Climate Warming as an Explanation for the Recent Northward Range Extension of Two Dragonflies, <i>Pachydiplax longipennis</i> and <i>Perithemis tenera</i>, into the Ottawa Valley, Eastern Ontario

Abstract

Climate warming is accepted as an explanation for the recent appearance of Blue Dasher, Pachydiplax longipennis (Burmeister, 1839), and Eastern Amberwing, Perithemis tenera (Say, 1839), in the Ottawa region, as this range expansion meets 6 criteria: (1) the climate in the newly occupied territory has warmed sufficiently to allow colonization; (2) a new range expectation based on the amount of climate warming is met; (3) other factors potentially promoting spread are excluded; (4) the possibility that range extension is a result of difficulty of observation and/or insufficient fieldwork in earlier times is excluded; (5) there is ample evidence for establishment; and (6) spread has been in the direction of the warmer territory or within it. By 2000, the mean daily temperature in the Ottawa region had increased by about 2°C since 1880 and about 1.1°C since 1960. This would allow new zonal boundaries and the prediction of expansion from a well-defined and long-occupied area into the Ottawa Valley. The two species entered this region in 2008–2012 and, subsequently, became well established.