Canadian Geography and Butterfly Distribution
Canada, with a land area of 9,922,335 square kilometres (almost 4 million square miles), is the second largest country in the world in area. It extends more than 5000 kilometres east to west from St. John's in Newfoundland to Victoria on Vancouver Island, and more than 4600 kilometres from the top of Ellesmere Island in the Arctic to Point Pelee in southern Ontario to the south. Most of this vast area, however, is sparsely populated, with the majority of Canada's 30 million inhabitants living in a narrow zone along Lake Ontario and in the St. Lawrence River Valley, an area that occupies less than 1 percent of the land area.
Politically, Canada was until recently divided into ten provinces that cross the southern half of Canada and two territories in the north. From east to west, the provinces are Newfoundland and Labrador, Nova Scotia, Prince Edward Island, New Brunswick, Quebec, Ontario, Manitoba, Saskatchewan, Alberta, and British Columbia, and the two territories were Northwest Territories and Yukon. On April 1, 1999, the eastern half of the mainland of the Northwest Territory, and most of the Arctic Islands, was made into the new territory of Nunavut.
Two life zones dominate Canada's landscape. The boreal forest, or Taiga Zone, that stretches from Newfoundland, the northern edge of the Great Plains, and the Rocky Mountain foothills northward to treeline, occupies fully 50 per cent of Canada's land mass or five million square kilometres; the Tundra Zone that stretches across northern Canada north of treeline, occupies another 25 per cent or 2.5 million square kilometres. These two life zones are the most sparsely populated parts of Canada, and have few roads to provide access for survey work on butterflies; the spotty distribution of butterflies on the maps for these areas reflects this paucity of available data.
Traditionally, the natural habitats of plants and animals in Canada have been arranged in five life zones: Tundra, Boreal (or Taiga), Cordillera, Prairie, and Mixed Deciduous Woodland.
For more information, see Terrestrial Ecozones of Canada on Environment Canada's web site.
Tundra Zone butterflies are most diverse in northern Yukon and the western Northwest Territories and show a rapid decline in diversity northwards in the Arctic Islands, eastward across northern Canada, and southward in alpine habitats in the mountains of Alberta and British Columbia. Forty-four species of butterflies have been recorded from the Tundra Zone, of which 32 are primarily tundra species. Of the 32 tundra-adapted species of butterflies in northern Yukon, 16 occur into southern British Columbia and Alberta, 11 occur as far east as northern Quebec, and six occur as far north as Ellesmere Island. The reason for this pattern is that during the last Ice Age (the Wisconsinan Glaciation), most of northern Canada was under ice, or too cold, making it impossible for butterflies to inhabit the area; most of the tundra-adapted species survived the Ice Age in the "Beringian Refugium", a large ice-free area in northern Yukon, Alaska, the exposed floor of the Bering Sea, and northeastern Siberia.
Following the deglaciation of Canada (during a period between 12,000 to 5000 years ago), these species dispersed northward and eastward with varying degrees of success. Many of the species in tundra habitats in the Rocky Mountains probably passed the Wisconsinan Glaciation in small refugia in the mountains. Among the most characteristic butterflies of the Tundra Zone are the Hecla Sulphur (Colias hecla), Labrador Sulphur (C. nastes), Arctic Fritillary (Boloria chariclea), Polaris Fritillary (B. polaris), Polixenes Arctic (Oeneis polixenes), Melissa Arctic (O. melissa), and White-Veined Arctic (O. bore).
