The classification of some Turdus species, such as the Naumann’s and dusky thrush complexes and the red-throated and black-throated thrush complexes, is controversial. Herein, we used molecular data and morphological characters to review the taxonomy of these thrush complexes and analyze the genetic differentiation between them. Herein, we examined the genetic characteristics of 13 microsatellite loci in all individuals and total of 129 alleles were detected. In parallel, we have a further judgment on their classification status by measuring 5 morphological features (tail length, wing length, toe length, claw length and instep length).

Collection of microsatellite loci 

We characterized 13 microsatellite loci for the targeted thrush species; the loci were identified originally isolated from therelated species Turdus merula. The 5' end of each forward primer was connected to a fluorescent dye-labeled M13, and the fluorescent label was FAM or JOE. The amplification profile of the microsatellite loci was standardized as follows: 5.0 μl of Ex Taq DNA polymerase (TaKaRa, Dalian), 3.5 μl of H₂O, 0.2 μl of BSA, 0.1 μl (10 pmol/μl) of each primer, 0.1 μl (10 pmol/μl) of M13 and 3.5 μl (20 ng) of genomic DNA. The PCR conditions were as follows: initial denaturation at 94°C for 3 min; 20 cycles of 94°C for 30 s, the annealing temperature for 30 s and 72°C for 45 s; 15 cycles of 94°C for 30 s, 60°C for 30 s and 72°C for 45 s; and a final extension at 72°C for 10 min. Amplicons were sized by a service provider (Shenggong BioTech) using capillary electrophoresis with an ABI 3730xl DNA analyzer. Alleles were scored using GeneMapper software version 4.0 (Applied Biosystems Inc.).

Morphometric data

A total of 77 individuals, including Naumann’s thrush (N=33), the dusky thrush (N=8), the red-throated thrush (N=33), and the black-throated thrush (N=3), were used in the morphometric analysis. Five morphological features, tail length, wing length (maximum chord), toe length, claw length and instep length, were measured using an electronic vernier caliper (with an accuracy of 0.001).

All lengths are measured in cm.