Genomic insights into sex-linked regions and dioecy in the ivory palm (Phytelephas aequatorialis)

Background and Aims: Dioecy has evolved independently multiple times in Palms, yet the genetic mechanisms underlying sex determination remain poorly understood across the family. Current knowledge is limited to genera from the subfamily Coryphoideae, in which Phoenix and Kerriodoxa independently recruited the same genomic region as the sex determining locus, suggesting a potentially convergent evolutionary pathway. Whether this pattern extends across the family remains unknown. Here, we investigate the genetic basis of sex determination in Phytelephas aequatorialis, from the Ceroxyloideaea palm subfamily, to identify its sex chromosome system, sex-linked genomic region, and candidate sex-determining genes. Methods: Using exon capture sequencing data from male and female individuals of P. aequatorialis, we analyzed genome wide sequence polymorphisms to detect signatures of sex linkage. Key Results: Our analyses reveal an XY sex chromosome system in Phytelephas, similar to that reported in the few dioecious palm species investigated to date. However, sex linkage maps to a distinct genomic region, indicating an independent origin of the sex-determining locus. We further identified 16 high confidence sex-linked genes with key roles in developmental processes and hormone signaling pathways, making them key candidates for involvement in sex determination. Sex-specific genetic markers were successfully developed from a subset of these genes. Conclusions: Our study suggests that in P. aequatorialis, the independent evolution of sex separation has relied on distinct genomic regions and genes, highlighting multiple evolutionary pathways leading to dioecy across the palm family. Comparative genomic analyses across additional lineages will be essential to reconstruct the evolutionary history of sex chromosomes and sex separation in this family.