The Boreal Zone is characterized by forests of spruce, poplar, Balsam Fir, Jack Pine, and White Birch. The Boreal Zone butterfly fauna has many species that occur in the southern part of the zone as extensions of species ranges from the Mixed Deciduous Woodland, Prairie, and Cordilleran Zones. Unlike the Tundra Zone, most butterflies characteristic of the Boreal Zone occur throughout the zone. The reason is that these butterflies, like the forests themselves, have reoccupied this formerly ice-covered part of Canada from farther south in the past 8000 years. As a result, we do not see significant subdivisions of the Boreal Zone; the differences in the fauna from region to region are largely determined by the influence of adjoining life zones. Some of the characteristic butterflies of the Boreal Zone are the Canadian Tiger Swallowtail (Papilio canadensis), Mustard White (Pieris oleracea), Pink-edged Sulphur (Colias interior), Taiga Alpine (Erebia mancinus), Jutta Arctic (Oeneis jutta), Atlantis Fritillary (Speyeria atlantis), and Bog Fritillary (Boloria eunomia). The ranges of many Boreal Zone species also extend slightly to extensively into the Cordilleran Zone and some, such as the Hoary Comma (Polygonia gracilis), Northern Blue (Lycaeides idas), and Grizzled Skipper (Pyrgus centaureae), have different subspecies in each zone.
The Cordilleran Zone is undoubtedly the most complex life zone in Canada, and the most varied in butterfly diversity with 184 recorded species. It is composed of a series of north-south mountain ranges that dissect the Zone; the mountain ranges in southern British Columbia, from east to west are the Rocky Mountains, Purcell Mountains, Selkirk Mountains, Monashee Mountains, Cascade Mountains, Coast Mountains, and Vancouver Island ranges. The Rocky Mountains and Coast Mountains continue northward through British Columbia, with numerous other ranges, largely inaccessible by road, between them in central and northern BC. Each range has moist forests of hemlock, spruce, fir, and cedar on the west slopes, alpine meadows along the tops, dry forests of pine and Douglas-fir on the east slopes, and arid valleys in between.
Each of these habitats has a significantly different butterfly community. The rainforests along the Pacific coast tend to be too wet and too cloudy to support many species of butterflies; moist conifer forests on the coast and farther inland are characterized by such species as the Hydaspe Fritillary (Speyeria hydaspe), Rosner's Hairstreak (Callophrys rosneri), and Clodius Parnassian (Parnassius clodius). Species characteristic of the drier forests are the Pale Swallowtail (Papilio eurymedon), PineWhite (Neophasia menapia), Barry's Hairstreak (Callophrys barryi), Thicket Hairstreak (C. spinetorum), and Lorquin's Admiral (Limenitis lorquini). Alpine habitats contain tundra species with ranges that extend southward in the mountains, like the Pelidne Sulphur (Colias pelidne skinneri), and Labrador Sulphur (C. nastes streckeri), as well as alpine species of the Cordilleran Zone, such as the Mead's Sulphur (C. meadii), Alberta Fritillary (Boloria alberta), and Lustrous Copper (Lycaenacuprea). More than a dozen butterfly species in Canada are largely restricted to the dry interior valleys of British Columbia. These are Great Basin species of the western United States with ranges that extend into Canada primarily in the Okanagan Valley, but also to a lesser extent in the Similkameen and Columbia River Valleys and the area around Kamloops. Some species that fall into this category are the Becker's White (Pontia beckerii), Desert Marble (Euchloe lotta), Lilac-bordered Copper (Lycaena nivalis), Behr's Hairstreak (Satyrium behrii), Western Green Hairstreak (Callophrys affinis), Pale Crescent (Phyciodes pallidus), Great Basin Wood-Nymph (Cercyonis sthenele), and Juba Skipper (Hesperia juba). Relatively few Cordilleran butterfly species are widespread throughout the zone; among these are the Spring White (Pontia sisymbrii), Northern Marble (Euchloe creusa), Mariposa Copper (Lycaena mariposa), Pacific Fritillary (Boloria epithore), and Field Crescent (Phyciodes pratensis). Other species are extremely rare and localized; the Indra Swallowtail (Papilioindra), Hoffmann's Checkerspot (Chlosyne hoffmanni), and Sonoran Skipper (Polites sonora) occur in Canada only in the Cascade Mountains in the vicinity of Manning Provincial Park. A few species occur in Canada only on Vancouver Island and limited areas of the adjacent mainland; these are the Western Sulphur (Colias occidentalis), Johnson's Hairstreak (Callophrys johnsoni), Great Arctic (Oeneis nevadensis), and Propertius Duskywing (Erynnis propertius).
