Mexican Mosquito Fern (Azolla Mexicana)

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COSEWIC Assessment and Update Status Report

on the

Mexican Mosquito-fern Azolla mexicana

in Canada

THREATENED 2008

COSEWIC status reports are working documents used in assigning the status of wildlife species suspected of being at risk. This report may be cited as follows:

COSEWIC. 2008. COSEWIC assessment and update status report on the Mexican Mosquito-fern Azolla mexicana in Canada. Committee on the Status of Endangered Wildlife in Canada. Ottawa. vi + 35 pp. (www.sararegistry.gc.ca/status/status_e.cfm).

Previous reports:

COSEWIC. 2000. COSEWIC assessment and update status report on the Mexican mosquito-fern Azolla mexicana in Canada. Committee on the Status of Endangered Wildlife in Canada. Ottawa. vi + 11 pp.

Martin, M.E. 2000. Update COSEWIC status report on the Mexican mosquito-fern Azolla mexicana in Canada, in COSEWIC assessment and update status report on the Mexican mosquito-fern Azolla mexicana in Canada. Committee on the Status of Endangered Wildlife in Canada. Ottawa. 1-11 pp.

Brunton, D.F. 1984. COSEWIC status report on the mosquito fern Azolla mexicana in Canada. Committee on the Status of Endangered Wildlife in Canada. Ottawa. 36 pp.

Production note: COSEWIC would like to acknowledge Brian Klinkenberg for writing the status report on the Mexican Mosquito-fern Azolla mexicana in Canada, prepared under contract with Environment Canada, overseen and edited by Erich Haber, Co-chair, COSEWIC Vascular Plants Specialist Subcommittee.

For additional copies contact:

COSEWIC Secretariat c/o Canadian Wildlife Service Environment Canada Ottawa, ON K1A 0H3

Tel.: 819-953-3215 Fax: 819-994-3684 E-mail: COSEWIC/[email protected] http://www.cosewic.gc.ca

Également disponible en français sous le titre Ếvaluation et Rapport de situation du COSEPAC sur l’azolle du Mexique (Azolla mexicana) au Canada – Mise à jour.

Cover photo: Mexican Mosquito-fern — Photo by Brian Klinkenberg.

©Her Majesty the Queen in Right of Canada, 2009. Catalogue No. CW69-14/568-2009E-PDF ISBN 978-1-100-12452-0

Recycled paper

COSEWIC Assessment Summary

Assessment Summary – November 2008

Common name Mexican Mosquito-fern

Scientific name Azolla mexicana

Status Threatened

Reason for designation This tiny floating aquatic fern of south-central British Columbia is restricted to 8 small water bodies where its populations undergo periodic fluctuations in numbers of individuals. Two populations and their habitat have been lost in recent years due to construction activities with most of the extant populations occurring adjacent to major highways or a railway where they are at potential risk from maintenance activities, including the use of chemicals such as road salt.

Occurrence British Columbia

Status history Designated Threatened in April 1984. Status re-examined and confirmed in April 1998, May 2000, and November 2008. Last assessment based on an update status report.

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COSEWIC Executive Summary

Mexican Mosquito-fern Azolla mexicana

Species information

Mexican Mosquito-fern Azolla mexicana is a tiny floating aquatic fern found in wetlands and small wet areas. Individual plants range in size from 1-2 cm in length. Leaves are tiny and overlap like shingles. Spore-producing structures, borne below the water surface, are present in the Canadian populations. Roots are simple and short. Plants usually have three “floats”. This species forms extensive green or red mats on the water surface.

Distribution

The natural range of Mexican Mosquito-fern is North, Central and South America (from Peru, northern Bolivia and Brazil north). In Canada, it is restricted in occurrence to British Columbia, where it occurs at the northern tip of its range. The eight extant British Columbia populations occur in three regions: the Little Fort area, the Shuswap Lake area, and Vernon. The extent of occurrence is 5400 km2 and the area of occupancy for the small fragmented water bodies is 11 km2 based on a 1 x 1 km grid and 40 km2 based on a 2 x 2 km grid.

Habitat

Mexican Mosquito-fern is a wetland species of sheltered still waters and is found in ponds, ditches, oxbow ponds, and lakeshores. It grows best in 50% sunlight, and is tolerant of semi-shade conditions. In BC, it is found in sites with pH ranging from 6.5- 8.1, although it is tolerant of pH ranging from 3.5 to 10.

Biology

This aquatic fern grows in a symbiotic relationship with a species of blue- green alga (a cyanobacterium) Anabaena azollae. Primary reproduction is through fragmentation of plants. Secondary reproduction is sexual through spore production. This is a heterosporous fern: two types of spores (of different sizes and appearance) are produced that fall to the bottom of water bodies and eventually germinate, producing new plants. Dispersal is by wind, waterfowl, and accidentally by humans.

Population sizes and trends

Ten populations of this species have been confirmed from British Columbia. Two of these are now extirpated as a result of road construction and urban development. In spite of this, there has been an increase in known populations for this species since the 1984 status report, which reported only four sites for the species. Populations fluctuate dramatically from year to year in areal extent. Because of this, population trends are unknown and further study over several years is needed.

Limiting factors and threats

Mexican Mosquito-fern is naturally limited by factors such as water chemistry and temperature, which restrict its range in British Columbia. Threats to the populations include road repairs and construction, housing / urban development, accidental spills on roads and railways (which can influence water chemistry and could cause complete population die-off), invasive species, and eutrophication of sites.

Special significance of the species

This species is rare in BC and Canada and is found in British Columbia at the northern limits of its range. As populations peripheral to the main species range, the Canadian populations could be important to the species long-term survival in the face of climate warming. The species is economically important and is cultivated in many countries around the world as a green fertilizer, due to the presence of the symbiotic nitrogen-fixing cyanobacterium, and for use as a nutritional supplement in livestock feed.

Existing protection or other status designations

One population of Mexican Mosquito-fern occurs within a provincial park. Other populations have no existing formal protection. COSEWIC assessed Mexican Mosquito-fern as Threatened in 2000.

COSEWIC HISTORY The Committee on the Status of Endangered Wildlife in Canada (COSEWIC) was created in 1977 as a result of a recommendation at the Federal-Provincial Wildlife Conference held in 1976. It arose from the need for a single, official, scientifically sound, national listing of wildlife species at risk. In 1978, COSEWIC designated its first species and produced its first list of Canadian species at risk. Species designated at meetings of the full committee are added to the list. On June 5, 2003, the Species at Risk Act (SARA) was proclaimed. SARA establishes COSEWIC as an advisory body ensuring that species will continue to be assessed under a rigorous and independent scientific process.

COSEWIC MANDATE The Committee on the Status of Endangered Wildlife in Canada (COSEWIC) assesses the national status of wild species, subspecies, varieties, or other designatable units that are considered to be at risk in Canada. Designations are made on native species for the following taxonomic groups: mammals, birds, reptiles, amphibians, fishes, arthropods, molluscs, vascular plants, mosses, and lichens.

COSEWIC MEMBERSHIP COSEWIC comprises members from each provincial and territorial government wildlife agency, four federal entities (Canadian Wildlife Service, Parks Canada Agency, Department of Fisheries and Oceans, and the Federal Biodiversity Information Partnership, chaired by the Canadian Museum of Nature), three non-government science members and the co-chairs of the species specialist subcommittees and the Aboriginal Traditional Knowledge subcommittee. The Committee meets to consider status reports on candidate species.

