合歡山亞熱帶高山草原花期重疊植物之繁殖策略與傳粉效率

Abstract

了解影響植物繁殖成功的因素，對於預測高山生態系在環境變遷下的韌性至關重要。本研究以臺灣合歡山亞熱帶高山草原中的27種共花期高山植物為對象，探討其繁殖策略與授粉效率。田間進行異交（outcrossing）、自然授粉（natural pollination）、補充授粉（supplemental pollination）、同株異花授粉（geitonogamous pollination）及自花授粉（autogamous pollination）等控制授粉實驗，以評估植物的交配系統、量化花粉限制與傳粉者貢獻，並比較不同授粉處理間的結實率。此外，亦於實驗室進行種子萌發試驗，以評估授粉後的繁殖表現。研究結果顯示，以異交為主的植物所占比例最高（40.7%），其次為混合交配型（37.0%），而以自交為主者占22.2%，顯示此高山植物群落具有多樣化的繁殖策略。不同物種對授粉處理的結實率反應亦有明顯差異；補充授粉與自然授粉經常產生較高的結實率，但沒有任何單一授粉處理能在所有物種中一致地產生最高的繁殖產出。花粉限制整體偏低，但不同物種間仍存在差異（PLI = −0.08–0.47），其中81.5%的研究物種之PLI值低於0.20。傳粉者貢獻亦呈現明顯的物種間差異（PCI = 0.17–1.00），其中70.4%的物種之PCI值高於0.50。自交親和性與傳粉者貢獻呈高度顯著負相關（Spearman’s ρ = −0.94，p < 0.001），但與花粉限制之間無顯著相關（ρ = −0.16，p = 0.425）。此結果顯示，較高的自主自交能力與較低的相對傳粉者貢獻有關，但無法一致地預測植物所受到的花粉限制程度。不同物種的最終萌發率亦有所差異，但多數物種在90天內達到中等至高程度的萌發。依據累積萌發動態，可將物種分為快速、中等及緩慢萌發型，代表物種分別為 G. scabrida 與 G. arisanensis、A. formosana 與 S. nemorensis var. dentatus，以及 R. junipericola 與 P. palustris。綜合而言，合歡山高山植物群落呈現多樣化的繁殖策略，而自交親和性、花粉供應、傳粉者貢獻及種子萌發在塑造植物繁殖成功方面扮演不同但相互關聯的角色。

Understanding the factors shaping plant reproductive success is essential for predicting the resilience of alpine ecosystems under changing environmental conditions. This study evaluated reproductive strategies and pollination efficiency of 27 co-flowering alpine plants in the subtropical meadows of Hehuanshan, Taiwan. Controlled pollination experiments, including outcrossing, natural, supplemental, geitonogamous, and autogamous pollination, were conducted in the field to characterize mating systems, quantify pollen limitation and pollinator contribution, and compare seed set among treatments. Seed germination experiments were also conducted under lab conditions to assess post-pollination reproductive performance. Predominantly outcrossing plants represented the largest group (40.7%), closely followed by mixed-mating plants (37.0%), while predominantly selfing plants accounted for 22.2%, revealing considerable diversity in reproductive strategies across the community. Seed-set responses also varied markedly among taxa, with supplemental and natural pollination frequently producing high seed set and no single pollination treatment consistently maximizing reproductive output across all plants. Pollen limitation was generally low but varied among taxa (PLI = −0.08 to 0.47), with 81.5% of the studied species having PLI values below 0.20. Pollinator contribution also varied considerably (PCI = 0.17–1.00), with 70.4% of species showing PCI values above 0.50. Self-compatibility was strongly and negatively associated with pollinator contribution (Spearman’s ρ = −0.94, p < 0.001), but showed no significant relationship with pollen limitation (ρ = −0.16, p = 0.425). Thus, greater autonomous selfing capacity was associated with reduced relative pollinator contribution but did not consistently predict the extent of pollen limitation. Final germination percentage varied among species, although most achieved intermediate to high germination within 90 days. Based on cumulative germination dynamics, species were classified as fast, intermediate, or slow germinators, represented respectively by G. scabrida and G. arisanensis, A. formosana and S. nemorensis var. dentatus, and R. junipericola and P. palustris. Taken together, the Hehuanshan alpine plant meadow exhibits a mosaic of reproductive strategies, with contrasting roles of self-compatibility, pollen availability, pollinator contribution, and germination in shaping reproductive success.