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Corbett, Cameron [1], Huebner, Cynthia [2], Barrett, Craig [3].

Reconstructing invasion history and patterns of awn polymorphism across space and time in the noxious weed Microstegium vimineum using plastid genome sequencing.

While studies over the past few decades have focused on the ecological impacts of invasive species, less is known about how invasive species adapt to new environments.  Japanese stiltgrass is an invasive weed in the USA from Asia that outcompetes native species and reduces biodiversity. This species displays polymorphism in presence-absence of the awn, a floret structure that plays a role in active burial syndrome and has been used as a basis for intraspecific taxonomy in earlier treatments. The awnless form was first collected in Tennessee (1919), while the awned form was collected in Pennsylvania (1938), suggesting the possibility of separate invasions. By sequencing uniparentally inherited plastid genomes, we are reconstructing the pattern of invasion history and specifically seed dispersal in the invasive range. We are further using plastid genomic relationships to characterize geographic patterns of important traits, including awn polymorphism, across space and time in the eastern USA and Asia. DNA samples were collected from both contemporary field populations (2019, 2020) and pressed herbarium samples dating back to 1931. Illumina libraries were generated from all accessions collected and sequenced in 96-reaction pools on an Illumina NextSeq2000. Plastid genome assembly was conducted using a batch script that runs a pipeline to generate complete plastomes. Plastomes were aligned and Maximum Likelihood was used to construct trees under partitioned models, with one copy of the Inverted Repeat removed. Plastid haplotype networks and population structure analyses were conducted to trace maternal ancestry of invasive accessions, and to compare the relative diversity of haplotypes in the native and invasive ranges. Preliminary sequencing data provide evidence of either multiple, separate invasions or a genetically diverse initial invasion. Specifically, nuclear sequence capture using in-house probes generated with AFLP showed several invasive accessions grouping with Asian accessions. We also sequenced the plastid trnC-petN spacer region for 80 US accessions across 8 populations and over 100 Japanese accessions available in NCBI GenBank. Of the five haplotypes found in Japan, three were also found in the USA. Additionally, awned and awnless individuals align across a north/south gradient in both invasive and native ranges with an intermediate form in a transition zone. These data support multiple invasions, subsequent spread from points of introduction, and possibly selection maintaining a latitudinal pattern of awn polymorphism. Such a pattern highlights the importance of not presuming invasions start from a singular event, but that repeated invasions with subsequent dispersal and gene flow contribute to invasiveness.

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1 - 49 Falling Run Road, 501, Morgantown, WV, 26505, United States
2 - Northern Research Station, USDA Forest Service, Morgantown, WV, 26505, United States
3 - West Virginia University, Biology, 53 Campus Drive, Morgantown, WV, 26506, USA

invasive plants
Japanesse Stiltgrass
Invasion History.

Presentation Type: Poster
Session: P1, Biogeography Posters
Location: Virtual/Virtual
Date: Monday, July 19th, 2021
Time: 5:00 PM(EDT)
Number: P1BG005
Abstract ID:449
Candidate for Awards:None

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