Directions for future study
We propose future research directions to improve our understanding of
the impact of the longitudinal environmental gradient across the
Palearctic region on organisms, populations, species, communities and
ecosystems: We hypothesize that biogeographic and macro-ecological
patterns that were found over latitudinal gradients, for example,
species diversity (Mittelbach et al. 2007; Condamine et
al. 2012) and body size (Bergmann’s rule; Olson et al. 2009),
may also hold true across the Palearctic longitudinal gradient.
Consequently, we call for broad examination of longitudinal gradients in
a variety of taxonomic groups, communities, food-webs and ecosystems,
Specifically, we hypothesize that this environmental gradient also
affects various properties of bird migration (Briedis et al.2020), including migration distance, direction, timing and
over-wintering areas of different migratory populations and species
across the Palearctic.