In the northern portion of the Cordilleran Zone there are seven mountain ranges in Yukon and the western Northwest Territories. The best known of these ranges, in terms of butterfly diversity, is the Ogilvie Mountains north of Dawson, because of the available access to many habitats via the Dempster Highway. For selected areas, there are also good butterfly data from the St. Elias Mountains (mainly Kluane National Park), the Richardson Mountains, and the British Mountains. The general pattern in many of these northern mountain ranges is extensive tundra habitat at middle and higher elevations, dry, prairie-like steppe habitat on some south-facing slopes and river bluffs, and boreal forest habitat in the valleys. Only seven of Yukon's 87 species of butterflies have not been found in British Columbia. The butterfly diversity of the northern Cordilleran Zone is discussed below under Glacial and Post-glacial Butterfly Distributions.
The Prairie Zone can be subdivided into short-grass prairie, which predominates in southern Alberta, southern Saskatchewan, and southwestern Manitoba, and tall-grass prairie, which occurs in southeastern Manitoba. North of these areas is a large area of mixed-grass prairie, and north of this is a region called the aspen parkland, an area of mixture between the northern edge of the prairie and the southern limits of the Boreal Zone; the aspen parkland is characterized by prairie habitat on hilltops and south-facing slopes and by groves of aspen and spruce in the valleys and on north-facing slopes. Also within the Prairie Zone are "badlands", areas usually along river valleys characterized by severe erosion and sparse vegetation.
Some butterfly species are widely distributed in the Prairie Zone, such as the Grey Copper (Lycaena dione), Gorgone Checkerspot (Chlosyne gorgone), Alberta Arctic (Oeneis alberta), Garita Skipperling (Oarisma garita), and Plains Skipper (Hesperia assiniboia). Others occur primarily in the short-grass and mixed-grass prairie, including the Edwards' Fritillary (Speyeria edwardsii), Sagebrush Checkerspot (Chlosyne acastus), Ridings' Satyr (Neominois ridingsii), Uncas Skipper (Hesperiauncas), and Afranius Duskywing (Erynnis afranius). A few species occur in arid habitats in the Prairies and in the dry interior valleys of southern British Columbia, such as the Two-tailed Swallowtail (Papilio multicaudatus), Lupine Blue (Icaricia lupini), Arrowhead Blue (Glaucopsyche piasus), and the extremely rare Mormon Metalmark (Apodemia mormo). Five prairie species of skippers are extremely rare in Canada and have only been collected a few times; these are Small Checkered Skipper (Pyrgusscriptura), Pahaska Skipper (Hesperia pahaska), Rhesus Skipper (Polites rhesus), Oslar's Roadside Skipper (Amblyscirtes oslari), and Simius Roadside Skipper (A. simius). Three species of skippers are characteristic of tall-grass prairie and occur in Canada only in southern Manitoba, where they are extremely local; these are Poweshiek Skipperling (Oarisma poweshiek), Ottoe Skipper (Hesperiaottoe), and Dakota Skipper (H. dacotae).
Mixed Deciduous Woodland Zone
This zone, characterized mainly by beech, maple, oak, and Red and White Pine, is in southern Ontario and Quebec, south of the Canadian Shield, and in the Maritime Provinces of New Brunswick, Nova Scotia, and Prince Edward Island. A small area of this habitat is also found in extreme western Ontario and southeastern Manitoba. This is a diverse life zone in Canada, with 146 species of butterflies recorded from the zone and 56 species largely restricted to it in Canada. The zone can be subdivided into three parts: the Atlantic Maritime Subzone in the Maritime Provinces, the Great Lakes-St. Lawrence River Subzone in Quebec and in eastern and central Ontario, and the Carolinian Subzone in southern Ontario. The species characteristic of the Mixed Deciduous Woodland Zone are southern species that have expanded their ranges into eastern Canada to varying degrees. As a result, all 56 of the species characteristic of the zone occur in the Carolinian Subzone of southern Ontario, 39 of these also occur farther north in the Great Lakes-St. Lawrence River Subzone, and 15 also occur in the Maritime Provinces.
