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1.
Erica L. Larson C. Guilherme Becker Eliana R. Bondra Richard G. Harrison 《Ecology and evolution》2013,3(4):985-1002
Hybrid zones provide insight into the nature of species boundaries and the evolution of barriers to gene exchange. Characterizing multiple regions within hybrid zones is essential for understanding both their history and current dynamics. Here, we describe a previously uncharacterized region of a well‐studied hybrid zone between two species of field crickets, Gryllus pennsylvanicus and G. firmus. We use a combination of mitochondrial DNA sequencing, morphological data, and modeling of environmental variables to identify the ecological factors structuring the hybrid zone and define patterns of hybridization and introgression. We find an association between species distribution and natural habitat; Gryllus pennsylvanicus occupies natural habitat along forest edges and natural clearings, whereas G. firmus occupies more disturbed areas in agricultural and suburban environments. Hybridization and introgression occur across patch boundaries; there is evidence of substantial admixture both in morphological characters and mtDNA, over a broad geographic area. Nonetheless, the distribution of morphological types is bimodal. Given that F1 hybrids are viable and fertile in the lab, this suggests that strong pre‐zygotic barriers are operating in this portion of the hybrid zone. 相似文献
2.
The grasshoppers Chorthippus brunneus and Chorthippus jacobsi are easily distinguished by male calling song and the number of stridulatory pegs on the hind femur, and form a mosaic hybrid zone in northern Spain. In this paper, we fit a two-dimensional cline to variation in male calling song characters, which are of particular interest as they are likely to be involved in mate choice by females. As with variation in peg number, local habitat makes only a small contribution in explaining deviations in mean song score from clinal expectations. However, the fitted width of the cline for song characters is significantly narrower than for peg number, suggesting that mating signals may be associated with reduced hybrid fitness in the field and that recombination rates are sufficient to allow clines for different characters to diverge in width. Despite this, estimates for the overall elevation in linkage disequilibrium at the zone center, based on covariance between peg and song characters, reveal a substantial overrepresentation of parental genotypes at the cline center relative to the expectations of a tension zone of similar width. Examination of covariance at individual sites reveals that this inflated estimate of linkage disequilibrium is caused by several sites where the distribution of phenotypes is effectively bimodal. This substantial variation in linkage disequilibrium at the cline center could result from local variation in the strength of assortative mating or selection against hybrids, or may reflect the long-distance colonization of empty habitat from outside the hybrid zone, which would continually create new contacts between parental genotypes at the cline center. Hybrid zones like this, in which strong linkage disequilibrium occurs in some situations but not in others, are of particular relevance to speciation research and allow investigation of the spread of combinations of alleles through different genetic and ecological backgrounds. 相似文献
3.
Jessica Purcell Sacha Zahnd Anouk Athanasiades Rebecca Türler Alan Brelsford 《Molecular ecology》2016,25(19):4866-4874
Research on hybridization between species provides unparalleled insights into the pre‐ and postzygotic isolating mechanisms that drive speciation. In social organisms, colony‐level incompatibilities may provide additional reproductive barriers not present in solitary species, and hybrid zones offer an opportunity to identify these barriers. Here, we use genotyping‐by‐sequencing to sequence hundreds of markers in a hybrid zone between two socially polymorphic ant species, Formica selysi and Formica cinerea. We characterize the zone, determine the frequency of hybrid workers, infer whether hybrid queens or males are produced and investigate whether hybridization is influenced by colony social organization. We also compare cuticular hydrocarbon profiles and aggression levels between the two species. The hybrid zone exhibits a mosaic structure. The asymmetric distribution of hybrids skewed towards F. cinerea suggests a pattern of unidirectional nuclear gene flow from F. selysi into F. cinerea. The occurrence of backcrossed individuals indicates that hybrid queens and/or males are fertile, and the presence of the F. cinerea mitochondrial haplotype in 97% of hybrids shows that successful F1 hybrids will generally have F. cinerea mothers and F. selysi fathers. We found no evidence that social organization contributes to speciation, because hybrids occur in both single‐queen and multiple‐queen colonies. Strongly differentiated cuticular hydrocarbon profiles and heightened interspecific aggression further reveal that species recognition cues are both present and perceived. The discovery of fertile hybrids and asymmetrical gene flow is unusual in ants, and this hybrid zone will therefore provide an ideal system with which to investigate speciation in social insects. 相似文献
4.
