The biogeography of ectomycorrhizal fungi a history of life in the subterranean

The science of biogeography maps spatial patterns of biological diversity as a means of understanding the evolutionary and ecolog­ ical processes that structure life on this planet (Lomolino et al., 2006). Understanding spatial patterns of biodiversity has given rise to some of the most important discoveries in modern science. The unique composition of flora and fauna in different parts of the world, coupled with the spatial and tempo­ ral coincidence of allied species, led both Darwin and Wallace to the idea of evolution by natural selection (Darwin, 1859; Wallace, 1855). Similarly, Wegener’s theory of conti­ nental drift was formulated in great part by the realization that the fossil record pro­ vided a window into the past arrangement of landmasses, precisely because of the s patially restricted nature of species distribu­ tions. Biogeography may not be a field familiar to most lay people or most micro­ biologists, but it is a powerful window into life on this planet. The documentation of basic biogeographic patterns is fundamental to understanding any taxonomic group. Knowing the time or place that an organism first arose and diver­ sified provides a window into the ecological and evolutionary processes shaping their diversity and tells us how they responded to past changes in the environment, or how they might fare under new climates. Yet, for the organisms studied by microbiologists (fungi, bacteria, viruses) and that constitute the majority of life on earth, basic details of biogeography remain poorly known, and are still a subject of debate. Biogeography was one of the earliest branches of plant and animal biology, but the development of microbial biogeography lagged, because the use of morphological systematics to differentiate microbes and reconstruct their evolutionary histories was a “fruitless search”, to quote Carl Woese (Woese, 1987). As a result of the paucity of morphological characters, until very recently many microbes were thought to lack distinct biogeographical patterns (Finlay, 2002; Peay et al., 2010c), and the importance of these organisms to the diversity and function The biogeography of ectomycorrhizal fungi – a history of life in the subterranean