DEFINITIONS (2008) Wildlife Species A species, subspecies, variety, or geographically or genetically distinct population of animal, plant or other organism, other than a bacterium or virus, that is wild by nature and is either native to Canada or has extended its range into Canada without human intervention and has been present in Canada for at least 50 years. Extinct (X) A wildlife species that no longer exists. Extirpated (XT) A wildlife species no longer existing in the wild in Canada, but occurring elsewhere. Endangered (E) A wildlife species facing imminent extirpation or extinction. Threatened (T) A wildlife species likely to become endangered if limiting factors are not reversed. Special Concern (SC)* A wildlife species that may become a threatened or an endangered species because of a combination of biological characteristics and identified threats. Not at Risk (NAR)** A wildlife species that has been evaluated and found to be not at risk of extinction given the current circumstances. Data Deficient (DD)*** A category that applies when the available information is insufficient (a) to resolve a species’ eligibility for assessment or (b) to permit an assessment of the species’ risk of extinction.

* Formerly described as “Vulnerable” from 1990 to 1999, or “Rare” prior to 1990. ** Formerly described as “Not In Any Category”, or “No Designation Required.” *** Formerly described as “Indeterminate” from 1994 to 1999 or “ISIBD” (insufficient scientific information on which to base a designation) prior to 1994. Definition of the (DD) category revised in 2006.

The Canadian Wildlife Service, Environment Canada, provides full administrative and financial support to the COSEWIC Secretariat.

Update COSEWIC Status Report

on the

Mexican Mosquito-fern Azolla mexicana

in Canada

2008

TABLE OF CONTENTS

SPECIES INFORMATION...... 4 Name and classification...... 4 Morphological description ...... 5 Genetic description...... 6 Designatable units ...... 9 DISTRIBUTION...... 9 Global range ...... 9 Canadian range ...... 10 Extent of occurrence...... 11 Area of occupancy...... 12 HABITAT ...... 12 Habitat requirements ...... 12 Habitat trends ...... 15 Habitat protection/ownership ...... 15 BIOLOGY ...... 15 Life cycle and reproduction...... 16 Herbivory ...... 16 Physiology ...... 17 Dispersal...... 18 Interspecific interactions ...... 18 Adaptability ...... 18 POPULATION SIZES AND TRENDS...... 19 Search effort ...... 19 Abundance, fluctuations and trends...... 20 Rescue effect...... 22 LIMITING FACTORS AND THREATS ...... 23 Limiting factors...... 23 Threats ...... 23 SPECIAL SIGNIFICANCE OF THE SPECIES ...... 24 EXISTING PROTECTION OR OTHER STATUS DESIGNATIONS ...... 24 TECHNICAL SUMMARY...... 26 ACKNOWLEDGEMENTS AND AUTHORITIES CONSULTED...... 6 Authorities consulted ...... 6 INFORMATION SOURCES ...... 6 BIOGRAPHICAL SUMMARY OF REPORT WRITER ...... 10 COLLECTIONS EXAMINED ...... 10

List of Figures Figure 1. Mexican Mosquito-fern, photo by Brian Klinkenberg...... 5 Figure 2. Canadian and BC distribution of Mexican Mosquito-fern...... 6 Figure 3. North American distribution of Mexican Mosquito-fern...... 10 Figure 4. Mexican Mosquito-fern on the surface of an oxbow near Little Fort...... 13 Figure 5. Mexican Mosquito-fern completely covers the pond ...... 14

List of Tables Table 1. Mexican Mosquito-fern populations in British Columbia ...... 7

SPECIES INFORMATION

Name and classification

Scientific Name: Azolla mexicana Schlecht. & Cham. ex K. Presl. English Common Name: Mexican Mosquito-fern French Common Name: Azolle du Mexique Family Name: Azollaceae Major Plant Group: Fern

Taxonomic circumscription of the genus Azolla is considered difficult and controversial by many researchers (Zimmerman et al. 1989; Pereira et al. 2001; Evrard and Van Hove 2004; Ceska pers. comm. 2005; Reid et al. 2006 and others). The most commonly accepted classification follows the work of Svenson (1944), who recognized seven species globally, and four New World species: Azolla caroliniana, A. filiculoides, A. mexicana, and A. microphylla. Difficulty is encountered when trying to identify sterile specimens lacking spores.

Recently, several researchers have reassessed the species of Azolla with varying outcomes (e.g., Zimmerman et al. 1989; Pereira et al. 2001; Reid et al. 2006). None has resolved the taxonomic difficulties and a clear picture has yet to emerge. Reid et al. (2006) indicate that cytology of the group has not helped because all species of Azolla are 2n = 44. These authors also indicate that initial circumscriptions of the species, and initial illustrations, were not based upon type specimens, and this has led to some confusion. Added to this is the natural variation in the species, and the environmental plasticity that is noticeable among populations, as well as the already-noted difficulty of working with sterile specimens (Zimmerman et al. 1989; Pereira et al. 2001; personal observation). This has led to much discussion about lumping species and reclassification.

However, the most recent DNA sequence work by Reid et al. (2006) has provided some insights. These authors have determined that Azolla mexicana is a good and distinct species. They have also determined that its lineage is identical to A. microphylla, and they recommend that the two species should be listed as a single species (A. microphylla, synonym A. mexicana). They cite experiments by Stergianou and Fowler (1990) that indicate that crosses between these two “species” yield normal offspring “which indicates conspecific status” (Reid et al. 2006, p. 537). However, a change in nomenclature and classification of these species is not yet in place.

For the purposes of this status report, A. mexicana is here recognized as a distinct species based on the taxonomic treatment by Svenson (1944) and the studies of Reid et al. (2006). Any taxonomic and nomenclatural update that results from their work may involve a future name change for this species. Regardless, this change in nomenclature would not affect the status of this species in Canada since A. microphylla is not known from North America.

Morphological description

Mexican Mosquito-fern is a tiny annual, aquatic, heterosporous1 fern that often forms extensive green or red-coloured mats in wetlands and small wet areas. It grows in a symbiotic relationship with the blue-green alga Anabaena azollae (a cyanobacterium), which lives in cavities on the dorsal lobes of Azolla leaves.

Plants are intricately branched with tiny overlapping leaves (Figure 1) and simple short roots, and range in size from 1-2 cm (Svenson 1944; Douglas et al. 2000; Martin In press). Upper leaf lobes are usually 0.7-0.9 mm long. Douglas et al. (2004, p. 302) describe the plants as “pinnately branched from a central axis, dichotomously branched only at the periphery of the plant, fronds overlapping like shingles.” Plants produce both micro- and mega-sporocarps (spore-bearing structures). A key character for separating Azolla species are the megasporangia, which are distinctively shallowly pitted at the base in A. mexicana, and are borne on short stalks on the undersides of floating lobes. These features are readily seen under a dissecting microscope. Generally, A. mexicana plants are larger and more compact than A. caroliniana, sporocarps are usually readily visible, and the floats2 on the leaves (usually three) are usually enlarged (Svenson 1944, Lomer pers. comm. 2007). A. filiculoides, the third Azolla species found in BC, has distinctively different megasporangia and is a much larger species than A. mexicana.

Figure 1. Mexican Mosquito-fern, photo by Brian Klinkenberg.

1 Having more than one kind of asexually produced spores 2 A structure that aids in the flotation of an aquatic organism (Answers.com).

Genetic description

There are no apparent ecological or behavioural barriers to gene flow in this species in British Columbia. No genetic information on this genus in BC is available. Although the distances separating the three groups of populations (~80 km, ~50 km and ~125 km—see Figure 2 and Table 1) probably preclude much genetic interaction among them, within each group of populations waterfowl movements may ensure a degree of interaction as occurs with other aquatic species (Figuerola 2002; Green et al. 2008).

Figure 2. Canadian and BC distribution of Mexican Mosquito-fern.

