Sibling Species Group Research Articles

CYTOTAXONOMIC STUDY OF OXYA SPECIES IN CHINA (ORTHOPTERA: ACRIDOIDEA)

Abstract The chromosomal conventional karyotype and C‐banding karyotype of eight species in the genus Oxya (Catantopidae) are analysed. The result shows that O. chinensis (Thunberg), O. shanghaiensis Willemse and O. adentata Willemse all have similar C‐banding distribution, but the model of chromosomal group, the chiasma localization data and the total heterochromatin content (THC) value are different. O. agavisa Tsai has its own c‐banding feature and is distinguished from other species in the genus. O. bicingula Ma et al. is similar to both the O. chinensis group and O. agavisu in chromosomal marks and morphological characters, indicating that these three species have some relations during the evolutionary process. O. hyla intricata (Stal) is a “sibling species group” as indicated by the variation of the morphological feature and there are also diversiforms in cytotaxonomic marks. It seems that this group has higher differentiational speed and the speciational evolution is more active in modern times. In this group, O. apicocingula sp. nov. and O. flave femura sp. nov. are more specialized than the other populations which have not many terminal C‐bands in genome. As a conclusion, we consider that the evolutionary rate of the species in Oxya genus is unbalanced. This status is due to the actions from both the hereditary basis and the environmental condition of the different species.

Morphometric discrimination among females of sibling species of Aconophorini (Homoptera: Membracidae)

Abstract. Keys to species of auchenorrhynchous Homoptera are often based on male features, leaving no means for identifying females other than association with males. As a possible solution to this problem, we examined the use of linear discriminant functions derived from morphometric data (ten linear measurements among homologous body landmarks) for distinguishing females in two groups of sibling species in the Neotropical treehopper tribe Aconophorini (Membracidae: Membracinae): (1) Calloconophora caliginosa (Walker) and C.pinguis (Fowler); and (2) Guayaquila minuta (Fowler), G.venezuelensis Dietrich, and Central and South American populations of G.pallescens (Stål). Samples of female specimens identified by association with males were used to derive the discriminant functions. Performance of these discriminant functions as evaluated by jackknifing the data was as follows: 98.11% of the specimens in the first group correctly identified using a combination of three measurements, and 94.94% of the specimens in the second group correctly identified using a combination of ten measurements.

THE GEOGRAPHIC PATTERN OF GENETIC DIFFERENTIATION BETWEEN HOST ASSOCIATED POPULATIONS OF RHAGOLETIS POMONELLA (DIPTERA: TEPHRITIDAE) IN THE EASTERN UNITED STATES AND CANADA.

True fruit flies in the Rhagoletis pomonella sibling species group are at the center of a long-standing debate concerning modes of speciation. The allopatric separation of populations is widely thought to be a prerequisite for speciation in sexually reproducing animals. However, speciation in the R. pomonella group appears to have occurred sympatrically as a consequence of these flies shifting and adapting to new host plants. The sympatric shift of R. pomonella from its native host hawthorn to introduced domestic apple, which occurred approximately 150 years ago, provides a test of whether host specialization is sufficient to allow populations to differentiate in the absence of geographic barriers to gene flow. We report the results of a geographic study of allozyme variation for hawthorn and apple infesting populations of R. pomonella across the eastern United States and Canada. Six loci consistently show significant allele frequency differences at paired apple and hawthorn sites. These six loci map to three different regions of the genome, and linkage disequilibrium exists between non-allelic genes within each of these regions. Allele frequencies for five of the six loci displaying host associated differences also co-vary significantly with latitude. Inter-host divergence is, therefore, superimposed on north-south clinal patterns of intra-host variation such that the magnitude of genetic divergence between hawthorn and apple flies is a function of latitude. The findings suggest that partially reproductively isolated "host races" can evolve in sympatry as a consequence of R. pomonella infesting new host plants. Host recognition and host associated developmental traits are discussed as important factors differentiating apple and hawthorn flies.

