COS 139-4 - Common milkweed, Asclepias syriaca, exhibits latitudinal clines in germination and early growth traits.

Wednesday, August 17, 2022

8:45 AM – 9:00 AM EDT

Location: 518B

Presenting Author(s)

EM

Emily Mohl, Ph.D

Associate professor
St Olaf College
Northfield, MN, United States

Coauthor(s)

MR

Mari Reid

St. Olaf College, United States
MW

Madelyn Wood

St. Olaf College, United States
LS

Lauren Sherman

St. Olaf College, United States
AM

Andrew McCall

Denison University, United States
JS

Jennifer Styrsky

University of Lynchburg, United States
JS

John Styrsky

University of Lynchburg, United States
DG

Danielle Garneau

SUNY Plattsburgh, New York, United States
KC

Kendra Cipollini

Wilmington College, United States
KS

Kaitlin Stack Whitney

Rochester Institute of Technology, United States
SS

Sara Scanga

Utica University, New York, United States
HM

Heather Marella

Bridgewater State University, United States
MF

M. Caitlin Fisher-Reid

Bridgewater State University, United States
KH

Kristine Hopfensperger

Northern Kentucky University, Kentucky, United States
PS

Patricia A. Saunders

Ashland University
Ashland, OH, United States

Background/Question/Methods

Restoration of milkweed plants, including Asclepias syriaca, has increased in response to population declines of a key herbivore, the monarch butterfly, Danaus plexippus. Evidence for local adaptation in A. syriaca would indicate that local seed sourcing would improve restoration success. Using seeds from 20 populations throughout the range of common milkweed, we tested for geographic clines in germination and early growth traits in a common garden. Additionally, we tested for local adaptation in germination traits to spring thermal conditions by planting seeds from 10 populations in growth chambers simulating Minnesota and Kentucky spring temperatures.

Results/Conclusions

Even after accounting for seed mass, germination time declined with source population latitude in all growing conditions, a pattern inconsistent with local adaptation to spring temperature. We did not detect geographic patterns in leaf development time, indicating that the processes underlying the latitudinal cline in germination time may be unique to this developmental stage. Preliminary analyses of field data indicate that source population latitude is positively associated with early season growth but negatively associated with end of season height. We conclude that latitudinal clines suggest plant phenology is adapted to local growing conditions, but recommendations to use locally sourced seed would be better supported by direct evidence for local adaptation.