Allozyme Polymorphisms in the Small Heath,Coenonympha pamphilus: Recent Ecological Selection or Old Biogeographical Signal?

2008 ◽  
Vol 45 (3) ◽  
pp. 217-228 ◽  
Author(s):  
Joachim Besold ◽  
Stefan Huck ◽  
Thomas Schmitt
Keyword(s):  
Ecological Selection ◽  
Allozyme Polymorphisms ◽  
Coenonympha Pamphilus

scholarly journals Mating System and Hybridity in Eucalyptus pauciflora

1977 ◽  
Vol 30 (4) ◽  
pp. 337 ◽  
Author(s):  
MA Phillips ◽  
AHD Brown
Keyword(s):  
Mating System ◽  
Outcrossing Rate ◽  
Seedling Stage ◽  
Average Heterozygosity ◽  
Evolutionary Advantage ◽  
Allozyme Polymorphisms ◽  
Self Fertilization

Allozyme polymorphisms at four loci expressed in seeds, and three other loci expressed in seedlings, were used to determine the outcrossing rate in three natural subalpine populations of snow gum (E. paucijlora). Based on the seed loci data, an estimated 37 % of seed was derived from self-fertilization and 63 % from random outcrossing. In the most elevated population the estimate after germination was similar. However, at lower elevations the frequency of effective self-fertilization estimated at the seedling stage was only 16 %. The less elevated populations also showed a greater average heterozygosity and a larger increase in heterozygosity in the adult over the progeny stages. Heterosis apparently operated differentially in these populations-it was more intense at the lower altitudes. Selection in favour of outcrossed individuals may be an important factor in checking the spread through the population of genes which promote self-fertilization, and which would otherwise enjoy an evolutionary advantage.

scholarly journals Ecological divergence in sympatry causes gene misregulation in hybrids

2019 ◽  
Author(s):  
Joseph A. McGirr ◽  
Christopher H. Martin
Keyword(s):  
Gene Expression ◽  
Reproductive Isolation ◽  
Differentially Expressed ◽  
F1 Hybrids ◽  
Adaptive Divergence ◽  
Lower Hybrid ◽  
Hybrid Fitness ◽  
Hybrid Gene ◽  
San Salvador ◽  
Ecological Selection

AbstractEcological speciation occurs when reproductive isolation evolves as a byproduct of adaptive divergence between populations. However, it is unknown whether divergent ecological selection on gene regulation can directly cause reproductive isolation. Selection favoring regulatory divergence between species could result in gene misregulation in F1 hybrids and ultimately lower hybrid fitness. We combined 58 resequenced genomes with 124 transcriptomes to test this hypothesis in a young, sympatric radiation of Cyprinodon pupfishes endemic to San Salvador Island, Bahamas, which consists of a dietary generalist and two novel trophic specialists – a molluscivore and a scale-eater. We found more differential gene expression between closely related sympatric specialists than between allopatric generalist populations separated by 1000 km. Intriguingly, 9.6% of genes that were differentially expressed between sympatric species were also misregulated in their F1 hybrids. Consistent with divergent ecological selection causing misregulation, a subset of these genes were in highly differentiated genomic regions and enriched for functions important for trophic specialization, including head, muscle, and brain development. These regions also included genes that showed evidence of hard selective sweeps and were significantly associated with oral jaw length – the most rapidly diversifying skeletal trait in this radiation. Our results indicate that divergent ecological selection in sympatry can cause hybrid gene misregulation which may act as a primary reproductive barrier between nascent species.SignificanceIt is unknown whether the same genes that regulate ecological traits can simultaneously contribute to reproductive barriers between species. We measured gene expression in two trophic specialist species of Cyprinodon pupfishes that rapidly diverged from a generalist ancestor. We found genes differentially expressed between species that also showed extreme expression levels in their hybrid offspring. Many of these genes showed signs of selection and have putative effects on the development of traits that are important for ecological specialization. This suggests that genetic variants contributing to adaptive trait divergence between parental species negatively interact to cause hybrid gene misregulation, potentially producing unfit hybrids. Such loci may be important barriers to gene flow during the early stages of speciation, even in sympatry.

scholarly journals Parallel evolution and ecological selection: replicated character displacement in spadefoot toads

2009 ◽  
Vol 276 (1676) ◽  
pp. 4189-4196 ◽  
Author(s):  
Amber M. Rice ◽  
Aaron R. Leichty ◽  
David W. Pfennig
Keyword(s):  
Resource Competition ◽  
Parallel Evolution ◽  
Character Displacement ◽  
Population History ◽  
Ancestral Population ◽  
Sympatric Populations ◽  
Trait Evolution ◽  
Ecological Selection ◽  
Spadefoot Toads ◽  
Repeated Evolution

