Ecological Memory in Farmed Landscapes: Predicting Distributions of Amphibian Communities in Palouse Prairie Wetlands

Ecological memory is a metaphor for patterns of historical biological diversity and ecological structure and function that can still be detected within modified landscapes, making it a key to understanding possibilities for future ecological restoration in human dominated landscapes.  Palouse Prairie has lost about 97% of its original wetland habitats to intensive farming, and is one of the most endangered grassland ecosystems in North America, making it a useful system for studying conservation of biological diversity in highly modified landscapes. We used data mining techniques to develop ecological models predicting the occurrence of over 4000 amphibian larvae of 8 species captured in 63 wetlands along a geographic gradient extending from the Palouse Prairie bioregion to Moses Lake, Washington. We then used these empirical models to describe the relative importance of historical biogeographic legacies vs. contemporary ecological forces in shaping the occurrence and distribution of amphibian communities in Palouse Prairie.

Our ecological models reveal that only a relatively few environmental variables are needed to predict occurrence of different amphibian species with high accuracy, including: a) presence or absence of introduced fish, b) wetland permanence and landscape context (e.g., surrounded by grasslands, farm fields, or urban areas), and c) broad biogeographic factors (e.g., sandy soils for toads). These models provide evidence for ecological memory and illustrate where wetland restoration and conservation would most beneficially impact several amphibian species of conservation concern, including endangered northern leopard frogs, Columbia spotted frogs, Great Basin spadefoot toads, and tiger salamanders.