Models Of Sympatric Speciation Research Articles

A FIELD TEST FOR HOST-PLANT DEPENDENT SELECTION ON LARVAE OF THE APPLE MAGGOT FLY, RHAGOLETIS POMONELLA.

Host-plant dependent fitness trade-offs refer to traits that enhance the performance of an insect on one plant species to its detriment on others. Such trade-offs are central to models of sympatric speciation via host shifts, but have proven difficult to empirically demonstrate. Here, we test for host-plant dependent selection on larvae of apple (Malus pumila L.)- and hawthorn (Crataegus mollis L. spp.)-infesting races of Rhagoletis pomonella (Walsh). Samples of larvae were reared in the field and under protective conditions in a garage. Our rationale was that the garage should slow rates of fruit rot relative to the field, relaxing selection pressures associated with declining fruit quality. Four findings emerged from the study. (1) Larvae suffered higher mortality in fruits in the field than the garage. (2) The increase in mortality was greater for larvae in haws. (3) Larvae possessing the alleles Me 100, Acon-2 95, and Mpi 37, three allozymes displaying host-related differentiation in R. pomonella that map to linkage group II in the fly, left fruits earlier than other genotypes. (4) Allele frequencies for Me 100, Acon-2 95, and Mpi 37 were significantly higher in both apple and haw larvae surviving the field versus the garage treatment. Our results suggested that field conditions favored larvae that rapidly developed and left rotting fruits. Since these individuals tended to possess the alleles Me 100, Acon-2 95, and Mpi 37, frequencies of these allozymes were higher in the field. Selection on larvae was directional for Me 100, Acon-2 95, and Mpi 37 (or linked genes) in both host races. We previously showed that these same alleles can be disfavored in the pupal stage, especially in the apple race, where they correlate with premature diapause termination. Fitness trade-offs in Rhagoletis may therefore be due as much to differences in the relative strengths of directional selection pressures acting on different life stages as to disruptive selection affecting any one particular stage. The necessity to consider details of the entire life-cycle highlights one of the many challenges posed to documenting fitness trade-offs for phytophagous insects.

Molecular Evolution and Adaptive Radiation.

Preface List of Contributors Part I. Introduction: 1. Adaptive radiation and molecular evolution: concepts and research issues Thomas J. Givnish 2. Homoplasy in molecular vs. morphological data: the likelihood of correct phylogenetic inference Thomas J. Givnish, and Kenneth J. Sytsma Part II. Integrative Studies: 3. Adaptive radiation of the Hawaiian silversword alliance: congruence and conflict of phylogenetic evidence from molecular and non-molecular investigations Bruce G. Baldwin 4. The chronicle of marsupial evolution Mark S. Springer, John A. W. Kirsch, and Judd A. Chase 5. Evolutionary origins of phenotypic diversity in Daphnia John K. Colbourne, Paul D. N. Hebert, and Derek J. Taylor 6. Evolutionary trends in the ecology of New World monkeys inferred from a combined phylogenetic analysis of nuclear, mitochondrial, and morphological data Ines Horovitz, and Axel Meye 7. Adaptive radiation in the aquatic plant family Pontederiaceae: insights from phylogenetic analysis Spencer C. H. Barrett, and Sean W. Graham 8. Molecular evolution and adaptive radiation in Brocchinia (Bromeliaceae: Pitcairnioideae) atop tepuis of the Guayana Shield Thomas J. Givnish, Kenneth J. Sytsma, James F. Smith, William J. Hahn, David H. Benzing, and Elizabeth M. Burkhardt Part III. Convergence: 9. You aren't always what you eat: evolution of nectar-feeding among Old World fruitbats (Megachiroptera: Pteropodidae) John A. W. Kirsch, and Francois-Joseph Lapointe 10. Chloroplast DNA restriction sites and floral versus non-floral characters in the obligate twig epiphytes in subtribe Oncidiinae (Orchidaceae) Mark W. Chase, and Jeffrey D. Palmer 11. Adaptation, cladogenesis, and the evolution of habitat association in North American tiger beetles: a phylogenetic perspective Alfried P. Vogler Part IV. Rapid Radiations: 12. Molecular phylogenetic tests of sympatric speciation models in Lake Malawi cichlid fishes Peter N. Reinthal, and Axel Mey 13. A rapid adaptive radiation due to a key innovation in Aquilegia Scott Hodges 14. Origin and evolution of Argyranthemum (Asteraceae: Anthemideae) in Macaronesia Javier Francisco-Ortega, Daniel J. Crawford, Arnoldo Santos-Guerra, and Robert K. Jansen Part V. Reproductive Strategies: 15. Floral diversification, pollination biology, and molecular evolution in Platanthera (Orchidaceae) Jeffrey R. Hapeman, and Kenneth Inoue 16. Phylogenetic perspectives on the evolution of dioecy: adaptive radiation in the endemic Hawaiian genera Schiedea and Alsinodendron (Caryophyllaceae: Alsinoideae) Ann K. Sakai, Stephen G. Weller, Warren L. Wagner, and Pamela S. Soltis 17. Ecological and reproductive shifts in the diversification of the endemic Hawaiian Drosophila Michael P. Kambysellis, and Elysse M. Craddock Part VI. Character Divergence and Community Assembly: 18. History of ecological selection in sticklebacks - uniting experimental and phylogenetic approaches Eric B. Taylor, James D. McPhail, and Dalph Schluter 19. Phylogenetic studies of convergent adaptive radiations in Caribbean Anolis lizards Todd Jackman, Jonathan B. Losos, Allan Larson, and Kevin de Queiros Part VII. Macroevolutionary Patterns: 20. Molecular and morphological evolution during the post-Palaeozoic diversification of echinoids Andrew B. Smith, and D. T. J. Littlewood 21. How fast is speciation: molecular, geological and phylogenetic evidences from adaptive radiations of fish Amy R. McCune Index.

