Phylogenomics reveals conservation challenges and opportunities for cryptic endangered species in a rapidly disappearing desert ecosystem

There is growing evidence for the decline of cryptic species across the planet as a result of human activities. Accurate data regarding patterns of poorly known or hard-to-find species diversity is essential for the recognition and conservation of threatened species and ecosystems. Casey’s June beetle Dinacoma caseyi is a federally listed endangered species restricted to the Coachella Valley in southern California, where rapid development is leading to habitat fragmentation. This fragmentation may be disproportionately impacting a wide-range of poorly-dispersing, cryptic species, including Casey’s June beetle, which has flightless females. We characterized 1876 single nucleotide polymorphisms from across the genome along with 1480 bp of mitochondrial DNA of all confirmed extant Dinacoma populations. We found that Dinacoma is isolated into three distinct species, including evidence for a previously undescribed species revealed during this study. Each is restricted to a small part of the inland desert region. Our results suggest unappreciated and fine scale diversity, which may be reflected in the other cryptic species of the region. Patterns of diversity in non-vagile species should guide ongoing conservation planning in the region. These results show that genetic exchange within the one remaining island of beetle habitat (Palm Canyon Wash) is not limited. However, non-vagile species, such as Casey’s June beetle, may not colonize suitable but fragmented habitat islands which presents risks to the species due to habitat loss and periodic natural events that may put the single population at risk of extirpation.