A Sibling Species Group of Hydractinia in the North-Eastern United States

Many symbiotic organisms are narrowly distributed on one or a few host species. These associations are intriguing, as they invite the development of hypotheses regarding the pattern and process of speciation and serve as laboratories for the testing of methods of phylogenetic reconstruction (Kraus, 1978; Futuyma & Slatkin, 1983; Stone & Hawks worth, 1986). The evolution of host-specificity in the sea may be expected to be severely constrained by the difficulty of achieving reproductive isolation in taxa whose gametes are freely released into the water column and/or whose larvae are potentially widely distributed (Scheltema, 1977). Yet this difficulty may well be overestimated, given the recent demonstrations of limited gamete (Pennington, 1985; Yund, in press) and larval dispersal (Knight-Jones & Moyse, 1961; Ryland, 1981; Olsen, 1985; Jackson & Coates, 1986; Grosberg, 1987). Indeed, if gamete and larval dispersal are as limited as has recently been contended (Jackson, 1986), local isolation of populations may be a routine occurence, offering repeated opportunities for speciation.

Chromosomes of two species of Tisbe (Copepoda, Harpacticoida) belonging to different groups of sibling species

Karyological investigations curried out on Tisbe marmorata and T. dobzhanskii confirmed the diploid value 2n= 24 for the former species; on the basis of more than 200 observations it was ascertained that the diploid number of the latter species corresponds to 22, in contrast with a previous report. The karyotypes of these two species differ both in morphology and in location of satellites, not only from each other, but also from all other species so far examined. A close comparison of the two species with their respective siblings is made.

Heritable divergence of Rhagoletis pomonella host races by seasonal asynchrony

Possible mechanisms for animal speciation in the absence of geographic isolation remain controversial. Univoltine flies of the Rhagoletis pomonella sibling species group of larval fruit parasites have been cited1–5 as prime examples of sympatric speciation through divergence in host plant association. The recent emergence of several populations of R. pomonella associated with plants other than the fly's native hawthorn host has been attributed to the effects described by a model2–4 of sympatric host-race formation involving host recognition and survival genes; however, direct genetic evidence of biologically meaningful differentiation among putative host races has been lacking. In contrast, the potential importance of seasonal asynchrony (of flies adapted to host plants with different fruiting phenologies) in initial restriction of gene flow has been largely undervalued. Here I report heritable divergence in seasonal emergence of R. pomonella flies collected from sympatric populations on three host plant species in Illinois, in the United States.

Drumming as a Behavioral Line of Evidence for Delineating Species in the Genera Isoperla, Pteronarcys, and Taeniopteryx (Plecoptera)

The drumming behavior of nine Isoperla species, Pteronarcys pictetii Hagen, and two Taeniopteryx species are described for the first time. A derived form of drumming in Isoperla ouachita Stark and Stewart, consisting of male calls produced by abdominal rubbing, is reported for the first time in the Perlodidae. Use of drumming behavior as a line of evidence to delineate cryptic and sibling species groups within the genera Taeniopteryx, Pteronarcys, and Isoperla is examined. Male calling of Isoperla species varies from ancestral tapping to rubbing, and there is no overlap in important signal variables between sympatric species. There is no overlap of important drumming variables in the signals of known North American Taeniopteryx and Pteronarcys species, whose signals of both male and female are of a simple, ancestral type, with none of the derived states, such as diphasy or rubbing. Drumming in all known species of the three genera is species-specific, and largely corroborates morphologically based species separations.

Molecular structure of a somatically unstable transposable element in Drosophila.

A transposable element has been isolated from an unstable white mutation in Drosophila mauritiana, a sibling species of Drosophila melanogaster. The unstable white-peach (wpch) allele exhibits a spectrum of germ-line and somatic mutability more similar to insertion mutations in maize and in the nematode Caenorhabditis elegans than has been reported for insertion mutations in Drosophila. The inserted element mariner is 1286 nucleotides long and has terminal inverted repeats. The element contains a single open reading frame encoding 346 amino acids. A duplication of 2 base pairs of white sequence is present at the insertion site. Mariner is present in approximately 20 copies in the D. mauritiana genome, is present from 0 to 7 copies in other members of the sibling species group, and is apparently absent from the genome of D. melanogaster.

Untersuchungen zur Taxonomie der Gattung Araniella (Araneae, Araneidae)

Morphological and ethological criteria were used in studying the taxonomic relations between different forms within the genus Araniella. Criteria for a diagnosis of all species and subspecies of the genus are given. A. opisthographa (Kulczyǹski, 1905), A. cucurbitina (Clerck, 1757), A. proxima (Kulczyǹski, 1885) and A. maderiana (Kulczyǹski, 1905) form one group of sibling species in the narrowest sense, A. alpica (L. Koch, 1869) and A. inconspicua (Simon, 1874) a second distinct one. A. displicata (Hentz, 1847) seems to occupy a relatively isolated position. A. cossoni (Simon, 1885) is regarded as a synonym for A. cucurbitina. It is impossible to make a statement about the status of A. silesiaca (Fickert, 1876) and A. croatica (Kulczyǹski, 1905) because of the lack of sufficient material. A. silesiaca is not a synonym for Araneus crispulus Tullgren, 1952, a species which does not belong to the genus Araniella.

