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PLANT DIVERSITY AND ENDEMISM IN THE CALIFORNIA FLORISTIC PROVINCE

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The California Floristic Province (CFP) is an area of high biodiversity and endemism corresponding roughly to the portion of western North America having a Mediterranean-type climate. High levels of diversity and endemism in the CFP are attributed to the unique geo-climatic setting of the region. In recent years, much has been learned about the origins of plant diversity in western North America. This work, however, has been hindered by a focus on political rather than biotic regions, such that much more is known about diversity and endemism in the state of California than the natural biotic region represented by the CFP. Here we present a preliminary list of native land plants (vascular plants and bryophytes) found in the CFP, as well as an analysis of diversity and endemism patterns at the level of both species and minimum rank taxa (MRT; species and infraspecific taxa). A total of 6,927 MRT are native to the CFP, including 6,143 vascular plants and 784 bryophytes. Of these, 2,612 vascular plants are endemic to the CFP (42%) compared to 37 endemic bryophytes (5%). Finally, 2,506 native CFP vascular plant MRT (41% of the CFP flora) and 454 CFP bryophyte MRT (58% of the CFP flora) are found outside California in the Oregon and Baja California parts of the CFP. This high degree of sharing across political boundaries among both vascular plants and bryophytes highlights the cohesiveness of the CFP, and the need to focus more research effort on biotic regions.
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... Another biodiversity hotspot in North America is the California Floristic Province (CFP) (Calsbeek et al., 2003;Burge et al., 2016) and it is considered one of the world's top 25 most biologically rich and endangered terrestrial ecosystems (Myers et al., 2000). The CFP is an area with high plant diversity and endemism and exhibits a Mediterranean-type climate that extends to southern Oregon, western Nevada, and northern Baja California, Mexico (Raven and Axelrod, 1978). ...
... The CFP is an area with high plant diversity and endemism and exhibits a Mediterranean-type climate that extends to southern Oregon, western Nevada, and northern Baja California, Mexico (Raven and Axelrod, 1978). A total of 5006 species native to the CFP region exist with an estimate of 36.9 endemism (Burge et al., 2016). Compared to other areas of North America with high endemic plant and animal taxa, the CFP is the largest and has more identifiable subspecies than the central and northeastern United States and Canada combined (Calsbeek et al., 2003). ...
... California's flora, the Jepson Manual [5], classifies the state into ten ecoregions that represent different geographic divisions based on distinctive types of dominant vegetation, topographic, geologic and climatic conditions. Each ecoregion has a distinctive set of endemic species and communities adapted to specific climatic conditions [5,6] (see File S1 for a more detailed description). The ecoregions reveal the great vegetative diversity and climate variability that encompasses the state of California. ...
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Climate change is affecting Mediterranean climate regions, such as California. Retrospective phenological studies are a useful tool to track biological response to these impacts through the use of herbarium-preserved specimens. We used data from more than 12,000 herbarium specimens of 29 dominant native plant species that are characteristic of 12 broadly distributed vegetation types to investigate phenological patterns in response to climate change. We analyzed the trends of four phenophases: preflowering (FBF), flowering (F), fruiting (FS) and growth (DVG), over time (from 1830 to 2023) and through changes in climate variables (from 1896 to 2023). We also examined these trends within California’s 10 ecoregions. Among the four phenophases, the strongest response was found in the timing of flowering, which showed an advance in 28 species. Furthermore, 21 species showed sequencing in the advance of two or more phenophases. We highlight the advances found over temperature variables: 10 in FBF, 28 in F, 17 in FS and 18 in DVG. Diverse and less-consistent results were found for water-related variables with 15 species advancing and 11 delaying various phenophases in response to decreasing precipitation and increasing evapotranspiration. Jepson ecoregions displayed a more pronounced advance in F related to time and mean annual temperature in the three of the southern regions compared to the northern ones. This study underscores the role of temperature in driving phenological change, demonstrating how rising temperatures have predominantly advanced phenophase timing. These findings highlight potential threats, including risks of climatic, ecological, and biological imbalances.
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... The Jepson Ecoregions (88) used in these analyses divide the state into major ecological regions sharing similar climate, topography, flora, and vegetation mosaics. Eighty percent of the state lies within the California Floristic Province-CFP (Northwestern, Cascade Range, Sierra Nevada, Great Valley, Central Western, and Southwestern ecoregions)-characterized by a Mediterranean-type climate (cool wet winters, warm dry summers) and exceptionally high plant diversity with 20% of all vascular plant species found in the United States, 37% of which are endemic (89,90). Vegetation of the CFP spans chaparral (evergreen shrublands), coastal scrub, and oak woodlands and grasslands in the south and at lower elevations in valleys and foothills, to mixed evergreen, conifer, montane, and subalpine forests in the north and at higher elevations. ...
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