Table 1. Mexican Mosquito-fern populations in British Columbia

Locale Population Ownership/Protection Population description* Status status Little Fort 1) Little Fort, Round Top Private, owner unknown Covers pond (10 x 5m) 2005 Extant 2007. / North Road (July). In 1997, the population Thompson (CDC EO #25545) at this site was thriving River Area (500,000 plants), but in 2004 plants were not present. Plants present in both 2005 and 2007 (500,000 plants). 2) Little Fort, north of Dunn Peak Provincial Covers two large oxbows on Extant 2007. Not seen in (CDC EO #25458) Park (based on the west side of highway (30 x oxbow on east side of the Conservation Data Centre 18m). In some years (e.g., highway since prior to (4 km south of Mapping Service map) 2004, 2005, 2007) there is a 1997 (although previously Population 1) high density of plants: 10,000 observed there), lately plants per m2 for a total of only observed on the west over 1 million plants (Douglas side. 2004). The population has declined to zero visible plants in some years. It is impossible to determine trends from the annual fluctuations. It has persisted at this site for almost 25 years. 3) Little Fort, south of Private, owners unknown 3 sites in close proximity: Extant 2007. (CDC EO #25454) (possibly different owners 1) shallow pond at south end Site 1) no plants observed for each site) of pasture; (3 x 20m). In in 2007, plants observed (8 km south of 2004, this site consisted of in 2005; 2) had extensive Population 2) 40,000-60,000 plants in a 0.5 cover in 2005 and 2007 m ring around the edge of 3 but not observed m x 20 metre pond. 2) two previously (specifically in oxbow lakes on west side of 2004); 3) had no visible highway south of pasture; 20 plants in 2005, scattered x 150m very densely covered plants present in 2007. [over a million plants] 3) oxbow on east side of highway; 20 x 60m sparsely covered. In 1998, the eastern site consisted of 400-500 plants (40% coverage) over a 300 square metre area. In 2004, there was less than 1% coverage over a 100 square metre area at this site. 4) Darfield (CDC EO N.A. Known from a pond on the Extirpated. Douglas #25478) west side of the highway (2004) reported the site filled in by highway (13 km south of construction. Population 3) 5) Darfield, south of New Private, owners unknown Plants present in oxbow on Extant 2007. population. east side of highway only. 15 New population (2007) x 80m east, then 15 x 100+m on east side of highway, (3.6 km south of north/south; sparsely covered 3.6 km to the south of Population 4) [several 1000s of plants]. previously known Darfield population.

Locale Population Ownership/Protection Population description* Status status Shuswap Lake 6) Tappen/White Creek North Bay Indian First observed at this site in Extant 1997. Area (CDC EO #3786) Reserve 5 1974 on still water and Not visited in 2005 or stranded on the muddy bank. 2007; no plants observed (80 km from the Little In 1997, small numbers of in 2004 (Douglas 2004), Fort / North Thompson plants were observed among but habitat still intact. River populations) streamside vegetation along the lowest stretch of the creek and in a larger, but still small, concentration in a backwater at the first right- angled bend. 7) Salmon Arm (CDC EO Subpopulation 1: Plants throughout a 5 x 85m Not visited in 2005 or #3782) Switsemalph Indian wet area along RR tracks. 2007. Subpopulation Reserve with CPR Population size at mouth of observed in 2004 (9 km from interests and private lands. Salmon River unknown, but (Douglas 2004). Population 6) Possibly also Crown Land previously stated at 5 x 30m. (lakebed) (based on the Mexican Mosquito-fern has (Although 1.8 km Conservation Data Centre been observed in the area separates these two Mapping Service map) around the Salmon River at subpopulations, given the outlet to Salmon Arm, the likely level of Shuswap Lake, since 1890. interaction between In 1982, it was observed in them—waterfowl flying the shallow water of an from subpopulation 1 to oxbow lake, and in 1993, it subpopulation 2 on a was observed at the mouth of daily basis—they were the river. In 1994, it was considered as a single observed in several sites population. Also, around the lakeshore. Since over the years then it has been sporadically other intervening observed in several sites subpopulations have throughout the general area. sporadically been observed along the foreshore.) Subpopulation 2: Salmon Plants observed in a 3 x 2m Extant 2005. Arm foreshore Municipality area in 2005; no plants of Salmon Arm observed in 2007. 8) Sicamous (CDC EO Private, owner unknown None Extirpated. Douglas #3780) (2004) reported the site filled in. (26 km from Population 7) 9) Eagle River population Subpopulation 1: Cambie Azolla had been observed Extant 1997. (along Eagle River) (CDC here in a large slough since No plants observed since (9 km from EO #3784) 1972. Martin (1998) visited 1997 (2004, 2005, 2007) Population 8) Private, owner unknown the site frequently from 1987 but habitat still intact. to 1997 and always found the (Less than 1 km plants fully covering the separates the two pond. However, no plants subpopulations.) have been seen for the past couple of years (Douglas, 2004).

Locale Population Ownership/Protection Population description* Status status Subpopulation 2: Eagle None. Historical. No plants River / Solsqua observed since 1974. Private, owner unknown However, a possible collection by W. Schofield in 1997 from south side of highway could be from this site (but there is some ambiguity in the site description). Vernon 10) Vernon Creek Subpopulation 1: 2 10 x 20m patches in Extant 2007. Okanagan Avenue, pasture. Observed by M. Martin (50 km south of the Vernon (CDC EO #21875) (2007) Shuswap Lake Private: recently sold to populations) a land development company. (Less than 1 km separates Subpopulation 2: Vernon Dense subpopulation Extant 2007 [a few plants the two subpopulations.) Creek (CDC EO #25670) covered the surface of an were observed in Sept., Owner unknown: possibly oxbow 25 x 2m in size in although no plants were Vernon Airport; also 1997. Also seen sparsely present in Aug. 2007]. possibly City of Vernon scattered along the creek (Marshall Fields recreation sides north (upstream 400m) area) of the larger, oxbow subpopulation. Sources: Fieldwork by the authors in 2005 and 2007, BC Conservation Data Centre Occurrence Reports, Goward (1994), Douglas (2004), and Martin (pers. comm. 2007). * Since it was difficult to determine property ownership in the field during the time that fieldwork was being conducted, it was impossible to complete an accurate assessment of the number of individuals in any population. While most populations were visible from roadways, the winding oxbows and sloughs would have hidden some plants from view.

Designatable units

Since all populations occur within the same ecozone (Southern Mountain Ecological Area recognized by COSEWIC), a single designatable unit is recognized for this species.

DISTRIBUTION

Global range

Mexican Mosquito-fern is found in disjunct patches in North, South and Central America (Svenson 1944; Lumpkin and Plucknett 1980; Brunton 1984; Douglas 2004). In the United States, it is found in several western and mid-western states: Arizona, Arkansas, California, Colorado, Illinois, Iowa, Kansas, Minnesota, Missouri, Nebraska, Nevada, New Mexico, Oklahoma, Oregon, Texas, Utah, Washington and Wisconsin (Figure 3).

Figure 3. North American distribution of Mexican Mosquito-fern. Source: Brunton (1984), Environmental Lab (2002) and USDA (2007).

Canadian range

In Canada, Mexican Mosquito-fern is found only in south-central British Columbia (Figure 2) where it reaches the northern limits of its distribution (Brunton 1984). It was first collected in British Columbia by John Macoun, from Sicamous, in 1889, and was reported by him from Salmon Arm in 1890 (Brunton 1984). There are now ten (10) populations of this species reported in British Columbia, in three areas: Little Fort / North Thompson River, Shuswap Lake area and Vernon (Figure 3). Two of the ten populations have been confirmed as extirpated (Goward 1994; Douglas 2004; BCCDC 2005; Southern Interior Rare Plants Recovery Team 2007; Martin In press).

All Canadian populations of Mexican Mosquito-fern lie within the Southern Interior Forest Region, in the Okanagan, Shuswap, and Kamloops Forest Districts. They are found within the Montane Cordillera Ecozone (Ogilvie 1998; Environment Canada 2005).

BC populations may be relictual from a warmer post-glacial period (Brunton 1984; Martin In press). Martin (In press) speculates that it may be a species still expanding its range. It is reported from the fossil flora of the Okanagan Highlands of the province (Greenwood et al. 2005). Less than 1% of the global population is found in Canada.

