Northern Taxa Research Articles

Two Centuries of Change in the Native Flora of Franklin County, Massachusetts, U.S.A.

We examined changes in the native vascular flora of Franklin County, Massachusetts, a largely rural county with a long history of botanical investigation. The historical flora was documented using herbarium specimens and literature records, and the current flora was assessed in 10 years of field work starting in 2010. The county contains 26 towns, and apparent changes were based on town-level presence/absence. In total, 1205 species were recorded. Apparent losses from the historical flora totaled 5.6% of species, and apparent gains totaled 4.2%. Several families exhibited greater declines than the flora as a whole, including the Orchidaceae, Ophioglossaceae, Ranunculaceae, and Violaceae. Species dependent on fungi during at least part of their life cycle declined relative to other species, but were concentrated in a small group of families, including the Orchidaceae and Ophioglossaceae. Species with fleshy fruits increased relative to those with ant-dispersed seeds. Annuals increased relative to biennials and perennials, probably due to the increasing extent of ruderal habitats. Graminoids showed greater apparent increases than forbs, which may reflect undercollecting of the former taxa during the historical period. Species changes were related to habitat, with marked increases in plants of ruderal habitats, but other apparent changes may reflect sampling biases. Northern taxa appear to be declining relative to other species, particularly in towns at lower elevations. This study is one of several that have examined floristic changes in the northeastern United States and is part of a nascent literature suggesting that climate changes have altered the southern New England flora in the past century. Additional documentation of regional floras is needed to facilitate assessments of future floristic changes.

Post‐Pleistocene dispersal explains the Rapoport effect in North American salamanders

AbstractAimsIn many taxa, the latitudinal span of species' geographic ranges are positively correlated with median latitude (the Rapoport effect). This correlation is frequently explained as adaptation to contemporary climate; however, variability in post‐glacial range expansion among species could also explain this observation. We analyse geographic data for North American salamanders to test the potential causes of Rapoport effects.LocationTemperate North America.TaxonSalamanders (order Caudata).MethodsWe tested for a Rapoport effect by estimating correlations between the latitudinal midpoint and latitudinal range among species. Next, we manipulated species' latitudinal ranges by removing post‐glacial habitat and assessing the impact of species demonstrating post‐glacial range expansion in forming a Rapoport effect. We built ecological niche models for species found south of the Wisconsin Ice Sheet during the Last Glacial Maximum and transferred these models to post‐glacial areas. If dispersal is important in forming a Rapoport effect, then some species may tolerate northern climates but have not expanded northward as a result of variation in geographic access to post‐glacial habitats. We created binary ecological niche models by thresholding using the equal sensitivity and specificity value.ResultsWe recovered a Rapoport effect that was robust to the null models we tested. Analyses that manipulated ranges and species pools supported a role for variation in post‐glacial range expansion among species, especially for eastern North America. Results from transferring ecological niche models indicated that species have suitable habitat north of their range limit.Main conclusionsVariation in post‐glacial range expansion is important in shaping geographic range size clines among species in areas where climates changed rapidly, though we also found support for the climatic variability hypothesis. Post‐glacial colonization and range expansion likely plays an important role in forming latitudinal biodiversity gradients in northern taxa. While ecophysiology and biotic interactions have been emphasized as important contributors to diversity gradients, our study indicates that post‐glacial colonization also plays a key role in forming latitudinal gradients.

Fine-grained habitat-associated genetic connectivity in an admixed population of mussels in the small isolated Kerguelen Islands

