臺灣藜蘆屬植物系統分類學及生殖生物學研究

Abstract

藜蘆屬植物（Veratrum L.）隸屬黑葯花科 （Melanthiaceae），全球約有 25 個被接受的物種，主要分布於北溫帶地區。本屬在臺灣有兩種，臺灣藜蘆(Veratrum formosanum O.Loes.)與雪山藜蘆（V. shuehshanarum S.S.Ying），皆為臺灣特有種。花色與葉寬為主要區辨特徵。然而，由於形態特徵不明確與系統演化關係未解，兩者的分類地位仍具爭議。尤其我們觀察到花色連續變異的中間型，顯示需要更全面的分類重新評估。本研究根據分布海拔，可將藜蘆族群大致分為低海拔（800–1100 公尺）與高海拔（2200–3600 公尺）兩群，並進行野外採樣，包括以往未調查到的區域的三種形態植株。除了量測形態及檢視植物標本館標本外，並以核酸內轉錄間隔區(internal transcribed spacer, ITS)序列及葉綠體基因片段atpB-rbcL intergenic spacer，重建其親緣關係樹，更建立此兩種葉綠體全基因組與屬下近緣種比較。結果顯示，在形態測量結果顯示，三種形態上的葉形、葉長寬、基部網狀纖維、花細部構造之特徵與花粉構造高度重疊；分子親緣分析（nrITS 和 葉綠體片段 atpB–rbcL ）與前人研究一致，呈現低解析度，無法有效分辨三種形態間的親緣關係。為提升解析度，研究進一步建構葉綠體全基因組。結果顯示僅在 rpoC1 intron 中存在單一核苷酸差異，顯示基因組間極低分化。因此綜合形態與譜系分析結果，本研究建議雪山藜蘆併入到臺灣藜蘆的同物異名。此外，本研究建立了生活史及部分生殖生物學。觀察發現，臺灣藜蘆主要的訪花昆蟲為雙翅目，特別是蠅類，顯示其紫色花與特殊氣味可能為傳粉適應。中間型與雪山藜蘆族群則未觀察到傳粉者。花粉產量與花粉/胚珠比（P/O）顯示，低海拔族群有較高的產粉量與 P/O 比，反映出可能對異花授粉依賴增加，以及其生殖限制。這些物候資料能透過長期追蹤作為國家公園族群保育政策及未來氣候變遷追蹤的指標之一。

Veratrum (Melanthiaceae) are perennial plants, with around 25 accepted species predominantly distributed in the Northern Temperate regions. Two species are currently recognised in Taiwan, Veratrum formosanum O.Loes. and V. shuehshanarum S.S.Ying, distinguished by their floral color and leaf shape (two morphotypes). However, the taxonomy of Veratrum species in Taiwan has remained contentious due to unclear morphological distinction and unresolved phylogenetic relationships. In particular, a series of intermediate types can be observed across different elevations, presenting a complex pattern of variation that calls for a more integrative taxonomic reassessment. In this study, we conducted field sampling across a range of elevations, including sites that had not previously been examined, to investigate the morphological, molecular, and reproductive characteristics of the two morphotypes and their intermediates of Veratrum in Taiwan. The populations of Veratrum spp. in Taiwan can be categorized into low (800-1100 m) and high (2200-3600 m) elevation groups based on the localities. Results from morphological measurements revealed considerable overlap in leaf and floral traits between low- and high-altitude populations, for both morphotypes. Phylogenetic analyses were performed using nuclear ITS and chloroplast atpB–rbcL regions, and the results are consistent with previous studies, but showed low resolution among the two morphotypes and their intermediates. To improve phylogenetic resolution, we reconstructed complete chloroplast genomes from one individual each of V. formosanum and V. shuehshanarum collected at high elevations. The two genomes differed by only a single base substitution, located in the rpoC1 intron, indicating extremely low divergence in their plastomes. Therefore, based on the combined evidence from both morphological characteristics and phylogenetic analyses, we propose that V. shuehshanarum should be treated as a taxonomic synonym of V. formosanum. We also conducted reproductive biology comparisons and life cycle assessments for Veratrum in Taiwan. Floral visitors to V. formosanum were predominantly Diptera spp., especially flies for populations in both low- and high-altitude areas, which are likely attracted by the plant’s distinctive purple flowers and decaying odor. These floral traits suggest a sapromyiophilous pollination syndrome. No pollinators were recorded on intermediate type or V. shuehshanarum populations for the flowering individuals observed. Comparisons of pollen production and pollen-ovule (P/O) ratios showed that low-altitude populations produce more pollen and have higher P/O ratios than high-altitude populations for both morphotypes, suggesting a shift toward greater reliance on out crossing and the potential presence of reproductive constraints. These phenological data can serve as indicators for conservation strategies in national parks and for monitoring future climate change impacts.