Elevation and phylogeny shape herbaceous seed dormancy in a biodiversity hotspot of southwest China

Seed dormancy contributes greatly to successful establishment and community stability and shows large variation over a continuous status scale in mountain ecosystems. Although empirical studies have shown that seed dormancy status (SDS) is shaped by elevation and phylogenetic history in mountain ecosystems, few studies have quantified their combined effects on SDS. Here, we collected mature seeds from 51 populations of 11 Impatiens species (Balsaminaceae) along an elevational gradient in the Gaoligong Mountains of southwest China and estimated SDS using mean dormancy percentage of fresh seeds germinated at three constant temperatures (15, 20, and 25°C). We downloaded 19 bioclimatic variables from WorldClim v.2.1 for each Impatiens population and used internal transcribed spacer (ITS), atpB-rbcL, and trnL-F molecular sequences from the GenBank nucleotide database to construct a phylogenetic tree of the 11 species of Impatiens. Logistic regression model analysis was performed to quantify the effects of phylogeny and environment on SDS. Results identified a significant phylogenetic SDS signal in the Impatiens species. Furthermore, elevation and phylogeny accounted for 63.629% of the total variation in SDS among the Impatiens populations. The best logistic model indicated that temperature was the main factor influencing variation in SDS among the Impatiens species, and model residuals were significantly correlated with phylogeny, but not with elevation. Our results indicated that seed dormancy is phylogenetically conserved, and climate drives elevational patterns of SDS variation in mountain ecosystems. This study provides new insights into the response of seed plant diversity to climate change.