Zachary Hoover

The sky-island mountain ranges of the southwestern United States offer a natural setting for examining how climate and geography impact population structure and gene flow. The jewel scarab, Chrysina gloriosa, is a charismatic beetle restricted to high-elevation habitats in these mountains, where isolation and environmental change may be driving population divergence. We used low-coverage whole-genome resequencing and species distribution modelling to study population structure, gene flow, and demographic history across five mountain ranges in Arizona and West Texas. Our results indicate strong genetic differentiation among most populations, with recent gene flow detected only between two neighboring ranges, possibly through male-mediated dispersal. Demographic analyses reveal a decline in effective population size following late Pleistocene climate shifts, consistent with habitat contraction inferred from paleo-vegetation records. Future climate projections suggest further habitat loss and increasing isolation. Together, these results show how past and ongoing climatic changes have and continue to shape population structure in C. gloriosa, with important implications for its long-term evolutionary potential. These findings mirror patterns documented across sky-island taxa globally, supporting a general model in which climate-driven habitat dynamics and dispersal limitation interact to generate recurrent cycles of population fragmentation, genetic erosion, and demographic instability in montane systems.

The jewel scarab Chrysina gloriosa is one of the most charismatic beetles in the United States and is found from the mountains of West Texas to the Southeastern Arizona sky islands. This species is highly sought by professional and amateur collectors worldwide due to its gleaming metallic coloration. However, the impact of the large-scale collection of this beetle on its populations is unknown, and there is a limited amount of genetic information available to make informed decisions about its conservation. As a first step, we present the genome of C. gloriosa, which we reconstructed using a single female specimen sampled from our ongoing effort to document population connectivity and the demographic history of this beetle. Using a combination of long-read sequencing and Omni-C data, we reconstructed the C. gloriosa genome at a near-chromosome level. Our genome assembly consisted of 454 scaffolds spanning 642 MB, with the ten largest scaffolds capturing 98% of the genome. The scaffold N50 was 72 MB, and the BUSCO score was 95.5%. This genome assembly will be an essential tool to accelerate understanding C. gloriosa biology and help make informed decisions for the conservation of Chrysina and other species with similar distributions in this region. This genome assembly will further serve as a community resource for comparative genomic analysis.

Positive-sense single-stranded RNA (ssRNA) bacteriophages (phages) were first isolated six decades ago. Since then, extensive research has been conducted on these ssRNA phages, particularly those infecting E. coli. With small genomes of typically 3–4 kb that usually encode four essential proteins, ssRNA phages employ a straightforward infectious cycle involving host adsorption, genome entry, genome replication, phage assembly, and host lysis. Recent advancements in metagenomics and transcriptomics have led to the identification of ~65,000 sequences from ssRNA phages, expanding our understanding of their prevalence and potential hosts. This review article illuminates significant investigations into ssRNA phages, with a focal point on their structural aspects, providing insights into the various stages of their infectious cycle.