ALLOZYME DIVERGENCE AMONG FIVE DIPLOID SPECIES OF ANTENNARIA (ASTERACEAE: INULEAE) AND THEIR ALLOPOLYPLOID DERIVATIVES

The Antennaria parlinii and A. neodioica agamic complexes are widely distributed across North America. Morphological data have suggested that these dioecious, perennial, entire-leaved herbs are of multiple hybrid origin from among five sexual diploid species. Antennaria neglecta, A. plantaginifolia, A. racemosa, and A. virginica are hypothesized to be the diploid progenitors of the A. neodioica complex, whereas A. parlinii sensu lato is thought to include the genomes of A. plantaginifolia, A. racemosa, and A. solitaria. An electrophoretic study was initiated to assess the degree of divergence among the five diploid species and to test the hypotheses of the hybrid (allopolyploid) origins of A. parlinii and A. neodioica. Twenty genetic loci were surveyed in 76 populations of the diploid and polyploid taxa. The diploid species are well defined morphologically, although the genetic basis of differences distinguishing them have not been determined. The species exhibit little divergence at genes specifying soluble enzymes, however each species has unique alleles in highest frequency at one or two genes. Allozymes indicate that gene diversity in the obligately outcrossing diploids occurs primarily within rather than among populations. The shale barren endemic, A. virginica, is as genetically diverse as the more edaphically diverse and widespread species. Tetraploid cytotypes of diploid (2n = 28) A. virginica possess the same allozymes as the diploids and these cytotypes appear to be of autopolyploid (non-hybrid) origin. Enzyme electrophoresis is concordant with morphological data in suggesting that A. neodioica contains the genomes of A. neglecta, A. virginica, A. plantaginifolia, A. racemosa and perhaps A. solitaria whereas the latter three species are the progenitors of A. parlinii.     

ALLOZYME VARIATION WITHIN AND BETWEEN LASTHENIA MINOR AND ITS DERIVATIVE SPECIES,L. MARITIMA (ASTERACEAE)

Enzyme electrophoresis was employed to examine genetic variation at 20 loci in 16 populations of Lasthenia minor and 18 populations of its presumed derivative species L. maritima. The purposes of the study were to ascertain levels of genetic variation in each species, to assess how the variation at enzyme-coding genes is apportioned within and among populations of each species, and to determine the level of divergence between the two species. The two species are both diploid annuals, similar morphologically, and produce fertile F₁ hybrids when crossed. Lasthenia minor is self-incompatible and restricted to mainland California, whereas L. maritima is self-compatible and probably largely autogamous; it occurs on seabird rocks from central California to British Columbia. Mean genetic identities for pair-wise comparisons of populations of the two species are similar to values for populations of the same species, indicating they have not diverged at the 20 genes coding for soluble enzymes. Despite its more extensive geographical range, L. maritima exhibits only 50% of the genetic diversity of L. minor. The latter species apportions a greater amount of its diversity within populations, whereas the former harbors more diversity among populations than within them. This is probably a reflection of the different breeding systems of the two species. Six unique alleles were detected in L. minor, whereas only one novel allele was found in a single individual of L. maritima. The electrophoretic data are concordant with the suggestion that L. maritima is relatively recently derived from L. minor. The switch from outcrossing to selfing and selection of genotypes adapted to the chemically and physically unusual substrate on the seabird rocks are considered the critical steps in the evolution of L. maritima.     

PATTERNS OF ISOZYME VARIATION IN WESTERN NORTH AMERICAN ANTENNARIA (ASTERACEAE: INULEAE) II. DIPLOID AND POLYPLOID SPECIES OF SECTION ALPINAE

