How far could the alien boatman Trichocorixa verticalis verticalis spread? Worldwide estimation of its current and future potential distribution

Abstract

Invasions of alien species are considered among the least reversible human impacts, with diversified effects on aquatic ecosystems. Since prevention is the most cost-effective way to avoid biodiversity loss and ecosystem problems, one challenge in ecological research is to understand the limits of the fundamental niche of the species in order to estimate how far invasive species could spread. Trichocorixa verticalis verticalis (Tvv) is a corixid (Hemiptera) originally distributed in North America, but cited as an alien species in three continents. Its impact on native communities is under study, but it is already the dominant species in several saline wetlands and represents a rare example of an aquatic alien insect. This study aims: i) to estimate areas with suitable environmental conditions for Tvv at a global scale, thus identifying potential new zones of invasion; and ii) to test possible changes in this global potential distribution under a climate change scenario. Potential distributions were estimated by applying a multidimensional envelope procedure based on both climatic data, obtained from observed occurrences, and thermal physiological data. Our results suggest Tvv may expand well beyond its current range and find inhabitable conditions in temperate areas along a wide range of latitudes, with an emphasis on coastal areas of Europe, Northern Africa, Argentina, Uruguay, Australia, New Zealand, Myanmar, India, the western boundary between USA and Canada, and areas of the Arabian Peninsula. When considering a future climatic scenario, the suitability area of Tvv showed only limited changes compared with the current potential distribution. These results allow detection of potential contact zones among currently colonized areas and potential areas of invasion. We also identified zones with a high level of suitability that overlap with areas recognized as global hotspots of biodiversity. Finally, we present hypotheses about possible means of spread, focusing on different geographical scales.

Figure 1. Current known distribution of Trichocorixa verticalis verticalis.

Map of native (triangles) and invaded (circles) distribution areas of Trichocorixa verticalis verticalis, with a close-up of the Iberian Peninsula and Morocco.

Figure 2. Current potential distribution.

Map of worldwide potential distribution of Trichocorixa verticalis verticalis based on current climatic conditions.

Figure 3. Climatic suitability within the current potential distribution.

Map of worldwide current potential distribution of Trichocorixa verticalis verticalis. showing the climatic favorability from red (very high suitability) to light blue (very low suitability). These values were calculated applying Mahalanobis distances within the area defined in Fig. 1.

Figure 4. Future potential distribution of Trichocorixa verticalis verticalis.

This map shows the worldwide future potential distribution of Trichocorixa verticalis verticalis. Predictions were based on the Community Climate Model scenario (CCM3) for the year 2100. The concordance between current and future periods is shown in green. Areas labeled in brown are new areas with environmental suitability for future conditions, while yellow cells represent areas where suitable climatic conditions are predicted to be lost in the future.