Margreiter Vera, Porro Francesco, Mondoni Andrea, Erschbamer Brigitta
Department of Botany, University of Innsbruck, Innsbruck, Austria.
Department of Earth and Environmental Science, University of Pavia, Pavia, Italy.
Front Plant Sci. 2022 May 13;13:827330. doi: 10.3389/fpls.2022.827330. eCollection 2022.
The reasons why some species occur widespread, while related species have restricted geographical ranges have been attributed to habitat specialization or ecological niche breadth. For species in the genus , habitat specialization alone cannot explain the distributional differences observed. We hypothesize that recruitment traits (i.e., germination, emergence, and survival) may account for differences in geographical ranges and that early life stages correlate to survival. We studied recruitment responses in 13 widespread and 12 narrow-ranged species in the laboratory and common garden experiments using seeds collected from 79 populations in the European Alps. We found that in the laboratory cold temperature led to higher germination percentages compared with warm temperature for both distribution groups. This represents an exception to the general assumption that alpine species require warm cues for germination. In warm laboratory temperatures, widespread species germinated better than narrow-ranged species, indicating a greater tolerance of warm temperatures for the former. Subsequent to germination, recruitment traits between the two distribution groups were lower or null in the common garden, suggesting that the impact of recruitment on species' geographical ranges occurs at the earliest life stage. Mean time to emergence of narrow-ranged species showed lower variability than that of widespread species. Consistently, intraspecific variation of mean annual temperatures between seed collection sites was lower for narrow-ranged species, indicating a close relationship between home sites and emergence time. Emergence percentage was a strong predictor of survival only for widespread species, underlining that seed and seedling functional traits differ between distribution groups, which require further research. Our results support the view that early life stages are critical to population dynamics and thus can influence species' geographical ranges. The wider responses to climatic conditions in widespread species may have facilitated their spread across the Alps. Our results also suggest that all species face a considerable threat from climate warming due to their overall cold-adapted recruitment niche.
一些物种分布广泛，而相关物种的地理分布范围却有限，其原因被归结为栖息地特化或生态位宽度。对于该属中的物种，仅栖息地特化无法解释所观察到的分布差异。我们推测，补充特征（即发芽、出土和存活）可能是地理分布范围差异的原因，并且早期生命阶段与存活率相关。我们在实验室和普通花园实验中，使用从欧洲阿尔卑斯山79个种群收集的种子，研究了13种广布种和12种狭域种的补充反应。我们发现，在实验室中，对于两个分布组而言，与温暖温度相比，低温导致更高的发芽率。这是对高山物种发芽需要温暖信号这一普遍假设的一个例外。在温暖的实验室温度下，广布种比狭域种发芽更好，表明前者对温暖温度具有更大的耐受性。发芽后，在普通花园中，两个分布组之间的补充特征较低或不存在，这表明补充对物种地理分布范围的影响发生在最早的生命阶段。狭域种的平均出土时间变异性低于广布种。同样，狭域种种子收集地点之间的年平均温度种内变异性较低，表明原生地与出土时间之间存在密切关系。出土率仅是广布种存活率的一个强预测指标，这突出了分布组之间种子和幼苗功能特征的差异，这需要进一步研究。我们的结果支持这样一种观点，即早期生命阶段对种群动态至关重要，因此可以影响物种的地理分布范围。广布种对气候条件的更广泛反应可能促进了它们在阿尔卑斯山的扩散。我们的结果还表明，由于其整体适应寒冷的补充生态位，所有物种都面临着来自气候变暖的相当大的威胁。
