Drainage of aquatic habitat for urban and agricultural development (Meinke 1982) Invasion of noxious weeds: e.g. reed canary grass (Phalaris arundinacea), and purple loosestrife (Lythrum salicaria. (WNHP 1999, USFWS 1994)). Invasion of reed canary gr

Most sites containing H. aquatilis are < 1 acre (FWS web page) As of 2000 (Rush and Gamon 2000, USFWS 1996, CDFG 2001): The main geographical areas where H. aquatilis is found include: 1-- ID (Latah Co.) 1 occurrence 3 --WA (Spokane, Clark and Pierce Co) 45 occurrences in Spokane Co., 5 occurrences in Pierce Co. and One (1) in Clark County. 1 - MT (Lake and Missoula Co.) A total of 101 occurrences in Lake and Missoula Counties. 1 - CA (Medocino Co, rediscovered in 1996). 6 occurrences.

Germination trials preformed on MT populations by Lesica (1992) found that seeds had significantly lower germination rates after 8 months of dried storage. Additionally, plants grown from older seeds had reduced vigor (Lesica 1992). However, different monitoring studies indicated that seeds retained germinability for at least 2 years (Schassberger and Shelly 1991, Shelly 1992). These conflicting germination results may reflect variability in duration of seed viability, perhaps correlated with the extent of wetland drying in a year (Shelly 1992 based on work done by Lesica 1991, USFWS 1996). Germination trials and observations. Howellia aquatilis has relatively large seeds, and is capable of germinating in both the dark and at low temperatures, which are characteristic of plants that generally do not form persistent seed banks (Lesica 1990). H. aquatilis germination was 2-3 times greater under an above-freezing, fluctuating temperature regime, possibly the consequence of a mechanism that prevents germination of seeds that are buried too deep (Lesica 1990). While H. aquatilis requires submersion to grow and reproduce, it cannot germinate under anaerobic conditions (Lesica 1990). The seed bank peaks in September, immediately after seed dispersal. By mid-October, approximately 25 percent of the seed bank has germinated, and the seed bank is reduced to 40% of the September peak. Disease and predation reduce the seeds back to 10 percent of the September peak by mid-May (Lesica 1990). Optimal development for H. aquatilis occurs in ponds that dry down in wet years but do not dry up too early in dry year (Lesica 1990, 1992). Relatively shallow organic and mineral sediments with high levels of nutrient availability provide optimal H. aquatilis habitat. Disturbances that cause a decrease in pond fertility will have strongly adverse effects on H. aquatilis populations (Lesica 1990). Germination trials in a variety of soils indicate that H. aquatilis has difficulty completing its lifecycle in non-organic substrates (Lesica 1992). Water pH and water conductivity are often highly related, and are probably important in determining the distribution of H. aquatilis, but not the abundance in an area (Lesica 1990). Howellia aquatilis is negatively associated with dissolved solids, indicating that this species is probably restricted to fresh water (Lesica 1992). Abundant graminoid cover may exclude H. aquatilis from some ponds (Lesica 1992). Individuals/population can vary dramatically annually. Monitoring showed that in 1985 and 1987, 10,000 plants established, but in 1986 there were fewer than 100 plants (Lesica et al. 1988). Transplant experiments were preformed to determine the viability of transplanting seedlings into ponds that still contain water (H. aquatilis will not germinate in anaerobic environments). Two years after the plantings, plants were still present at the two transplantation sites. However, one of the sites experienced an 85% decrease in population side between the first and second year of monitoring. Additionally, while the sites contained reproductive plants after the first year, no new plants were apparent after the second year. The possibility of further decline, followed by local extinction, is high for both ponds. If the populations persist, these results would suggest that limited dispersal events keep H. aquatilis from establishing in suitable ponds. If they do not persist, it is possible that transplanted ponds were unsuitable for H. aquatilis over the longer term (Roe and Shelly 1991). Protein electrophoresis was used to examine the genetic structure of 4 populations. 8 enzymes on 18 loci were encoded. All the loci were monomorphic for the same allele, both within and between populations. H. aquatilis appears to have only one homozygous genotype throughout its entire range It is likely that these populations have not had enough time since separation to diverge genetically. It is difficult to determine if these plants are rare because they are genetically impoverished or vice versa (Lesica et al. 1988).

Listed as Threatened under the Endangered Species Act. Critical habitat was not designated, because the Fish and Wildlife Service was concerned about the publication of site-specific maps of critical habitat (USFWS 1994).

Continue inventory studies (WNHP 1999) Continue population and transect monitoring (Shelly 1992). Research seed bank dynamics further. Seed bank production is likely to be higher in years when the pond retains more water, but subsequent effects of high water level on seed bank persistence is unknown (Shelly 1992). Research the longevity of seed viability, especially in regards to wetness/dryness of the environment (USFWS 1996, Rush and Gamon 2000). Detailed study of population dynamics in relation to pond drying and other climatic influences (Shelly 1992, Rush and Gamon 2000). Also, population dynamics in relation to snowpack depth, annual precipitation and temperature patterns (USFWS 1996). Further study the effect of predation and disease on seed bank and population (Shelly 1992) Study the successional pathways and rates of emergent freshwater ponds. Determine if artificial habitat maintenance can be used to maintain populations (USFWS 1996). Study the degree of threat posed by reed canary grass (Phalaris arundinacea) (Rush and Gamon 2000). Investigate the relationship between nutrient availability and the abundance of Howellia (Shelly 1992). Maintain a forested buffer with a minimum width of 300ft around aquatic habitats. Logging and vegetation disturbing activities in this buffer should be minimized, but activities may be necessary to maintain the buffer (management for mountain pine beetle kill, prescribed burning) (Shelly 1992). The potential effects of prescribed burning should be examined prior to burning areas with H. aquatilis. Early season burns likely do not have an adverse effect, because the ponds still contain water (USFWS 1996). Create and maintain corridors between ponds for animal movement to facilitate seed dispersal and maintain metapopulation dynamics (Shelly 1992). Determine the mechanisms by which seeds are dispersed between ponds (Rush and Gamon 2000) Check suitable but currently unoccupied ponds to determine if species is colonizing new sites (USFWS 1996). Preservation of sites that have a broad scope of ponds at different stages of succession, providing suitable colonization habitats as ponds that currently contain H. aquatilis become inappropriate (Lesica 1988). Restore populations in areas where the plant was know to occur historically (Lesica 1988). Model rates of colonization and extirpation (Rush and Gamon 2000).

Seeds cannot be saved using conventional means (i.e.. Drying and freezing.) Determine successful means of maintaining viable seed or plant material. Collect and store seeds or plant material.