Plant invasion alters latitudinal patterns of plant-defense syndromes

Authors: LIU, M - Fudan University; PAN, Y - Fudan University; PAN, X - Fudan University; SOSA, D - Consejo Nacional De Investigaciones Científicas Y Técnicas(CONICET); Blumenthal, Dana; VAN KLEUNEN, M - University Of Konstanz; LI, B - Fudan University

Submitted to: Ecology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/17/2021
Publication Date: 8/5/2021
Citation: Liu, M., Pan, Y., Pan, X., Sosa, D., Blumenthal, D.M., Van Kleunen, M., Li, B. 2021. Plant invasion alters latitudinal patterns of plant-defense syndromes. Ecology. 102(12). Article e03516. https://doi.org/10.1002/ecy.3511.
DOI: https://doi.org/10.1002/ecy.3511

Interpretive Summary: Both herbivory declines and plant defense have been predicted to decline with latitude. We investigated latitudinal variation in leaf herbivory, mycorrhizal associations, and plant defense in invasive wetland plant both in its native Argentinean range and its introduced Chinese range. Leaf herbivory decreased with latitude, particularly in the introduced range. In addition, latitudinal variations in plant defenses were associated with biotic factors, including interactions with mycorrhical fungi, in the native range and with abiotic factors in the introduced range. These results show how and why herbivore interactions with a problematic wetland invader plant vary regionally.

Technical Abstract: It has been predicted that herbivory declines with latitude and hence defensive traits also show latitudinal patterns. However, it is unknown as to whether this also holds for invasive plants in the introduced ranges. We conducted two extensive field surveys of Alternanthera philoxeroides (alligator weed), a worldwide alien invasive plant, along broad latitudinal gradients (covering 12° of latitude) in Argentina (native range) and China (introduced range). We assessed latitudinal patterns of plant defense (leaf nitrogen concentration, triterpenoid saponins, flavonoids, tannins and lignin, and leaf trichome density), herbivory (percentage leaf area removed) and AMF association (a-diversity and percentage root colonization of AMF). We found that leaf herbivory decreased with latitude, but the slope was steeper for introduced than native populations and that leaf herbivory in the introduced range was significantly lower than that in the native range, but only at high latitudes. We also found that native and introduced populations have contrasting latitudinal patterns in many putative defense traits (concentrations of triterpenoid saponins, flavonoids and lignin, and trichome density). Our results demonstrate that the correlations of defenses with herbivory, AMF association and climate factors in the introduced range contrast those in the native range. Specifically, there were no significant correlations of any defensive traits studied with leaf herbivory in the introduced range. Overall, our study confirms that plant invasion alters latitudinal patterns of defense and herbivory, and advances our understanding of the biogeographic consequences of plant invasion.