|BOTANICAL ELECTRONIC NEWS|
|No. 348 April 26, firstname.lastname@example.org||Victoria, B.C.|
Cody (1979) and Porsild and Cody (1980) reported Nymphaea tetragona Georgi ssp. leibergii (Morong) Porsild in Northwest Territories (NWT) on the basis of a specimen collected on an island in the Simpson group in Great Slave Lake, 40 miles NE of Resolution (E. A. Preble 243, US, see Porsild 1939). Recently Wiersema (1996, 1997) has recognized two taxa in North America: Nymphaea leibergii Morong, which occurs mostly in eastern and central North America, and Nymphaea tetragona, which occurs in northwestern North America and Eurasia. Nymphaea tetragona is distinguished by a prominent ridge at the insertion of the sepals which is lacking in N. leibergii (Wiersema 1997a,b, Crowe and Hellquist 2000, Hellquist 2003). Previously all small white water- lilies in North America were referred to N. tetragona ssp. leibergii.
Wiersema reported Nympaea tetragona from NWT on the basis of a specimen collected from a small lake 25 miles from Yellowknife on the road to Fort Rae (Murdy s. n., 1 Aug. 1961, KNK). As a result of the split N. tetragona is actually a new record for NWT (not adequately explained in the recent compilation of additions - see Catling et al. 2005). Questions have arisen regarding the the identity other collections, specifically whether they are referable to N. tetragona or to N. leibergii (which occurs close to the NWT border in British Columbia) and is also present in northern Saskatchewan (Wiersema 1997). An examination of all the NWT collections readily available (see below) revealed that both N. leibergii and N. tetragona occur in NWT.
The identity of the Preble collection (cited above) at the US National Museum has not been checked. The distribution map produced by Hultén and Fries (1986) shows four locations in NWT, one being the Resolution site (Preble), the two northernmost being near Yellowknife and the other being near to Fort Smith and possibly based on a specimen collected right on the Alberta- NWT border (17 July 1950, Cody & Loan 4500, DAO) cited by Wiersema (1996) under Alberta. These same four locations were shown by McJannet et al. in 1995. The basis for the locations shown near Yellowknife may be the published reports of Thieret (1963, 1964) evidently overlooked by Porsild and Cody (1980). In his 1963 catalogue of the flora of the Yellowknife highway, Thieret noted under Nymphaea tetragona Georgi ssp. leibergii (Morong) Porsild that it was: "seen only once, in a muck bottom lake, among Nuphar, mile 35.5 S [meaning 35.5 miles west of Yellowknife] 8328. In full flower on July 30." This specimen is presumably at F (Field Museum in Chicago) where most of the collections from Thieret's survey are deposited. In his 1964 description of vegetation along the Yellowknife highway Thieret states: "...Ray Murdy tells me that in 1963 he observed the species "here and there" in almost all of the medium to large lakes he studied along the highway from mile 10 S to mile 39 S." Thus of the 4 locations plotted, specimens are known from 3, and 2 of the specimens are referable to N. tetragona based on examination by Wiersema.
Four recent collections of small water-lilies are also attributable to Nymphaea tetragona including: pond no. 2, W of Yellowknife at 62.4792 ̊N, -114.7280 ̊W, P. M. Catling & M. Fournier, 21 July 2003 (DAO); pond no. 124, W of Yellowknife at 62.5625 deg. N, -115.0868 deg. W, P. M. Catling & M. Fournier, 21 July 2003 (DAO); with Chara in pond in Spruce woods, 15 km N of Fort Simpson at 61.9124 deg. N, -121.7005 deg. W, P. M. Catling 102 & B. Kostiuk, 24 July 2004 (DAO); shallow wetland, Deh Cho area, 61.6225 deg. N, -121.1002 deg. W, G. Allen 91, 10 Aug. 2004 (DAO).
On the other hand, one recent collection is referable to Nymphaea leibergii: Camsell Ferry at 62.1567 deg. N, 122.4908 deg. W, L. Kershaw 15, 2003 (DAO).