Butterfly species characteristic of the Carolinian Subzone include the Giant Swallowtail (Papiliocresphontes), Spicebush Swallowtail (P. troilus), Southern Cloudywing (Thorybes bathyllus), Sleepy Duskywing (Erynnis brizo), and Black Dash (Euphyes conspicua). Species that occur in both the Carolinian and Great Lakes-St. Lawrence River Subzones are the West Virginia White (Pieris virginiensis), Hickory Hairstreak (Satyrium caryaevorum), Edwards' Hairstreak (S. edwardsii), Juniper Hairstreak (Callophrys grynea), Appalachian Brown (Satyrodes appalachia), and Indian Skipper (Hesperia sassacus). Those that occur throughout the entire zone include the Harvester (Feniseca tarquinius), Henry's Elfin (Callophrys henrici), Harris's Checkerspot (Chlosyne harrisii), Baltimore Checkerspot (Euphydryas phaeton), Eastern Comma (Polygonia comma), Northern Pearly-Eye (Enodia anthedon), Little Wood-Satyr (Megisto cymela), and Pepper and Salt Skipper (Amblyscirtes hegon). The Mixed Deciduous Woodland Zone also contains disjunct populations characteristic of other zones, including prairie species such as the Garita Skipperling (Oarisma garita) and Gorgone Checkerspot (Chlosyne gorgone) in areas of relict prairie in Ontario, and Boreal Zone species such as the Pink-edged Sulphur (Colias interior) and Bog Copper (Lycaena epixanthe), which occur in bogs as far south as southern Ontario. The Mixed Deciduous Woodland Zone is also characterized by the high proportion of vagrant and migratory species that occur there. Thirty-one of the 35 species in this category in Canada have been recorded in this zone, and 19 of these have only been recorded there.
Thirty-five species of butterflies recorded from Canada are not resident species in Canada, but occur as seasonal migrants or strays from the south. Some of these, such as the Monarch (Danaus plexippus), Painted Lady (Vanessa cardui), American Lady (V. virginiensis), Red Admiral (V. atalanta) and Question Mark (Polygonia interrogationis), occur annually and widely and breed, with a full or partial return migration in the late summer and fall. Another six species - the Zebra Swallowtail (Eurytides marcellus), Checkered White (Pontia protodice), Little Yellow (Eurema lisa), American Snout (Libytheana carinenta), Variegated Fritillary (Euptoieta claudia), and Common Buckeye (Junonia coenia) regularly migrate to Canada, often with limited breeding, especially in southern Ontario. The remaining 24 species rarely if ever breed in Canada and most have been recorded only afew times.
Glacial and Post-Glacial Butterfly Distributions
As recently as 12,000 years ago, most of Canada was covered by massive ice sheets, the results of the most recent Ice Age. This period, termed the Late Wisconsinan glacial maximum, lasted from about 23,000 to 10,000 years ago, and reached its peak about 18,000 years ago. At this time the Laurentian Ice Sheet covered most of Canada from Newfoundland to the foothills of the Rocky Mountains in Alberta, the Innuitian Ice Sheet covered most of arctic Canada, and the Cordilleran Ice Sheet covered most of British Columbia and southern Yukon. During this period there were ice-free areas on the west coast and in the Arctic Islands, but these were probably not suitable for butterfly populations to survive and there is no indication that any did.