沖繩産シナハマダラカ群の卵型調査

沖繩産のA. lesteri卵型について観察所見をのべ, それに関連した今日までの若干の知見を紹介した。また旧北区系のいわゆるsinensis groupが再検討されねばならない時期にきていることを指摘した。

Scanning electron microscope study of the modified spine characteristic for males of some Tisbe (Copepoda: Harpacticoida) species

The scanning electron microscope proved to be an ideal instrument for examining the species-specific spine (on the endopodite basal segment of male P2) in the group of sibling species Tisbe holothuriae, T. pontina and T. battagliai. Three other species: T. gracilis, T. cucumariae and T. biminiensis belonging to the gracilis group are included in the present study. A possible functional significance of the spine is discussed.

Studies of Asilidae (Diptera) systematics and evolution: III. Tribe Blepharepiini (Dasypogoninae)

Examination of types and comparative studies of the male genitalia permitted a reclassification of Blepharepium Rondani, 1848, the only recent representative of the tribe Blepharepiini. This tribe can be distinguished from all other tribes of Dasypogoninae by the presence of a complete prosternum. Blepharepium has the following recognized species: 1. annulatum (Bigot, 1857 (= secabile Walker, 1860; southern Mexico, Central America, northwestern South America, West Indies; forest areas); 2. cajennensis (Fabricius, 1787), with 3 subspecies: i. cajennensis s. s. (= inserens Walker, 1851; = auricincta Schiner, 1867; = inca Curran, 1942; Guianas, coastal Venezuela, western Brazilian Amazonia, Peru, northern Bolivia); ii. coarctatum (Perty, 1833; = bonariensis Macquart, 1838; = occidens Walker, 1851; = lynchi Carrera, 1949; open formations of Guiano-Brazilian subregion) ; iii. cunctabundum, n. ssp., forest areas of the States of Sao Paulo south to Rio Grande do Sul, Brazil; 3. fuscipennis (Macquart, 1834 ; = insertus Walker, 1851; - maculipennis Macquart, 1855; western Amazonia, Brazilian Atlantic forest); 4. luridum Rondani, 1848 (- modesta Bigot, 1878; Amazonia); 5. subcontractum (Walker, 1856; = bassleri Curran, 1942; western Amazonia); 6. priapus, sp. n., from Arizona, Phoenix; 7. sonorensis, sp. n. (annulatum group of sibling species; Sonoran Desert, s. Utah to n. Mexico); 8. surumu, sp. n. (annulatum group of sibling species; southern Venezuela, northeastern Roraima Territory in Brazil). Senobasis borealis James, from the the Oligocene shales of Florissant, Colorado, may also belong to Blepharepium. Considerations on the biology, ecology, and evolution of the group are given.

Allozymes as Diagnostic Characters of Sibling Species of Drosophila

Considerable enzyme variation that is genetically controlled exists within and between natural populations of Drosophila. Our studies of two groups of sibling species show that allozyme differences can be used as species-diagnostic characters. A locus is defined as diagnostic if an individual can be correctly assigned to one of two species with a probability of 99% or higher. Between 15 and 32% of the loci studied are diagnostic for any two of the sibling species. If several diagnostic loci are used, the species of any individual can be diagnosed with virtual certainty.

Hybridisation Experiments on Five Species of African Schistosomes

The African schistosomes fall naturally into two main groups of sibling species, the S. haematobium complex and the S. mansonil S. rodhaini group. Morphological differentiation of the species within each group depends on small differences in the eggs but in many cases there are clear biological differences in definitive and intermediate host specificity and in parasitic site within the host, and these criteria serve to strengthen a classification based on egg morphology. Nevertheless, many authors have disputed the validity

Theory of fitness in a heterogeneous environment: Part III. The response to selection

