, assumed to be due to various unmeasured factors in those studies, such as composition of vegetation matrix surrounding habitat patches; abiotic factors; or vegetation structure (Sharp et al. 1974, Kremen 1992, Vessby et al. 2001). Researchers have investigated the relationship of particular habitat attributes on butterfly communities in temperate zones, often either local attributes (Sharp et al. 1974, Vessby et al. 2002, Simonson et al 2001, Clausen et al. 2001, Erhardt 1985) or landscape attributes (Baz and Garcia-Boyero 1995, Boggs and Murphy 1997, Ricketts 2000). Few temperate zone studies have investigated the relative importance of both local and landscape attributes in predicting patterns in butterfly species richness, abundance or diversity (Steffan-Dewenter and Tscharntke 1997, Guti?rrez and Men?ndez 1995). In addition, to my knowledge no studies have investigated relationships of butterfly community composition and local resource and landscape factors in montane meadows the Sierra Nevada. I propose to examine the relationship of a suite of local and landscape of habitat factors to patterns of butterfly community composition in mountain meadows in the northern Sierra Nevada, California. Community is defined as all species located within a given area (meadow). However, a distinction will be made between all species that occur in meadows, species that gather resources, reproduce, and reside within meadows (residents), and species that gather resources and perhaps mate in meadows but who reproduce using host plants located outside the selected habitat (non-residents). STUDY QUESTIONS Using a multiple regression approach, I propose to answer the following questions: Community ecology questions Do local resources predict butterfly composition? Does meadow position in the landscape affect butterfly composition? Are local variables better predictors than landscape variables? 1. Is the richness of residents predicted by meadow host plant richness or total plant species richness? Is the abundance of residents predicted by meadow host plant abundance or total plant species abundance? 2. Is the richness of residents predicted by floral resource species richness? Is the richness of non-residents predicted by these variables? Or total butterfly richness? Is the abundance of residents predicted by floral resources abundance? Is the abundance of non-residents predicted by these variables? Or the abundance of all butterflies? 3. Is compositional similarity of resident butterflies predicted by compositional similarity of host plants, of total plant species, or of floral resources? And for non-residents? Total butterflies? 4. Are the richness or abundance of residents predicted by proportion wet vegetation association? Non-residents? Or total butterflies? 5. Are richness or abundance of residents predicted by matrix vegetation (proportion of forest, chaparral/sagebrush, meadow)? Non-residents? Total butterflies? 6. Are richness or abundance of residents predicted by isolation from other meadows? Non-residents? Total butterflies? Conservation and applied questions Is butterfly community composition correlated with habitat degradation? Can results be applied practically for monitoring or assessment? 1. Are resident, non-resident or all butterfly richness or abundance predicted by stream incision measures? Is host plant, floral resource or total plant richness or abundance predicted by stream incision measures? 2. Using a subset of butterfly species that are easy to identify, are results the same as tests using residents or all butterflies? METHODS Overview of Experimental Design Multiple regression tests will be used to examine patterns butterfly community composition and meadow habitat attributes. I will conduct a correlative study of butterfly community attributes (species richness and abundance) with local habitat attributes (host plant richness and abundance, nectaring resources richness and abundance, vegetation height, proportion of vegetation communities, meadow size) and landscape attributes (elevation, vegetation type of surrounding matrix, isolation from other meadows, isolation from similar meadow types). Temporal factors, and numerous other habitat attributes, will not be considered. Study Region The proposed study site is the Truckee Ranger District of Tahoe National Forest (USFS), located in the northern Sierra Nevada mountains of California. The region is east of the crest of the Sierra Nevada, resulting in drier and warmer conditions than the western mountain slopes. Montane meadows occur within a matrix of lodgepole pine forest, chaparral and sagebrush scrub community types, in a range of elevations (approximately 5500-7000 feet). Snowmelt occurs in the region in April or May, and early-flowering plant species and early flight season butterflies have been documented to occur at that time. Estimate of Sample Size Published studies were used to estimate a range of expected r2 values for correlations between butterfly community attributes and habitat attributes. Using calculations from Cohen (1977), effect size was determined, and a matrix was created of estimated