California Floristic Province Research Articles

Local adaptation and phenotypic plasticity drive leaf trait variation in the California endemic toyon (Heteromeles arbutifolia).

To survive climate change and habitat loss, plants must rely on phenotypic changes in response to the environment, local adaptation, or migration. Understanding the drivers of intraspecific variation is critical to anticipate how plant species will respond to climate change and to inform conservation decisions. Here we explored the extent of local adaptation and phenotypic plasticity in Heteromeles arbutifolia, toyon, a species endemic to the California Floristic Province. We collected leaves from 286 individuals across toyon's range and used seeds from 37 individuals to establish experimental gardens in the northern and southern parts of toyon's range. We measured leaf functional traits of the wild-collected leaves and functional and fitness traits of the offspring grown in the experimental gardens. We then investigated the relationships between traits and source environment. Most traits we investigated responded plastically to the environment, and some traits in young seedlings were influenced by maternal effects. We found strong evidence that variation in leaf margins is a result of local adaptation to variation in temperature and temperature range. However, the source environment was not related to fitness traits or survival in the experimental gardens. Our findings reiterate the adaptive role of toothed leaf margins in colder and more seasonally variable environments. Additionally, we provide evidence that fitness of toyon is not dependent on where they are sourced, and thus toyon can be sourced across its range for restoration purposes.

Ceanothus: Taxonomic patterns in life history responses to fire.

Ceanothus (Rhamnaceae) is a large genus of shrubs that dominate California chaparral and are resilient to fires. Persistence is ensured by resprouting and/or seedling recruitment from dormant seed banks. Some species do both and others, the obligate seeders, are entirely dependent on seedling recruitment. The distribution of these two modes within the genus is poorly documented. We used all available publications that document species responses to fire and filled most gaps in the literature based on extensive field studies of more than 60 recent wildfires in California. The genus is divided into two subgenera, Ceanothus and Cerastes. Ceanothus is widely considered to comprise mostly resprouting species and Cerastes to consist of only obligate seeders. The subgenus Ceanothus includes resprouting species throughout their range from the eastern United States and Midwest to western United States. Within the California Floristic Province (CFP), a few species are unique in producing massive lignotubers that develop from repeated fires; however, within the CFP, the majority of species in this subgenus do not resprout and are obligate seeders. Two have disjunct subspecies that are facultative seeders or obligate seeders. Previously, speciation in this genus was contended to have occurred in the late Miocene within the CFP. The syndrome of obligate seeding is most strongly represented in this region, and we hypothesize that evolution of this syndrome was a response to increased predictability of fire driven by the Mediterranean climate and the long interval between fires.

Rapid shifts in grassland communities driven by climate change.

Many terrestrial plant communities, especially forests, have been shown to lag in response to rapid climate change. Grassland communities may respond more quickly to novel climates, as they consist mostly of short-lived species, which are directly exposed to macroclimate change. Here we report the rapid response of grassland communities to climate change in the California Floristic Province. We estimated 349 vascular plant species' climatic niches from 829,337 occurrence records, compiled 15 long-term community composition datasets from 12 observational studies and 3 global change experiments, and analysed community compositional shifts in the climate niche space. We show that communities experienced significant shifts towards species associated with warmer and drier locations at rates of 0.0216 ± 0.00592 °C yr-1 (mean ± s.e.) and -3.04 ± 0.742 mm yr-1, and these changes occurred at a pace similar to that of climate warming and drying. These directional shifts were consistent across observations and experiments. Our findings contrast with the lagged responses observed in communities dominated by long-lived plants and suggest greater biodiversity changes than expected in the near future.

Phylogenomic perspectives on speciation and reproductive isolation in a North American biodiversity hotspot: an example using California sages (Salvia subgenus Audibertia: Lamiaceae).

