基于形态特征判定五种鹬类性别的可靠性

Reliability of Identifying Gender of Five Sandpipers Using Morphologic Measurements

快速准确地鉴定两性同型鸟类个体性别在鸟类生态学研究中具有重要意义。本文选择2008年春季迁徙期在崇明东滩停歇的大滨鹬(Calidris tenuirostris)、红腹滨鹬(C.canutus)、红颈滨鹬(C.ruficollis)、尖尾滨鹬(C.acuminata)及翘嘴鹬(Xenus cinereus)5种两性同型的鹬类,用分子生物学方法进行性别鉴定,并基于个体的形态特征(体重、翅长、喙长、头喙长及跗跖长)采用判别分析方法对性别进行判定。结果表明,尖尾滨鹬雄性各形态特征均显著大于雌性,其他4种鹬类则相反。5种鹬类形态特征的性别差异指数在0.5%~25.3%之间,重叠度在29.4%~98.6%之间。5种鹬类判别分析判定性别的准确率在(0.69±0.06)^(0.96±0.01)之间,其中,尖尾滨鹬判别准确率(0.96)最高,翘嘴鹬判别准确率(0.69)最低。形态特征在两性间的差异程度影响性别的判别准确率。另外,两性性比对性别判别的准确率也有影响:性比偏雄性鸟类的雄性判别准确率高于雌性,而性比偏雌性鸟类的雌性判别准确率高于雄性。采用判别分析估测的性比与分子生物学鉴定结果相似,表明判别分析在判定种群的性比方面具有较高的可靠性。

Rapid and accurate identification of the gender of monomorphic birds, which are difficult to determine by direct observation, is of great significance in the study of avian ecology. Discriminant analysis according to morphological characteristicshas has been frequently used for sexing individuals in monomorphic species because of its fast, simple procedure and high accuracy. This study used discriminant analysis to identify the gender of five monomorphic sandpiper species at Chongming Dongtan, a stopover site of the East Asian-Australasian Flyway （EAAF）： Great Knots Calidris tenuirostris, Red Knots C. canutus, Red-necked Stints C. ruficollis, Sharp-tailed Sandpipers C. acuminate, and Terek Sandpipers Xenuscinereus. Five morphological characteristics （body weight, wing length, bill length, head and bill length, and tarsus length） were measured during spring migration in 2008. Firstly, we identified the gender of the individuals in the five species using molecular biological method. Then we used independent t tests to compare the difference in the morphological characteristics between the males and females. The degree of overlap in morphological characteristics between males and females as well as the sexual dimorphism index were calculated for each species. Finally, we used discriminant analysis to deduce the gender of each individual according to morphological measurements and compared the results with that from molecular biology method. The morphological characteristics of the males were significantly larger than that of the females in Sharp-tailed Sandpipers, while the females were larger than the males in other four species （Table 1）. The sexual size dimorphism index of morphological characteristics in the five sandpiper species varied in 0.5%﹣25.3% （Table 2）, and the interspecific overlaps of morphological characteristics varied in 29.4%﹣98.6% （Table 1）. The accuracy of gender identification using discriminant analysis was 0.69 ± 0.06﹣0.96 ± 0.01, with the highest in the Sharp-tailed Sandpipers （96%） while the lowest in the Terek Sandpipers （69%, Table 3）. The difference in morphological characteristics between the genders affected the accuracy of gender discrimination. In addition, sex ratio might also affect the accuracy of gender discrimination. The sex ratio estimated using discriminant analysis is similar to that using molecular biological method （Table 3）, indicating that the discriminant analysis has a high reliability in determining the sex ratio of population.