Historical reports that have been redetermined:

• One collection of this species from Cobble Hill, Victoria, Vancouver Island, 2002, has been redetermined as Azolla caroliniana. [Collection #: RBCM (V) 184823. Sterile; plants all less than 0.5 cm in size]

Populations confirmed as destroyed:

• Population 4 (Darfield, south of): reported destroyed by Douglas (2004), confirmed as destroyed during fieldwork in 2005 and 2007. • Population 8 (Sicamous): reported destroyed by Douglas (2004), confirmed as destroyed during fieldwork in 2005 and 2007.

Populations added during 2007 fieldwork

• One population (Population #5 in Table 1-South of Darfield)

Extent of occurrence

The current extent of occurrence (EO) for Mexican Mosquito-fern is 5,400 km2. The extent of occurrence was calculated using Hawth’s Analysis Tools ‘create minimum convex polygon’ tool for ArcGIS 9.x (Beyer 2004). The point layer file containing the populations for all of the known populations (extant and extirpated) was used as the input file. The area of the convex hull as determined by the program was given as ~5,400 km2. This value is only slightly larger (by ~100 km2) than the EO that would be estimated from the populations presented in Martin (In press). The discovery of a new population in Vernon in 1997 (50 km south of the Shuswap Lake population; Martin In press) increased the EO by 60% from an estimated EO of 3,400 km² as of 1984 (Brunton 1984, Goward 1994) to 5,300 km². The extirpation of two populations did not affect the EO.

Area of occupancy

The Index of Area of Occupancy (IAO), determined using the IUCN methodology and 1 x 1 km grid cells, is 11 km2. Using 2 x 2 km cells, the IAO is 40 km2. However, the actual area occupied would be much less than 1 km2 (about 10 ha) if one only considers the areas of the wetlands in which Mexican Mosquito-fern is found, since most of the wetland areas (e.g., oxbows, sloughs, ponds, wet depressions in fields) are less than 1 ha in size.

The IAO was determined by converting to a raster file the layer containing all of the known populations (extant and extirpated) using the ArcGIS 9.2 Spatial Analyst ‘convert features to raster’ tool. The cell size was specified first as 1000 x 1000 m (so that each cell would represent an area of 1 km2 on the ground) and then as 2000 x 2000 m (so that each cell represents an area of 4 km2 on the ground). The cells associated with the extirpated population were not included in the calculation of the IAO values presented above.

HABITAT

Habitat requirements

Mexican Mosquito-fern is a species of relatively narrow growing requirements that is susceptible to changes in water levels and water chemistry which may restrict its occurrence in what otherwise appears to be suitable habitat (Lumpkin 1993; Douglas et al. 2004). As with other species of Azolla, it is a shade-tolerant species (Wagner 1997), found in quiet still waters of lakes, ponds, streams and other wetlands (Figure 4). In BC, it is specifically found along the shores of quiet bays and inlets of lakes, oxbows of creeks, ponds, in wet pastures proximal to creek systems, and in ditches (Brunton 1984; Douglas 2000; Martin In press, 2007). Although it is primarily a still-water species (Svenson 1944; Tryon and Tryon 1982; Brunton 1984; Douglas et al. 2000; Martin In press), Martin (In press) has observed it in faster-flowing waters. However, this may simply represent dispersal.

Figure 4. Mexican Mosquito-fern on the surface of an oxbow near Little Fort (population 2) (the red mat of Azolla has been coloured white in this photo in order to illustrate how visible it would be in the field). Photo by Brian Klinkenberg.

This species grows well in shallow water with a depth of only a few centimetres, especially where the roots can touch the substrate (Wagner 1997; Watanabe 1997). This corresponds well with summer drawdown in areas of deep water, a period when plants appear to flourish. This was noticeable during fieldwork for the species. Throughout its range, and in BC, it occurs with other aquatic species that include Lemna minor (Common Duckweed), Lemna trisulca (Ivy-leaved Duckweed), Riccia fluitans (Crystalwort), Phalaris arundinacea (Reed Canary Grass) (Keddy 1976; Brunton 1984; Klinkenberg field observations). Phalaris arundinacea is particularly prominent in the Salmon Arm sites.

Douglas (2004) and Brunton (1984) describe the species as preferring cool, slightly acidic, partially shaded, phosphorus-rich, but otherwise nutrient-poor still waters with low salinity. Wind and wave action eventually fragments and kills mosquito-ferns in general, although periodic annual flooding probably aids in dispersal (Martin In press; field observation). It is known that excessive turbidity can inhibit spore germination in

Azolla species. In BC, the Shuswap populations are described as occurring in glacial outwash plains with locally distributed calcareous deposits (Brunton 1984). Water tests conducted by Brunton (1984) found that the pH at Mexican Mosquito-fern sites ranged from 6.5 at Sicamous to 8.1 at Salmon Arm. Individual plants of Mexican Mosquito-fern vary in size from 1 cm to 2 cm, and this may reflect pH variation at each site. Other variations in water chemistry, temperature, etc., may also influence germination and growth.

Populations typically carpet areas where they occur (Figure 5), although abundance and thickness can vary dramatically from year to year.

Figure 5. Mexican Mosquito-fern completely covers the pond (area enclosed by the white line); population 1 near Little Fort. Photo by Brian Klinkenberg.

Habitat trends

In the Shuswap locale, where there is moderate urban expansion occurring, one site for this species has been lost to site alteration for development. At the Vernon locale there is the threat of development for one subpopulation, based on the recent sale of the property to a land development company.

Overall, potential habitat for this species remains stable as the large majority of it occurs in rural areas outside of any immediate development potential. However, as a result of road and highway construction, many of the oxbows and sloughs associated with the occurrence of Mexican Mosquito-fern in British Columbia have been alienated from the natural forces that influence them, such as the natural shifting of the creek/riverbed over time that sometimes allows reincorporation of old oxbows and the creation of new ones.

Habitat protection/ownership

Mexican Mosquito-fern populations occur on private lands, federal Indian reserve lands, municipal lands, Crown land (possibly), and within a provincial park. A brief summary of ownership and protection levels is provided in Table 1. The section on search effort discuses the difficulty of identifying ownership in the field.

BIOLOGY

There is a substantial amount of biological information on Azolla species as a result of their use in cultivation. This literature covers growing requirements, including influences of various chemicals (phosphorus, iron, calcium and more), temperature ranges, pH requirements and much more. While only limited biological information specific to A. mexicana is available, the general Azolla literature does provide a better understanding of this species. Key biological information on Azolla species and Azolla mexicana is summarized below.

Life cycle and reproduction

Azolla species, in general, are considered annuals that die back or decompose in the fall (Martin In press).3 Reproduction in Azolla species is most commonly by vegetative reproduction, where fragments break off and multiply (Moore 1969; Wagner 1997). Sexual reproduction by spores also occurs, and sporocarps occur in pairs in the leaf axils of older plants, usually with a pair of either microsporocarps or megasporocarps (sometimes one of each; Moore 1969). Sporocarp development in Azolla species is generally associated with mat development and summer months in temperate regions (Lumpkin and Plucknett 1980). Megasporocarps and microsporocarps dehisce at maturity and the spores sink to the bottom where they can lie dormant; germination and fertilization take place under water (Lumpkin and Plucknett 1980). Schaffner (1905) provides a clear discussion of the life cycle of heterosporous pteridophytes, and indicates that, since there are no hermaphrodites, there is no possibility of self-fertilization.

Primary dispersal of Azolla mexicana, like other species of Azolla, is by both water movement (currents, high winds) and by waterfowl (Moore 1969; Green et al. 2008). Fish may also play a role in dispersing this species. Human transport also, no doubt, occurs.

