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1.
In Lake Baikal Elodea canadensis Michx. was first observed at the end of the 1970's.Suggestions have been made as to the bringing of E. canadensis to Baikal by aquarists or by transport vehicles and transport together with fishes taken from lakes of the Urals where mass development of the plant was observed at the beginning of the present century. The spread of E. canadensis along Lake Baikal must be due to navigation, but natural factors also affect its spread.The quantitative biomass development of E. canadensis in various areas of the lake is reviewed, and discussed in relation to historical aspects of spread and regulation by environmental factors.The fast spread of E. canadensis, its high competitive quality and metabolic capacities for purifying sewage waters deserve attention.Expansion of E. canadensis may be referred to as a catastrophic phenomenon. Its effect has now covered practically the whole perimeter of Lake Baikal. 相似文献
2.
Elodea canadensis Michx. was first observed in Lake Baikal at the end of the 70's. E. canadensis was probably introduced to Baikal by aquarists or by transport vehicles and transport together with fishes taken from lakes of the Urals, where mass development of the plant was observed at the beginning of the present century. The spread of E. canadensis along lake Baikal may be due to navigation, but natural factors also affect its spread.The fast spread of E. canadensis, its high competitive quality and metabolic properties for purifying sewage waters are of interest.The expansion of E. canadensis may be considered a catastrophic phenomenon; its effect now covers practically the whole perimeter of Lake Baikal. 相似文献
3.
Huan Lu Lifang Xue Jiliang Cheng Xianghong Yang Hongjie Xie Xiaoling Song Sheng Qiang 《Plant, cell & environment》2020,43(6):1394-1403
Solidago canadensis, originating from the temperate region of North America, has expanded southward to subtropical regions through polyploidization. Here we investigated whether freezing tolerance of S. canadensis was weakened during expansion. Measurement of the temperature causing 50% ruptured cells (LT50) in 35 S. canadensis populations revealed ploidy-related differentiation in freezing tolerance. Freezing tolerance was found to decrease with increasing ploidy. The polyploid populations of S. canadensis had lower ScICE1 gene expression levels but more ScICE1 gene copies than the diploids. Furthermore, more DNA methylation sites in the ScICE1 gene promoter were detected in the polyploids than in the diploids. The results suggest that promoter methylation represses the expression of multi-copy ScICE1 genes, leading to weaker freezing tolerance in polyploid S. canadensis compared to the diploids. The study provides empirical evidence that DNA methylation regulates expression of the gene copies and supports polyploidization-driven adaptation to new environments. 相似文献
4.
Huiyuan Cheng Shu Wang Mei Wei Bingde Wu Daolin Du Congyan Wang 《Population Ecology》2021,63(4):290-301
Reproductive allocation (RA) plays a vital role in the development of ecological strategies during the life cycle of plant species. Invasive alien plants (IAP) may exist at various invasion degrees across a gradient of the colonization process with several grades of relative abundances in the occupied environments. The progressive variation in the invasion degree of IAP has the potential to modify their RA strategy. This study purposes of estimating the RA strategy of the IAP Solidago canadensis L. and the correlations among RA of S. canadensis, the invasion intensity of S. canadensis, the invasiveness of S. canadensis, and the community invasibility across a gradient of invasion degrees by using the field sampling experiment. The height and relative abundance of S. canadensis did not remarkably affect its RA. The RA of S. canadensis was positively related to its reproductive biomass and total biomass. The key reason may be that plant individuals with higher total biomass can allocate more resources into sexual reproduction. The RA of S. canadensis was positively related to its invasiveness. Thus, the RA of S. canadensis may be crucial to its invasiveness. 相似文献
5.