Reticulated evolution -i.e. secondary introgression / admixture between sister taxa-is increasingly recognized as playing a key role in structuring infra-specific genetic variation and revealing cryptic genetic connectivity patterns. When admixture zones coincide with ecological transitions, the connectivity patterns often follow environmental variations better than distance and introgression clines may easily be confounded with local adaptation signatures. The Kerguelen mussels is an ideal system to investigate the potential role of admixture in enhancing micro-geographic structure, as they inhabit a small isolated island in the Southern Ocean characterized by a highly heterogeneous environment. Furthermore, genomic reticulation between Northern species (M. edulis, M. galloprovincialis and M. trossulus) and Southern species (M. platensis: South America and the Kerguelen Islands; and M. planulatus: Australasia) has been suspected. Here, we extended a previous analysis by using targeted-sequencing data (51,878 SNPs) across the three Northern species and the Kerguelen population. Spatial structure in the Kerguelen was then analyzed with a panel of 33 SNPs, including SNPs that were more differentiated than the genomic average between Northern species (i.e., ancestry-informative SNPs). We first showed that the Kerguelen lineage splitted very shortly after M. edulis and M. galloprovincialis initiated speciation, and it subsequently experienced admixture with the three Northern taxa. We then demonstrated that the Kerguelen mussels were significantly differentiated over small spatial distance, and that this local genetic structure was associated with environmental variations and mostly revealed by ancestry-informative markers. Simulations of admixture in the island highlight that genetic-environment associations can be better explained by introgression clines between heterogeneously differentiated genomes than by adaptation.

Cold tolerance in the genus Arabidopsis.

Cold tolerance is an important factor limiting the geographic distribution and growing season for many plant species, yet few studies have examined variation in cold tolerance extensively within and among closely related species and compared that to their geographic distribution. This study examines cold tolerance within and among species in the genus Arabidopsis. We assessed cold tolerance by measuring electrolyte leakage from detached leaves in multiple populations of five Arabidopsis taxa. The temperature at which 50% of cells were lysed was considered the lethal temperature (LT50 ). We found variability within and among taxa in cold tolerance. There was no significant within-species relationship between latitude and cold tolerance. However, the northern taxa, A. kamchatica, A. lyrata subsp. petraea, and A. lyrata subsp. lyrata, were more cold tolerant than A. thaliana and A. halleri subsp. gemmifera both before and after cold acclimation. Cold tolerance increased after cold acclimation (exposure to low, but nonfreezing temperatures) for all taxa, although the difference was not significant for A. halleri subsp. gemmifera. For all taxa except A. lyrata subsp. lyrata, the LT50 values for cold-acclimated plants were higher than the January mean daily minimum temperature (Tmin ), indicating that if plants were not insulated by snow cover, they would not likely survive winter at the northern edge of their range. Arabidopsis lyrata and A. kamchatica were far more cold tolerant than A. thaliana. These extremely cold-tolerant taxa are excellent candidates for studying both the molecular and ecological aspects of cold tolerance.

The mystery of the origins of Cebus albifrons malitiosus and Cebus albifrons hypoleucus: mitogenomics and microsatellite analyses revealed an amazing evolutionary history of the Northern Colombian white-fronted capuchins

Knowledge of the genetic units of species is fundamental to the conservation of biodiversity. This is true for all regions, including the Neotropics where the Earth has its greatest diversity, including roughly 34% of primate species, a group that has almost 60% of its taxa threatened with extinction. The untufted (gracile) capuchins are medium-sized Neotropical primates, traditionally classified in four species: Cebus albifrons, C. capucinus, C. olivaceus, and C. kaapori. They have a very confusing intra-specific systematics with a large number of fragmented and isolated populations throughout their geographical distributions. We sequenced a large sample of gracile capuchins, including all of the recognized species, to offset the paucity of phylogenic and phylogeographic data regarding this group and to try to understand their phylogeny and evolution. A set of 189 gracile and robust capuchins were sequenced for their mitogenomes whereas another set of 394 gracile and robust capuchins were sequenced at two individual mitochondrial genes (mtCOI-COII). Additionally, 41 Colombian gracile capuchins were geno typified at eight nuclear DNA microsatellites. Our main findings are as follows: (1) Nineteen different groups of gracile capuchin were detected with the mitogenomics data set and more than twenty significant groups and sub-groups were identified with the mtCOI-COII genes; (2) The temporal splits of the older gracile capuchin haplogroups expanded between 2 and 4 million years ago (MYA), during the Pliocene; (3) The two most northern taxa of Colombian C. albifrons (malitiosus and hypoleucus) are the same taxon (C. a. hypoleucus) as was claimed by Cabrera. This taxon represents an old colonization event from the Amazon to current northern Colombia. It is intensely hybridized (evidence from both mitochondrial and nuclear genes) with a haplogroup of C. capucinus (H3) and also has an influx of robust capuchins; (4) Three different and independent migrations of C. albifrons from the Amazon arrived to northern Colombia giving rise to C. a. hypoleucus (including malitiosus), C. a versicolor (including leucocephalus, cesarae, and pleei), and C. a. adustus; (5) On the Caribbean island of Trinidad, two different gracile capuchin taxa exist, one autochthonous, which could correspond to a fourth migration into northwestern South America (C. a. trinitatis) and probably another one, introduced more recently (C. olivaceus brunneus); (6) The values of the genetic distance analyses, the inexistence of reciprocal mitochondrial monophylia for many clades of gracile capuchins and the strong hybridization detected with nuclear microsatellites, especially among hypoleucus (malitiosus), C. capucinus-H3, versicolor, and cesarae, support that all the gracile capuchins belong to one unique superspecies: C. capucinus (senior name for all the gracile capuchins).