Antennaria is a genus of dioecious, perennial, herbaceous Composites that are especially diverse in the cordillera of western North America. Section Alpinae consists of about nine taxa, among them A. aromatica, A. densifolia, A. media, A. pulchella, and A. umbrinella. Although diploids are morphologically distinct, the polyploid derivatives of the diploids obscure the morphological distinctness of the groups. A survey of 19 putative isozyme loci indicates that the diploids have diverged only moderately from one another with respect to biochemical genetics (I = 0.838 to 0.961). Additionally, only moderate amounts of genetic diversity were detected. Isozyme data are supportive of a hypothesis of a rapid mode of speciation in Antennaria, where morphological differentiation has been accompanied by small amounts of allozyme divergence. Polyploids have significantly higher amounts of heterozygosity than diploids and tetrasomic inheritance is inferred. Evidence from morphology and biochemical genetics suggests that the polyploids represent a continuum between interracial autopolyploids and segmental allopolyploids. In light of the relatively low degree of genetic and morphological divergence among many Antennaria species, taxonomic conservatism is advocated.     

ALLOZYME DIVERSITY WITHIN AND DIVERGENCE AMONG FOUR SPECIES OF ROBINSONIA (ASTERACEAE: SENECIONEAE), A GENUS ENDEMIC TO THE JUAN FERNANDEZ ISLANDS,CHILE

Enzyme electrophoresis was employed to assess genetic diversity within and divergence among four species of Robinsonia (R. evenia, R. gayana, R. gracilis, R. thurifera), a genus endemic to the Juan Fernandez Islands, Chile. The genus consists of treelike perennial plants, and all species are dioecious. Morphological diversity within the genus is reflected by recognition of two subgenera, with three sections in one subgenus. Total gene diversity is highest in the two species (R. gayana and R. gracilis) that are most common and have the largest population sizes. Robinsonia evenia has only half and the rare R. thurifera only 20% of the diversity detected in the other two species. The diversity measured in R. gayana and R. gracilis is comparable to the values typical of continental species of flowering plants with similar life history attributes. The genetic identities between species range from 0.560 to 0.706, which is similar to or below many values for congeneric species, but much lower than most reports for congeners on oceanic islands. The higher diversity within and divergence among species of Robinsonia compared to many insular endemics may result from several factors. The genus probably arose from selfincompatible plants of the genus Senecio, which means that several to perhaps many colonizers carried considerable allozymic variation to the Islands. Large population sizes and obligate outcrossing are additional factors that would account for higher diversity. Sorting of alleles during radiation and the process of mutation probably combined to produce divergence among the species. Estimated divergence times calculated for the species from allozyme data range from 1.7 to 5.5 million years depending on the assumptions made in the calculations; the age of the island (Masatierra) on which these four species are confined is approximately 4.0 million years. The electrophoretic data suggest that Robinsonia arrived early in the archipelago, and radiated and speciated rapidly after colonization.     

ALLOZYME VARIATION WITHIN AND AMONG MATURE POPULATIONS OF SPECKLED ALDER (ALNUS RUGOSA) AND RELATIONSHIPS WITH GREEN ALDER (A. CRISPA)

Vegetative tissues from 14 sexually mature populations of speckled alder (Alnus rugosa (Du Roi) Sprengel) in Québec have been analyzed for electrophoretically demonstrable variation in 9 enzymes encoding a total of 15 loci. Speckled alder demonstrated a diploid-like expression for all polymorphic loci investigated. Populations were in Hardy-Weinberg equilibrium for the 9 polymorphic loci observed. The total expected heterozygosity was 0.173. Analysis of fixation indices indicated a slight deficiency of heterozygotes, relative to panmictic expectations. This was likely due to weak population differentiation, which did not follow any particular geographical trend. Qualitative estimates of interpopulation rates of gene flow were high, and in good agreement with the small pair-wise population genetic distances and among-population fixation index. Levels of genetic diversity and partition of this diversity were similar to previous observations obtained with the sympatric species A. crispa (Ait.) Pursh. However, no phenomena of interspecific hybridization were noted. The average genetic distance between these two alder species was large, with a value of 0.4, emphasizing the different ecological niches colonized by each of the two species. The estimate of divergence time between these two taxa was two million years. It is in agreement with the hypothesis of repetitive spatial isolation of each species in ice-free refugia during the Pleistocene, thus promoting their reproductive isolation. The interspecific divergence noted at the enzyme level allowed for the easy electrophoretic identification of each taxon.     

