II. Role of surrounding landscape in the numbers of species and species abundance.

We have found that the temporal and spatial heterogeneity of the landscape plays a significant role in regulating the abundance and diversity of insect predators. This can be better understood when for instance, we “intersected” our bio-complexity framework with the life cycle of one of the most important predator groups in agroecosystems: the coccinellid complex. A key feature of the life system of coccinellids is their mobility in the landscape. The coccinellid life system includes congregation in aggregation sites during the winter and sites for feeding and reproduction during the summer. Dispersion from overwintering sites occurs when adults colonize crops in spring, with movement among habitats during the summer, and when adults return to overwintering sites during the fall. Our findings provide insight into the mechanisms that regulate predator species diversity and abundance in agricultural landscapes. For example, during the winter, tree related habitats provide aggregation sites for coccinellid species. The use of these habitats in the landscape depends on tree species, orientation of the habitat to solar radiation, and distance of overwintering sites from the crops. The presence of deciduous habitats in the landscape increases coccinellids species diversity in field crops. Incorporating woody crops (such as Populus) in agroecosystems increases plant diversity in the landscape and provides alternate habitats for predators during the first years of tree growth and development. However, we observed a "succession" of dominant species within the coccinellid complex as Populus aged. The dominant beetle species in young poplar plantations (one to four years) were also dominant in the adjacent field crops. Thereafter, the dominant coccinellid species in poplar were species typical of deciduous habitats. During early spring, adults become active in the overwintering sites. The twelve-spotted ladybird beetle feeds on spring flowers such as the wood anemonae Anemone quinquefolia, spring beauty Claytonia virginica, and dandelion Taraxacum officinale. This provides a burst of energy to sustain dispersal to distant crop systems. During the summer, increased landscape diversity provides more resources for beneficial predators. Coleomegilla maculata lengi populations prefer alfalfa or wheat during spring but switch to corn during late summer. We observed that corn-soybean rotation affects the composition of the coccinellid community. Coleomegilla maculata lengi was the dominant species in corn whereas and Coccinella septempunctata was dominant in soybean. In wheat we observed that of the two most abundant species in the KBS landscape Coleomegilla maculata lengi prefers simple habitats (high input) but Coccinella septempunctata responded favorably to the most diverse treatment (zero input). Succession habitats provide alternate shelter and food sources to predators during the summer. We found that the optimal level of species diversity and abundance of coccinellids occurs during the second year of plant succession. A higher diversity of predatory species is observed after the sixth year, but the number of individuals is low.

Publications Clark, M.S., Gage, S.H. and Spence, J.R., 1997. Habitats and management associated with common ground beetles (Coleoptera: Carabidae) in a Michigan agricultural landscape. Environmental Entomology, 26: 519-527. Colunga-G., M. S.H. Gage, and L. E. Dyer. 1998. The insect community. In: Cavigelli, M.A., S.R. Deming, L.K. Probyn, and R.R. Harwood (eds.) Michigan field crop ecology: managing biological processes for productivity and environmental quality. Michigan State university Extension Bulletin E-2646: 59-70 Colunga-Garcia, M. 1996. Interactions between landscape structure and ladybird beetles (Coleoptera: Coccinellidae) in field crop agroecosystems. Ph.D. Thesis. Michigan State University Colunga-Garcia, M., S.H. Gage, and D.A. Landis. 1997. The response of an assemblage of Coccinellidae (Coleoptera) to a diverse agricultural landscape. Environ. Entomol. 26: 797-804. Maredia, K.M., S.H. Gage, D.A. Landis, and J.M. Scriber. 1992b. Habitat use patterns by the seven-spotted lady beetle (Coleoptera: Coccinellidae) in a diverse agricultural landscape. Biol. Control 2: 159-165 Maredia, K.M., S.H. Gage, D.A. Landis, and T.M. Wirth. 1992a. Ecological observations on predatory Coccinellidae (Coleoptera) in southwestern Michigan. Great Lakes Entomol. 25:265-270. Ostrom, H.P., Colunga-Garcia, M. and Gage S.H. 1997. Establishing pathways of energy flow for insect predators using stable isotope ratios: field and laboratory evidence. Oecologia 109: 108-113.

Posters Colunga-G, M. and S.H. Gage. 1998. Wooded habitat use by predatory ladybird beetles in an agriculture landscape. United States Regional Association of the International Association for Landscape Ecology. Lansing, Michigan. Colunga-G, M. and S.H. Gage. 2000. Patterns of Abundance of Insect Predators in a Diversified Agricultural Landscape: a 12-year synthesis in the KBS-LTER. Long Term Ecological Research all Scientist Meeting. Snowbird, Utah. Colunga-G, M., M.S. Clark, and S.H. Gage. 1998. Response of predaceous arthropods to habitats and management in an agricultural setting. . Entomological Society of America. Las Vegas, Nevada. Colunga-G, M. and S.H. Gage. 1995. Species assemblages of predatory coccinellids in perennial plantations and early field succession. Entomological Society of America. Las Vegas, Nevada. Colunga-G. M. and S.H. Gage. 1996. Response of a complex of insect predators to habitat aging in an agricultural landscape. Ecological Society of America. Providence, Rhode Island.