Phylogeographic structure in long-tailed voles (Rodentia: Arvicolinae) belies the complex Pleistocene history of isolation, divergence, and recolonization of Northwest North America's fauna.

Quaternary climate fluctuations restructured biodiversity across North American high latitudes through repeated episodes of range contraction, population isolation and divergence, and subsequent expansion. Identifying how species responded to changing environmental conditions not only allows us to explore the mode and tempo of evolution in northern taxa, but also provides a basis for forecasting future biotic response across the highly variable topography of western North America. Using a multilocus approach under a Bayesian coalescent framework, we investigated the phylogeography of a wide‐ranging mammal, the long‐tailed vole, Microtus longicaudus. We focused on populations along the North Pacific Coast to refine our understanding of diversification by exploring the potentially compounding roles of multiple glacial refugia and more recent fragmentation of an extensive coastal archipelago. Through a combination of genetic data and species distribution models (SDMs), we found that historical climate variability influenced contemporary genetic structure, with multiple isolated locations of persistence (refugia) producing multiple divergent lineages (Beringian or northern, southeast Alaska or coastal, and southern or continental) during glacial advances. These vole lineages all occur along the North Pacific Coast where the confluence of numerous independent lineages in other species has produced overlapping zones of secondary contact, collectively a suture zone. Finally, we detected high levels of neoendemism due to complex island geography that developed in the last 10,000 years with the rising sea levels of the Holocene.

영흥도의 식물상

We have investigated the flora of Yeongheungdo Island in Ongjin-gun, Incheon. A total of 13 separate field trips were carried out from March 2012 to October 2013. As a result, 302 taxa including 80 families, 211 genera, 261 species, 6 subspecies, 31 varieties and 4 forms were identified. These include the following: 1 taxon protected under the Act on the Protection and Management of Wildlife, 3 Korean endemic taxa, 8 floristic indicator species including 2 taxa of grade V, 3 of grade II and 3 of grade I, 33 naturalized taxa with the naturalization rate of 10.9% and 1 northern taxon vulnerable to climate change.

Redescription of Eremiascincus fasciolatus (Günther, 1867) (Reptilia: Squamata: Scincidae) with clarification of its synonyms and the description of a new species.

We present an assessment of the systematic status of populations currently assigned to Eremiascincusfasciolatus across Australia using morphological data. Our analyses show that these populations actually comprise four species: a large and robust, narrow-banded taxon from eastern Queensland and three slender, desert-dwelling taxa from the western, northern, and south-eastern Australian arid zone respectively. These data necessitate: 1) the redescription of E.fasciolatus, a species endemic to the dry forests of eastern Queensland, 2) the resurrection of E. pallidus for the western taxon, 3) the resurrection of E. intermedius for the northern taxon, and 4) the description of the south-eastern desert-dwelling taxon, which largely occurs in the Lake Eyre Basin, as a new species. The new species, Eremiascincusphantasmus sp. nov., can be distinguished from congeners by its large size, pale color, depressed snout, and small circular ear opening, as well as by several scale characteristics. Body proportions, a depressed snout, small ear opening, and pale color suggest that this species is fossorial and predominantly occurs in habitats with loose substrate, such as dune systems and sandy plains. A synopsis of each species and a key to the narrow-banded species of Eremiascincus are provided.