Herbivory

Azolla species are preyed upon by many insect types, particularly Lepidoptera, Diptera, Coleoptera, Aphids, and as well by snails (Gomez-Pignataro 1978; Calilung and Lit 1986; Wagner 1997; Watanabe 1997 and others). Lumpkin and Plucknett (1980) indicate that insect attacks are more prevalent in the summer, especially above temperatures of 28º C, and Azolla crops are known to be destroyed by insects. Gomez-Pignataro (1978) reports the use of Azolla mexicana as shelter by beetles, and predation on the beetles by a wasp (Polybia rejecta forma belizensis). He speculates that the wasp may control the beetles and their predation on A. mexicana.

3 An exception to this was noted by the author: Azolla mexicana plants from Vernon grown in Richmond, BC, in 2005/06 survived winter freezing and thawing and persisted into the next growing season (personal observation). Plants from Salmon Arm and Little Fort died back in October. Herbarium collections of healthy plants in November 1997 (by Martin) support this apparent cold resistance. What this represents is unknown. Reports of fall dieback may be erroneous, die-back could be variable, or plants from Vernon may not be pure Azolla mexicana (i.e., they may be hybrids with an unknown Azolla). The specimens from Vernon were verified by G.W. Douglas, and meet the size and leaf requirements for the species; however, sporocarps were immature. Additionally, in 2007, the Vernon Creek site had dried up in mid-summer (Martin pers. com. 2007). However, following autumn rains, this site refilled with water, and plants were collected from the site on Oct. 1, 2007. Plants were healthy and lush, but lacked sporocarps. This invites some speculation on life history, and adaptive responses.

Physiology

Several key features of the physiology of Azolla species, and Azolla mexicana specifically, emerge from the literature. Plants do best in 50% sunshine (Lumpkin and Plunknett 1980). Azolla generally can survive in water with a pH ranging from 3.5 to 10. Levels below 3.5 and above 10.0 are considered lethal (Lumpkin and Plucknett 1980). Johnson (1986) reports that Azolla mexicana grows best in slightly acidic waters, and grows most abundantly where the pH ranges between 6.0 and 7.0. Moore (1969) notes that in Azolla species, generally, the response to pH is significantly influenced by other factors such as light intensity, temperature and iron levels. Azolla mexicana can tolerate low levels of salinity, but is killed by high levels (Johnson 1986; Moore 1969). Growth rates of Azolla decrease with increasing salinity, and growth stops at salinity levels of 1.3%-die-off occurs at higher levels (Lumpkin and Plucknett 1980). A. mexicana has been found to be more tolerant of NaCl salinity than salinity associated with other salts. The addition of fixed nitrogen has resulted in greater salt tolerance (Johnson 1986).

Although Azolla species generally have an optimum temperature range of 18-28º C, some species can tolerate a wider temperature range of –5–35º C (Wagner 1997). The optimal temperature for Azolla reproduction is 25º C (Watanabe 1997). Nayak and Singh (2004) report abundant spore production for Azolla species under prolonged mat-forming conditions (summer months). Azolla mexicana, as with all Azolla species in general, is sensitive to desiccation (Douglas 2004; personal observation), and is killed by high temperatures (Vitousek et al. 2002 and others). However, A. mexicana is tolerant of higher temperatures than other species (Lumpkin and Plucknett 1980).

Low winter temperatures result in die-off of Azolla species at northern stations (Tryon and Tryon 1982; Brunton 1984). Although Azolla species generally are reported to be resistant to cold, freezing of the water surface can result in die-off4 (Tsujimura, Ideda and Tukamoto 1957 cited in Moore 1969). Lumpkin (1993), in Flora North America, indicates that A. mexicana is less cold tolerant and has a narrower environmental range than A. caroliniana. Cold tolerance is generally greatest with a higher pH in the range of 8 to 10 (Lumpkin and Plucknett 1980).

Based on cultivation information, and on other sources, phosphorus and iron may be limiting factors for growth and population establishment (Brunton 1984). Lack of iron turns plants yellow, while lack of phosphorus curbs growth and turns plants red (Lumpkin and Plucknett 1980). Azolla fronds also turn red in strong sunlight, while fronds that are growing in shade retain their green colour. However, red colouration may also be a result of stress factors such as insect damage, high pH, low temperature, or calcium deficiencies that can limit the ability of plants to use strong sunlight (Lumpkin and Plucknett 1980; Watanabe 1982; Wagner 1997).

4 See comments under footnote #3.

Dispersal

The possibility of rescue effect for this species in Canada exists. Azolla mexicana is passively dispersed by wind, water currents and waterfowl, and dispersal by humans no doubt occurs if plants or spores are transported on clothing or attached to boats (Moore 1960; Lumpkin and Plucknett 1980). Long-distance dispersal is likely through transport by birds, both externally (e.g., carried in mud attached to the feet) (Cruden 1966; Figuerola 2002; Figuerola and Green 2003) and internally (endozoochory) (Figuerola 2002; Figuerola and Green 2002; Green et al. 2008). There is “little doubt that birds acts as dispersal agents” for many aquatic species (Cruden 1966, p. 518); even Darwin in 1859 noted that birds disperse plant propagules (Cruden 1966). The distances involved range from 10s of km on a daily basis to over 200 km during migration (Cruden 1966; Figuerola 2002). Although there have been no studies specifically studying the transportation of Mexican Mosquito-fern by birds, Green et al. (2008, p. 386) did observe in Australia that “swan and especially coot samples contained large amounts of Azolla filiculoides” megasporocarps that were potentially viable.

It is likely that, in the event of extirpation of Canadian populations, rescue could be effected naturally, especially during waterfowl migration periods.

Interspecific interactions

Azolla mexicana, like other species of Azolla, lives in symbiosis with a cyanobacterium—Anabaena azollae (Lumpkin and Plucknett (1980). Azolla provides nutrients and a protective cavity for the alga, while the alga provides fixed atmospheric nitrogen to the Azolla. Other interspecific interactions are unknown.

Adaptability

Azolla mexicana is one of several species of Azolla that are grown horticulturally and agriculturally as a green fertilizer and for use as a nutritional supplement in livestock feed. Cultivated stock may be readily used for transplanting, and is used in various countries in the Mediterranean, including Turkey, and others. However, the success of transplants and their adaptability under BC growing conditions is unknown. The species is very limited in the ponds and streams in which it appears.

POPULATION SIZES AND TRENDS

Search effort

Directed fieldwork for Mexican Mosquito-fern—over an area that encompasses the known range for the species in British Columbia—was conducted in July and August in two separate years—2005 and 2007. This is the time period when the species can be most easily identified in the field. In 2007, field searches were conducted from the 15th to the 21st of August in an area from Osoyoos north to Clearwater, and from just west of Revelstoke to Cache Creek (1800 km driven). In late July, 2005, the same area was also searched specifically for the Mexican Mosquito-fern for recovery strategy work (over 1800 km driven). Although typically populations are highly visible in August, it is possible that some (sub) populations may only appear in September and October (Brunton 1984; Martin pers. comm. 2007; personal observations 2007).

In both 2005 and 2007, all documented populations of Mexican Mosquito-fern (extant, assumed extirpated and historical) were visited. Close attention was paid, in particular, to bodies of water near previously identified populations since it was felt that those areas would be the most likely to contain undocumented populations. However, surveys were also conducted between sites for the species.

In addition, in 2002, 2003, and 2004, fieldwork conducted for other species (e.g., Symphyotrichum frondosum) by the author was carried out in the same region during the months of July and August, with a total of over 3000 km driven. Fieldwork for these species covered most of the same territory as that associated with Mexican Mosquito- fern, and included searching lakes, ponds and rivers for shoreline species. Other botanists, such as Malcolm Martin, Trevor Goward, George Douglas, Jenifer Penny, and Jamie Fenneman have also travelled extensively throughout the region over many years (Penny pers. comm. 2007). Douglas and Fenneman, in particular, searched for Mexican Mosquito-fern in the same areas in 2004. If Mexican Mosquito-fern had been present in any of the areas searched, it likely would have been documented.

