California Native Plant Research Articles

Conservation Genetics of the Endangered Lompoc Yerba Santa (Eriodictyon capitatum Eastw., Namaceae), including Phylogenomic Insights into the Evolution of Eriodictyon.

Eriodictyon capitatum (Namaceae) is a narrowly distributed shrub endemic to western Santa Barbara County, where it is known from only 10 extant California Natural Diversity Database element occurrences (EOs). Owing to low numbers of plants in nature, a limited overall extent, and multiple current threats, E. capitatum is listed as Endangered under the Federal Endangered Species Act and as Rare under the California Native Plant Protection Act. In the present study, high-throughput DNA sequence data were analyzed to investigate genetic diversity within and among all accessible EOs; to determine the extent of genetic isolation among EOs; to examine clonality within EOs; and to examine the taxonomic circumscriptions of E. capitatum, E. altissimum, E. angustifolium, and E. californicum through phylogenomic analysis. Population genetic analyses of E. capitatum reveal a pattern of strong genetic differentiation by location/EO. The clonality assessment shows that certain small EOs may support relatively few multilocus genotypes. The phylogenomic analyses strongly support the present-day taxonomic circumscriptions of both E. altissimum and E. capitatum, showing them to be reciprocally monophyletic and sister with strong support. Taken together, these results paint a picture of an evolutionarily and morphologically distinct species known from relatively few, genetically isolated stations.

A FLORISTIC STUDY OF SWANTON PACIFIC RANCH, SANTA CRUZ COUNTY, CALIFORNIA

The Swanton Pacific Ranch (SPR) is located north of the town of Davenport, in Santa Cruz County, California, and is owned by California Polytechnic State University, San Luis Obispo. SPR is approximately 1295 ha and contains areas of salt marsh, coastal prairie, coastal bluff scrub, northern coastal scrub, riparian forest, redwood forest, mixed evergreen forest, and chaparral. The property extends over an elevational gradient from 0 m to 420 m. In this study, we conducted a floristic inventory at SPR and documented 636 taxa. Between 2017 and 2019 we vouchered 547 taxa with 974 specimens. We were unable to locate 63 taxa that had been previously reported, 27 represented from historic collections and 36 represented by personal observations, but lacking vouchers. We relocated, but did not collect, 26 taxa known from previous collections. Overall, we documented 93 families at SPR, with Asteraceae, Poaceae, and Fabaceae having the most species, respectively. California rare taxa, listed by the California Native Plant Society, made up 2.5% of the flora (n = 18). Locally rare taxa made up 10% of the flora (n = 65). Non-native taxa made up 26% of the flora (n = 169). We vouchered one new taxon for Santa Cruz County, Senecio aphanactis Greene, which has a California Rare Plant Rank of 2B.2; documented a new occurrence of Hesperocyparis abramsiana (C.B.Wolf) Bartel var. abramsiana, a Federally Threatened conifer; and collected a form of Sanicula crassicaulis Poepp. Ex DC that we have published as a distinct variety. Overall, this relatively small coastal ranch contained approximately 10% of the flora of California. The 2020 CZU Lightning Complex Fire burned ca. 90% of SPR within a year of this study being completed. This opens the possibility for this study to be used as a baseline for future studies examining post-fire shifts in plant diversity at a landscape scale.

Floral nectar microbial communities exhibit seasonal shifts associated with extreme heat: Potential implications for climate change and plant-pollinator interactions.

