|Listed||August 12, 1998|
|Description||A slender, perennial, ground-dwelling orchid.|
|Habitat||Monterey pine forest with a sparse understorey and maritime chaparral with dwarf shrubs.|
|Threats||Destruction by urbanization and development of golf course, along with competition with invasive alien plants, roadside mowing, and potentially an increase in deer grazing.|
Yadon's piperia, Piperia yadonii, is a slender perennial herb in the orchid family (Orchidaceae). Mature plants typically have two or three lanceo-late to oblanceolate basal leaves 4-6 in (10-15 cm) long and 0.8-1.2 in (2-3 cm) wide. The single flowering stems are up to 20 in (50 cm) tall with flowers arranged in a dense narrow-cylindrical raceme. The flowers consist of three petal-like sepals and three petals (together referred to as tepals). The upper three tepals are green and white and the lower three white. The lowermost tepal is specialized into a lip that is narrowly triangular and is strongly de-curved such that the tip nearly touches the spur of the flower. Piperia yadonii may occur with P. elegans,P. elongata, P. michaelii, and P. transversa, but it is distinguished from them in flower by its shorter spur length, particular pattern of green and white floral markings, and its earlier flowering time.
Yadon's piperia has light-weight seeds capable of long-distance dispersal through wind scattering; therefore, houses and other physical obstructions may affect seed dispersal. As in other orchids, germination of Yadon's piperia seeds probably involves a symbiotic relationship with a fungus. Following germination, orchid seedlings typically grow below ground for one to several years before producing their first basal leaves. Plants may produce only vegetative growth for several years, before first producing flowers.
The basal leaves in mature Yadon's piperia plants typically emerge sometime after fall or winter rains and wither by May or June, when the plant produces a single flowering stem. Only a small percentage of the Yadon's piperia plants in a population may flower in any year. This is consistent with what is known of other orchid species. As in some other plant taxa, individual orchids that flower in one year may not have the necessary energy reserves to flower in the following year, so size and flowering are not necessarily age-dependent.
Piperia yadonii was first collected by Leroy Abrams in 1925, in open pine forest near Pacific Grove. It was identified at that time as Piperia unalascensis, a polymorphic and wide-ranging species in the western United States. In a 1977 treatment of the genus Piperia, Ackerman segregated out several long-spurred taxa from the P. unalascensis complex, but attempted no analysis of the short-spurred forms. Morgan and Ackerman then segregated out two new taxa from the P. unalascensis complex in 1990, one of which was named Yadon's piperia after Vernal Yadon, former Director of the Museum of Natural History in Pacific Grove, Monterey County.
Yadon's piperia has been found in Monterey pine forest with a herbaceous, sparse understory and in maritime chaparral along ridges where the shrubs, most often Arctostaphylos hookeri (Hooker's manzanita), are dwarfed and the soils shallow. Yadon's piperia, like other orchids, does not appear to be an early successional species but is able to colonize trails and roadbanks within the dwarf maritime chaparral or Monterey pine forest once a decade or more has passed, if light and moisture regimes are favorable.
Yadon's piperia is found within Monterey pine forest and maritime chaparral communities in northern coastal Monterey County. Its center of distribution is the Monterey Peninsula where plants are found throughout the larger undeveloped tracts of Monterey pine forest. The range of Yadon's piperia extends north to the Los Lomas area, near the border of Santa Cruz County. Searches north into Santa Cruz County have uncovered little suitable habitat and no Yadon's piperia; nor do regional herbaria contain collections from Santa Cruz County. Since preparation of the proposed rule, Yadon's piperia has been found at one location about 15 mi (24 km) south of the Monterey Peninsula near Palo Colorado Canyon in maritime chap-arral. Maritime chaparral is uncommon along this region of the Big Sur coastline, but a few scattered patches do occur south to Pfieffer Point, located about 25 mi (40 km) from the Peninsula. This plant has been found only 4-6 mi (6.4-9.6 km) inland, despite searches of lands farther east. Toro Regional Park, 10-15 mi (16-24 km) inland, was searched and four unidentified Piperia were found, but the habitat was reported to be dissimilar to that favored by Yadon's piperia.
The Pebble Beach Company funded intensive surveys for Yadon's piperia, focusing first on the Monterey Peninsula in 1995 and then beyond the Peninsula to western Monterey County in 1996. Approximately 84,000 Yadon's piperia plants on about 350 acres were counted at all known sites throughout the range of this species since 1990. Plants are often densely clustered and may reach densities of 100-200 plants in a few square meters (10-20 plants in a few square feet). the age structure of these populations is not known because size and flowering are not always age-dependent.
During these surveys, the greatest concentrations of Yadon's piperia, approximately 57,000 plants or 67% of the known total, were found scattered throughout much of the remaining Monterey pine forest owned by the Pebble Beach Company and the Del Monte Forest Foundation on the Monterey Peninsula. About 8,500 of these plants are in open space areas there. Another 2,000 plants, 2% of all known, occur on remnant patches of Monterey pine forest in parks and open space areas of Pacific Grove and Monterey. Inland to the north, about 18,000 Yadon's piperia plants or 21% of all known plants, have been found on the chaparral covered ridges north of Prunedale. About 8,000 of these are on lands that receive some protection at Manzanita County Park and The Nature Conservancy's Blohm Ranch; the remainder are on private lands that are not protected. South of the Peninsula about 7,500 plants have been found on CDPR properties at Pt. Lobos Ranch, on surrounding lands that are to be turned over to CDPR in the future, and in a smaller parcel that is in private ownership.
