Format: ORAL

Diego F. Morales-Briones1, Gudrun Kadereit1

1 Ludwig-Maximilians-Universität München, Munich, Germany

Caroxyloneae and Salsoleae constitute a species-rich lineage of Amaranthaceae containing around 40 genera and 300400 species, including the largely polyphyletic Salsola. Members of this lineage are primarily distributed in the steppes and deserts of Eurasia, northern and southern Africa. It includes leaf- and stem-succulent halophytic, xerohalophytic, xerophytic, and ruderal plants, where C4 photosynthesis is prominent. Generic boundaries in Caroxyloneae and Salsoleae have been historically a matter of long-standing debates, with numerous transfers, reinstatements, or newly established genera in recent years. To date, phylogenetic analyses of the tribe have been based on a limited number of DNA regions, leaving most phylogenetic relationships unclear in an already highly taxonomic challenging group. To build a comprehensive backbone phylogeny of the group to clarify generic boundaries and investigate patterns of C4 photosynthesis, we used 483 putative single-copy loci from a custom target enrichment bait set and sampled 175 spp. from 36 genera from Caroxyloneae and Salsoleae. We recovered many paralogs for all species, including many pseudo-gene copies. These paralogs were spread across all Chenopods II, with several species even having gene copies as far as nested within Polycnemoideae (one of the other subfamilies in Amaranthaceae). This extreme paralog pattern largely halted the ability to infer orthologs using tree-based methods because the many duplications found in the gene trees resulted in mainly small orthologs, which ultimately resulted in a phylogeny with massive discordance and low to no support for most nodes. Here, we will explore the challenges and strategies for overcoming the issue of rampant paralogy to attempt to build a backbone of Caroxyloneae and Salsoleae.