Document Type

Article

Publication Date

2025

Publication Title

American Journal of Botany

Abstract

Premise: Hydrological regime influences wetland plant species distribution andperformance. Global warming and extreme weather events are magnifying floodingpatterns, and understanding how invasive taxa respond across life stages (establish-ment vs. established phase) is important for predicting and managing their coloni-zation and spread. Our objective was to measure flood trait responses at contrastinglife stages in closely related congeners (Ludwigia peploides, diploid; L. hexapetala,decaploid; Onagraceae) differing in their invasiveness in the field.

Methods: In the field, we assessed phenological responses to seasonal hydrological changes,and in mesocosms, we assessed flood stress responses of establishing shoot fragments underdeep‐flooded, shallow‐flooded, and gradual drawdown hydrological treatments.

Results: Counter to expectations, establishing L. peploides expressed more flood tolerancetraits in mesocosms than L. hexapetala. For example, L. peploides had greater total leaf areaand aerenchyma production than L. hexapetala, supporting its growth under flooding,whereas L. hexapetala expressed more flood escape traits (higher shoot elongation rates,trend for longer shoot internode length). Although L. hexapetala expressed some traitsassociated with drought tolerance, these trends were not significant. In the field, longer‐established plants had a reversed pattern for flood escape versus tolerance traits. Ludwigiapeploides rapidly shifted to sexual reproduction as soils began to dry, whereas L. hexaetalaflowered regardless of soil moisture availability.

Conclusions: These contrasting patterns of flood tolerance versus escape traitsdemonstrate that invasive Ludwigia congeners have differing strategies to counterphysiological stress induced by flooding and emphasize the importance of life stage inresponse to environmental variation

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