Considering the current abundance of Yadon's piperia in the remaining large tracts of Monterey Forest, this species probably occurred throughout the Peninsula when Monterey pine forests were much more extensive.
Continued fragmentation and destruction of habitat due to urban and golf course development are currently the greatest threats to Yadon's piperia. Other threats include exclusion by alien species, roadside mowing, and potentially an increase in deer grazing of flowering stems.
The Monterey Peninsula provides the greatest amount of remaining contiguous habitat and supports about 70% of known individuals of this taxon. The Del Monte Forest has 184 acres (73.6 hectares) of Yadon's piperia, over half of the remaining area for this species. Based on the distribution of plants found in remaining Monterey pine forest, historical collections from the now-urbanized Pacific Grove area, and the amount of Monterey Pine forest which the Peninsula historically supported, the distribution of Yadon's piperia today is likely only a fraction of the historical extent of this species on the Peninsula. In the habitat that remains, this taxa occurs in 13 of the proposed subdivisions to be developed. The 245-acre (98-hectare) site of the proposed golf course supports about 16,000 individuals of this species and is the second largest contiguous stand of Monterey pine forest left on the Peninsula. The development currently proposed by the Pebble Beach Company would result in the loss or alteration of habitat supporting about 46,000 plants of Yadon's piperia on about 149 acres (60 hectares). This would represent about 80% of known plants on the Peninsula.
Including the 7,500 plants in the Huckleberry Hill Reserve, about 10,800 plants of Yadon's piperia would fall within proposed forested open space. Other open space areas are located at the ends or borders of the proposed subdivisions or in some cases are encircled by the proposed lots. The effects of habitat fragmentation are likely to result in the eventual extirpation of colonies in these areas. The alien shrub Genista monspessulana has invaded the nearby La Mesa housing development and is expected to engulf remnant habitats that support Yadon's piperia. Trampling by recreationists is a noted problem in remnant habitats that support Yadon's piperia at two city parks. Mowing for roadside fire control, which shears off the flowering stalks of this plant, thereby preventing reproduction, also occurs in remnant open space habitats on the Peninsula.
Beyond the Monterey Peninsula, over 60% of the known Yadon's piperia plants are on privately owned lands without protection, most of these in the Prunedale area. Two residential developments of over 40 acres (16 hectares), each of which support potential maritime chaparral habitat, have been approved. A third property, known to support several thousand Yadon's piperia, has been subdivided, although construction has not yet begun.
Increased predation (herbivory) by deer due to an elevated deer population on the Peninsula is a potential threat to Yadon's piperia. During surveys in 1995 and 1996 a sample of plants both on and off of the Peninsula were placed under cages to protect them from large herbivores. About 13% of the caged plants flowered, while in unprotected plants only about 2% could be found with flowering stems, a reduction of 85%. Severe herbivory of leaves, also likely from deer, has been noted as well Although the Service is not aware of any quantitative data on deer populations on the Peninsula, anecdotal evidence, such as sightings and reports of health, suggest that the number of deer on the Peninsula is high. If the loss of 85% of flowering stems calculated by Allen in 1996 is close to actual herbivory rates on the Peninsula, predation could have a substantial effect on the reproductive success of the species, particularly as populations are reduced by large scale habitat loss and fragmentation due to development.
The inadequacy of existing regulations is also a contributing factor in the status of this species. The biological surveys that are required under CEQA are are not always adequate to identify sensitive species. In the northern portion of the range of Yadon's piperia, for example, a 40-acre (16-hectares) residential development was approved in an area that contains maritime chaparral habitat and is located within 5 mi (8 km) of a known site of Yadon's piperia. The biological survey was conducted in September 1995, a seasonal time when no aboveground parts of Yadon's piperia are present.
Yadon's piperia, like many other orchids and showy-flowered monocots, may be particularly vulnerable to collecting by amateur and professional horticulturalists due to the plant's unusual flower and its tuberous growth habitat which increases the ease with which it can be moved.
Conservation and Recovery
The Yadon's piperia survives on about 350 acres (140 hectares) of scattered critical habitat, most of which is privately owned by the Pebble Beach Company and the Del Monte Forest Foundation on the Monterey Peninsula. Some habitats are protected in areas managed by these private owners as open space or parks, and others are conserved in Manzanita County Park, the Blohm Ranch of the Nature Conservancy, and land owned at Pt. Lobos Ranch by the California Department of Parks and Recreation. More of the privately owned critical habitat of the Yadon's piperia should be more strictly protected than is presently the case. This could be done by acquiring private habitat and establishing ecological reserves, or by negotiating conservation easements with the landowners. The populations of the Yadon's piperia should be monitored, and research undertaken into its ecological needs.
U.S. Fish and Wildlife Service
Ventura Fish and Wildlife Office
2493 Portola Road, Suite B
Ventura, California 93003-7726
Telephone: (805) 644-1766
U.S. Fish and Wildlife Service. 12 August 1998. "Endangered and Threatened Wildlife and Plants; Final Rule Listing Five Plants From Monterey County, California, as Endangered or Threatened." Federal Register 63 (155): 43100-43116.