An important issue in evolutionary biology is understanding the pattern of G matrix variation in natural populations. We estimated four G matrices based on the morphological traits of two cricket species, Gryllus firmus and G. pennsylvanicus, each reared in two environments. We used three matrix comparison approaches, including the Flury hierarchy, to improve our ability to perceive all aspects of matrix variation. Our results demonstrate that different methods perceive different aspects of the matrices, which suggests that, until more is known about these methods, future studies should use several different statistical approaches. We also found that the differences in G matrices within a species can be larger than the differences between species. We conclude that the expression of the genetic architecture can vary with the environment and that future studies should compare G matrices across several environments. We also conclude that G matrices can be conserved at the level of closely related species. 相似文献
5.
Many hybrid zones contain a deficit of hybrid genotypes relative to expectations from tension zone models. This is often associated with separation of parental genotypes into distinct habitats (mosaicism), but sometimes parentals can be found co-occuring in the same local population (bimodality). In both cases, prezygotic isolation may play an important role in determining the genotypic composition of the zone. Chorthippus brunneus and C. jacobsi (Orthoptera: Acrididae) meet and form a complex hybrid zone in northern Spain. Analysis of stridulatory peg numbers reveals partial spatial and seasonal isolation in a 25 km2 area of the zone: C. jacobsi phenotypes predominate in June and July and are present in both valley and mountain habitats; C. brunneus phenotypes predominate in August and are restricted to valley habitats, always in sympatry with C. jacobsi. Strong assortative mating was observed in laboratory mating experiments. Spatial, seasonal and behavioural isolation combine to produce strong premating isolation in the study area. These results suggest a role for premating isolation in maintaining both the mosaic structure and bimodality of this hybrid zone. 相似文献
6.
MARLENE ZUK 《Ecological Entomology》1987,12(3):349-354
ABSTRACT. 1. Gregarines, debilitating gut parasites, significantly reduced longevity and increased weight loss in the field cricket Gryllus pennsylvanicus Burmeiser when adults were kept on suboptimal diets, but in G.pennsylvanicus and G.veletis (Alexander and Bigelow) fed ad libitum , weight change, longevity, and fecundity were not significantly different in infected and control individuals.
2. Adults harbouring gregarines at eclosion took significantly longer to develop from the second and third instars than did uninfected adults.
3. Longevity of nymphs kept in the laboratory without food was decreased in infected individuals compared with uninfected ones, but not significantly so.
4. The evolutionary and ecological implications of nonlethal parasites are discussed. 相似文献
2. Adults harbouring gregarines at eclosion took significantly longer to develop from the second and third instars than did uninfected adults.
3. Longevity of nymphs kept in the laboratory without food was decreased in infected individuals compared with uninfected ones, but not significantly so.
4. The evolutionary and ecological implications of nonlethal parasites are discussed. 相似文献
7.
沙蟋翅多型性的调控机理 总被引:1,自引:0,他引:1
沙蟋Gryllus firmus Zera&Denno成虫的后翅有长翅和短翅2种类型,是翅多型性机理研究的极佳模式昆虫。长翅成虫从第5日龄开始迁飞,而短翅成虫的主要特点是繁殖。除了翅的表型差异外,长翅成虫的飞行肌发达,呈褐色;卵巢幼小,直到飞行停止后(大约在10d以后)才开始发育。而短翅成虫的飞行肌退化并呈乳白色;卵巢在第4日龄就发育成熟,表现为卵巢硕大。对翅多型性机理的深入研究,将有利于了解沙蟋迁飞和扩散的内在机理,为准确地预测预报该虫的发生提供重要的理论和实际依据。文章概述沙蟋翅多型性与外界环境的相互关系,以及体内生化代谢和内分泌激素等的变化对该虫迁飞和生殖的影响和作用,进而探讨翅多型的遗传机制和进化意义等问题。 相似文献
8.