The recent report of Nymphaea leibergii (sub N. tetragona ssp. leibergii) from Alaska (Cook and Roland 2002) is presumably an error based on material of N. tetragona since N. leibergii does not occur in Alaska (Wiersema 1997) where N. tetragona is widespread.
Rare annual plants may have widely fluctuating populations, may or may not have abundant seed banks, are often adapted to disturbances, and may rely on metapopulations for their long term persistence. These characteristics influence the way we design rare plant surveys, assess the status and or threats, and design recovery plans or mitigation. Surveys and assessments should include historical locations, locations with few individuals, and all suitable habitat (even if empty) in close proximity to known populations. Information on seed bank size and viability, and dispersal distances, is needed to assess the status and potential threats to rare annual plants.
Rare plants typically have few occurrences and may have small populations. These small populations are more susceptible to stochastic events (Primack 2002), often have low pollination rates (Dieringer 1999; Wolf 2001), decreased seed viability or seed production (Fischer and Matthies 1998; Wolf 2001; Watson, Uno, McCarty and Kornkven 1994; Brys et al. 2004), and low genetic variation (Ellstrand and Elam, 1993; Primack 2002; Watson et al. 1994; Hackney and McGraw 2001).
The importance of small isolated populations, on the long term persistence of a species, depends on how the species reproduces, whether it needs insects to assist in pollination, and the characteristics of the gene pool (Holderegger and Schneller 1994; Heschel and Paige 1995; Sipes and Tepedino 1995; Husband and Barrett 1996; Schemske, Husband, Ruckelshaus, Goodwillie, Parker and Bishop 1994). Generally, this information is unavailable for plant species at risk in Alberta, many of which are peripheral to core populations. Species specific information may be found in publications about populations in other jurisdictions, but there is no guarantee that the information will be applicable to peripheral populations as the genetics may be distinctly different (Lesica and Allendorf 1995), nor can one confidently extrapolate from more common species in the same genus (Kunin and Shmida 1997).
Rare annual plants add a layer of complexity to the equation. Annual plants only grow for one year, and a large portion of the life cycle is seed. Plant numbers often fluctuate wildly from year to year depending on the seed production in previous years, germination of seedlings and environmental conditions (e.g. timing and amount of rainfall) (Fischer and Matthies 1998; Harrison, Maron and Huxel 1999; Primack 2002; Primack and Miao 1992). In addition, annual plants are often adapted to disturbances such as fire, land slides, grazing or flooding, and are often out competed in later successional stages (Hayes and Holl 2003; Watson et al. 1994; Harrison et al., 1999). For example, in Alberta we have found woollyheads (Psilocarphus elatior), smooth Boisduvalia (Boisduvalia glabella), and chaffweed (Anagallis mimina) only when spring or summer precipitation is sufficient to create ponding in ephemeral prairie wetlands. Additionally, the wetland area must be grazed sufficiently that taller perennial species are kept short and mineral soils are exposed.
Of the seed produced each year by annual plants, some portion is non-viable, some is lost to seed predators, some form seedlings, and some is stored in the seed bank. Seed bank and germination ecology are especially important to annual plants, but information on them is extremely difficult and time-consuming to gather (Elzinga, Salzer and Willoughby 1998; McCue and Holstford 1998).
Most annuals have small seeds. Small seeds tend to remain viable longer than large seeds (Guo, Rundel and Goodall 1999) but the seed may or may not persist in the seed bank (Watson et al. 1994), and the seed may be abundant or rare, depending on the species (Guo, Rundel and Goodall 1999).
The presence of abundant seed in the seed bank influences the genetics and hence the fitness of a population. Seeds germinating from the seed bank are "composed of progeny produced in many generations and represent migration from the past" (McCue and Holtsford 1998). The seed bank may have a broader genetic diversity than the current population of plants, and therefore may compensate for the harmful consequences of genetic drift or inbreeding, characteristic of small populations (McCue and Holtsford 1998; Ellstrand and Elam 1993).