The California Floristic Province (CA-FP) is the most species-rich region of North America north of Mexico. One of several proposed hypotheses explaining the exceptional diversity of the region is that the CA-FP harbours myriad recently diverged lineages with nascent reproductive barriers. Salvia subgenus Audibertia is a conspicuous element of the CA-FP, with multiple sympatric and compatible species. Using 305 nuclear loci and both organellar genomes, we reconstruct species trees, examine genomic discordance, conduct divergence-time estimation, and analyse contemporaneous patterns of gene flow and mechanical reproductive isolation. Despite strong genomic discordance, an underlying bifurcating tree is supported. Organellar genomes capture additional introgression events not detected in the nuclear genome. Most interfertility is found within clades, indicating that reproductive barriers arise with increasing genetic divergence. Species are generally not mechanically isolated, suggesting that it is unlikely to be the primary factor leading to reproductive isolation. Rapid, recent speciation with some interspecific gene flow in conjunction with the onset of a Mediterranean-like climate is the underlying cause of extant diversity in Salvia subgenus Audibertia. Speciation has largely not been facilitated by gene flow. Its signal in the nuclear genome seems to mostly be erased by backcrossing, but organellar genomes each capture different instances of historical gene flow, probably characteristic of many CA-FP lineages. Mechanical reproductive isolation appears to be only part of a mosaic of factors limiting gene flow.

Chromosomal evolution, environmental heterogeneity, and migration drive spatial patterns of species richness in Calochortus (Liliaceae)

We used nuclear genomic data and statistical models to evaluate the ecological and evolutionary processes shaping spatial variation in species richness in Calochortus (Liliaceae, 74 spp.). Calochortus occupies diverse habitats in the western United States and Mexico and has a center of diversity in the California Floristic Province, marked by multiple orogenies, winter rainfall, and highly divergent climates and substrates (including serpentine). We used sequences of 294 low-copy nuclear loci to produce a time-calibrated phylogeny, estimate historical biogeography, and test hypotheses regarding drivers of present-day spatial patterns in species number. Speciation and species coexistence require reproductive isolation and ecological divergence, so we examined the roles of chromosome number, environmental heterogeneity, and migration in shaping local species richness. Six major clades-inhabiting different geographic/climatic areas, and often marked by different base chromosome numbers (n = 6 to 10)-began diverging from each other ~10.3 Mya. As predicted, local species number increased significantly with local heterogeneity in chromosome number, elevation, soil characteristics, and serpentine presence. Species richness is greatest in the Transverse/Peninsular Ranges where clades with different chromosome numbers overlap, topographic complexity provides diverse conditions over short distances, and several physiographic provinces meet allowing immigration by several clades. Recently diverged sister-species pairs generally have peri-patric distributions, and maximum geographic overlap between species increases over the first million years since divergence, suggesting that chromosomal evolution, genetic divergence leading to gametic isolation or hybrid inviability/sterility, and/or ecological divergence over small spatial scales may permit species co-occurrence.

Repeated patterns of reptile diversification in Western North America supported by the Northern Alligator Lizard (Elgaria coerulea).

Understanding the processes that shape genetic diversity by either promoting or preventing population divergence can help identify geographic areas that either facilitate or limit gene flow. Furthermore, broadly distributed species allow us to understand how biogeographic and ecogeographic transitions affect gene flow. We investigated these processes using genomic data in the Northern Alligator Lizard (Elgaria coerulea), which is widely distributed in Western North America across diverse ecoregions (California Floristic Province and Pacific Northwest) and mountain ranges (Sierra Nevada, Coastal Ranges, and Cascades). We collected single-nucleotide polymorphism data from 120 samples of E. coerulea. Biogeographic analyses of squamate reptiles with similar distributions have identified several shared diversification patterns that provide testable predictions for E. coerulea, including deep genetic divisions in the Sierra Nevada, demographic stability of southern populations, and recent post-Pleistocene expansion into the Pacific Northwest. We use genomic data to test these predictions by estimating the structure, connectivity, and phylogenetic history of populations. At least 10 distinct populations are supported, with mixed-ancestry individuals situated at most population boundaries. A species tree analysis provides strong support for the early divergence of populations in the Sierra Nevada Mountains and recent diversification into the Pacific Northwest. Admixture and migration analyses detect gene flow among populations in the Lower Cascades and Northern California, and a spatial analysis of gene flow identified significant barriers to gene flow across both the Sierra Nevada and Coast Ranges. The distribution of genetic diversity in E. coerulea is uneven, patchy, and interconnected at population boundaries. The biogeographic patterns seen in E. coerulea are consistent with predictions from co-distributed species.

