The modern distribution of chironomid sub-fossils (Insecta: Diptera) in Costa Rica and the development of a regional chironomid-based temperature inference model

Chironomids have been shown to provide robust reconstructions of past temperature change and variability. This is the first study to assess the contemporaneous relationship between the distribution of sub-fossil chironomids and limnological and climatic parameters in Central America. Here, we describe the distribution of chironomids in a suite of 51 lakes in Costa Rica. We identify environmental variables that account for a statistically significant amount of variance in midge distribution, and develop a quantitative chironomid-based inference model for mean annual air temperature (MAT). Psectrocladius, which is documented for the first time in Costa Rica, dominate high-elevation lakes characterized by low MAT and relatively dilute water. Canonical correspondence analysis (CCA) revealed that MAT and conductivity account for large, statistically significant amounts of variance in the distribution of chironomids. A chironomid-based inference model for MAT, developed using a partial least squares approach, provided robust performance statistics with a high coefficient of determination and a relatively low root-mean square error. Application of the chironomid-based inference model for MAT to chironomid stratigraphies spanning the Holocene, together with the ecological information provided by this study, will enable us to address many outstanding questions relating to long-term climate and environmental change in the region.