Four other ice-free areas (refugia) probably did support butterfly populations. The largest and most significant of these was the Beringian Refugium, which was a large ice-free area in northern Yukon, Alaska, the exposed floors of the Bering and Chukchi Seas, and northeastern Siberia. During this period, and during previous periods of glacial advances, the Beringian Refugium was not part of the North American region in its affinities but was effectively an eastward-extending peninsula of Asia. At that time this area was treeless, or almost so, with tundra and dry-steppe habitat dominating the landscape. In what remains of the Beringian Refugium in Yukon and Alaska, fossil remains of plants and animals characteristic of Asia can be found, but we also find extant populations of organisms, including butterflies, that show these same affinities. For example, the Green Marble (Euchloe naina) was thought to be restricted to mountain ranges in Siberia until a population was recently discovered in the Ogilvie Mountains in Yukon. Other species, such as the Phoebus Parnassian (Parnassius phoebus), Disa Alpine (Erebia disa), Mt. McKinley Alpine (E. mackinleyensis), Scree Alpine (E. anyuica), and Philip's Arctic (Oeneis rosovi), mirror this refugium by having ranges that extend into North America from Siberia in this unglaciated area. Other species, such as the Four-dotted Alpine (Erebia youngi) and Reddish Alpine (E. lafontainei), are restricted in distribution to the North American portion of Beringia and have their closest relatives, E. dabanensis Erschoff and E. kozhantshikovi Sheljuzhko respectively, restricted to the Siberian portion of Beringia. Many moths also show this same pattern of Siberian species and endemic species restricted in North America to the area of the Beringian Refugium (Lafontaine and Wood, 1988).
Three lines of evidence support the possibility that some species of butterflies may have persisted in small mountaintop refugia in the Rocky Mountains where the Laurentian and Cordilleran Ice Sheets came together. Geological findings show that some areas in the Rocky Mountains were not glaciated. There are relict populations of flightless, cold-adapted arthropods such as Rock Crawlers (family Grylloblattidae), distant relatives of crickets and cockroaches, living in these same areas. Isolated populations of cold-adapted butterflies, such as the Magdalena Alpine (Erebia magdalena) also live in these areas.
The third area of Canada that may have supported butterfly populations during the last Ice Age was the southern Prairies, including the Cypress Hills on the Saskatchewan/Alberta border. This area, however, was continuous with ice-free areas in the United States and it is not possible to determine whether the unusual species of butterflies that live in the area today have a long history there, or have moved in from farther south after the Ice Age.
The fourth possible butterfly refuge in Canada was along the east coast. This ice-free area was probably largely on the continental shelf and, except for islands like Iles-de-la-Madeleine and possibly some mainland areas, it is under the Atlantic Ocean today. Among east-coast endemic plants and animals that support the existence of this refugium are three butterfly species: the Short-tailed Swallowtail (Papilio brevicauda), Maritime Copper (Lycaena dospassosi), and Maritime Ringlet (Coenonympha nipisiquit).
Increasing world temperatures and drier conditions brought the last Ice Age to an end. The last remnants of the great Wisconsinan ice masses still persist today in Greenland, and also in Canada; the Barnes and Penny Ice Caps on Baffin Island, the Agassiz Ice Cap on Ellesmere Island, and the glaciers in the St. Elias Mountains in Kluane National Park, Yukon, are some of the larger remnants. As the ice sheets melted and withdrew from the land, over a long period from 15,000 to 7000 years ago, the plant and animal communities moved back into Canada, primarily from the south. The largest of these communities is the boreal forest, which now occupies about half of Canada. The boreal forest not only occupied a large portion of formerly glaciated Canada, but also spread over most of the Beringian Refugium in Yukon and Alaska, and forced the tundra and steppe butterflies there to retreat into suitable remaining habitat in the mountains. The relatively recent arrival and spread of the boreal forest in Canada explains why most Boreal Zone butterflies occur widely through the Zone and there is little geographical differentiation into subspecies. The butterflies that passed the Ice Age in the Beringian Refugium fall into two groups: species adapted to open boggy tundra spread widely across northern Canada after the glaciers melted; and species of specialized habitats such as dry-steppe slopes (e.g., Oeneis uhleri cairnesi) or rockslides (e.g., Erebia mackinleyensis) remained isolated in these habitats in Yukon and Alaska. Some alpine-adapted species spread southward in the mountain ranges of British Columbia and Alberta. The repopulation of the Cordilleran, Prairie, and Mixed Deciduous Woodland Zones from the south resulted in much partitioning in species ranges in these areas, reflecting the different habitats and climate zones being occupied.
