Taxonomy, Distribution, and Evolution of Golden Plovers (Pluvialis dominica and Pluvialis fulva)

Abstract

A discriminant function analysis of specimen measurements separates 96% of two forms of Lesser Golden Plover in breeding plumage, previously described as subspecies. The forms breed sympatrically in northwest Alaska and are not isolated by habitat, but the incidence of specimens phenotypically intermediate between two forms is no higher there than in areas of allopatry. The absence of a cline of intergrades or of a hybrid zone indicates that the forms are reproductively isolated through assortative mating and are separate species. To explain the process of speciation in these very similar forms, I propose that the evolution of genetically controlled and markedly different migration routes (Pluvialis dominica to South America and Pluvialis fulva to the central and western Pacific and Indian oceans) during Pleistocene glacial isolation may have selected against hybrids during subsequent secondary contact of populations. This would leat to adaptations in behavior and plumage, such as the difference in male undertail coverts reported here, that would produce assortative mating and reproductive isolation in sympatry. Thus, the requirements of migration and winter range drive the process of speciation.