Abstract Detail

Ecological Section

Marchini, Gina L [1], Maraist, Caitlin [1], Williamson, Michelle N. [1], Cruzan, Mitchell B [2].

Enhanced drought tolerance in the invasive bunchgrass Brachypodium sylvaticum (slender false brome).

Introduced plants encounter novel climatic conditions in their invasive range, but the physiological processes resulting in a successful invasion are not well understood. Invasive success is thought to be a result of a combination phenotypic plasticity and evolutionary change. Introduction to new environments can expose populations to elevated levels of natural selection, resulting in trait responses that contribute to a successful invasion. We identified evolutionary patterns of phenotypic adaptation in the rapidly spreading grass Brachypodium sylvaticum (Poaceae). This invasive grass has persisted in Oregon’s dry summer season, which contrasts with the mild Maritime climate of its home range. Few studies have compared phenotypic plasticity between invasive populations and their native progenitors in response to variation in water availability. We raised clonal tillers from populations distributed throughout the invasive and native ranges in drought and non-drought conditions for six months. Leaf morphological traits related to water use such as specific leaf area, stomatal density, and xylem morphology were measured and evaluated for their effects on growth, biomass, and inflorescence production. Pressure-volume curves measuring the relationship between water potential and relative water content in dehydrating leaves was measured for 3-6 individuals from each population.            
 
Our results show that variation exists in physiological and morphological characteristics across the native and invasive ranges of B. sylvaticum, although none of the traits measured appeared to be plastic in response to soil moisture availability. Individuals from invasive populations showed characteristics related to drought adaptation such as a greater bulliform cell area within leaves (p=0.0041), greater xylem vessel frequency (p<0.0001), and greater hydraulically weighted xylem diameter (p<0.0001) than plants from the native range. Data from pressure-volume curves found that invasive B. sylvaticum individuals possessed more rigid cells and a lower water potential at turgor loss point (p=0.0143 and p=0.0314, respectively), allowing more efficient water uptake. Our results suggest that moisture may be a component driving physiological change in invasive populations of B. sylvaticum.

1 - Portland State University, Biology, P.O. Box 751, Portland, OR, 97207, USA
2 - Portland State University, Department Of Biology, PO BOX 751, PORTLAND, OR, 97207, USA

Keywords:
Brachypodium
invasive species
ecophysiology
Grass
Pacific Northwest
Drought
Adaptation.

Presentation Type: Oral Paper:Papers for Sections
Session: 10
Location: Firs South/Boise Centre
Date: Monday, July 28th, 2014
Time: 1:45 PM
Number: 10002
Abstract ID:821
Candidate for Awards:Ecological Section Best Graduate Student Paper