Speciation in the White-breasted Nuthatch (Sitta carolinensis): a multilocus perspective

Area of Science:

• Evolutionary Biology
• Phylogeography
• Ornithology

Background:

• Phylogeographic studies infer evolutionary processes from gene lineage distributions.
• Single-gene analyses offer insights into diversification but not definitive evolutionary mechanisms.
• The White-breasted Nuthatch (Sitta carolinensis) was previously found to have four distinct clades based on mitochondrial DNA.

Purpose of the Study:

• To explore the evolutionary history of Sitta carolinensis using a multilocus dataset.
• To resolve the evolutionary mechanisms driving diversification in S. carolinensis.
• To validate previous findings from single-locus studies with more comprehensive genetic data.

Main Methods:

• Utilized a multilocus (20 loci) DNA dataset for Sitta carolinensis.
• Applied principal component, clustering, and species tree analyses.
• Conducted coalescent analyses and tested isolation-migration models.

Main Results:

• The multilocus data confirmed the four distinct lineages previously identified in single-locus studies.
• Coalescent analyses indicated that isolation, rather than gene flow, was the dominant evolutionary force.
• All divergence events within S. carolinensis were linked to Pleistocene glacial cycles.

Conclusions:

• Multilocus data robustly support the existence of four distinct lineages within S. carolinensis.
• Isolation has been the key evolutionary mechanism shaping genetic variation and divergence.
• Pleistocene glacial cycles were the primary drivers of diversification in this species.