Tsuga canadensis (L.) Carr. forests of the southern Appalachian Mountains are currently facing imminent decline induced by a nonnative insect
pest, the hemlock woolly adelgid (Adelges tsugae Annand). To effectively manage these forest systems now and in the future, land managers need baseline data on forest structure
and dynamics prior to large-scale Tsuga canadensis mortality. Most of our knowledge concerning the dynamics of Tsuga canadensis forests comes from more northern locations such as the Great Lakes region and New England and, therefore, may not pertain
to the ecological systems found within the southern Appalachian Mountains. We examined the structure and canopy dynamics of
four Tsuga canadensis forest stands within the Cataloochee watershed, in the far eastern part of Great Smoky Mountains National Park (GSMNP). We
characterized the environmental settings and vertical forest layers, as well as the diameter and age-structures of each Tsuga canadensis forest stand. These environmental and structural data showed that there were indeed differences between forest stands with
and without successful Tsuga canadensis regeneration. The two forest stands exhibiting successful Tsuga canadensis regeneration were located above 1,000 m in elevation on well-drained, moderately steep slopes and had the greatest canopy
openness. Structural data from these two forest stands indicated a history of more continuous Tsuga canadensis regeneration. We also constructed disturbance chronologies detailing the history of canopy response to disturbance events
and related these to Tsuga canadensis regeneration within each forest stand. Student t-tests adjusted for unequal variances indicated significant differences in the number of release events per tree between forest
stands with and without successful Tsuga canadensis regeneration. While forest stands with successful Tsuga canadensis regeneration were more frequently disturbed by minor to major canopy disturbances, events of moderate intensity were found
to be most significant in terms of regeneration. These data will be of value to land managers maintaining stands of Tsuga canadensis where treatment for hemlock woolly adelgid infestation has been successful. In areas where treatment is impractical or unsuccessful,
land managers will be able to use these data to restore Tsuga canadensis forests after the wave of hemlock woolly adelgid induced mortality has passed.
As of August 2008, Joshua A. Kincaid will be a member of the Environmental Studies program at Shenandoah University in Winchester,
Virginia, USA 相似文献
6.
Three subspecies of sandhill crane (Grus canadensis) are recognized in the Midcontinental population, the lesser (Grus c. canadensis), Canadian (G. c. rowani), and greater (G. c. tabida). Blood samples collected on the population's primary spring staging area in Nebraska, U.S.A., were used to resolve the genetic relationship among these subspecies. Phylogenetic analysis of 27 G. canadensis, by DNA sequencing of a 675 bp region of the mtDNA, supports the subspecies designations of G. c. canadensis and G. c. tabida. G. c. rowani individuals were intermediate with each of the other two subspecies. Genetic divergence ranged from 6.5 to 14.5% between G. c. canadensis and G. c. tabida, 0.5 to 6.6% within G. c. canadensis, and 0.1 to 6.0% within G. c. tabida. Sufficient DNA for analysis was obtained from shed feathers indicating a source of genetic material that does not require the capture or sacrifice of the birds. Other genetic markers and methods, including satellite telemetry, are required for obtaining detailed information on crane distributions as needed to establish effective management units for the MCP. 相似文献
7.
Interaction of sauger Sander canadensis and walleye Sander vitreus in a large,shallow northern river
The objectives of this study were to: (1) determine the relative abundance of sauger Sander canadensis and walleye S. vitreus within the Rainy River using a standardized index netting technique; (2) assess the life-history characteristics of the two species in a northern river; (3) examine the spatial distribution of the two species; (4) assess year-class synchrony. At a larger scale, relative abundance of S. canadensis and S. vitreus were similar among sections of the river. However, at a finer scale, S. canadensis were the dominant species over more area (24%) of the river than S. vitreus (12%). Life-history traits for both species were within the range reported for North American. Mortality rates were similar, suggesting that anglers were not affecting one species more than the other. Year-class strengths were not synchronous between S. canadensis and S. vitreus (r = 0.07). There was evidence of S. canadensis potentially outcompeting S. vitreus with a strong year class of S. canadensis followed by a very weak class of S. vitreus. Additionally, S. canadensis were larger than S. vitreus in most sections of the river when adjusted for mean size. However, the potential interspecific competition was not to the exclusion of S. vitreus. Turbidity was probably the factor that enable S. canadensis to survive sympatrically with S. vitreus given their inability to segregate by depth within the river. 相似文献
8.
