Three new cryptic species of Begonia section Baryandra (Begoniaceae) from the Philippine archipelago supported by morphological and molecular evidence

Background and aims – The Philippine archipelago harbours the world’s greatest diversity of flowering plants, yet it is identified as a global plant diversity darkspot where much of this diversity remains poorly documented and inadequately sampled. To address this knowledge gap, extensive botanical explorations have been conducted, leading to the discovery of three new Begonia species from Panay and Mindanao Islands, which are described and illustrated herein.

Material and methods – All morphological descriptions and measurements are based on recently collected living and herbarium specimens. The new species are included in a phylogenetic analysis based on noncoding plastid regions (ndhA intron, ndhF-rpl 32 spacer, and rpl 32 - trnL spacer) and the nuclear internal transcribed spacer (nrITS) region from the assembled plastome and nuclear ribosomal DNA sequences. Key results – The newly described species from Mindanao (Begonia absiana sp. nov. and B. amorosoana sp. nov.) exhibit close morphological similarities to B. acuminatissima, while the novel species from Panay (B. panayica sp. nov.) shows affinity to B. biliranensis.

The phylogenetic analyses confirmed the monophyly of B. sect. Baryandra but revealed significant cytonuclear discordance and unresolved relationships within the group. All three new species were placed in a well-supported clade, but their precise relationships remain uncertain, possibly reflecting rapid diversification.

Conclusion – These findings underscore an urgent need to intensify botanical exploration and conservation efforts in the Philippines to protect these unique evolutionary lineages before their habitats are lost.