sample sizes for given number of independent variables and effect sizes at specified probabilities of Type I (alpha = 0.05) and Type II (power=0.8) errors (see Table 1). Experimental Design I propose the following methods to estimate dependent and independent variables of interest. Each meadow is a sampling unit. Target sample size based on estimated effect size (above) is n=20. Meadow sites will be randomly selected within watersheds of the study region, but road accessibility will be considered in the selection. Over 140 butterfly species have been documented in the study region, compiled from species lists for Placer, Nevada, Sierra and Washoe (NV) counties (Opler unpublished data; Shapiro personal communication; USGS unpublished data). Transects will be established throughout each meadow; number of transects will be scaled according to meadow size to standardize sampling effort (minimum number of transects per meadow to be determined). Transects will be sampled at 2 week intervals throughout the flight season of May 15 to August 15. Transects will be visited and all species and number of individuals observed within 2 m of the transect will be recorded. Where visual identification is not possible, individuals will be captured, identified and released. Sampling will occur under optimal daylight and weather conditions. Voucher specimens will be captured and pinned. Butterfly species will be categorized as resident and non-resident species based on host plants presence in meadow or forest vegetation associations and specialist knowledge. Following data collection, a subset of species that are easy to capture and identify will be selected. I have compiled a list of host plants associated with butterfly species expected to be present the study region (Opler and Wright 1999, Glassner 2001, Shapiro personal communication, Tietz 1972, USGS unpublished data). This list will be cross-referenced with a species list collected in the study region in 2002 by Rich Hatfield (unpublished data) to create a list of expected host plants in the study region. To estimate host plant richness and abundance, meadows will be randomly sampled for host plants of all expected species. Voucher specimens of plant species will be collected. To estimate nectar resources, flowering plant richness and abundance plots will be established along butterfly transects within each vegetation association within the meadow (see below for discussion of vegetation association). Number of plots in each vegetation association will scaled in proportion to vegetation association for all transects within the meadow, in order to standardize sampling effort. Species and number of inflorescences for all flowering plants will be recorded. An estimate of nectar resources for each meadow will be made based on plots and proportion of each vegetation type along transects. To estimate vegetation structure within meadows, nectar resources plots (above) will be sampled for average vegetation height. Using the proportion of vegetation types along transects as an estimate of proportion of vegetation associations within meadows, average vegetation height for the whole meadow will be calculated. The proportion of vegetation associations will be estimated as the portion of each butterfly transect that covers a particular vegetation type. As depth to water table has been tied to different meadow vegetation associations (Allen-Diaz 1991), proportion of vegetation types will be used as a proxy for the wetness or dryness of meadows. The matrix vegetation type will be estimated using GIS and field observation. In the field, matrix vegetation types will be noted and hand-mapped. Using digitized aerial photographs, the proportion of forest, shrub and meadow matrix vegetation will be calculated within a 300 m band surrounding each meadow. Isolation will be calculated as distance to 3 nearest meadows, from meadow edge to meadow edge using GIS. All values will be scaled to nearest value (where nearest value = 1). In addition, isolation from similar meadow types will be calculated, using USFS meadow classifications of wet/dry type and GIS. Meadow size and elevation will also be calculated digitally using GIS. Statistical Analysis Statistical analysis will be performed using SPSS. Multiple regression models will be built and evaluated to test the significance of relationships of total, obligate and non-obligate butterfly species richness and abundance with multiple independent variables. IMPLICATIONS OF RESULTS This study will describe patterns that suggest future experimental tests of underlying mechanisms. A significant relationship of isolation or matrix attributes and butterfly richness or abundance, for example, could suggest an experimental investigation of metapopulation dynamics among different meadows within the region. Similarly, the relative importance suggested of attributes may direct conservation or management actions to local or regional scales. For example, a significant positive relationship of floral resources to butterfly species richness or abundance may suggest the importance of within-meadow management actions, such as grazing intensity. REFERENCES Allen-Diaz, B. 1991. Water table and plant species relationships in Sierra Nevada meadows. American Midland Naturalist 126: 30-43. Baz, A. and A. Garcia-Boyero. 