Sanguinaria canadensis is a member of the Papaveraceae that normally has eight petals rather than four as is usual in the family. Using epi-illumination microscopy to study floral development, we show that the four additional petal primordia are initiated in positions that correspond to the first four stamen positions in species of the Papaveraceae with four petals. Also, these additional petal primordia share early developmental features with stamen primordia: at inception they are circular in outline, and the relationship between organ length and width while very young is similar. The developmental pathway of the additional petals combines both stamen and petal features: initially stamenlike in appearance, they develop into typical petals. The additional petals of S. canadensis can therefore be interpreted as homeotic because petal features are expressed in stamen positions. Organogenesis in the ‘Multiplex’ cultivar is similar to that of its wild progenitor, but during development all primordia in the androecial region become petals. This cultivar, as well as variants within natural populations, show that replacement of stamens with petals occurs within the species. 相似文献
9.
Patricio Picco Paul Hasuoka Ernesto Verni Marianela Savio 《International journal of phytoremediation》2019,21(7):693-698
AbstractThe capacity of Elodea canadensis to phytofiltrate arsenic species from water was evaluated. Plants were adapted to tap water and supplemented with 15 and 250?µg L?1 of As. Inorganic arsenic species (As III, As V), and organic arsenic compounds: monomethylarsonate (MMA) and dimethylarsinate (DMA) were analyzed. Sampling was carried out at different times after exposure in culture water and plant organs. Plants exposed to 15?µg L?1 of As concentration showed no significant difference on As concentration (95% confidence level) in their organs compared to controls. When plants were exposed to 250?µg L?1 of As concentration, a significant increase of As concentration in plant organs was observed. After 1?h exposure, plants reduce 63.16% the As concentration in the culture water, with a bioaccumulation factor (BF) of 4.3. Under these conditions, E. canadensis accumulate As V in roots and do not translocate it to stems (transfer factor <1). MMA was determined in stems and leaves. E. canadensis effectively phytofiltrate As from tap water of a city located in an arsenic endemic area from concentrations of 36?µg L?1 to undetectable levels (10?ng L?1). 相似文献
10.
Forty-two Helicobacter isolates were isolated from swine feces in The Netherlands and Denmark. All 12 isolates sequenced (16S rRNA gene) formed a robust clade with Helicobacter canadensis (~99% similarity). Species-specific PCR indicated that all of the isolates were H. canadensis isolates. Although the appearance of the porcine isolates was similar to the appearance of H. canadensis, only one of these isolates was able to hydrolyze indoxyl acetate, a cardinal characteristic of this taxon. Examination of the 23S rRNA and hsp60 genes revealed high levels of similarity between the porcine isolates and H. canadensis. However, amplified fragment length polymorphism genomic typing showed that isolates recovered from swine feces were genetically distinct from H. canadensis strains obtained from humans and geese. 相似文献
11.
Solidago canadensis L. is a major invasive weed that is highly tolerant to disturbances and difficult to control in China. In order to develop a rapid non-chemical control strategy for this weed in heterogeneous environments, we investigated different treatments including mechanical control (cutting and hoeing) and inoculation with an indigenous pathogen, Sclerotium rolfsii SC64, which was isolated from S. canadensis and applied by means of a solid formulation. Greenhouse and field trials were conducted to test how the control regimes (i.e. individual treatment methods, combination of these methods and different treatment timing) influence control efficiency. The fungal isolate S. rolfsii SC64 caused 70% plant mortality and fresh weight reduction of S. canadensis under 150 cm growth stage, and efficacy increased to 80% when the above-ground material was removed. However, the use of cutting, hoeing or treating with S. rolfsii SC64, on its own, did not provide sufficient control of S. canadensis. Cutting treatments performed in July and September only eliminated sexual reproduction of S. canadensis. Combination of cutting, hoeing and treating with isolate SC64 during the growing season in May, July and September was able to kill more than 90% of the ramets. This combination of methods not only eliminated sexual reproduction of S. canadensis, but also destroyed its underground stems and prevented its regrowth. Therefore, this integrated approach may provide an optima control strategy for S. canadensis. 相似文献
12.