Important pollinator species for conserving rare plant species endemic to San Clemente Island, California

Much effort has been spent on the conservation of rare, threatened, and endangered plants in the biodiversity hotspot of the California Floristic Province, however little is known about the identity of their pollinators. In this study we provide the first formal study on the identity of the invertebrate pollinators of five rare endemic island plant species from San Clemente Island, the southernmost of the California Channel Islands: Delphinium variegatum ssp kinkiense, Lithophragma maximum, Malacothamnus clementinus, Malva assurgentiflora ssp glabra, and Sibara filifolia. We surveyed plant-pollinator interactions at populations of each focal plant species using timed sweep-netting. We used pollinator capture data to compile bipartite interaction networks for each plant population, and calculated centrality indices (degree, betweenness centrality, and closeness centrality) of pollinators to identify species important to network stability. We found a significant effect of pollinator taxonomic group (fly, bee, wasp, or Lepidopteran) on some indices of pollinator centrality in interaction networks, and variation in pollinator centrality between different locations. Hoverflies, moths, and butterflies were important generalists with higher network centrality across all plant populations, while bees tended to be more specialists within their networks, except for the Malva assurgentiflora ssp glabra network, where bees were on average of higher centrality than flies. We recommend targeted restoration practices for future study that could support pollination both directly and indirectly to focal rare plant species of conservation interest across plant populations. These practices could augment general pollinator conservation best practices such as reducing pesticide use and planting native plant species to provide increased pollination to endangered plants.

Revision of the western Nearctic spider genus Cybaeina including the description of Neocybaeina gen. nov. and Rothaeina gen. nov. (Araneae: Cybaeidae: Cybaeinae).

This paper is the last in a series revising the Nearctic Cybaeinae spider fauna (Araneae: RTA clade: Cybaeidae) exclusive of Cybaeozyga Chamberlin & Ivie. The forested habitats of the west coast of North America are home to a diverse array of endemic Cybaeinae spider taxa. Many of these have very restricted distributions, especially within an area of the western United States of America from the Olympic Peninsula of northwestern Washington to the northern half of the California Floristic Province of California, a well-known biodiversity hotspot. Here we revise the genus Cybaeina Chamberlin & Ivie recognizing three species: the type species Cybaeus minutus Banks (= Cybaeina minuta (Banks)), C. confusa Chamberlin & Ivie, and a single new species C. dixoni Bennett spec. nov. We describe Neocybaeina Bennett gen. nov. with type species Cybaeina xantha Chamberlin & Ivie (= Neocybaeina xantha (Chamberlin & Ivie) comb. nov.) and a single new species N. burnetti spec. nov. Finally we describe Rothaeina Bennett gen. nov. with type species Cybaeina sequoia Roth (= Rothaeina sequoia (Roth) comb. nov.) and four new species R. beaudini Bennett spec. nov., R. jamesi Bennett spec. nov., R. mackinleyi Bennett spec. nov., and R. petersoni Bennett spec. nov. In addition to descriptions of the genera and both sexes of their included species (except for N. burnetti spec. nov. and R. beaudini Bennett spec. nov. which are known from females only), we provide diagnoses, illustrations, distribution maps, and, for the three species of Cybaeina and the five of Rothaeina gen. nov., identification keys. In closing, we discuss conservation implications for this cryptic and infrequently collected group of western Nearctic Cybaeinae, several of which are short-range endemic species.

Phylogeography and cohesion species delimitation of California endemic trapdoor spiders within the Aptostichus icenoglei sibling species complex (Araneae: Mygalomorphae: Euctenizidae).