Ecological character displacement—trait evolution stemming from selection to lessen resource competition between species—is most often inferred from a pattern in which species differ in resource-use traits in sympatry but not in allopatry, and in which sympatric populations within each species differ from conspecific allopatric populations. Yet, without information on population history, the presence of a divergent phenotype in multiple sympatric populations does not necessarily imply that there has been repeated evolution of character displacement. Instead, such a pattern may arise if there has been character displacement in a single ancestral population, followed by gene flow carrying the divergent phenotype into multiple, derived, sympatric populations. Here, we evaluate the likelihood of such historical events versus ongoing ecological selection in generating divergence in trophic morphology between multiple populations of spadefoot toad ( Spea multiplicata ) tadpoles that are in sympatry with a heterospecific and those that are in allopatry. We present both phylogenetic and population genetic evidence indicating that the same divergent trait, which minimizes resource competition with the heterospecific, has arisen independently in multiple sympatric populations. These data, therefore, provide strong indirect support for competition's role in divergent trait evolution.

scholarly journals Transspecies beak color polymorphism in the Darwin’s finch radiation

2021 ◽  
Author(s):  
Erik D. Enbody ◽  
C. Grace Sprehn ◽  
Arhat Abzhanov ◽  
Huijuan Bi ◽  
Mariya P. Dobreva ◽  
...  
Keyword(s):  
Molecular Genetic ◽  
Introgressive Hybridization ◽  
Color Polymorphism ◽  
Regulatory Mutation ◽  
Genetic Investigation ◽  
Interspecific Introgression ◽  
Evolutionary Diversification ◽  
Ecological Selection ◽  
Balanced Polymorphism ◽  
As Species

AbstractCarotenoid-based polymorphisms are widespread in populations of birds, fish, and reptiles1, but little is known of how they affect fitness and are maintained as species multiply2. We report a combined field and molecular-genetic investigation of a nestling beak color polymorphism in Darwin’s finches. Beaks are pink or yellow, and yellow is recessive3. Here we show that the polymorphism arose in the Galápagos approximately half a million years ago through a regulatory mutation in the BCO2 gene, and is shared by 14 descendant species. The frequency of the yellow genotype is associated with cactus flower abundance in cactus finches, and is altered by introgressive hybridization. The polymorphism is most likely a balanced polymorphism, maintained by ecological selection pressures associated with diet, and augmented by occasional interspecific introgression. Polymorphisms that are hidden as adults, as here, may contribute to evolutionary diversification in underappreciated ways in other systems.

Sexual and ecological selection on a sexual conflict gene

2020 ◽  
Vol 33 (10) ◽  
pp. 1433-1439
Author(s):  
Agata Plesnar‐Bielak ◽  
Anna M. Skwierzyńska ◽  
Jacek Radwan
Keyword(s):  
Sexual Conflict ◽  
Ecological Selection

scholarly journals Ecological selection pressures for C 4 photosynthesis in the grasses

2009 ◽  
Vol 276 (1663) ◽  
pp. 1753-1760 ◽  
Author(s):  
Colin P. Osborne ◽  
Robert P. Freckleton
Keyword(s):  
Comparative Method ◽  
High Irradiance ◽  
Evolutionary Transitions ◽  
Evolutionary Selection ◽  
Evolutionary Origins ◽  
Ecological Selection ◽  
Arid Conditions ◽  
Ecological Association ◽  
Saline Habitats ◽  
Use Efficiency

Grasses using the C 4 photosynthetic pathway dominate grasslands and savannahs of warm regions, and account for half of the species in this ecologically and economically important plant family. The C 4 pathway increases the potential for high rates of photosynthesis, particularly at high irradiance, and raises water-use efficiency compared with the C 3 type. It is therefore classically viewed as an adaptation to open, arid conditions. Here, we test this adaptive hypothesis using the comparative method, analysing habitat data for 117 genera of grasses, representing 15 C 4 lineages. The evidence from our three complementary analyses is consistent with the hypothesis that evolutionary selection for C 4 photosynthesis requires open environments, but we find an equal likelihood of C 4 evolutionary origins in mesic, arid and saline habitats. However, once the pathway has arisen, evolutionary transitions into arid habitats occur at higher rates in C 4 than C 3 clades. Extant C 4 genera therefore occupy a wider range of drier habitats than their C 3 counterparts because the C 4 pathway represents a pre-adaptation to arid conditions. Our analyses warn against evolutionary inferences based solely upon the high occurrence of extant C 4 species in dry habitats, and provide a novel interpretation of this classic ecological association.

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