Tolerance of subzero winter cold in kudzu (Pueraria montana var. lobata)

Abstract

The use of species distribution as a climate proxy for ecological forecasting is thought to be acceptable for invasive species. Kudzu (Pueraria montana var. lobata) is an important invasive whose northern distribution appears to be limited by winter survival; however, kudzu’s cold tolerance thresholds are uncertain. Here, we used biogeographic evidence to hypothesize that exposure to − 20 °C is lethal for kudzu and thus determines its northern distribution limit. We evaluated this hypothesis using survival tests and electrolyte leakage to determine relative conductivity, a measure of cell damage, on 14 populations from eastern North America. Relative conductivity above 36% was lethal. Temperatures causing this damage averaged − 19.6 °C for northern and − 14.4 °C for southern populations, indicating kudzu acclimates to winter cold. To assess this, we measured relative conductivity of above- and belowground stems, and roots collected throughout the winter at a kudzu population in southern Ontario, Canada. Consistent with acclimation, the cold tolerance threshold of aboveground stems at the coldest time of year was − 26 °C, while stems insulated from cold extremes survived to − 17 °C—colder than the survival limits indicated by kudzu’s biogeographic distribution. While these results do not rule out alternative cold limitations, they indicate kudzu can survive winters north of its current distribution. For kudzu, biogeography is not a proxy for climatic tolerance and continued northward migration is possible. Efforts to limit its spread are therefore prudent. These results demonstrate that physiological constraints inform predictions of climate-related changes in species distribution and should be considered where possible.

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Oecologia (2018) 187:839–849
https://doi.org/10.1007/s00442-018-4157-8
GLOBAL CHANGE ECOLOGY – ORIGINAL RESEARCH
Tolerance ofsubzero winter cold inkudzu (Pueraria montana var.
lobata)
HeatherA.Coiner1· KatharineHayhoe2,3· LewisH.Ziska4· JeVanDorn5· RowanF.Sage1
Received: 20 October 2017 / Accepted: 2 May 2018 / Published online: 16 May 2018
© Springer-Verlag GmbH Germany, part of Springer Nature 2018
Abstract
The use of species distribution as a climate proxy for ecological forecasting is thought to be acceptable for invasive species.
Kudzu (Pueraria montana var. lobata) is an important invasive whose northern distribution appears to be limited by winter
survival; however, kudzu’s cold tolerance thresholds are uncertain. Here, we used biogeographic evidence to hypothesize
that exposure to −20°C is lethal for kudzu and thus determines its northern distribution limit. We evaluated this hypothesis
using survival tests and electrolyte leakage to determine relative conductivity, a measure of cell damage, on 14 populations
from eastern North America. Relative conductivity above 36% was lethal. Temperatures causing this damage averaged
−19.6°C for northern and −14.4°C for southern populations, indicating kudzu acclimates to winter cold. To assess this,
we measured relative conductivity of above- and belowground stems, and roots collected throughout the winter at a kudzu
population in southern Ontario, Canada. Consistent with acclimation, the cold tolerance threshold of aboveground stems
at the coldest time of year was −26°C, while stems insulated from cold extremes survived to −17°C—colder than the
survival limits indicated by kudzu’s biogeographic distribution. While these results do not rule out alternative cold limita-
tions, they indicate kudzu can survive wintersnorth of its current distribution. For kudzu, biogeography is not a proxy for
climatic tolerance and continued northward migration is possible. Efforts to limit its spread are therefore prudent. These
results demonstrate that physiological constraints inform predictions of climate-related changes in species distribution and
should be considered where possible.
Keywords Freezing tolerance· Global warming· Invasive species· Species distributions· Thermal acclimation· Climate
equilibrium· Niche shift
Introduction
Forecasting plant invasions is an ecological priority in a
changing climate (Fischlin etal. 2007). Models predicting
changes in species distributions often rely on the assumption
that the climate in the native range is an adequate proxy for
physiological and ecological tolerances, thereby allowing
climate correlates to predict future range limits. Recent work
Communicated by Evan H DeLucia.
Electronic supplementary material The online version of this
article (https ://doi.org/10.1007/s0044 2-018-4157-8) contains
supplementary material, which is available to authorized users.
* Rowan F. Sage
r.sage@utoronto.ca
1 Department ofEcology andEvolutionary Biology,
University ofToronto, 25 Willcocks Street, Toronto,
ONM5S3B2, Canada
2 Climate Science Center, Texas Tech University, Lubbock,
TX79409, USA
3 ATMOS Research andConsulting, Lubbock, TX79490,
USA
4 United States Department ofAgriculture, Agricultural
Research Service, Adaptive Cropping Systems Laboratory,
10300 Baltimore Avenue, Beltsville, MD20705, USA
5 Department ofPediatrics, Center forBetter Beginnings,
University ofCalifornia, La Jolla, SanDiego,
CA92093-0828, USA
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