尼泊爾埋葬蟲族群在兩島嶼上的溫度適應

Abstract

全球暖化對生物造成全面性的衝擊，生物如何適應不同的氣候差異，產生不同的溫度適應模式，是預測暖化如何影響生物續存的重要問題。過去探討生物如何適應不同的氣候主要有兩個假說：適應溫差的氣候變異度假說以及適應平均溫度的最佳溫度假說。生存及繁殖決定了生物的續存，但意義卻不相同，其適應模式也不可一概而論，而過去研究大多著重於生存方面的溫度適應，對於繁殖的溫度適應探討甚少，但繁殖才是生物終其一生的目標。我們以廣泛分布於亞洲的尼泊爾埋葬蟲為實驗物種，比較各溫度下不同族群繁殖表現的差異，以日本奄美族群及台灣合歡山族群進行比較，我們發現生存指標－溫度耐受度符合氣候變異度假說的預測，奄美族群耐受範圍大於合歡山族群。而繁殖方面兩族群對溫度的適應則是比較複雜，在繁殖成功率上兩族群並無顯著的不同，子代的品質也沒有顯著差異，但在埋葬行為方面合歡山族群成功埋葬屍體的比顯著高於奄美族群；而奄美族群雖然埋葬屍體的比例較低，但埋葬屍體後的繁殖成功率則顯著較高。且奄美族群成功埋葬屍體後產出的子代品質都高於合歡山族群，顯示兩族群有不同的繁殖策略。本研究結果顯示，溫度耐受度的適應比較簡單，溫度變異大的環境耐受度也要增加，符合氣候變異度假說的預測，而繁殖不同階段的適應明顯不同，表示繁殖是相對複雜的行為，從埋葬屍體到子代孵化，其中包含了不只一個行為表現，並且各自的適應模式並不相同，這說明了要充分了解氣候對生物適應的影響，除了生存以外也必須仔細考慮其他的生活史特徵與適應性成分。

Climate change has a wide range of influences on organisms. Understanding how organism adapt to thermal variation is critical to forecast the fate of species in the warming world. Most of the previous studies focused on species’ thermal tolerance, but not other important fitness components such as reproduction, varied across different thermal environments. Therefore, how the different fitness components were influenced by climate remains poorly understood. Here, we test two hypotheses about climate adaptation: climate variation hypothesis, and thermal optimum hypothesis, through investigating the thermal tolerance and breeding performance of two populations of burying beetles (Nicrophorus nepalensis Hope 1831) from different latitudes (Amami island: 28°15'12.7'N, and Mt. Hehuan: 24°10'48.2'N). We found that the range of thermal tolerance of the Amami population was broader than that of the Hehuan population, supporting the climate variation hypothesis. However, beetles from the Amami population had better breeding performance than those from the Hehuan population after successfully preparing their breeding resources (i.e. burying carcasses) in every tested temperature. On the other hand, beetles from the Hehuan population had better burying performance than those from Amami population especially in high temperature, and the two populations had no difference in finally fitness at every tested temperature. Our results showed that reproductive performance, which involved in multiple steps such as carcass burial, and larva hatching, is affected by more complicated mechanisms than that of adult physiological tolerance. Our findings also showed the necessity to comprehensively understand the adaptive models of different life history traits.