Deterministic process shape coexistence of alpine meadow species based on DNA barcode sequences

Abstract

Deterministic and stochastic processes can simultaneously construct plant community assemblages. However, how they shape herbaceous plants’ phylogeny and functional structure in alpine meadows is unclear, hindering the understanding of species’ coexistence processes and diversity maintenance in herbaceous communities. We established a permanent research sample plot of 3.76 × 105 m2 in alpine meadows on the northeastern Qinghai-Tibet Plateau of China, investigated the flora, measured nine functional traits, analyzed inter- and intraspecific variation, and visualized phylogenetic signals. The results show that: (1) The phylogenetic structure based on DNA barcode sequences exhibits a range from competitive exclusion (NRI < 0, NTI < 0) to habitat filtering (NRI > 0, NTI > 0) along an altitude gradient. (2) The interspecific functional structure varied with altitude, reflecting different survival strategies of plants. In contrast, intraspecific trait variation was associated with environmental screening processes. (3) Except for PH and LPC, none of the functional traits showed a phylogenetic signal (K < 1, P > 0.05), suggesting that they are more influenced by environmental heterogeneity; with increasing altitude, enhanced environmental filtering favors species with conservative strategies of selection. These results suggest that deterministic processes (interspecific competition, habitat filtering) may be the main mechanisms of species coexistence in alpine meadows. Low altitude drives niche differentiation of coexisting species through competitive exclusion to reduce competition for resources. In contrast, high altitude species lead to the coexistence of functionally similar species through habitat filtering.