Global warming intensifies the interference competition by a poleward-expanding invader on a native dragonfly species

Abstract

Rapid climate warming has boosted biological invasions and the distribution or expansion polewards of many species: this can cause serious impacts on local ecosystems within the invaded areas. Subsequently, native species may be exposed to threats of both interspecific competition with invaders and temperature rises. However, effects of warming on interspecific interactions, especially competition between invader and native species remains unclear. To better understand the combined threats of biological invasions and warming, the effect of temperature on competitive interactions between two dragonfly species, the expanding Trithemis aurora from Southeast Asia and the Japanese native Orthetrum albistylum speciosum were assessed based on their foraging capacity. Although the stand-alone effect of temperature on foraging intake of the native dragonfly was not apparent, its intake significantly decreased with increasing temperatures when the invader T. aurora was present. Such reductions in foraging might lead to displacement of the native species through competition for food resources. This suggests that impacts of invader species against native species are expected to be more severe when interspecific competition is exacerbated by temperature rises.

Keywords: biological invasion; climate change; competitive displacement; ecological risk; foraging capacity/behaviour; interspecific interactions.

Figure 1.

Tendency of the distribution expansion of the invasive Trithemis aurora in Japan. Trithemis aurora, native to Southeast Asia and Taiwan (subtropical to tropical climates), was first detected in subtropical Ishigaki Island (southwest Japan) in 1981 [34,35], and then collected in Okinawa Island in 1983 [34], Amami-Oshima Island in 1988 [33], and the southern Kyushu district in 1999 [34]. Its distribution had spread to the Shikoku district by the late 2000s [33,36]. Furthermore, distribution of T. aurora extended to the central Kinki district (Nara Prefecture) in 2020. Solid blue and red circles show native of T. aurora and its invaded regions, respectively. The solid green circle indicates the latest area of T. aurora detection (Nara Prefecture, central Kinki district).

Figure 2.

A. Effects of the invading competitor T. aurora (Ta) on native O. albistylum speciosum (Oas). (a) Effect of temperature and presence of the invader on the foraging intake of the native species under two experimental conditions: stand-alone (blue), and cohabitation (purple); (b) number of attacks of T. aurora on O. albistylum speciosum. B. Effects of a native competitor on invading T. aurora. (c) Effects of temperature and presence or absence of Oas on the foraging intake of Ta under the two experimental conditions: stand-alone (red) and cohabitation (purple); (d) number of attacks of O. albistylum speciosum on T. aurora. Fitted curves and bands for 95% confidence interval with GLMMs and GLMs. In (a) and (c) the asterisks indicate that the interaction between temperature and the presence or absence of competing species is significant at p < 0.05 and n.s. indicates no significant difference.

Figure 3.

(a) Effect of the body size and the presence or the absence of T. aurora on the foraging intake of O. albistylum speciosum under the two experimental conditions: stand-alone (blue) and cohabitation (purple). (b) Effect of the body size and presence of O. albistylum speciosum on the foraging intake of T. aurora under the same two conditions: stand-alone (red) and cohabitation (purple). Fitted curves and bands for 95% confidence interval with GLMMs. The asterisks indicate that the interaction between temperature and the presence or the absence of competing species is significant at p < 0.05 and n.s. indicates no significant difference.