以排遺DNA標定法探討金門地區兩條溪流流域歐亞水獺之族群結構

Abstract

本實驗利用非侵害性分子調查方法研究金門地區歐亞水獺的族群結構及空間分佈。自2001年二月到十一月，每季於金門本島的兩個流域採集新鮮排遺，並從其中萃取DNA，再利用7組微衛星基因座及SRY基因辨識排遺樣本的來源個體與性別。自343份排遺樣本中，成功地增幅出222(65％)份的所有基因座，並被辨識為38個基因型。在此實驗中，因等位基因遺漏（allelic dropout）造成各基因座中誤判基因型的機率小於0.005。由於根據試算，即使在由近親構成的族群中，任意兩隻個體為相同基因型的機率也小於0.01。因此，本實驗所用微衛星體基因的解析效果是足夠用來估計族群數量。成功辨識的38隻個體中有13隻（34％）為居留者（停留超過一季以上的個體），其中有6隻與7隻分別出現於兩個流域中。其餘的25隻為過境者（僅出現一季的個體）。這些流域的水獺密度為每公里河段1.5-1.8隻，若只考慮居留者則為每公里0.8-1.1隻，兩種密度的估計值皆高於其他研究文獻所估算的密度。雄性居留者的平均活動範圍約為2.3公里，雌性則約為1.3公里。此外，兩個流域各有兩群二到三隻雌性居留者同時活動於相同範圍，同一群內的個體並未出現在另一群的活動範圍中。根據基因分析及排遺分佈資料判斷，一個流域內的同一群雌性居留者類似家庭組成，另一流域內同一群個體的親緣關係則較不親近。雄性居留者的出現範圍未超過一個以上的雌性團體範圍。大多數出現位置相近的個體（包括居留者及過境者）彼此的親緣關係也有較親近的趨勢。由於兩個流域系統複雜程度不同，而在水系較複雜的流域中出現的過境者相對較多，推測較複雜的水域系統可能提供水獺較多的活動通道，以致有較多的過境者通過。

Noninvasive molecular methods were used to obtain data on the population structure and spatial organization of Eurasian otters (Lutra lutra) in Kinmen. DNA samples were extracted from fresh spraints collected in Kinmen every season from February to November 2001 and genotyped for a panel of 7 microsatellites and SRY gene to identify individual genotypes and sex. 222 (65%) of 343 spraints were successfully genotyped for the panel and 38 different genotypes (19 females and 19 males) were identified. The probability of false homozygotes came from allelic dropout was < 0.005 and the microsatellite panel with the probability of identity of < 0.01, even for siblings, was powerful enough to estimate the population size. 13 (34%) of 38 genotypes were residents (the individuals that were identified for more than one season), and each of the two streams accommodated six and seven residents respectively. The other 25 genotypes were floaters (the individuals that were only identified in one season). The density of 1.5-1.8 otters/km, or 0.8-1.1 otters/km for residents, was higher than that estimated in other studies. The mean active ranges of female and male residents were about 1.3 km and 2.3 km respectively. Female residents lived in exclusive group ranges, and each range was occupied by two to three females. According to the data of genetics and spraints distribution, females within the same group ranges were likely to be a family in one stream, but were less related in the other stream. The ranges of male residents overlapped with no more than one group range of female residents. Most of these otters, including residents and floaters, appeared in the same range tend to be more related to each other. There were relative more floaters identified along the stream with a more complex waterway system. The complexity of the waterways may help provide a good network of paths for floaters.