Calling song and selective phonotaxis in the field crickets,Gryllus firmus andG. pennsylvanicus (Orthoptera: Gryllidae) 总被引:1,自引:1,他引:0
The field cricket species, Gryllus firmusand G. pennsylvanicus,occur in a mosaic hybrid zone that roughly parallels the eastern slope of the Appalachian mountains in the northeastern United States. It is important to know what role, if any, the calling song plays in mate choice in sympatric and allopatric populations. In this report, we present results on the variability of calling song properties along transects across this hybrid zone. We also present the results of experiments on phonotactic selectivity of females from an allopatric population of G. firmus.The male calling song of allopatric G. firmuswas significantly slower in temporal rhythm (i. e., chirp and pulse repetition rates) and lower in pitch (i.e., dominant frequency) than that of allopatric G. pennsylvanicus.Calling song properties of males recorded in the hybrid zone varied considerably in temporal and spectral properties. In two-stimulus (choice) phonotaxis experiments, allopatric females of G. firmuspreferred synthetic calling songs with conspecific pulse repetition rates over songs that had lower and higher pulse rates. This preference persisted even when the sound pressure levels of alternative stimuli were unequal. Therefore, allopatric females of G. firmuscan discriminate between conspecific and heterospecific calling songs. Whether or not this same selectivity is present in sympatric populations remains unclear. Investigations of phonotactic selectivity in other allopatric and sympatric populations of both species are currently under way. 相似文献
9.
10.
Long-term studies of hybrid zones can provide valuable insight into a number of questions that have long attracted the attention of evolutionists. These questions range from the stability and fate of hybrid zones to the relative fitness of hybrids. In this paper we report the results of a 14-year survey of the Allonemobius fasciatus-Allonemobius socius hybrid zone. Populations were collected intensively in 1986 and 1987 and then more sporadically through the end of the 1980s and throughout the 1990s. By documenting changes in the genetic composition of populations near and within the zone during this period of time we assessed: the strength of the reproductive isolation between the two species; the relative growth rates (which can be considered a surrogate of relative fitness) of genotype classes corresponding to hybrids and to pure species individuals; and, the power of single-year and multi-year measurements of relative growth rates to predict changes in the genetic composition of mixed populations through time. In brief, we found very large year-to-year variation in the relative growth rates of pure species and hybrid individuals. This variation may reflect the fact that both species are at the edge of their range and perhaps at the limits of their ability to deal with environmental perturbations. As a consequence of the variation, even multi-year estimates of relative growth rates often provided imprecise predictions regarding the future genotypic composition of mixed populations. Despite our limited ability to predict the dynamics of individual populations, some trends are apparent. A. socius, the southern species, has clearly increased in frequency along a transect through the Appalachian Mountains, indicating that the zone is moving north in this region. In contrast, the zone appeared to be more stable along the East Coast transect. Within mixed populations, character-index profiles are often bimodal and stable through time, indicating relatively strong reproductive isolation between the two species that is not being reinforced, nor is it breaking down. 相似文献
11.
12.
