動物的物種起源常常與地理障礙有關(guān),，比如山水等地理分布隔開了物種，也造成了生殖隔離,。日前，美國密蘇里大學(xué)的研究人員研究發(fā)現(xiàn)僅染色體的數(shù)量就可以控制物種隔離,，相關(guān)論文發(fā)表在Proceedings of the Royal Society B:Biological Sciences。
MU文學(xué)院生物科學(xué)系主任Carl Gerhardt教授和博士生Mitch Tucker研究了兩種生活在密蘇里關(guān)系緊密的灰色樹蛙物種,，東部灰樹蛙和科普灰樹蛙。
Gerhardt說不管對人類還是樹蛙,，用肉眼來看這兩種樹蛙長的很相似。唯一不同的就是染色體的數(shù)量,，東部灰樹蛙有兩倍數(shù)量的染色體,。
為了吸引伴侶,，這兩個物種在它們叫聲表現(xiàn)方面有所區(qū)別,。雄性青蛙都唱同樣的“情歌”——只是一只樹蛙唱的慢一點,。
研究人員在早前的研究發(fā)現(xiàn)樹蛙染色體數(shù)越多,，細胞越大,，這就降低了顫音的頻率。雌性樹蛙對雄性叫聲的選擇是否同樣與染色體數(shù)有關(guān)尚不清楚,。
為解決這個疑惑，Tucker通過模擬樹蛙發(fā)育早期的春季溫度,，模擬了樹蛙染色體復(fù)制的過程,。雌性樹蛙發(fā)育成熟后，向這些雌蛙播放電腦合成的不同顫音頻率的雄性樹蛙的叫聲,。研究人員發(fā)現(xiàn)雌蛙蹦向染色體相匹配的雄性樹蛙,，這也表明了雌性樹蛙的偏好。
Gerhardt說這就表明了僅染色體的數(shù)量就可以控制物種隔離,。隨著染色體數(shù)量增加,，細胞大小也改變了，而這可能是叫聲和選擇變化的直接原因,。
據(jù)Gerhardt說,，東部灰樹蛙可能是因染色體復(fù)制,、行為變化和生殖隔離而導(dǎo)致快速進化的罕見案例。（生物谷Bioon.com）
doi:10.1098/rspb.2011.1968
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PMID:
Parallel changes in mate-attracting calls and female preferences in autotriploid tree frogs
Tucker MA, Gerhardt HC.
For polyploid species to persist, they must be reproductively isolated from their diploid parental species, which coexist at the same time and place at least initially. In a complex of biparentally reproducing tetraploid and diploid tree frogs in North America, selective phonotaxis-mediated by differences in the pulse-repetition (pulse rate) of their mate-attracting vocalizations-ensures assortative mating. We show that artificially produced autotriploid females of the diploid species (Hyla chrysoscelis) show a shift in pulse-rate preference in the direction of the pulse rate produced by males of the tetraploid species (Hyla versicolor). The estimated preference function is centred near the mean pulse rate of the calls of artificially produced male autotriploids. Such a parallel shift, which is caused by polyploidy per se and whose magnitude is expected to be greater in autotetraploids, may have facilitated sympatric speciation by promoting reproductive isolation of the initially formed polyploids from their diploid parental forms. This process also helps to explain why tetraploid lineages with different origins have similar advertisement calls and freely interbreed.
