scholarly journals Sympatric ecological divergence with coevolution of niche preference

2019 ◽  
Author(s):  
Pavel Payne ◽  
Jitka Polechová
Keyword(s):  
Genetic Variation ◽  
Gene Flow ◽  
Assortative Mating ◽  
Parameter Space ◽  
Sympatric Speciation ◽  
Secondary Contact ◽  
Disruptive Selection ◽  
Ecological Divergence ◽  
Trade Off ◽  
Speciation Process

AbstractReinforcement, the increase of assortative mating driven by selection against unfit hybrids, is conditional on pre-existing divergence. Yet, for ecological divergence to precede the evolution of assortment, strict symmetries between fitnesses in niches must hold, and/or there must be low gene flow between the nascent species. It has thus been argued that conditions favouring sympatric speciation are rarely met in nature. Indeed, we show that under disruptive selection, violating symmetries in niche sizes and increasing strength of the trade-off in selection between the niches quickly leads to loss of genetic variation, instead of evolution of specialists. The region of the parameter space where polymorphism is maintained further narrows with increasing number of loci encoding the diverging trait and the rate of recombination between them. Yet, evolvable assortment and pre-existing assortment both substantially broaden the parameter space within which polymorphism is maintained. Notably, pre-existing niche preference speeds up further increase of assortment, thus facilitating reinforcement in the later phases of speciation. We conclude that in order for sympatric ecological divergence to occur, niche preference must co-evolve throughout the divergence process. Even if populations come into secondary contact, having diverged in isolation, niche preference substantially broadens the conditions for coexistence in sympatry and completion of the speciation process.

scholarly journals Sympatric ecological divergence with coevolution of niche preference

2020 ◽  
Vol 375 (1806) ◽  
pp. 20190749 ◽  
Author(s):  
Pavel Payne ◽  
Jitka Polechová
Keyword(s):  
Genetic Variation ◽  
Gene Flow ◽  
Reproductive Isolation ◽  
Parameter Space ◽  
Sympatric Speciation ◽  
Secondary Contact ◽  
Disruptive Selection ◽  
Theme Issue ◽  
Ecological Divergence ◽  
Trade Off

Reinforcement, the increase of assortative mating driven by selection against unfit hybrids, is conditional on pre-existing divergence. Yet, for ecological divergence to precede the evolution of assortment, strict symmetries between fitnesses in niches must hold, and/or there must be low gene flow between the nascent species. It has thus been argued that conditions favouring sympatric speciation are rarely met in nature. Indeed, we show that under disruptive selection, violating symmetries in niche sizes and increasing strength of the trade-off in selection between the niches quickly leads to loss of genetic variation, instead of evolution of specialists. The region of the parameter space where polymorphism is maintained further narrows with increasing number of loci encoding the diverging trait and the rate of recombination between them. Yet, evolvable assortment and pre-existing assortment both substantially broaden the parameter space within which polymorphism is maintained. Notably, pre-existing niche preference speeds up further increase of assortment, thus facilitating reinforcement in the later phases of speciation. We conclude that in order for sympatric ecological divergence to occur, niche preference must coevolve throughout the divergence process. Even if populations come into secondary contact, having diverged in isolation, niche preference substantially broadens the conditions for coexistence in sympatry and completion of the speciation process. This article is part of the theme issue ‘Towards the completion of speciation: the evolution of reproductive isolation beyond the first barriers'.

scholarly journals Sympatric Speciation in Threespine Stickleback: Why Not?

2011 ◽  
Vol 2011 ◽  
pp. 1-15 ◽  
Author(s):  
Daniel I. Bolnick
Keyword(s):  
Sexual Dimorphism ◽  
Assortative Mating ◽  
Intraspecific Competition ◽  
Gasterosteus Aculeatus ◽  
Theoretical Models ◽  
Sympatric Speciation ◽  
Threespine Stickleback ◽  
Disruptive Selection ◽  
Evolutionary Diversification ◽  
Trait Variance

Numerous theoretical models suggest that sympatric speciation is possible when frequency-dependent interactions such as intraspecific competition drive disruptive selection on a trait that is also subject to assortative mating. Here, I review recent evidence that both conditions are met in lake populations of threespine stickleback (Gasterosteus aculeatus). Nonetheless, sympatric speciation appears to be rare or absent in stickleback. If stickleback qualitatively fit the theoretical requirements for sympatric speciation, why do they not undergo sympatric speciation? I present simulations showing that disruptive selection and assortative mating in stickleback, though present, are too weak to drive speciation. Furthermore, I summarize empirical evidence that disruptive selection in stickleback drives other forms of evolutionary diversification (plasticity, increased trait variance, and sexual dimorphism) instead of speciation. In conclusion, core assumptions of sympatric speciation theory seem to be qualitatively reasonable for stickleback, but speciation may nevertheless fail because of (i) quantitative mismatches with theory and (ii) alternative evolutionary outcomes.

scholarly journals What role does natural selection play in speciation?