KARYOTYPES OF FIVE PLANT SPECIES WITH DISJUNCT DISTRIBUTIONS IN VIRGINIA AND THE CAROLINAS

Five species (Actaea pachypoda, Aralia nudicaulis, Cornus alternifolia, Panax quinquefolius, and Symplocarpus foetidus) display a disjunct distribution between the Mountains and Piedmont in North Carolina, South Carolina, and Virginia. The Piedmont populations are small and have apparently been isolated from the Mountain populations for several thousand years. Karyotype differences among populations were found only in A. pachypoda, and even in this species the differences were slight. The absence of population differences in four species, and the moderate differentiation found in A. pachypoda, indicate considerable cytological stability in these species.     

PRESENCE AND DISTRIBUTION OF BROMINE IN THYSANOCLADIA DENSA (SOLIERIACEAE,GIGARTINALES), A MARINE RED ALGA FROM THE GREAT BARRIER REEF1

Electron-probe X-ray microanalysis of freeze dried sections of growing branch tips of Thysanocladia densa Sander shows high concentrations of bromine in the region of the medulla. Indirect evidence infers that the Br is associated with intercellular, granular deposits which accumulate within the mucilage of the medulla. The concentration of Br decreases in older regions of the thalli.     

THE VEGETATIVE ANATOMY OF JAUMEA CARNOSA (LESS.) GRAY (ASTERACEAE), A SALT MARSH SPECIES

Certain anatomical characters of Jaumea carnosa, a salt marsh plant, which are diagnostic, adaptive, or otherwise important for an ecological anatomy study are described. The characters which follow are noteworthy. The plant has a sympodial construction forming an extensively branched rhizome system, and erect lateral shoots which eventually become prostrate. The leaves have very few, and only moderately developed succulent characters, such as: poorly defined palisade tissue, central mesophyll cells which are slightly enlarged anticlinally, and a complete lack of sclerification in the mesophyll. A continuous schizogenous canal system lined with epithelial cells lies in the ground tissues of all stem forms and leaves. The phellem is composed of thin-walled, only lightly suberized cells. Very broad parenchymatous areas develop in the secondary tissues of the rhizome, associated with a slowing of vascular cambial activity which creates depressions in the axis. Adventitious roots arise from ground tissues close to the primary xylem and from interfasicular regions close to the primary phloem in the rhizomes.     

ALLOZYME VARIATION IN SOME POPULATIONS OF THE FRESHWATER SNAILS LYMNAEA PEREGRA, L. AURICULARIA AND L. STAGNALIS (GASTROPODA: PULMONATA)

Three species of the genus Lymnaea (Gastropoda, Pulmonata, Basommatophora)were examined for genetic variation at 11 enzymatic loci insamples collected in Brittany (North-Western France). Variabilitywas greatest in L. percgra, but the limited area of samplingdid not allow specific inferences. The UPGMA clustering of unbiasedgenetic distances (Nei, 1978) isolated first L. auriculariasamples, and secondly the single L. stagnalis sample from theL. peregra set. This scheme of relationships was opposed tothe identification of alleles shared by the three species atthe studied loci Analysis of L. peregra population structure by F-statistics(Weir & Cockerham, 1984) suggested high inbreeding and raisedthe possible role of self-fertilization. The contradiction betweenhigh variability and high homozygosity is discussed. Furthermore,population differentiation was rather weak (although statisticallysignificant), despite some remarkable differences among loci.Nm estimates using Wright's (1951) and Slatkin's (1985) methodsrevealed a gene flow unable to prevent the effect of geneticdrift among populations. The relative homogeneity of populationswith weak genetic exchange is discussed (Received 24 May 1993; accepted 21 March 1994)     

中国长冠叶蝉属分类研究并一新种记述(同翅目,叶蝉科,大叶蝉亚科)

对中国长冠叶蝉属Stenatkina的种类进行了系统整理,提出脊大叶蝉属Atkinoida Cai是长冠叶蝉属Stenatkina的新异名,编制了分种检索表,简记了已知种的分布,描述了采自云南盈江的1新种,即白翅长冠叶蝉S.albopennis Yang,sp.nov.,绘制了新种雄性外生殖器构造图,提供了长冠叶蝉属中国所有种类的背观彩色整体照片.研究标本及新种模式标本保存在贵州大学昆虫研究所.     