The majority of the publicly accessible roads in the region have been traversed at least once and the major roads traversed many times over those years. All suitable ponds, rivers and wetland areas observable from a paved road, as well as accessible water bodies identified from topographic maps, were scanned, both on foot and using binoculars. If there was any indication that Mexican Mosquito-fern might be present (i.e., patches of red or green plants on the surface of the water body (Figure 4), a closer inspection was made where access was possible.

It is important to note that, outside of the main and secondary roads, there are relatively few accessible roads in this area of the province.

At the Vernon sites, the landowner of one subpopulation was approached, but permission to enter was denied. This was because the site was purchased by a development consortium (Martin pers. comm. 2007). However, it is also important to note that most Mexican Mosquito-fern populations occur in rural areas where it is often difficult to identify the property owner while in the field. Ownership for some sites is obscure and would require detailed investigation. This is particularly true in areas of open rangeland (no fencing) that were searched in the North Thompson River area. Lack of access to private property was a limitation as the full extent of populations at some sites is not visible from the road, and cannot be determined without a site visit, which in turn determines how many property owners are involved.

In most cases, for known populations, it was impossible to identify a residence associated with the property on which the population was observed (fences may or may not be present, and the closest residence may be several kilometres away). The owner or resident was not present at the one population that occurred on private lands and for which a residence could be easily identified (the Little Fort Round Top Road population). Two of the populations occur on Indian Reserves, and permission was not obtained for a site visit. It was thus not possible to document the full extent of any of the populations—only a general description of the population as viewed from the highway could be taken. Fortunately, most populations were visible from the highway. However, given the nature of the habitat of the species, it is possible that populations occur in oxbows and sloughs not visible from any highway.

Abundance, fluctuations and trends

For this status report, all reported sites for Mexican Mosquito-fern from previous status reports were assessed using a minimum separation of 1 km between populations. This distinction of populations is generally followed by the Vascular Plants Subcommittee (COSEWIC) for defining separate populations. This has resulted in a grouping of some “populations” and recognition of subpopulations (Table 1). Following this, there are now 10 populations of this species reported in British Columbia that can be identified within three areas: Little Fort / North Thompson River, Shuswap Lake area and Vernon (Figure 2). Two of the ten populations have been confirmed as extirpated (Goward 1994; Douglas 2004; BCCDC 2005; Southern Interior Rare Plants Recovery Team 2007; Martin In press).

Better documentation of known sites, and fieldwork since the first COSEWIC status report in 1984 (Brunton 1984), the update status report by Martin (In press), the national recovery strategy by Klinkenberg (2005) and for this status report, makes it appear that the number of Mexican Mosquito-fern populations has greatly expanded. However, while two populations in the Little Fort area (80 km to the north of the Shuswap Lake population) were not officially reported until 1994 (Goward 1994), they were known (and had been documented by collections) in 1982, which meant that, by 1984, there were actually 6 populations.

Between 1984 and 1997, an additional two populations were reported in the Little Fort area, bringing the total number of populations to 8. In 1997, a new population was reported from Vernon by Martin (In press), increasing the total number of known populations to 9. Note that Martin (In press) identifies two new populations from Vernon, and therefore reports ten populations in total. Assessment using a GIS showed, however, that the records from Vernon should be considered as a single population, and therefore Martin’s population totals should be restated as 9. Given that Martin has lived in the Vernon area for several decades, the population he found in Vernon may represent a new population. However, due to dormancy of spores it is uncertain if this actually represents an expansion of the EO or renewed growth from dormant spores of a previously existing population.

The discovery of a new population south of Darfield during 2007 fieldwork brings the total number of known population for this species to 10. Since 1997, however, two populations were extirpated, leaving only 8 extant populations for this species as of 2007.

Because this species seems tied to the warmer temperature ranges, monitoring and on going inventory work will be needed to assess whether expansion of the species range is occurring.

Population fluctuations

Of note with this species is the appearance and disappearance of populations from year to year. Fieldwork in 2004, 2005 and 2007 has shown that while in some years plants appear absent from a site, they can reappear in following years. Goward (1994) particularly documents this fluctuation in appearance of Mexican Mosquito-fern in the Little Fort area between 1982 and 1994. Losses may be attributable to water chemistry and temperature fluctuations, and precipitation and/or draw-down in creeks and ponds. Re-appearance may be attributable to a persistent spore bank that reactivates when microclimate and water chemistry conditions are favourable. From this, it is important to note that absence of plants in any given year does not mean the extirpation of the population.

This responsiveness to annual and seasonal fluctuations in growing conditions influences searches for new populations and confirmation of known populations. Although many sites have been searched for the species with no success, this does not mean that populations are not present. Repeated searches over a span of several years are needed to assess populations of this species. It is notable that populations reported historically continue to be reported in the same sites, so populations appear to be persistent, and do not appear to have expanded in each locale. Also of note is the wide fluctuation in areal extent of individual populations. Based on fieldwork, this can vary from a few plants in one year to a thick continuous cover of plants in other years.

It should be apparent that determining the absolute population size—counting individual plants—is not practical for this species, given its extensive mat-forming nature. As illustrated in Figure 5, the plant, if present, most often covers the surface of the water body with thousands if not tens of thousands of plants (Table 1).

Furthermore, in spite of an extensive surface coverage in some years, plants can ‘disappear’ in intervening years. For example, in 2004 George Douglas did not observe any plants growing in the (western) oxbow in Figure 4, yet in 2005, when the photo was taken in the late summer, tens of thousands of plants were present. No plants were observed in the adjacent (eastern) oxbow in 2005, although Douglas observed several hundred plants there in 2004. He noted that in previous years the population at this site was much larger than our estimates for 2007.

This illustrates the problem inherent in confirming populations of mat-forming or clonal plants in years when they are dormant. If the habitat remains undisturbed, many years of consistent observation are required before a population can be declared extirpated. A population of a species such as Mexican Mosquito-fern should only be declared extirpated if the habitat has been significantly altered, as is the case for the Sicamous population and for the extirpated Darfield population (in both cases the land was filled in). Determining the total number of individuals and year-to-year changes in total population size and density would only be meaningful if those numbers were derived from many years of careful, consistent observation. Site-specific yearly monitoring of actual areas occupied would be an easier and more practical manner of determining population fluctuations than estimating numbers of individuals for this tiny aquatic fern.

Rescue effect

Since A. mexicana is not tracked in Washington State, information on its overall abundance is not available. However, based on information obtained from the collection labels for A. mexicana specimens held in the UW Herbarium at the Burke Museum of Natural History and Culture (2007), the species does not appear to be abundant in that state as only eight collections are recorded from Washington State. Two of those collections are from the 1800s, and three of the more recent collections list the species as not common. The three collections from the two northerly-most counties do, however, indicate that the species is abundant at those sites. Assuming that waterfowl could transport plants or spores, it is possible that plants from Washington State populations could rescue Canadian populations. Such an event, however, would likely occur infrequently with long intervals between events. This is surmised on the basis that in the Okanagan only 10 locations are known and many other seemingly suitable water bodies are unoccupied by the species. If movement by waterfowl is the primary means of natural dispersal, then presumably more suitable habitats should be occupied.

LIMITING FACTORS AND THREATS

Limiting factors

Several naturally limiting factors affect Mexican Mosquito-fern in BC.

1. Mexican Mosquito-fern is reportedly sensitive to cold temperatures, which may affect populations during periods of temperature extremes and may account for population fluctuations from year to year. Plants growing in sites with higher pH are reportedly less susceptible to cold temperatures. However, see the discussion in Footnote #3, page 16.