Florentine Riquet Cathy Liautard‐Haag Lucy Woodall Carmen Bouza Patrick Louisy Bojan Hamer Francisco Otero‐Ferrer Philippe Aublanc Vickie Bduneau Olivier Briard Tahani El Ayari Sandra Hochscheid Khalid Belkhir Sophie Arnaud‐Haond Pierre‐Alexandre Gagnaire Nicolas Bierne 《Evolution; international journal of organic evolution》2019,73(4):817-835
Diverging semi‐isolated lineages either meet in narrow clinal hybrid zones, or have a mosaic distribution associated with environmental variation. Intrinsic reproductive isolation is often emphasized in the former and local adaptation in the latter, although both reduce gene flow between groups. Rarely are these two patterns of spatial distribution reported in the same study system. Here, we report that the long‐snouted seahorse Hippocampus guttulatus is subdivided into discrete panmictic entities by both types of hybrid zones. Along the European Atlantic coasts, a northern and a southern lineage meet in the southwest of France where they coexist in sympatry—i.e., in the same geographical zone—with little hybridization. In the Mediterranean Sea, two lineages have a mosaic distribution, associated with lagoon‐like and marine habitats. A fifth lineage was identified in the Black Sea. Genetic homogeneity over large spatial scales contrasts with isolation maintained in sympatry or close parapatry at a fine scale. A high variation in locus‐specific introgression rates provides additional evidence that partial reproductive isolation must be maintaining the divergence. We find that fixed differences between lagoon and marine populations in the Mediterranean Sea belong to the most differentiated SNPs between the two Atlantic lineages, against the genome‐wide pattern of structure that mostly follow geography. These parallel outlier SNPs cluster on a single chromosome‐wide island of differentiation. Since Atlantic lineages do not map to lagoon‐sea habitat variation, genetic parallelism at the genomic island suggests a shared genetic barrier contributes to reproductive isolation in contrasting contexts–i.e., spatial versus ecological. We discuss how a genomic hotspot of parallel differentiation could have evolved and become associated both with space and with a patchy environment in a single study system. 相似文献
13.
Inbreeding, the mating of close relatives, is known to have deleterious effects on fitness traits in organisms. Developmental stability (DS) and canalization may represent two processes that allow an organism to maintain a stable development that will produce the fittest phenotype. Inbreeding is thus expected to affect either DS or canalization. We tested if inbreeding affects DS and canalization using an inbreeding experiment on the cricket Gryllus firmus. We compared mean length, fluctuating asymmetry (as an index of DS), and morphological variation (as an index of canalization) of four limb traits between seven highly inbred lines, their F1 crosses, and outbred lines originated from the same stock population and maintained in the same environmental conditions. We show evidence for moderate inbreeding depression on the four measures of leg length. The nonsystematic difference in fluctuating asymmetry indices between breed types indicates that inbreeding or heterozygosity did not affect DS, or that fluctuating asymmetry is not a reliable index of DS. In contrast, inbreeding appears to affect canalization, as shown by the significantly higher variation in inbred lines compared to other lines. Identical low variation values in the crossbred and outbred lines indicate that heterozygosity could affect canalization. High variation in morphological variation and fluctuating asymmetry within crossbred or inbred lines, however, suggest the effect of recessive deleterious alleles on both canalization and DS. Although the strong correlation in morphological variation among traits suggests that identical genetic mechanisms govern canalization for all the limb traits, the absence of significant correlation in fluctuating asymmetry among traits causes us to reject this hypothesis for DS. For most of the traits, morphological variation and fluctuating asymmetry were not significantly correlated, which support the hypothesis that canalization and DS consist in two distinct mechanisms. 相似文献
14.
Many models of life history evolution assume trade-offs between major life history traits; however, these trade-offs are often not found. The Y model predicts that variation in acquisition can mask underlying allocation trade-offs and is a major hypothesis explaining why negative relationships are not always found between traits that are predicted to trade-off with one another. Despite this model's influence on the field of life history evolution, it has rarely been properly tested. We use a model system, the wing dimorphic cricket, Gryllus firmus as a case study to test the assumptions and predictions of the Y model. By experimentally altering the acquisition regime and by estimating energy acquisition and energy allocation directly in this species, we are able to explicitly test this important model. Overall, we find strong support for the predictions of the Y model. 相似文献
15.
