scholarly journals Dispersal predicts hybrid zone widths across animal diversity: Implications for species borders under incomplete reproductive isolation

2018 ◽  
Author(s):  
Jay P. McEntee ◽  
J. Gordon Burleigh ◽  
Sonal Singhal
Keyword(s):  
Hybrid Zone ◽  
Zone Model ◽  
Hybrid Zones ◽  
Tension Zone ◽  
Zone Formation ◽  
Zone Width ◽  
Random Dispersal ◽  
Animal Diversity ◽  
Starting Point ◽  
Incomplete Reproductive Isolation

AbstractHybrid zones occur as range boundaries for many animal taxa. One model for how hybrid zones form and are stabilized is the tension zone model. This model predicts that hybrid zones widths are determined by a a balance between random dispersal into hybrid zones and selection against hybrids, and it does not formally account for local ecological gradients. Given the model’s simplicity, it provides a useful starting point for examining variation in hybrid zone widths across animals. Here we examine whether random dispersal and a proxy for selection against hybrids (mtDNA distance) can explain variation in hybrid zone widths across 135 hybridizing taxon pairs. We show that dispersal explains >30% of hybrid zone width variation across animal diversity and that mtDNA distance explains little variation. Clade-specific analyses revealed idiosyncratic patterns. Dispersal and mtDNA distance predict hybrid zone widths especially well in reptiles, while hybrid zone width scaled positively with mtDNA distance in birds, opposite predictions. Lastly, the data suggest that lower bounds on hybrid zone widths may be set by dispersal and the extent of molecular divergence, suggesting that hybrid zones are unlikely to form in restricted geographic spaces in highly dispersive and/or recently diverged taxa. Overall, our analyses reinforce the fundamental importance of dispersal in hybrid zone formation, and more generally in the ecology of range boundaries.

scholarly journals Climate-mediated hybrid zone movement revealed with genomics, museum collection, and simulation modeling

2018 ◽  
Vol 115 (10) ◽  
pp. E2284-E2291 ◽  
Author(s):  
Sean F. Ryan ◽  
Jillian M. Deines ◽  
J. Mark Scriber ◽  
Michael E. Pfrender ◽  
Stuart E. Jones ◽  
...  
Keyword(s):  
Genetic Diversity ◽  
Hybrid Zone ◽  
Zone Model ◽  
Hybrid Zones ◽  
Papilio Glaucus ◽  
Evolutionary Trajectory ◽  
Developmental Threshold ◽  
Papilio Canadensis ◽  
Nonlinear Responses ◽  
Conservation And Management

Climate-mediated changes in hybridization will dramatically alter the genetic diversity, adaptive capacity, and evolutionary trajectory of interbreeding species. Our ability to predict the consequences of such changes will be key to future conservation and management decisions. Here we tested through simulations how recent warming (over the course of a 32-y period) is affecting the geographic extent of a climate-mediated developmental threshold implicated in maintaining a butterfly hybrid zone (Papilio glaucus and Papilio canadensis; Lepidoptera: Papilionidae). These simulations predict a 68-km shift of this hybrid zone. To empirically test this prediction, we assessed genetic and phenotypic changes using contemporary and museum collections and document a 40-km northward shift of this hybrid zone. Interactions between the two species appear relatively unchanged during hybrid zone movement. We found no change in the frequency of hybridization, and regions of the genome that experience little to no introgression moved largely in concert with the shifting hybrid zone. Model predictions based on climate scenarios predict this hybrid zone will continue to move northward, but with substantial spatial heterogeneity in the velocity (55–144 km/1 °C), shape, and contiguity of movement. Our findings suggest that the presence of nonclimatic barriers (e.g., genetic incompatibilities) and/or nonlinear responses to climatic gradients may preserve species boundaries as the species shift. Further, we show that variation in the geography of hybrid zone movement could result in evolutionary responses that differ for geographically distinct populations spanning hybrid zones, and thus have implications for the conservation and management of genetic diversity.

scholarly journals Quantitative Correlation and Control Strategy for Element Content Fluctuation along Casting Direction in Central Area of Continuous Casting Billet

Metals ◽  
2021 ◽  
Vol 11 (3) ◽  
pp. 452
Author(s):  
Dongwei Guo ◽  
Zibing Hou ◽  
Zhiqiang Peng ◽  
Qian Liu ◽  
Jianghai Cao
Keyword(s):  
Control Strategy ◽  
Central Area ◽  
Solidification Structure ◽  
Equiaxed Crystal ◽  
Correlation Relationship ◽  
Zone Formation ◽  
Zone Width ◽  
Quantitative Correlation ◽  
Central Segregation ◽  
And Control

The statistical correlation was applied to analyze the specific and quantitative correlation relationship between the solidification structure and central segregation along the casting direction in carbon steel billet. On this basis, the segregation formation mechanism of the solute element and related control strategy were investigated. It is found that the equiaxed crystal zone fluctuation along the casting direction determines the fluctuation degree of central segregation. At the same time, the central segregation at a certain position is mostly affected by the equiaxed crystal zone width at the hysteretic position. Moreover, the casting speed can influence the columnar to equiaxed transition (CET) fluctuation along the casting direction by affecting the flow of molten steel in the billet. Overall, the segregation mechanism of solute elements along the casting direction can be summarized into two aspects: First, with the growth of columnar crystals in the initial stage, the segregated solutes are continuously enriched and distributed in the equiaxed crystal zone after CET. The fluctuation of the equiaxed crystal zone will affect the distribution of the enriched solute in the billet and cause the fluctuation of the central segregation. Second, due to the solidification shrinkage at the end of solidification, the solute-enriched liquid phase at the hysteretic position is pumped to the solidification endpoint and forms the central V-shaped segregation. Meanwhile, the stable solidification structure (columnar crystal length or equiaxed crystal zone width) along the casting direction and control measures preceded equiaxed crystal zone formation are beneficial to reduce the central V-shaped segregation.