2. Mexican Mosquito-fern is also sensitive to changes in pH, salinity and water temperatures, as well as to phosphorus and iron levels in the water. Slight changes to these elements resulting from natural changes to site conditions (e.g., periodic flooding) could also account for population fluctuations and place distributional limitations.

3. Nitrogen fertilizers adversely affect Azolla growth, but reports of the effects are inconsistent (Lumpkin and Plucknett 1980).

Threats

Several threats to Mexican Mosquito-fern and its habitat have been identified by Brunton (1984), Martin (In press) and during work for this status report:

1. Road construction: Several populations of this species occur adjacent to highways and roads, and other public use areas, and this proximity to these areas poses a threat. One population was lost as a result of infilling related to road construction/road repairs (south of Darfield) (Douglas 2004).

2. Housing/urban development: This is a threat in the Sicamous and Vernon areas. One of the two subpopulations in Vernon has recently been purchased by a development company, and one subpopulation in the Sicamous area has been infilled in an area of housing development.

3. Eutrophication: Eutrophication is apparent at population 7, subpopulation 2 (Salmon Arm foreshore subpopulation). This site is located at the base of the public pier, along the foreshore of Lake Shuswap, immediately to the east of the park area. Algae bloom was apparent at this site in 2005 and 2006, although Azolla plants were present; the actual effect of a bloom on Azolla is, however, unknown.

4. Invasive species: Encroachment of Reed Canary Grass (Phalaris arundinacea) is also evident at population 7, subpopulation 2 (Salmon Arm foreshore), and was reported by Douglas in 2004 and confirmed in 2005 and 2007.

5. Accidental spills and runoff:

a. Roadways/highways: Most populations of Mexican Mosquito-fern are found along highways and in public access areas where impact from adjacent roadwork, chemical spills, or development could potentially affect the wetland habitat and could alter water chemistry, conceivably destroying entire populations. Additionally, sensitivity to high levels of salinity use on adjacent highways would make salting of roadways and associated runoff a threat. Salt and other toxic runoff from roadways could impact plants directly.

b. Railway spills: While the chances of a railway spill adjacent to the two populations located along the railway at Salmon arm are low, an occurrence would nevertheless have significant impact on the adjacent wetlands, and Azolla mexicana.

SPECIAL SIGNIFICANCE OF THE SPECIES

Azolla mexicana is a species at risk in BC and Canada that reaches its northern limits of distribution in the Little Fort area of British Columbia. BC populations are disjunct by 300 km from the nearest US population in Washington State. As populations, peripheral to the main species range, our populations could be important to the species long-term survival in the face of climate warming.

In other parts of the world, A. mexicana is grown as a crop and is of economic importance. It is used as a green manure and as a weed control measure in rice and other crops. It is also used as food for livestock. In some regions it is considered an invasive species. It is, for example, listed as a noxious weed in some counties in Montana.

EXISTING PROTECTION OR OTHER STATUS DESIGNATIONS

In Canada, Mexican Mosquito-fern is protected on federal lands by the Species at Risk Act (SARA). Specific conservation status in Canada and the US follows:

Global Status: G5 (Global: Secure) Global Status Last Reviewed: 27Jan 1987 Global Status Last Changed: 27Jan 1987 Rounded Global Status: G5 - Secure Nation: United States National Status: NNR (National: Not Ranked) Nation: Canada National Status: N2 (National: Imperiled) COSEWIC: T (Threatened 2000)

United States

Arizona (SNR), Arkansas (SNR), California (S3.2?) (Subnational: Vulnerable to Imperiled?), Colorado (S4) (Subnational: Apparently Secure), Illinois (S4), Iowa (S3) (Subnational: Vulnerable), Kansas (SNR), Minnesota (SNR), Missouri (SNR), Nebraska (SNR), Nevada (SNR), New Mexico (SNR), Oklahoma (SNR), Oregon (SNR), Texas (SNR), Utah (S2?) (Subnational: Imperiled?), Washington (SNR), Wisconsin (SNR)

Canada

British Columbia (S2) SARA: Schedule 1, threatened

TECHNICAL SUMMARY

Azolla mexicana Mexican Mosquito-fern Azolle du Mexique Range of Occurrence in Canada: British Columbia

Demographic Information Generation time (average age of parents in the population) <1 yrs Observed percent reduction in total number of mature individuals over the Unknown last 10 years. Projected percent reduction in total number of mature individuals over the Unknown next 10 years. Observed percent reduction in total number of mature individuals over any Unknown 10 years period, over a time period including both the past and the future. Are the causes of the decline clearly reversible? Are the causes of the decline understood? Have the causes of the decline ceased? Observed trend in number of populations Unknown Likely stable but uncertain since losses have occurred and new populations found due to increased search effort and population fluctuations with some absent some years. Are there extreme fluctuations in number of mature individuals? No Numbers of plants can fluctuate greatly at sites but due to the presence of dormant spores “extreme fluctuation” as defined by IUCN is not met. Are there extreme fluctuations in number of populations? No

Number of mature individuals in each population Population N Mature Individuals Millions of tiny aquatic ferns reproducing vegetatively at 8 extant sites with fluctuations noted at some sites.

Grand Total Millions likely in any one year

Extent and Area Information Estimated extent of occurrence (km²) 5400 km² Observed trend in extent of occurrence Unknown Increased numbers of localities are likely due mainly to increased search effort. Are there extreme fluctuations in extent of occurrence? No Estimated area of occupancy (km²) 1x1 grid = 11km² 11 based on 1x1 km grid; 40 based on a 2x2 km grid 2x2 grid = 40km² Observed trend in area of occupancy Unknown Perhaps stable but uncertain since new sites found and some lost. Are there extreme fluctuations in area of occupancy? No There can be apparent visual fluctuation from year to year in the actual area of habitat occupied. Is the extent of occurrence or area of occupancy severely fragmented? No Sites are 50-80 km apart although the potential exists for occasional movement of propagules by waterfowl. “Severely fragmented” as defined by IUCN cannot be readily determined. Number of current locations 8

Trend in number of locations Increase The current number is seemingly an increase but this is likely due to the more extensive fieldwork since the original status report. Are there extreme fluctuations in number of locations? No Observed trend in area of habitat Unknown The species has undergone some population losses and fluctuations in size of populations makes it difficult to determine a trend.

Quantitative Analysis Ex.: % probability of extinction in 50 years

Threats (actual or imminent, to populations or habitats) Road construction and associated infilling has resulted in the loss of one population (Darfield). Site development (infilling) has resulted in the loss of another population (Sicamous). One subpopulation in Vernon occurs on a property that was recent purchased by a land development company, so its future is very insecure. Several populations / subpopulations have not been observed for several years (i.e., Eagle River, Vernon Creek, White Creek) although no apparent causal factor can be identified. This could be a result of lack of observation at the right time, natural population variation, or actual extirpation of the population. The majority of the populations, with the exception of the Vernon and White Creek populations and some of the Salmon Arm subpopulations, are located adjacent to major highways or a railway, so accidental spills and maintenance activities and associated chemicals (e.g., road salt in the winter) are ever-present threats.

Rescue Effect (immigration from an outside source) Status of outside population(s)? USA: Not assessed nationally Is immigration known or possible? Unknown Possible but no evidence available Would immigrants be adapted to survive in Canada? Likely Is there sufficient habitat for immigrants in Canada? Yes Is rescue from outside populations likely? Unlikely Movement of propagules is possible but unlikely over 300 km distance during migration north from Washington. If this were a likelihood, more populations should have become established in BC.

Current Status COSEWIC: Threatened 2008

Status and Reasons for Designation Status: Alpha-numeric code: Threatened B1ab(iii,iv,v)+2ab(iii,iv,v) Reasons for designation: This tiny floating aquatic fern of south-central British Columbia is restricted to 8 small water bodies where its populations undergo periodic fluctuations in numbers of individuals. Two populations and their habitat have been lost in recent years due to construction activities with most of the extant populations occurring adjacent to major highways or a railway where they are at potential risk from maintenance activities, including the use of chemicals such as road salt.