Many annual plant populations vary widely in size from year to year depending on environmental conditions, such as moisture or disturbance. The degree of fluctuation is recognized as an important criteria in assessing the status of animal and plant species at risk (IUCN criteria B and C). For annual plants, fluctuation in plant numbers from year to year can be a substantial risk factor if there is no dormant seed bank, for the very small populations at the low point of the fluctuation have a high risk of losing valuable genes or losing entire populations. If, however, only a portion of the seed within the seed bank germinates in a given year then the fluctuating population may not be a serious risk factor. In some cases, what appears to be a local extinction may simply be prolonged seed dormancy (McCue and Holtsford 1998; Lesica and Steele 1994). This ability to persist as dormant seeds is an "escape in time" from environmental harshness (Harrison et al. 1999) that plants use, as opposed to an "escape in space" that mobile animals use. It is an effective survival mechanism, but makes the task of assessing the status of an annual species more difficult for botanists.
Plant populations move. Very slowly. Plant populations that are found in isolated patches rely on the movement of pollen or seeds within metapopulations to maintain their genetic diversity. (A metapopulation is made up of a shifting mosaic of populations linked by some degree of migration (Primack 2002)). Even common plant species suffer reduced seed set and smaller populations when isolated (Lienert and Fischer 2003; Soons and Heil 2002), and species with small populations, short life cycles, or high habitat specificity are even more susceptible (Fischer and Stöcklin 1997). Some species, however, seem to have adapted to small populations and limited gene flow (Holderegger and Schneller 1994). Metapopulations may be structured around one central core population that provides pollen or seed for numerous smaller populations. If the core population is eliminated, then the surrounding populations will also go extinct (Primack 2002). In addition, empty but suitable microsites might be necessary for long-term persistence of a metapopulation in a balance between local extinctions and recolonizations (Hanksi Moilanen and Gyllenberg 1996; Primack 2002).
Long distance dispersal of seeds, however, is often rare and highly episodic, depending on a combination of unusual occurrences (Wolf 2001). Local populations, especially those in clusters, are more likely to produce seeds, and are more likely to recolonize a vacant habitat (Wolf 2001). Populations of annual plants farther than 100 m (Primack and Miao 1992) or 300 m (Harrison et al. 1999) from each other, have higher rates of extinction and fewer recolonization events than close populations. Primack and Miao (1992) conducted seeding studies and concluded that "Animals walking and digging through the soil, plus the action of wind and water flow, apparently do not move seeds any significant distance once they have landed on the soil surface". It appears that while pollination may occur over large areas, seed dispersal is restricted to small areas in most years.
Meta-population theory is confounded by two additional factors when dealing with annual plants. Firstly, when species have persistent seed banks, or are capable of long term vegetative reproduction, the local extinction and recolonization rates are obscured, and it may be difficult to discern the dispersal rates in space versus time (Wolf 2001). Secondly if nearby populations fluctuate independently, then there is more potential for rescue and recolonization than if populations within dispersal range of one another behave synchronously (Harrison et al. 1999). Asynchronous populations take advantage of "escape in time" where populations produce seed in different years under different conditions. This means that a serious large scale event such as a large flood, fire, or hail storm would only eliminate the seed production from one population rather than the entire metapopulation.
Survey techniques must be adapted to the characteristics of rare annual plants. Because a large portion of life cycle is as seed, the number of individuals visible above ground may fluctuate widely and are not easy to identify. Surveys should always include a thorough search of historical records and a survey of the historical locations. The timing of the surveys should be flexible to reflect the moisture conditions and the disturbance regimes required by the species in question. Potential habitat should be examined in several years, under different climatic conditions, since "the absence of individuals above ground in any given year does not necessarily mean that the population is truly extinct" (Harrison et al. 1999). All potential habitat in close proximity to the survey area should be surveyed, for it is often the existence of at least a portion of the metapopulation that will ensure the long-term survival of the species or subpopulation.
Because annual plants are often associated with disturbances, surveys should carefully inspect these areas, even though we intuitively associate rare plants with undisturbed habitats. In Southern Alberta, we have found American pellitory (Parietaria pensylvanica) under shrubs where cattle gather for shade and churn the soil. We have also found smooth boisduvalia and chaffweed under irrigation pivots in cultivated fields, and sand verbena is found in open, shifting sand dunes.
