Figure 2 Bayesian and maximum likelihood (ML) trees for dunlin
mitochondrial DNA haplotypes from Jiangsu in different years and from
different breeding areas. (a) 2015 and (b) 2016. Numbers near nodes are
posterior probabilities from Bayesian analysis and bootstrap values from
ML analysis (BI/ML). Colored circles indicate subspecies of birds
sampled in breeding areas or at Jiangsu (see key), which are grouped
into Alaskan (ALA, pink shading) and Beringian (BER, yellow shading)
lineages. The number of individuals from different lineages in different
years is in parentheses.
Sixty-seven individuals were identified as males and 99 individuals were
identified as females using a molecular method. The proportion of sexed
birds decreased from 85.90% in 2015 to 57.23% in 2016. Owing to
incomplete morphological data, the number of individuals was different
in different morphological statistics. Scatter plots indicated little
overlap in bill and wing lengths between the two years (Fig. 3). For
males, wing length and bill length data conformed to a normal
distribution, and both were significantly different between years (wing
length, t = 3.004, df = 44, two-tailed P = 0.004;
bill length, t = 7.612, df = 44, two-tailed P< 0.001). Wing and bill lengths of males were shorter in 2015
than in 2016 (Fig. 3b). For females, wing length data conformed to a
normal distribution, whereas bill length data did not fit a normal
distribution. Only bill length was significantly different between the
two years for females
(wing
length, t = 1.657, df = 84,
two-tailed P = 0.105;
Mann–Whitney U-test: bill length, Z = –2.126, P =
0.033). Female dunlins in 2015 tended to have longer bills and wings
than those in 2016 (Fig. 3a).