The most complete known Neogene Glyptodontidae (Mammalia, Xenarthra, Cingulata) from northern South America: taxonomic, paleobiogeographic, and phylogenetic implications

ABSTRACT The knowledge of northern South American Glyptodontidae (Mammalia, Xenarthra, Cingulata) is very scarce compared with that of southern South American taxa, which have been systematically studied since the 19th century. Recently, the northern taxa (originally assigned to the Glyptodontidae Propalaehoplophorinae Asterostemma and Propalaehoplophorus) have been reinterpreted as basal Glyptodontinae, belonging to the new genus Boreostemma. In this contribution, we present and describe the most complete Neogene Glyptodontidae from northern South America (middle Miocene of the Honda Group, La Venta, Colombia), and its main taxonomic, paleobiogeographic, and phylogenetic implications. This new material expands the morphological characterization of B. acostae and corroborates differences compared with Glyptodontidae from Miocene southern South America. A cladistic analysis corroborates the monophyly of the Glyptodontinae, that B. acostae and B. venezolensis being the sister group of the remaining taxa of Glyptodontinae. The traditionally recognized genera (e.g., Glyptodon and Glyptotherium) constitute natural groups. Whereas the Miocene seems to represent a diversification period for Glyptodontidae in southern South America, the recorded taxa in northern South America are restricted with certainty only to the Glyptodontinae Boreostemma.

Revisiting genetic structuring in spotted gums (genus Corymbia section Maculatae) focusing on C. maculata, an early diverged, insular lineage

Species delineation in the spotted gum complex was revisited focusing on Corymbia maculata. This study expands the range of C. maculata analysed with microsatellite markers to include populations from the north of the species range. It supported earlier findings that it is a cohesive genetic entity, well resolved from northern spotted gum taxa, Corymbia citriodora and Corymbia henryi; and inferences that its insularity is due to early lineage divergence and historical isolation. The northern extent of C. maculata sampled, as defined by chloroplast and nuclear genomes predominantly of C. maculata character, was the location of Kiwarrak, south of the Manning River near Taree in New South Wales. Trees from a recognised intergrade zone at the Yarratt locality, around 26 km north of Kiwarrak, also possessed a uniquely C. maculata chloroplast haplotype, but their nuclear genomes were predominantly of northern taxa ancestry. Range expansion of northern taxa leading to southerly gene movement into populations formerly C. maculata, would account for this apparent instance of chloroplast capture. Two subpopulations were identified in C. maculata, a northern population of which the Ourimbah locality was the most southerly studied, and a southern population of which Wingello was the most northerly locality studied. Diminished levels of northern taxa ancestry, i.e. C. citriodora or C. henryi, in individuals from the southern, relative to the northern subpopulation of C. maculata, suggested that secondary contact with northern taxa contributes to its substructure.

Polytrichum formosumvar.densifolium(Musci: Polytrichaceae) New to Missouri and the Interior Highlands of North America

Abstract. Polytrichum formosum var. densifolium is reported for Warren County, Missouri. Warren County is immediately north of the Missouri River and lies within the Border County Region, Interior Highlands of North America. This mostly northern taxon also occurs near Missouri in Tennessee. Unpublished molecular data indicate the taxon may be better placed in Polytrichum rather than Polytrichastrum.

