Abstract
Mount Kenya is of ecological importance in tropical east Africa due to the dramatic gradient in vegetation types that can be observed from low to high elevation zones. However, species richness and phylogenetic diversity of this mountain have not been well studied. Here, we surveyed distribution patterns for a total of 1,335 seed plants of this mountain and calculated species richness and phylogenetic diversity across seven vegetation zones. We also measured phylogenetic structure using the net relatedness index (NRI) and the nearest species index (NTI). Our results show that lower montane wet forest has the highest level of species richness, density, and phylogenetic diversity of woody plants, while lower montane dry forest has the highest level of species richness, density, and phylogenetic diversity in herbaceous plants. In total plants, NRI and NTI of four forest zones were smaller than three alpine zones. In woody plants, lower montane wet forest and upper montane forest have overdispersed phylogenetic structures. In herbaceous plants, NRI of Afro‐alpine zone and nival zone are smaller than those of bamboo zone, upper montane forest, and heath zone. We suggest that compared to open dry forest, humid forest has fewer herbaceous plants because of the closed canopy of woody plants. Woody plants may have climate‐dominated niches, whereas herbaceous plants may have edaphic and microhabitat‐dominated niches. We also proposed lower and upper montane forests with high species richness or overdispersed phylogenetic structures as the priority areas in conservation of Mount Kenya and other high mountains in the Eastern Afro‐montane biodiversity hotspot regions.
Highlights
Plant richness in high mountains is one of the most important issues in biodiversity conservation, due to global climate change (Bhattarai & Vetaas, 2003; Li, Kraft, Yu, & Li, 2015; Trigas, Panitsa, & Tsiftsis, 2013; Vetaas & Grytnes, 2002)
Li et al (2015) found that compared to other communities, the evergreen broad-leaved forests in Dulong Valley in China had the highest levels of species richness and phylogenetic diversity, as well as an overdispersed phylogenetic structure, and suggest that communities with high species richness or an overdispersed phylogenetic signal should be the focus for biodiversity conservation, as these areas may help maximize the potential of local flora to respond to future global change
The species richness of woody and herbaceous plants of forests is expected to be affected by environmental variation, forest canopy, and anthropogenic disturbances (Clinton, 2003; Schmitt, Denich, Demissew, Friis, & Boehmer, 2010; Zhang, Huang, Wang, Liu, & Du, 2016)
Summary
Plant richness in high mountains is one of the most important issues in biodiversity conservation, due to global climate change (Bhattarai & Vetaas, 2003; Li, Kraft, Yu, & Li, 2015; Trigas, Panitsa, & Tsiftsis, 2013; Vetaas & Grytnes, 2002). Highly nonrandom patterns, for example, phylogenetic signals in environmental tolerances or localized speciation events, could create incongruent taxonomic and phylogenetic diversity patterns (Devictor et al, 2010; Tucker & Cadotte, 2013). We analyze changes in taxonomic and phylogenetic diversity across different vegetation zones of Mount Kenya, which is the largest ancient extinct volcano in the Great Rift Valley area, and the second highest peak in Africa (Speck, 1982). It constitutes an important reservoir for plant diversity, including a substantial number of endemic and endangered species. We aim to compare the diversity patterns between woody and herbaceous plants in order to a get better insight into the factors contributing to observed patterns in diversity
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