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Barrett, Craig [1], Huebner, Cynthia [2], Cumberledge, Aubrey [1], Latvis, Maribeth [3], McKain, Michael [4], Motley, M'Kayla [5], Santee, Mathilda Viola [1], Skibicki, Sam [1], Thixton, Hana [1].

Digitized collections elucidate invasion history and patterns of awn polymorphism in the invasive Japanese stiltgrass (Microstegium vimineum).

Centralized, searchable databases of digitized historical biodiversity collections facilitate a variety of studies including those of macroecology, macroevolution, responses to climate change, and invasive species biology. Here, over 1,000 digitized Asian and US herbarium images were examined to investigate invasion history and trait variation in a problematic weed, Microstegium vimineum. Specifically, the presence and absence of awns was investigated to test hypotheses on geographic patterns of this polymorphic trait, which serves myriad functions in grasses including diaspore burial and dispersal to safe sites. Similar patterns of awn presence-absence polymorphism were observed in Asia and the US, with the awned form predominating at higher latitudes, and the awnless form at lower latitudes. Reconstruction of the invasion history of M. vimineum in the US revealed an initial invasion of the awnless form in the Southeast, with the first recorded specimen from Tennessee in 1919 and subsequent spread in the southeastern US. A putative secondary invasion of the awned form appeared in herbarium records in eastern Pennsylvania in the late 1930s, with subsequent spread through the Northeast. Logistic regression of abiotic climate variables (BIOCLIM) and awn presence-absence accurately predicted the occurrence of awned or awnless forms for 93 percent of US records. A closer, quantitative investigation of awn and floret measurements from a subset of records along a latitudinal gradient revealed that awned forms have longer florets, and that floret size varies significantly with latitude, while those records with longer awns also show higher degrees of awn bending. Further, there is evidence of a ‘transition zone’ with specimens having relatively short awns at mid-latitudes between predominantly ‘long-awned’ forms to the north and awnless forms to the south. Taken together, we hypothesize that multiple invasions have occurred in the US, and that a combination of invasion history and selection for awned forms at higher latitudes determine the geographic pattern of polymorphism in this trait, which recapitulates the same geographic pattern found in the native range. Our results support the hypothesis of awns increasing seed survival at higher latitudes where soil freezing is more frequent and intense. However, there does not appear to be a disadvantage of not being able to find safe sites associated based on the predominance of awnless florets in southern latitudes. This study demonstrates the power and utility of large, centralized, digitized databases of historical specimens in invasive species biology.

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1 - West Virginia University, Biology, 53 Campus Drive, Morgantown, WV, 26506, USA
2 - Northern Research Station, USDA Forest Service, Morgantown, WV, 26505, United States
3 - South Dakota State University, Department Of Natural Resource Management, 1390 College Avenue, Box 2140B, South Dakota State University , Brookings , SD, 57006, United States
4 - University of Alabama, Biological Sciences, 300 Hackberry Lane, Tuscaloosa, AL, 35487, USA
5 - University Of Alabama, Box 870118, Box 870118, Tuscaloosa, AL, 35487, United States

burial syndrome
transition zone
rapid evolution.

Presentation Type: Oral Paper
Session: BIOGI, Biogeography I
Location: Virtual/Virtual
Date: Monday, July 19th, 2021
Time: 12:45 PM(EDT)
Number: BIOGI002
Abstract ID:239
Candidate for Awards:None

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