The purpose of this publication is to present a series of reports.... on the species composition and biogeography of selected taxa belonging to some of the major phylogenetic groups inhabiting the Mixedwood Plains Ecozone. We have attempted to include diverse taxa representing a wide range of structural and functional roles within the ecosystems of the Mixedwood Plains. The reports summarize available data on the status of species diversity in each group and assess the factors influencing species distributions and community composition in the Ecozone from the end of the Wisconsinan Glacial Maximum to the present. The information and interpretations are intended to provide the foundation of a comprehensive framework for analysing the status and dynamics of species level biodiversity in the Mixedwood Plains.

The Mixedwood Plains Ecozone of Canada comprises southern Ontario south of the Precambrian Shield and the St. Lawrence Valley of Quebec as far east as the region of Rivière-du-Loup (Fig. I-1). The Ecozone is the northernmost extension of the deciduous forest biome that extends throughout much of the eastern United States from the Ozark Plateau to the Appalachian Mountains. This biome is contiguous with two other Canadian Ecozones, the Atlantic-Maritime and Boreal Shield, and merges with the Prairie-Great Plains biome south and west of the Great Lakes. The geography, climate and soils of the Mixedwood Plains were summarized by Wicken (1986) and by the Ecological Stratification Working Group (1995), and these authors provided a brief list of some of the more conspicuous species of woody perennial plants and vertebrate animals. The reports presented here add substantially to the information available for assessing and characterizing the biodiversity of the Ecozone.

To understand and interpret current species and community diversity in the Mixedwood Plains Ecozone we must appreciate that it has developed over a relatively short period of time. Only 18000 years ago the Laurentide Ice Sheet covered all of southeastern Canada including the future Mixedwood Plains. By about 13000 years ago the ice sheet had receded northward to expose the Great Lakes Basin and by 11000 years ago most of the area now included in the Ecozone was ice free (Fig.I-2). At this time, the ecosystem was dominated by Spruce Parkland comprising open groves of White Spruce, Balsam Fir and Aspen mixed with tundra and grasslands. This community has no modern analog, but probably resembled open Spruce forests near the northern end of Lake Huron and on the eastern foothills of the Rocky Mountains. During the early Holocene, Spruce Parkland and its associated Pleistocene megafauna was replaced, first by a pine dominated forest and then by a mixture of shade-tolerant tree species including maples, birch, beech and hemlock. Much of the landscape was probably covered by savannah maintained by periodic burning and cutting carried out by humans. The Hypsithermal Interval between 5000 and 4000 years ago resulted in the decline of hemlock and the northern advance of several hardwood species, and culminated in the establishment of a modern mixed forest in the Great Lakes-St. Lawrence region during the late Holocene.

Throughout the Holocene, plant and animal species recolonized the Mixedwood Plains Ecozone from Pleistocene refugia distributed south of the maximum limit of the Laurentide Ice Sheet between the Ozark Plateau and the Atlantic Coast. Species dispersed northward following routes across, between and around the Great Lakes and their precursors, typically moving with other members of established communities but with numerous opportunities to develop new associations and interactions. The decompression of life zones that occurred during the Holocene resulted in a variety of distribution patterns among species inhabiting the Mixedwood Plains. Cold-adapted species from periglacial refugial areas invaded first, often leaving relict populations in suitable habitats in the Mixedwood Plains as they moved further north. Warm-adapted species colonized later, usually maintaining populations in their distributional centres in the southeastern United States while reaching their northern limits in the Mixedwood Plains or Boreal Shield Ecozones. Species adapted to prairie conditions colonized the Mixedwood Plains from the West during the Hypsithermal Interval, leaving relict populations in dune, alvar, savannah and wetland habitats when they were largely displaced with the return to cooler and wetter climate during the late Holocene. Consequently, the communities found in the Mixedwood Plains exhibit exceptionally high diversity, comprising many species that occur together only in this Ecozone. The species composition of these communities has been dynamic throughout the Holocene and continues to change extensively.

