Abstract Detail

Ecological Section

Marchini, Gina [1], Cruzan, Mitchell B. [2].

Adaptive genetic differentiation during the lag phase of a newly invasive bunchgrass (Brachypodium sylvaticum).

The potential for rapid evolution in invasive species makes them a useful tool for studying adaptive responses of populations introduced to new environments. While the possibility of rapid evolution in invasive plants has been well documented, few studies have investigated the point in the invasive process where adaptation to the novel environment takes place. Lag phases, the period between species introduction and invasion, are a common phenomenon assumed to be a time of slow demographic growth where selection results in necessary environmental adaptations before vigorous population spread occurs. However, detecting lag phase adaptation in wild populations is difficult. We used common garden experiments and QST-FST comparisons examining the divergence of quantitative traits and neutral molecular markers to identify evolutionary patterns of phenotypic adaptation during the lag phase and subsequent range expansion of the invasive bunchgrass slender false brome (Brachypodium sylvaticum; Poaceae). Thirteen morphological and physiological traits were selected for quantification based on climate matching between the dry summer season of B. sylvaticum’s invasive range in Oregon, US, and the mild Maritime climate of the species’ native range in Northern Europe. We investigated phenotypic adaptation during the lag phase by integrating the genetic probability of contribution from native source regions into QST-FST comparisons between native and invasive B. sylvaticum populations. Separate QST-FST analyses were performed for invasive populations to investigate additional trait divergence during invasive range expansion. QST-FST comparisons found phenotypic divergence greater than neutral expectations in 5 traits between native and invasive populations, indicating selective divergence had occurred during invasive species establishment. Adaptive differentiation in quantitative traits was not present among populations in the invasive range. Results show that adaptive divergence occurred after introduction to the novel environment but prior to invasive range expansion, and that trait differentiation among invasive populations is the result of a selectively neutral process such as genetic drift. This study provides evidence for adaptive genetic differentiation occurring during the lag phase of an invasive species, while also providing a method for detection of selective processes after species introduction to a novel environment.

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 sylvaticum
poaceae
invasive species
ecological genetics
Qst-Fst.

Presentation Type: Oral Paper:Papers for Sections
Session: 9
Location: Salon 17/18/The Shaw Conference Centre
Date: Monday, July 27th, 2015
Time: 9:30 AM
Number: 9005
Abstract ID:322
Candidate for Awards:Ecological Section Best Graduate Student Paper