Effects of mutual intercropping on cadmium accumulation by the accumulator plants Conyza canadensis,Cardamine hirsuta,and Cerastium glomeratum 总被引:1,自引:0,他引:1
Hui Xia Dong Liang Fabo Chen Ming'an Liao Yi Tang 《International journal of phytoremediation》2018,20(9):855-861
In this study, three cadmium (Cd) accumulator species (Conyza canadensis, Cardamine hirsuta, and Cerastium glomeratum) were co-cultured in Cd-contaminated soil in pots to study the effects of intercropping on co-remediation. Only C. canadensis intercropped with C. glomeratum, C. hirsuta intercropped with C. glomeratum, and three-species intercropping increased plant biomass compared with their respective monocultures. The treatments of C. canadensis intercropped with C. glomeratum and three-species intercropping increased the Cd contents in roots and shoots of C. canadensis, whereas the other intercropping treatments decreased or had no significant impact on Cd contents. As for Cd accumulation, the treatments of C. canadensis intercropped with C. glomeratum, C. hirsuta intercropped with C. glomeratum, and three-species intercropping increased Cd accumulation in a single plant compared with that of their respective monocultures, whereas other intercropping treatments decreased Cd accumulation in individual plants. Only the treatments of C. canadensis intercropped with C. glomeratum and C. hirsuta intercropped with C. glomeratum increased Cd accumulation in shoots of a single pot compared with that of their respective monocultures. Therefore, C. canadensis intercropped with C. glomeratum and C. hirsuta intercropped with C. glomeratum may improve the phytoremediation efficiency for Cd-contaminated soil. 相似文献
13.
Guang-Qian Ren Hong-Yu Yang Jian Li K. Prabakaran Zhi-Cong Dai Xiu-Pu Wang Kun Jiang Chris B Zou Dao-Lin Du 《Plant Species Biology》2020,35(4):283-299
Phenotypic plasticity is commonly considered to contribute to the invasion success of invasive species. However, the importance of phenotypic plasticity, nitrogen (N) levels and warming to the invasion of invasive species is unclear. The effects of warming and N addition on the morphology, biomass allocation and biochemistry traits of Solidago canadensis and their plasticity were investigated by conducting a pot experiment. The results showed that the effect of N addition on biomass was improved for S. canadensis; whereas warming displayed no significant effect, their positive synergistic interact effect resulted in the overall significant increase in plant performance. The mean phenotypic plasticity indices (MPPI) of biochemistry and total parameters demonstrated a difference between operations, and the higher value was observed in N interaction with temperature treatments than N addition or warming alone. The observed MPPI indicated the biochemistry parameters > morphological parameters > allocation parameters. The MPPI of biochemistry parameters, morphological parameters and total parameters exhibited significant and positive correlations with N level and MPPI of morphological parameters was also significantly positively correlated with the fitness of S. canadensis. These results indicated that the global warming and N addition would make the invaded habitat more suitable for the growth of invasive S. canadensis, and even may effectively increase the invasion risk of S. canadensis through the enhanced phenotypic plasticity, which is a crucial factor to help species deal with the changing environment. 相似文献
14.
Justin L. Hart Saskia L. van de Gevel John Sakulich Henri D. Grissino-Mayer 《Trees - Structure and Function》2010,24(4):621-633
It has long been hypothesized that trees growing at range limits likely also occur near the limit of their ecological amplitude
and thus, should be more sensitive to climate variability than individuals growing nearer the range core. We developed a tree-ring
chronology using Tsuga canadensis individuals from three disjunct stands at the species’ southern limit to quantify the influence of climate and disturbance
on radial growth patterns. The tree-ring record extended 158 years from 1850 to 2007. Significant negative relationships were
found between the STANDARD chronology and monthly mean temperature, monthly maximum temperature, and monthly minimum temperature
during the previous and current summer, while significant positive relationships were documented between the STANDARD chronology
and monthly minimum temperature for September and October of the current year. Also, significant positive relationships were
documented between the STANDARD chronology and monthly total precipitation for September of the previous year and May of the
current year. Response function analysis showed that monthly climate variables (r
2 = 0.22) and prior growth (r
2 = 0.40) explained 62% of the variance in the T. canadensis tree-ring chronology. A time series plot for the T. canadensis chronology showed that actual tree growth agreed relatively well with the predicted growth based on significant climate variables.