The assessment of threats or status of rare annual plants is difficult. Most research on conservation biology has been done for animals, and there has been little work done on the role of metapopulations and seed banks for rare annual plants (Ellstrand and Elam 1993; McCue and Holtsford 1998). Little work has been done on plants that are rare in Alberta, so we don't know if a species has a persistent seed bank, how long the seeds lie dormant, or how far the seeds are dispersed, much less the reasons for rarity.
Based on the previous discussion several points should be considered when assessing the threat or status of a rare annual plant species:
The Alberta Endangered Species Conservation Committee and The Committee on the Status of Wildlife in Canada use the criteria established by the International Union for the Conservation of Nature (IUCN 2001) to assess the status of plants and animals at risk. One of the criteria (B - extent of occurrence) considers extreme fluctuations in the extent of occurrence, area of occupancy, number of locations or subpopulations, or number of mature individuals. The number of mature individuals is defined as " the number of individuals known, estimated or inferred to be capable of reproduction. When estimating this quantity the following points should be borne in mind: Where the population is characterised by natural fluctuations the minimum number should be used . ... For plants with seed banks use the juvenile period + either the half-life of seeds in the seed bank or the median time to germination. Seed bank half-lives commonly range between <1 and 10 years."
Primack (2002) suggests that for annual plants the effective population size should be somewhere between the lowest and the highest number of breeding individuals, and proposed using the Harmonic Mean of several years data. Ne = t/(1/N1 + 1/N2 + ... + 1/Nt). McCue and Holtsford (1998) point out that the impact of even a small number of seeds in the seed bank can have a significant impact on the effective population, and suggest that the Ne should include an estimate of viable seeds/population area. This, however, assumes that you know the size of the seed bank and how long the seeds persist.
Without data on the seed bank, we run the risk of under- estimating the effective population (by ignoring a viable seed bank) or under-estimating the impacts of population loss (by assuming that a fluctuating population will have a seed bank, and is therefore safe).
Mitigation of impacts to rare plants should always concentrate on protecting existing populations rather than using experimental techniques to establish new populations (Bush 2001). Successful introductions likely depend "on the fortuitous combination of a particular genotype in a suitable microsite in a particular year" (Primack and Miao 1992). If experimental introductions are attempted, they should involve seeding numerous potential microsites in several years (Primack and Miao 1992).
In summary, mitigation of human impacts to rare annual plant populations should:
Monitoring is essential to any mitigation project that involves disturbing rare communities and rare plant species. Monitoring is the only way to assess if the mitigation was successful or not, and to make informed choices about future mitigation strategies. Successful mitigation techniques can therefore be used with greater confidence and unsuccessful ones reevaluated or avoided.
Many of the techniques recommended for rare plant mitigation are experimental, and little is known about the biology and reproductive capacity of individual species (Allen 1994; Primack 2002; Falk, Millar and Olwell 1996). To account for the natural fluctuations in populations, monitoring should be done regularly and for several years. Remember, that absence might be the result of prolonged dormancy not extinction.
When monitoring for recovery plans, data should be collected from years when the plants are absent as well as from years when they are present, to fully describe their response to environmental fluctuations. When monitoring to determine if mitigation was successful (assuming the budget is very limited), it may be appropriate to survey in selected years (3 years in 5, or 5 in 12) to take advantage of years with good growing conditions (provided you understand what conditions are needed for germination). In either case, the results should be published so that we can increase our understanding or rare plant biology and mitigation.
Rare annual plants have a suite of unique characteristics that affect our ability to assess their status and to develop recovery and mitigation plans. Rare annual plant species may naturally experience large fluctuations in plant numbers, and may have dormant seed banks which are difficult to assess in terms of size and viability. In addition, they may rely heavily on the presence of nearby populations and disturbance for their long-term persistence. These characteristics must be included into the design of field surveys, into the thought processes behind assessing the status and the threats to the population, and when designing mitigation and monitoring programmes.