2010 ◽  
Vol 365 (1547) ◽  
pp. 1825-1840 ◽  
Author(s):  
N. H. Barton
Keyword(s):  
Gene Flow ◽  
Habitat Preference ◽  
Genetic Variance ◽  
Bimodal Distribution ◽  
Biological Species ◽  
Disruptive Selection ◽  
Linkage Equilibrium ◽  
Sexual Population ◽  
Trade Off ◽  
High Gene

If distinct biological species are to coexist in sympatry, they must be reproductively isolated and must exploit different limiting resources. A two-niche Levene model is analysed, in which habitat preference and survival depend on underlying additive traits. The population genetics of preference and viability are equivalent. However, there is a linear trade-off between the chances of settling in either niche, whereas viabilities may be constrained arbitrarily. With a convex trade-off, a sexual population evolves a single generalist genotype, whereas with a concave trade-off, disruptive selection favours maximal variance. A pure habitat preference evolves to global linkage equilibrium if mating occurs in a single pool, but remarkably, evolves to pairwise linkage equilibrium within niches if mating is within those niches—independent of the genetics. With a concave trade-off, the population shifts sharply between a unimodal distribution with high gene flow and a bimodal distribution with strong isolation, as the underlying genetic variance increases. However, these alternative states are only simultaneously stable for a narrow parameter range. A sharp threshold is only seen if survival in the ‘wrong’ niche is low; otherwise, strong isolation is impossible. Gene flow from divergent demes makes speciation much easier in parapatry than in sympatry.

scholarly journals Genomic signatures of sympatric speciation with historical and contemporary gene flow in a tropical anthozoan

2018 ◽  
Author(s):  
Benjamin M. Titus ◽  
Paul D. Blischak ◽  
Marymegan Daly
Keyword(s):  
Gene Flow ◽  
Cryptic Species ◽  
Species Complex ◽  
Sympatric Speciation ◽  
Sea Anemone ◽  
Secondary Contact ◽  
Marine Habitats ◽  
Contemporary Gene Flow ◽  
Cryptic Species Complex ◽  
Tropical Sea

AbstractSympatric diversification is increasingly thought to have played an important role in the evolution of biodiversity around the globe. However, an in situ sympatric origin for co-distributed taxa is difficult to demonstrate empirically because different evolutionary processes can lead to similar biogeographic outcomes-especially in ecosystems with few hard barriers to dispersal that can facilitate allopatric speciation followed by secondary contact (e.g. marine habitats). Here we use a genomic (ddRADseq), model-based approach to delimit a cryptic species complex of tropical sea anemones that are co-distributed on coral reefs throughout the Tropical Western Atlantic. We use coalescent simulations in fastsimcoal2 to test competing diversification scenarios that span the allopatric-sympatric continuum. We recover support that the corkscrew sea anemone Bartholomea annulata (Le Sueur, 1817) is a cryptic species complex, co-distributed throughout its range. Simulation and model selection analyses suggest these lineages arose in the face of historical and contemporary gene flow, supporting a sympatric origin, but an alternative secondary contact model also receives appreciable model support. Leveraging the genome of Exaiptasia pallida we identify five loci under divergent selection between cryptic B. annulata lineages that fall within mRNA transcripts or CDS regions. Our study provides a rare empirical, genomic example of sympatric speciation in a tropical anthozoan-a group that includes reef-building corals. Finally, these data represent the first range-wide molecular study of any tropical sea anemone, underscoring that anemone diversity is under described in the tropics, and highlighting the need for additional systematic studies into these ecologically and economically important species.

scholarly journals Colour pattern as a single trait driving speciation in Hypoplectrus coral reef fishes?