Varvara Vedenina Anja Klöpfel Norbert Elsner 《Biological journal of the Linnean Society. Linnean Society of London》2012,107(2):383-397
The closely related grasshopper species Stenobothrus rubicundus and Stenobothrus clavatus are known to hybridize in a very narrow contact zone on Mt. Tomaros in northern Greece. These species produce very different and complex courtship songs accompanied with visual display. We analyzed the courtship songs and underlying stridulatory movements of the hind legs in natural hybrids from Mount Tomaros. The two species were also hybridized in the laboratory and their songs were compared with the songs of the natural hybrids. Some hybrid songs were shown to have intermediate features between parental songs, whereas other hybrid songs comprised completely new elements. The clavatus‐like song elements were found to dominate in hybrid songs. These song features may influence the mating success of hybrid males in the contact zone. A comparison of hybrid songs with the song pattern of the north European S. rubicundus populations allowed us to suggest a scenario of S. rubicundus and S. clavatus origin. © 2012 The Linnean Society of London, Biological Journal of the Linnean Society, 2012, ?? , ??–??. 相似文献
16.
Among the Orthoptera, wing dimorphism, where one morph is long‐winged and flight capable while the other is short‐winged and flight incapable, is common and believed to be maintained in populations due to trade‐offs to flight capability. In males, macropterous individuals call less than micropterous individuals and as a consequence obtain fewer matings. This trade‐off is hypothesized to be mediated by the energetic costs of calling. In this paper we report results for a path analysis examining lipid weight and DLM (dorso longitudinal muscle) condition of male Gryllus firmus. We found that as DLM condition changes from a nonfunctional to a functional state, call duration decreases, and as lipid weight increases, call duration increases. The most important linked path was wing morph → DLM condition → call duration. This model is consistent with the prediction that the trade‐off between wing morph and call duration is mediated via DLM and lipid stores. 相似文献
17.
Genotype‐environment associations support a mosaic hybrid zone between two tidal marsh birds 下载免费PDF全文
Jennifer Walsh Rebecca J. Rowe Brian J. Olsen W. Gregory Shriver Adrienne I. Kovach 《Ecology and evolution》2016,6(1):279-294
Local environmental features can shape hybrid zone dynamics when hybrids are bounded by ecotones or when patchily distributed habitat types lead to a corresponding mosaic of genotypes. We investigated the role of marsh‐level characteristics in shaping a hybrid zone between two recently diverged avian taxa – Saltmarsh (Ammodramus caudacutus) and Nelson's (A. nelsoni) sparrows. These species occupy different niches where allopatric, with caudacutus restricted to coastal marshes and nelsoni found in a broader array of wetland and grassland habitats and co‐occur in tidal marshes in sympatry. We determined the influence of habitat types on the distribution of pure and hybrid sparrows and assessed the degree of overlap in the ecological niche of each taxon. To do this, we sampled and genotyped 305 sparrows from 34 marshes across the hybrid zone and from adjacent regions. We used linear regression to test for associations between marsh characteristics and the distribution of pure and admixed sparrows. We found a positive correlation between genotype and environmental variables with a patchy distribution of genotypes and habitats across the hybrid zone. Ecological niche models suggest that the hybrid niche was more similar to that of A. nelsoni and habitat suitability was influenced strongly by distance from coastline. Our results support a mosaic model of hybrid zone maintenance, suggesting a role for local environmental features in shaping the distribution and frequency of pure species and hybrids across space. 相似文献
18.
MARLENE ZUK 《Ecological Entomology》1987,12(3):341-348
ABSTRACT. 1. Gregarines, debilitating protozoan gut parasites, were monitored in two species of field cricket, Gryllus veletis (Alexander and Bigelow) and G.pennsylvanicus Burmeister, in northern Michigan in 1983 and 1984.
2. Gregarines were found in 31–51% of G.veletis individuals and 50–70% of G.pennsylvanicus.
3. Males were more heavily infected than females in G. veleris , but G.pennsylvanicus males and females had nearly equal infection levels; this disparity resulted in an overall lower infection rate for G. veletis.
4. Both species had fewer gregarines in 1983 than in 1984, possibly due to the adverse effect of drier conditions in 1983 on development of parasite cysts in the soil.
