Rare Plants completed

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.
Project Focus

Dehesa nolina, Otay tarplant, Parry's tetracoccus, San Diego thorn-mint, Thread-leaved brodiaea

chaparral, coastal sage scrub, grassland

Emily Perkins

Patricia Gordon-Reedy

Conservation Biology Institute

A & L Western Laboratories; California Department of Fish & Wildlife; San Diego Management and Monitoring Program; San Diego State University; Space and Naval Warfare Systems Command (SPAWAR); The Nature Conservancy; U.S. Fish and Wildlife Service; U.S. Geological Survey

Patricia Gordon-Reedy; Spring Strahm

Sarah McCutcheon

Spring Strahm

Parry's tetracoccus Tetracoccus dioicus

Goal: Maintain or enhance existing Parry's tetracoccus occurrences to ensure multiple conserved occurrences with self sustaining populations to increase resilience to environmental and demographic stochasticity, maintain genetic diversity, and ensure persistence over the long term (>100 years) in chaparral and coastal sage scrub vegetation communities.

Regional NFO 2017 SS
MON-RES-SPEC TETDIO-3

Management units: 3, 8

In 2017, begin field research into soils and habitat relationships and conduct habitat suitability and climate change modeling for Parry's tetracoccus 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, habitat models, analyses, 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 Parry's Tetracoccus by 2018 2021
Threat Name Threat Code
Climate changeCLICHN
Invasive plantsINVPLA
Loss of connectivityLOSCON
Urban developmentURBDEV
Code Obj. code Statement
TETDIO-1 MON-IMP-IMG In 2019, inspect Parry's tetracoccus occurrences on Conserved Lands (see occurrence table) using the regional rare plant IMG monitoring protocol to record abundance and collect habitat and threats covariate data to determine management needs.

San Diego thorn-mint Acanthomintha ilicifolia

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.

Regional NFO 2017 SO
MON-RES-SPEC ACAILI-11

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 regimeALTFIR
Climate changeCLICHN
Human uses of the PreservesHUMUSE
Invasive plantsINVPLA
Loss of connectivityLOSCON
Urban developmentURBDEV
Code Obj. code Statement
ACAILI-2 MON-IMP-IMG 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.
ACAILI-5 MON-RES-GEN 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.
ACAILI-6 MGT-PRP-MGTPL 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

Thread-leaved brodiaea Brodiaea filifolia

Goal: Maintain or enhance existing Thread-leaved brodiaea occurrences to ensure multiple conserved occurrences with self sustaining populations to increase resilience to environmental and demographic stochasticity, maintain genetic diversity, and ensure persistence over the long term (>100 years) in grassland and vernal pool vegetation communities.

NFO 2017 SS
MON-RES-SPEC BROFIL-3

Management units: 6, 7, 8

In 2017, continue field research into soils and habitat relationships and development of habitat suitability and climate change models for thread-leaved brodiaea 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 thread-leaved brodiaea by 2018 2021
Threat Name Threat Code
Climate changeCLICHN
Invasive plantsINVPLA
Loss of connectivityLOSCON
Urban developmentURBDEV
Code Obj. code Statement
BROFIL-5 MGT-PRP-MGTPL In 2020, begin preparing a section for thread-leaved brodiaea in the MSP Rare Plant Management Plan that prioritizes management actions to maintain and expand conserved occurrences (see occurrence table) based upon an assessment of data on occurrence status, habitat and threats. Prioritize management recommendations for re-establishment of historic occurrences or establishment of new occurrences in suitable habitat, as needed, to achieve at least 4 occurrences with self-sustaining populations on Conserved Lands. Minimum criteria for enhancement are to reduce invasive annual nonnative plants and thatch to less than 20% absolute cover within the occurrence.

Otay tarplant Deinandra conjugens

Goal: Maintain or enhance existing Otay tarplant occurrences to ensure multiple conserved occurrences with self sustaining populations to increase resilience to environmental and demographic stochasticity, maintain genetic diversity, and ensure persistence over the long term (>100 years) in native and non native grassland vegetation communities.

Regional NFO 2017 SS
MON-RES-SPEC DEICON-11

Management units: 3

In 2017, continue field research into soils and habitat relationships and development of habitat suitability and climate change models for Otay tarplant 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, habitat models, analyses, 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 Otay Tarplant by 2018 2021
Threat Name Threat Code
Climate changeCLICHN
Invasive plantsINVPLA
Loss of connectivityLOSCON
Urban developmentURBDEV
Code Obj. code Statement
DEICON-10 MGT-IMP-SBPL In 2019, begin implementing the MSP Seed Collection, Banking and Bulking Plan for Otay tarplant 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.

Dehesa nolina Nolina interrata

Goal: Maintain or enhance existing Dehesa beargrass occurrences and establish new occurrences, as needed, to ensure multiple conserved occurrences with self sustaining populations to increase resilience to environmental and demographic stochasticity, maintain genetic diversity, and ensure persistence over the long term (>100 years) in chaparral vegetation communities.

Regional NFO 2017 SO
MON-RES-SPEC NOLINT-9

Management units: 3

In 2017, begin field research into soils and habitat relationships and conduct habitat suitability and climate change modeling for Dehesa nolina 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, habitat models, analyses, 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 Dehesa nolina by 2018 2021
Threat Name Threat Code
Altered fire regimeALTFIR
Climate changeCLICHN
Invasive plantsINVPLA
Loss of connectivityLOSCON
Code Obj. code Statement
NOLINT-1 MON-IMP-IMG Beginning in 2017 and continuing every 5 years, thereafter, continue inspections of Dehesa beargrass occurrences on Conserved Lands (see occurrence table) begun in 2014 using the IMG regional monitoring protocol to record abundance/map perimeters and collect threats and covariate data to determine management needs.
File name Lead Author Year Type
Enhancing the Resilience of Edaphic Endemic Plants Conservation Biology Institute 2018 report