2007 ◽  
Vol 274 (1615) ◽  
pp. 1265-1271 ◽  
Author(s):  
Oscar Puebla ◽  
Eldredge Bermingham ◽  
Frédéric Guichard ◽  
Elizabeth Whiteman
Keyword(s):  
Gene Flow ◽  
Coral Reef ◽  
Assortative Mating ◽  
Reef Fishes ◽  
Coral Reef Fishes ◽  
Colour Pattern ◽  
Disruptive Selection ◽  
Reef Fish Species ◽  
Colour Patterns ◽  
Colour Morphs

Theory shows that speciation in the presence of gene flow occurs only under narrow conditions. One of the most favourable scenarios for speciation with gene flow is established when a single trait is both under disruptive natural selection and used to cue assortative mating. Here, we demonstrate the potential for a single trait, colour pattern, to drive incipient speciation in the genus Hypoplectrus (Serranidae), coral reef fishes known for their striking colour polymorphism. We provide data demonstrating that sympatric Hypoplectrus colour morphs mate assortatively and are genetically distinct. Furthermore, we identify ecological conditions conducive to disruptive selection on colour pattern by presenting behavioural evidence of aggressive mimicry, whereby predatory Hypoplectrus colour morphs mimic the colour patterns of non-predatory reef fish species to increase their success approaching and attacking prey. We propose that colour-based assortative mating, combined with disruptive selection on colour pattern, is driving speciation in Hypoplectrus coral reef fishes.

scholarly journals Measure of Similarity between GMMs by Embedding of the Parameter Space That Preserves KL Divergence

Mathematics ◽  
2021 ◽  
Vol 9 (9) ◽  
pp. 957
Author(s):  
Branislav Popović ◽  
Lenka Cepova ◽  
Robert Cep ◽  
Marko Janev ◽  
Lidija Krstanović
Keyword(s):  
Computational Complexity ◽  
Parameter Space ◽  
Recognition Accuracy ◽  
Gaussian Mixture Models ◽  
Gaussian Mixture ◽  
Dimensional Manifold ◽  
Dimensional Parameter ◽  
Trade Off ◽  
Measure Of Similarity ◽  
Lower Dimensional

In this work, we deliver a novel measure of similarity between Gaussian mixture models (GMMs) by neighborhood preserving embedding (NPE) of the parameter space, that projects components of GMMs, which by our assumption lie close to lower dimensional manifold. By doing so, we obtain a transformation from the original high-dimensional parameter space, into a much lower-dimensional resulting parameter space. Therefore, resolving the distance between two GMMs is reduced to (taking the account of the corresponding weights) calculating the distance between sets of lower-dimensional Euclidean vectors. Much better trade-off between the recognition accuracy and the computational complexity is achieved in comparison to measures utilizing distances between Gaussian components evaluated in the original parameter space. The proposed measure is much more efficient in machine learning tasks that operate on large data sets, as in such tasks, the required number of overall Gaussian components is always large. Artificial, as well as real-world experiments are conducted, showing much better trade-off between recognition accuracy and computational complexity of the proposed measure, in comparison to all baseline measures of similarity between GMMs tested in this paper.

scholarly journals Parasite variation and the evolution of virulence in a Daphnia-microparasite system

Parasitology ◽  
2007 ◽  
Vol 135 (3) ◽  
pp. 303-308 ◽  
Author(s):  
T. J. LITTLE ◽  
W. CHADWICK ◽  
K. WATT
Keyword(s):  
Genetic Variation ◽  
Rank Order ◽  
Genetic Relationships ◽  
Natural Populations ◽  
Host Genotype ◽  
Relative Growth ◽  
Trade Off ◽  
Relative Growth Rates ◽  
Pasteuria Ramosa ◽  
Evolution Of Virulence

SUMMARYUnderstanding genetic relationships amongst the life-history traits of parasites is crucial for testing hypotheses on the evolution of virulence. This study therefore examined variation between parasite isolates (the bacterium Pasteuria ramosa) from the crustacean Daphnia magna. From a single wild-caught infected host we obtained 2 P. ramosa isolates that differed substantially in the mortality they caused. Surprisingly, the isolate causing higher early mortality was, on average, less successful at establishing infections and had a slower growth rate within hosts. The observation that within-host replication rate was negatively correlated with mortality could violate a central assumption of the trade-off hypothesis for the evolution of virulence, but we discuss a number of caveats which caution against premature rejection of the trade-off hypothesis. We sought to test if the characteristics of these parasite isolates were constant across host genotypes in a second experiment that included 2 Daphnia host clones. The relative growth rates of the two parasite isolates did indeed depend on the host genotype (although the rank order did not change). We suggest that testing evolutionary hypotheses for virulence may require substantial sampling of both host and parasite genetic variation, and discuss how selection for virulence may change with the epidemiological state of natural populations and how this can promote genetic variation for virulence.

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