Aliso: A Journal of Systematic and Floristic Botany Aliso: A Journal of Systematic and Floristic Botany Pogogyne Floribunda (Lamiaceae), A New Species from the Great Pogogyne Floribunda (Lamiaceae), A New Species from the Great Basin in Northeastern California Basin in Northeastern California

Pogogyne jloribunda is described as a new endemic species from Lassen and Modoc counties in northeastern California. Its occurrence on the eastern Modoc Plateau of the Great Basin Aoristic Province is the first record for the genus outside the California Aoristic Province. Pogogyne zizypho roides also is reported from the Great Basin in Lassen County.


INTRODUCTION
A distinctive new Pogogyne has been discovered in vernal pools and seasonal lakes of the Modoc Plateau in northeastern California at the west edge of the Great Basin Floristic Province (GBFP) circumscribed by Raven (1977). This is the first reported occurrence of the genus Pogogyne beyond the California Floristic Province (CFP), in which the genus was previously thought to be endemic (Raven and Axelrod 1978;Zedler 1987). The new Pogogyne and species associated with it could be relicts of the past migration of CFP species into the western GBFP. TAXONOMY Pogogyne floribunda Jokerst, sp. nov. Fig. 1 Caules plerumque multi basii, plerumque minus quam 10 em alti. Aores densi in spicas elongatas occultans caulis plurimi. Corolla 4-6 mm longa, alba maculis lavendulis in palato, occulta inter calyces et bracteis.
Specimen labels of P. floribunda collected before my investigations provide little habitat data. From my observations at Devils Garden, P. jloribunda occurs in seasonal1akes; wide, intermittently flooded drainages; and basalt-flow vernal pools (Holland 1986). Seasonal lakes and vernal pools supporting P. jloribunda are inundated or have saturated soil during winter and spring, and are generally dry by June or as early as April. In Devils Garden, seasonal lakes supporting P. jloribunda pond water only during years of above-average precipitation. Pogogyne jloribunda also occurs in intermittent drainages where topography prevents surface ponding.
The three types of seasonal wetlands with P. floribunda had a distinctive dark, grayish-brown or black, relatively deep Vertisol soil. It is classified as Ravendale clay loam, a fine, montmorillonitic, mesic, Entic Chromoxerert. This self-churning, expansive clay soil remains damp several centimeters below the surface throughout the hot summer (Lukow 1987).
Pogogyne floribunda at Devils Garden often occurs with a 30-60% cover of The presence of P. floribunda in the western GBFP documents the previously acknowledged floristic tie with the CFP (Griffin 1966;Young, Evans, Kay, and Budy 1986).
Pogogynejloribunda germinates and flowers during June after surface water has dried. Seedlings of P. floribunda were not visible on 11 May 1987 at a site where the plants were abundant 6 weeks later. Flowering continues through August. Pogogyne floribunda begins flowering soon after emerging from the soil and con- tinues throughout summer when adequate soil moisture is available. A heavy July rain shower caused plants with maturing fruit to rebranch at the base with new, actively flowering stems. Seed is produced from July to September. Pogogyne floribunda occurs in a habitat that is vulnerable to destruction or alteration. It has a relatively narrow range and is known from only a few populations (Fig. 1 ), but a thorough survey throughout its range has not been conducted. Reports of 5050 hectares of Artemisia cana subsp. bolanderi vegetation in a 145,750-hectare portion of the Devils Garden (Salwasser and Shimamoto 1981) indicate undocumented populations likely exist. The species may occur in southeastern Oregon and northwestern Nevada, which are connected to the eastern Modoc Plateau by sagebrush scrub and juniper woodland vegetation with vernal pools and seasonal lakes. Although normally the stems are concealed by flowers, P.floribunda specimens collected or observed during late summer may have naked lower stems. This may be due to the following reasons: 1) the lower stem can be buried as Vertisol soils expand and fluff, 2) plants rooted in deep soil cracks flower only along portions of the stem that are above ground level, and 3) calyces and bracts of the lower stem can mature and abscise by late summer while the upper stem is still concealed by flowers.