中国拟峰斑螟属一新种及棕黄拟蜂斑螟变异讨论(鳞翅目,螟蛾科,斑螟亚科)

记述采自西藏拟峰斑螟属Anabasis Heinrich 1新种,模式标本保存在南开大学生命科学学院昆虫标本室.该文同时讨论了棕黄拟峰斑螟A.fusciflavida的变异,提供了该种在中国的分布图.     

柴达木盆地第四纪介形类Cyprididae科的新种和新组合

本文记述了柴达木盆地陆相第四纪介形类Cyprididae科的五个新种和两个新组合,它们分别是:Amplocypris qaidamensis sp.nov.,Eucyprinotus foveatus(Popova),E.qinghaiensis sp.nov.,Heterocypris subtriangularis sp.nov.,Psychrodromus gansenensis(Huang),P.mangnaiensis sp.nov.和Trajancypris nanlingqiuensis sp.nov.。其中,Amplocypris,Eucyprinotus和Psychrodromus在柴达木盆地第四系的产出,尚属首次报道。     

EFFECT OF LIGHT AND WATER-STRESS ON PHOTOSYNTHESIS AND BIOMASS PRODUCTION IN BOLTONIA DECURRENS (ASTERACEAE), A THREATENED SPECIES

Boltonia decurrens (Torrey & Gray) Wood, a perennial species endemic to the Illinois River Valley, is threatened with extinction. Construction of a system of dikes along the Illinois River has altered flood patterns during the last 100 years, converting wet prairies and natural marshes to cropland. Remaining shore habitats have been modified by heavy siltation and altered flooding regimes. Boltonia decurrens is now confined to areas that are disturbed by occasional cropping, disappearing from sites after 3 to 5 years of natural succession. This study was conducted to determine the role of light and water availability upon growth and reproduction. Our data indicate that under greenhouse conditions B. decurrens requires high levels of light for optimal photosynthesis and growth, and is more sensitive to reductions in growth light level than to moderate drought-stress. This sensitivity to light regime may help explain its disappearance from disturbed areas after several years of natural succession. If B. decurrens is overtopped by fast-growing species, it could be shaded to the extent that growth and seed production would be severely affected, increasing the likelihood of its extinction.     

ALLOZYME VARIATION AMONG POPULATIONS OF BIOMPHALARIA PFEIFFERI (KRAUSS, 1848) (GASTROPODA: PLANORBIDAE) IN CAMEROON

Allozyme electrophoresis was used to study genetic diversityamong the freshwater, hermaphroditic snail Biomphalaria pfeifferiin Cameroon. Four of 19 loci studied were polymorphic. The allozymesfor two loci, aspartate aminotransferase-1 (AAT-1) and isocitratedehydrogenase (IDH), showed distribution patterns related toclimatic zones. AAT-1¹⁰⁰ and IDH¹⁰⁰ occurred predominantly inthe Tropical Climatic Zone, located in the northern half ofthe country. AAT-1¹⁴⁰ and IDH⁹⁰ were common in the EquatorialZone. Intrapopulation variations occurred in 5 of 19 populationsampled. Only one population, polymorphic for AAT-1 locus, waspanmictic. The other 4 populations were not in Hardy-Weinbergequilibrium. The deficiency of heterozygotes in those populationsis unusual for a member of the genus Biomphalaria and may bedue to a predominance of self-fertilization. Other explanationsinclude ecological factors or the presence of segregated sub-populationsthat do not outcross. This latter hypothesis is supported bythe total absence of heterozygotes for PGM alleles. (Received 24 August 1989; accepted 14 September 1989)