How dry is dead? Evaluating the impact of desiccation on the viability of the invasive species Cissus quadrangularis

Abstract

Cissus quadrangularis is a succulent vine that degrades forests where it is not native by growing over trees and causing them to break or by impeding regeneration. Methods for its control have been tried but no satisfactory approach has been found yet. We carried out an experiment to analyze how much desiccation Cissus can endure before losing its ability to grow when rehydrated, using fragments of 0.5, 1, 2, and 3 internodes to test if desiccation tolerance was affected by fragment length. We found that Cissus remains viable after losing up to 80% of its weight, with shorter fragments losing viability (capacity to grow) at 70% weight loss. No fragments sustained viability at 90% water loss, establishing a critical threshold for Cissus desiccation tolerance. Our study also showed that shorter fragments (0.5 internodes) were less viable compared to longer ones (1, 2 or 3 internodes). Cissus has a remarkable tolerance to desiccation. Therefore, management strategies should ensure complete dehydration of Cissus fragments to prevent its regrowth. Reducing fragments to smaller sizes could amplify the effectiveness of control measures by reducing their viability, but risks of increasing propagule numbers should be considered.

Keywords: Madagascar; desiccation tolerance; ecological restoration; invasive species; management; tropical dry forest.

FIGURE 1

Proportion of Cissus quadrangularis fragments that exhibited viability (scored as regrowth of roots or shoots) for the three internode categories across all the mass loss categories (of all the 750 fragments used in the experiment). Error bars represent the standard error of the proportions. The bar plot shows the direct observations from the dataset, while the model‐based probabilities presented in the results section, derived from logistic regression, serve to estimate the likelihood of regrowth for these categories.

FIGURE 2

Proportion of viable (Yes) and non‐viable (No) Cissus quadrangularis fragments categorized by the percentage of weight loss. Numbers above the bars represent the weight loss category. Each bar represents the proportion of viable and non‐viable fragments within each length category: 0.5, 1, 2, or 3 internode‐long fragments.