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Holocarpha Macradenia (Santa Cruz Tarplant) 5-Year Review: Summary and Evaluation

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Holocarpha Macradenia (Santa Cruz Tarplant) 5-Year Review: Summary and Evaluation Holocarpha macradenia (Santa Cruz tarplant) 5-Year Review: Summary and Evaluation Photos: Kim Hayes, Elkhorn Slough Foundation U.S. Fish and Wildlife Service Ventura Fish and Wildlife Office Ventura, California February 2014 5-YEAR REVIEW Holocarpha macradenia (Santa Cruz tarplant) I. GENERAL INFORMATION Purpose of 5-Year Reviews: The U.S. Fish and Wildlife Service (Service) is required by section 4(c)(2) of the Endangered Species Act (Act) to conduct a status review of each listed species at least once every 5 years. The purpose of a 5-year review is to evaluate whether or not the species’ status has changed since it was listed (or since the most recent 5-year review). Based on the 5-year review, we recommend whether the species should be removed from the list of endangered and threatened species, be changed in status from endangered to threatened, or be changed in status from threatened to endangered. Our original listing of a species as endangered or threatened is based on the existence of threats attributable to one or more of the five threat factors described in section 4(a)(1) of the Act, and we must consider these same five factors in any subsequent consideration of reclassification or delisting of a species. In the 5-year review, we consider the best available scientific and commercial data on the species, and focus on new information available since the species was listed or last reviewed. If we recommend a change in listing status based on the results of the 5-year review, we must propose to do so through a separate rule-making process defined in the Act that includes public review and comment. Species Overview: As summarized in the final listing rule for the species (Service 2000), Holocarpha macradenia (Santa Cruz tarplant) is an aromatic annual herb in the aster family (Asteraceae). Holocarpha macradenia is one of only four species of the genus Holocarpha, all geographically restricted to California. At the time of listing, we identified the primary threats to H. macradenia as: alteration and destruction of habitat due to historic and ongoing urban and commercial development; historic habitat alteration by grazing of native vegetation; limited success of seed transplant (experimentally seeded) populations; and competition from nonnative, invasive plants. Holocarpha macradenia occurs in 14 native and 4 to 8 experimentally seeded populations in coastal grasslands and prairies in Contra Costa, Santa Cruz, and Monterey Counties, California (Service 2000). Methodology Used to Complete This Review: This review was prepared by the Ventura Fish and Wildlife Office (VFWO), following guidance issued by the Pacific Southwest Region of the Service in March 2008. We used survey information from experts who have been monitoring various localities of this species and the California Natural Diversity Database (CNDDB) maintained by the California Department of Fish and Wildlife (formerly the California Department of Fish and Game) (CDFW). Personal communications with experts were our primary sources of information used to update the species’ status and threats. A recovery plan has not been prepared for this species. This 5-year review contains updated information on the species’ biology and threats, and an assessment of that information compared to that known at the time of listing. We focus on current threats to 2 the species that are attributable to the Act’s five listing factors. The review synthesizes all this information to evaluate the listing status of the species and provide an indication of its progress towards recovery. Finally, based on this synthesis and the threats identified in the five-factor analysis, we recommend a prioritized list of conservation actions to be completed or initiated within the next 5 years. Contact Information: Lead Regional Office: Lisa Ellis, Fish and Wildlife Biologist, Region 8, Pacific Southwest, (916) 414-6464. Lead Field Office: Lena Chang, Fish and Wildlife Biologist, (805) 644-1766 ext. 302; Connie Rutherford, Listing and Recovery Program Coordinator for Plants, (805) 644- 1766 ext. 306; Ventura Fish and Wildlife Office. Federal Register (FR) Notice Citation Announcing Initiation of This Review: A notice announcing initiation of the 5-year review of this taxon and the opening of a 60-day period to receive information from the public was published in the Federal Register on May 21, 2010 (Service 2010). No comments were received as a result of that notice. Listing History: Original Listing FR Notice: 65 FR 14898 Date of Final Listing Rule: March 20, 2000 Entity Listed: Holocarpha macradenia (Santa Cruz tarplant), a plant species Classification: Threatened State Listing Holocarpha macradenia was listed by the State of California as endangered in 1979. Associated Rulemakings: Critical Habitat FR Notice: 67 FR 63968 Date Designated: October 16, 2002 Area Designated: 2,902 acres (1,175 hectares (ha)) Review History: Since the listing rule was published in 2000 and critical habitat was designated in 2002, there have been no formal reviews conducted for Holocarpha macradenia. Species’ Recovery Priority Number at Start of 5-Year Review: The recovery priority number for Holocarpha macradenia is 8 according to the Service’s 2009 Recovery Data Call for the Ventura Fish and Wildlife Office (Service 2009). This number is based on a 1-18 ranking system where 1 is the highest ranked recovery priority and 18 is the lowest. This number indicates that H. macradenia is a species that faces a moderate degree of threat and has a high potential for recovery (Service 1983). 