Floral nectar contains vital nutrients for pollinators, including sugars, amino acids, proteins, and secondary compounds. As pollinators forage, they inoculate nectar with bacteria and fungi. These microbes can colonize nectaries and alter nectar properties, including volume and chemistry. Abiotic factors, such as temperature, can influence microbial community structure and nectar traits. Considering current climate change conditions, studying the effects of increased temperature on ecosystem processes like pollination is ever more important. In a manipulative field experiment, we used a passive-heating technique to increase the ambient temperature of a California native plant, Penstemon heterophyllus, to test the hypothesis that temperatures elevated an average of 0.5°C will affect nectar properties and nectar-inhabiting microbial communities. We found that passive-heat treatment did not affect nectar properties or microbial communities. Penstemon heterophyllus fruit set also was not affected by passive-heat treatments, and neither was capsule mass, however plants subjected to heat treatments produced significantly more seeds than control. Although we conducted pollinator surveys, no pollinators were recorded for the duration of our experiment. A naturally occurring extreme temperature event did, however, have large effects on nectar sugars and nectar-inhabiting microbial communities. The initially dominant Lactobacillus sp. was replaced by Sediminibacterium, while Mesorhizobium, and Acinetobacter persisted suggesting that extreme temperatures can interrupt nectar microbiome community assembly. Our study indicates that the quality and attractiveness of nectar under climate change conditions could have implications on plant-pollinator interactions.

Infrastructuring Gardens: The Material Politics of Outdoor Water Conservation in Los Angeles

Historically, urban developers, politicians, and public water utilities have invented Los Angeles as a semitropical oasis in a dry climate. During the California drought of 2011 through 2016, however, the city’s residential gardens became a new frontier of water conservation policy. Water agencies started to subsidize the replacement of lushly irrigated lawns with California Friendly® landscapes, thereby endorsing a technology-centered “infrastructuring” of gardens to increase water conservation. This approach contrasts with California native plant gardening promoted by nature conservationists, which uses vernacular horticultural techniques to restore native plant biodiversity and reduce irrigation. The article shows that each approach has important political implications for urban space and water use, the value accorded to nature and gardening work, and relations between citizens and experts. Analyzing the differences between these approaches, we critically interrogate Los Angeles’s modern infrastructure regime that shapes water conservation policy. Particular attention is paid to how new material objects, knowledges, and practices in gardening recompose relationships between water, plants, technology, humans, and urban space. We argue that the notion of infrastructuring gardens offers a fruitful lens for ascertaining how expert cultures shape urban environmental change and how alternative gardening practices (re)produce urban nature differently.

Get to know Your Environment: Medicinal California Native Plants

Get to know Your Environment: Medicinal California Native Plants

Testing an invasion mechanism for Eucalyptus globulus: Is there evidence of allelopathy?

Sparse understory communities, in association with non-native tree species, are often attributed to allelopathy, the chemical inhibition of a plant by another. However, allelopathy is a difficult ecological phenomenon to demonstrate as many studies show conflicting results. Eucalyptus globulus, a tree native to Australia, is one of the most widely planted trees around the world. Sparse understories are common beneath E. globulus plantations and are often attributed to allelopathy, but the ecological impacts of E. globulus on native plant communities outside Austrialia are poorly understood. To assess allelopathy as a mechanism of understory inhibition, we tested volatile- and water-soluble leaf extracts from E. globulus, Salvia apiana, and Quercus agrifolia on seed germination of California native plants. We also quantified germination rates and early seedling growth of California native plants grown in soil from E. globulus plantations versus soil from an adjacent native plant community. Volatile compounds from E. globulus did not significantly reduce germination for any species. Inhibition from water-soluble E. globulus compounds was comparable to that of a native tree, Quercus agrifolia (10%). Eucalyptus globulus soil supported germination and early seedling growth of native species equal to or better than coastal scrub soil, although species responses were variable. In contrast to previous studies, our results fail to support the hypothesis that E. globulus chemically inhibits germination of native species. California native plants germinate and grow well in soils from E. globulus plantations, which may have significant implications for management and restoration of land historically occupied by E. globulus plantations.

List of Bryophytes Collected in the Northern Last Chance Range and Eureka Valley, Death Valley National Park

A list of bryophytes occurring naturally in northern Death Valley National Park is presented. So far, 41 taxa have been documented, representing seven families and 24 genera. One species, Jaffueliobryum wrightii, is considered rare by the California Native Plant Society.

