一只雄豪勛爵島竹節(jié)蟲(chóng)和一只雌豪勛爵島竹節(jié)蟲(chóng)(左),。 (圖片提供:Thomas Reischig)
豪勛爵島竹節(jié)蟲(chóng)(Dryococelus australis)和豪勛爵島到底誰(shuí)先出現(xiàn)在地球上,?你可能并不會(huì)提出這個(gè)關(guān)于古老的問(wèn)題,然而研究人員根據(jù)一份報(bào)告終于有了自己的答案:這種不能飛的昆蟲(chóng)顯然比它們的家——澳大利亞附近的豪勛爵島——還要古老,。這一發(fā)現(xiàn)證明,,這種昆蟲(chóng)最初起源于一座古老的海島,而后者如今已經(jīng)淹沒(méi)在太平洋中了,。
身長(zhǎng)達(dá)13公分的豪勛爵島竹節(jié)蟲(chóng)看起來(lái)就像一只蝗蟲(chóng)和一只螳螂的“混血兒”,。與竹節(jié)蟲(chóng)大家族中的其他成員不同,豪勛爵島竹節(jié)蟲(chóng)生有粗壯結(jié)實(shí)的體魄,,并且在地面上生活,。研究人員認(rèn)為,上世紀(jì)60年代,,當(dāng)黑鼠到達(dá)豪勛爵島后,,豪勛爵島竹節(jié)蟲(chóng)便滅絕了。然而2001年的新聞卻報(bào)道說(shuō),,研究人員在豪勛爵島附近的一個(gè)名為柏爾的金字塔的小島上發(fā)現(xiàn)了20到30只豪勛爵島竹節(jié)蟲(chóng)個(gè)體,,這讓它們成為了迄今為止全世界最稀有的一種昆蟲(chóng),。
然而有關(guān)豪勛爵島竹節(jié)蟲(chóng)棲息地的發(fā)現(xiàn)則更讓人感到驚訝,。作為對(duì)竹節(jié)蟲(chóng)進(jìn)化起源研究的一部分,新西蘭皇家科學(xué)院土地環(huán)境保護(hù)研究所生物學(xué)家Thomas Buckley和同事,,從3個(gè)竹節(jié)蟲(chóng)種群——包括豪勛爵島竹節(jié)蟲(chóng)以及70多只其他竹節(jié)蟲(chóng)——中采集了脫氧核糖核酸(DNA)樣本,。研究人員最終發(fā)現(xiàn),豪勛爵島竹節(jié)蟲(chóng)具有2000多萬(wàn)年的歷史,,這一年代比豪勛爵島上的巖石早了1300萬(wàn)年,。
那么這些昆蟲(chóng)到底是在哪里進(jìn)化的呢?Buckley認(rèn)為,,答案可能就在太平洋的海面下,。豪勛爵島是一條古老島鏈中最年輕的成員,,這條島鏈?zhǔn)怯《?mdash;澳大利亞構(gòu)造板塊向北行進(jìn)至一處火山中心時(shí)形成的。其中比較古老的島嶼已經(jīng)成為淹沒(méi)在海底的死火山,。豪勛爵島竹節(jié)蟲(chóng)很可能便是在這樣一座下沉的島嶼上進(jìn)化的,并且隨著自己的棲息地逐漸喪失而向南遷徙,。研究人員在12月16日的英國(guó)《皇家學(xué)會(huì)學(xué)報(bào)B》網(wǎng)絡(luò)版上報(bào)告了這一研究成果,。
DNA分析同時(shí)還揭示了其他一些意想不到的結(jié)果:這3種竹節(jié)蟲(chóng)種群的親緣關(guān)系并不近。這意味著它們類似的矮壯體型是為了適應(yīng)陸地上的生活而分別進(jìn)化的結(jié)果,,這一過(guò)程即人們所說(shuō)的趨同進(jìn)化,。(鳥(niǎo)和蝙蝠的翅膀便是趨同進(jìn)化的另一個(gè)例子,。)從事竹節(jié)蟲(chóng)研究的意大利波洛尼亞大學(xué)的進(jìn)化生物學(xué)家Marco Passamonti表示:“這項(xiàng)研究很新很有趣……它發(fā)現(xiàn)了一個(gè)不尋常的動(dòng)物體系中的趨同進(jìn)化現(xiàn)象,。”他說(shuō),,“這項(xiàng)研究對(duì)我的工作提供了非常好的支持。”(生物谷Bioon.com)
生物谷推薦原始出處:
Proceedings of the Royal Society B,,doi: 10.1098/rspb.2008.1552,Thomas R. Buckley,,Sven Bradler
Extreme convergence in stick insect evolution: phylogenetic placement of the Lord Howe Island tree lobster
Thomas R. Buckley1, Dilini Attanayake1, Sven Bradler2
1 Landcare Research, Private Bag 92170, Auckland 1142, New Zealand
2 Johann-Friedrich-Blumenbach-Institut für Zoologie und Anthropologie, Georg-August-Universit?t G?ttingen, Berliner Strasse 28, 37073 G?ttingen, Germany
The ‘tree lobsters’ are an enigmatic group of robust, ground-dwelling stick insects (order Phasmatodea) from the subfamily Eurycanthinae, distributed in New Guinea, New Caledonia and associated islands. Its most famous member is the Lord Howe Island stick insect Dryococelus australis (Montrouzier), which was believed to have become extinct but was rediscovered in 2001 and is considered to be one of the rarest insects in the world. To resolve the evolutionary position of Dryococelus, we constructed a phylogeny from approximately 2.4kb of mitochondrial and nuclear sequence data from representatives of all major phasmatodean lineages. Our data placed Dryococelus and the New Caledonian tree lobsters outside the New Guinean Eurycanthinae as members of an unrelated Australasian stick insect clade, the Lanceocercata. These results suggest a convergent origin of the ‘tree lobster’ body form. Our reanalysis of tree lobster characters provides additional support for our hypothesis of convergent evolution. We conclude that the phenotypic traits leading to the traditional classification are convergent adaptations to ground-living behaviour. Our molecular dating analyses indicate an ancient divergence (more than 22Myr ago) between Dryococelus and its Australian relatives. Hence, Dryococelus represents a long-standing separate evolutionary lineage within the stick insects and must be regarded as a key taxon to protect with respect to phasmatodean diversity.