A mitochondrial-DNA-based phylogeny for some evolutionary-genetic model species of Colias butterflies (Lepidoptera, Pieridae)

We study the phylogenetic relationships among some North American Colias (“sulfur”) butterflies, using mitochondrial gene sequences (ribosomal RNA, cytochrome oxidase I+II) totaling about 20% of the mitochondrial genome. We find that (1) the lowland species complex shows a branching order different from earlier views; (2) several montane and northern taxa may be more distinct than in earlier views; (3) one morphologically conservative Holarctic assemblage, C. hecla, is differentiated at the molecular-genetic level into at least three taxa which occupy distinct positions in the phylogeny and are sisters to diverse other taxa. These conclusions, constituting phylogenetic hypotheses, are supported by parsimony, maximum-likelihood, and Bayesian reconstruction algorithms. They are tested formally, by interior branch tests and paired-site tests, against alternative hypotheses derived from conventional species and subspecies naming combinations. In all cases our hypotheses are supported by these tests and the conventional alternatives are rejected. The “barcoding” subset of cytochrome oxidase I sequence identifies only some of the taxa supported by our full data set. Comparison of genetic divergence values among Colias taxa with those among related Pierid butterflies suggests that species radiations within Colias are comparatively younger. This emerging Colias phylogeny facilitates comparisons of genetic polymorphism and other adaptive mechanisms among taxa, thereby connecting micro- and macro-evolutionary processes.

Genetic structuring in the spotted gum complex (genus Corymbia, section Politaria)

Spotted gums (genus Corymbia, section Politaria) occur as a species replacement series along the eastern seaboard of Australia, their distributions marked by regions of disjunction and sympatry. Their taxonomy remains controversial, with species assignment often challenging and reliant on knowledge of geographic origin as well as subtle morphological or leaf-oil variation. In the present paper, we explore a classification for spotted gums, without assuming predefined geographic or taxonomic groups but instead using genetic structure at microsatellite marker loci (n = 9) and a Bayesian model-based clustering approach implemented in Structure software. The C. torelliana outgroup (n = 21; section Cadagaria) formed a well resolved cluster (minimum pairwise Fst = 0.19). Four populations were evident within the spotted gums (n = 93) but structure was weak (pairwise Fst range 0.13–0.05). Geographic distance, topography and distribution disjunction were major determinants of structure, with migration among populations approximating a linear stepping-stone model. Corymbia maculata was resolved as a taxon and had the greatest genetic distance from any other population (minimum pairwise Fst 0.08). Three clusters were evident within the northern taxa but alignment with taxonomic groupings was poor. C. citriodora material from north of a major disjunction in central Queensland formed a Northern population. C. citriodora, C. variegata and C. henryi material south of this disjunction but north of the Border Range, formed a Central population, whereas a Southern population comprised C. variegata and C. henryi from predominately south of the Border Range.

A reconnaissance of population genetic variation in arctic and subarctic sulfur butterflies (Coliasspp.; Lepidoptera, Pieridae)

Genotype–phenotype–environment interactions in temperate-zone species of Colias Fabricius, 1807 have been well studied in evolutionary terms. Arctic and alpine habitats present a different range of ecological, especially thermal, conditions under which such work could be extended across species and higher clades. To this end, we survey variation in three genes that code for phosphoglucose isomerase (PGI), phosphoglucomutase (PGM), and glucose-6-phosphate dehydrogenase (G6PD) in seven arctic and alpine Colias taxa (one only for G6PD). These genes are highly polymorphic in all taxa studied. Patterns of variation for the PGI gene in these northern taxa suggest that the balancing selection seen at this gene in temperate-zone taxa may extend throughout northern North America. Comparative study of these taxa may thus give insight into the mechanisms driving genetic differentiation among subspecies, species, and broader clades, supporting the study of both micro- and macro-evolutionary questions.

Taxonomic status of Triturus vittatus (Amphibia: Salamandridae) in western Turkey: trunk vertebrae count, genome size and allozyme data