Towards the latter stages of the Ice Age, between about 9000 and 6000 years ago, there was a dramatic warming trend called the hypsithermal. Warmer and drier conditions during this period resulted in the expansion of the prairies northward in Alberta into the Peace River area, and eastward from the Great Plains into the northeastern United States and southern Ontario. Remnants of this expansion persist today along the banks of the Peace River and in eastern North America. In these regions, forests have not been able to displace the prairie, mainly in dune areas and 'alvars', where the rock substrate is too close to the surface to allow trees to grow. These relict prairies support the Uhler's Arctic (Oeneis uhleri), Alberta Arctic (O. alberta), and Northern and Gorgone Checkerspots (Chlosynepalla and C. gorgone) in the Peace River area, and the Garita Skipperling (Oarisma garita), Large Marble (Euchloe ausonides), Melissa 'Karner' Blue (Lycaeides melissa samuelis), and Gorgone Checkerspot (Chlosyne gorgone) in Ontario.
Changing Butterfly Distributions
The ranges of some butterfly species change through time. Probably the most dramatic changes involve introduced species. The European Skipper (Thymelicus lineola), introduced at London, Ontario, about 1910, has become a major pest of Timothy Grass and is now abundant as far south as South Carolina and in parts of the west as far as Victoria, British Columbia. The Cabbage White (Pieris rapae), introduced at Quebec City about 1860, has spread throughout most of North America.
Among our native butterfly species, the most common pattern of change, unfortunately, is shrinking ranges as suitable habitat disappears, or is partitioned into remnants too small to support the butterfly populations. Many prairie species have become more sparsely distributed, or have disappeared, from the eastern portion of their ranges. For example, the Ridings' Satyr (Neominois ridingsii) and Uncas Skipper (Hesperia uncas) have disappeared from Manitoba and Edwards' Fritillary (Speyeria edwardsii) has disappeared from Manitoba and most of its former Saskatchewan range. The Karner Blue (Lycaeides melissa samuelis), Frosted Elfin (Callophrys irus), and Persius Duskywing (Erynnis persius persius) have been extirpated from Canada owing to loss of suitable habitat in the few remaining stands of native Lupine in southern Ontario.
Examples of the opposite trend are the Olympia Marble (Euchloe olympia) and Common Ringlet (Coenonympha tullia). The Olympia Marble, formerly a primarily prairie species, has expanded its range into eastern Canada in the past 30 years in dry abandoned farmland. The Common Ringlet was largely restricted to Boreal Zone habitats in eastern Canada but in the latter half of this century its range has dramatically expanded to the south through southern Canada and into the northeastern United States.
Sometimes it is difficult to determine whether range extensions are due to expanding ranges or better collecting efforts. The discovery of more than a dozen colonies of Gorgone Checkerspot (Chlosyne gorgone) in southeastern Ontario in 1996 is probably a combination of new collecting efforts in the area and expansion of remnant colonies into abandoned farmland and roadside habitats. The recent discovery of more than 100 colonies of Pearl Crescent (Phyciodes tharos) in eastern Ontario and western Quebec may be a similar phenomenon.
Butterfly enthusiasts are advised to watch for, and report, examples of range extensions, and known disappearances of species from areas formerly occupied.
Reproduced with permission from The Butterflies of Canada by Ross A. Layberry, Peter W. Hall, and J. Donald Lafontaine. University of Toronto Press; 1998. Specimen photos courtesy of John T. Fowler.
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