台灣陸域蛇類之分布、預測與熱點分析

Abstract

瞭解生物地理分布範圍及與環境之關係，乃生物研究之重要基石。蛇類屬易滅絕物種，在棲地喪失與人為獵捕壓力下，野外蛇類的族群數量銳減。為了解台灣陸域蛇類之棲地偏好、分布範圍及保育現況，本研究結合蛇類分布資料庫及環境因子資料庫，利用Ecological-Niche Factor Analysis (ENFA) 進行37種蛇類（占所有陸域蛇種82.2%）之空間預測。本研究共採用8,866筆記錄點資料，所有資料共2,360個網格（占總網格數6.4%）。ENFA分析結果顯示台灣陸域蛇類在棲地選擇上並無一致偏好傾向，分布範圍主要受限於海拔高度、南向值、年均溫及月均溫變異係數，部份蛇種之分布亦與人為活動有關。結果亦顯示21種蛇類模式之預測準確度能達到預期之水準 (rs ≥ 0.8)，而兩種蛇種（白腹游蛇與水蛇）則受限於生物特性而使準確度偏低 (rs ≤ 0.5)。此外，蛇類種豐度隨海拔升高而降低，此現象遵循Rapoport-rescue hypothesis。中高海拔蛇種與特有種之預測熱點分布大致相似，均集中於海拔1,500-2,000 m，低海拔蛇種之熱點則集中於山區與平地交會處，而保育類蛇種之熱點在名錄修正前後呈現不同的分布樣式。本研究顯示對台灣蛇類保育而言，山區邊緣比高山地區更具急迫性。

Understanding the geographical range of species distribution and the relationship between species and environment is very important. Due to habitat loss and human hunting, the abundance of snakes, which are vulnerable to extinction, is dramatically decreasing. To understand the habitat preferences, distribution range, and conservation status of terrestrial snakes in Taiwan, I applied Ecological-Niche Factor Analysis (ENFA) to predict the spatial distribution of 37 species of snakes (82.2% of total species). A total of 8,866 presence records of snakes were gathered, and these records covered 2,360 grids, about 6.4% of total grids. In general, the results of ENFA indicated that the habitat preferences of different species were inconsistent, and the distribution was constrained mainly by elevation, southness, annual mean temperature, and coefficient of variation of 12 month’s mean temperature. Some species were also relative to human activities. Twenty-one species had higher predictive accuracy (rs ≥ 0.8), while two species (Sinonatrix percarinata suriki and Enhydris plumbea) had lower predictive accuracy (rs ≤ 0.5) due to their biological traits. In addition, snake species richness decreased with increasing elevation which followed the Rapoport-rescue hypothesis. Both the predicted hotspots of mid- and high-elevation species and those of endemic species concentrated between 1,500-2,000 m asl, and those of low-elevation species were between mountains and lowlands. The distribution pattern of predicted hotspots of protected species was different with that of species listed in the new revision of protected species. To conserve snake species in Taiwan, I suggested that the edges of mountains are more urgent than alps.