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Species in the genus Sphagnum create, maintain, and dominate boreal
peatlands through ‘extended phenotypes’ that allow these organisms to
engineer peatland ecosystems and thereby impact global biogeochemical
cycles. One such phenotype is the production of peat, or incompletely
decomposed biomass, that accumulates when rates of growth exceed
decomposition. Interspecific variation in peat production is thought to be
responsible for the establishment and maintenance of ecological gradients,
such as the microtopographic hummock-hollow gradient, along which
sympatric species sort within communities. This study investigated the
mode and tempo of functional trait evolution across 15 species of Sphagnum
using data from the most extensive studies of Sphagnum functional traits
to date and phylogenetic comparative methods. We found evidence for
phylogenetic conservatism of the niche descriptor height-above-water-table
and of traits related to growth, decay, and litter quality. However, we
fail to detect the influence of phylogeny on interspecific variation in
other traits such as shoot density and suggest that environmental context
can obscure phylogenetic signal. Trait correlations indicate possible
adaptive syndromes that may relate niche and its construction. This study
is the first to formally test the extent to which functional trait
variation among Sphagnum species is a result of shared evolutionary
history.
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