However, positive departures from the predicted growth were noted. Dendroecological analysis revealed these departures were
likely related to disturbance events. Our results indicated that T. canadensis individuals at its southernmost extent are sensitive to regional climate, but not more so than trees nearer the range core.
We hypothesize that microenvironmental conditions of T. canadensis stands at its southern limit are similar to conditions within the contiguous distribution of the species, which may explain
this pattern. 相似文献
15.
16.
SUMMARY Myogenesis of two representatives of Platyhelminthes, Stylostomum sanjuania and Pseudoceros canadensis, was followed from egg deposition until well‐differentiated free‐swimming larval stages, using F‐actin staining and confocal laserscanning microscopy. Zonulae adhaerentes are the only structures to stain before 50% of development between egg deposition and hatching in S. sanjuania, and before 67% of development in P. canadenis. Subsequently, irregular fibers appear in the embryo, followed by a helicoid muscle close to the apical pole. Three longitudinal muscle pairs form, of which the dorsal pair remains more pronounced than the others. Gradually, new muscles form by branching or from double‐stranded muscle zones adjacent to existing muscles. This results in an elaborate muscular bodywall that consists of a single helicoid muscle as well as multiple circular and longitudinal muscles. Diverse retractor muscles insert at the sphincter muscles around the stomodeum. The overall arrangement and formation mode of the larval musculature appears very similar in both species, although only P. canadensis has a primary circular muscle posterior to the helicoid muscle. Muscle formation in the apical region of the embryo precedes that at the abapical pole and the primary longitudinal muscles form slightly later than the primary circular muscles. Myogenesis and larval myoanatomy appears highly conserved among polyclad flatworms, but differs significantly from that of other trochozoan clades. Our data suggest that the larval muscular ground pattern of polyclad larvae comprises a bodywall consisting of a helicoid muscle, circular and longitudinal muscles, several retractor muscles, and sphincter muscles around the stomodeum. 相似文献
17.
Michal Polak 《Ethology : formerly Zeitschrift fur Tierpsychologie》1993,95(4):278-290
Male Polistes canadensis and P. carnifex aggregate along crests of prominent ridges in Santa Rosa National Park, Costa Rica. At these sites males of both species defend territories (trees and shrubs) by chasing conspecific rivals. Territories do not contain nests or resources that are collected by females. Chasing by territorial males reduces the amount of time spent by intruders in a territory. I describe and contrast male territorial behavior of both species. Some male P. canadensis are territorial while others in the same area exhibit patrolling behavior, flying from one occupied territory to another. Males of P. carnifex exhibit territoriality only. Patrolling in P. canadensis is an outcome of relatively high male density along the ridge, rendering territories in short supply, as shown by the observation that experimentally vacated territories are seized rapidly by formerly patrolling males. Due to a high intraspecific intrusion rate, territorial male P. canadensis spend less time perching and more time flying and chasing intruders from their territories than do male P. carnifex. Males of these two species also differ in the placement of their territories along the ridgeline; P. canadensis occupy territories in saddles while P. carnifex occupy those at peaktops. I show that this divergent spatial pattern is not maintained by competitive exclusion of either species by the other, and I discuss alternative explanations for their separate spatial distributions. Comparative data suggest that males are territorial because females restrict matings to within territories, and I discuss alternative hypotheses to explain this bias in female behavior. 相似文献
18.
