Abstract Detail

Paleobotany

Brightly, William [1], Stromberg, Caroline [2], Christin, Pascal-Antoine [3], Bianconi, Matheus [4].

The role of grasslands in the evolution of seed dispersal strategy in the Poaceae.

Habitats dominated by grasses are globally important, accounting for approximately 40% of all terrestrial ecosystems. The assembly and expansion of these habitats began during the late Oligocene - early Miocene, and was one of the most consequential ecological events of the last 66 million years. Though there is a substantial body of work investigating the consequences of grassland expansion in several groups of animals, grasses themselves have received less attention. Here we explore the effect that this transition had on the evolution of grass seed dispersal strategy, a biologically important process with wide ranging consequences for plants and their communities. Grasses possesses a remarkable diversity of seed dispersal strategies. For grasses, the expansion of grassland habitats likely altered interactions with potential dispersers (e.g., the rise of grazing faunas) and the geographic distribution of suitable habitats, both of which may have influenced the evolution of dispersal strategy. Using a phylogenetic comparative framework, we therefore tested whether or not occupation of grassland habitats was associated with changes in dispersal characters in grasses. We collected diaspores (unit of seed dispersal) of grasses with a focus on broad phylogenetic and ecological sampling. For each diaspore, morphological characters (mass, callus type, shape, surface roughness, falling velocity) were measured and used to estimate dispersal potential for anemochorous (wind), epizoochorous (external animal), and endozoochorous (internal animal) dispersal. We classified habitat type using a GIS based approach, incorporating occurrence data downloaded from GBIF. For each dispersal strategy, we compared several models of character evolution. These varied in whether or not grassland and non-grassland taxa were considered as distinct evolutionary regimes. Preliminary results did not reveal any systematic differences in relation to epizoochory or endozoochory, though grasslands appeared to be associated with increased wind dispersal potential. Evolution of increased wind dispersal potential in grassland habitats may represent the increased viability of this dispersal strategy in these open environments. In addition, transitions away from the family’s ancestral understory habitat may have relaxed selection for larger seed sizes which made anemochory more viable. We are currently working to improve and expand our dataset, particularly through the incorporation of fossil grass diaspores. Fossils were collected from late Oligocene and Miocene sites in Kansas and Nebraska, and represent some of the earliest grassland communities in North America. Their incorporation into our comparative framework will provide unique insight into this question.

1 - 2208 NW 64th St, Seattle, WA, 98107, United States
2 - University Of Washington, Department Of Biology, Life Sciences Building, Box 351800, Seattle, WA, 98195, United States
3 - University of Sheffield, Department of Animal and Plant Sciences, Sheffield, UK
4 - University of Sheffield, Department of Plant and Animal Sciences, Sheffield, UK

Keywords:
seed dispersal
Grasses
grassland.

Presentation Type: Oral Paper
Session: PAL2, Cookson Award Session II
Location: Virtual/Virtual
Date: Monday, July 27th, 2020
Time: 12:45 PM
Number: PAL2001
Abstract ID:652
Candidate for Awards:Isabel Cookson Award,Maynard F. Moseley Award