THE EFFECTS OF WINTER LENGTH ON THE GENETICS OF APPLE AND HAWTHORN RACES OF RHAGOLETIS POMONELLA (DIPTERA: TEPHRITIDAE).

Host plant-associated fitness trade-offs are central to models of sympatric speciation proposed for certain phytophagous insects. But empirical evidence for such trade-offs is scant, which has called into question the likelihood of nonallopatric speciation. Here, we report on the second in a series of studies testing for host-related selection on pupal life-history characteristics of apple- (Malus pumila L.) and hawthorn- (Crataegus mollis L. spp.) infesting races of the Tephritid fruit fly, Rhagoletis pomonella (Walsh). In particular, we examine the effects of winter length on the genetics of these flies. We have previously found that the earlier fruiting phenology of apple trees exposes apple-fly pupae to longer periods of warm weather preceding winter than hawthorn-fly pupae. Because R. pomonella has a facultative diapause, we hypothesized that this selects for pupae with more recalcitrant pupal diapauses (or slower metabolic/development rates) in the apple-fly race. A study in which we experimentally manipulated the length of the prewintering period for hawthorn-origin pupae supported this prediction. If the period preceding winter is important for apple- and hawthorn-fly pupae, then so too should be the length (duration) of winter; the rationale for this prediction is that "fast developing" pupae that break diapause too early will deplete their energy reserves and disproportionately die during long winters. To test this possibility, we chilled apple- and hawthorn-origin pupae collected from a field site near Grant, Michigan, in a refrigerator at 4°C for time periods ranging from one week to two years. Our a priori expectation was that longer periods of cold storage would select against allozyme markers that were associated with faster rates of development in our earlier study. Since these electromorphs are typically found at higher frequencies in hawthorn flies, extending the overwintering period should favor "apple-fly alleles" in both races. The results from this "overwinter" experiment supported the diapause hypothesis. The anticipated genetic response was observed in both apple and hawthorn races, as allele frequencies became significantly more "apple-fly-like" in eclosing adults surviving longer chilling periods. This indicates that it is the combination of environmental conditions before and during winter that selects on the host races. Many tests for trade-offs fail to adequately consider the interplay between insect development, host plant phenology, and local climatic conditions. Our findings suggest that such oversight may help to explain the paucity of reported fitness trade-offs.