Microbes, mutualism, and range margins: testing the fitness consequences of soil microbial communities across and beyond a native plant's range.

Interactions between plants and soil fungi and bacteria are ubiquitous and have large effects on individual plant fitness. However, the degree to which spatial variation in soil microbial communities modulates plant species' distributions remains largely untested. Using the California native plant Clarkia xantiana ssp. xantiana we paired glasshouse and field reciprocal transplants of plant populations and soils to test whether plant-microbe interactions affect the plant's geographic range limit and whether there is local adaptation between plants and soil microbe communities. In the field and glasshouse, one of the two range interior inocula had a positive effect on plant fitness. In the field, this benefit was especially pronounced at the range edge and beyond, suggesting possible mutualist limitation. In the glasshouse, soil inocula from beyond-range tended to increase plant growth, suggesting microbial enemy release beyond the range margin. Amplicon sequencing revealed stark variation in microbial communities across the range boundary. Plants dispersing beyond their range limit are likely to encounter novel microbial communities. In C.x.xantiana, our results suggest that range expansion may be facilitated by fewer pathogens, but could also be hindered by a lack of mutualists. Both negative and positive plant-microbe interactions will likely affect contemporary range shifts.

Phytophthora Introductions in Restoration Areas: Responding to Protect California Native Flora from Human-Assisted Pathogen Spread

Over the past several years, plantings of California native plant nursery stock in restoration areas have become recognized as a pathway for invasive species introductions, in particular Phytophthora pathogens, including first in the U.S. detections (Phytophthora tentaculata, Phytophthora quercina), new taxa, new hybrid species, and dozens of other soilborne species. Restoration plantings may be conducted in high-value and limited habitats to sustain or re-establish rare plant populations. Once established, Phytophthora pathogens infest the site and are very difficult to eradicate or manage—they degrade the natural resources the plantings were intended to enhance. To respond to unintended Phytophthora introductions, vegetation ecologists took a variety of measures to prevent pathogen introduction and spread, including treating infested areas by solarization, suspending plantings, switching to direct seeding, applying stringent phytosanitation requirements on contracted nursery stock, and building their own nursery for clean plant production. These individual or collective actions, loosely coordinated by the Phytophthoras in Native Habitats Work Group ensued as demands intensified for protection from the inadvertent purchase of infected plants from commercial native plant nurseries. Regulation and management of the dozens of Phytophthora species and scores of plant hosts present a challenge to the state, county, and federal agriculture officials and to the ornamental and restoration nursery industries. To rebuild confidence in the health of restoration nursery stock and prevent further Phytophthora introductions, a voluntary, statewide accreditation pilot project is underway which, upon completion of validation, is planned for statewide implementation.

Remembering Lee W. Lenz (1915–2019)

Known primarily for his systematic work on Iris, Dr. Lee Lenz was also known for his taxonomic revision in other monocotyledonous groups such as Yucca, leading to his recognition of Yucca jaegeriana as distinct from the Joshua tree, Y. brevifolia. He was also involved in breeding horticultural forms from California native plants, such as xChiranthofremontia lenzii, and was credited with developing the first red-flowering iris within the Pacific Coast hybrids. Dr. Lenz was Director of Rancho Santa Ana Botanic Garden (now California Botanic Garden) in Claremont, California, from 1960 to 1983. A table lists his articles and Director's Reports published in Aliso between 1950 and 2007.

Drought‐Net rainfall shelters did not cause nondrought effects on photosynthesis for California central coast plants

AbstractRainfall interception shelters are frequently used to study the ecological consequences of drought. One common shelter design employs V‐shaped plastic troughs spaced on a supporting frame to intercept rainfall. Shading, reflection, and infrared radiation may alter the radiative environment under shelters in ways independent of their intended effect on soil moisture. We measured microclimate and several photosynthetic variables for watered, potted plants under rain‐out shelters and in open‐air, unsheltered plots. We tested whether the shelter infrastructure altered aboveground micrometeorology and photosynthesis for watered, potted plants of native Californian species: Elymus glaucus, Eriogonum latifolium, Mimulus aurantiacus, and Morella californica. We quantified the effects on photosynthesis in terms of light harvesting by photosystem II (PSII) and leaf‐level gas exchange on open‐air and shelter plots, the quantum yield of PSII for darkened leaves, dark respiration, and nocturnal stomatal conductance. The rain‐out shelter reduced daily integrated photosynthetically active radiation by 20%. Air temperature, leaf temperature, and leaf‐to‐air vapour pressure difference were not different under shelters compared with controls during the day. Likewise, there were no effects of shelters on net CO2 assimilation, stomatal conductance to water vapour (gs), internal leaf (CO2), or electron transport rate through PSII during the daytime. At night, Tair was 0.6°C higher under shelters, but there were no effects on dark respiration or stomatal conductance. Despite some differences in micrometeorology under rain‐out shelters compared with open‐air plots, there were little or no aboveground nondrought effects of the shelters on leaf‐level photosynthesis for watered, potted plants of these California native plant species.

Phytophthora Species Are Common on Nursery Stock Grown for Restoration and Revegetation Purposes in California.

Phytophthora tentaculata was detected for the first time in North America in 2012 in a nursery on sticky monkeyflower plant (Diplacus aurantiacus) and again in 2014 on outplanted native plants. At that time, this species was listed as a federally actionable and reportable pathogen by the USDA. As a result of these detections, California native plant nurseries were surveyed to determine the prevalence of Phytophthora species on native plant nursery stock. A total of 402 samples were collected from 26 different native plant nurseries in California between 2014 and 2016. Sampling focused on plants with symptoms of root and crown rot. Symptomatic tissue was collected and tested by immunoassay, culture, and molecular techniques (PCR). Identifications were made using sequences from the internal transcribed spacer (ITS) rDNA region, a portion of the trnM-trnP-trnM, or the atp9-nad9 mitochondrial regions. Phytophthora was confirmed from 149 of the 402 samples (37%), and from plants in 22 different host families. P. tentaculata was the most frequently detected species in our survey, followed by P. cactorum and members of the P. cryptogea complex. Other species include P. cambivora, P. cinnamomi, P. citricola, P. hedraiandra, P. megasperma, P. multivora, P. nicotianae, P. niederhauserii, P. parvispora, P. pini, P. plurivora, and P. riparia. A few Phytophthora sequences generated from mitochondrial regions could not be assigned to a species. Although this survey was limited to a relatively small number of California native plant nurseries, Phytophthora species were detected from three quarters of them (77%). In addition to sticky monkeyflower, P. tentaculata was detected from seven other hosts, expanding the number of associated hosts. During this survey, P. parvispora was detected for the first time in North America from symptomatic crowns and roots of the nonnative Mexican orange blossom (Choisya ternata). Pathogenicity of P. parvispora and P. nicotianae was confirmed on this host. These findings document the widespread occurrence of Phytophthora spp. in native plant nurseries and highlight the potential risks associated with outplanting infested nursery-grown stock into residential gardens and wildlands.

Identifying native plants for coordinated habitat management of arthropod pollinators, herbivores and natural enemies

Abstract Providing noncrop flowering resources in agricultural landscapes is widely promoted as a strategy to support arthropods that deliver pollination and pest control services. However, management options have largely been developed separately for pollinators and natural enemies, whereas possible effects on insect herbivores, such as crop pests, have often been overlooked. A first critical step for design and implementation of multifunctional plantings that promote beneficial arthropods while controlling insect pests is to identify suitable plant species to use. We aimed to identify California native plants and, more generally, plant traits suitable for the coordinated management of pollinators (wild bees and honeybees), insect herbivores and arthropod natural enemies (predators and parasitic wasps). We established 43 plant species in a common garden experiment and sampled arthropods by weekly netting (wild bees), observations (honeybees), or vacuum sampling (insect herbivores, arthropod predators, and parasitic wasps) during peak bloom of each plant species over 2 years. Plant species differed in attractiveness for each arthropod functional group. Floral area of the focal plant species positively affected honeybee, predator, and parasitic wasp attractiveness. Later bloom period was associated with lower numbers of parasitic wasps. Flower type (actinomorphic, composite, or zygomorphic) predicted attractiveness for honeybees, which preferred actinomorphic over composite flowers and for parasitic wasps, which preferred composite flowers over actinomorphic flowers. Across plant species, herbivore, predator, and parasitic wasp abundances were positively correlated, and honeybee abundance correlated negatively to herbivore abundance. Synthesis and applications. We use data from our common garden experiment to inform evidence‐based selection of plants that support pollinators and natural enemies without enhancing potential pests. We recommend selecting plant species with a high floral area per ground area unit, as this metric predicts the abundances of several groups of beneficial arthropods. Multiple correlations between functionally important arthropod groups across plant species stress the importance of a multifunctional approach to arthropod habitat management.

Soil- and waterbornePhytophthoraspecies linked to recent outbreaks in Northern California restoration sites

Many studies around the globe have identified plant production facilities as major sources of plant pathogens that may be released in the wild, with significant consequences for the health and integrity of natural ecosystems. Recently, a large number of soilborne and waterborne species belonging to the plant pathogenic genus Phytophthora have been identified for the first time in California native plant production facilities, including those focused on the production of plant stock used in ecological restoration efforts. Additionally, the same Phytophthora species present in production facilities have often been identified in failing restoration projects, further endangering plant species already threatened or endangered. To our knowledge, the identification of Phytophthora species in restoration areas and in plant production facilities that produce plant stock for restoration projects is a novel discovery that finds many land managers unprepared, due to a lack of previous experience with these pathogens. This review summarizes some of the key knowledge about the genus Phytophthora in general and lists some of the many soilborne and waterborne species recently recovered from some California restoration sites and plant production facilities.

Clarifying the Conservation Status of Northern California Black Walnut (Juglans hindsii) Using Microsatellite Markers

The conservation status of the northern California black walnut (Juglans hindsii (Jeps.) Jeps. ex R. E. Sm.) has been a source of considerable confusion and controversy. Although not currently legally protected by either Federal or State Endangered Species Acts, this species is given conservation status by the California Native Plant Society and the California Department of Fish and Wildlife, and some California counties require mitigation for removal of individuals of this species, especially older trees. Despite the current widespread distribution in northern California and southern Oregon of trees that match J. hindsii morphologically, there are only three or four sites where the species is known to have occurred prior to extensive settlement of California by Europeans in the mid-19th century. This has led to the suspicion that trees found in other places may not be genetically pure J. hindsii but may instead be descendants of lineages that experienced past gene flow from one or more other species. In addition, despite its more distant relationship, the cultivated walnut (J. regia L.) readily hybridizes (as the male parent) with J. hindsii, producing morphologically identifiable ‘Paradox' hybrids, which occur spontaneously and are widely planted as rootstocks and street trees. Finally, recent collections of J. hindsii from southern California have raised questions about the respective geographic distributions of J. hindsii and southern California black walnut (J. californica S. Watson). We analyzed genotypes at 10 microsatellite loci for 158 mostly wild J. hindsii trees, as well as some orchard waifs, from 10 counties in northern and southern California and one county in southern Oregon, including representatives of putative original native populations. We also sampled several Paradox hybrids, 10-20 standards for each of the five North American black walnut species, and six standards for J. regia. Bayesian cluster analyses with the program STRUCTURE revealed that at least 71.5% of the putatively wild J. hindsii represent genetically pure members of that species, while the remaining trees show evidence of past hybridizations with one or more of the other North American black walnut species. We found no evidence of introgression of J. regia into J. hindsii. The results suggest that individual J. hindsii trees should not have conservation status.

