Invasive alien plants can increase the abundance of generalist herbivorous insects
Acacia dealbata (Fabaceae: EPPO List of Invasive Alien Plants) and Carpobrotus edulis (Aizoaceae: EPPO List of Invasive Alien Plants) can cause negative impacts on native species and ecosystem services within the EPPO region. A. dealbata is native to Australia and has been present within the EPPO region since the early 1800s. It forms dense monospecific stands, reducing light, native plant cover and diversity in the understory. C. edulis is native to South Africa and has been present in the EPPO region since the early twentieth century. It invades coastal areas and cliffs and changes the dynamics of dunes and displaces local flora. The present study set out to assess the accumulation of herbivorous insects at different invasion levels of the non-native plant species and to evaluate whether introduced plants favour native or exotic herbivorous insects, as well as generalist or specialist herbivorous insects. To do this, A. dealbata was surveyed in nine areas (500 m apart) in the Iberian Peninsula including Galicia (Spain) and Região Norte (Portugal). In the same region, C. edulis, was surveyed in nine coastal areas with no known history of disturbance in the last 10 years. Sampling was conducted in 2015 and at each site, both invasive plant species were categorised into a low, medium or high occurrence based on its percentage cover, and herbivorous insect species were collected and identified. In total, 3 317 insects were identified during the study and the majority were spittlebug nymphs: Philaenus spumarius (Hemiptera: Aphrophoridae) found feeding on the non-native plants and other species. In addition, Cercopis intermedia (Hemiptera: Cercopidae) was found on A. dealbata in higher abundance compared to on other plant species. Two non-native species, Icerya purchasi (Hemiptera: Margarodidae) and Nezara viridula (Heteroptera: Pentatomidae) were found feeding on A. dealbata. The results highlight that alien plant invasions can alter herbivore community structure. This study shows that both C. edulis and A. dealbata act as hosts of native and exotic herbivores.
Sources
Rodríguez, Thompson V, Rubido-Bará, Cordero-Rivera A, González L (2019) Herbivore accumulation on invasive alien plants increases the distribution range of generalist herbivorous insects and supports proliferation of non-native insect pests. Biological Invasions 21, 1511-1527.