HYBRIDIZATION STUDIES ON THE HOST RACES OF EUROSTA SOLIDAGINIS: IMPLICATIONS FOR SYMPATRIC SPECIATION.

We studied the inheritance of survival ability in host-associated populations of the tephritid fly, Eurosta solidaginis, to test predictions of sympatric speciation models. Eurosta solidaginis induces galls on two species of goldenrod, Solidago altissima and S. gigantea. The host-associated populations have been hypothesized to be host races that originated in sympatry (Craig et al. 1993). We found evidence for disruptive selection for host use, which is a critical assumption of sympatric speciation models. Each host race had higher survival rates on their host plant than on the alternative host. F1 and backcross hybrids also had lower survival rates than the pure host-race flies on their host plant. Since assortative mating occurs due to host-plant preference (Craig et al. 1993) this would select for divergence in host preference. Low hybrid survival could have been due to strong genetic incompatibilities of the populations or due to host adaptation by each population. Strong genetic incompatibilities would result in poor survival on all host plants, while host adaptation could result in low overall survival with high hybrid survival on some host plants with particularly "benign" environments. High survival of F1 , F2 , and backcross hybrids on some plant genotypes in some years supported the host adaptation hypothesis. F1 flies mated and oviposited normally and produced viable F2 and backcross hybrids indicating gene flow is possible between the host races. A few flies developed and emerged on the alternative host plant. This demonstrates that genes necessary to utilize the alternative host exist in both host races. This could have facilitated the origin of one of the populations via a host shift from the ancestral host. The inheritance of survival ability appears to be an autosomal trait. We did not find evidence that survival ability was maternally influenced or sex linked.

Sympatric speciation driven by beneficial mutations

Published models of sympatric speciation through habitat specialization require balanced polymorphism at loci affecting fitness in different habitats, but the conditions for maintenance of such polymorphism are stringent. Here I suggest a complementary mechanism favouring the evolution of habitat races, regarded as a prelude to sympatric speciation. It rests on the assumption that beneficial mutations with habitat-specific effects frequently arise and become incorporated into gene pools. When a mutation with fitness effects differing between habitats spreads in the population, there is indirect selection favouring habitat choice over random dispersal. I studied this process in a two-locus, two-habitat computer simulation. The results suggest that the conditions favouring sympatric speciation are less stringent than previously thought.

A quantitative genetic competition model for sympatric speciation

AbstractI use multilocus genetics to describe assortative mating in a competition model. The intensity of competition between individuals is influenced by a quantitative character whose value is determined additively by alleles from many loci. With assortative mating based on this character, frequency‐ and density‐dependent competition can subdivide a population with an initially unimodal character distribution. The character distribution becomes bimodal, and the subpopulations corresponding to the two modes are reproductively separated because mating is assortative. This happens if the resource distribution is unimodal, i.e. even if selection due to phenotypic carrying capacities is not disruptive. The results suggest that sympatric speciation due to frequency‐dependent selection can occur in quite general ecological scenarios if mating is assortative. I also discuss the evolution of assortative mating. Since it induces bimodal phenotype distributions, assortative mating leads to a better match of the resources if their distribution is also bimodal. Moreover, in a population with a bimodal phenotype distribution, the average strength of frequency‐dependent competition is lower than in a unimodal population. Therefore, assortative mating permits higher equilibrium densities than random mating even if the resource distribution is unimodal. Thus, even though it may lead to a less efficient resource use, assortative mating is favoured over random mating because it reduces frequency‐dependent effects of competition.

A model of sympatric speciation by sexual selection

Quantitative genetic models have indicated that sexual selection may lead to speciation in isolated populations or to exaggeration of differences in male traits along a cline. We argue that where female mate preference and opposing natural selection against conspicuous males have produced a stable equilibrium in male trait genotype, a reversed female mate preference may invade the population, initially assisted by reduced male mortality. The consequent linkage disequilibrium may lead to rapid sympatric speciation. Assuming a four-locus quantitative male trait and single-locus female preference rule and overlapping generations, we present a simulation model which indicates that reversal of female mate preference in a single individual can lead rapidly to full reproductive isolation in a small population. Speciation may be produced by the proposed mechanism in allopatry, parapatry or full sympatry. We suggest that differences in mating system and its genetic bases may account for some of the differences in speciation rates among lineages.

