Linking niche theory to ecological impacts of successful invaders: insights from resource fluctuation‐specialist herbivore interactions

Abstract

Summary1. Theories of species coexistence and invasion ecology are fundamentally connected and provide a common theoretical framework for studying the mechanisms underlying successful invasions and their ecological impacts. Temporal fluctuations in resource availability and differences in life-history traits between invasive and resident species are considered as likely drivers of the dynamics of invaded communities. Current critical issues in invasion ecology thus relate to the extent to which such mechanisms influence coexistence between invasive and resident species and to the ability of resident species to persist in an invasive-dominated ecosystem. 2. We tested how a fluctuating resource, and species trait differences may explain and help predict long-term impacts of biological invasions in forest specialist insect communities. We used a simple invasion system comprising closely related invasive and resident seed-specialized wasps (Hymenoptera: Torymidae) competing for a well-known fluctuating resource and displaying divergent diapause, reproductive and phenological traits. 3. Based on extensive long-term field observations (1977-2010), we developed a combination of mechanistic and statistical models aiming to (i) obtain a realistic description of the population dynamics of these interacting species over time, and (ii) clarify the respective contributions of fluctuation-dependent and fluctuation-independent mechanisms to long-term impact of invasion on the population dynamics of the resident wasp species. 4. We showed that a fluctuation-dependent mechanism was unable to promote coexistence of the resident and invasive species. Earlier phenology of the invasive species was the main driver of invasion success, enabling the invader to exploit an empty niche. Phenology also had the greatest power to explain the long-term negative impact of the invasive on the resident species, through resource pre-emption. 5. This study provides strong support for the critical role of species differences in interspecific competition outcomes within animal communities. Our mechanistic-statistical approach disentangles the critical drivers of novel species assemblages resulting from intentional and nonintentional introductions of non-native species.

Isotopic niche overlap between the invasive leiothrix and potential native competitors

“…However, although an overlap in diet is a potential source of competition, it does not always mean that competition occurs (Cody, 1974;Dhondt, 2012), but it may in fact be attenuated by different factors. First, the different species could exploit the shared resources at different times of year, decreasing or avoiding competence (León et al, 2014;Gidoin et al, 2015). Nevertheless, since the three species moult during the same period over a short time window, approximately from July to August (Jenni and Winkler, 1994;pers.…”

Biological Invasion Theories: Merging Perspectives from Population, Community and Ecosystem Scales

“…A plant example is the invasion of the non-native tree Casuarina equisetifolia on recent volcanic flows on La Reunion Island (Potgieter et al 2014). Other examples are the ability of the invasive fruit fly Drosophila suzukii to use unripe and ripening fruits before the other drosophila feeding on ripe and rotting fruits (Poyet et al, 2014), or invasive seed wasps who have priority access to limited resources due to earlier phenology than their competitors (Gidoin, Roques & Boivin, 2015). Such cases point to invasive populations accessing unused or under-utilized resources or to gain competitive advantage to exploit shared and limited resources, leading to significant community-level impacts.…”

When higher carrying capacities lead to faster propagation

“…Studies on introduced species often show that invasion success is correlated with life-history traits (Moravcova et al, 2010;van Kleunen et al, 2011;Gidoin et al, 2015) yet, the properties of the environment also affect expansion patterns. Previous studies have analyzed the impact of habitat quality on expansion.…”