Exploring genetic diversity and population structure of the Little Tern (Sternula albifrons) in Taiwan based on mtDNA and ddRAD sequencing data

In this study, the Little Tern (Sternula albifrons) populations in Taiwan were examined based on two different types of data: the mitochondrial control region DNA sequences and double digest Restriction-site Associated DNA (ddRAD) sequencing data. The feather samples were collected from 59 chicks across four known breeding colonies located at western (Penghu and Changhua) and eastern (Yilan and Hualien) coasts of Taiwan. The results obtained were consistent from the analyses and did not cluster the samples into two geographical groups with respect to the West and East of Taiwan. Furthermore, the AMOVA analyses and pairwise phi-ST or FST estimations based on both types of data revealed little to no population differentiation among populations and between regions. The findings of this study suggested a high population connectivity among the breeding colonies in Taiwan. Additionally, the obtained control region sequences of the Little Tern from Taiwan were compiled with those from Japan deposited in the GenBank to compare the genetic diversity and to examine the phylogeographic break that may shape the diversity pattern of the Little Tern in eastern Asia. The resulting haplotype network did not clearly separate Taiwanese and Japanese populations but the three most common haplotypes were prevalent for mainland Japan, Okinawa and Taiwan samples, respectively. The Little Tern populations may be frequently connected but with some restrictions on their gene flow that caused moderate to great differentiation among the three populations, which further supported by the AMOVA analyses, pairwise phi-ST estimations and the positive yet significant isolation by distance pattern.