phyloDS: phylogeny-aware differential splicing across species, beyond reference annotations

Alternative splicing diverges rapidly between species, yet its comparative analysis lags far behind that of gene expression: junction orthology is defined on a single reference genome, species are treated as independent samples, and detected shifts are rarely grounded in sequence-level evidence. We present phyloDS, an RNA-seq–driven framework that resolves all three limitations. phyloDS defines orthologous splice junctions on multiple sequence alignments of one-to-one orthologous genes, tests their differential usage with a regularized Ornstein–Uhlenbeck model, and cross-validates detected shifts against splice-site predictions made from genomic sequence alone. Applied to primate brain and rodent heart transcriptomes, phyloDS recovered up to 2.9-fold more shared orthologous splice junctions than a reference-based strategy and kept type I error near nominal where competing methods inflate it more than two-fold. It identified 234 and 502 differentially used orthologous splice junctions in hominoids and mole-rats (86 and 141 unannotated), revealing a mitochondrial and contractile splicing signature in mole-rats .