The recent history of species diversity in the Mixedwood Plains has been strongly influenced by European settlement, beginning with the harvesting of animal pelts for the fur trade during the 17th century. Forest clearance to supply lumber mills and open the landscape to agriculture had accelerating impact on native biodiversity throughout the 18th century. Most recently, growth of industry, urban centres and transportation corridors has reduced and fragmented forests, savannahs and wetlands, isolating many native populations and communities in tiny remnant patches of habitat. Populations of many naturalized introduced species have spread aggressively through the Mixedwood Plains during the past century, often at the expense of native biota. These trends have resulted in a somewhat ironic situation in that more species inhabit the Ecozone than at any previous point in the post-Wisconsinan period, but many survive there as isolated populations that may not be sustainable. Interpretation of changes in species diversity during the recent era of accelerating human impact is often difficult or impossible because we lack adequate baseline information on the condition of populations or communities prior to human intervention. We frequently find ourselves trying to understand changes without access to well documented information on either the species in question or the environmental stressors that influence their status. This problem is regularly compounded by the narrowly focussed and sectoral mandates of publicly funded organizations that hold information, and the lack of funds available for supporting compilation, evaluation, analysis and interpretation of existing data sets.

The taxonomic and ecological knowledge base varies considerably among the groups of organisms represented in the Mixedwood Plains. Vascular plants and vertebrate animals have been relatively well studied, and virtually all species expected to occur in the Ecozone have already been reported. The vulnerability of species in these groups to extirpation has become a preoccupation among biologists, resource managers and the public. By emphasizing the plight of charismatic endangered species we have drawn attention to the urgent need for conservation action. However, this approach has generated a variety of parallel protection and recovery initiatives that compete with one another for a severely limited pool of resources. More significantly, programs focussed on individual species have probably inhibited more holistic analyses of biodiversity in the Ecozone. Few people are aware that the vast majority of species in the Ecozone are microorganisms, non-vascular plants and invertebrate animals. These species comprise the infrastructure of our ecosystems and sustain many essential ecological processes, yet their biology is poorly known and many of them have not even been named or classified. The lack of names and diagnostic information for these species precludes ecological study and perpetuates our ignorance of their roles in maintaining the structural and functional integrity of our ecosystems. More extensive biotic inventories are urgently needed so that we can better understand the relationship between the species composition of our biological communities and their capacity to self-organize and self-regulate. To achieve real progress in conserving biodiversity we must incorporate concerns about endangered species into strategies that promote understanding and protection of species, communities and habitats representing all levels of ecosystem organization.

In conclusion, we should emphasize that the following reports are intended to provide an initial synthesis of available data on species diversity in the Mixedwood Plains Ecozone. We expect that these reports will be revised and updated as additional information comes to light, and hope that further contributions covering other groups will be forthcoming. Every species and clade in the Ecozone represents a unique opportunity to improve our ability to answer fundamental questions about our ecosystems. The most basic of these questions, "What species are present ?", demands expertise in systematics. Questions which are essentially about historical events, such as "Where did these species originate ?" or "How and when did they get here ?", require knowledge of systematics, genetics and biogeography. Questions dealing with function and process, such as "What are these species doing here ?" or "How do they interact with one another ?" can only be answered by testing the predictions of conceptual models derived from a synthesis of phylogenetic and historical information with behavioural and physiological data. We offer the following general recommendations to stimulate development of a framework to integrate various scientific perspectives into a comprehensive research and monitoring agenda for investigating biodiversity change in the Mixedwood Plains Ecozone.

RECOMMENDATIONS FOR MONITORING AND ASSESSING BIODIVERSITY CHANGE IN THE MIXEDWOOD PLAINS ECOZONE

1. Establish a network of diverse, dedicated, secure, study sites representing the special terrestrial and freshwater habitats of the Ecozone (eg. Great Lakes - St. Lawrence River; mesotrophic lakes and rivers of Manitoulin-Lake Simcoe Ecoregion; springs and streams; wetlands; relict Carolinian woodlands, prairies and dunes; alvars; Niagara Escarpment; characteristic soil types; etc.).

2. Select a range of study sites including protected areas and plots affected by various types and levels of disturbance resulting from human activities.

3. Arrange sites representing each type of habitat in transects traversing the Ecozone, whenever possible.

4. Foster development of multidisciplinary teams of qualified experts committed to assessing, evaluating and monitoring biodiversity at species, community and landscape levels.

5. Develop GIS frameworks to permit correlation of species richness and abundance data with other environmental variables.

6. Support holistic approaches that link efforts to protect species with conservation of the communities, habitats and landscapes that sustain them.

7. Design long term research to improve understanding of relationship between the species composition of communities and their structural and functional integrity.

8. Adopt and publish standards and protocols for data collection, management, analysis and interpretation.

9. Conduct inventories at study sites and establish baselines for monitoring special species and communities.

10. Include taxa and communities representing all levels of ecosystem organization, especially those implicated as agents or regulators of essential ecological processes.

