都市化对南加州溪流两栖类与外来种生物分布与丰度之影

1、國立台灣大學生態學與演化生物學研究所碩、博士專題討論摘要 日期：2005年12月23日題目：都市化對南加州溪流兩棲類與外來種生物分佈與豐度之影響Effects of Urbanization on the Distribution and Abundance of Amphibians and Invasive Species in Southern California Streams.作者：Seth P. D. Riley; Gary T. Busteed; Lee B. Kats; Thomas L. Vandergon; Lena F. S. Lee; Rosi G. Dagit; J

2、acob L. Kerby; Robert N. Fisher; Raymond M. Sauvajot出處：Conservation Biology, Dec. 2005, Vol. 19(6): 1894-1907講者：李承恩摘要：都市化（urbanization）對生態系造成許多方面的負面的影響，其中也包括淡水生態系；它亦被視為兩棲類族群驟降的主因之一。本文研究團對於2000 - 2002年間，針對南加州35條都市化的溪流，進行原生兩棲類與外來種生物的分佈與豐度、溪流棲地特徵及水棲昆蟲相的調查。他們測量樣站所屬集水區（watershed）內都市土地利用面積的百分比，來做為都市化的指標。在

3、高都市化的溪流內普遍存在外來種螯蝦（Procambarus clarkii）及魚類，而原生的兩棲類也較少，如：加州蠑螈（Taricha torosa）與加州樹蟾（Hyla cadaverina）。結果指出超過8的都市化似乎會造成此影響，且與其他研究推論的10 15相近。雖然還沒發現直接的證據來說明，但以分佈最廣的太平洋樹蟾（H. regilla）為例，在有外來種生物存在的地方，其族群量確實較低。而在都市化溪流的水棲昆蟲相，其多樣性亦偏低，特別是一些敏感性的水棲昆蟲更加明顯。都市化溪流中動物群聚的改變，大致亦與其棲地的物理特徵有關，如較少的深潭（pool）、較多的深流（run）、增加水深與流量，

4、如此亦可增加溪流的續流性（permanent）。而溪流的續流性也在2002年得到驗證，該年許多天然溪流都呈乾涸狀態，相對地都市化溪流則不改變。都市化明顯地改變這個區域的溪流棲地，且提高外來種入侵之之可能性，進而對原生兩棲類分佈與豐度造成負面的影響。參考文獻：Paul, M. J., and J. L. Meyer. 2001. Streams in the urban landscape. Annual Review of Ecology and Systematics 32: 333365.Willson, J. D., and M. E. Dorcas. 2003. Effects of

5、habitat disturbance on stream salamanders: implications for buffer zones and watershed management. Conservation Biology 17: 763771.Topic:Effects of Urbanization on the Distribution and Abundance of Amphibians and Invasive Species in Southern California Streams.Authors:Seth P. D. Riley; Gary T. Buste

6、ed; Lee B. Kats; Thomas L. Vandergon; Lena F. S. Lee; Rosi G. Dagit; Jacob L. Kerby; Robert N. Fisher; Raymond M. SauvajotJournal:Conservation Biology, Dec. 2005, Vol. 19(6): 1894-1907Speaker:Cheng-En LiAbstract:Urbanization negatively affects natural ecosystems, and aquatic systems in particular. U

7、rbanization is also cited as one of the potential contributors to declines in amphibian populations. From 2000 to 2002 the authors determined the distribution and abundance of native amphibians and exotic predators and characterized stream habitat and invertebrate communities in 35 streams in an urb

8、anized landscape of Southern California. They measured the percentage of area within each watershed occupied by urban land uses as watershed development. In more developed watersheds, streams often had exotic crayfish (Procambarus clarkii) and fish, and had fewer California newts (Taricha torosa) an

9、d California treefrogs (Hyla cadaverina), both native species. These effects seemed particularly evident above 8% development and conformed with other urban stream studies that show negative impacts beginning at 1015% urbanization. For the most widespread native amphibian, Pacific treefrogs (H. regi

10、lla), abundance was lower in the presence of exotic crayfish, although direct urbanization effects were not found. Macroinvertebrate communities were also less diverse in urban streams, especially for sensitive species such as EPT. Fauna changes in urban streams may be related to changes in physical

11、 stream habitat, such as fewer pool and more run habitats and increased water depth and flow. These characteristics led to more permanent streams. Variation in stream permanence was particularly evident in 2002, when many natural streams were dry but urban streams were relatively unchanged. Urbanization has significantly altered stream habitat in this region and may enhance invasion by exotic species and negatively affect distribution and abundance of native amphibians.Reference:Paul, M. J., and J. L. Meyer. 2001. Streams in the urban landscape. Annual Review of Ecology and Systematics 32: