Photo Credit: USFWS: John Martin
Goal: Maintain large populations, enhance small populations, and establish new populations of San Diego thornmint or pollinator habitat to buffer against environmental stochasticity, maintain genetic diversity, and promote connectivity, thereby enhancing resilience within and among MUs over the long-term (>100 years) in native habitats.
Management units: 3, 4, 5, 6
Starting in 2017, reduce the potential impact of fire for at risk large populations of San Diego thornmint (see occurrence table) by reducing fuel loads of invasive annuals
| Action | Statement | Action status | Projects |
|---|---|---|---|
| IMP-1 | Manage thatch and invasive annuals every 3-5 years to reduce fire threat for populations of San Diego thornmint most at risk of fire (populations with ignition probability or fire frequency > 3 or that have burned since 2003) | available for implementation | |
| IMP-2 | Submit project metadata, monitoring datasets and report with management actions to the MSP Web Portal. | waiting for precedent action |
| Criteria | Deadline year |
|---|---|
| Fuel Loads and Invasive Grasses Reduced for at Risk Populations | 2021 |
| Threat Name | Threat Code |
|---|---|
| Altered fire regime | ALTFIR |
| Human uses of the Preserves | HUMUSE |
| Invasive plants | INVPLA |
| Loss of connectivity | LOSCON |
| Urban development | URBDEV |
Management units: 3, 4, 5, 6
Beginning in 2017, annually inspect conserved populations of San Diego thornmint (see occurrence table) using the regional rare plant IMG monitoring protocol to record abundance and collect covariate habitat and threats data to determine management needs.
| Action | Statement | Action status | Projects |
|---|---|---|---|
| IMP-1 | Based upon occurrence status and threats, determine management needs including whether routine management or more intensive management is warranted. | some occurrences are in progress | |
| IMP-2 | Submit project metadata, occurrence status, habitat and threats data, and management recommendations to the MSP Web Portal. | some occurrences are in progress |
| Criteria | Deadline year |
|---|---|
| Surveys Completed Annually with Management Recommendations | 2021 |
| Threat Name | Threat Code |
|---|---|
| Altered fire regime | ALTFIR |
| Human uses of the Preserves | HUMUSE |
| Invasive plants | INVPLA |
| Urban development | URBDEV |
Management units: 3, 4, 5, 6
Beginning in 2017, conduct routine management actions identified through the IMG monitoring at San Diego thornmint occurrences on Conserved Lands (see occurrence table). Depending on the type and level of threat, management should only be conducted as needed, not necessarily every year, and using BMPs with precautions to do no harm.
| Action | Statement | Action status | Projects |
|---|---|---|---|
| IMP-1 | Perform routine management activities as needed, such as protecting occurrences from disturbance through enforcement and controlling invasive non-native plant species to =20% absolute cover. | available for implementation | San Diego Thornmint Restoration |
| IMP-2 | Submit project metadata and management data to MSP web portal. | available for implementation | San Diego Thornmint Restoration |
| Criteria | Deadline year |
|---|---|
| Routine Management Completed as Needed Based Upon Monitoring Recommendations | 2021 |
| Threat Name | Threat Code |
|---|---|
| Altered fire regime | ALTFIR |
| Human uses of the Preserves | HUMUSE |
| Invasive plants | INVPLA |
| Urban development | URBDEV |
Management units: 3, 4, 5, 6
In 2017, continue refining BMPs developed for San Diego thornmint (CBI 2014) by incorporating results of management experiments to control invasive species that threaten populations (e.g., Brachypodium removal studies at Mission Trails and South Crest) and based on research studies (e.g., seed bulking guidelines, seed transfer zones).
| Action | Statement | Action status | Projects |
|---|---|---|---|
| DEV-1 | Refine BMPs prepared by CBI in the San Diego Thornmint Adaptive Management Framework (2014) by incorporating results of management experiments to control invasive species that threaten populations (e.g., Brachypodium removal and South County Grasslands projects) and based on research studies (e.g., seed bulking guidelines, seed transfer) | In progress | |
| DEV-2 | Submit project metadata, management datasets and BMP report to MSP web portal. | In progress |
| Criteria | Deadline year |
|---|---|
| BMPs for San Diego Thornmint Prepared by 2018 | 2021 |
| Threat Name | Threat Code |
|---|---|
| Altered fire regime | ALTFIR |
| Human uses of the Preserves | HUMUSE |
| Invasive plants | INVPLA |
| Loss of connectivity | LOSCON |
| Urban development | URBDEV |
Management units: 3, 4, 5, 6
In 2017, continue a study begun in 2016 to characterize the population genetic structure, gene flow, and genetic diversity for San Diego thornmint occurrences (see occurrence table). The study will determine if there is evidence of mixed ploidy levels within or among occurrences; evaluate vulnerability of occurrences to genetic drift and loss of genetic diversity; assess the level of gene flow among occurrences; identify if there are signatures of genetic bottlenecks or low genetic diversity in occurrences that have undergone recent reductions; and look for evidence of local population adaptation. Based on the results of the genetic analyses, management recommendations will include whether common garden and reciprocal transplantations are necessary before proceeding with population enhancement or restoration and will provide specific recommendations for collecting, bulking and distributing seed to enhance existing occurrences or establish new occurrences.
| Action | Statement | Action status | Projects |
|---|---|---|---|
| RES-1 | Use BMPs to collect plant material for genetic samples at San Diego thornmint occurrences on Conserved lands in the MSPA. | in progress | |
| RES-2 | Evaluate the overall long-term genetic trajectory for San Diego thornmint. | in progress | |
| RES-3 | Hold a workshop of scientists, rare plant experts, and land managers to develop management recommendations based upon the results of genetic analyses. | in progress | |
| RES-4 | Submit project metadata, genetic datasets and analyses, and report with management recommendations to the MSP Web Portal. | in progress | |
| RES-4 | Submit project metadata, genetic datasets and analyses, and report with management recommendations to the MSP Web Portal. | in progress |
| Criteria | Deadline year |
|---|---|
| By 2017, Completed Genetic Study for San Diego Thornmint | 2021 |
| Threat Name | Threat Code |
|---|---|
| Loss of connectivity | LOSCON |
Management units: 3, 4, 5, 6
In 2018, begin preparing a section for San Diego thornmint the MSP Rare Plant Management Plan that prioritizes management actions to maintain or expand occurrences on Conserved Lands based upon an assessment of data on occurrence status, habitat and threats. Prioritize management recommendations to maintain large occurrences and enhance at least 3 small occurrences (see occurrence table). Minimum criteria for enhancement are to reduce invasive annual nonnative plants and thatch to less than 20% absolute cover within the occurrence
| Action | Statement | Action status | Projects |
|---|---|---|---|
| PRP-1 | Consult the San Diego County Rare Plant Working Group made up of plant ecologists, geneticists, rare plant experts, land managers, restoration practitioners, seed banking and bulking practitioners, wildlife agencies, and other stakeholders to provide input and recommendations for the San Diego thornmint section in the MSP Rare Plant Management Plan. | waiting for precedent action | |
| PRP-2 | Develop a conceptual model that identifies management actions to effectively reduce threats to San Diego thornmint occurrences. | waiting for precedent action | |
| PRP-3 | Prioritize occurrences for management based upon an assessment of occurrence size, the potential for management to significantly reduce identified threats, and the availability of adjacent suitable habitat for occurrence expansion. | waiting for precedent action | |
| PRP-4 | Develop an implementation plan for San Diego thornmint that prioritizes management actions for the next 5 years and details tasks, lead entities, responsibilities, and timelines, budgets. | waiting for precedent action | |
| PRP-5 | Submit project metadata and MSP Rare Plant Management Plan to the MSP Web Portal. | waiting for precedent action |
| Criteria | Deadline year |
|---|---|
| By 2019 Completed Section for San Diego Thornmint in the MSP Rare Plant Management Plan. | 2021 |
| Threat Name | Threat Code |
|---|---|
| Altered fire regime | ALTFIR |
| Climate change | CLICHN |
| Human uses of the Preserves | HUMUSE |
| Invasive plants | INVPLA |
| Loss of connectivity | LOSCON |
| Urban development | URBDEV |
Management units: 3, 4, 5, 6
In 2019, begin implementing highest priority management actions identified for San Diego thornmint in the MSP Rare Plant Management Plan.
| Action | Statement | Action status | Projects |
|---|---|---|---|
| IMP-1 | Submit project metadata, management datasets, and report to the MSP Web Portal. | waiting for precedent action |
| Criteria | Deadline year |
|---|---|
| By 2023, =2 High Priority Management Actions Implemented for San Diego Thornmint from the MSP Rare Plant Management Plan | 2021 |
| Threat Name | Threat Code |
|---|---|
| Altered fire regime | ALTFIR |
| Climate change | CLICHN |
| Human uses of the Preserves | HUMUSE |
| Invasive plants | INVPLA |
| Loss of connectivity | LOSCON |
| Urban development | URBDEV |
Management units: 3, 4, 5, 6
In 2019, begin monitoring the effectiveness of implementation of the highest priority management actions identified in the San Diego thornmint section of the MSP Rare Plant Management Plan.
| Action | Statement | Action status | Projects |
|---|---|---|---|
| IMP-1 | Submit metadata, management effectiveness datasets, analyses, and report to the MSP Web Portal. | waiting for precedent action |
| Criteria | Deadline year |
|---|---|
| Effectiveness of High Priority Management Actions Determined | 2021 |
| Threat Name | Threat Code |
|---|---|
| Altered fire regime | ALTFIR |
| Climate change | CLICHN |
| Human uses of the Preserves | HUMUSE |
| Invasive plants | INVPLA |
| Loss of connectivity | LOSCON |
| Urban development | URBDEV |
Management units: 3, 4, 5, 6
In 2018, begin preparing a section for San Diego thornmint in the MSP Seed Collection, Banking and Bulking Plan to preserve genetic diversity and rescue occurrences in case of catastrophic disturbance. The plan should incorporate best science and management practices (Wall 2009, KEW 2016) and recommendations from the 2016-2017 genetic study to provide guidelines for collecting and storing seeds over the long term at a permanent, established conservation seed bank (e.g., Institute for Conservation Research Native Plant Seed Bank, Rancho Santa Ana Botanic Garden Seed Conservation Program) and for providing sources of seeds for management purposes. The plan should include recommendations for: collecting and storing seeds for conservation banking; management oriented research; rescuing occurrences after catastrophic disturbances; and seed bulking and out-planting to augment extant occurrences or to establish new occurrences with consideration of genetic implications for population sustainability.
| Action | Statement | Action status | Projects |
|---|---|---|---|
| PRP-1 | Consult the San Diego County Rare Plant Working Group made up of plant ecologists, geneticists, rare plant experts, land managers, restoration practitioners, seed banking and bulking practitioners, wildlife agencies, and other stakeholders to provide input and recommendations for the San Diego thornmint section of the MSP Seed Collection, Banking and Bulking Plan. | waiting for precedent action | California Plant Rescue (CaPR) - San Diego Zoo Wildlife Alliance's Native Plant Seed Bank |
| PRP-2 | Prepare a seed collection plan to collect seeds over multiple years, collect seeds several times within a season, accumulate seeds across populations, and to sample among habitats and ecological niches. Include guidelines for collecting and storing seeds along maternal lines from small occurrences (<1,000 plants) and to provide propagules to be used in management experiments, enhancement of existing occurrences, and establishment of new occurrences. | waiting for precedent action | California Plant Rescue (CaPR) - San Diego Zoo Wildlife Alliance's Native Plant Seed Bank |
| PRP-3 | The seed collection plan should include guidelines for collecting seeds from occurrences of sufficient size to accommodate harvest and based on genetic studies as available. Include provisions for collecting seed from unconserved populations planned for development. | waiting for precedent action | California Plant Rescue (CaPR) - San Diego Zoo Wildlife Alliance's Native Plant Seed Bank |
| PRP-4 | Include protocols and guidelines for collecting voucher specimens and submitting to the San Diego Natural History Museum (McEachern et al. 2007). | waiting for precedent action | California Plant Rescue (CaPR) - San Diego Zoo Wildlife Alliance's Native Plant Seed Bank |
| PRP-5 | Include guidelines for testing seeds for viability and to obtain information on dormancy and germination rates. | waiting for precedent action | California Plant Rescue (CaPR) - San Diego Zoo Wildlife Alliance's Native Plant Seed Bank |
| PRP-6 | Submit project metadata and MSP Seed Collection, Banking and Bulking Plan to MSP Web Portal. | waiting for precedent action | California Plant Rescue (CaPR) - San Diego Zoo Wildlife Alliance's Native Plant Seed Bank |
| Criteria | Deadline year |
|---|---|
| By 2019, Completed Section for San Diego thornmint in the MSP Seed Collection Banking and Bulking Plan | 2021 |
| Threat Name | Threat Code |
|---|---|
| Altered fire regime | ALTFIR |
| Climate change | CLICHN |
| Human uses of the Preserves | HUMUSE |
| Invasive plants | INVPLA |
| Loss of connectivity | LOSCON |
| Urban development | URBDEV |
Management units: 3, 4, 5, 6
In 2019, begin implementing the MSP Seed Collection, Banking and Bulking Plan for San Diego thornmint to collect and store seeds at a permanent seed bank and to provide propagules as needed for management oriented research, existing population enhancement and establishment of new occurrences.
| Action | Statement | Action status | Projects |
|---|---|---|---|
| IMP-1 | Bulk seed at a qualified facility for enhancement, expansion, establishment or transplantation projects using seed from genetically appropriate donor accessions in the propagation seed bank collection. | waiting for precedent action | California Plant Rescue (CaPR) - San Diego Zoo Wildlife Alliance's Native Plant Seed Bank |
| IMP-2 | Maintain records for collected seed to document donor and receptor sites, collection dates and amounts. Submit seed collection, storage and bulking data to the MSP Web Portal. | waiting for precedent action | California Plant Rescue (CaPR) - San Diego Zoo Wildlife Alliance's Native Plant Seed Bank |
| Criteria | Deadline year |
|---|---|
| By 2023, =2 Highest Priority Actions Implemented for San Diego thornmint from the MSP Seed Banking and Bulking Plan | 2021 |
| Threat Name | Threat Code |
|---|---|
| Altered fire regime | ALTFIR |
| Climate change | CLICHN |
| Human uses of the Preserves | HUMUSE |
| Invasive plants | INVPLA |
| Loss of connectivity | LOSCON |
| Urban development | URBDEV |
Management units: 3, 4, 5, 6
In 2017, continue field research into soils and habitat relationships and development of habitat suitability and climate change models for San Diego thornmint and other edaphic endemic plants to better understand habitat requirements and to identify and prioritize geographic areas important for connectivity, restoration, and range shifts due to climate change and other threats.
| Action | Statement | Action status | Projects |
|---|---|---|---|
| RES-1 | Test soils at potential expansion sites and compare to occupied reference sites to determine site suitability based on soils. | In progress | Enhancing the Resilience of Edaphic Endemic Plants |
| RES-2 | Prepare habitat suitability models under current environmental conditions and for different scenarios of climate change to delineate potential future habitat. | In progress | Enhancing the Resilience of Edaphic Endemic Plants |
| RES-3 | Collect covariate data on vegetation composition and cover (alliance and association-level mapping), soils, invasive plants and other threats for selected populations. | In progress | Enhancing the Resilience of Edaphic Endemic Plants |
| RES-4 | Prioritize locations for conservation, management, and future surveys based on predicted distributions and environmental correlates. | In progress | Enhancing the Resilience of Edaphic Endemic Plants |
| RES-5 | Submit project metadata, monitoring data and report to MSP web portal. | In progress | Enhancing the Resilience of Edaphic Endemic Plants |
| Criteria | Deadline year |
|---|---|
| Refined Models and Prioritized Future Survey Locations for San Diego Thornmint by 2018 | 2021 |
| Threat Name | Threat Code |
|---|---|
| Altered fire regime | ALTFIR |
| Climate change | CLICHN |
| Human uses of the Preserves | HUMUSE |
| Invasive plants | INVPLA |
| Loss of connectivity | LOSCON |
| Urban development | URBDEV |
| Metric | Condition | Trend | Confidence |
|---|---|---|---|
1. Conserved OccurrencesNumber of known, extant occurrences on conserved lands |
Good |
Improving |
Moderate |
2. Population StatusNumber of occurrences increasing in size over time |
Caution |
No Change |
Moderate |
3. Threats to OccurrencesPercent of occurrences with significant threats |
Concern |
No Change |
High |
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Brachypodium Control - Phase I and II
This project used a science-based, experimental approach to develop treatment and restoration
strategies for the emerging invasive grass, Brachypodium distachyon (Brachypodium), on
conserved lands in southern San Diego County, CA. Phase I (2013-2015) included conceptual
models to inform experimentally-based treatment and restoration strategies; experimental
treatments (dethatching, herbicide, mechanical removal), monitoring, and seed collection,
bulking, and outplanting. Treatments continued in Phase II (2016-2017), using the most
effective management strategy (herbicide). See the Phase I and II reports for study results and
Best Management Practices (BMPs) for Brachypodium control. Herbicide is the most effective
treatment for controlling Brachypodium but timing of treatment is critical and multiple
treatments may be required in a single year, depending on rainfall and temperature. Herbicide
treatment of forbs becomes increasingly important as cover of Brachypodium and other
nonnative grasses decrease. Dethatching improves treatment effectiveness and stimulates the
soil seedbank (if present). The experimental design was coordinated with SDMMP and the City
of San Diego, and results may contribute to a regional analysis of Brachypodium control across
multiple sites, habitats, and microclimates.
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Covered and Invasive Species Management: Crestridge Ecological Reserve and South Crest Properties
This was a two year, TransNet-funded study (#5001586) on Crestridge Ecological Reserve and South Crest properties. Both properties support MSCP covered species and sensitive habitats, and function as critical landscape linkages between the northern and southern MSCP. Surrounded by residential development and heavily impacted by the 2003 Cedar Fire, these properties are subject to ongoing invasive plant issues. Specific task actions included invasive plant and covered plant species mapping and risk assessment s, invasive plant control and experimental studies, and development of an early detection invasive control plan.
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Enhancing the Resilience of Edaphic Endemic Plants
The Management Strategic Plan for San Diego County requires prioritization and management for edaphic endemic plants, including the five rare plants addressed in this study. These species face low genetic diversity due to reduced population sizes, geographic isolation, and loss of pollinators. To enhance the resilience of these species across their ranges, we must manage threats to increase population sizes, identify potentially suitable habitat to connect existing populations, find or restore new populations, and provide opportunities for shifting distributions due to climate change.
This study identifies and describes geographic areas that support the five edaphic endemic species and their habitat in a design that enhances resilience and provides opportunities for shifting distributions. We developed conceptual models to inform field studies and management, refined soils and vegetation attributes, and assessed regional population structure and threats. We used results to suggest prioritized locations for surveys, management, potential translocation, and additional conservation or acquisition. Project partners (U.S. Geological Survey and San Diego Management and Monitoring Program) modeled suitable habitat for the target species under current and future climate scenarios; we reference models as appropriate.
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Otay Mesa Rare Plants
The Otay Mesa Rare Plants Project will improve the conservation status of several of San Diego County's rarest plants on important conserved lands in Otay Mesa. The Project includes seed bulking for two high-priority Management Strategic Plan (MSP) plant species and direct restoration of five MSP plants with seeding, planting, and maintenance. Seeding, planting, and maintenance for the MSP plants will be conducted as part of two separate habitat restoration projects, one to restore vernal pools and maritime succulent scrub and another to restore maritime succulent scrub and native grasslands.
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Population Genetic Analysis of 6 Rare Plant Species in San Diego County
The first phase (years 1-2) of this research task focused on genetic and cytological screening to determine potential ploidy and population genetic differences among occurrences within species. Upon completion, an expert panel convened to review results of the genetic studies and develop specific recommendations for each species relative to the MSP management objectives planned for that species. These recommendations included designing appropriate common garden or reciprocal transplant studies to determine the fitness consequences of using seed from different populations to increase population size or establish new occurrences. The recommendations also addressed MSP objectives involving seed banking and seed bulking needs for each species. The expert panel also made recommendations on genetic management of populations, including whether genetic connectivity needs to be enhanced or restored to maintain or increase genetic diversity. Recommended and approved studies will be added in the second phase (beginning in year 3). The following questions were specifically addressed in phase 1:
1. What is the status of documented occurrences?
2. Is there evidence of mixed ploidy levels among or within occurrences?
3. What is current genetic structure among and within occurrences in the MSPA? How vulnerable are the occurrences to genetic drift and loss of genetic diversity and is there gene flow between occurrences?
4. Are there signatures of genetic bottlenecks or lower genetic diversity in populations that have undergone recent reductions due to fire, drought, or other causes, or evidence of local adaptation?
5. Based on the cytological and genetic analysis, what are the recommendations for common garden and reciprocal transplantations, for collecting, bulking and distributing seeds for enhancing existing occurrences, and for establishing new occurrences?
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Rare Plant Inspect and Manage Monitoring 2014-2026
From 2014-2026, a Management and Monitoring Strategic Plan (MSP Roadmap) monitoring objective for 30 rare plant species is to inspect occurrences to determine management needs. The inspect and manage (IMG) objective is implemented to document the status of rare plant occurrences and assess habitats and threats to develop specific management recommendations. IMG monitoring is implemented by a combination of land managers and contracted biologists in coordination with the SDMMP. Available rare plant data is posted below. New annual updates are typically posted in March. Based upon an evaluation of these data, a 2014-2026 monitoring schedule has been developed for the 30 rare plant species (attached below). Coordinating data collection across the region allows analyses of species and population trends over time and provides a better understanding of the association between habitat and threat covariates and population dynamics.
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Rare Plant Management and Seed Plan
MSP Roadmap 2019 and 2020 objectives include developing a Management Strategic Plan Framework Rare Plant Management Plan for Conserved Lands in Western San Diego County and a Management Strategic Plan Seed Collection, Banking, and Bulking Plan for Conserved Lands in Western San Diego County. These plans include general sections with background information and rationale for prioritizing and developing management recommendations with separate chapters and specific recommendations for priority species. In 2019, general framework sections were developed along with species chapters for San Diego thornmint, Nuttall's acmispon, salt marsh bird's-beak and Otay tarplant (CBI, AECOM and SDMMP 2020 a,b). In 2020, chapters will be developed for short-leaved dudleya, Orcutt's spineflower, and willowy monardella. These plans are developed with input and guidance provided by the Rare Plant Management Group Steering Committee and species working groups. Participants in these groups include landowners and managers, scientists, species experts, restoration specialists, seed collection and banking practitioners, and representatives from non-profit organizations and wildlife agencies. These plans are based on the latest scientific information for species on habitat relationships, ecology, genetics, seed collection guidelines, and best management practices. Occurrence-specific management recommendations are based on working group input and multiple years of Inspect and Manage monitoring data on population status, habitat associations and threats. These are living documents as new species chapters are added as they are developed and existing chapters are revised when new information becomes available or management actions are completed, and new recommendations are needed.
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SAN DIEGO THORNMINT ENHANCEMENT PROJECT
Project will expand and enhance three populations of San Diego thornmint (ACIL) on San Diego Habitat Conservancy managed properties. Project main goals are to improve ACIL habitat, and increase the ACIL seed bank to reduce the likelihood of extirpation. This project is partially funded by SANDAG TransNet EMP Land Management Grant #S1125501.
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San Diego Thornmint Genetic Analysis
Genetic studies were performed on San Diego Thornmint to help inform restoration practices. In this project, plant material was collected from a number of populations, a collection of seeds was gathered to obtain a representative sample of genetic diversity, a conduction of analysis of rangewide ploidy and isozomes was performed, and quarterly and annual reports were given to indicate progress and accomplishments. The Center for Natural Lands Management (CNLM), National Forest Genetics Laboratory of the USDA Forest Service, and the Applied Ecology Division of the Institute for Conservation Research, San Diego Zoo Global designed and conducted the studies.
Project partially funded by SANDAG TransNet EMP Land Management Grant #5001964
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San Diego Thornmint Restoration
The goal of the project is to improve and expand areas occupied by the San Diego thornmint (MSP Category SO [Significant occurrence(s) at risk of loss from MSPA]) within Mission Trails Regional Park (MTRP) Fortuna through restoration and enhancement of degraded habitat. This program addresses the immediate needs of thornmint within the MTRP by building on the on-going City weed treatment effort (based on SANDAG-funded CBI protocols to address Brachypodium distachyon) to address loss and degradation of existing thornmint habitat due to an increase of invasive plants and drought. Activities included in this program consist of herbicide treatment, thornmint and other native seed collection, seed bulking and redistribution, vegetation monitoring, photo monitoring, and thornmint monitoring. The methodologies used in conjunction with this proposal are similar to those used to restore approximately .25 acres of Pogogyne nudiuscula (Otay Mesa Mint) vernal pool habitat located in Otay Mesa. This project is consistent with the management objectives and actions prescribed in CBl's / SDMMP's Adaptive Management Framework for the Endangered San Diego Thornmint, the MTRP Natural Resources Management Plan, and the City of San Diego MHPA - Eastern Area MSCP Subarea Plan. Herbicide weed treatment within the thornmint population at MTRP Fortuna last occurred in 2014 and 2015.
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Valley Fire Rare Plant Discovery Surveys
A project between the SDMMP and US Forest Service to establish and prioritize survey areas on Conserved Lands within the perimeter of the 2020 Valley Fire to document whether historic occurrences are extant and to discover new occurrences for 18 rare plant species. In 2022, AECOM and Conservation Biology Institute botanists surveyed areas for 18 target rare plant species and mapped the spatial extent of each new occurrence, counted or estimated the occurrence population size, and collected voucher specimens. They also photographed each new occurrence from a georeferenced location that captured a representative view of the occurrence. Botanists created a species list for the areas surveyed within the Valley Fire footprint. These areas included locations where rare plants were detected and mapped and negative data point areas where rare plants were not detected. In 2023, botanists shall again conduct surveys on suitable habitat on USFS lands burned in the 2020 Valley Fire. Results from these surveys should lead to a greater understanding of post-fire rare plant composition. In 2023, botanists may see species that did not emerge in the first year of surveys, and species found in the first year of surveys may have expanded their range. The 18 rare plant species included in the surveys are: San Diego thornmint (Acanthomintha ilicifolia), Marvin's allium (Allium marvinii), Western spleenwort (Asplenium vespertinum), Deane's milkvetch (Astragalus deanei), Encinitas baccharis (Baccharis vanessae), San Diego goldenstar (Bloomeria clevelandii), Orcutt's brodiaea (Brodiaea orcuttii), Lakeside ceanothus (Ceanothus cyaneus), San Miguel savory (Clinopodium chandleri), Variegated dudleya (Dudleya variegata), Mission Canyon bluecup (Githopsis diffusa filicaulis), Ramona horkelia (Horkelia truncata), Heart-leaved pitcher sage (Lepechinia cardiophylla), Felt-leaved pitcher sage (Monardella hypoleuca lanata), Chaparral nolina (Nolina cismontana), Gander's ragwort (Packera ganderi), Moreno currant (Ribes canthariforme), and Parry's tetracoccus (Tetracoccus dioicus).
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Endemic to San Diego County, California, and northwestern Baja California, Mexico [1].
Forty-six occurrences on conserved lands in MU 2 (El Dorado Hills), 3 (Crestridge Ecological Reserve, Dennery Ranch, Hollenbeck Canyon Wildlife Area, San Diego National Wildlife Refuge, Otay Lakes Cornerstone Lands, City of Chula Vista Central City Preserve, South Crest Properties, Bonita Meadows, Flying Dolphin Trust, Otay Mountain Ecological Reserve, Rancho Jamul Ecological Reserve, Wright's Field), 4 (Canada de San Vicente, City of Poway Open Space, Cleveland National Forest, Mission Trails Regional Park, Simon Preserve, Sycamore Canyon and Goodan Ranch Preserves), 5 (Ramona Grasslands Preserve), and 6 (Black Mountain Open Space Park, Carlsbad Oaks North Habitat Conservation Area, Emerald Point Open Space, Los Penasquitos Canyon Preserve, Manchester Mitigation Bank, Rancho La Costa Habitat Conservation Area).
FE and CE [2].
Occurs in openings within coastal sage scrub, chaparral, and native grassland [3; cited in 1, 4]. Restricted to gabbro soils derived from igneous rock, and gray calcareous clay soils derived from soft calcareous sandstone [5; cited from 1]. Occurs on gentle (0-25 degrees) southeast to west facing slopes [1]. Elevation range is 10-960 meters [2]. Characterized by a low density of forbs and geophytes, and a low density or absence of shrubs [1].
Inbreeding was identified as a problem for small populations, which can have significantly lower germination rates due to high levels of homozygosity [6]. Has significant genetic structure [9]. Differentiation among populations is consistent with gene flow decreasing as a function of geographic distance. Longitudinal and elevational distance more strongly related to genetic differentiation than latitudinal distance. Potential polyploidy, but further confirmation needed.
Annual aromatic herb in the Lamiaceae (mint family) [1].
Winter annual that germinates in late winter to early spring and flowers in April and May [1]. Seeds mature in late spring and early summer.
Breeding and mating systems are unknown but a study of other congeneric species indicates some level of selfâ€compatibility and autogamous seed production [7; cited from 1]. The most common insect visitors for other congeneric species are medium†and largeâ€sized bees, particularly bumble bees. Excessive ground thatch may interfere with insect visitation and also nesting of potential pollinators such as groundâ€nesting bees [8, 9]. Species has a short-lived, above-ground seed bank, with very little seed stored in the soil [10].
USFWS 2009 5-Year Review determined urbanization as the most significant threat [1]. Proximity of development to occurrences leads to nonnative plant competition, trampling, fragmentation, and increased isolation. In 2009, 62 percent of occurrences were adjacent to development, cutslopes, agricultural fields, golf courses, ornamental landscaping, and fuel modification zones. Road construction, vehicles, grazing, foot traffic, recreational activities, and erosion are also threats [2]. Recreation occurring at over 40 percent of the extant occurrences is a potential threat because trail use on wet clay lens soils can cause deep ruts [1]. Particularly sensitive to competition from nonnative plants, such as purple false-brome, that alter habitat [9]. Fire can negatively impact habitat due to invasions by nonnative fire following plants [1].Climate change may affect longterm viability of current habitat due to: (1) drier conditions that may result in a lower percent germination and smaller population sizes; (2) higher temperatures may inhibit germination [10]; (3) a shift in the timing of the annual rainfall may favor nonnative species [1]; (4) the timing of pollinator life-cycles may become out-of-sync with timing of flowering; and (5) drier conditions may result in increased fire frequency, making the habitat more vulnerable to the threats of subsequent erosion and nonnative/native plant invasion.
Under a Local Assistance Grant from the California Department of Fish and Wildlife, the Conservation Biology Institute, in partnership with the San Diego Management and Monitoring Program, conducted a comprehensive review of existing information, past research, and current management and monitoring for San Diego thornmint and developed an Adaptive Management Framework for future research and monitoring [11]. Limitations to accurately assessing population status are: (1) lack of recent census data, (2) a comprehensive threats assessment, and (3) accurate mapping. These limitations are being addressed through the MSP Inspect and Manage objective with regionally coordinated monitoring efforts using a standardized protocol to assess population status, habitat, and threats [12]. In September 2014 the Center for Natural Lands Management completed an Environmental Mitigation Program Grant "Species-specific Management: Genetic studies of San Diego thornmint (Acanthomintha ilicifolia) to inform restoration practices" [9]. Recommendations for protecting the genetic integrity and diversity are: (1) Support natural regeneration of large populations, (2) Use management to rapidly increase the population size of any recently small populations, (3) Use collections of historically small populations to enhance population size, (4) Record and maintain records of any movement of plant material, (5) Design seed collections to maximize genetic diversity within population, (6) Keep seed collections separate at least by site if collection within large population.
[1]  U.S. Fish and Wildlife Service. 2009. “Acanthomintha Ilicifolia ( San Diego Thornmint ) 5-Year Review : Summary and Evaluation.†Carlsbad, California.
[2] CNPS, Rare Plant Program. 2016. Inventory of Rare and Endangered Plants (online edition, v8-02). California Native Plant Society, Sacramento, CA. http://www.rareplants.cnps.org, accessed 29 August 2016.
[3] Beauchamp, R.M. 1986. A Flora of San Diego County, California. National City, CA: Sweetwater River Press.
[4] Reiser, C.H. 2001. Rare Plants of San Diego County. San Diego, CA: Aquifer Press.
[5] Oberbauer, T. A., and J.M. Vanderwier. 1991. “The Vegetation and Geologic Substrate Association and Its Effect on Development in Southern California.†In Environmental Perils, San Diego Region, edited by P.L. Abbott and W.J. Elliot, 208–9. San Diego, CA: San Diego Association of Geologists.
[6] Menges, E.S. 1990. “Population Viability Analysis for an Endangered Plant.†Conservation Biology 4: 52–62.
[7] Steek, D.M. 1995. “Reproductive Biology of a Rare California Annual, Acanthomintha Duttonii, and Its Congener, Acanthomintha Obovata Ssp. Cordata.†University of California, Davis.
[8] Klein, M.W. 2009. “Pollinator Study on Lakeside Ceanothus (Ceanothus Cyaneus) and San Diego Thornmint (Acanthomintha Ilicifolia).†Contract No. PO650018. Sacramento, CA.
[9] Rogers, D. 2014. “EMP Grant - Final Report: Species-Specific Management: Genetic Studies of San Diego Thornmint (Acanthomintha Ilicifolia) to Inform Restoration Practices.â€
[10] Bauder, E.T., and J. Sakrison. 1999. “Mechanisms of Persistence of San Diego Thornmint (Acanthomintha Ilicifolia). FG7634R5.†Borrego Springs, CA.
[11] Conservation Biology Institute. 2014. “Adaptive Management Framework for the Endangered San Diego Thornmint , Acanthomintha Ilicifolia , San Diego County , California.†San Diego, CA.
[12] Rempel, R., Y. C. Moore, K. Preston, and E. Perkins. 2013. “Management Strategic Plan for Conserved Lands in Western San Diego County.â€