The California Conservation Genomics Project: Characterizing Tamalia aphid galls as part of California’s landscapes

The University of California Conservation Genomics Project (CCGP) has three principal goals: 1) to identify biological populations harboring the greatest genomic diversity across the state’s diverse ecological regions (eco-regions); 2) to identify the most intact remaining eco-regions likely to be resilient in the face of climate change and novel land-use patterns; 3) to amass data on the genomic well-being of ecological keystone species.  We argue that Tamalia coweni (Aphididae), by inducing galls on a wide variety of Arctostaphylos (Ericaceae) shrubs in California’s landscapes, represents a keystone species. As seen in the wide variety of gall shape, size, and texture across host plant species, gall induction by Tamalia aphids is a unique manifestation of gene expression in both host plant and insect. Beyond providing critical nutriment and shelter for the aphids, galls support a variety of  associated arthropods, including socially parasitic Tamalia inquiline aphids, two specialist dipteran predators, opportunist predatory anthocorid bugs, gregarious Aprostocetus larvae (Eulophidae), and thigmotactic thrips. As a first step towards characterizing the genetics of T. coweni at a landscape level, we are creating a chromosome-level reference genome for T. coweni. At a population level, we are applying genome re-sequencing techniques for sampling Tamalia galls comprehensively across California’s eco-regions. Ultimately we will use these data to identify the regions and populations with the highest potential for safeguarding genetic and ecological diversity in perpetuity.