Aim: Pyrodiversity is the spatial or temporal variability in fire effects across a land- scape. Multiple ecological hypotheses, when applied to the context of post- fire sys- tems, suggest that high pyrodiversity will lead to high biodiversity. This resultant “pyrodiversity– biodiversity” hypothesis has grown popular but has received mixed support by recent empirical research. In this paper, we sought to review the existing pyrodiversity literature, appraise support for the pyrodiversity– biodiversity hypoth- esis, examine potential mechanisms underlying the hypothesis and identify outstand- ing questions about pyrodiversity and future research needs.

Location: Global terrestrial ecosystems.

Methods: We performed a systematic literature review of research related to pyrodi- versity and the pyrodiversity– biodiversity hypothesis. We also examined how two in- dividual species with distinct relationships with fire (spotted owl Strix occidentalis and black- backed woodpecker Picoides arcticus) respond to pyrodiversity as case studies to illustrate underlying mechanisms.

Results: We identified 41 tests of the pyrodiversity– biodiversity hypothesis reported from 33 studies; 18 (44%) presented evidence in support of the pyrodiversity– biodiversity hypothesis, while 23 (56%) did not. Our literature review suggested that support for the pyrodiversity– biodiversity hypothesis varies considerably with no consistent patterns across taxonomic groups and ecosystem types. Studies examining the pyrodiversity– biodiversity hypothesis often define pyrodiversity in different ways, examine effects at dif- ferent scales and are conducted in ecosystems with different natural fire regimes, baseline levels of biodiversity, and evolutionary histories. We suggest these factors independently and jointly have led to widely varying support for the pyrodiversity– biodiversity hypothesis.

Main Conclusions: Clarifying the pyrodiversity– biodiversity hypothesis will be fa- cilitated by stronger development of the different potential mechanisms underlying pyrodiversity– biodiversity relationships, which can be aided by examining how indi- vidual species respond to pyrodiversity. Future research would benefit from a closer examination of the role of scale (e.g. scale dependence) in pyrodiversity– biodiversity relationships, standardization of pyrodiversity metrics, broad- scale mapping of pyro- diversity, and macroecological study of pyrodiversity– biodiversity relationships.