Ecological plasticity by morphological design reduces costs of subordination: influence on species distribution

We studied the feeding behaviour of two subordinate tit species (Parus spp.) in two competitive contexts: feeding solitarily versus feeding in the presence of the dominant great tit. Considering ecological plasticity as the within-species component of mean behavioural performance associated with different morphologies in different species, we test the hypothesis that subordinate species with morphological designs allowing a greater ecological plasticity (e.g. blue tit whose hindlimb morphology is modified for greater leg flexion) may gain an advantage against subordinate species with a less plastic design (e.g. crested tit whose hindlimb morphology is modified for aid in leg extension) in a competitive context. Our results demonstrate that the blue tit has greater foraging abilities than the crested tit, as the former is able to modify its feeding behaviour in the presence of the dominant great tit significantly more than the crested tit. In light of these results we propose that some subordinate species can take advantage of their greater ecological plasticity against another less plastic, subordinate species, suggesting that ecological plasticity due to morphological design is a way of reducing costs of subordination as well as a novel, alternative mechanism explaining species distribution.