scholarly journals Primary hybrid zone formation in Tephroseris helenitis (Asteraceae), following postglacial range expansion along the central Northern Alps

2021 ◽  
Vol 30 (7) ◽  
pp. 1704-1720
Author(s):  
Georg Pflugbeil ◽  
Matthias Affenzeller ◽  
Andreas Tribsch ◽  
Hans Peter Comes
Keyword(s):  
Hybrid Zone ◽  
Range Expansion ◽  
Zone Formation ◽  
Northern Alps

scholarly journals Hybrid zone formation and contrasting outcomes of secondary contact over transects in common toads

2017 ◽  
Vol 26 (20) ◽  
pp. 5663-5675 ◽  
Author(s):  
Jan W. Arntzen ◽  
Wouter de Vries ◽  
Daniele Canestrelli ◽  
Iñigo Martínez-Solano
Keyword(s):  
Hybrid Zone ◽  
Secondary Contact ◽  
Zone Formation

A hybrid zone defined by allozymes and ventral colour in Geocrinia rosea (Anura:Myobatrachidae)

2007 ◽  
Vol 55 (6) ◽  
pp. 371 ◽  
Author(s):  
Don A. Driscoll ◽  
J. Dale Roberts
Keyword(s):  
Hybrid Zone ◽  
Range Expansion ◽  
Taxonomic Revision ◽  
Hybrid Population ◽  
Genetic Groups ◽  
Colour Patterns ◽  
Allozyme Loci ◽  
Two Populations ◽  
Genetic Division

The frog Geocrinia rosea is highly genetically subdivided with a major genetic division between northern and southern populations. Previous research did not sample a region spanning 12 km between these two populations. We report the distribution of G. rosea in the unsampled area and identify a geographically restricted hybrid zone. Boundaries of genetic groups were defined using two allozyme loci in 13 populations and ventral colouration. G. rosea was not continuously distributed in the area of parapatry. At the only point where the northern and southern groups met, there was a single hybrid population with genotypes demonstrating substantial interbreeding. Colour patterns implied a slightly broader hybrid zone, with four populations showing ventral colour introgression. Northern populations tended to have pink bellies whereas southern populations generally had orange bellies. We conclude that the two groups have diverged in allopatry and have formed a very narrow hybrid zone after range expansion. The magnitude of allozyme divergence between the four currently recognised species in the G. rosea complex is similar to the divergence between northern and southern G. rosea and is much greater than the divergence between other intraspecific groups. Taxonomic revision may therefore be warranted.

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.

Distortion of symmetrical introgression in a hybrid zone: evidence for locus-specific selection and uni-directional range expansion

2006 ◽  
Vol 19 (3) ◽  
pp. 705-716 ◽  
Author(s):  
J. JOHANNESEN ◽  
B. JOHANNESEN ◽  
E. M. GRIEBELER ◽  
I. BARAN ◽  
M. R. TUNC ◽  
...  
Keyword(s):  
Hybrid Zone ◽  
Range Expansion

Comparisons among morphological characters and between localities in the Chorthippus parallelus hybrid zone (Orthoptera: Acrididae)

1991 ◽  
Vol 334 (1271) ◽  
pp. 297-308 ◽  
Keyword(s):  
Population Structure ◽  
Gene Flow ◽  
Morphological Change ◽  
Hybrid Zone ◽  
Range Expansion ◽  
Morphological Characters ◽  
Patchy Distribution ◽  
Chorthippus Parallelus ◽  
Last Glaciation ◽  
Common Observation

Two subspecies of the grasshopper, Chorthippus parallelus , meet and hybridize in the Pyrenees. The hybrid zone between the two taxa is believed to have formed following range expansion at the end of the last glaciation and to be maintained by a balance between gene flow and selection against hybrids. Laboratory FI hybrid males are sterile. We have examined morphological characters in two cols about 200 km apart and compared the positions and widths of dines for these characters both within and between cols. Clines are neither coincident (centred in the same position), nor concordant (equal in width) in either col. Furthermore clines are wider and more dispersed in the western col. The lack of concordance can be explained on several models for the maintenance of the hybrid zone and is a common observation. There are many fewer examples of lack of coincidence and this result is more difficult to interpret. We suggest that it is due to a difference in population structure between the cols: a patchy distribution of grasshoppers in the western col produces wider, more dispersed dines while a sharp break in distribution in the eastern col tends to concentrate morphological change over a shorter distance.

Precipitation in Al-Li-Cu Alloys

1981 ◽  
Vol 39 ◽  
pp. 44-45
Author(s):  
J. E. O'Neal ◽  
K. K. Sankaran
Keyword(s):  
Electron Microscopy ◽  
Age Hardening ◽  
Precipitation Behavior ◽  
Zone Formation ◽  
Specific Strength ◽  
Hardening Behavior ◽  
Cu Alloys ◽  
High Specific Strength ◽  
Transmission Electron ◽  
Structural Applications

Al-Li-Cu alloys combine high specific strength and high specific modulus and are potential candidates for aircraft structural applications. As part of an effort to optimize Al-Li-Cu alloys for specific applications, precipitation in these alloys was studied for a range of compositions, and the mechanical behavior was correlated with the microstructures.Alloys with nominal compositions of Al-4Cu-2Li-0.2Zr, Al-2.5Cu-2.5Li-0.2Zr, and Al-l.5Cu-2.5Li-0.5Mn were argon-atomized into powder at solidification rates ≈ 103°C/s. Powders were consolidated into bar stock by vacuum pressing and extruding at 400°C. Alloy specimens were solution annealed at 530°C and aged at temperatures up to 250°C, and the resultant precipitation was studied by transmission electron microscopy (TEM).The low-temperature (≲100°C) precipitation behavior of the Al-4Cu-2Li-0.2Zr alloy is a combination of the separate precipitation behaviors of Al-Cu and Al-Li alloys. The age-hardening behavior at these temperatures is characteristic of Guinier-Preston (GP) zone formation, with additional strengthening resulting from the coherent precipitation of δ’ (Al3Li, Ll2 structure), the presence of which is revealed by the selected-area diffraction pattern (SADP) shown in Figure la.

RELATIVE ABUNDANCE AND THE SPECIES-SPECIFIC REINFORCEMENT OF MALE MATING PREFERENCE IN THE CHRYSOCHUS (COLEOPTERA: CHRYSOMELIDAE) HYBRID ZONE

Evolution ◽  
2005 ◽  
Vol 59 (12) ◽  
pp. 2639 ◽  
Author(s):  
Merrill A. Peterson ◽  
Barbara M. Honchak ◽  
Stefanie E. Locke ◽  
Timothy E. Beeman ◽  
Jessica Mendoza ◽  
...  
Keyword(s):  
Relative Abundance ◽  
Hybrid Zone ◽  
Mating Preference ◽  
Male Mating ◽  
Species Specific
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