scholarly journals The evolution of reproductive isolation in Daphnia

2019 ◽  
Vol 19 (1) ◽  
Author(s):  
Tiffany A. Chin ◽  
Carla E. Cáceres ◽  
Melania E. Cristescu
Keyword(s):  
Gene Flow ◽  
Reproductive Isolation ◽  
Daphnia Pulex ◽  
Early Stages ◽  
Relative Contribution ◽  
Prezygotic Barriers ◽  
Ecological Barriers ◽  
Species Formation ◽  
Complex Process ◽  
Postzygotic Reproductive Isolation

Abstract Background The process by which populations evolve to become new species involves the emergence of various reproductive isolating barriers (RIB). Despite major advancements in understanding this complex process, very little is known about the order in which RIBs evolve or their relative contribution to the total restriction of gene flow during various stages of speciation. This is mainly due to the difficulties of studying reproductive isolation during the early stages of species formation. This study examines ecological and non-ecological RIB within and between Daphnia pulex and Daphnia pulicaria, two recently diverged species that inhabit distinct habitats and exhibit an unusual level of intraspecific genetic subdivision. Results We find that while ecological prezygotic barriers are close to completion, none of the non-ecological barriers can restrict gene flow between D. pulex and D. pulicaria completely when acting alone. Surprisingly, we also identified high levels of postzygotic reproductive isolation in ‘conspecific’ interpopulation crosses of D. pulex. Conclusions While the ecological prezygotic barriers are prevalent during the mature stages of speciation, non-ecological barriers likely dominated the early stages of speciation. This finding indicates the importance of studying the very early stages of speciation and suggests the contribution of postzygotic isolation in initiating the process of speciation.

scholarly journals The limits to parapatric speciation 3: evolution of strong reproductive isolation in presence of gene flow despite limited ecological differentiation

2020 ◽  
Vol 375 (1806) ◽  
pp. 20190532 ◽  
Author(s):  
Alexandre Blanckaert ◽  
Claudia Bank ◽  
Joachim Hermisson
Keyword(s):  
Gene Flow ◽  
Reproductive Isolation ◽  
Local Adaptation ◽  
Theme Issue ◽  
Genetic Barrier ◽  
Incipient Species ◽  
Postzygotic Reproductive Isolation ◽  
Minimal Configuration ◽  
Parapatric Speciation ◽  
Two Populations

Gene flow tends to impede the accumulation of genetic divergence. Here, we determine the limits for the evolution of postzygotic reproductive isolation in a model of two populations that are connected by gene flow. We consider two selective mechanisms for the creation and maintenance of a genetic barrier: local adaptation leads to divergence among incipient species due to selection against migrants, and Dobzhansky–Muller incompatibilities (DMIs) reinforce the genetic barrier through selection against hybrids. In particular, we are interested in the maximum strength of the barrier under a limited amount of local adaptation, a challenge that many incipient species may initially face. We first confirm that with classical two-locus DMIs, the maximum amount of local adaptation is indeed a limit to the strength of a genetic barrier. However, with three or more loci and cryptic epistasis, this limit holds no longer. In particular, we identify a minimal configuration of three epistatically interacting mutations that is sufficient to confer strong reproductive isolation. This article is part of the theme issue ‘Towards the completion of speciation: the evolution of reproductive isolation beyond the first barriers’.

scholarly journals Extensive introgression despite Haldane’s rule: insights from grasshopper hybrid zones

2021 ◽  
Author(s):  
Linda Hagberg ◽  
Enrique Celemin ◽  
Iker Irisarri ◽  
Oliver Hawlitschek ◽  
J L Bella ◽  
...  
Keyword(s):  
Gene Flow ◽  
Reproductive Isolation ◽  
Male Sterility ◽  
Secondary Contact ◽  
Hybrid Zones ◽  
Hybrid Male ◽  
Hybrid Male Sterility ◽  
Haldane’S Rule ◽  
Haldane's Rule ◽  
Species Formation

