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Invading a mutualistic network: to be or not to be similar

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ABSTRACT

Biological invasion remains a major threat to biodiversity in general and a disruptor to mutualistic interactions in particular. While a number of empirical studies have directly explored the role of invasion in mutualistic pollination networks, a clear picture is yet to emerge and a theoretical model for comprehension still lacking. Here, using an eco‐evolutionary model of bipartite mutualistic networks with trait‐mediated interactions, we explore invader trait, propagule pressure, and network features of recipient community that contribute importantly to the success and impact of an invasion. High level of invasiveness is observed when invader trait differs from those of the community average, and level of interaction generalization equals to that of the community average. Moreover, multiple introductions of invaders with declining propagules enhance invasiveness. Surprisingly, the most successful invader is not always the one having the biggest impact on the recipient community. The network structure of recipient community, such as nestedness and modularity, is not a primary indicator of its invasibility; rather, the invasibility is best correlated with measurements of network stability such as robustness, resilience, and disruptiveness (a measure of evolutionary instability). Our model encompasses more general scenarios than previously studied in predicting invasion success and impact in mutualistic networks, and our results highlight the need for coupling eco‐evolutionary processes to resolve the invasion dilemma.

No MeSH data available.


(A) Invasiveness and (B) impact of the invader as a function of its relative trait value and generalization level ratio, relative to those of the native community. Invasiveness and impact values represent the average over 100 medium‐size networks. Lines represent the zero level of invasiveness under different introduction modes.
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ece32263-fig-0002: (A) Invasiveness and (B) impact of the invader as a function of its relative trait value and generalization level ratio, relative to those of the native community. Invasiveness and impact values represent the average over 100 medium‐size networks. Lines represent the zero level of invasiveness under different introduction modes.

Mentions: Both the generalization level of the invader and its trait had an effect on the invasion success (Fig. 2). In general, species having the level of generalization similar to that of the natives are more likely to be invasive (vertically centered area of Fig. 2A). Species having extreme trait values but a high level of generalization also have high invasiveness (top‐right and bottom‐right corners of Fig. 2A). Species that are extreme specialist with extreme trait values also tend to be more invasive than those with trait value similar to most of the native species (extreme left area of Fig. 2A). Although the trait of the invader and its level of generalization can affect the population density of the native community, the overall impact of the invasion is small, reducing the total population size of the entire native community by about 1% (Fig. 2B). Highly generalist species having trait values similar to those of native species have the highest impact on the native community (center‐right area of Fig. 2B). The impact is also high for extreme specialist species having trait values similar to natives (center‐left area of Fig. 2B). The introduction of species having extreme trait values or having level of generalization similar to those of the natives only slightly affected native population densities (top, bottom, and vertically centered areas of Fig. 2B). Moreover, when the introduced species has a trait value that falls far outside the range of resident traits, its invasiveness and impacts become trivial because it is situated far from the resource optimum and thus suffers from the lack of resources (Fig. S1). For 89% of the studied cases, the introduction of the alien species made the total population density decline (Fig. S2).


Invading a mutualistic network: to be or not to be similar
(A) Invasiveness and (B) impact of the invader as a function of its relative trait value and generalization level ratio, relative to those of the native community. Invasiveness and impact values represent the average over 100 medium‐size networks. Lines represent the zero level of invasiveness under different introduction modes.
© Copyright Policy - creativeCommonsBy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4979722&req=5

ece32263-fig-0002: (A) Invasiveness and (B) impact of the invader as a function of its relative trait value and generalization level ratio, relative to those of the native community. Invasiveness and impact values represent the average over 100 medium‐size networks. Lines represent the zero level of invasiveness under different introduction modes.
Mentions: Both the generalization level of the invader and its trait had an effect on the invasion success (Fig. 2). In general, species having the level of generalization similar to that of the natives are more likely to be invasive (vertically centered area of Fig. 2A). Species having extreme trait values but a high level of generalization also have high invasiveness (top‐right and bottom‐right corners of Fig. 2A). Species that are extreme specialist with extreme trait values also tend to be more invasive than those with trait value similar to most of the native species (extreme left area of Fig. 2A). Although the trait of the invader and its level of generalization can affect the population density of the native community, the overall impact of the invasion is small, reducing the total population size of the entire native community by about 1% (Fig. 2B). Highly generalist species having trait values similar to those of native species have the highest impact on the native community (center‐right area of Fig. 2B). The impact is also high for extreme specialist species having trait values similar to natives (center‐left area of Fig. 2B). The introduction of species having extreme trait values or having level of generalization similar to those of the natives only slightly affected native population densities (top, bottom, and vertically centered areas of Fig. 2B). Moreover, when the introduced species has a trait value that falls far outside the range of resident traits, its invasiveness and impacts become trivial because it is situated far from the resource optimum and thus suffers from the lack of resources (Fig. S1). For 89% of the studied cases, the introduction of the alien species made the total population density decline (Fig. S2).

View Article: PubMed Central - PubMed

ABSTRACT

Biological invasion remains a major threat to biodiversity in general and a disruptor to mutualistic interactions in particular. While a number of empirical studies have directly explored the role of invasion in mutualistic pollination networks, a clear picture is yet to emerge and a theoretical model for comprehension still lacking. Here, using an eco‐evolutionary model of bipartite mutualistic networks with trait‐mediated interactions, we explore invader trait, propagule pressure, and network features of recipient community that contribute importantly to the success and impact of an invasion. High level of invasiveness is observed when invader trait differs from those of the community average, and level of interaction generalization equals to that of the community average. Moreover, multiple introductions of invaders with declining propagules enhance invasiveness. Surprisingly, the most successful invader is not always the one having the biggest impact on the recipient community. The network structure of recipient community, such as nestedness and modularity, is not a primary indicator of its invasibility; rather, the invasibility is best correlated with measurements of network stability such as robustness, resilience, and disruptiveness (a measure of evolutionary instability). Our model encompasses more general scenarios than previously studied in predicting invasion success and impact in mutualistic networks, and our results highlight the need for coupling eco‐evolutionary processes to resolve the invasion dilemma.

No MeSH data available.