3 Recovery Plan or Outline A recovery plan for Holocarpha macradenia has not been prepared. II. REVIEW ANALYSIS Application of the 1996 Distinct Population Segment (DPS) Policy The Endangered Species Act defines “species” as including any subspecies of fish or wildlife or plants, and any distinct population segment (DPS) of any species of vertebrate wildlife. This definition of species under the Act limits listing as distinct population segments to species of vertebrate fish or wildlife. Because the species under review is a plant, the DPS policy is not applicable, and the application of the DPS policy to the species’ listing is not addressed further in this review. Information on the Species and its Status Species Biology and Life History Holocarpha macradenia is an aromatic annual herb in the aster family (Asteraceae), and is one of only four species of the genus Holocarpha, all geographically restricted to California. Holocarpha macradenia occurs in coastal terrace prairie habitat along the coast of central California in Contra Costa, Santa Cruz, and Monterey Counties. Holocarpha macradenia is an upright annual plant, standing on average, less than 24 inches (61.0 centimeters (cm)) tall, and is distinguished from other members of the genus by its numerous ray flowers and black anthers. Like many tarplants, H. macradenia is strongly scented and produces a sticky resin (Keil 1993, Hayes 1998, Holl and Hayes 2006). Flowering from July to October, the inflorescences comprise yellow ray and disc flowers. Native bees, flies, wasps, and winged beetles have been observed pollinating H. macradenia (Barber 2002). Most seeds remain on the plant until the first significant rain (0.6-1.2 inches (15–30 millimeters (mm)) in late autumn (Service 2002, Holl and Hayes 2006). Seed Ecology The basal rosette (leaves radiating from the stem near ground-level) increases in size until approximately June, when plants produce a stem that reaches a height of 11.8 to 31.5 inches (30 to 80 centimeters (cm)). Plants produce 1 to 60 inflorescences with two types of flowers that produce two types of achenes (seeds) with different morphologies and requirements for germination. Seeds from the ray flowers have a thicker seed coat, long-term dormancy, and complex germination cues; whereas seeds from the disk flowers are lighter, and narrower. Neither type of seed appears to have a structural means for dispersal, and most fall within 17.7 inches (45 cm) of the plant (Holl and Hayes 2006) though it is possible that some ray seeds may be dispersed over long distances by animals (Satterthwaite et al. 2007). Holocarpha macradenia is self-incompatible, meaning that individuals will not produce viable seeds without cross pollinating with other individuals (Baldwin, in litt. 2001). Gene flow between populations increases the likelihood of viability by maintaining genetic diversity; 4 therefore, gene flow is essential for the long-term survival of self-incompatible species (Ellstrand 1992). Results of studies indicate that disk seeds produced by Holocarpha macradenia germinate within a year of production while ray seeds form persistent seed banks. The precise length of time H. macradenia seed banks remain viable is unknown, though there is an account of H. macradenia seedlings emerging from a pile of soil scraped from a construction site 8 years after it last hosted adult plants. It is possible that seed bank survival is high, since seeds known to be at least 15 years old have successfully germinated (Barber 2002). Because H. macradenia is capable of establishing seed banks, sites that support populations of the species, particularly small populations (fewer than 100 individuals), may not display any individuals in a given year, but can have viable populations in other years (Service 2000). Management of seed banks (i.e., scraping or other habitat manipulations to enhance germination) must be balanced between germination of seeds in the seed bank before they become too old, and the risk of overstimulation that may result in depletion of the seed bank and reduction of its ability to buffer against environmental variability (Satterthwaite et al. 2007, Watsonville Wetlands Watch 2009). Spatial Distribution Historically, habitat for Holocarpha macradenia occurred on grasslands and prairies found on coastal terraces in elevations below 330 feet (100 m), from Monterey County, north to Contra Costa and Marin Counties. Holocarpha macradenia was known from “low dry fields about San Francisco Bay” (Jepson 1925).
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