Many ecosystems today are threatened by invasive species. These newcomers prey on or compete with native species, they carry new parasites and diseases, and even cause extinctions of long-established residents. But why are some species such successful invaders while the advances of other species in foreign territory remain unrecognized?
要回答这个问题，我们专注于侵入性物种最普遍的例子之一：老鼠。这些啮齿动物几乎在地球上到处都是发现对本地生态社区的不利影响，特别是在岛上。作为他博士学论文的一部分，来自安塔那利多大学的Toky Randriamoria在马达加斯加中部捕获了小哺乳动物。老鼠是他主要在他的陷阱中发现的农业领域，靠近村庄，以及天然森林。最初由来自中世纪的阿拉伯半岛的海运会引入，黑人和挪威大鼠已经过度运行马达加斯加。今天，它们在岛上的几乎所有自然和人为栖息地都发生，在某些地区代表了> 95％的啮齿动物捕获。
Toky collected nearly 600 hair samples of black and Norway rats, which I used to encipher the diet and habitat use of these individuals by stable isotope analysis. Stable isotopes are “one of nature’s ecological recorders” and integrate information on what and where an individual fed during the period of hair growth. We found that rats mixed animal and plant matter and had an extremely broad dietary niche. Indeed, rats covered a dietary niche that was larger than a whole community of around 20 native species! Moreover, rats were opportunistic foragers and changed their diet according to what was available.
But we learnt even more from stable isotope analysis: the signature of some individuals did not match to their habitat. This can only mean that certain individuals move between agricultural fields near villages and natural forests; and with them their parasites and diseases.
Thus overall, our results suggest that due to their flexible and generalist diet and potential movement between natural forest and anthropogenic habitats, rats might affect native forest-dependent Malagasy rodents as competitors, predators, and disease vectors. The combination of these effects helps explain the invasion success of rats and the detrimental effects of this genus on the endemic fauna.
To learn more about the research of Melanie and her co-authors, please explore these links:
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