評估棲地適合度能否作為族群豐度的指標－以臺灣山區四種囓齒目動物為例

Abstract

根據 Ideal free distribution (IFD) 理論，生物個體的分佈會反應棲地品質，棲地品質越高的地方、個體數量越高。生態棲位模擬利用物種出現點位以及相對應之環境條件，模擬物種實際生態棲位，再據此推估研究地區內每一地點的棲地適合度。棲地適合度可反應棲地品質，因此根據 IFD 之預測，棲地適合度越高的地點，可能有越高的族群數量。囓齒動物具短暫生活史，其族群數量往往能快速反應棲地品質，因而與棲地適合度可能存在正向關係。本研究利用最大熵演算法建立臺灣山區四種囓齒目動物 (臺灣森鼠 Apodemus semotus、高山白腹鼠 Niviventer culturatus、黑腹絨鼠 Eothenomys melanogaster、臺灣高山田鼠 Alexandromys kikuchii) 之生態棲位模型，並由文獻中彙整出各物種不同地點的捕捉率 (代表族群相對豐度)，以檢測生態棲位模型所建立的棲地適合度，是否能夠反應各物種之族群豐度。結果顯示，臺灣森鼠、黑腹絨鼠與臺灣高山田鼠的棲地適合度與族群相對豐度存在顯著正向關係。此外，黑腹絨鼠與臺灣高山田鼠在特定族群豐度情境下，能以棲地適合度對應族群豐度的趨勢變化。為了更周全地評估棲地適合度是否為值得信賴之族群豐度指標，未來應建立豐度資料的標準化方法。

The theory of ideal free distribution (IFD) predicts that organisms distribute themselves according to habitat quality thereby a higher number of individuals would be found in areas of higher habitat quality. Ecological niche modeling combines species occurrences with environmental conditions to establish a species’ realized niche, based on which habitat suitability of a given geographic extent can be projected. Such habitat suitability could potentially reflect habitat quality, and according to IFD, area with higher suitability are likely higher population abundance. Rodents have relatively short life history, and their population abundance often responds quickly to habitat quality. Consequently, rodent population abundance is likely to increase positively with habitat suitability. In this study, I used Maxent algorithm to build the ecological niche models for four rodent species (Apodemus semotus, Niviventer culturatus, Eothenomys melanogaster, Alexandromys kikuchii) in Taiwan’s montane region. Furthermore, I collected literature values of capture rate as an index of relative population abundance to examine whether habitat suitability from the ecological niche model can reflect population abundance of the rodents. I found positive relationships between habitat suitability and relative population abundance for A. semotus, E. melanogaster and A. kikuchii. Moreover, under certain scenarios of population abundance, such positive relationships also exist for E. melanogaster and A. kikuchii. To improve the evaluation of whether habitat suitability is an appropriate indicator of population abundance, I suggest that standardized abundance data should be established.