近日，從中科院昆明植物所獲悉,，該所孫航研究組在中國西南“生物地理線”,，即田中—楷永線的研究上取得新突破，證實氣候因子改變導(dǎo)致田中—楷永線兩側(cè)植物區(qū)系分異,。相關(guān)成果發(fā)表在《分子生態(tài)學(xué)》雜志上,。
據(jù)了解，田中—楷永線位于我國西南部,，是東亞植物區(qū)系中中國—喜馬拉雅和中國—日本區(qū)系一條最重要的生物地理分界線,。由于地質(zhì)歷史和氣候等因素，致使分界線東,、西兩側(cè)區(qū)域植物區(qū)系的分異,。通常認為，田中—楷永線以西的植物區(qū)系較年輕,，有較多的新特有類群,；而田中—楷永線以東的植物區(qū)系較為古老，并富有古特有或孓遺的類群,。但目前尚不清楚田中—楷永線在促使種群譜系地理結(jié)構(gòu)分化方面的重要性,。
為此，孫航研究組利用葉綠體基因和核基因片段,，對河谷優(yōu)勢,、耐旱的灌木——苦刺花進行了遺傳結(jié)構(gòu)和譜系地理分析，重建了其種群分布和分化歷史,。結(jié)果表明,，苦刺花種群在田中—楷永線兩側(cè)有顯著的譜系地理分化，其分化時間大約在1.28個百萬年，這個時間明顯晚于喜馬拉雅的最后一次抬升,。
研究證明,，導(dǎo)致田中—楷永線兩側(cè)植物區(qū)系分異是氣候因子改變，如季風(fēng)氣候體系引起環(huán)境梯度變化,，特別是最后一次冰期溫度和植被類型的改變所致,。
通過進一步分析，科研人員還發(fā)現(xiàn),，與田中—楷永線東側(cè)的苦刺花種群相比,，西側(cè)種群長期以來較穩(wěn)定，并存在多個避難所,，特別是在橫斷山河谷,。而東側(cè)的種群受最后一次冰期影響，分化出了不同的區(qū)域譜系地理結(jié)構(gòu),。
同時,，核基因研究還表明田中—楷永線東部的居群可能來源于恰好位于該線以東的金沙江下游種群，從而驗證了許多類群“冰期走出橫斷山”的假說,，并不支持傳統(tǒng)上認為田中—楷永線是一條古老的生物地理分界線的觀點,。（生物谷 Bioon.com）
生物谷推薦的英文摘要
Mol Ecol. doi: 10.1111/mec.12388
Phylogeography of Sophora davidii (Leguminosae) across the ‘Tanaka-Kaiyong Line’, an important phytogeographic boundary in Southwest China
Fan DM, Yue JP, Nie ZL, Li ZM, Comes HP, Sun H.
The 'Tanaka-Kaiyong Line' (TKL) is a major phytogeographic boundary in Southwest China, separating East Asia's Sino-Himalayan and Sino-Japanese Floras. However, little is known about the importance of this boundary in promoting intraspecific phylogeographic subdivision and divergence. Using chloroplast (cpDNA) and nuclear-intron (nDNA) sequence data, we reconstructed the population history of Sophora davidii, a drought-tolerant riparian shrub widely distributed on either side of the TKL. Specifically, we aimed at testing two long-standing explanations for possible vicariant events across the TKL: (i) Late Pliocene (c. 3 Ma) geological uplift of the eastern Qinghai-Tibetan Plateau (QTP) or (ii) a sharp environmental gradient associated with the establishment of different monsoon regimes on either side of the TKL during the (Late) Pleistocene. Our genealogical analyses detected a major west-east split in cpDNA, geographically largely consistent with the TKL, and dated to c. 1.28 Ma (95% HPD: 0.21-2.96 Ma), hence postdating the latest phase of eastern QTP uplift. Furthermore, integrating cpDNA phylogeographic patterns with mismatch analyses, we found multiple refugial isolation and long-term demographic stability of populations in the west (Hengduan Mountain Range) compared with extensive range expansions in the east, possibly during the last glacial period(s) and followed by differentiation into regional sublineages (southeast: Yunnan-Guizhou Plateau vs. northeast: Qinling Mts./Loess Plateau). Although nuclear differentiation was less marked, the geographical pattern of nDNA haplotypes provided some further indication of the species' eastward expansion, possibly from source populations located just east of the TKL (lower Jinshajiang region). Overall, the present data reject the geological (tectonic) explanation for the TKL and, instead, provide supportive evidence for its role as a climatically driven barrier to present-day plant dispersal. In addition, our study highlights changing temperatures and vegetation types during the last glacial period(s), along with aspects of regional topography, to be important determinants of the glacial eastward expansion of S. davidii. In consequence, our study lends support to a 'glacial out-of-Hengduan Mts'. hypothesis for the xerophytic-riparian flora of Southwest China, which in turn is inconsistent with the traditional view of the TKL as a 'classical' vicariant-biogeographic boundary.
