Nate Upham

Nate's research focuses on the evolution and diversification of New World rodents in the superfamily Octodontoidea (spiny rats, tree rats, nutria, degus, tuco-tucos, chinchilla rats, and hutias). These are the "native" rats of South America and the Antilles, having arrived on the continent ~40 million years ago likely via overwater dispersal from Africa. In comparison, the "immigrant" group of mice and rats (subfamily Sigmodontinae) arrived in South America starting ~9 million years ago at the beginning of the Great American Biotic Interchange. Nate is interested in the interactions between these two diversifying lineages of rodents in South America, and how their differences and similarities in history and ecology have influenced their presently disparate diversity patterns (193 living species of octodontoids vs. 421 species of sigmodontines). The exceptional fossil record of Octodontoidea adds an important element to Nate's research — the dimension of time. The 89 known fossil genera span a period of 24.5 million years, and greatly assist in determining the timing and rates of evolutionary change in this rodent group. Nate uses fossil data in combination with DNA sequences and morphological measurements (body size and shape traits) to uncover patterns of diversification over geography and in relation to past geologic events. By studying how these ecologically diverse rodents have evolved, this research aims to illuminate broader mechanisms shaping the evolution of biotas in temperate, tropical, and montane South American environments. Understanding the relative roles that abiotic factors (climate and environment) and biotic factors (species interactions) play in the evolutionary theatre is acutely critical today as the worst scenarios of global climate change, habitat destruction, and biodiversity loss are still preventable. In this regard, environmental education is one Nate's top priorities.