Coast Mountain Field Institute (CMFI) is beginning it's second year of programming in a few weeks. Last year CMFI was established as a non-profit organization designed to provide field- based educational opportunities on a wide range of topics, from botany to natural and cultural history, nature- related arts, family-oriented natural history programs, to stewardship and conservation. Courses are meant for a wide variety of audiences, and feature small group sizes, interesting topics, and beautiful locations. Instructors include some of BC's most renowned biologists and naturalists. The main goals for CMFI are to help enhance people's knowledge and understanding, while inspiring a continuing appreciation, for the province's wild landscapes, and to develop a desire to foster stewardship for future generations.
We have designed eighteen courses for 2005. Botany related courses include a 2 day program on Salt Spring Island examining Garry Oak Ecosystems with Terry McIntosh (May 14 -15). Other botany courses include a wildflower investigation at Manning Park, Plants for Hikers on Keats Island, and the a fungi workshop on the Sunshine Coast (not quite botany, but close enough for us). Examples of other courses offered for 2005 include Okanagan Songbird Migration led by Dick Cannings, BC Rivers: From Urban To Wild led by Mark Angelo, Danny Catt, and Bob Gunn, and Ethnoecology of the Straits Landscape, led by Dr. Brenda Beckwith, Cheryl Bryce, and Marilyn Lambert. The programs promise to be interesting, informative, and relevant. For a complete listing of our courses and for more information about our institute, please visit our website at http://www.cmfi.ca/.
The eruption of Mount St. Helens on May 18, 1980, had a momentous impact on the fungal, plant, animal, and human life from the mountain to the far reaches of the explosion's ash cloud and mudflows. Although this intense natural event caused loss of substantial life and property, it also created a unique opportunity to examine a huge disturbance of natural systems and their subsequent responses. Based on one of the most studied areas of volcanic activity, this book synthesizes the ecological research that has been conducted for twenty- five years since the eruption.
Research from geology as well as plant and animal ecology has been integrated in this unprecedented look at the complex interactions of biological and physical systems in the response of the volcanic landscape. Lessons from the volcano inform our larger understanding of ecosystem disturbances, natural processes, and the impact of land-use practices. Included are results of significant and long-term research on vegetation, mycorrhizae, plant and animal interactions, arthropods, amphibians, mammals, fish, lakes, nutrient cycling, geomorphology, and environmental management. This comprehensive account will be of value to those interested in natural history, ecology, disturbance, conservation biology, limnology, geoscience, and land management. Questions about what actually happens when a volcano erupts, what the immediate and long-term dangers are, and how life reasserts itself in the environment are discussed in full detail.
In the great BEN tradition, as explained in Adolf Ceska's "Short History of BEN" (No. CCXLVII April 1, 2000), I learned about RSS ("Really Simple Syndication") as a way of providing news feeds and am incorporating it in a number of my web sites. The technology is growing rapidly in popularity this year. Major journals, newspapers, blogs and other websites have incorporated RSS as a means of communication, written in a simplified version of XML (the extensible form of HTML -- the language of the web). RSS feeds from many sites can be consolidated into a collection of news that is read by a special reader, an RSS reader. Anyway, BEN now has an RSS feed! The feed is linked at the BEN web site by an orange tag that says "XML" (the traditional RSS indicator). If you import this into an RSS reader, then you will have BEN articles as news items. With some RSS readers, you can click the orange icon, drag and drop it, or copy the link into an import utility. Is this of any practical use? -- you be the judge.
Daniel Mosquin of the University of British Columbia Botanical Garden and Centre for Plant Research has crafted the BEN newsfeed into his site on the following web page: http://www.ubcbotanicalgarden.org/resources/botanicalelectronicnews.php His site uses the newsfeed in building part of the website and is updated whenever the newsfeed is changed, providing breaking BEN news, for instance. If you decide to see what an RSS newsreader is, I would suggest a free one (e.g., Lektora at http://www.lektora.com/ is a good one, which becomes an integral part of Firefox or Internet Explorer web browsers and comes with about 30 pre-configured feeds) before you buy one.
For more, here is my introduction to RSS in my Scott's Botanical Links site: http://www.ou.edu/cas/botany-micro/bot-linx/mar05.shtml#Mar29
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