Abstract
Understanding how eco-evolutionary processes and environmental factors
drive population differentiation and adaptation are key challenges in
evolutionary biology of relevance for biodiversity protection.
Differentiation requires at least partial reproductive separation, which
may result from different modes of isolation such as geographic
isolation (allopatry) or isolation by distance (IBD), resistance (IBR),
and environment (IBE). Despite that multiple modes might jointly
influence differentiation, studies that compare the relative
contributions are scarce. Using RADseq, we analyse neutral and adaptive
genetic diversity and structure in 11 pike (Esox lucius) populations
along a latitudinal gradient (54.9 - 63.6°N), to investigate the
relative effects of IBD, IBE and IBR, and to assess whether the effects
differ between neutral and adaptive variation, or across structural
levels. Patterns of neutral and adaptive variation differed, likely
reflecting that they have been differently affected by stochastic and
deterministic processes. The importance of the different modes of
isolation differed between neutral and adaptive diversity, yet were
consistent across structural levels. Neutral variation was influenced by
interactions among all three modes of isolation, with IBR (seascape
features) playing a central role, wheares adaptive variation was mainly
influenced by IBE (environmental conditions). Taken together, this and
previous studies suggest that it is common that multiple modes of
isolation interactively shape patterns of genetic variation, and that
their relative contributions differ among systems. To enable
identification of general patterns and understand how various factors
influence the relative contributions, it is important that several modes
are simultaneously investigated in additional populations, species and
environmental settings.