Although the process of species formation is notoriously idiosyncratic, the observation of pervasive patterns of reproductive isolation across species pairs suggests that generalities, or “rules”, underlie species formation in all animals. Haldane’s rule states that whenever a sex is absent, rare or sterile in a cross between two taxa, that sex is usually the heterogametic sex. Yet, understanding how Haldane’s rule first evolves and whether it is associated to genome wide barriers to gene flow remains a challenging task because this rule is usually studied in highly divergent taxa that no longer hybridize in nature. Here, we address these questions using the meadow grasshopper Pseudochorthippus parallelus where populations that readily hybridize in two natural hybrid zones show hybrid male sterility in laboratorial crosses. Using mitochondrial data, we infer that such populations have diverged some 100,000 years ago, surviving multiple glacial periods in isolated Pleistocenic refugia. Nuclear data shows that secondary contact has led to extensive introgression throughout the species range, including between populations showing hybrid male sterility. We find repeatable patterns of genomic differentiation across the two hybrid zones, yet such patterns are consistent with shared genomic constraints across taxa rather than their role in reproductive isolation. Together, our results suggest that Haldane’s rule can evolve relatively quickly within species, particularly when associated to strong demographic changes. At such early stages of species formation, hybrid male sterility still permits extensive gene flow, allowing future studies to identify genomic regions associated with reproductive barriers.

scholarly journals The limits to parapatric speciation 3: Evolution of strong reproductive isolation in presence of gene flow despite limited ecological differentiation

2020 ◽  
Author(s):  
Alexandre Blanckaert ◽  
Claudia Bank ◽  
Joachim Hermisson
Keyword(s):  
Gene Flow ◽  
Reproductive Isolation ◽  
Local Adaptation ◽  
Maximum Amount ◽  
Genetic Barrier ◽  
Incipient Species ◽  
Postzygotic Reproductive Isolation ◽  
Minimal Configuration ◽  
Parapatric Speciation ◽  
Two Populations

AbstractGene flow tends to impede the accumulation of genetic divergence. Here, we determine the limits for the evolution of postzygotic reproductive isolation in a model of two populations that are connected by gene flow. We consider two selective mechanisms for the creation and maintenance of a genetic barrier: local adaptation leads to divergence among incipient species due to selection against migrants, and Dobzhansky-Muller incompatibilities (DMIs) reinforce the genetic barrier through selection against hybrids. In particular, we are interested in the maximum strength of the barrier under a limited amount of local adaptation, a challenge that may initially face many incipient species. We first confirm that with classical two-locus DMIs, the maximum amount of local adaptation is indeed a limit to the strength of a genetic barrier. However, with three or more loci and cryptic epistasis, this limit holds no longer. In particular, we identify a minimal configuration of three epistatically interacting mutations that is sufficient to confer strong reproductive isolation.

Introgression between non-sister species of honeyeaters (Aves: Meliphagidae) several million years after speciation

2019 ◽  
Vol 128 (3) ◽  
pp. 583-591
Author(s):  
Leo Joseph ◽  
Alex Drew ◽  
Ian J Mason ◽  
Jeffrey L Peters
Keyword(s):  
Gene Flow ◽  
Reproductive Isolation ◽  
Sex Chromosomes ◽  
Common Ancestor ◽  
Sister Species ◽  
Species Boundaries ◽  
North Eastern ◽  
The City

Abstract We reassessed whether two parapatric non-sister Australian honeyeater species (Aves: Meliphagidae), varied and mangrove honeyeaters (Gavicalis versicolor and G. fasciogularis, respectively), that diverged from a common ancestor c. 2.5 Mya intergrade in the Townsville area of north-eastern Queensland. Consistent with a previous specimen-based study, by using genomics methods we show one-way gene flow for autosomal but not Z-linked markers from varied into mangrove honeyeaters. Introgression barely extends south of the area of parapatry in and around the city of Townsville. While demonstrating the long-term porosity of species boundaries over several million years, our data also suggest a clear role of sex chromosomes in maintaining reproductive isolation.

