據(jù)10月9日的《科學(xué)》（Science）雜志報(bào)道說,，在熱帶地區(qū)，許多物種如果缺乏一個(gè)可以遷往的較為涼爽的地方的話,，它們不久將面臨因?yàn)槿驓夂虻淖兣霈F(xiàn)種群數(shù)的下降及滅絕的局面,。這些地球上的熱帶地區(qū)對物種來說是一種獨(dú)特的挑戰(zhàn)，因?yàn)榫暥确较虻倪w徙（向東或向西）并不能夠給它們提供足夠的救助,。這些物種必須將其活動(dòng)范圍向高處遷移才能夠躲避暑熱,。
Robert Colwell及其同事分析了熱帶的植物、昆蟲和真菌等1902個(gè)物種的數(shù)據(jù)并得出結(jié)論：低地的物種種群數(shù)不久即會(huì)出現(xiàn)生物多元性和物種豐富程度的下降,，這是因?yàn)檫€沒有什么已經(jīng)適應(yīng)了較高溫度的物種源可以取代那些因氣溫變暖而被驅(qū)往更高海拔的物種,。在此期間,，研究人員提出，較高海拔的物種當(dāng)面臨向更高海拔攀登的空間已不復(fù)存在的時(shí)候,，它們將會(huì)同時(shí)面臨“山頂滅絕”的處境,。 此外，一項(xiàng)新的調(diào)查顯示,，在美國Yosemite國家公園內(nèi)的小型哺乳動(dòng)物在經(jīng)過氣溫變暖的一個(gè)世紀(jì)之后,，其活動(dòng)范圍發(fā)生了重大的改變。某些生活在高海拔地區(qū)的哺乳動(dòng)物如高山金花鼠的活動(dòng)范圍已經(jīng)縮小,，而生活在低海拔地區(qū)的動(dòng)物如巢鼠則已經(jīng)將其活動(dòng)范圍擴(kuò)大到了較高的海拔地區(qū),。
Craig Moritz及其同事說，氣候變暖也攪亂了其它生活在中等海拔和高海拔地區(qū)的哺乳動(dòng)物群落,。為了證明這些變化,，研究人員將他們的調(diào)查數(shù)據(jù)與在20世紀(jì)初由Joseph Grinnell收集的Yosemite大量的數(shù)據(jù)組進(jìn)行了比較。Joseph Grinnell是一位田野生物學(xué)家,，他的工作導(dǎo)致了“生態(tài)位”概念的問世,。盡管物種的活動(dòng)范圍出現(xiàn)了顯著的波動(dòng)，Yosemite在過去的100年中一直維持著小型哺乳動(dòng)物物種的多樣性,。Moritz及其同事提出,，受到公園保護(hù)的廣大地區(qū)可能因?yàn)樵试S哺乳動(dòng)物隨著氣候的變化而遷往新的海拔高度從而保持了這些動(dòng)物的多樣性。在一篇Perspective中,，Jens-Christian Svenning更為詳細(xì)地解釋了這些發(fā)現(xiàn)。（生物谷Bioon.com）
生物谷推薦原始出處：
Science,，Vol. 322. no. 5899, pp. 258 - 261,，Robert K. Colwell，John T. Longino
Global Warming, Elevational Range Shifts, and Lowland Biotic Attrition in the Wet Tropics
Robert K. Colwell,1* Gunnar Brehm,2 Catherine L. Cardelús,3 Alex C. Gilman,4 John T. Longino5
Many studies suggest that global warming is driving species ranges poleward and toward higher elevations at temperate latitudes, but evidence for range shifts is scarce for the tropics, where the shallow latitudinal temperature gradient makes upslope shifts more likely than poleward shifts. Based on new data for plants and insects on an elevational transect in Costa Rica, we assess the potential for lowland biotic attrition, range-shift gaps, and mountaintop extinctions under projected warming. We conclude that tropical lowland biotas may face a level of net lowland biotic attrition without parallel at higher latitudes (where range shifts may be compensated for by species from lower latitudes) and that a high proportion of tropical species soon faces gaps between current and projected elevational ranges.
Science,，Vol. 322. no. 5899, pp. 261 - 264,，Craig Moritz，Steven R. Beissinger
Impact of a Century of Climate Change on Small-Mammal Communities in Yosemite National Park, USA
Craig Moritz,1,2* James L. Patton,1,2 Chris J. Conroy,1 Juan L. Parra,1,2 Gary C. White,3 Steven R. Beissinger1,4
We provide a century-scale view of small-mammal responses to global warming, without confounding effects of land-use change, by repeating Grinnell's early–20th century survey across a 3000-meter-elevation gradient that spans Yosemite National Park, California, USA. Using occupancy modeling to control for variation in detectability, we show substantial (500 meters on average) upward changes in elevational limits for half of 28 species monitored, consistent with the observed 3°C increase in minimum temperatures. Formerly low-elevation species expanded their ranges and high-elevation species contracted theirs, leading to changed community composition at mid- and high elevations. Elevational replacement among congeners changed because species' responses were idiosyncratic. Though some high-elevation species are threatened, protection of elevation gradients allows other species to respond via migration.