Reasons for the Failure of Theories

A theory may be invalid, not owing to erroneous observations or the invocation of an inappropriate law, but because of the use of equivocal terms. This is demonstrated for Darwin's failed model of sympatric speciation through the principle of divergence.

Host fidelity is an effective premating barrier between sympatric races of the apple maggot fly.

Models of sympatric speciation for phytophagous insects posit a central role for host plant-associated mating as a premating isolating mechanism in lieu of geographic barriers to gene flow. Here, by means of three mark-and-recapture studies, we confirm that host fidelity (i.e., the tendency of an insect to reproduce on the same host species that it used in earlier life-history stages) restricts gene flow between sympatric apple- and hawthorn-infesting races of Rhagoletis pomonella (Diptera: Tephritidae) to approximately 6% per generation. Genetically based differences in host preference, adult eclosion under the "correct" host species, and allochronic isolation contribute to host fidelity in various degrees in the races. The results verify that host-associated adaptation can produce reproductive isolation as a correlated character (a key premise of sympatric speciation). The study also represents one of the few or perhaps only example in animals where the intra-specific isolating effects of specific phenotypes have been quantified in nature.

A cytogenetic analysis of the Simulium ochraceum species complex (Diptera: Simuliidae) in Central America

A cytobiotaxonomic study of the medically important insect vector Simulium ochraceum s.l. revealed two sibling species and one cytotype from various endemic and nonendemic zones of human onchocerciasis in Guatemala and Mexico. Polytene chromosome maps and idiograms as well as notes on the biology of the three taxa designated S. ochraceum A, S. ochraceum B, and S. ochraceum C within the subgenus Psilopelmia are presented. All three taxa exhibit distinct sex chromosomes and taxon-specific suites of autosomal inversion polymorphisms. Simulium ochraceum C differs from both S. ochraceum A and S. ochraceum B by five interspecific inversions designated IIS-7,8 and IIIL-12, 13 + 14, 15. The three taxa exhibit niche and biting preferences, with S. ochraceum A being highly anthropophilic. Analysis of autosomal inversion polymorphism profiles indicates S. ochraceum A has long-range dispersal capability. Our results are consistent with the general findings that in the Simuliidae, sibling speciation may be suspected wherever a morphospecies occupies different niches in a stream continuum. We find for the first time an apparent partitioning of taxa by altitude. Simulium ochraceum A may be a primary vector of human onchocerciasis in Guatemala, as its vertical distribution is coincident with that of the highest areas of nodule prevalence in the human population. A genotypic component of variation in vectorial capacity of S. ochraceum A populations seems to occur, since the Y4 chromosome and its X chromosome counterpart are associated with hyperendemic areas of human onchocerciasis. Our observation that a supernumerary band, 37B1Hb, is associated with sex determination in two of the taxa may be of significance for the elucidation of the molecular basis of sex determination and possible resolution of issues pertinent to the general model of sympatric speciation in the Simuliidae.

Ribosomal RNA sequencing of members of the Crypthecodinium cohnii (Dinophyceae) species complex; comparison with soluble enzyme studies.

Sixty-five members of the Crypthecodinium cohnii species complex were analyzed for sequence differences within the D2 region of the 23S ribosomal RNA molecule. On the basis of 46 sequence differences the strains fell into 19 distinct ribosets (strains of identical sequence), some with many members. Members of four of the seven major sibling species (widespread breeding groups) were each found within single ribosets. Members of three other major sibling species were each, however, divided into two ribosets by a single sequence difference correlated with geographic separation and with previously reported electrophoretic polymorphisms of soluble enzymes within the sibling species. In addition to members of major sibling species, some ribosets include many minor sibling species (each represented by only one strain). Of 38 minor sibling species, 22 shared sequence with a major sibling species. Of these 22, 14 were identical in soluble enzymes to their related major sibling species or differed by only one of three enzymes. Other minor sibling species appear to have diverged extensively from any others in both rRNA sequence and electrophoretic profile. As a group, major sibling species differ markedly in the number of minor sibling species associated with them, suggesting differences in frequency of sexually isolating events in their past histories. These findings are discussed in the context of the previously proposed model of sympatric speciation.

