Flooding compromises compensatory capacity of an invasive plant: implications for biological control

Abstract

Plant compensatory growth is proposed to be insidious to biological control and known to vary under different environmental conditions. However, the effects of microsite conditions on compensation capacity and its indirect impacts on biological control of plant invaders have received little attention. Alligator weed, Alternanthera phioxeroides, is an invasive plant worldwide, growing in both aquatic and terrestrial habitats that are often affected by flooding. Biological control insects have been successful in suppressing the plant in many aquatic habitats but have failed in terrestrial habitats. To evaluate the impact of flooding on compensation capacity, we conducted common garden and greenhouse experiments in which plants were grown under different moisture conditions (aquatic versus terrestrial). Our results show that plants were able to fully recover from continued herbivory in the terrestrial habitat, but failed in the aquatic habitat, indicating a flooding-regulated plant compensatory capacity. Also, the grazed plants increased below-ground growth and reproductive root bud formation in the terrestrial habitat, but there was no such difference in the aquatic habitat. Our findings suggest that the differing plant compensatory capacity, affected by flooding, may explain the different biological control efficacy of alligator weed in aquatic and terrestrial habitats. Understanding mechanisms in plant invader compensation in different microsite conditions is important for improving management efficiency.

Climate warming affects biological invasions by shifting interactions of plants and herbivores

“…This survey found that the plant range was from 20°N to 34.7°N and its population size was greatest in regions between 30°N and 32.5°N. Previous studies in China found that the beetle has only successfully suppressed A. philoxeroides in aquatic habitats but has limited impact in terrestrial habitats , partly due to lower pupal survival (Ma & Wang, ) and high plant tolerance of herbivory (Lu & Ding, ). Consequently, the terrestrial form of A. philoxeroides is still very invasive in China.…”

Direct and indirect impacts of different water regimes on the invasive plant, alligator weed (Alternanthera philoxeroides), and its biological control agent, Agasicles hygrophila

“…The root morphology and distribution determine a plant's resource acquisition, especially in environments that are characterized by low water and nutrient availability (Lynch ). The root‐to‐shoot mass ratio of A. philoxeroides is lower and the roots are composed mainly of thin roots in aquatic habitats, while the root‐to‐shoot mass ratio is much higher and the roots are composed mainly of thick storage roots in terrestrial habitats (Lu & Ding ). Therefore, the level of root resource acquisition of A. philoxeroides might be lower in aquatic than terrestrial habitats, implying that the plant will perform poorly when flooded.…”

“…). In terrestrial habitats, although it can establish populations and cause damage to the weed, it has had little or no impact on the weed population due to low pupal survival (Ma & Wang ) and the high tolerance of A. philoxeroides to herbivory (Lu & Ding ). As a result, terrestrial A. philoxeroides is still invasive in China.…”

Predicting Compensatory Growth and Reproduction in Agricultural Weeds Using a Plant’s Growth Rate Trajectory: A Test with Defoliation of Abutilon theophrasti

“…[2]. Given that compensatory growth in weeds can negate the effects of biological control agents [9], this study illustrates a mechanism and growth variables that need to be measured to predict compensatory responses in weed species as a function of environmental resource levels.…”