Tolerance of subzero winter cold in kudzu (Pueraria montana var. lobata) and its implications for northward migration in a warming climate

Authors: COINER, HEATHER - University Of Toronto; HAYHOE, KATHARINE - Texas Tech University; Ziska, Lewis; VAN DORN, JEFF - Texas Tech University; SAGE, ROWAN - University Of Toronto

Submitted to: Oecologia
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/20/2018
Publication Date: 5/16/2018
Citation: Coiner, H.A., Hayhoe, K., Ziska, L.H., Van Dorn, J., Sage, R.F. 2018. Tolerance of subzero winter cold in kudzu (Pueraria montana var. lobata) and its implications for northward migration in a warming climate. Oecologia. https://doi.org/10.1007/s00442-018-4157-8.
DOI: https://doi.org/10.1007/s00442-018-4157-8

Interpretive Summary: Kudzu (Pueraria montana var. lobata) is an important invasive species that was planted throughout southeastern North America until the mid-20th century. Its presence results in significant environmental and economic damage. Consequently, how changing climate alter its spread is of concern. Winter survival is commonly assumed to control its distribution; however, its cold tolerance thresholds have not been determined. Here, we used biogeographic data from kudzu’s distribution in North America to assess whether a minimal temperature of –20°C exposure determines its northern distribution limit. Consistent with acclimation, cold tolerance threshold varied with the season. At the coldest time of year, aboveground stems avoided lethal injury above -26°C, while belowground stems survived to –17°C — colder than the survival limits indicated by kudzu’s biogeographic distribution. In the field, soil insulated belowground tissues from extreme cold, so stems and roots avoided lethal exposure. While these results do not rule out alternative cold limitations, they indicate that kudzu can survive north of its current range limit if dispersed by humans. Northward range expansion of kudzu is currently a possibility and efforts to limit such spread would be prudent.

Technical Abstract: Kudzu (Pueraria montana var. lobata) is an important invasive species that was planted throughout southeastern North America until the mid-20th century. Winter survival is commonly assumed to control its distribution; however, its cold tolerance thresholds have not been determined. Here, we used biogeographic evidence from kudzu’s distribution in North America to hypothesize –20°C exposure 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 fourteen populations from eastern North America. Relative conductivity above 36% was lethal. Threshold temperatures causing this damage averaged -19.6°C for northern and -14.4°C for southern populations, indicating kudzu acclimates to varying extremes of winter cold. To further 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, cold tolerance threshold varied with the season. At the coldest time of year, aboveground stems avoided lethal injury above -26°C, while belowground stems survived to –17°C — colder than the survival limits indicated by kudzu’s biogeographic distribution. In the field, soil insulated belowground tissues from extreme cold, so stems and roots avoided lethal exposure. While these results do not rule out alternative cold limitations, they indicate kudzu can survive north of its current range limit if dispersed by humans. Northward range expansion of kudzu is currently a possibility and efforts to limit such spread would be prudent.