O. P. Rajora B. P. Dancik 《TAG. Theoretical and applied genetics. Theoretische und angewandte Genetik》1995,90(3-4):331-334
A rare phenomenon of the occurrence of novel non-parental chloroplast DNA (cpDNA) variants in natural sexual interspecific hybrids between Populus deltoides var deltoides and P. nigra, P. x canadensis is described. Restriction fragment variation of cpDNA in 17 P. x canadensis cultivars was examined and compared with that of representative samples of P. deltoides and P. nigra using 83 combinations of 16 restriction enzymes and six Petunia hybrida cpDNA probes. Twelve cultivars had one to five novel non-parental cpDNA fragments in the chloroplast genome region homologous to the 9.0-kb PstI cpDNA fragment of Petunia from the large single-copy region. 相似文献
19.
N. J. Loman L. A. S. Snyder J. D. Linton R. Langdon A. J. Lawson G. M. Weinstock B. W. Wren M. J. Pallen 《Journal of bacteriology》2009,191(17):5566-5567
We determined the genome sequence of the type strain of Helicobacter canadensis, an emerging human pathogen with diverse animal reservoirs. Potential virulence determinants carried by the genome include systems for N-linked glycosylation and capsular export. A protein-based phylogenetic analysis places H. canadensis close to Wolinella succinogenes.Helicobacter canadensis is an emerging pathogen that has been isolated from four Canadian patients with diarrhea and an Australian patient with bacteremia (3, 10). Wild geese have been identified as a reservoir in Europe (12, 13), while in China, the organism has been isolated from the feces of wild rodents (5). H. canadensis has also been isolated from laboratory rabbits (11) and from Guinea fowl in France (8). Atypical isolates have been obtained from swine feces from The Netherlands and Denmark (6). To shed light on the virulence and colonization factors of H. canadensis and to reassess its phylogenetic status, we performed whole-genome sequencing of the type strain, H. canadensis strain MIT 98-5491/NCTC 13241.Single- and paired-end whole-genome shotgun sequencing was performed using 454 pyrosequencing technology, supplemented by Solexa sequencing. An initial assembly of the 454 single-end and paired-end data was created using a Newbler assembler (Roche), generating four scaffolds with an average size of 402 kb. The genome sequence was completed using a combination of BLASTX searches and analysis of the Solexa data, followed by confirmatory PCRs, PCR-assisted contig extension (1), and combinatorial PCR, with conventional and long-PCR protocols. Annotation was performed using GenDB (7).The genome of H. canadensis NCTC 13241 consists of a single circular chromosome 1,623,845 bp in length, with a G+C content of 34%. There are 1,535 protein-coding sequences (CDSs), 40 transfer RNAs, and three rRNA loci.Although phylogenetic analyses based on 16S rRNA gene sequences place H. canadensis in the genus Helicobacter (3), analysis of 23S rRNA sequences supports a clade containing H. canadensis and Wolinella succinogenes (2). Our own phylogenetic analysis using a concatenation of 482 conserved CDSs from the H. canadensis genome and related genomes provides strong support for a W. succinogenes/H. canadensis clade (data not shown), suggesting that the current taxonomy should be reevaluated.One hundred seventeen CDSs from H. canadensis have no detectable ortholog in eight other genome-sequenced epsilonproteobacteria. We found only one contiguous region of difference longer than 10 genes (ROD1; HCAN_0630-HCAN_0663). Most CDSs in ROD1 are of unknown function, although, curiously, the region carries three versions of asparagine synthetase and contains six homopolymeric tracts. A second region of difference (ROD2; HCAN_0479-HCAN_0496) shows homology to HHGI1, a pathogenicity island from Helicobacter hepaticus strain ATCC 51449 that contributes to virulence in H. hepaticus (4).The H. canadensis NCTC 13241 genome contains 29 potentially phase-variable genes with homopolymeric tracts, including several genes that, by homology, might be implicated in virulence, e.g., an immunoglobulin A protease (HCAN_0234) and two homologues of the vacuolating cytotoxin from Helicobacter pylori (HCAN_0457 and HCAN_714). The genome contains a capsular polysaccharide export locus similar to that in Campylobacter jejuni (9). Also, like C. jejuni, H. canadensis possesses genes encoding an N-linked glycosylation pathway, including two copies of PglB (HCAN_0729 and HCAN_0930). 相似文献
20.