Sympatric speciation: A simulation model of imperfect assortative mating

The computer model of sympatric speciation (Fialkowski, 1988, J. theor. Biol. 130, 379) has been expanded and partial assortative mating incorporated. The model is intended as a working hypothesis and offers proposals for further research on sympatric speciation. As a working hypothesis it states that sympatric speciation should be looked for in populations where heterozygotes' fitness is below the average fitness of homozygotes and that assortative mating can be incubated in particular cases of stable conditions determined by Maynard Smith & Hoekstra (1980, Genet. Res. 35, 45) when polymorphs co-exist without heterozygotic overdominance. The hypothesis states that two different mechanisms of sympatric speciation exist: the first mechanism is operational in rather stable environments and (taking into account reversibility of the speciation process) may last as long as a million generations; in this mechanism a population in equilibrium is “eroded from inside”. The cases when the emergence of nascent species is not accompanied by any change in environment should be researched to establish its biological existence. The second mechanism of emergence of the two populations is extremely fast (usually less than 200 generations) and is the result of notable changes in the environment. The hypothesis states that increased homozygosity in populations must exist and be observed at least temporarily as a distinct deviation from the Hardy-Weinberg recombination principle.

Genetic variation among apple and hawthorn host races of Rhagoletis pomonella across an ecological transition zone in the Mid‐Western United States

AbstractIn previous studies, we have shown that apple and hawthorn populations of Rhagoletis pomonella (Diptera: Tephritidae) represent partially reproductively isolated and genetically differentiated host races; a result consistent with predictions of sympatric speciation models. The geographic pattern of allozyme variation for these flies is complex, however, as inter‐host differences are superimposed on latitudinal allele frequency clines within the races. In addition, pronounced allele frequency shifts exist among R. pomonella populations across three major ecological transition zones in the mid‐western United States. This suggests that selection related to environmental heterogeneity is responsible for the allele frequency shifts, but does not rule out secondary contact as an alternative possibility. Resolution of this issue is important, because if secondary contact is involved, then we would have to reassess the relationship host race formation has with speciation in the R. pomonella group.Here, we present results from a detailed genetic analysis of fly populations spanning the deciduous/prairie transition zone near the border between the states of Wisconsin and Illinois. Allele frequencies for hawthorn populations within the zone formed ‘spikes’, rather than the expected steps, and these frequency peaks correlated with variation in local ambient temperature conditions. Ambient temperature, and not secondary contact, therefore appears to be an important determinant of the shape of R. pomonella allele frequency clines. Allele frequency heterogeneity was also observed among apple populations, but was less pronounced compared to that for hawthorn flies. This suggests that ambient temperature differentially affects the host races, possibly through differences in the fruiting phenologies of apple and hawthorn trees. Several pairs of linked loci displayed concordant allele frequency changes and were in disequilibrium among both apple and hawthorn populations along the Wisconsin/Illinois transect. Although we do not know the reason for the observed pattern of disequilibrium, site to site variation in levels of inter‐host migration, coupled with selection, seem the most likely explanations. We conclude by discussing how host specific adaptations, such as those associated with ambient temperature, may interact with host recognition traits to drive the sympatric speciation process for R. pomonella group flies.

Speciation in the sub‐Antarctic weevil genus Dusmoecetes Jeannel (Coleoptera: Curculionidae)

AbstractRelatively few instances of sympatric speciation have been reported in the literature, and both theoretical and empirical studies of this mode of speciation remain controversial. Recently, a model of sympatric speciation less restrictive than earlier ones has been proposed. This study presents a hypothetical speciation scenario, based on current observations, which seems to be consistent with the new model. Two morphologically similar, though ecologically separated, species are identified in the Dusmoecetes similis (C. O. Waterhouse) species complex on Marion Island (46° 54′S, 37° 45′E), based on a study of the morphology, biology and ecology of the group. Differences between the demands placed on angiosperm‐ and bryophyte‐feeding members of the complex, and the differing demands of bryophyte and angiosperm‐dominated communities, coupled with low vagility and a high degree of assortative mating, suggest that a sympatric model can be used to explain speciation in this genus, which probably occurred within the last 10,000 years. Differences between Dusmoecetes marioni Jeannel and D. Similis (Waterhouse) are discussed, and a lectotype designated for the latter species.

