Seedlings of the Invasive Strawberry Guava Psidium cattleianum Were More Sensitive to Defoliation Than the Closely Related Malagasy Native Eugenia goviala in a Simulated Herbivory Experiment

Abstract

The success of non-native plants in their recipient environments is often attributed to their relatively lower herbivorous attack (i.e., leaf damage). However, whether non-native plants are inherently more tolerant to leaf damage than native ones remains unclear. We conducted a field experiment to test the effects of clipping (25%, 50%, and 75% leaf area loss) on growth (stem height and production of new leaves) of the natural regenerations of invasive strawberry guava Psidium cattleianum (Myrtaceae) and its closely related native, Eugenia goviala (VU, Myrtaceae,), in a degraded forest in Andasibe, Madagascar. Each clipped individual was paired with a neighboring control (0% defoliation). Survival rates after 105 days were high (>93%) for both species and were not related to clipping levels. Eugenia goviala increased stem growth by 98% at 25% clipping but exhibited no response at higher clipping levels. Clipping tended to reduce stem growth in P. cattleianum but effects were only significant at 75% defoliation (46% reduction in stem growth). Defoliation did not affect the production of new leaves but we detected a tendency for P. cattleianum to produce fewer leaves at higher clipping levels. These results indicate a higher sensitivity to defoliation in the invasive strawberry guava compared to its close native relative E. goviala, which does not support the hypothesis that non-native plant species are more tolerant to leaf damage than native ones. Heavy defoliation can represent a substitute for mechanical control of the strawberry guava. Future studies should focus on identifying suitable native herbivores as part of an integrated control program for this invasive species.

Defoliation in Perennial Plants: Predictable and Surprising Results in Senna spp.

“…Some studies have found greater sensitivity to defoliation in non-native vs. native species [ 51 ], though we did not see this difference in the congeneric species in this study. While sulphur butterflies oviposit on all the Senna spp.…”

The eco‐evolutionary history of Madagascar presents unique challenges to tropical forest restoration

“…Whereas tavy reduces soil nutrient availability, a separate question is whether native Malagasy species grow slowly due to conservative growth strategies adapted to Madagascar’s ancient and inherently nutrient‐poor soils (de Gouvenain et al, 2007; Ghimire et al, 2018; Manjaribe et al, 2013; Rakotonoely & Ramamonjisoa, 2020; Vincelette et al, 2007; also see Section 2.2 ). It is difficult to test this hypothesis using existing literature, because comparisons of growth rates cannot be disentangled from land use (i.e., tavy, as per above), though the relatively short height and small diameter of trees in undisturbed Malagasy rain forests suggest the possibility of evolved conservative growth strategies (Grubb, 2003).…”

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