"Subspeciation in the Meadow Mouse, Microtus montanus, in Wyoming and Colorado" by Sydney Anderson is a scientific publication written in the mid-20th century. The book focuses on the study of the subspecies of the meadow mouse, specifically Microtus montanus, in the unique ecological regions of Wyoming and Colorado. Through extensive fieldwork and analysis of collected specimens, Anderson explores the variations within the species, influenced by various environmental and geographical factors. In this publication, Anderson examines 1,187 specimens of Microtus montanus collected over several years, detailing the morphological characteristics and measurements of the mice from various localities. The study identifies and describes previously unrecognized subspecies while discussing how geographical barriers and environmental conditions have led to evolutionary variations among isolated populations. It emphasizes the role of moisture and seasonal population fluctuations on the survival and adaptation of these meadow mice, providing significant insights into their ecological niche and evolutionary biology. The findings contribute to a greater understanding of subspeciation and biodiversity within rodent species in North America. (This is an automatically generated summary.)