Pogogyne floribunda is assigned to Section Hediomoides because the corollas are scarcely exserted from the calyx and are thus inconspicuous, and the upper stamens are rudimentary (Howell 1931a). Specimens key to P. zizyphoroides Benth. in Munz (1968) or Peck (1941). Section Hediomoides spans the geographic range of the genus Pogogyne, with the localized endemics P. floribunda and P. tenuiflora Gray of Guadalupe Island, Baja California, at the northern and southern range extremes and the widespread P. zizyphoroides and P. serpylloides (Torr.) Gray in the intervening region. Munz ( 1968) acknowledged a distinctive trait of P. jloribunda when recognizing the summer-flowering form of P. zizyphoroides from the Modoc Plateau. Prior records for the genus on the Modoc Plateau are not documented. Neither Howell ( 1931 a, b) nor Jepson (1943) cited collections from the Modoc Plateau. The Modoc Plateau was excluded from the distribution of Pogogyne zizyphoroides and other Pogogyne species by Jepson (1951), Abrams (1951), Mason (1957), Peck (1941), Hitchcock, Cronquist, Ownbey, and Thompson (1959), and Cronquist, Holmgren, Holmgren, Reveal, and Holmgren (1984). An obscure reference to a Modoc Pia-teau Pogogyne was uncovered in the original description of Polygonum esotericum Wheeler (Wheeler 1938), where P. zizyphoroides is listed as an associate.
The distribution, morphology, and ecology of P. floribunda suggest its closest relationship lies with P. zizyphoroides. Historic collections of P. floribunda were probably referred to asP. zizyphoroides because of their morphological similarity and the latter's presence in cismontane northern California and southern Oregon. Both species have dense-flowered, spicate inflorescences and flowers with the same shape and dimensions. The two species differ, however, in their habit, stature, inflorescence size, flower color, geographic range, phenology, and habitat associations, as described below.
Pogogyne jloribunda has white flowers in long, continuous spikes that extend the length of the stem. Plants are usually branched at the base and produce few to many flowering spikes that rarely exceed 10 em in height (30-cm stems have been observed). Pogogyne zizyphoroides, in contrast, has purple or pink flowers in an interrupted spike of terminal and axillary flower clusters. Dried flowers of P. zizyphoroides can appear colorless but retain a faint lavender hue under magnification. Stems of P. zizyphoroides are branched above the base, typically exceed 10 em, and are not flowered along the lower stem. The stems, leaves, bracts, and calyces of P. zizyphoroides are more densely hirsute than those of P. floribunda, and the leaves of the former are generally larger and typically persist throughout anthesis, while those of P. floribunda often abscise during anthesis.
Pogogyne floribunda flowers from June to August. The eastern Modoc Plateau is characterized by a cold desert climate with 25-38 em of annual precipitation. Winters have freezing temperatures and most precipitation falls as snow. The soil of vernal pools and seasonal lakes with P. floribunda is usually submerged under water, snow, or ice during winter, flooded or saturated during spring, and normally dry at the surface by summer.
In contrast, P. zizyphoroides flowers from March to May and occurs in portions of California and Oregon with a Mediterranean climate characterized by mild, wet winters with occasional freezing temperatures. Annual precipitation ranges from 6 to 12 em, most of which falls as rain. Vernal pools and swales supporting this species are continuously or intermittently flooded or have saturated soils from November to April, and are dry by May.
An exceptional P. zizyphoroides population is known from the GBFP in Secret Valley, Lassen County ( Fig. 1) (Schoolcraft 1022, 28 Jun 1983, mudflats with silver sage, T31N, RISE, S. 22, specimen at the U.S. Bureau ofLand Management herbarium, Susanville, California) (Fig. 1). The collection clearly represents P. zizyphoroides. This most easterly population of P. zizyphoroides is disjunct from its main distribution in eastern Shasta County and near Burney and Weed in Siskiyou County by over 46 km. ACKNOWLEDGMENTS I am grateful to the California Academy of Science and the University of California, Berkeley, for the use of their facilities and specimens. I thank the curators and staff at the California Academy of Science for their support and their assistance in obtaining specimens. I also acknowledge the assistance of Tony Rypich, who prepared the map; Jane Palik, who provided word processing; Dr.