The Gondwanan connection – Southern temperate Amanita lineages and the description of the first sequestrate species from the Americas

Abstract

Amanita is a diverse and cosmopolitan genus of ectomycorrhizal fungi. Although most species fruit aboveground, some sequestrate taxa have been documented from Australia and the Mediterranean region. We describe A. nouhrae sp. nov., a new hypogeous (truffle-like) species associated with Nothofagus antarctica in northern Patagonia. This constitutes the first report of a sequestrate Amanita from the Americas. Thick-walled basidiospores ornamented on the interior spore wall (crassospores) were observed consistently in A. nouhrae and its sister epigeous taxon A. morenoi. A. morenoi is a rarely collected but apparently common species from northern Patagonia that has sometimes been misidentified as the Australian taxon A. umbrinella. Nuclear 18S and 28S ribosomal DNA and mitochondrial 16S and 26S DNA placed these two species in a southern temperate clade within subgenus Amanita, together with other South American and Australian species. Based on a dated genus-level phylogeny, we estimate that the southern temperate clade may have originated near the Eocene/Oligocene boundary (ca. 35 Ma ± 10 Ma). This date suggests a broadly distributed ancestor in the Southern Hemisphere, which probably diversified as a result of continental drift, as well as the initiation of the Antarctic glaciation. By comparison, we show that this clade follows an exceptional biogeographic pattern, within a genus otherwise seemingly dominated by Northern Hemisphere dispersal.