A method is presented for estimating the average fitness of a population which is responding to selection in a fluctuating environment. The environment is assumed to be a stationary Markov random process of the type described by Uhlenbeck & Ornstein (1930), and the genotype is restricted to a single locus with two alleles. The fitness of each genotype depends on the deviation of its phenotype from the optimal phenotype in the given environment. Finally the fitness of the population is expressed as a function of the parameters of the genetic system (average phenotypic effect of a gene substitution, mutation rate) and of the environment (mean, variance, and autocorrelation). Conditions were found under which it is advantageous for a population to be polymorphic (that is, under which the average phenotypic effect of a gene substitution should differ from zero for maximum fitness). These conditions are of two very different kinds. First, regardless of whether the environment is autocorrelated or not, phenotypic diversity is advantageous if the environment is sufficiently heterogeneous compared to the tolerance of an individual for non-optimal conditions. When W( Cz) is the fitness of a genotype whose phenotype differs from the optimum phenotype by z, the tolerance is defined as the distance from the peak (at z = 0) to the point of inflection of W( Cz). Since W( z) has its inflection at some z 0, the tolerance of each genotype is z 0 C , and C is an inverse measure of homeostasis. If the environment consists of discrete niches or is bimodal with modes (or optimal phenotypes in the niches) further apart than z 0 C , it is sufficiently heterogeneous for polymorphism to be optimal. This kind of polymorphism is stable. The different genotypes should be retained in the same frequencies without responding to selection, so that the optimal genetic system will be one in which there is large genetic variance due to epistatic interactions but a minimal additive component. The second kind of optimal polymorphism occurs when there is a high autocorrelation in the environment. Here the advantage of genetic variance is only that it permits response to selection. Thus it will consist mostly of additive variance. These two kinds of optimal polymorphism have very different consequences for speciation. In the first case, recombination between populations will result in F 2 breakdown, so that natural selection will tend toward the establishment of isolating mechanisms. Therefore we expect that groups in which there is low individual tolerance of suboptimal environment will have high levels of static polymorphism based on epistatic complexes, a high degree of F 2 breakdown, and a high rate of speciation. In the second case, where additive variance predominates, F 2 between populations is more or less intermediate and there is not any strong selection for isolation. Hence a high individual tolerance of non-optimal environments will be accompanied by genetic systems with more additive variance, fewer inversions holding epistatic blocks, low F 2 breakdown, and a low rate of speciation. It is suggested that the willistoni group of sibling species and Drosphila melanogaster are representatives of these alternative systems of adaptation.

Current concepts of evolutionary mechanisms in mosquitoes.

The processes by which a panmictic population is broken up into smaller, differentiated groups is one of the central problems involved in the study of the evolutionary mechanism. In mosquitoes, it appears evident that a considerable amount of physiological, but relatively little morphological differentiation has taken place, so that several groups of sibling species exist. The morphological and taxonomic picture of “species” at the present time is therefore highly inaccurate. It is true that morphological variability is restricted, but the physiological differences, plus the reproductive barriers between populations clearly indicate the specific status of many populations.

TheAnopheles hyrcanusGroup in South-East Asia (Diptera: Culicidae)

The<i>Anopheles hyrcanus</i>Group in South-East Asia (Diptera: Culicidae)

The willistoni group of sibling species of Drosophila.

Journal Article THE WILLISTONI GROUP OF SIBLING SPECIES OF DROSOPHILA Get access H. Burla, H. Burla University of São Paulo BrazilColumbia University New York Search for other works by this author on: Oxford Academic Google Scholar A. Brito da Cunha, A. Brito da Cunha University of São Paulo BrazilColumbia University New York Search for other works by this author on: Oxford Academic Google Scholar A. R. Cordeiro, A. R. Cordeiro University of São Paulo BrazilColumbia University New York Search for other works by this author on: Oxford Academic Google Scholar Th. Dobzhansky, Th. Dobzhansky University of São Paulo BrazilColumbia University New York Search for other works by this author on: Oxford Academic Google Scholar C. Malogolowkin, C. Malogolowkin University of São Paulo BrazilColumbia University New York Search for other works by this author on: Oxford Academic Google Scholar C. Pavan C. Pavan University of São Paulo BrazilColumbia University New York Search for other works by this author on: Oxford Academic Google Scholar Evolution, Volume 3, Issue 4, 1 December 1949, Pages 300–314, https://doi.org/10.1111/j.1558-5646.1949.tb00031.x Published: 01 December 1949 Article history Received: 11 April 1949 Published: 01 December 1949