Climate change as a driver of insect invasions: Dispersal patterns of a dragonfly species colonizing a new region

Abstract

The dragonfly Trithemis kirbyi Sélys, 1891 recently colonized Western Europe from North Africa. Since its first record in the Iberian Peninsula in 2007, the species has been spreading northward and has become naturally established in the central and eastern Iberian Peninsula, the Balearic Islands and southern France. Despite its worldwide distribution, its rapid colonization of the western Mediterranean area occurred only very recently. The aims of this study were to evaluate (1) whether the species’ colonization of the western Mediterranean is related to climate change and rising temperatures, specifically the summer warming peaks that have occurred in the last decade, (2) which climatic variables have most influenced its distribution and dispersal, and (3) its potential future dispersal and colonization capacity towards the eastern Mediterranean. We found that the dispersal and recent establishment of T. kirbyi in southwestern Europe strongly depends on increasing temperatures, particularly summer temperature peaks, which has allowed this species to disperse farther and more effectively than during years with average summer temperatures. The most important variable in the suitability models is the minimum temperature of the coldest month, which, in recent decades, has become less of a limiting factor for ectotherms. According to the models, suitable areas for the species are currently found throughout the eastern Mediterranean parts of Europe, and it is likely that it can naturally colonize these areas as it did in the Iberian Peninsula. Trithemis kirbyi is a model of how climate change and observed rising temperatures have turned previously inhospitable regions into suitable areas for exotic species, which may successfully colonize them naturally if they can reach these promising lands on their own. However, this study serves as a warning that such species can also colonize these new regions with a little help from unsuspecting means, which are often responsible for the increasingly common presence of invasive, noxious taxa in Europe.

A Warm Welcome to the Alps—The Northward Expansion of Trithemis annulata (Odonata, Libellulidae) in Italy

“…As temperature increases, higher latitudes and elevations are expected to warm, hence receiving more warm-tolerant species [15]. It is in keeping with this hypothesis that in Europe, many Odonata species have already expanded their distribution northward [5,7,9,13]. In South Korea, Shin et al [11] documented the northward expansion of Ischnura senegalensis between 1980 and 2020.…”

“…Thus, T. annulata is advancing rather fast in Italy, particularly considering the 34 km/year observed over 7 years in northern Italy. However, for its congener Trithemis kirbyi Gil-Tapetado et al [13] reported that this species has a high dispersal potential and can disperse an average of 430 km per year and this ability to cross large distances quickly has been confirmed by sightings of this species on isolated islands in the Mediterranean basin [54]. When considering Odonata in general, the advance of the northern limit is slower.…”

“…Also, the distribution of other Odonata species has successfully been modelled using MaxEnt and bio 5 is one of the most important variables for predicting species distributions of Palearctic Odonata [65]. In contrast, for Trithemis kirbyi the most important bioclimatic variable explaining the distribution of suitable areas was the minimum temperature of the coldest month (bio6) [13], and for Ischnura senegalensis, the annual mean temperature and the maximum temperature of the warmest month contributed a total of 79.9% of habitat suitability [11].…”

“…Many authors have suggested that Odonata are ideally suited to study the effects of climate change [4,9,10], and the effects of recent climate warming have been investigated in a large number of publications [5,7,9,[11][12][13]. Because species range shifts primarily depend on thermal niche, geographical ranges are expected to shift as a response to warming [10].…”

“…Thus, the analysis of the recent rapid range expansion of a dragonfly, for which a considerable amount of distributional data is available, will likely shed some light on the speed, mechanisms and direction of such a distributional shift. These data are important but, unfortunately, detailed accounts of the expansion of single species are rare in the literature (e.g., [11,13,30]). However, detecting changes using fragmented samples of data and identifying potential causes for those changes is challenging, and there are considerable uncertainties regarding the speed of distributional shifts [15].…”