Applicability of Criteria Criterion A (Decline in Total Number of Mature Individuals): Not applicable. No overall decline percentages are available although two populations have become extirpated. Criterion B (Small Distribution Range and Decline or Fluctuation): Meets Threatened B1ab(iii,iv,v)+2ab(iii,iv,v); the extent of occurrence and area of occupancy are below critical values for Threatened; 8 extant populations are known with recent losses of two populations resulting in a loss of habitat, number of locations and mature individuals. Criterion C (Small and Declining Number of Mature Individuals): Not applicable. Population size exceeds maximum criterion levels. Criterion D (Very Small Population or Restricted Distribution): Not applicable. Population size is too large for D1. Criterion D2, even when based on the smaller IAO being <20 km², may not apply due to the presence of 8 extant populations and the potential for the discovery of a few additional small populations in areas not directly accessible by roads. Criterion E (Quantitative Analysis): None available

ACKNOWLEDGEMENTS AND AUTHORITIES CONSULTED

Several knowledgeable individuals were consulted during the preparation of this status report. The author would like to extend thanks to Adolf Ceska, Sharon Hartwell, Frank Lomer, Malcolm Martin, and Jenifer Penny for providing key information about Azolla mexicana and other Azolla species in BC. A special thank you to Malcolm Martin for providing ownership information on Vernon populations, specimens, and field accompaniment. Particular thanks go to Rose Klinkenberg for assistance with background research and fieldwork. The assistance of Linda Jennings, UBC Herbarium, in obtaining specimens loans is very much appreciated.

Authorities consulted

Alain Filion. COSEWIC Secretariat, Map Preparation and Calculations. E-mailed August 8, 2007. Kevin Fort (cc Bob Elner), Canadian Wildlife Service, Pacific and Yukon Region. E- mailed August 8, 2007. Dave Fraser, BC Endangered Species Specialist, Biodiversity Branch, BC Ministry of Environment. E-mailed August 9, 2007. Gloria Goulet, COSEWIC Secretariat, Aboriginal Traditional Knowledge. E-mailed August 9, 2007. Ted Lea, Recovery Team, BC Ministry of Environment. E-mailed August 9, 2007. Jenifer Penny, Provincial Botanist, BC Conservation Data Centre. E-mailed August 9, 2007.

INFORMATION SOURCES

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BIOGRAPHICAL SUMMARY OF REPORT WRITER

Brian Klinkenberg is an Associate Professor of Geography at the University of British Columbia, and holds an M.Sc. in biogeography and a Ph.D. in landscape modelling and GIS. His research focuses on spatial analysis, landscape analysis, and the biogeography of rare plants, and has included exploration of the coincidence of rare plants and landform, the biogeography of the vascular flora of the Erie Islands, ecosystems services, effects of landscape and habitat fragmentation on forests, methods of evaluating restoration success, and nature reserve design. He is project coordinator and editor for E-Flora BC and E-Fauna BC, the biogeographic atlases of British Columbia. Brian is presently Chair of the Research Committee of the South Coast Conservation Program, and sits on the recovery teams for Streambank Lupine and Phantom Orchid. He has authored several national recovery plans, including Bidens amplissima, Cephalanthera austiniae, Azolla mexicana, Symphyotrichum frondosum, Epilobium torreyi, and Lupinus rivularis. He has also authored or co- authored several COSEWIC status reports, including Astragalus spaldingii, Bidens amplissima, Celtis tenuifolia, Cephalanthera austiniae (2), Collinsia verna, Desmodium illinoense, Opuntia humifusa, Lupinus rivularis, Ranunculus californicus, and Symphyotrichum frondosum. Additional technical reports include inventory and monitoring standards for rare plant species, and predictive mapping of rare species.

COLLECTIONS EXAMINED

The following collections were examined by the author:

UBC

1) Azolla mexicana. V219686, J.A. Calder, D.B.O. Savile and J.M. Ferguson, September 14, 1954, ½ mile west of Solsqua along road between Sicamous and Revelstoke, duplicate DAO. Vegetative. Unable to confirm identification.

2) Azolla mexicana. V213376, W.B. Schofield (his collection #109591), 1997, floating mats on pond ca. 6 mi E of Sicamous, pond in woodland. Fertile. ID confirmed by R. Klinkenberg.

3) Azolla mexicana. V140625, A & B Schwartz, September 22, 1972. 5 miles east of Sicamous opposite RR crossing. Fertile. ID confirmed by R. Klinkenberg.

RBCM (V)

4) Azolla mexicana. 184823, J. Deniseger. February 14, 2002. Det. Richard Hebda. Vancouver Island, Cobble Hill, just outside of Manley Creek Community Park, north of Arbutus, Victoria. Golf Course. Plants less than .5 cm, vegetative. This specimen was re-determined as Azolla caroliniana by R. Klinkenberg 2007.

5) Azolla mexicana. 174999, M.E. Martin, November 4, 1997, Vernon Creek, .5 km along creek from mouth, oxbow at bend of creek. Vegetative. Verified by G. W. Douglas.

6) Azolla mexicana. 174998, M.E. Martin, November 4, 1997. Det. M.E. Martin. Vernon, 6141 Okanagan Avenue 82L-3, two low patches in field surrounded by rough pasture. Vegetative. Verified by G. W. Douglas.

7) Azolla mexicana. 196897, Bob Scheer, September 3, 1998. Thompson- Okanagan, Little Fort, 1.13 km south of Little Fort, junction of highways 5 and 24, in abandoned stream channel at roadside in pond channel. Fertile. ID confirmed by R. Klinkenberg.

Other (unprocessed specimens to be deposited at UBC)

2005

8) Azolla mexicana. Malcolm Martin. August 24, 2005. Vernon Creek, north side, in oxbow across from Marshall Fields parking area, in stagnant shallow water. A few scattered but immature sporocarps.

9) Azolla mexicana. Brian Klinkenberg. July 2005. Salmon Arm, in shallow water of the bay immediately adjacent to public pier, east side of park where it meets the pier. Many sporocarps. ID confirmed by R. Klinkenberg 2005/2007.

10) Azolla mexicana. Brian Klinkenberg. July 2005. Little Fort, just north of, in shallow water in oxbow. Fertile. ID confirmed by R. Klinkenberg 2005/2007.

2007

11) Azolla mexicana. Brian Klinkenberg. August 2007. Salmon Arm, along railway tracks east of pier. Fertile. ID confirmed by R. Klinkenberg 2007.

12) Azolla mexicana. Brian Klinkenberg. August 2007. Darfield. Twenty meters south of Darfield sign, in shallow water of oxbow on east side of road. Fertile. ID confirmed by R. Klinkenberg 2007.

13) Azolla mexicana. Brian Klinkenberg. August 2007. Little Fort, south of, in shallow water in old oxbow, east side of road. Population continues in patches on west side of road in oxbows and ponded areas. Fertile. ID confirmed by R. Klinkenberg 2007.

14) Azolla mexicana. Malcolm Martin. October 2007. Vernon Creek, in small drainage ditch into Vernon Creek. Disturbed area. Immature plants with no sporocarps. (No plants were present when the area was checked in August 2007).

Specimen examined by Frank Lomer

15) Azolla mexicana. George Douglas5. Date Unknown (probably 2004). Site unknown. Fertile. ID confirmed by Frank Lomer 2007.

Excluded

Azolla mexicana. V219683, J.A. Calder, September 14, 1954, ½ mile west of Solsqua along road between Sicamous and Revelstoke, duplicate DAO. Re-determined to A. caroliniana.

5 Frank Lomer examined two specimens collected by George Douglas that contained George’s field collection numbers, but no other notes. The identification was confirmed by the megaspores.