Making a Bad Situation Worse: An Invasive Species Altering the Balance of Interactions between Local Species

Abstract

Biological invasions pose a significant threat to biodiversity, especially on oceanic islands. One of the primary explanations for the success of plant invaders is direct suppression of competitors. However, indirect interactions can also be important, although they are often overlooked in studies on biological invasion. The shrub Leucaena leucocephala is a widespread island invader with putative allelopathic effects on the germination and growth of other species. We quantified the impact of Leucaena on plant communities richness on an oceanic Brazilian island and, through nursery experiments, investigated the potential for allelopathic effects on the germination of Erythrina velutina, a native species that is often absent from stands of Leucaena. Additionally, in a manipulative field experiment, we examined the direct and indirect effects (mediated by the native species Capparis flexuosa) of the invader on the development of Erythrina. The species richness in invaded sites was lower than in uninvaded sites, and Capparis was the only native species that was frequently present in invaded sites. In the nursery experiments, we found no evidence that Leucaena affects the germination of Erythrina. In the field experiments, the odds of Erythrina germination were lower in the presence of Leucaena litter, but higher in the presence of Leucaena trees. However, the survival and growth of Erythrina were considerably inhibited by the presence of Leucaena trees. The isolated effect of native Capparis on the germination and growth of Erythrina varied from positive to neutral. However, when Capparis and Leucaena were both present, their combined negative effects on Erythrina were worse than the effect of Leucaena alone, which may be attributed to indirect effects. This study provides the first empirical evidence that the balance of the interactions between native species can shift from neutral/positive to negative in the presence of an exotic species.

Short rotation coppice of leguminous tree Leucaena spp. improves soil fertility while producing high biomass yields in Mediterranean environment

“…However, as Leucaena spp. can become an invasive alien species in certain areas, it must be managed with caution (Chiou et al, 2016;Mello and Oliveira, 2016).…”

Allelopathy and Allelochemicals of Leucaenaleucocephala as an Invasive Plant Species

“…There has also been no clear explanation for the suppression of L. leucocephala on native plant species. However, it was observed that the survival and growth of a native woody plant species, Erythrina velutina Willd., was suppressed by the presence of L. leucocephala in the field experiments under relatively controlled conditions [34]. The experiments under controlled conditions may illuminate the possible involvement of light and other environmental factors and suggest the involvement of other factors, such as allelopathy, in the suppression.…”

“…leucocephala threatens native vegetations and biodiversity in the invaded areas [11,27,34]. The species richness in L. leucocephala invaded areas was lower than that in its unin-vaded areas, and the establishment of the native plant species was hardly observed in the L. leucocephala invaded areas [31,34,45,46]. Seedling establishment of native plant species in L. leucocephala plantations was also less [45].…”

“…leucocephala has already naturalized in more than 130 countries in the Pacific Ocean region, Asia, South and Central America, Caribbean, Africa, Middle East, Australia, and Europe, and the number of naturalized countries is still increasing [1,2]. Ecosystems in islands are very vulnerable against invasive plant species like L. leucocephala, and L. leucocephala has caused serious problems in native plant communities in tropical and subtropical oceanic islands [27,[31][32][33][34][35][36]. L. leucocephala is recognized as being a weed of roadsides, hillsides, forest margins, riparian habitats, deserted lands, and abandoned lands (Figure 2).…”

Persistence of Coffea arabica and its relationship with the structure, species diversity and composition of a secondary forest in Brazil

“…A shift in resource availability during succession can cause a shift in community composition and structure from secondary to old-growth forest [ 4 ]. Non-native species can play an important role during succession [ 5 ], as they often have strategies of rapid resource uptake and use and can, in some cases, outperform native species [ 6 , 7 ]. A challenge is to understand the role of non-native species in the community processes because they can potentially become invasive [ 8 – 10 ].…”