Phylogenetic analyses
An MJ haplotype network of COI was constructed using 108 sequences from
the species’ range (Figure 2a). This network inferred three genetic
groups, which were supported as distinct clades in the BI phylogenetic
tree (Figure S1.2); the archipelagic, northern, and southern clades
possibly reflected the three subspecies, L. c. superciliosus ,L. c. cristatus , and L. c. lucionensis , respectively
(Figure 1c). In this network, a split between the southern and
archipelagic clades was observed with nine mutational gaps. The northern
clade was genetically most distant from the southern clade and its major
haplotype (H1) was separated only by two mutational positions from one
of the archipelagic major haplotypes. A similar structure was supported
by the multi-locus network including both the mitochondrial and nuclear
loci. Two individuals appeared to be intermediate between the southern
and northern clusters (Figure 2b).
The southern clade was inferred as the basal lineage of the Brown Shrike
by the BI tree (Figure S1.2). The first split occurred between the
southern and the archipelagic/northern clades, around 0.80 [0.55,
1.10] million years ago (Mya), corresponding to the late Early to
Middle Pleistocene while the northern and the archipelagic clade
diverged around 0.32 [0.20, 0.47] Mya, during the Middle Pleistocene
(numbers within square brackets indicate 95% highest posterior
density).