Natural, Manmade Treasures Abound at Balboa Park

Natural, Manmade Treasures Abound at Balboa Park

A Checklist of the Bryophytes of the California Channel Islands

Abstract An annotated, vouchered checklist of the bryophytes of the California Channel Islands is presented, including the known distribution of each species across the eight islands. The bryoflora currently comprises 158 minimally ranked taxa. Fifty-nine mosses, two hornworts, and twenty-two liverworts are reported for the first time from the islands. Fifteen species previously reported from the archipelago are excluded based on new determinations and nomenclatural changes. The bryoflora includes two putative undescribed species in the Bryaceae, Plagiobryoides sp. from Santa Catalina Island and Gemmabryum sp. from Santa Rosa Island. Excluding these two putative new species, no new state records are reported. One species, Tortula californica, is listed by the California Native Plant Society at the 1B rank. Previous reports from the literature are catalogued and nomenclatural changes are noted. There are no island endemics, with the possible exception of the two putative undescribed species. The bryoflora ...

Improving nursery production of fifteen California native plant species: the effect of air-filled porosity

Many studies have shown the importance of air-filled porosity (VA ) for optimal growth and dry weight of container-grown plants, but few have examined its effects on California native plants. Anecdotal evidence suggests that various upland native species require higher substrate aeration or less frequent irrigation than do standard nursery crops. We tested effects of VA and irrigation frequency on 15 California native species that had been identified by growers as challenging because of their aeration needs and sensitivity to overwatering. Plants were grown in substrates with 10% or 22% VA and were irrigated once (up to 574 ml) or twice daily (up to total of 972 ml). None of the applied treatments preferentially influenced plant survival or growth. Results indicate that these species may tolerate both normal and high VA values. The high survival and growth rates in these experiments indicate that growers’ experiences of plant death or poor plant growth are attributable to something other than VA .

CITY OF HAWTHORNE OCEAN FRIENDLY GARDEN DEMONSTRATION PROJECT

INTRODUCTION A comprehensive approach to reducing landscape water use was implemented in the Demonstration Garden in the City of Hawthorne. By creating healthy soil, grading to capture and retain rainwater, using California native and climate-appropriate plants, and implementing sustainable maintenance practices, the garden was designed to mimic the natural processes of a mini-watershed. The soil is now able to soak up and retain rainwater, reducing the need for supplemental irrigation and eliminating urban runoff. Habitat and food for wildlife was introduced, and maintenance costs were minimized by reducing green waste and eliminating the need for chemical fertilizers, herbicides, and pesticides. The installation was supplemented by two classes offered free to the public: a three hour introduction to California Friendly Landscaping principles, and a half day hands-on workshop in which participants used their newly-acquired knowledge to plant California natives and install drip irrigation. California nati...

Use of a hybrid optical remote sensing classification technique for seasonal wetland habitat degradation assessment resulting from adoption of real-time salinity management practices

Delayed seasonal wetland drawdown is being investigated as one means of improving the scheduling of saline drainage discharge to the San Joaquin River, California, as an application of the principal of basin-scale real-time salinity management. A hybrid rapid vegetation assessment methodology was derived from the California Native Plant Society Rapid Assessment Protocol for classifying the vegetation in these seasonal wetlands. A hybrid remote sensing methodology combining pixel- and object-based components was developed to apply this classification strategy to a 160 km2 region. Twenty-six different plant communities were represented in a total of 20 land cover classes. An overall mapping accuracy ranges from 60% for identification of all 26 plant communities to 100% for identification of a single plant species. Low representation of certain associations for sensor calibration resulted in lower than anticipated mapping success as measured by errors of omission and commission. This image processing methodology provides an important tool, in concert with soil salinity mapping and wetland biology surveys, to assess the long-term impact of adaptive management strategies such as real-time salinity management on the wetland resource.