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DISCOVERY OF CHAMAENERION LATIFOLIUM (L.) HOLUB (ONAGRACEAE) IN THE GREAT LAKES REGION

Samuel R. Brinker

Science and Research Branch Ontario Ministry of Natural Resources and Forestry Peterborough, Ontario K9J 3C7 sam.brinker@ontario.ca

ABSTRACT

The f irst report of Chamaenerion latifolium (L.) Holub in the Great Lakes region is described from Kama Hills, near Nipigon, Ontario. This showy, long-lived herbaceous perennial is a circum- polar arctic and alpine plant of well-irrigated, open calcareous floodplains, river bars, seepage slopes, and scree slopes in alpine zones. Its presence in the region is remarkable, being disjunct from the next nearest populations over 700 km to the north. It adds to the list of disjunct arctic- alpine plants restricted to isolated pockets of disturbance-maintained, open rocky sites that have remained relatively unchanged since the retreat of the Wisconsinan glacier roughly 11,000 years ago.

KEYWORDS: Chamaenerion latifolium, disjunct arctic-alpine, western Lake Superior region, Thunder Bay District.

INTRODUCTION

Chamaenerion latifolium (L.) Holub (Onagraceae) is reported here as new for the Great Lakes basin and the Thunder Bay District in Ontario. Addition- ally, this record appears to be the most southerly occurrence of this species east of the Rocky Mountains, as illustrated in Figure 1. An early literature report exists from the Black Hills region of South Dakota in McIntosh (1931), though no substantiating specimens have been found, nor do recent floras for the re- gion include this taxon (e.g., Dorn et al 1977, VanBruggen 1985, Marriott 1986) other than referencing the historical report and lack of a supporting specimen. The small population of roughly 100 mostly non-flowering plants is disjunct from the nearest population to the north by roughly 700 km. Its oc- currence in the Great Lakes basin is remarkable and mirrors the distribution of several other disjunct arctic-alpine vascular plants in the region, e.g., Pyrola grandiflora Radius, Saxifraga oppositifolia L., Carex glacialis Mackenzie, Dryas integrifolia Vahl, and Cerastium alpinum L., among others (for more complete discussions and lists see Butters and Abbe 1953; Soper and Maycock 1963; Given and Soper 1981; Bakowsky 1998).

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FIGURE 1. North American range map of Chamaenerion latifolium (adopted from Small 1968; Por- sild and Cody 1980; and Aiken et al. 2007). The Kama Hills site in the Lake Superior basin is repre- sented by a white star.

DISTRIBUTION AND ECOLOGY

Chamaenerion latifolium (Figure 2), which is known under the vernacular names Arctic Fireweed, Alpine Fireweed, Dwarf Fireweed, Broad-leaved Fire- weed, River Beauty, and Épilobe à feuilles larges, is a long-lived perennial herb of arctic and alpine habitat found throughout the Northern Hemisphere, includ- ing North America, Greenland, Iceland and northern Russia, but is absent from most of northern Europe. It is highly disjunct in southern Asia, occurring in the Himalayas from Afghanistan to western China (Small 1968). In North America, it is found in Alaska, Yukon, the Northwest Territories, Nunavut, Labrador, and Newfoundland, portions of northern Manitoba, Ontario, and Quebec, as well as sporadically throughout the Canadian Arctic Island Archipelago (Figure 1) (Por- sild and Cody 1980; Aiken et al. 2007). In the West, its range extends south along the Rocky Mountains culminating a trend in the western Cordillera to increas-

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FIGURE 2. Chamaenerion latifolium, growing on wet, vertical rock at Kama Hills, Thunder Bay District, Ontario. Photo by Samuel Brinker.

ingly isolated and elevated sites, the southernmost of which occur in Colorado at 12,500 ft (Small 1968).

A pioneer species, Chamaenerion latifolium is an excellent colonizer of suc- cessional habitat and can often be found in abundance, forming monospecif ic stands on calcareous substrates that are usually well-irrigated, such as gravel bars, alluvial floodplains, newly exposed glacial tills, seepage slopes, edges of snow patches, and even disturbed roadsides. Despite being a long-lived perennial and a highly eff icient colonizer, C. latifolium is a poor competitor. According to Doak (1991), it shows its greatest growth and reproduction when colonizing sparsely vegetated sites, quickly decreasing in abundance and vigor as other species invade.

Plants arise from pseudorhizomes, a slight thickening of the underground stem which bear annual shoots that originate as branches at or below ground level of the previous years’ growth (Doak 1991). Each pseudorhizome can per- sist for several years, but eventually dies off creating autonomous plants. Chamaenerion latifolium is an excellent disperser, distributed by comose, wind- blown seeds.

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FIGURE 3. Medicolous cliff habitat at Kama Hills, Ontario. The plants were restricted to the central portion of the upper vertical tier of the rock face with direct sunlight exposure. Photo by Samuel Brinker.

DISCUSSION

The Lake Superior region has long been known to harbour assemblages of arctic and alpine plant species adapted to its cold, exposed rocky shores dotted with sparse, often stunted conifer trees and low ericaceous shrubs found more abundantly in the adjacent uplands. The region’s unique landscape and its geo- logic and edaphic diversity are thought to have maintained small areas of ex- posed, open habitat following the retreat of the Wisconsinan ice sheets that for- merly covered the region until roughly 11,000 years ago (Saarnisto 1974). As the regional climate ameliorated and the ice sheets receded, the cold-adapted vege- tation that colonized the recently exposed land was largely replaced by boreal forest. The continued presence of this unique assemblage of plants is therefore assumed to be relictual, persisting in small isolated pockets of open habitat orig- inating from late-glacial and post-glacial colonization via step-wise or long-dis- tance dispersal. Well-known sites harbouring arctic-alpine floral assemblages tend to be coastal (e.g., Old Woman Bay) and are often on remote islands (e.g., Slate Islands, Isle Royale), in isolated inland canyons (e.g., Ouimet Canyon, Ot- tertooth Canyon), or on exposed diabase cliff and talus slopes which often har- bour a more characteristically Western Cordilleran floral element (e.g., North Fowl Lake).

