Altitudinal diversity of aquatic plants in the Qinghai‐Tibet Plateau

Abstract

Altitudinal diversity of terrestrial plants has been widely studied, whereas little is known for the patterns of aquatic plants. Here, we used a standardised field dataset to quantify the altitudinal patterns in the diversity and structure of aquatic plant assemblages, as well as the relationships between diversity indices and environmental variables. Large‐scale field investigations were carried out in 128 sites ranging from 2,280 to 5,020 m above sea level across the southern part of Qinghai‐Tibet Plateau, China. In total, 102 species of aquatic plants were recorded, belonging to 67 genera, 31 families. Five taxonomic, phylogenetic, and functional indices were calculated for each collection site. We firstly examined altitudinal patterns of these diversity indices, then quantified the variations of indices across water areas, water flow, and soil matrix, respectively. We also explored the relationships between diversity indices and environmental variables using redundancy and variance partitioning analysis, to detect the ecological variables that drove the diversity. The results showed that taxonomic, phylogenetic, and functional diversity of aquatic plants decreased with increasing altitude. Net relatedness index of aquatic plants showed a hump pattern along the altitude gradient, with a peak around 3,800 m above sea level. There was no obvious trend in the net functional relatedness index of aquatic plants with altitude. Annual mean temperature was the most important variable associated with the taxonomic, phylogenetic, and functional diversity. Water area and water flow were significantly associated with functional structure, but not phylogenetic structure. Soil matrix also correlated with aquatic plant diversity. A large‐scale altitudinal gradient can influence aquatic plant diversity. Environmental filtering and niche convergence might have played dominant roles in the increasing and decreasing stages of phylogenetic structure of aquatic plant assemblages, respectively, along the altitudinal gradient. Phylogenetic and functional structure of aquatic plant assemblages showed different patterns along the altitudinal gradient, and the environmental variables better explained the change of functional structure than did the phylogenetic variables. This is the first comprehensive study on the species, phylogeny, and function of aquatic plant assemblages along a large‐scale altitudinal gradient. We found an altitudinal decline in the diversity of aquatic plants and different patterns in the phylogenetic and functional structures of aquatic plant assemblages. These findings indicate that functional traits have high phenotypic plasticity and are more affected by environments than phylogenetic relationships which are mainly shaped by evolutionary processes.

Unravelling the factors affecting multiple facets of macroinvertebrate beta diversity in the World's Third Pole

“…Indeed, upper canyon streams, especially those glacier‐fed ones, harbour many unique and environmentally sensitive species and lineages (Li, Wang, et al, 2019; Xu et al, 2018), as well as serve as sources of colonizers to streams in the lower reaches. These streams also have experienced and are forecasted to experience increasingly rapid climate change (Hamerlik & Jacobsen, 2012; Zhou et al, 2022). With the intensification of global warming, invertebrate assemblages in currently cold‐climate upper streams may be gradually replaced by those living in the lowland area.…”

“…environmental filtering) is most often the predominant force of community assembly (Heino, Melo, Siqueira, Soininen, et al, 2015; Hill et al, 2019). However, it is still unclear whether these findings and rules are applicable to aquatic communities in alpine regions, such as the Tibetan plateau (also known as the ‘World's Third Pole’), where related research is still in its infancy (Zhou et al, 2022).…”

“…However, it is still unclear whether these findings and rules are applicable to aquatic communities in alpine regions, such as the Tibetan plateau (also known as the 'World's Third Pole'), where related research is still in its infancy (Zhou et al, 2022).…”

“…Organisms inhabiting these streams are the products of adaptation to extreme environments, as well as geological events like the Tibetan Plateau uplift (Zhang et al, 2000). Studies on diversity patterns of stream organisms not only reveal community patterns in natural environmental conditions, but also can be used as a benchmark to predict the impacts of environmental change on alpine biotas and to infer the history of this plateau's geology and climate (Zhou et al, 2022).…”

Geographic patterns and environmental correlates of taxonomic and phylogenetic diversity of aquatic plants in China

“…A hump‐shaped pattern between species richness (SR) of aquatic plants and latitude was found across Europe and North Africa, with the highest peak being located between 40° and 50°N (Chappuis et al, 2012), and this pattern has been confirmed by recent work on freshwater plants in Europe, which found the highest peak at ~55°N (Alahuhta et al, 2020). Second, aquatic plant diversity commonly decreases with increasing altitude (Jones et al, 2003; Lacoul & Freedman, 2006a; Hrivnák et al, 2013; Zhou et al, 2022a), and a recent study in northern Spain found that altitude was not a good predictor of the diversity of aquatic plant assemblages across ponds ranging from 700 to 2100 m above sea level (Fernández‐Aláez et al, 2018). Third, there have been few reports on the longitude pattern of aquatic plant diversity, but the study on the local diversity pattern of aquatic plants in the Hexi Corridor of China shows that there is no significant correlation between longitude and diversity (Tian et al, 2020).…”