Species delimitation is an imperative first step toward understanding Earth's biodiversity, yet what constitutes a species and the relative importance of the various processes by which new species arise continue to be debatable. Species delimitation in spiders has traditionally used morphological characters; however, certain mygalomorph spiders exhibit morphological homogeneity despite long periods of population-level isolation, absence of gene flow, and consequent high degrees of molecular divergence. Studies have shown strong geographic structuring and significant genetic divergence among several species complexes within the trapdoor spider genus Aptostichus, most of which are restricted to the California Floristic Province (CAFP) biodiversity hotspot. Specifically, the Aptostichus icenoglei complex, which comprises the three sibling species, A. barackobamai, A. isabella, and A. icenoglei, exhibits evidence of cryptic mitochondrial DNA diversity throughout their ranges in Northern, Central, and Southern California. Our study aimed to explicitly test species hypotheses within this assemblage by implementing a cohesion species-based approach. We used genomic-scale data (ultraconserved elements, UCEs) to first evaluate genetic exchangeability and then assessed ecological interchangeability of genetic lineages. Biogeographical analysis was used to assess the likelihood of dispersal versus vicariance events that may have influenced speciation pattern and process across the CAFP's complex geologic and topographic landscape. Considering the lack of congruence across data types and analyses, we take a more conservative approach by retaining species boundaries within A. icenoglei.

The morphological and ecological variation of Arctostaphylos (Ericaceae) fruit: A link between plant ecology and animal foraging behavior.

Persistent soil seed banks are characteristic of Arctostaphylos (Ericaceae) species in the Mediterranean-climate California Floristic Province. While most species are obligate seeders, regeneration of stands of all Arctostaphylos species ultimately depends on post-fire seedling recruitment. Arctostaphylos seed banks are created, in large part, by scatter-hoarding rodents. Variation in fruit morphology, therefore, is expected to impact the Arctostaphylos-rodent interaction. Seeds produce sufficient rewards (nutritious mature embryo) to entice rodents to disperse and ultimately bury seeds in the soil. Hard seed coats increase the time required to extract the embryo, encouraging rodents to choose storage over immediate predation, and nutlets are frequently empty. We assessed the variation of fruit nutlet fusion and seed viability among 38 Arctostaphylos taxa. Factors such as latitude, elevation, life history, ploidy, and phylogenetic position were also analyzed. Generalized mixed-effects models were used to determine the factors contributing to variation in fruit nutlet fusion and seed viability. Our results indicate that fruit volume and shape are the most important variables affecting nutlet fusion and seed viability. Additionally, other potential influences only show a weak correlation and are not predicted to significantly impact nutlet fusion or seed viability. These findings provide insights into evolved strategies used by plants to increase reproductive success via scatter-hoarding rodents. Our study benefits the conservation and restoration of Arctostaphylos stands by emphasizing the importance of animal-mediated dispersal and providing estimates of seed viability for different species. With the anticipated effects of climate change, such as departures from historic fire regimes, the preservation of the relationship between plants and animal foragers is crucial for the continued survival of Arctostaphylos and California's evergreen chaparral.

A 55,000-Year Reconstruction of Vegetation in the Los Angeles Basin: Insights into Future Change and a Better Guide for the Present

The California Floristic Province is a biodiversity hotspot. Endemic flora is threatened by climate change, habitat fragmentation and destruction. It is also host to the La Brea Tar Pits (LBTP), which in addition to its famous megafauna, preserves a rare long-term plant macrofossil record with taxonomic resolution to genus and species. The LBTP flora has the potential to provide a comprehensive vegetational history for the Los Angeles Basin and a dynamic baseline for modern conservation efforts. We used accelerator mass spectrometry (AMS) radiocarbon dating to establish a 55 ka timeline of plant presence in Los Angeles, California. We identified and radiocarbon dated 188 plant macrofossils from the La Brea Tar Pits collections. Eight distinct phases of vegetation were identified based on the loss or appearance of key taxa in the timeline. Pairwise similarity was calculated between each identified phase to compare changes to phase species makeup through time. The transition periods between phases were compared to existing climate proxy records to better understand forcings behind vegetation shifts. Two transition periods in the record are of interest to modern conservation efforts. First, fog-dependent closed cone pine species, Pinus muricata and Pinus radiata, become extirpated from the Los Angeles Basin at 48 ka. This disappearance corresponds with a period of extended drought. Second, repeated patterns of juniper species replacement during periods of megadrought, and their eventual extirpation at 12.8 ka, indicate the importance of land management choices in the ability of juniper populations to rebound after drought-induced die-off. Understanding the long-term dynamics of plant community structure in a region is crucial to managing landscapes in the context of global change, and these data are now being leveraged to inform local conservation efforts in the city of Los Angeles.

