Abronia umbellata ssp. breviflora
|pink sand verbena|
|Edward Guerrant, Ph.D.|
The following Participating Institutions are custodians for this species in the CPC National Collection:
Rae Selling Berry Seed Bank & Plant Conservation Programs
The conservation of Abronia umbellata ssp. breviflora is fully sponsored.
Edward Guerrant, Ph.D. contributed to this Plant Profile.
Due to an ironic twist of fate, pink sandverbena was the first North American plant collected and described from west of the Mississippi. Pink sandverbena seeds were first collected at Monterey Bay, CA on a 1786 scientific expedition. The collector, Jean-Nicolas Collignon, was subsequently lost at sea with his ship. The seeds, however, had been sent back Paris on another ship, where they were grown in the Jardin des Plantes and named. Without active conservation efforts, pink sandverbena's ultimate fate may be as grim as that of the man who discovered it.
Abronia umbellata ssp. breviflora was once found all along the Pacific coast, from northern California to British Columbia. Today it is limited to a few populations in northern California and Oregon. Long thought extinct in both Washington and British Columbia, two individuals were recently found on Vancouver Island that may be this species. Habitat destruction caused by human activity and exotic plant invasion does not solely impact this sandy beach dwelling species. The plight of the endangered western snowy plover (a native bird) appears correlated with the state of pink sandverbena. Both of these species require open sandy beaches, and evidence suggests that the snowy plover uses this sandverbena for forage and cover. It follows that efforts to conserve either of these species will be most effective if coordinated with each other.
In 2000, two plants were found on Vancouver Island in British Columbia, Canada. The debate continues as to whether they are A. umbellata ssp. breviflora or a separate taxon, A. umbellata ssp. acutalata. If they are A. umbellata ssp. breviflora, then the range truly extends from northern California to Canada. If, however, they are identified as A. umbellata ssp. acutalata, two points become apparent: 1) there are only TWO remaining INDIVIDUALS of A. umbellata ssp. acutalata in the entire world and 2) the range of A. umbellata ssp. breviflora has been reduced to include only northern California and Oregon.
Distribution & Occurrence
Pink sandverbena inhabits open sandy beaches, typically at or below the zone of driftwood accumulation and away from sand dominated by introduced European beachgrass (Ammophila arenaria) (Kaye 1997a, Kaye et al 1998).
|As of 2000: extinct in WA; known to occur OR and CA. In 2000, a small population of two individuals was discovered on Vancouver Island (Kaye 2000). Approximately 41 sites in California are listed as "presumed extant" by the California Natural Diversity Database (2001). Approximately six populations have been observed in Oregon since the mid-1980s (ONHP Database, 2000). Despite these seemingly high numbers, populations tend to move about and this is not likely an accurate snapshot of things as they currently are. Populations are often very small (one or two individuals).|
Conservation, Ecology & Research
Cold treatments in germination were largely unsuccessful. Instead, alternating warm temperatures was required. These results are consistent with natural conditions in A. umbellata ssp. breviflora habitat - the Pacific Coast generally receives a week or so of warm weather in early spring (Kaye et al 1998, Kaye 1999).
Since populations are typically found at or below zone of driftwood accumulation, they are often obliterated by winter storms. Each spring, the population re-establishes from seeds that persist in the sand. In protected sandy areas, 3% of population over-winters and flowers the next year (Kaye et al., 1998).
Natural populations sizes vary widely over time and space. For plants growing in more a static habitat, the observed drops in population size and reproductive output would be cause for grave concern. However, A. umbellata ssp. breviflora grows in a dynamic habitat characterized by winter storms that destroy old plants, but also create new habitat and disperse seeds. In areas outside monitoring plots, observations indicate that A. umbellata ssp. breviflora expands well onto recently deposited or disturbed substrates (Kaye 1999).
