Abstract Detail

Bryology and Lichenology

Piatkowski, Bryan [1], Yavitt, Joseph [2], Turetsky, Merritt [3], Shaw, Jonathan [1].

Carbon storage and niche preference track phylogeny in Sphagnum (peat moss).

Boreal peatlands are dominated by Sphagnum peat mosses and have extraordinary impacts on global biogeochemical cycles as these wetlands hold roughly a quarter of all terrestrial carbon in the form of peat, or incompletely decomposed biomass. Sphagnum engineer boreal peatlands through the production of peat, sequestering carbon and allowing these mosses to outcompete other plants while providing unique habitat for a diverse assemblage of life. Interspecific variation in the propensity to form peat, largely driven by variation in tissue decomposability, is hypothesized to promote niche differentiation within peatlands through establishment of microhabitat gradients along which species sort within communities; for example, some species form raised hummocks while others grow in hollows near the water table. However, it is unclear how decomposability evolved during Sphagnum diversification and to what extent natural selection created such species differences. In the largest experiment of its kind to date, we measured litter decomposition rates for over 50 Sphagnum species and competed phylogenetic models of trait evolution. We found that interspecific variation in decomposability measured under natural conditions is phylogenetically conserved within Sphagnum and that selective regime divergence in crown group ancestors coincided with the evolution of niche differentiation along prominent ecological gradients. Species belonging to the predominantly hummock-forming clade, containing subgenera Sphagnum and Acutifolia, produce less decomposable litter than do species in the hollow-dwelling clade comprised of subgenera Subsecunda and Cuspidata. We also highlight several cases within subgenera where selective regime shifts occur concomitantly with habitat transitions. Our results contribute to a recent revival of Dawkin’s ‘extended phenotype’ hypothesis in which organisms modify their environment through artefacts, such as beaver dams, that natural selection then acts through. The discovery of separate adaptive optima for functional traits and associated microhabitat preferences across Sphagnum subgenera represents a singular case for plants in which niche construction and differentiation are promoted via natural selection both among species and in the genus per se. Furthermore, this study demonstrates linkages between phylogenetic relationships, ecological function, and global biogeochemistry.

1 - Duke University, Department of Biology, Campus Box 90338, Durham, NC, 27708, USA
2 - Cornell University, Department of Natural Resources, 111 Fernow Hall, Ithaca, NY, 14853, USA
3 - University of Colorado, Institute of Arctic and Alpine Research, Campus Box 450, Boulder, CO, 80309, United States

Keywords:
Sphagnum
peat moss
phylogenetic comparative methods
extended phenotype
niche construction.

Presentation Type: Oral Paper
Session: BL1, Bryology/Lichenology AJ Sharp Session
Location: Virtual/Virtual
Date: Thursday, July 30th, 2020
Time: 11:15 AM
Number: BL1006
Abstract ID:802
Candidate for Awards:A. J. Sharp Award