Phenotypic Variation in Mangrove Cuckoo (Coccyzus minor) across Its Geographic Range.

John D Lloyd

doi:10.1371/journal.pone.0152141

Abstract

Mangrove Cuckoo (Coccyzus minor) exhibits substantial phenotypic variation across its geographic range, but the significance of this variation for taxonomy remains unresolved. Using measurements of bill size and ventral color recorded from 274 museum specimens, I found that variation in these traits was clinal. No named subspecies was reciprocally diagnosable from all others, and none was distinguishable from the nominate form, such that previously recognized subspecific distinctions are invalid. Greatest differences in phenotype occurred between populations in Florida, the Bahamas, and the Greater Antilles–characteristically small-billed–and those in the Lesser Antilles, which had larger bills. Phenotypically intermediate individuals on the geographically intermediate islands of Barbuda and Antigua linked these two extremes. Individuals intermediate in bill size and color also characterized populations from throughout the remainder of the range in northern South America and Middle America. Mechanisms maintaining the fairly pronounced phenotypic differences between nearby populations of Greater and Lesser Antillean birds are unknown, yet the geographic proximity of these populations suggests that they probably persist despite occasional gene flow, and may be adaptive.

Highlights

Mangrove Cuckoo (Coccyzus minor) exhibits extensive variation in phenotype, especially in bill size, bill shape, and color of the ventral plumage [1]
One approach has been to classify populations into recognizable subspecies, an effort that, at its zenith, yielded 14 named forms [2]. This approach was criticized in a subsequent review of the taxonomy of Mangrove Cuckoo, which, based on visual inspection of a series of specimens, argued that all phenotypic variation in the species was random with respect to geography [3]
I collected data on morphology and plumage color for 12 of the 14 subspecies listed by Peters [2], which was the most recent major treatment of subspecific variation in Mangrove Cuckoo

Summary

Introduction

Mangrove Cuckoo (Coccyzus minor) exhibits extensive variation in phenotype, especially in bill size, bill shape, and color of the ventral plumage [1]. One approach has been to classify populations into recognizable subspecies, an effort that, at its zenith, yielded 14 named forms [2]. This approach was criticized in a subsequent review of the taxonomy of Mangrove Cuckoo, which, based on visual inspection of a series of specimens, argued that all phenotypic variation in the species was random with respect to geography [3]. Most avian taxonomies (e.g., [4]) treat the species as monotypic, questions persist about whether some populations may be distinctive enough to warrant recognition as subspecies [5]

Methods

Results

Conclusion