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Peat mosses (Sphagnum) are ecosystem engineers— species in boreal
peatlands simultaneously create and inhabit narrow habitat preferences
along two microhabitat gradients: an ionic gradient and a hydrological
hummock-hollow gradient. In this paper we demonstrate the connections
between microhabitat preference and phylogeny in Sphagnum. Using a dataset
of 39 species of Sphagnum, with an 18-locus DNA alignment and an
ecological dataset encompassing three large published studies, we tested
for phylogenetic signal and within-genus changes in evolutionary rate of
eight niche descriptors and two multivariate niche gradients. We find
little to no evidence for phylogenetic signal in most component
descriptors of the ionic gradient, but interspecific variation along the
hummock-hollow gradient shows considerable phylogenetic signal. We find
support for a change in the rate of niche evolution within the genus— the
hummock-forming subgenus Acutifolia has evolved along the multivariate
hummock-hollow gradient faster than the hollow-inhabiting subgenus
Cuspidata. Because peat mosses themselves create some of the ecological
gradients constituting their own habitats, the classic microtopography of
Sphagnum-dominated peatlands is maintained by evolutionary constraints and
the biological properties of related Sphagnum species. The patterns of
phylogenetic signal observed here will instruct future study on the role
of functional traits in peatland growth and reconstruction.
441 views reported since publication in 2014.