scholarly journals How Can Satellite DNA Divergence Cause Reproductive Isolation? Let Us Count the Chromosomal Ways

2012 ◽  
Vol 2012 ◽  
pp. 1-11 ◽  
Author(s):  
Patrick M. Ferree ◽  
Satyaki Prasad
Keyword(s):  
Reproductive Isolation ◽  
Developmental Stages ◽  
Rapid Evolution ◽  
Model Organisms ◽  
Cellular Mechanisms ◽  
Closely Related Species ◽  
Heterochromatin Formation ◽  
Interspecies Hybrids ◽  
Postzygotic Reproductive Isolation ◽  
And Function

Satellites are one of the most enigmatic parts of the eukaryotic genome. These highly repetitive, noncoding sequences make up as much as half or more of the genomic content and are known to play essential roles in chromosome segregation during meiosis and mitosis, yet they evolve rapidly between closely related species. Research over the last several decades has revealed that satellite divergence can serve as a formidable reproductive barrier between sibling species. Here we highlight several key studies on Drosophila and other model organisms demonstrating deleterious effects of satellites and their rapid evolution on the structure and function of chromosomes in interspecies hybrids. These studies demonstrate that satellites can impact chromosomes at a number of different developmental stages and through distinct cellular mechanisms, including heterochromatin formation. These findings have important implications for how loci that cause postzygotic reproductive isolation are viewed.

scholarly journals Genome-Wide Regulatory Interactions in the Early Stages of Drosophila Speciation

2020 ◽  
Author(s):  
◽  
Alwyn Clark Go
Keyword(s):  
Reproductive Isolation ◽  
Expression Analysis ◽  
Regulatory Elements ◽  
Specific Expression ◽  
Allele Specific Expression ◽  
Regulatory Interactions ◽  
Early Stages ◽  
Genome Wide ◽  
Allele Specific ◽  
Incomplete Reproductive Isolation

Speciation occurs when reproductive barriers prevent the exchange of genetic information between individuals. A common form of reproductive barrier between species capable of interbreeding is hybrid sterility. Genomic incompatibilities between the divergent genomes of different species contribute to a reduction in hybrid fitness. These incompatibilities continue to accumulate after speciation, therefore, young divergent taxa with incomplete reproductive isolation are important in understating the genetics leading to speciation. Here, I use two Drosophila subspecies pairs. The first is D. willistoni consisting of D. w. willistoni and D. w. winge. The second subspecies pair is D. pseudoobscura, which is composed of D. p. pseudoobscura and D. p. bogotana. Both subspecies pairs are at the early stages of speciation and show incomplete reproductive isolation through unidirectional hybrid male sterility. In this thesis, I performed an exploratory survey of genome-wide expression analysis using RNA-sequencing on D. willistoni and determined the extent of regulatory divergence between the subspecies using allele-specific expression analysis. I found that misexpressed genes showed a degree of tissue specificity and that the sterile male hybrids had a higher proportion of misexpressed genes in the testes relative to the fertile hybrids. The analysis of regulatory divergence between this subspecies pair found a large (66-70%) proportion of genes with conserved regulatory elements. Of the genes showing evidence or regulatory divergence between subspecies, cis-regulatory divergence was more common than other types. In the D. pseudoobscura subspecies pair, I compared sequence and expression divergence and found no support for directional selection driving gene misexpression in their hybrids. Allele-specific expression analysis revealed that compensatory cis-trans mutations partly explained gene misexpression in the hybrids. The remaining hybrid misexpression occurs due to interacting gene networks or possible co-option of cis-regulatory elements by divergent transacting factors. Overall, the results of this thesis highlight the role of regulatory interactions in a hybrid genome and how these interactions could lead to hybrid breakdown by disrupting gene interaction networks.

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