Measures for phenology and range shifts
The start of the growing season in Europe, including Finland, has
advanced over the past decades (Menzel & Fabian 1999; Helama et
al. 2020), and suitable conditions for seasonally recurring
life-history events now often occur earlier than before. To investigate
the strategy of adjusting phenology in situ, we focus on the
phenological timing of adult flight period, with the assumption of
advanced flight period mirroring an adaptive response.
The area of Finland extends over a ca. 1100 km latitudinal gradient
across boreal and subarctic climates and is topographically relatively
homogenous. The climatic isoclines roughly follow latitudes (Ahtiet al. 1968), but they are currently shifting northwards due to
climate change (Jylhä et al. 2010). Species range shifts as a
response to climate change should thus be observable in Finland through
colonization of new suitable areas north of their previous distribution
(cf. Pöyry et al. 2009). To study the strategy of colonizing new
suitable areas, we focus on measuring shifts in the northern range
boundary (NRB).