Effect of barriers and distance on song, genetic, and morphological divergence in the highland endemic Timberline Wren (Thryorchilus browni, Troglodytidae).

Andrés Camacho-Alpízar,Eric J Fuchs,Gilbert Barrantes

doi:10.1371/journal.pone.0209508

Abstract

Populations may become isolated by distance, geographic barriers or both. Isolated populations often diverge in behavioral, morphological and genetic traits as a result of reduced inter-population gene flow. Highland species commonly present naturally fragmented distributions that confine populations to the highest mountain peaks, isolated by mountain passes and distance. The endemic Timberline Wren (Thryorchilus browni) inhabits the highlands of the Talamanca mountain range, including western Panama, and the highest peak in the Central Volcanic mountain range of Costa Rica. Using microsatellites and song recordings we studied the effect of a geographic barrier and distance on song, genetic and morphological divergence among four populations in Costa Rica. A lowland mountain pass resulted in the largest genetic, vocal, and morphological (bill length) differences among populations, likely due to reduce the gene flow. Cultural drift and assortative mating by females selecting songs from their own population likely accentuates the effect of isolation and limited gene flow between populations. This pattern of population divergence has been found in other Neotropical highland birds, but over larger geographical scales. We conclude that mountain passes and distance both reduce gene flow between populations in recently-isolated highland species with restricted distributions.

Highlights

IntroductionAbsent or limited gene flow will result in some degree of inter-population divergence [1]
For most species, absent or limited gene flow will result in some degree of inter-population divergence [1]
Three sites were located within the Talamanca Mountain Range: Cerro Buena Vista (CBV: 9 ̊ 33’N, 83 ̊ 44’W), Cerro Vueltas (CV: 09 ̊ 37’N, 83 ̊ 51’W) and Cerro Chirripo (CCH: 09 ̊ 28’N, 83 ̊ 29’W); and the fourth site was in the Irazu Volcano (IV: 09 ̊ 59’N, 83 ̊ 52’W), located in the Central Volcanic mountain range (Fig 1)

Summary

Introduction

Absent or limited gene flow will result in some degree of inter-population divergence [1]. Multiple factors, including morphology and behavior, may restrict gene flow [2,3]; spatial separation and barriers are often considered the two main factors limiting gene flow among populations [1,4]. In the absence of physical or ecological barriers, dispersal limitation restricts gene flow in animals, increasing genetic structure and phenotypic differences among populations [5,6]. Gene flow distances will depend on the social structure and mating system of each species [7,8].

Methods

Results

Conclusion