The occurrence of C. latifolium on a water-fed cliff face is noteworthy in that

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TABLE 1. Disjunct arctic-alpine plants “partially tracked” in Ontario’s Great Lakes basin. These plants are locally common in extreme northern Ontario near Hudson Bay and James Bay but occur very rarely around the shores of the Great Lakes, separated by hundreds of kilometers from their nor- mal range. These populations have different natural and anthropogenic threats from those of the northern populations and are therefore tracked only in this region of the province.

Scientif ic Name Common Name Anemone parviflora Michaux Small-flowered Anemone Astragalus alpinus L. Alpine Milk-vetch Carex glacialis Mackenzie Glacier Sedge Carex saxatilis L. Russet Sedge Carex scirpoidea Michaux ssp. scirpoidea Single-spike Sedge Castilleja septentrionalis Lindley Northeastern Paintbrush Cerastium alpinum L. Alpine Chickweed Chamaenerion latifolium (L.) Holub River Beauty Draba aurea Vahl ex Hornemann Golden Draba Dryas integrifolia Vahl Entire-leaved Mountain Avens Poa alpina L. Alpine Bluegrass Poa pratensis L. ssp. alpigena (Lindman) Hiitonen Alpigene Bluegrass Pyrola grandiflora Radius Arctic Pyrola Saxifraga tricuspidata Rottbøll Three-toothed Saxifrage Solidago multiradiata Aiton Multi-rayed Goldenrod Tanacetum bipinnatum (L.) Schultz-Bipontinus Dwarf Tansy Taraxacum ceratophorum (Ledebour) de Candolle Horned Dandelion Tofieldia pusilla (Michaux) Persoon Small False Asphodel

this habitat is distinct from the more typical arctic-alpine habitat types men- tioned above that have received more extensive botanical attention. The unusual wet vertical rock surface is much scarcer than the more typical dry cliffs in the region and closely mimics ice-scoured river banks and seepage slopes typical of

C. latifolium habitat in arctic and alpine regions and limits competition from woody invasion. The vegetation at the Kama Hills site illustrated in Figure 3 is sparse, domi- nated by bryophytes and low herbaceous plants and with few woody species as a result of the lack of soil development. Other moisture-loving calciphiles present included Primula mistassinica Michx. and Dasiphora fruticosa (L.) Rydb. The constant water supply here and the northwest aspect create a distinctly humid and colder than normal microclimate.

Although Chamaenerion latifolium is relatively common in northern Ontario, this isolated population disjunct from its main range may be especially sensitive to climate change. Such peripheral populations of arctic-alpine plants have been highlighted as particularly vulnerable to warming climates (Lesica and McCune 2004; Klanderud 2008; Gibson et al. 2009), and local extinctions of peripheral populations from their core may mean losses of genetic distinctiveness (Hampe and Petit 2005; Hamilton and Eckert 2007). This population occurs in the Kama Hills Provincial Conservation Reserve and thereby is protected from direct an- thropogenic threats such as logging, mining, or development. Chamaenerion lat- ifolium joins a list of disjunct arctic-alpine vascular plants in the Lake Superior

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region that, despite being more common further north in Ontario, are being mon- itored (partially tracked) in the Great Lakes basin because of the unique set of threats that they face, namely climate change, shoreline development, and small population size. It is considered globally Secure (G5) (NatureServe 2015, as Chamerion latifolium), nationally Secure in Canada (CESCC 2011), and Appar- ently Secure (S4) in Ontario (Oldham and Brinker 2009). Table 1 lists the current disjunct arctic-alpine plants that are rare in the Great Lakes basin, but which are generally common and widespread in Ontario’s Hudson Bay lowland.

DIAGNOSTIC CHARACTERS

Chamaenerion latifolium can be distinguished from the other showy species of Chamaenerion in the region, C. angustifolium (L.) Holub, by its low, decum- bent to ascending, often branched stem (up to 40 cm) and compact, few-flowered raceme. Chamaenerion angustifolium is taller (up to 1 m), with an erect, usually single stem, and an elongated, many-flowered raceme. Also, the base of the style is glabrous in C. latifolium, whereas it is pubescent in C. angustifolium. Chamaenerion latifolium is restricted to wet, calcareous cliff habitat in the Lake Superior region, whereas C. angustifolium is widespread in meadows, clearings, open forests, and recently burned or otherwise disturbed areas.

SPECIMEN CITATION

ONTARIO, THUNDER BAY DISTRICT: Kama Hills Conservation Reserve, 19 km east of Nipigon, on medicolous, sheltered rock face with Phegopteris con- nectilis, Primula mistassinica, Calamagrostis canadensis, Rubus pubescens, and Dasiphora fruticosa. Roughly 100 mostly non-flowering stems, August 21, 2015, Brinker 4647 (DAO, MICH).

ACKNOWLEDGMENTS

I would like to thank the Ontario Ministry of Natural Resources and Forestry’s Science and Re- search Branch and the Natural Heritage Information Centre which supported f ieldwork, as well as funds secured through the Canada Ontario Agreement. The manuscript benef ited from the helpful comments of Peter C. Hoch and Anton A. Reznicek.

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