The role of biotic resistance is a subject of debate in our understanding of invasions. We used a well‐known system in the Northern Range of Trinidad, where ephemeral conditions in small pool habitats lead to repeated colonisation by two native species (guppies, Using horticultural containers under forest cover, alongside constructed bankside mesocosms, we established populations of each species to test hypotheses concerning the conditions under which the guppy, a globally successful invasive species with the potential to establish populations from a single female, could be excluded by a resident intraguild predator, the killifish. Recruitment success of the guppy depended on founder numbers (propagule size) and introduction order (whether first or last to arrive in the habitat). Single founder guppies always failed to recruit in pools with resident killifish, which we posit is directly attributable to biotic resistance from the resident. However, increased propagule pressure (introduction attempts and propagule number) greatly increased the probability of successful invasion. Our results have two main implications. The first is that guppies are capable of being successful colonisers even in the presence of a resident intraguild predator. The second is to highlight the role that biotic resistance can play in preventing establishment in small‐water habitats, especially under circumstances of low propagule pressure. While previous studies have shown that guppies are strong colonisers outside of their native range, our findings suggest that this may not always be the case when there are other small‐bodied fish present. Accordingly, we argue that in small‐water habitats, biotic resistance and intraguild predation relationships should be important considerations when the ability to establish is being assessed for a taxon.
The encroachment of invasive shrubs in forest understories can have detrimental effects on native plant recruitment. As a result, removal of invasive species is a common practice although long‐lasting success is rare. In order to effectively conserve and manage invaded forests, it is crucial to understand the mechanisms that drive shrub invasion, that is, high propagule pressure, low native resistance and exploitation of empty niches. To gain a deeper understanding of the invasion process in forest ecosystems we conducted a meta‐analysis of the work done in this topic. We collected data on invasive species and native community performance, and on the abiotic conditions of forest understories under low and high levels of shrub invasion. We analysed data from 124 articles that yielded 377 unique observations. Our results revealed that while invader performance did not vary by the mechanism of invasion, the impact on the native community was significantly detrimental when invasion occurred via low biotic resistance, and only marginally significant via propagule pressure. Invasive species performance was associated with increases in light availability, but not with other resources (soil water or nutrients). When assessing impact on native performance as a function of invasive performance, results were again only significant under the low biotic resistance mechanism. Lastly, impacts were stronger when invasion took place by a single invader.
- NSF-PAR ID:
- 10443866
- Publisher / Repository:
- Wiley-Blackwell
- Date Published:
- Journal Name:
- Journal of Applied Ecology
- Volume:
- 60
- Issue:
- 11
- ISSN:
- 0021-8901
- Format(s):
- Medium: X Size: p. 2314-2326
- Size(s):
- ["p. 2314-2326"]
- Sponsoring Org:
- National Science Foundation
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