AbstractThe banded newt, Triturus vittatus is suggested to consist of two species (T. ophryticus and T. vittatus). The northern taxon, T. ophryticus, is subdivided into two geographic fragments: the "western group" of populations from western Anatolian Turkey, and the "eastern group" distributed in the remaining part of the Pontic Turkey and western Caucasus. The western samples are characterized by a peculiar combination of various features. In this group the modal number of trunk vertebrae is equal to 12, like in T. v. vittatus and T. v. cilicensis, whereas the eastern group of T. ophryticus has 13 vertebrae. The amount of DNA per diploid nucleus, determined by flow cytometry, is higher in the western group (66.8-68.8 pg vs. 62.5-63.7 pg in the eastern group). Significant differences between both groups of T. ophryticus were revealed in allozymes (DNei'72 = 0.383 in average) as well. We allocate the western group of T. ophryticus to a separate subspecies, Triturus ophryticus nesterovi, subsp. nov. A paleogeographic scenario for T. vittatus and other newts is proposed. The taxonomic structure of the paraphyletic genus Triturus is discussed. We proposed to split the genus in four monophyletic genera Triturus sensu stricto, Lophinus, Mesotriton and Ommatotriton.

Systematics of sphagnum frogs of the genus Philoria (Anura: Myobatrachidae) in eastern Australia, with the description of two new species

Analyses of allozyme and mitochondrial nucleotide sequence variation in Philoria from northeastern NSW and southeastern Queensland revealed that there are more species than the three that are currently recognized. In addition to the three species presently recognized P. kundagungan, P. loveridgei, and P. sphagnicolus, another two species P. pughi n.sp. and P. richmondensis n.sp. were recognized under the evolutionary species concept. All species are allopatric. Each of the five species had two or more fixed genetic differences with all other species. Additionally, each species possessed two or more unique allozyme characters (apomorphies). Each species had strongly supported reciprocally monophyletic mitochondrial haplotypes in comparison with each of the other species. Multivariate morphometric analysis was able to distinguish P. sphagnicolus from the remaining four northern taxa but was unsuccessful in reliably distinguishing the two new species. Mating call analysis identified two distinct call groups: P. sphagnicolus and the remaining species, the latter showing little discrimination between species. The distribution of Philoria in NSW and Queensland shows a strong association with high rainfall rainforest at mid to high altitudes (above 600 m elevation). The habitat of all species is remarkably similar, all are found predominantly in the headwaters of rainforest streams or soaks on the forest floor. All species lay their eggs in nests in the ground, where the larvae remain throughout their entire development until they emerge post metamorphosis. It was confirmed that nests where the embryos were at an early stage of development were of two types: foaming egg masses, and nests containing a non-foaming jelly substance. All species are limited in their distribution. In particular P. richmondensis is in need of special conservation consideration, as it is known from only three localities within a very small range. A number of populations in southeastern Queensland and northern NSW await molecular analysis to be identified with certainty.

Phylogeny and Historical Biogeography of New Zealand Indigenous Aphidini Aphids (Hemiptera, Aphididae): An Hypothesis

Abstract Aphids (Hemiptera: Sternorrhyncha: Aphididae) are most diverse in the temperate northern hemisphere, with only a few lineages native to the southern hemisphere. The highly diverse subfamily Aphidinae probably gained its dominance from a successful northern hemisphere radiation in the Tertiary. A few species in the tribe Aphidini, however, are indigenous to Gondwanan regions, including New Zealand and Australia. The conventional view is that these species dispersed to the south from the northern hemisphere after the main Tertiary radiation. We tested this hypothesis in a phylogenetic context by reconstructing relationships among New Zealand indigenous Aphidini, as well as their relationships to several northern taxa. Phylogenies were reconstructed from molecular data using independent and combined analyses of mitochondrial tRNA leucine + cytochrome oxidase II and nuclear elongation factor-1α (EF1α) sequences, with both parsimony and maximum likelihood methods. These analyses recovered a highly sup...

The phytogeography of Denmark revisited

Patterns of vascular plant diversity in Denmark are examined, based on the most recently published Danish Flora. The highest diversity is found on the major isles of Sjaelland, Mon, Falster and Bornholm, but many rare taxa occur in Jylland. Two different cluster analyses suggest a division of Denmark into six phytogeographical regions, which only partly supports earlier, more subjective divisions of Denmark. Our results suggest that north- and northwestern Jylland and the isles of Laeso and Anholt belong to the boreo-nemoral phytogeographical region, due to their high number of northern taxa, which clearly differentiate them from the rest of Denmark, despite the lack of typical boreo-nemoral tree species, such as Pinus sylvestris. Because the tree component of vegetation often has been changed by man, the classical division of Scandinavia based on a few woody species is inappropriate. We conclude that tree-species oriented approaches are invalid for phytogeographical classifications. Classification, based on the whole flora, and if possible also involving environmental information, is likely to be more successful and should be addressed in future phytogeographical studies.