11. Develop and maintain relational databases for special taxa to permit documentation of spatial and temporal changes and correlation of species data with other relevant information.

12. Complete systematic work on special taxa to support assessment, monitoring and conservation programs.

References

Dyke, A.S. and V.K. Prest. 1987. Palaeogeography of Northern North America, 18 000 to 5 000 Years Ago. Geological Survey of Canada, Map 1703a Scale 1 : 12 500 000.

Ecological Stratification Working Group. 1995. A National Ecological Framework for Canada. Agriculture and Agri-Food Canada, Research Branch, Centre for Land and Biological Resources Research and Environment Canada, State of the Environment Directorate, Ecozone Analysis Branch, Ottawa/Hull.

Wiken, E.B. (compiler). 1986. Terrestrial ecozones of Canada. Ecological Land Classification Series No. 19. Environment Canada, Hull, Que. 26 pp. + map.

Table of Contents:

• PTERIDOPHYTES

  Daniel F. Brunton Daniel Brunton Consulting Services

• VASCULAR PLANTS

  P.M. Catling and J. Cayouette Research Branch, Agriculture Canada Eastern Cereal and Oilseed Research Centre K.W. Neatby Building, Central Experimental Farm Ottawa, Ontario K1A 0C6

• FRESHWATER MOLLUSCA (Gastropoda and Bivalvia)

  David W. Barr Department of Invertebrate Zoology Royal Ontario Museum

• TERRESTRIAL MOLLUSCS

  F. Wayne Grimm For the Biosphere Environmental Consulting Group

• THE CRAYFISHES (Crustacea, Cambaridae)

  David W. Barr Department of Invertebrate Zoology Royal Ontario Museum

• MITES (Acari)

  Ian M. Smith, Evert E. Lindquist and Valerie Behan-Pelletier Biodiversity Assessment and Evaluation Research Branch, Agriculture Canada Eastern Cereal and Oilseed Research Centre K.W. Neatby Building, Central Experimental Farm Ottawa, Ontario K1A 0C6

• "SHORT-HORNED" BUGS (Homoptera-Auchenorrhyncha)
  

  K.G.A. Hamilton Biodiversity Assessment and Evaluation Research Branch, Agriculture Canada Eastern Cereal and Oilseed Research Centre K.W. Neatby Building, Central Experimental Farm Ottawa, Ontario K1A 0C6

• SAWFLIES (Hymenoptera: Symphyta)

  Henri Goulet Research Branch, Agriculture Canada Eastern Cereal and Oilseed Research Centre K.W. Neatby Building, Central Experimental Farm Ottawa, Ontario K1A 0C6

• BUTTERFLIES AND MOTHS (Lepidoptera)

  J.D. Lafontaine Biodiversity Assessment and Evaluation Research Branch, Agriculture Canada Eastern Cereal and Oilseed Research Centre K.W. Neatby Building, Central Experimental Farm Ottawa, Ontario K1A 0C6

• GROUND BEETLES (Coleoptera: Carabidae)
  

  Yves Bousquet Research Branch, Agriculture Canada Eastern Cereal and Oilseed Research Centre K.W. Neatby Building, Central Experimental Farm Ottawa, Ontario K1A 0C6

• FRESHWATER FISHES

  E. J. Crossman and E. Holm Department of Ichythyology and Herpetology Royal Ontario Museum

• BIRDS

  Daniel F. Brunton Daniel Brunton Consulting Services

• MAMMALS

  Andrew B. T. Smith Department of Zoology University of Toronto

  and

  Donald A. Smith Department of Biology Carleton University

• AGARICS, BOLETES AND CHANTERELLES

  S.A. Redhead Curator - National Mycological Herbarium (DAOM) Biological Resources Program Eastern Cereal and Oilseed Research Centre Research Branch, Agriculture and Agri-Food Canada Ottawa, ON   K1A 0C6

• AMPHIBIANS AND REPTILES

  Michael J. Oldham Natural Heritage Information Centre Ontario Ministry of Natural Resources P.O. Box 7000, Peterborough, ON K9J 8M5 oldhamm@gov.on.ca

• DRAGONFLIES AND DAMSELFLIES

  P. M. Catling, R. Hutchinson and B. Ménard Biological Resources Program Eastern Cereal and Oilseed Research Centre Agriculture and Agri-Food Canada Ottawa, ON   K1A 0C6