THE COIL POLYMORPHISM IN PARTULA SUTURALIS DOES NOT FAVOR SYMPATRIC SPECIATION

Theories of sympatric speciation have a long and controversial history (Mayr, 1963) and have enjoyed a resurgence of interest in recent years (e.g., Maynard Smith, 1966; Bush, 1975; Tauber and Tauber, 1977; Rosenzweig, 1978). Of particular interest is the role of behavioral isolation, which has generally been considered to evolve along with divergence in allopatric populations or by selection against hybrids after secondary contact. It has also been suggested that behavioral isolation can precede the development of postmating isolation (Bush, 1975; Tauber and Tauber, 1977). In this case, genetically simple behavioral differences might begin the process of genetic divergence of sympatric populations. The purported examples of this mechanism, however, have been criticized (Futuyma and Mayer, 1980; Henry, 1985), and there is no general agreement about the importance of sympatric speciation. Gittenberger (1988) has proposed a model of sympatric speciation, resulting from reproductive isolation due to differences in the direction of shell-coiling in snails. In the species that have been examined, the direction of coiling is controlled by a single pair of alleles. The expression of the genotype, however, is delayed by one generation, because the phenotype is determined by the mother's genotype. Gittenberger cites evidence from several species that snails with opposite coiling have difficulty in mating. He proposes that the consequent assortative mating could lead to sympatric speciation. Given the controversy surrounding sympatric speciation, it is important to evaluate such models carefully. The purpose of this note is to examine the properties of polymorphism for coiling that relate to sympatric speciation. Our analysis will focus on Partula suturalis, one of the few species of snails that is polymorphic for the direction of coiling and the only one to be studied extensively. Mating between snails of opposite coil is difficult (Lipton and Murray, 1979), and individuals without enough potential mates of the same coil produce fewer offspring (Johnson, 1982). This generates positive frequency-dependent selection (a disadvantage of rare types) and leads to monomorphism within populations. In nature, polymorphic populations are only found in steep clines between areas that are uniformly sinistral and dextral. The dextral populations of P. suturalis occur in the presence of sympatric and closely related sinistral species. The difference in coil has probably come about by selection against hybridization, favoring enhanced premating isolation (Clarke and Murray, 1969). The evidence for such selection raises the question of whether the variation in coiling could lead to genetic subdivision and speciation within P. suturalis itself.

Genetic correlations between morphology and antipredator behaviour in natural populations of the garter snake Thamnophis ordinoides.

The genetic coupling of morphology and behaviour means that the evolution of the two types of traits will not be independent: changes in behaviour will result in changes in morphology and vice versa. This might explain nonadaptive differences in morphology through indirect selection on correlated characters of other categories. Genetic correlations between morphology and behaviour are also the basis for some models of sympatric speciation and of the stability of polymorphisms. Morphology and behaviour are often correlated in nature and a genetic basis for such couplings has been demonstrated. I present here evidence that colour pattern and antipredator behaviour are genetically coupled in natural populations of the garter snake Thamnophis ordinoides. Similar phenotypic correlations between pattern and behaviour exist among species of North American snakes, indicating that selection for particular combinations of traits may help to maintain genetic covariances and colour polymorphism in Thamnophis ordinoides.

