The evolution of local co-occurrence in birds in relation to latitude, degree of sympatry, and range symmetry

This study analyzes a large sample of occurrence records (7,834,063 checklists from the eBird project) of 887 passerine bird species distributed globally. Under the assumption that speciation and trait divergence rates are faster in temperate areas and that trait divergence does promote local secondary contact of newly evolved species, the expectaction is that local co-occurrence increases with latitude.Syntopy increased from the Southern to Northern Hemisphere and was positively related to sympatry and range symmetry.