Summary The eastern tiger swallowtail butterfly,Papilio glaucus, is the most polyphagous of all Papilionidae species. While diverse larval detoxication abilities are known for bothPapilio glaucus and the closely relatedP. canadensis, the factors affecting oviposition preferences in adult females are unknown. These congeneric species were studied to determine the extent of oviposition mistakes on toxic plants. We were also interested in comparing the geographic patterns of variation in oviposition preferences and the genetic basis of these differences. We conducted oviposition three-choice studies with the Canadian tiger swallowtail butterfly,Papilio canadensis, and the Eastern tiger swallowtail,Papilio glaucus, giving them the choice of (1) tuliptree,Liriodendron tulipifera, which is toxic to virtually all populations (P. canadensis) north of the Great Lakes Region of North America, (2) quaking aspen,Populus tremuloides, which is toxic to essentially all populations (P. glaucus) south of the Great Lakes, and (3) black cherry,Prunus serotina, which is an excellent foodplant for all members of thePapilio glaucus group, but which does not occur at latitudinal extremes of North America (in Alaska and most of Canada or the southern half of Florida). Handpaired interspecific hybrids were tested under the same experimental design to evaluate the possibility of sexlinked oviposition behavior. There was considerable variability in the choice of plants by individual butterflies, but a general trend suggesting that the females of each species had a lower preference for the plant toxic to their larvae. More than 6000 oviposition bouts were counted from 37 differentp. canadensis and 54p. glaucus females along a latitudinal transect of approximately 5000 km from Alaska south through the Great Lakes hybrid zone region to southern Florida. While not exceptionally high anywhere, the preference for aspen (Salicaceae) declined precipitously in central Michigan (45° N latitude) and remained very low (5–12%) in all locations southward to Florida, whereas we observed a reciprocal trend in preference for tuliptree (Magnoliaceae) which was greatest in Florida (87% of all eggs) and steadily declined northward across the Great Lakes region. Cherry was selected in these 3-choice tests at a relatively consistent and low frequency at all latitudes. Fixed allele differences in sex-linked (LDH and PGD) and autosomal (HK) electromorphs are known forP. glaucus andP. canadensis. Our electrophoretic data suggest that the preference of an individual female for aspen is not simply a characteristic of the northern species (P. canadensis) but can occur inP. glaucus females. The reciprocal situation is also evident in Northern Michigan and Wisconsin females (scored electrophoretically and morphologically asP. canadensis) which sometimes exhibit a clear preference for the toxic tuliptree. In fact, Alaskan populations ofP. canadensis chose tuliptree for about 52% of their eggs, even though none of their offspring has ever survived on this plant species in laboratory studies. We conclude that even with distinctive latitudinal trends, a considerable amount of local variation in relative oviposition preference exists among individuals of these polyphagous species. BothP. glaucus andP. canadensis will lay eggs on toxic plants. It appears that factors selecting against oviposition on toxic tuliptrees have been minimal (relative to other factors) in Alaska and somewhat stronger in the Great Lakes hybrid zone. It is in this zone of contact with tuliptree where selection against theP. canadensis populations ovipositing on tuliptree may be strong due to high larval mortality when such natural mistakes are made. We do not know whether behavioral preference changes evolutionarily preceded or followed the development of specific physiological detoxication abilities for tuliptree or quaking aspen. However, for bothP. canadensis andP. glaucus the occurrence of oviposition mistakes on toxic plants by adults extends geographically well beyond the larval detoxication abilities of their offspring. Hybrid female offspring of pairings with Michigancanadensis females andglaucus males show distinct preferences for tuliptree, suggesting that oviposition may be controlled by a factor (or factors) on the sex chromosome. Unfortunately we were unable to obtain reciprocal hybrids to evaluate the possibility of sex-linked aspen preference. 相似文献