Abstract
The spatial patterns of biodiversity and their underlying mechanisms have been an active area of research for a long time. In this study, a total of 63 samples (20m × 30m) were systematically established along elevation gradients on Mount Tai and Mount Lao, China. We explored altitudinal patterns of plant diversity in the two mountain systems. In order to understand the mechanisms driving current diversity patterns, we used phylogenetic approaches to detect the spatial patterns of phylogenetic diversity and phylogenetic structure along two elevation gradients. We found that total species richness had a monotonically decreasing pattern and tree richness had a unimodal pattern along the elevation gradients in the two study areas. However, altitudinal patterns in shrub richness and herbs richness were not consistent on the two mountains. At low elevation, anthropogenic disturbances contributed to the increase of plant diversity, especially for shrubs and herbs in understory layers, which are more sensitive to changes in microenvironment. The phylogenetic structure of plant communities exhibited an inverted hump-shaped pattern along the elevation gradient on Mount Tai, which demonstrates that environmental filtering is the main driver of plant community assembly at high and low elevations and inter-specific competition may be the main driver of plant community assembly in the middle elevations. However, the phylogenetic structure of plant communities did not display a clear pattern on Mount Lao where the climate is milder. Phylogenetic beta diversity and species beta diversity consistently increased with increasing altitudinal divergence in the two study areas. However, the altitudinal patterns of species richness did not completely mirror phylogenetic diversity patterns. Conservation areas should be selected taking into consideration the preservation of high species richness, while maximizing phylogenetic diversity to improve the potential for diversification in the future.
Highlights
The spatial patterns of species diversity adapted to the main environmental gradient have been a hot issue in ecological and environmental sciences [1]
We examined phylogenetic structure along two elevation gradients to understand the mechanisms that are driving current diversity patterns
We identified the prevailing forces structuring the species distribution of plants across an elevation gradient on two mountains by using phylogenetic and traditional diversity analyses in combination
Summary
The spatial patterns of species diversity adapted to the main environmental gradient have been a hot issue in ecological and environmental sciences [1]. Comprehending spatial patterns in biodiversity and the causal factors behind them are fundamental to developing sound conservation and management strategies [2, 3], as well as to studying global climate change and predicting its biological impacts on vegetation [4, 5]. The most common pattern is a unimodal curve with high richness at intermediate altitudes, which accounts for about 50% of previous studies. Another common pattern is a monotonically decreasing curve with increasing elevation, found in about 25% of previous studies. The variation in species diversity patterns can be caused by many factors, such as climate, productivity, anthropogenic influences, evolutionary history, and biotic interactions, e.g. competition and facilitation [9, 10]. There are many proposed hypotheses to explain the altitudinal patterns, the underlying mechanisms remain poorly understood [11]
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