Abronia umbellata ssp. breviflora numbers tend to decline with substrate age, especially after 3 years. Generally, other plant species increase in abundance and diversity (species richness) (Kaye 1999). Nutrient cycling in the soil affects these trends. In general fresh sand provided near optimal conditions for A. umbellata ssp. breviflora growth (Kaye 1999). After sand has been dredged, nitrogen increases with time, while potassium declines. On older substrates, nutrients are limiting (especially potassium) and competition for them is intense. While both increases in interspecific competition and decreases in soil fertility contribute to A. umbellata ssp. breviflora decline, is likely that competition has the stronger impact. On older substrates, adding fertilizer in the presence of competitors fertilizes the associated species as well, and competitors are able to establish and rapidly grow roots into pocket of nutrients below A. umbellata ssp. breviflora individuals (Kaye 1999). Frequent disturbances remove competing vegetation and may be required to maintain viable populations of pink sandverbena (Kaye 1999).
Individuals within this species can be either annuals or short-lived perennials (Grenier 1991). Disturbances from winter storms play a complicated and important role in the life cycle of A. umbellata ssp. breviflora. These winter storms remove and deposit large amounts of sand, establish foredunes, and carry plants and seed out to the ocean. This disturbance often buries plants, preventing their short-term persistence; some restoration efforts have not been successful after the first year because of this phenomenon. However, winter storms also prevent other plants from establishing and outcompeting A. umbellata ssp. breviflora. This disturbance can be especially important in removing European beachgrass (Ammophila arenaria). Paradoxically, winter storm disturbances both hinder short-term survival of individuals and help the long-term persistence of populations and the species by creating new habitat (Kaye 2000).
Genetic analyses of reintroduced populations indicates that the population size at the time of founding has a significant effect on the genetic diversity of that population. Genetic distance indicated limited divergence among most natural populations. It is likely that this limited divergence is due to a population bottleneck at some time in the species' history, or to high rates of migration between populations. This genetic similarity reveals that populations do not appear to be genetically adapted to one particular site, and consequently have more widespread reintroduction potential. Genetic contamination from reintroducing plants to natural populations is not much of an issue because all populations are so similar (McGlaughlin, 2000).
Scientists currently debate whether the plants found in British Columbia are another, otherwise extinct taxon: Abronia umbellata ssp acutalata. If they indeed are distinct, then there are only two remaining individuals of Abronia umbellata ssp acutalata in the world.
Stabilization of dunes by European beachgrass (Ammophila arenaria) (Grenier 1991).
Propagation research determined that plants do not form adventitious roots, suggesting that stem cuttings would not be successful. Seed germination and transplanting techniques should be focus for reintroduction techniques (Kaye and Greenlee, 1995).
Seeds germinate best with the fruit husk removed (Kaye, 1999)
Some seed lots require cold pre-treatment, while others may not. Germination requirements for this species differ from year to year, possibly due to annual variation in environmental conditions during maturation and while fruits are on the ground, prior to collection (Kaye, 1999).
Field propagation studies indicate that 30% of seeds sown between the surface and 1 inch (3 cm) deep in the sand germinate and establish as seedlings, while none buried 4 inches (10 cm) deep germinate and establish. Results indicate that scattering seeds on the surface or lightly raking them in is the best technique. Seeds are much easier to sow than plants are to transplant, so larger numbers of pink sandverbena plants can potentially be introduced, possibly outweighing the predictability of transplants (Kaye et al 1998, Kaye 1999).
Germination trials conducted at The Berry Botanic Garden resulted in 0% germination with 8 weeks of cold stratification followed by alternating 50F/68F (10/20C) treatment, but 17% under 8 weeks of cold stratification followed by constant 68F (20C). Without cold stratification, 20% germination was achieved with either a constant 68F (20C) or alternating 50F/68F (10/20C) temperatures (BBG File).
The seedling establishment rate using 50,000 seeds scattered in the sand per site, while low in absolute terms, was substantially greater than attempts with 5,000 seeds per site (0.54% establishment rate as opposed to 0.017%) (Kaye 2000).
Plants were very successful on dredged sand brought up and deposited on the beach. The nutrient-rich sand smothered the previously dominant European beachgrass (Amophila arenaria), thereby creating suitable habitat for the pink sandverbena (Kaye and Greenlee, 1995).
Transplanted individuals placed singly, or in clusters of three or six are equally capable of growth, flower production and seedling production the following year. They often grow larger than plants from the wild. Transplanting wild seedlings in the fall failed to produce vigorous plants (Kaye et al. 1998).
