埋葬蟲近紅外線感知行為演化之生態因子

地球上多樣的光環境所施加的選汰壓力，塑造了生物視覺的演化。然而，我們對於生態因子與物理環境如何共同塑造長波光感知，目前仍然所知有限。森林落葉層的光環境有相當豐富的長波光 (> 700 nm)，這個波段的光線因為其低能量的性質，通常被認為無法透過視覺感光來接收。在本篇研究中，我們發現了目前為止陸域生態系的動物之中，光感知可見光波長(850-1050 nm) 最長的動物尼泊爾埋葬蟲 (Nicrophorus nepalensis)，並探討了塑造該特殊視覺的生態因子及其演化意義。 (一)、野外實驗證實，森林落葉層對於埋葬蟲而言，是一個種間競爭壓力小的環境，埋葬蟲因而不需要投資在耗能的埋葬行為上；相較之下，森林無落葉的地面則有相當激烈的種間競爭，埋葬蟲幾乎無法在沒有落葉的環境成功繁殖。（二）、室內的行為操作實驗，透過調整不同波長與強度的光線環境，進一步證實埋葬行為會受近紅外線調控，且預期的行為反應（不埋但仍有加工屍體）隨著波長增加而越明顯，在近紅外光的波長反應最明顯。此外，行為與外部形態的證據皆排除埋葬蟲使用熱感知的可能性，因而支持埋葬蟲使用光感知來偵測近紅外光。（三）、比較基因體的分析結果顯示，斑紋埋葬蟲屬有三種視蛋白：昆蟲紫外線視蛋白、昆蟲長波視蛋白、與rhodopsin7-like視蛋白，其中rh7-like視蛋白可能在近紅外線感知中扮演重要角色。綜合上述證據，我的研究指出，物理環境中豐富的長波光以及激烈的種間競爭壓力，此二生態因子共同塑造了埋葬蟲近紅外線感知的演化。

關鍵字

近紅外線感知；種間競爭；視覺適應；埋葬蟲

並列摘要

The remarkably varied light environments in ecosystems on Earth presents strong selective pressures on the evolution of visual systems. Physical limitations imposed on vision by a given light environment constraint the possibility of visual adaptations. However, we still have limited understandings on the interactions of ecological drivers and physical limitation in shaping the visual adaptation in forests—the largest terrestrial ecosystem. Forest detritus possesses markedly abundant long-wavelength light (> 700 nm), which has been conventionally considered imperceptible by animals. Here, we discover the longest visible wavelength (850-1050 nm) of photoreception known in terrestrial ecosystems and investigate the ecological drivers of this unusual visual adaption in forest-dwelling burying beetles (Nicrophorus nepalensis). Our field experiments reveal that forest detritus is a safe location with low interspecific competition and thus a location where beetles do not need to invest in costly carcass burial. We experimentally manipulate the light environments and demonstrate that burying behavior is mediated by the long-wavelength light (> 700 nm) cue through photoreception, rather than thermoreception. Our comparative genomic survey also identifies three opsin genes, an insect ultraviolet (UV) opsin, long-wavelength (LW) opsin, and a Drosophila rhodopsin7-like opsin, as candidates for the NIR photoreceptor. Together, our results identify interspecific competitive pressure as the crucial ecological driver for the only known visual system that can detect long-wavelength light under nature condition.

並列關鍵字

near infrared photoreception ； interspecific competition ； visual adaptation ； burying beetles

參考文獻

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埋葬蟲近紅外線感知行為演化之生態因子

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