Title: Phylogenetic structures of the environmental niches of phytoplankton: Diatoms vs. dinoflagellates
Authors: Zhi-Ping Mei - Dalhousie University (Canada) [presenting]
Andrew Irwin - Dalhousie University (Canada)
Zoe Finkel - Dalhousie University (Canada)
Abstract: Niche differences among phyla of phytoplankton are well known, but less is known about niche differentiation within phyla. Ecological niches of phytoplankton collected at Gullmar time series station (Sweden) during 1989 through 2014 were modelled with MaxEnt. Phylogenetic principal component analysis and variance decomposition of niches across the phylogenetic tree were conducted to study phylogenetic signal of niche differentiation of diatoms and dinoflagellates, determining the extent to which niches are conserved across the phylogenetic tree of the two functional groups. There is clear distinction in niches between diatoms and dinoflagellates, with diatoms in lower temperature, shorter daylength, weaker water column stratification, and higher nutrient niches than dinoflagellates, with the exception that Gymnodiniales of dinoflagellates share similar range of ecological niches with diatoms. Nutrient and physics niches tend to be conserved within two functional groups of diatoms and dinoflagellates. Within each group, different niche variables diverged at different nodes at the lower taxonomic levels of the phylogeny. On average, 15 - 40\% of the variation in niche means across species is determined by phylogenetic branches older than subclasses for diatoms, or orders for dinoflagellates. Niche divergence at different nodes of the phylogenetic tree is consistent with the evolution of ocean environment throughout the evolutionary history of diatoms and dinoflagellates.