Barnes Paul W, Ryel Ronald J, Flint Stephan D
Department of Biological Sciences and Environment Program, Loyola University New Orleans, New OrleansLA, United States.
Department of Wildland Resources, Utah State University, LoganUT, United States.
Front Plant Sci. 2017 Aug 22;8:1451. doi: 10.3389/fpls.2017.01451. eCollection 2017.
Ongoing changes in Earth's climate are shifting the elevation ranges of many plant species with non-native species often experiencing greater expansion into higher elevations than native species. These climate change-induced shifts in distributions inevitably expose plants to novel biotic and abiotic environments, including altered solar ultraviolet (UV)-B (280-315 nm) radiation regimes. Do the greater migration potentials of non-native species into higher elevations imply that they have more effective UV-protective mechanisms than native species? In this study, we surveyed leaf epidermal UV-A transmittance (T) in a diversity of plant species representing different growth forms to test whether native and non-native species growing above 2800 m elevation on Mauna Kea, Hawaii differed in their UV screening capabilities. We further compared the degree to which T varied along an elevation gradient in the native shrub and the introduced forb to evaluate whether these species differed in their abilities to adjust their levels of UV screening in response to elevation changes in UV-B. For plants growing in the Mauna Kea alpine/upper subalpine, we found that adaxial T, measured with a UVA-PAM fluorometer, varied significantly among species but did not differ between native (mean = 6.0%; = 8) and non-native (mean = 5.8%; = 11) species. When data were pooled across native and non-native taxa, we also found no significant effect of growth form on T, though woody plants (shrubs and trees) were represented solely by native species whereas herbaceous growth forms (grasses and forbs) were dominated by non-native species. Along an elevation gradient spanning 2600-3800 m, T was variable (mean range = 6.0-11.2%) and strongly correlated with elevation and relative biologically effective UV-B in the exotic ; however, T was consistently low (3%) and did not vary with elevation in the native . Results indicate that high levels of UV protection occur in both native and non-native species in this high UV-B tropical alpine environment, and that flexibility in UV screening is a mechanism employed by some, but not all species to cope with varying solar UV-B exposures along elevation gradients.
地球气候的持续变化正在改变许多植物物种的海拔分布范围，外来物种往往比本地物种向更高海拔扩张得更多。这些由气候变化引起的分布变化不可避免地使植物暴露于新的生物和非生物环境中，包括变化的太阳紫外线（UV）-B（280-315纳米）辐射环境。外来物种向更高海拔的更大迁移潜力是否意味着它们比本地物种具有更有效的紫外线防护机制？在本研究中，我们调查了代表不同生长形式的多种植物物种的叶片表皮紫外线-A透过率（T），以测试生长在夏威夷莫纳克亚山海拔2800米以上的本地和外来物种在紫外线筛选能力上是否存在差异。我们进一步比较了本地灌木和引入的草本植物中T沿海拔梯度变化的程度，以评估这些物种在响应UV-B海拔变化时调整其紫外线筛选水平的能力是否存在差异。对于生长在莫纳克亚山高山/亚高山上部的植物，我们发现，用UVA-PAM荧光计测量的近轴T在物种间有显著差异，但本地物种（平均值 = 6.0%；n = 8）和外来物种（平均值 = 5.8%；n = 11）之间没有差异。当汇总本地和外来分类群的数据时，我们还发现生长形式对T没有显著影响，尽管木本植物（灌木和树木）仅由本地物种代表，而草本生长形式（草和草本植物）以外来物种为主。在跨越2600-3800米的海拔梯度上，T是可变的（平均范围 = 6.0-11.2%），并且与外来植物中的海拔和相对生物有效UV-B密切相关；然而，本地植物中的T始终较低（3%），并且不随海拔变化。结果表明，在这个高UV-B热带高山环境中，本地和外来物种都具有高水平的紫外线防护，并且紫外线筛选的灵活性是一些但不是所有物种用来应对沿海拔梯度变化的太阳UV-B照射的一种机制。
