CLAY AFFINITY AND ENDEMISM IN CALIFORNIA'S FLORA

While the role of harsh soils in shaping the endemic flora of California has been extensively studied (e.g., serpentine endemism), plant endemism to many other soils within California is still poorly explored. Clay soils present substantial physical, chemical, and hydraulic challenges to plant life due to the extreme chemical and physical properties of clay particles. We conducted an extensive search of California herbarium records to generate a list of minimum-rank taxa found within California with potential clay affinity which we supplemented with the Jepson eFlora and the California Native Plant Society's Rare Plant Inventory. We assessed over 53,000 herbarium voucher records to evaluate each taxon's affinity and endemism to clay soils and found evidence for endemism to clay soils in the California flora. We ranked affinity to clay soils for 217 taxa and found that a third of those taxa are endemic to clay soils. From the results, we provide a database of clay affinity with notes on life form, habitat associations, distribution, special status and rarity.