Measuring ecological specialization along a natural stress gradient using a set of complementary niche breadth indices

摘要

Aims: Ecological specialization refers to a restricted ecological niche breadth for a species, resulting from the trade-off between range of the resources it can exploit and efficacy in exploiting a specific resource. One hypothesis predicts that specialist species should be dominant in stressful environments, whereas generalist species should be dominant at less extreme environmental gradients. An alternative hypothesis states that specialization should be favoured in stable systems, and that ecological disturbances should affect specialist species negatively. These hypotheses have been poorly tested. Mediterranean coastal dune systems are characterized by strong sea-inland environmental gradients, ideal for tackling this challenge. We ask: (1) is distribution of specialist and generalist plant species related to this gradient; and (2) do different specialization indices indicate congruent or complementary patterns?