Chromosomal rearrangements, speciation and reproductive isolation: The example of two karyotypic species of the genus Sorex

Journal of Evolutionary BiologyVolume 2, Issue 5 p. 373-378 Free Access Chromosomal rearrangements, speciation and reproductive isolation: The example of two karyotypic species of the genus Sorex Cornelis R. Neet, Cornelis R. Neet Institut de Zoologie et d'Ecologie Animale, Université de Lausanne, Bâtiment de Biologie, CH-1015 Lausanne, SwitzerlandSearch for more papers by this authorJacques Hausser, Jacques Hausser Institut de Zoologie et d'Ecologie Animale, Université de Lausanne, Bâtiment de Biologie, CH-1015 Lausanne, SwitzerlandSearch for more papers by this author Cornelis R. Neet, Cornelis R. Neet Institut de Zoologie et d'Ecologie Animale, Université de Lausanne, Bâtiment de Biologie, CH-1015 Lausanne, SwitzerlandSearch for more papers by this authorJacques Hausser, Jacques Hausser Institut de Zoologie et d'Ecologie Animale, Université de Lausanne, Bâtiment de Biologie, CH-1015 Lausanne, SwitzerlandSearch for more papers by this author First published: September 1989 https://doi.org/10.1046/j.1420-9101.1989.2050373.xCitations: 7AboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Citing Literature Volume2, Issue5September 1989Pages 373-378 RelatedInformation

Speciation in black flies

In many Simuliidae, patterns of spatial and temporal relationships among the most closely related species are more readily interpreted in terms of sympatric speciation than of allopatric speciation. Specific examples are (i) the allotriploid taxa in Gymnopais and other genera, (ii) the black fly faunas of geologically recent islands (Tahiti), and (iii) species in Prosimulium onychodactylum, a prototype of a continental multisibling species complex. A model of sympatric speciation is presented based on coadaptation of polymorphic sex chromosomes in pairs reinforced by progressive development of assortative mating. This model predicts that (i) populations should frequently exhibit sex-chromosome polymorphism, (ii) these sex-chromosome polymorphisms, and autosomal ones, should in some cases display linkage or association disequilibria, (iii) species pairs or complexes should be incurred that differ only in sex chromosomes and that share extensive ancestral autosomal polymorphisms, and (iv) such species should differ in their biology and perhaps their present-day distribution. Recent publications and observations are in accordance, in general, with predictions from the model. Genetic control, e.g., of diapause, larval developmental timing, and niche preference or ethology, could substitute as a basis of incipient cleavage. The evidence for sympatric speciation is purely inferential, but this is equally true for the allopatric interpretation, and in black flies the circumstantial evidence for prevalence of sympatric speciation appears more compelling. This is not to deny the efficacy of allopatry and founder effect in the origin of some species complexes.Key words: sympatric speciation, black fly, evolution.

REPRODUCTIVE ISOLATION BY HOST SPECIFICITY IN A PAIR OF PHYTOPHAGOUS LADYBIRD BEETLES.

Crossing experiments and food-choice tests show that two sympatric species of phytophagous ladybird beetles, Epilachna niponica and E. yasutomii, are reproductively isolated by host-plant specificity. Adult beetles selected their natural hosts when given choices, though some accepted the host of the other species when no choice was offered. In each species, survival of larvae to the second instar was significantly higher on their own host plant. No evidence for sexual isolation, gametic isolation, hybrid inviability, or reduced hybrid fertility was detected. Reproductive isolation by host specificity is an important prerequisite for certain models of sympatric speciation. Although the present example supports the plausibility of such models, an allopatric origin of host-plant specificity cannot be discounted.

SYMPATRIC SPECIATION IN SNAILS; A LARGELY NEGLECTED MODEL.

EvolutionVolume 42, Issue 4 p. 826-828 Note and CommentFree Access SYMPATRIC SPECIATION IN SNAILS; A LARGELY NEGLECTED MODEL Edmund Gittenberger, Edmund Gittenberger Systematic Zoology Section, Leiden University, c/o Rijksmuseum van Natuurlijke Historie, P.O. Box 9517, 2300 RA, Leiden, THE NETHERLANDSSearch for more papers by this author Edmund Gittenberger, Edmund Gittenberger Systematic Zoology Section, Leiden University, c/o Rijksmuseum van Natuurlijke Historie, P.O. Box 9517, 2300 RA, Leiden, THE NETHERLANDSSearch for more papers by this author First published: July 1988 https://doi.org/10.1111/j.1558-5646.1988.tb02502.xCitations: 46AboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinked InRedditWechat Citing Literature Volume42, Issue4July 1988Pages 826-828 ReferencesRelatedInformation