José Antonio Carbonell, Josefa Velasco, Andrés Millán, Andy J. Green, Cristina Coccia, Simone Guareschi and Cayetano Gutiérrez-Cánovas

Biological invasions are one of the most important causes of biodiversity loss and ecosystem change worldwide, and especially affect aquatic habitats. However, it is still unclear how biological invasions may interact with local abiotic stressors, which are expected to increase as global change intensifies. Furthermore, we know little about the response of native communities of insects to biological invasions, despite the huge contribution of insects to global animal biodiversity.

The aim of the present work is to investigate the impact of the invasive water boatman Trichocorixa verticalis verticalis on the co-existence patterns of three native boatman species along a salinity gradient, and determine which ecological community assembly rules are driving these patterns. To achieve that, we characterised the habitat specialisation and functional niches of each species from physiological and biological characteristics, respectively, and their degree of overlap. Secondly, we used field data to compare the coexistence patterns of native and invasive species in invaded and non-invaded areas of southern Iberia and northern Morocco. Finally, we tested if habitat filtering (stress gradient segregates species into different habitats allowing regional coexistence) or niche differentiation (different resource exploitation allows the coexistence of species in the same habitat) assembly rules mediate their coexistence.

We found that in non-invaded areas habitat filtering drives habitat segregation of species along the salinity gradient, with a lower contribution of niche differentiation. According to our results, the presence of the invasive insect modifies the distribution and coexistence patterns of native boatmen. In invaded areas, niche differentiation seems to be the main mechanism preventing competition among the invasive and native species, enabling coexistence and resource partitioning.

The combined study of functional niche similarity and abiotic stressor tolerance of invasive and native species can improve our understanding of the effects of invasive species along abiotic stress gradients. Our novel approach may increase our capacity to predict the outcomes of other biological invasions in a global change context.

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Image: Trichocorixa verticalis verticalis. (photo by José A. Carbonell)