scholarly journals Influence of Niche Overlap and Territoriality on Hybridization Between Hermit Warblers and Townsend's Warblers

The Auk ◽  
2000 ◽  
Vol 117 (1) ◽  
pp. 175-183 ◽  
Author(s):  
Scott F. Pearson ◽  
David A. Manuwal
Keyword(s):  
Habitat Use ◽  
Hybrid Zone ◽  
Parental Species ◽  
Niche Overlap ◽  
Habitat Characteristics ◽  
Hybrid Zones ◽  
Parental Fitness ◽  
Habitat Transition ◽  
Habitat Variables ◽  
Washington Cascades

Abstract Hybrid zones between Townsend's Warblers (Dendroica townsendi) and Hermit Warblers (D. occidentalis) in the Pacific Northwest are narrow relative to estimated dispersal distances and appear to be moving, with Townsend's replacing Hermits. We examined whether the habitat-transition and parental-fitness asymmetry models can explain why these zones are narrow and moving by comparing habitat variables associated with warbler territories in the Washington Cascades hybrid zone. Habitat variables did not differ among phenotypes, suggesting that the habitat-transition model cannot explain the narrow and dynamic nature of this hybrid zone. Habitat characteristics of Hermit Warbler territories did not differ inside versus outside the hybrid zone, also suggesting that this zone is not associated with a region of habitat transition. The lack of difference in habitat use could be the result of comparing variables that are not important to pairing success. However, warblers tended to select territories on west-southwest aspects. South aspects in the southern Washington Cascades are dominated by Douglas fir (Pseudotsuga menziesii) and true fir, which is a habitat selected by female warblers when choosing among territories and males. The parental-fitness asymmetry model does not necessarily make predictions about habitat use within the hybrid zone but predicts the superiority of one parental species over the other. However, if significant overlap occurs in habitat use or niche (as in these warblers), then competition between parental species is likely to occur. To determine whether these species compete, we mapped 12 warbler territories and monitored an additional 94 territories throughout the breeding season and found that all males with neighbors compete for and hold exclusive territories. Thus, the pattern of habitat use and territoriality is consistent with the parental-fitness asymmetry model.

scholarly journals Analyses of Hybrid Viability across a Hybrid Zone between Two Alnus Species Using Microsatellites and cpDNA Markers

Genes ◽  
2020 ◽  
Vol 11 (7) ◽  
pp. 770
Author(s):  
Jan Šmíd ◽  
Jan Douda ◽  
Karol Krak ◽  
Bohumil Mandák
Keyword(s):  
Hybrid Zone ◽  
Haplotype Diversity ◽  
Alnus Glutinosa ◽  
Zone Model ◽  
Triploid Hybrid ◽  
Genetic Lineages ◽  
Cpdna Markers ◽  
Spatial Positioning ◽  
Germination Experiment

Diploid Alnus glutinosa s. str. and autotetraploid A. rohlenae form a narrow hybrid zone in a study area in southern Serbia, which results in triploid hybrid formation. The vast majority of previous studies have been focused on studies of maternal plants, but the offspring resulting from their crossing have not been much studied. Here, we use the variability of microsatellites and chloroplast DNA between these species and their putative hybrids to create an overall picture of the development of the hybrid zone and its predicted type. To elucidate the gene transfer within both species, the origins of individual ploidies and especially the role of triploid hybrids, a germination experiment was carried out linked with a flow cytometry study of the resulting seedlings. The tension zone model seems to offer the most adequate explanation of our observations, with selection against triploid hybrids and the spatial positioning of the hybrid zone. Despite selection against them, the triploid hybrids play an important role in the exchange of genes between the two species and therefore serve as a bridge for introgression. The presence of fertile triploids is essential for enriching the haplotype diversity between these species and for the development of new genetic lineages.

scholarly journals Male territorial vocalizations and responses are decoupled in an avian hybrid zone

2008 ◽  
Vol 363 (1505) ◽  
pp. 2879-2889 ◽  
Author(s):  
Paula M den Hartog ◽  
Hans Slabbekoorn ◽  
Carel ten Cate
Keyword(s):  
Hybrid Zone ◽  
Acoustic Signals ◽  
Hybrid Zones ◽  
Natural Hybrid ◽  
Individual Male ◽  
Individual Strategy ◽  
Intraspecific Communication ◽  
Selective Sensitivity ◽  
Species Specific ◽  
Male Signals

A core area of speciation research concerns the coevolution of species-specific signals and the selective sensitivity to such signals. Signals and responses to them should be tuned to each other, to be effective in intraspecific communication. Hybrid zones are ideal to study the presence of such ‘behavioural coupling’ and the mechanisms governing it, and this has rarely been done. Our study examines acoustic signals of males and their response to them in the context of territorial interactions in a natural hybrid zone between two dove species, Streptopelia vinacea and Streptopelia capicola . Male signals are important in hybrid zone dynamics as they are essential for territory establishment, which is crucial for successful reproduction. We tested whether the response of individual male hybrids is linked to how similar their own signal is to the playback signal. We did not find evidence for behavioural coupling. The combined evidence from the low level of response to hybrid and heterospecific signals outside the hybrid zone and a lack of coupling within the hybrid zone suggests that perceptual learning may explain our results. Learning to respond to locally abundant signals may be the best individual strategy and is likely to contribute to the maintenance of a hybrid zone.

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