Rock-wallaby Biology and Management: Synthesis and Directions for Future Research.

This paper is a summary and overview of the National Rock-wallaby Symposium held in the Flinders Ranges, South Australia in November/December 1994. Whilst no rock-wallaby taxon of full specific rank is critically endangered, many distinct populations are at immediate risk of extinction. In particular, there is a strong north-south gradient in the conservation status of rock-wallabies. Southern taxa are more threatened than northern taxa, and within species, southern populations are more threatened than northern ones. A clear agenda for future research emerged. Much of this agenda can usefully be placed in the "declining population paradigm" recently identified by Caughley (1994). The threatening process most clearly indicated is predation by foxes, but whether this applies to rock-wallaby populations throughout Australia needs to be determined. Until it is, any manipulations of predation pressure should be treated as experiments. To measure the success of such manipulations, improved methods of population monitoring must be developed. Finally, the level of knowledge about rock-wallabies must be improved, both at the broad scale of taxonomy and distribution, and at the fine scale of detailed studies of the ecology and behaviour of particular populations.

INSECTS OF THE BOREAL ZONE OF CANADA

AbstractThe boreal zone of Canada extends across the continent over millions of square kilometres. Characterizing the insects of this cool temperate zone is especially important for an understanding of the Canadian fauna in general, and for northern forestry. The boreal zone supports simple coniferous forests with some deciduous trees and an understory of a few common vascular plants, mosses, and lichens. This enormous area of apparently similar vegetation nevertheless shows very great spatial and temporal heterogeneity, with a wide range of subhabitats. Aquatic habitats of many different kinds are especially well represented in the zone. The diversity of terrestrial habitats is maintained chiefly by disturbance, especially fire and seasonal flooding, and contributes greatly to faunal diversity.About 22 000 insect species are estimated to occur in the zone, far fewer than in more southern zones. Northern taxa, notably Diptera, are relatively well represented. The distributions and patterns of variation of the species are summarized. About half have transcontinental ranges, and many occur also in forested habitats in the western mountains south of the boreal zone. About 8% of the species appear to be holarctic. Few species that occur in the boreal zone are strictly confined to it, however. Generalist species in fresh water and other widespread habitats are conspicuous. Many species are centred farther south, and extend northward into the zone to varying degrees.Adaptations to northern conditions have been reported in many boreal insects. For example, the short growing season is reflected by the prevalence of univoltine species. Insects survive the long cold winters by cold-hardiness and dormancies. Species from disturbed habitats disperse widely. The limited diversity of resources is confirmed by the fact that the food range of some groups of herbivores is wider than in their southern relatives.Boreal ecosystem relationships are complex, especially relative to the arctic. Numerous associations among insects, and between insects and other organisms, have been demonstrated. However, some evidence suggests that the structure of northern biotic communities might depend more on the tolerances of individual species than on interactions among the species.The population dynamics of boreal forest insects, notably the spruce budworm, are discussed. In view of the spatial and temporal complexity of the boreal zone, the diversity of interactions with abiotic and biotic factors, and the prevalence of data that correlate with rather than explain population changes, our current failure to understand “outbreaks” of certain boreal insects is not surprising, because many factors probably combine to determine the population of a given species at a given lime and place.Information on most aspects of the composition and biology of the boreal fauna is incomplete. Data on boreal species have been collected chiefly in southern transitional ecosystems adjacent to boreal zones, rather than in truly boreal systems. Basic taxonomic information on several important taxa, as well as detailed taxonomic and morphometric information about individual species, is especially scanty. However, substantial and coordinated studies of boreal faunas will yield information of great interest and value. Some approaches relevant to further work in taxonomic and ecological arenas are suggested.