Abstract
The interactions between pairs of native and alien plants via shared use of pollinators have been widely studied. Community level studies however, are necessary in order to fully understand the factors and mechanisms that facilitate successful plant invasion, but these are still scarce. Specifically, few community level studies have considered how differences in invasion level (alien flower abundance), and degree of floral trait similarity between native and invasive species, mediate effects on native plant-pollinator communities. Here, we evaluated the role of alien species on overall plant-floral visitor network structure, and on species-level network parameters, across nine invaded coastal communities distributed along 205 km in Yucatán, México that vary in alien species richness and flower abundance. We further assessed the potential the role of alien plant species on plant-floral visitor network structure and robustness via computational simulation of native and invasive plant extinction scenarios. We did not find significant differences between native and alien species in their functional floral phenotypes or in their visitation rate and pollinator community composition in these invaded sites. Variation in the proportion of alien plant species and flower abundance across sites did not influence plant-pollinator network structure. Species-level network parameters (i.e., normalized degree and nestedness contribution) did not differ between native and alien species. Furthermore, our simulation analyses revealed that alien species are functionally equivalent to native species and contribute equally to network structure and robustness. Overall, our results suggest that high levels of floral trait similarity and pollinator use overlap may help facilitate the integration of alien species into native plant-pollinator networks. As a result, alien species may also play a similar role than that of natives in the structure and stability of native plant and pollinator communities in the studied coastal sand dune ecosystem.
Highlights
Alien plant species can alter a vital ecosystem function by disrupting mutualistic interactions between native plant species and their pollinating partners [1,2,3]
Current understanding of alien species effects still strongly relies on studies of interactions between an invasive and one, or very few, native species [4, 7], typically at a single location ([8], but see [15,16,17])
While some have shown that alien plant species can affect network specialization, modularity, nestedness and robustness [19, 20], others have found little to no effect on network structure [5, 21]
Summary
Alien plant species can alter a vital ecosystem function by disrupting mutualistic interactions between native plant species and their pollinating partners [1,2,3]. Alien plants can decrease floral visitation, pollen deposition and reproductive success of native plant species ([4,5,6]; but see [7]) as well as alter the structure of community-level plant-pollinator interactions (i.e. network structure; [8,9,10,11]) These effects can in turn affect the long-term stability and functionality of native plant communities [12,13,14]. In order to gain a more complete understanding of the consequences of alien species effects on native plant-pollinator interactions it is imperative to evaluate how their effects vary across various levels of alien species richness and floral abundance even in highly invaded ecosystems [17, 22]. Few studies have simultaneously considered both, network structure and species-level effects, limiting our understanding of overall alien species effects on native plant-pollinator communities
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