Data from: A single evolutionary innovation drives the deep evolution of symbiotic N2-fixation in angiosperms

Symbiotic associations occur in every habitat on earth, but we know very
little about their evolutionary histories. Current models of trait
evolution cannot adequately reconstruct the deep history of symbiotic
innovation, because they assume homogenous evolutionary processes across
millions of years. Here we use a recently developed, heterogeneous and
quantitative phylogenetic framework to study the origin of the symbiosis
between angiosperms and nitrogen-fixing (N2) bacterial symbionts housed in
nodules. We compile the largest database of global nodulating plant
species and reconstruct the symbiosis’ evolution. We identify a single,
cryptic evolutionary innovation driving symbiotic N2-fixation evolution,
followed by multiple gains and losses of the symbiosis, and the subsequent
emergence of ‘stable fixers’ (clades extremely unlikely to lose the
symbiosis). Originating over 100 MYA, this innovation suggests deep
homology in symbiotic N2-fixation. Identifying cryptic innovations on the
tree of life is key to understanding the evolution of complex traits,
including symbiotic partnerships.