Checklist of true flies (Diptera) from San Luis Obispo County, California, U.S.A.: an outcome of the Fly School II taxonomic workshop

True flies (Diptera) are a hyper-diverse group of insects which are considerably under-studied compared to many other organisms. Here we report a list of taxa collected during the 2019 Fly School held in San Luis Obispo County, California, a region of the California Floristic Province biodiversity hotspot. From June 20th to July 6th, an international team of 35 entomologists collected and identified Diptera at 17 main sites across the county. The team identified a total of 68 families, 188 genera, and 133 species/species groups. Of these, we uncovered 21 potential new county records for California, expanding knowledge of geographic distributions for these taxa. We discuss the strengths and limitations of this list and suggest ideas for streamlining the publication of similar lists for other specialized taxonomic workshops.

Rarity, geography, and plant exposure to global change in the California Floristic Province

AbstractAimRarity and geographic aspects of species distributions mediate their vulnerability to global change. We explore the relationships between species rarity and geography and their exposure to climate and land use change in a biodiversity hotspot.LocationCalifornia, USA.TaxaOne hundred and six terrestrial plants.MethodsWe estimated four rarity traits: range size, niche breadth, number of habitat patches, and patch isolation; and three geographic traits: mean elevation, topographic heterogeneity, and distance to coast. We used species distribution models to measure species exposure—predicted change in continuous habitat suitability within currently occupied habitat—under climate and land use change scenarios. Using regression models, decision‐tree models and variance partitioning, we assessed the relationships between species rarity, geography, and exposure to climate and land use change.ResultsRarity, geography and greenhouse gas emissions scenario explained >35% of variance in climate change exposure and >61% for land use change exposure. While rarity traits (range size and number of habitat patches) were most important for explaining species exposure to climate change, geographic traits (elevation and topographic heterogeneity) were more strongly associated with species' exposure to land use change.Main conclusionsSpecies with restricted range sizes and low topographic heterogeneity across their distributions were predicted to be the most exposed to climate change, while species at low elevations were the most exposed to habitat loss via land use change. However, even some broadly distributed species were projected to lose >70% of their currently suitable habitat due to climate and land use change if they are in geographically vulnerable areas, emphasizing the need to consider both species rarity traits and geography in vulnerability assessments.

Reference genome of the rubber boa, Charina bottae (Serpentes: Boidae).

The rubber boa, Charina bottae is a semi-fossorial, cold-temperature adapted snake that ranges across the wetter and cooler ecoregions of the California Floristic Province. The rubber boa is 1 of 2 species in the family Boidae native to California and currently has 2 recognized subspecies, the Northern rubber boa C. bottae bottae and the Southern rubber boa C. bottae umbratica. Recent genomic work on C. bottae indicates that these 2 subspecies are collectively composed of 4 divergent lineages that separated during the late Miocene. Analysis of habitat suitability indicates that C. bottae umbratica montane sky-island populations from southern California will lose the majority of their habit over the next 70 yr, and is listed as Threatened under the California Endangered Species Act. Here, we report a new, chromosome-level assembly of C. bottae bottae as part of the California Conservation Genomics Project (CCGP). Consistent with the reference genome strategy of the CCGP, we used Pacific Biosciences HiFi long reads and Hi-C chromatin-proximity sequencing technology to produce a de novo assembled genome. The assembly comprises 289 scaffolds covering 1,804,944,895 bp, has a contig N50 of 37.3 Mb, a scaffold N50 of 97 Mb, and BUSCO completeness score of 96.3%, and represents the first reference genome for the Boidae snake family. This genome will enable studies of genetic differentiation and connectivity among C. bottae bottae and C. bottae umbratica populations across California and help manage locally endemic lineages as they confront challenges from human-induced climate warming, droughts, and wildfires across California.

