Genetic diversity and population structure of the critically endangered Yangtze finless porpoise (Neophocaena asiaeorientalis asiaeorientalis) as revealed by mitochondrial and microsatellite DNA.

Minmin Chen,Rui Ruan,Jinsong Zheng,Qingzhong Zhao,Min Wu,Ding Wang

doi:10.3390/ijms150711307

Abstract

Ecological surveys have indicated that the population of the critically endangered Yangtze finless porpoise (YFP, Neophocaena asiaeorientalis asiaeorientalis) is becoming increasingly small and fragmented, and will be at high risk of extinction in the near future. Genetic conservation of this population will be an important component of the long-term conservation effort. We used a 597 base pair mitochondrial DNA (mtDNA) control region and 11 microsatellite loci to analyze the genetic diversity and population structure of the YFP. The analysis of both mtDNA and microsatellite loci suggested that the genetic diversity of the YFP will possibly decrease in the future if the population keeps declining at a rapid rate, even though these two types of markers revealed different levels of genetic diversity. In addition, mtDNA revealed strong genetic differentiation between one local population, Xingchang–Shishou (XCSS), and the other five downstream local populations; furthermore, microsatellite DNA unveiled fine but significant genetic differentiation between three of the local populations (not only XCSS but also Poyang Lake (PY) and Tongling (TL)) and the other local populations. With an increasing number of distribution gaps appearing in the Yangtze main steam, the genetic differentiation of local populations will likely intensify in the future. The YFP is becoming a genetically fragmented population. Therefore, we recommend attention should be paid to the genetic conservation of the YFP.

Highlights

The Yangtze finless porpoise (YFP, Neophocaena asiaeorientalis asiaeorientalis) which was reclassified as a subspecies of the narrow-ridged finless porpoise (N. asiaeorientalis) in 2009 [1], inhabits only the middle and lower reaches of the Yangtze River and the adjoining Poyang and Dongting Lakes [2] (Figure 1)
Our results indicated that the Dongting Lake (DT) was significantly differentiated from the XCSS, Poyang Lake (PY), and TL populations, no significant genetic differentiation was observed among the DT, HHPZ, and EZHS populations, suggesting that a certain level of gene flow has remained between the DT, HHPZ, and EZHS populations over the last several generations
By using combined mitochondrial DNA (mtDNA) and microsatellite markers, we have obtained a detailed understanding of the genetic diversity and population structure of the YFP

Summary

Introduction

The Yangtze finless porpoise (YFP, Neophocaena asiaeorientalis asiaeorientalis) which was reclassified as a subspecies of the narrow-ridged finless porpoise (N. asiaeorientalis) in 2009 [1], inhabits only the middle and lower reaches of the Yangtze River (from Yichang to Shanghai) and the adjoining Poyang and Dongting Lakes [2] (Figure 1). The YFP population has declined remarkably over the last two decades, especially in the Yangtze main stream, decreasing from more than 2500 individuals in 1991 [5] to fewer than 1225 in 2006 [6]. According to the 2006 Yangtze Freshwater Dolphin Expedition (YFDE2006), the total population size, including those in the Poyang and Dongting Lakes, was approximately 1800 [6], whereas the 2012. Yangtze Freshwater Dolphin Expedition (YFDE2012) revealed that at the end of 2012, there were only approximately 1040 individuals remaining, including 500 in the Yangtze main stream, 450 in the Poyang Lake and 90 in the Dongting Lake [7]. Owing to the small population size, sharply declining population, and high probability of extinction, the YFP was recently reclassified as a Critically

Results

Discussion

Conclusion