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Abstract Detail

Molecular Ecology

Arredondo, Tina [1], Cruzan, Mitchell [2].

Impact of suburban landscape features on gene flow of an invasive grass.

The rapid range expansion associated with newly invasive species provides a natural experiment for studying the impact of the landscape on dispersal and gene flow. We use the recently introduced invasive grass, Brachypodium sylvaticum (Poaceae), to study impact of various landscape features on gene flow at the edge of its expanding range. The occurrence of B. sylvaticum along roadsides and waterways has brought into question whether its dispersal is linked to human use of these features. A total of 22 locations in the Clackamas Watershed in the Portland, Oregon metro region were sampled to span a diversity of landscape features potentially influencing gene flow (rivers, roads, canopy cover, development, and agriculture). We used a Genotyping-By-Sequencing (GBS) approach to find single nucleotide polymorphisms (SNPs) among these sites, and assessed populations genetic diversity, structure and potential numbers of source populations. We also created resistance surfaces for each landscape feature, using ResistanceGA to optimize resistance parameters and Circuitscape to generate resistance values between populations. We used Multiple Regression on distance Matrices (MRM) to compare feature resistance to genetic distance, and a backward selection process to drop insignificant features following each MRM run. Our STRUCTURE analysis revealed three distinct clusters, and diversity analyses support the existence of two separate local introductions. We found no evidence that development (p-value=0.075), roads (p-value=0.181), canopy cover (p-value=0.988), agriculture (p-value=0.193) or geographic distance (p-value=0.063) had a significant influence on genetic distance in B. sylvaticum. In contrast, resistance generated from rivers as a conduit explained a large portion of variation in genetic distance (R2=0.333, p-value<0.001). Our results indicate that rivers are influencing gene flow in invasive B. sylvaticum populations; ­as grass seeds tend to be moved by animals and people rather than by hydrochory, we interpret these results to mean humans interacting with the river are the probable dispersal vectors.

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1 - Portland State University, Biology, PO Box 751, Portland, OR, 97207, United States
2 - Portland State University, Department Of Biology, 1719 SW 10th Ave, SRTC Rm 246 - Biology, Portland, OR, 97201, United States

Biological invasion
landscape genetics
Isolation by resistance

Presentation Type: Oral Paper
Session: 22, Molecular Ecology
Location: 107/Mayo Civic Center
Date: Tuesday, July 24th, 2018
Time: 8:45 AM
Number: 22003
Abstract ID:389
Candidate for Awards:None

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