DOI: 10.5061/dryad.x0k6djhr4
title: A novel hybrid beachgrass is invading U.S. Pacific Northwest dunes with potential ecosystem consequences

description: Invasive plants formed via hybridization, especially those that modify the
 structure and function of their ecosystems, are of particular concern
 given the potential for hybrid vigor. In the U.S. Pacific Northwest, two
 invasive, dune-building beachgrasses, Ammophila arenaria (European
 beachgrass) and A. breviligulata (American beachgrass) have hybridized and
 formed a new beachgrass taxa (Ammophila arenaria × A. breviligulata) but
 little is known about its distribution, spread, and ecological
 consequences. Here we report on surveys of the hybrid beachgrass conducted
 across a 250-km range from Moclips, Washington to Pacific City, Oregon in
 2021 and 2022. We detected nearly 300 hybrid individuals, or an average of
 8–14 hybrid individuals per km of surveyed foredune. The hybrid was more
 common at sites within southern Washington and northern Oregon where A.
 breviligulata is abundant (75–90% cover) and A. arenaria is sparse and
 patchy. The hybrid displayed morphological traits such as shoot density
 and height that typically exceeded its parent species suggesting hybrid
 vigor. We measured an average growth rate of 30% over one year, with
 individuals growing faster at the leading edge of the foredune, nearest
 the beach. We also found a positive relationship between hybrid abundance
 and that of A. arenaria, suggesting that A. arenaria density may be a
 controlling factor for hybridization rate. The hybrid showed similar sand
 deposition and associated plant species richness patterns compared to its
 parent species, although longer-term studies are needed. Finally, we found
 hybrid individuals within and near conservation habitat of two Endangered
 Species Act-listed, threatened bird species, the western snowy plover
 (Charadrius alexandrinus nivosus) and the streaked horned lark (Eremophila
 alpestris strigata), a concern for conservation management. Documenting
 this emerging hybrid beachgrass provides insights into how hybridization
 affects the spread of novel species and the consequences for communities
 in which they invade.
description: # **A novel hybrid beachgrass is invading U.S. Pacific Northwest dunes
 with potential ecosystem consequences**
 [https://doi.org/10.5061/dryad.x0k6djhr4](https://doi.org/10.5061/dryad.x0k6djhr4) This folder contains datasets related to hybrid beachgrass distribution, spread, and ecological consequences. All .xlsx files have a Raw_Data tab that contains the dataset and a second Variable_Names tab that contains notes about the file and further explains each variable name. Any code will be provided upon request. ## Description of the data and file structure Included datasets are described below, organized into sections. ***Beachgrass Searches*** 1. **HYBR_AMAR_Searches_Divided.xlsx**: * The search transect dataset, as described below, split into roughly &lt;= 0.2 km segments using ArcGIS Pro for the purposes of analysis. 2. **HYBR_AMAR_Searches_Undivided.xlsx**: * Dataset of 53 search transects conducted in 2019 (by R. Mostow), 2021, and 2022 (by R. Askerooth, R. Mostow, S. Hacker, and field assistants). Search transects vary in length and each contain information about the number of *Ammphoila arenaria* and *Ammophila* hybrid individuals or “patches” found along the transect. 3. **HYBR_Patch_Locations.xlsx**: * Dataset of the distribution, location, and other identifying information of the hybrid patches found as of May 2023. ***Vegetation and Beachgrass Measurements*** 1. **Beachgrass_Morphometrics.xlsx**: * Measurements of beachgrass morphology and growth form, from samples collected in a field setting and measured in the lab. Species measured include *Leymus mollis* and all *Ammophila* taxa. 2. **All_Quadrat_Data_v2.xlsx**: * All data collected from haphazard quadrat (0.5 m by 0.5 m) sampling in 2021 and 2022, including dune grass density, tiller height, and quadrat species richness and percent cover. 3. **All_Perimeters_v2.xlsx**: * Areas of all hybrid patches collected in 2021 and 2022, in a long format, including patches that were not resampled for growth. 4. **Hybrid_Perimeters_Growth.xlsx** * Areas of hybrid patches collected in 2021 and 2022 in a wide format, showing change over time for only patches that were sampled in 2021 and again in 2022. 5. **Point_Intercept_221216.xlsx**: * Point-intercept surveys, perpendicular to the shoreline, that document the presence or absence of vegetation. Number headings denote the position along a line, while a value of 1 indicates the presence of a taxon, and value of 0 indicates absence. ***GPS Transects*** 1. Transect_Metrics.xlsx * Contains the three calculated metrics (Elevation, Volume, and Rugosity) derived from the Raw_transect_data folder. Processing of the transect data was performed in Matlab, while statistical analysis with the Transect_Metrics dataset was performed in R. Raw data of transects will be provided upon request.