A matter of distance: Native bee lineages and diversity in fragmented landscapes

Insects are among the most ecologically diverse animal groups and are experiencing global declines. Native bees, vital pollinators in many ecosystems, are particularly vulnerable to habitat loss, fragmentation, and climate variability; yet, few long-term datasets exist to assess their responses. Here, we present results from a 13-year, seven-season monitoring effort of native bee assemblages in coastal southern California, a global bee biodiversity hotspot. Bees were sampled from 1-hectare plots of native coastal scrub embedded in two landscape contexts: large natural reserves (n = 7) and small urban fragments (n = 7). We assess patterns in species richness, Shannon diversity, and interannual turnover, and examine how diversity metrics vary in response to landscape context and climate conditions. Preliminary results suggest reserves support ~30% more species than fragments, though this gap varies across years. We observe higher temporal species turnover (Bray-Curtis and Jaccard dissimilarity) among fragments, suggesting reduced stability in their communities over time. To contextualize these trends in an evolutionary framework, we constructed a near-complete phylogeny for the bee species in our study by integrating a global bee supermatrix with newly generated COI sequences and barcodes from public databases. Ongoing work will quantify phylogenetic diversity and test whether evolutionary history predicts species persistence in different landscape contexts. By linking long-term biodiversity data with habitat configuration and interannual climate variability, our study provides new insights into how land-use and climate change interact to shape insect communities. These findings inform conservation strategies for preserving bee diversity, including a rich evolutionary history.