Propagation observations determined that the majority of individuals are annuals, but a small amount (3%) continued to grow the following year into large plants and produce several thousand seeds (Kaye and Greenlee, 1995).
Second year plants often produce more seeds than first year, and therefore may be especially important in re-introduction efforts (Kaye et al, 1998).
Low density transplants grow larger in the first year than high density plantings, and mortality is unaffected by density (Kaye 1999).
Natural population sizes vary widely over time and space. The total number of tagged plants surviving to reproduce varied from 3.9 - 30.5 % between years. The average plant size varied from 3.7 inches (9.4 cm) to 20.9 inches (53.0 cm). Inflorescence number varied from one to 153 (Kaye 1999).
A study was conducted in which seedlings were transplanted onto dredged sand and old sand with and without fertilizer added. Some plots were weeded and others were not. Fertilizer has a stronger positive effect in fresh (dredged) sand, while weeding helped more on older substrates. While fertilizer addition caused a significant difference in flowering on fresh sand, the improvement was relatively small. In general, fresh sand provided the most favorable conditions for pink sandverbena growth (Kaye 1999).
On coastal sand dunes, plants increase in abundance and diversity (species richness) as time since dredged-sand deposition increases (Kaye 1999).
Pink sandverbena tends to decline with substrate age, especially after 3 years (Kaye 1999)
Transplants and plants from field-sown seed can reproduce and recruit substantial numbers of seedlings the following year (Kaye 1999). Even with initial success with plant establishment from seed, long term population establishment is difficult to achieve. By the second year following reintroduction efforts, no plants were present at four re-established sites and only one or two plants were present at three other sites (Kaye 2000).
One re-established population has done remarkably well. More than 1700 plants were established in 1997, and 411 plants germinated the following year. In 1999, more than 50,000 plants had established and in 2000 the population consisted 33,916 plants in the monitored area plus an additional 15,000 plants throughout the rest of the spit (Kaye 2000).
Eleven natural and four reintroduced A. umbellata ssp. breviflora populations (232 individual plants total) were sampled and genetically analyzed using Inter Simple Sequence Repeat (ISSR) screening. Most populations had relatively high levels of genetic diversity with heterozygosity ranging from 0.13 to 0.26 and means of 0.19 and 0.15 for natural and reintroduced populations, respectively. The two largest reintroduced populations had levels of diversity comparable to the source population, while the other two reintroduced populations were genetically impoverished (McGlaughlin 2000).
Restricted recreation and vehicle use of dunes at various sites.
One existing pink sandverbena population was protected from burial by sand dredged from a nearby harbor by moving material down the beach away from the population. In each subsequent dredging, sand has been placed in a new section of the beach without damaging existing or re-introduced populations. Addition of dredged sand has created new pink sandverbena habitat by burying European beachgrass (Kaye 1999).
A 2000 reintroduction through transplanting averaged 44% survival rate in the first year, however offspring from transplants were uncommon one year after the reintroduction effort (Kaye 2000).
Plants that grow close to shore (on the upper beach) were more likely to thrive short-term, but plants in the foredune were more likely to survive fall and winter storms. Competition from dune grasses in the foredune, however, can be detrimental to pink sandverbena growth. A strategy that places transplants among both habitats may improve over-all success (Kaye 2000).
Seed from 3 Oregon populations are currently banked at The Berry Botanic Garden.
List as threatened in CA, and British Columbia (Vrilakas 1988).
Restrict access to population areas (Vrilakas 1988).
Remove Ammophila arenaria (European beachgrass) or control with rock salt, herbicide, manual pulling and fire (Vrilakas 1988).
Continue research on reintroduction through seeding at a higher level (50,000-100,000 seeds instead of 5,000), as it is less time- and resource-consuming than transplantation (Kaye 1997a).
Study hybridization between Abronia umbellata ssp. breviflora and A. umbellata ssp. umbellata (Vrilakas 1988).
Utilize computer models based on natural population dynamics, population establishment success, and interactions between populations and unoccupied suitable habitat to simulate population dynamics and to determine the viability of actual individual populations (Kaye 2000).
Utilize computer programming to model meta-populations and determine the chance of extinction over time (Kaye 2000).
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