Abstract Detail

Molecular Ecology and Evolution

Tyrrell, Christopher D [1], Chambers, Patricia [2].

Trait versus niche conservatism in aquatic plant microhabitat preference.

Vascular plant species inhabiting freshwaters often show an affinity to waterbodies with particular phosphorus concentrations. In Europe, this pattern is exploited for use in surface water assessments where aquatic plants serve as bioindicators of water trophic condition. Rapid population growth of phytoplankton under high nutrient conditions, however, can override these plant-phosphorus affinities. Under these conditions, shading from plankton biomass conveys an advantage to plants with greater access to light. Among aquatic plants, the emergent and surface-floating growth forms are capable of escaping shading and ought to be more prevalent in highly productive habitats, but have species with these growth forms evolved an affinity to waters with higher phosphorus concentrations? I test this tangle of relationships by comparing aquatic plant species with nearctic, palearctic, or holarctic distributions using comparative phylogenetic and experimental approaches. Analyses revealed significant differences in phosphorus affinities among growth forms. Indigenous North American species (those that are nearctic rather than holarctic) are comparable to their palearctic relatives based on their growth forms. In general, submerged forms were associated with oligotrophic (low P concentrations) conditions, while emergent and free floating forms predominated under meso- and eu-trophic conditions (high-P concentrations). Subsequent experimental manipulations of growth form within species, however, demonstrated that submerged forms required more phosphorus per unit biomass than emergents, despite their association with lower phosphorus environments. This result suggests that phosphorus habitat preference may not be conserved among aquatic plants, rather, it is the pattern observed as a consequence of competition for light in high nutrient environments. Light competition is ameliorated by growth form, which is a phylogenetically conserved trait.

1 - Milwaukee Public Museum, Botany Department, 800 W Wells St, Milwaukee, WI, 53233, USA
2 - Environment Canada, Water Science & Technology Directorate, Burlington, ON, L7S 1A1, Canada

Keywords:
aquatic plants
phylogenetic signal
Phenotypic traits
biogeochemistry.

Presentation Type: Oral Paper
Session: 44, Molecular Ecology and Evolution II
Location: 102/Savannah International Trade and Convention Center
Date: Wednesday, August 3rd, 2016
Time: 3:00 PM
Number: 44007
Abstract ID:893
Candidate for Awards:None