Congruence between global crop wild relative hotspots and biodiversity hotspots

Biodiversity is currently experiencing exceptional loss due to the activities of humans, negatively impacting the ecosystem services on which humanity relies. Additionally, human induced climate change is already negatively impacting agriculture worldwide – a trend that will only worsen - leading to reduced yields for some crops and regions. Crop wild relatives (CWR) the wild cousins of domesticated crops, contain a wide breadth of genetic diversity not found in cultivated crops, which can be used for breeding new climate tolerant varieties. However, CWR are under-conserved in the wild, thus jeopardising this resource. Funds for CWR conservation activities are often limited; to conserve efficiently therefore, conservation strategies could prioritise in situ actions in areas of existing biodiversity conservation or protection, so long as CWR diversity overlaps with other components of biodiversity (i.e., other taxa). This analysis examines whether CWR could benefit from being conserved in biodiversity hotspots. Global CWR hotspots were defined from statistically significant spatial clustering of areas of high CWR richness. Biodiversity hotspots had significant overlap with CWR hotspots with the highest coincidence in the Mediterranean basin (91%) and the California Floristic Province (91%). Overall, the Mediterranean basin, Irano-Anatolian, Caucasus and Tropical Andes hotspots showed greatest promise for in situ conservation of CWR, and hence greater efficiency of conservation investments.

A framework linking biogeography and species traits to plant species vulnerability under global change in Mediterranean-type ecosystems

We review the roles that plant species traits and biogeography play in species’ exposure and vulnerability to decline or extinction under global change, focusing on separate and combined impacts of multiple threats – climate change, land-use change, and altered disturbance regimes. We establish a conceptual framework and research agenda for identifying the spatial characteristics of species ranges, as well as the life history and functional traits, that are associated with extinction risk for plant species with functional attributes emblematic of fire-prone, winter-precipitation Mediterranean-type ecosystems (MTEs). MTEs worldwide are characterized by their high plant diversity and unique floras, historical and contemporary high rates of land use change, and strong interactions between climate, fire, and land use. We focus on the California Floristic Province (CFP), an MTE that is a global plant diversity hotspot, and show how our framework can be used to understand the relationships between vulnerability to multiple global change drivers, species traits, and biogeography. Vulnerability can be assessed across species using linked distribution and population models that forecast plant responses to global change scenarios. Our overarching hypothesis is that species-specific vulnerability to global change in MTEs is a function of interactions between species and spatial traits: the nature of this interaction will depend on the type of global change process.

Reference Genome Assembly of the Big Berry Manzanita (Arctostaphylos glauca).

Arctostaphylos (Ericaceae) species, commonly known as manzanitas, are an invaluable fire-adapted chaparral clade in the California Floristic Province (CFP), a world biodiversity hotspot on the west coast of North America. This diverse woody genus includes many rare and/or endangered taxa, and the genus plays essential ecological roles in native ecosystems. Despite their importance in conservation management, and the many ecological and evolutionary studies that have focused on manzanitas, virtually no research has been conducted on the genomics of any manzanita species. Here, we report the first genome assembly of a manzanita species, the widespread Arctostaphylos glauca. Consistent with the genomics strategy of the California Conservation Genomics project, we used Pacific Biosciences HiFi long reads and Hi-C chromatin-proximity sequencing technology to produce a de novo assembled genome. The assembly comprises a total of 271 scaffolds spanning 547Mb, close to the genome size estimated by flow cytometry. This assembly, with a scaffold N50 of 31Mb and BUSCO complete score of 98.2%, will be used as a reference genome for understanding the genetic diversity and the basis of adaptations of both common and rare and endangered manzanita species.

Phylogeography and Genetic Structure in the California Giant Salamander (Dicamptodon ensatus): Impacts of current and historic landscape features.

