The conservation status and natural history of Pogogyne floribunda in Oregon

Call Number:

URL:

Keywords:

Abstract:

Pogogyne floribunda is a recently described (1992), annual mint species reported from an estimated six scattered sites in Oregon and one in western Idaho. It is otherwise restricted to a handful of locations in northeastern California on the Modoc Plateau, and is designated as a sensitive species by the BLM and a species of concern by the U.S. Fish and Wildlife Service. Populations are restricted to summer-dry playa lake beds and ephemeral channels in Great Basin silver sagebrush communities, and occur exclusively on public lands. The three year project described here was undertaken to evaluate the biology, taxonomic standing, and conservation status of the species in Oregon. Three Oregon populations were studied. <br>

Pogogyne floribunda is highly autogamous yet has a mixed mating system. Greenhouse and field studies show that plants are predominantly self-pollinated, and although outcrossing via insect pollinators is probably infrequent, it can occur and is potentially important in maintaining and enhancing local genetic variation. Accordingly, it may play a role in any evolutionary diversification of populations. Plants are typically highly fecund and tend to be prolific seed producers, which is significant since the species depends on seed banks to maintain populations. Seed germination is variable - some seeds are germinable when dispersed, while others are dormant and move into the seed pool. In dry years, the species may not appear at all, though it is important to recognize that populations are still viable below the surface. It is therefore imperative to protect known habitat and document the boundaries of populations, to ensure conservation of the cryptic but important seed banks. The species appears to have limited susceptibility to foliar and flower predation in the wild - predators that infest cultivated mint fields may actually be the greatest insect threat to the species, at least in areas where mint farming and wild populations of Pogogynecoincide. Plants have no known mychorrizal or other symbiotic associations, and are readily cultivated in a greenhouse setting. Large numbers of seeds can be produced quickly and efficiently for artificial seed banking, population augmentation, or other conservation purposes. <br>

Cattle are common components of the playa ecosystems favored by Pogogyne populations in Oregon. Exotic weed species are not presently a significant competitive threat, though continued trampling of Pogogyne sites by livestock may ultimately change this dynamic if weeds are able to invade the playas as a result of the disturbance. The large population occurring on the Klamath Resource Area, near Dog Hollow Reservoir (the largest site for the genus in Oregon), appears capable of withstanding modest grazing impacts, though specific and broader assessments are needed to evaluate the effects of long-term grazing and trampling. The two disjunct populations studied here, from the Vale and Lakeview Districts (i.e., at Bull Flat and Foley Lake RNA), also need explicit study regarding grazing impacts ñ their smaller size, scattered population structure, and exposure to denser livestock concentrations suggest that the Pogogyne plants occurring here probably face the most serious threats from cattle. Soil moisture is a critical factor governing the distribution and survival of Pogogyne populations, with plants preferring intermediate soil moisture zones on the playas. Management actions that either dry out playas or increase the duration and extent of flooding can both be destructive influences. <br>

Populations that occur at the outer boundaries of a speciesí range can exhibit unique qualities, and are often of interest to geneticists and conservationists. A goal of this study was to determine if the peripheral and disjunct Oregon populations of P. floribunda are comparable to those growing on the nearby Modoc Plateau area of California (i.e., those populations centered around the type locality). Morphometric and chloroplast DNA evaluation indicate the plants from the large Dog Hollow site are indeed typical for the species, while those from the highly disjunct Bull Flat and Foley Lake RNA populations are not. The latter populations are significantly divergent from typical P. floribunda, with the nucleotide data suggesting they have been potentially separated from the Modoc Plateau phenotype for perhaps tens of thousands of years. Moreover, the plants at Foley Lake may in fact be more closely related to a sister species, P. zizyphoroides, which otherwise occurs west of the Cascade-Sierran axis in low elevation valleys from extreme southwest Oregon to north-central California. While the disjunct Oregon populations are very interesting and may ultimately be worthy of formal taxonomic recognition, such a decision awaits further sequencing work, to place the divergence measured thus far into context within the genus. Formal taxonomic recognition would likely carry strong potential for listing under the federal ESA. In the meantime, it is recommended that P. floribunda sites continue to be protected by BLM, considering they plainly represent an evolutionarily significant genetic resource. <br>

Notes:

Reference Code: U06MEI01IDUS <br>

Full Citation: Meinke RJ. 2006. The conservation status and natural history of Pogogyne floribunda in Oregon. USDA Forest Service. Corvallis, Oregon. 47 pp <br>

Location: ELECTRONIC FILE - BOTANY: PLANT SPECIES: Pogogyne floribunda <br>

Keywords: Pogogyne, Pogogyne floribunda, Oregon, Idaho, Lamiaceae <br>

File(s): 

pogogyne-floribunda-cons-status-natural-history-2006-09.pdf