5. Levels of infection were not constant throughout the breeding season for either cricket species.
6. Body size was not correlated with parasite load in either G. veletis or G.pennsylvanicus.
7. Adult age was unrelated to gregarine level in G. veferis , whereas G.pennsylvanicus showed a positive correlation between adult age and parasite load during two non-consecutive weeks of the breeding season. 相似文献
2. Gregarines were found in 31–51% of G.veletis individuals and 50–70% of G.pennsylvanicus.
3. Males were more heavily infected than females in G. veleris , but G.pennsylvanicus males and females had nearly equal infection levels; this disparity resulted in an overall lower infection rate for G. veletis.
4. Both species had fewer gregarines in 1983 than in 1984, possibly due to the adverse effect of drier conditions in 1983 on development of parasite cysts in the soil.
5. Levels of infection were not constant throughout the breeding season for either cricket species.
6. Body size was not correlated with parasite load in either G. veletis or G.pennsylvanicus.
7. Adult age was unrelated to gregarine level in G. veferis , whereas G.pennsylvanicus showed a positive correlation between adult age and parasite load during two non-consecutive weeks of the breeding season. 相似文献
19.
Wolbachia are cytoplasmically inherited alpha-proteobacteria that can cause cytoplasmic incompatibility (CI) in insects. This incompatibility between sperm and egg is evident when uninfected females mate with infected males. Wolbachia-driven reproductive incompatibilities are of special interest because they may play a role in speciation. However, the presence of Wolbachia does not always imply incompatibility. The field crickets Gryllus firmus and G. pennsylvanicus exhibit a very clear unidirectional incompatibility and have been cited as a possible example of Wolbachia-induced CI. Here, we conduct curing experiments, intra- and interspecific crosses, cytological examination of Wolbachia in testes and Wolbachia quantifications through real-time PCR. All of our data strongly suggest that Wolbachia are not involved in the reproductive incompatibility between G. firmus and G. pennsylvanicus. 相似文献
20.
Abstract. 1. The grasshopper species Chorthippus brunneus and C. jacobsi form a complex mosaic hybrid zone in northern Spain. Two mark–release–recapture studies were carried out near the centre of the zone in order to make direct estimates of lifetime dispersal.
2. A model framework based on a simple random walk in homogeneous habitat was extended to include the estimation of philopatry and flying propensity. Each model was compared with the real data, correcting for spatial and temporal biases in the data sets.
3. All four data sets (males and females at each site) deviated significantly from a random walk. Three of the data sets showed strong philopatry and three had a long dispersal tail, indicating a low propensity to move further than predicted by the random walk model.
4. Neighbourhood size estimates were 76 and 227 for the two sites. These estimates may underestimate effective population size, which could be increased by the long tail to the dispersal function. The random walk model overestimates lifetime dispersal and hence the minimum spatial scale of adaptation.
5. Best estimates of lifetime dispersal distance of 7–33 m per generation were considerably lower than a previous indirect estimate of 1344 m per generation. This discrepancy could be influenced by prezygotic isolation, an inherent by-product of mosaic hybrid zone structure. 相似文献
2. A model framework based on a simple random walk in homogeneous habitat was extended to include the estimation of philopatry and flying propensity. Each model was compared with the real data, correcting for spatial and temporal biases in the data sets.
3. All four data sets (males and females at each site) deviated significantly from a random walk. Three of the data sets showed strong philopatry and three had a long dispersal tail, indicating a low propensity to move further than predicted by the random walk model.
4. Neighbourhood size estimates were 76 and 227 for the two sites. These estimates may underestimate effective population size, which could be increased by the long tail to the dispersal function. The random walk model overestimates lifetime dispersal and hence the minimum spatial scale of adaptation.
5. Best estimates of lifetime dispersal distance of 7–33 m per generation were considerably lower than a previous indirect estimate of 1344 m per generation. This discrepancy could be influenced by prezygotic isolation, an inherent by-product of mosaic hybrid zone structure. 相似文献