The California Floristic Province contains numerous ecological regions and a complex geological and geographical history that make it one of the worlds biodiversity hotspots. A number of wide-ranging taxa span across these regions and show complex patterns of dispersal, vicariance and lineage diversification, making localized small ranged species with lower levels of vagility essential to understanding the overall region. Here, we investigate the biogeography and population structure of the California Giant Salamander (Dicamptodon ensatus) (Eschscholtz 1833), an endemic species localized to a narrow coastal region between two areas of biological significance in the California Floristic Province, the North Coast Divide and Monterey Bay. We sequenced one mtDNA fragment (control region) for 133 individuals and a subset of 38 individuals for the anonymous nuclear locus E16C7. We analyzed these sequences with phylogenetic, coalescent, Bayesian clustering, and population genetic approaches in order to infer population structure, phylogenetic structure, and biogeographic history. Additionally, we examined occurrence data with species distribution modeling to generate a habitat suitability map to aid our interpretation of geographic structure. Our analyses recovered 4 major mtDNA lineages, two of which are combined into 3 major lineages when nuDNA is examined. These 3 major lineages are bounded by 4 major current or past geological features; the North Coast Divide, the former Wilson Grove Embayment/current Petaluma Gap, San Francisco Bay, and Monterey Bay. Other low-vagility species linked to moist microclimates and forest habitat do share similarities with the genetic patterns of D. ensatus hinting at a larger role for the past Wilson Grove embayment and modern Petaluma Gap in California biogeography.

LIMITING LIFE HISTORY STAGES IN THE ENDANGERED WETLAND PLANT CIRSIUM HYDROPHILUM VAR. HYDROPHILUM (ASTERACEAE)

In addition to its high biodiversity, the California Floristic Province contains over 1600 rare taxa, including many endemics restricted to specific soil types and habitats. In the highly urbanized San Francisco Estuary, these narrow endemics face additional limitations from habitat destruction and modification, prompting an interest in their conservation and management. One such taxon, the Federally listed Cirsium hydrophilum (Greene) Jeps. var. hydrophilum (Suisun thistle), is restricted to two or three populations, and may face limitations beyond past habitat loss. In this study, we investigated life history limitations that may contribute to rarity in C. hydrophilum var. hydrophilum. We documented low seed set, high seed predation by beetle larvae, low localized wind dispersal of seeds, and possible inbreeding in smaller patches. Because seeds did not have a stringent germination requirement in the lab, however, restoration or introduction of new populations from seed is possible. Using seeds from larger source populations could increase success of reseeding, as could adding seeds to augment potentially low genetic diversity in existing smaller subpopulations. Further study is needed to understand the ecology of seed predators, the relative importance of seed set and seed germination in the field, and to confirm our potential finding of reduced genetic diversity and inbreeding. Though the causes and consequences of rarity may differ for each species, this study explores several research directions that could be productive for understanding other California endemic Cirsium and rare wetland endemics.

A NEW ANNUAL SPECIES OF CHAENACTIS (COMPOSITAE) FROM THE CENTRAL DESERT OF BAJA CALIFORNIA, MEXICO

A new yellow-flowered annual pincushion, Chaenactis kyhosii B.G.Baldwin, is described from the Central Desert of Baja California, Mexico. This desert taxon has been confused with C. glabriuscula DC. sensu lato (s. l.), a species complex of the California Floristic Province and desert periphery. Chaenactis kyhosii (2n = 5II) is evidently allopatric with C. glabriuscula s. l. (2n = 6II) and is distinct chromosomally. It differs morphologically from other yellow-flowered members of Chaenactis, including C. glabriuscula s. l., by the character-state combination of having non-glandular hairs sparse or lacking, main stem branches concentrated at or near base, leaves mostly basal or proximal on stems, leaf blades entire and filiform or once-pinnate with filiform lobes, peduncles and involucres densely glandular, corollas of marginal florets only slightly enlarged, cypselae sparsely white-strigose to ± glabrate, and pappi uniseriate, of four well-developed, generally unequal, and often obtuse scales. Chaenactis kyhosii is more closely related to the white-flowered, primarily desert-dwelling annual C. fremontii A.Gray, also with 2n = 5II, and the southern lineages of C. glabriuscula s. l. than to the northern lineages of C. glabriuscula s. l.