2025/12/01 by Chih‐Chieh Yu, Zhi‐Qiong Mo, Jing‐Yi Lu +4 · 1 voice
Agricultural and Biological Sciences · #Plant Diversity and Evolution #Bryophyte Studies and Records #Fern and Epiphyte Biology
paper · doi:10.1002/ajb2.70141
PREMISE: The placement of Sladeniaceae s.l. (Sladenia and Ficalhoa) within Ericales has remained contentious, largely due to incongruent molecular signals between plastid and nuclear loci and lack of clear morphological synapomorphies supporting its circumscription. Resolving its phylogenetic position is essential for clarifying evolutionary relationships along the backbone of Ericales. METHODS: We used genome-skimming and Angiosperms353 data to reconstruct plastid and nuclear phylogenies of Ericales, with comprehensive sampling of Sladeniaceae, Pentaphylacaceae, and allied families. Phytop and SNaQ analyses were applied to evaluate incomplete lineage sorting (ILS) and introgression. Divergence times were estimated using a relaxed-clock birth-death model in the IQ2MC pipeline, and paleo-niche modeling was used to infer the historical distribution of Sladenia. RESULTS: Plastid phylogenies support the inclusion of Ficalhoa within Sladeniaceae, whereas nuclear trees place Ficalhoa as sister to Pentaphylacaceae, indicating strong cytonuclear discordance. Our analyses revealed a high level of incomplete lineage sorting at the nodes subtending Sladenia, Ficalhoa, and Pentaphylacaceae (ILS-i = 84.8%), which may be explained by the rapid early diversification of core Ericales during the mid-Cretaceous (~110-105 million years ago). No evidence of introgression was detected between Ficalhoa and Sladenia. CONCLUSIONS: Our findings suggest that stochastic sorting of ancestral plastid polymorphisms during rapid diversification may be the primary cause of cytonuclear discordance in the placement of Ficalhoa, although ancient plastid capture cannot be ruled out. These results support the inclusion of Ficalhoa within Pentaphylacaceae and underscore the roles of rapid diversification and incomplete lineage sorting in shaping deep phylogenetic relationships in Ericales.