1995. The effects of forest fragmentation on butterfly communities in central Spain. Journal of Biogeography 22:129-140. Berlow, E.L., C.M. D?Antonio, and S.A. Reynolds. 2002. Shrub expansion in montane meadows: The interaction of local-scale disturbance and site aridity. Ecological Applications 12: 1103-1118. Boggs, C.L. and D.D. Murphy. 1997. Community composition in mountain ecosystems: climatic determinants of montane butterfly distributions. Global Ecology and Biogeography Letters 6:39-48. Clary, W.P. and G.D. Booth. 1993. Early season utilization of mountain meadow riparian pastures. Journal of Range Management 46: 493-497. Debinski, D.M., Jakubauskas, M.E. and K. Kindscher. 2000. Montane meadows as indicators of environmental change. Environmental Monitoring and Assessment 64: 213-225. Erhardt, A. 1985. Diurnal Lepidoptera: Sensitive indicators of cultivated and abandoned grassland. Journal of Applied Ecology 22: 849-861. Erhardt. A. and J.A. Thomas. 1991. Lepidoptera as indicators of change in the semi-natural grasslands of lowland and upland Europe. In The Conservation of Insects and Their Habitat. London: Academic Press. Glassberg, J. 2001. Butterflies through Binoculars: The West. Oxford: Oxford University Press. Guti?rrez, D. and R. Men?ndez. 1995. Distribution and abundance of butterflies in a mountain area in northern Iberian peninsula. Ecography 18:209-216. Kremen, C. 1992. Assessing the indicator properties of species assemblages for natural areas monitoring. Ecological Applications 2: 203-217. Lawton, J.H. et al. 1998. Biodiversity inventories: indicator taxa and effects of habitat modification in tropical forest. Nature 391: 72-76. MacNally, R. and E. Fleishman. 2002. Using ?indicator? species to model species richness: model development and predictions. Ecological Applications 12: 79-92. Opler, P. and A. B. Wright. 1999. Western Butterflies. New York: Houghton Mifflin Company. Prendergast, J.R., R.M. Quinn, J.H. Lawton, B. C. Eversham, and D.W. Gibbons. 1993. Rare species, the coincidence of diversity hotspots and conservation strategies. Nature. 365: 335-337. Ricketts, T.H. 2000. II. The matrix matters: effective isolation in a fragmented landscape: biodiversity in native and agricultural habitats. In, Distribution and dispersal of species in natural and human-dominated landscapes. Dissertation, Stanford University. Ricketts, T.H., G.C. Daily, P.R. Ehrlich. 2002. Does butterfly diversity predict moth diversity? Testing a popular indicator taxon at local scales. Biological Conservation 103: 361-370. Scoble, M.J. 1992. Environmental and ecological importance of Lepidoptera. In The Lepidoptera, Form, Function and Diversity. New York: Oxford University Press. Sharp, M.A. and D.R. Parks. 1974. Plant resources and butterfly habitat selection. Ecology 55: 870-875. Simonson, S.E., P.A. Opler, T.J. Stohlgren, and G.W. Chong. 2001. Rapid assessment of butterfly diversity in a montane landscape. Biodiversity and Conservation. 10: 1369-1386. Soderstrom, B., B. Svensson, K. Vessby, and A. Glimskar. 2001. Plants, insects and birds in semi-natural pastures in relation to local habitat and landscape factors. Biodiversity and Conservation. 10: 1839-1863. SNEP (Sierra Nevada Ecosystem Project). 1996. Final Report to Congress: Assessments and Scientific Basis for Management. Vol. 2. Davis: University of California Centers for Water and Wildland Resources. Steffan-Dewenter, I. and T. Tscharntke. 1997. Early succession of butterfly and plant communities on set-aside fields. Oecologia. 109:294-302. Tietz, H.M. 1972. Index to the Described Life Histories, Early Stages and Hosts of the Macrolepidoptera of the Contental United States and Canada. Vols. 1 and 2. Florida:Allyn Museum of Entomology. Vane-Wright, R.I. and P.R. Ackery, eds. 1984. The Biology of Butterflies. London: Academic Press. Vessby, K., B. Soderstrom, A. Glimskar, and B. Svensson. 2002. Species-rich correlations of six different taxa in Swedish natural grasslands. Conservation Biology. 16: 430-439. Table 1. Effect size (f2) (R2) Number of independent variables (u) 0.35 (R2=0.26) 0.82 (R2=0.45) 1 (R2=0.5) 1.5 (R2=0.6) 2.33 (R2=0.7) 4 (R2=0.8) 3 35 * * * * * 5 43 22 19 15 12 9 7 * 26 * * * 12 16 * 41 * * * 22 23 * 52 * * * 30 * Sample sizes for these values of u and R2 were not calculated for simplicity, but could be inferred from other calculations on a relatively linear scale.

Visit #1053 @Sagehen Creek Field Station

Approved

Under Project # 899 | Research

Local and Landscape Factors Influencing the Meadow Butterfly Community

graduate_student - San Francisco State University (CSU)

Reservation Members(s)

Katrina Strathmann May 14 - Jun 29, 2003 (47 days)
Katrina Strathmann May 14 - Jun 29, 2003 (47 days)

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Camping/Lower camp 2 May 14 - Jun 29, 2003
Classroom 2 May 14 - Jun 29, 2003
Lab / Classroom 2 May 14 - Jun 29, 2003
Library / Classroom 2 May 14 - Jun 29, 2003