Contrasting effects of light, soil chemistry and phylogeny on leaf nutrient concentrations in cave-dwelling plants

Biogeochemical niche conservatism relates to plant species diversification and life form evolution in a subtropical montane evergreen broad‐leaved forest

“…To determine leaf C and N concentrations, leaf samples were analyzed using an elemental analyzer (Vario MAX CN Elemental Analyzer). Leaf P, K, Ca, and Mg concentrations were determined using an inductively coupled plasma emission spectrum (iCAP Qc, Thermo Fisher Scientific; Bai et al, 2020 ).…”

“…Previous studies have found that the values of Blomberg's K or Pagel's λ in leaf elemental concentrations are usually found to be lower than unity (i.e., pure BM process) even if they differ significantly from zero (i.e., no phylogenetic signal; e.g., Duffin et al, 2019 ; Hao et al, 2015 ; Peñuelas et al, 2010 ; Sardans et al, 2015 ), suggesting that the generation of biogeochemical niche conservatism might not follow a drift or niche retention model (Cooper et al, 2010 ). Several studies have shown that the values of Pagel's δ were higher than unity for leaf N, P, K, Ca, Mg, S, Fe, and Zn concentrations in tropical karst tree species and cave‐dwelling herbaceous species (Bai et al, 2019 , 2020 ), suggesting that biogeochemical niche conservatism could be generated by niche shifting model (Cooper et al, 2010 ; Pagel, 1999 ). Alternatively, some studies have shown that the generation of biogeochemical niche conservatism might follow the phylogenetic inertia model, that is, stabilizing selection toward an optimum or optima (Bai et al, 2019 , 2020 ; Fernández‐Martínez et al, 2018 ).…”

“…Several studies have shown that the values of Pagel's δ were higher than unity for leaf N, P, K, Ca, Mg, S, Fe, and Zn concentrations in tropical karst tree species and cave‐dwelling herbaceous species (Bai et al, 2019 , 2020 ), suggesting that biogeochemical niche conservatism could be generated by niche shifting model (Cooper et al, 2010 ; Pagel, 1999 ). Alternatively, some studies have shown that the generation of biogeochemical niche conservatism might follow the phylogenetic inertia model, that is, stabilizing selection toward an optimum or optima (Bai et al, 2019 , 2020 ; Fernández‐Martínez et al, 2018 ). For example, Fernández‐Martínez et al ( 2018 ) found that the evolution of leaf P concentration could be best described by stabilizing selection towards an optimum in global plants.…”

“…This is the case in biogeochemical niche conservatism. For instance, Bai et al ( 2020 ) found the lower evolutionary rates of leaf N, P, K, Ca, Mg, S, Fe, Mn, and Zn concentrations in ferns than herbs in caves. Since the generation of biogeochemical niche conservatism has been supported by different evolutionary models, researchers can compare which evolutionary model best fits dataset (Cooper et al, 2010 ; Münkemüller et al, 2015 ).…”

“…The other is from the detection of evolutionary rate and evolutionary process. For example, Bai et al ( 2020 ) have demonstrated that herbs tend to have higher evolutionary rate than ferns for leaf N, P, K, Ca, Mg, S, Fe, Mn, and Zn concentrations in caves. Moreover, they found that the higher optimal values of leaf Ca, N, and Mg were evolutionary selected in cave‐dwelling herbs.…”