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Publications (105)
Ants exhibit many complex social organization strategies. One particularly elaborate strategy is supercoloniality, in which a colony consists of many interconnected nests (= polydomy) with many queens (= polygyny). In many species of Formica ants, an ancient queen number supergene determines whether a colony is monogyne (= headed by single queen) o...
A rapid proliferation in the availability of whole genome sequences (WGS), often with relatively low read depth, offers an unprecedented opportunity for phylogenomic advances using publicly available data, but there are several key challenges in applying these data. Using low‐coverage WGS data for the ant species of Formica , we conducted detailed...
Seasonal migration allows animals to use habitat where conditions are unfavorable for part of the year but may constrain breeding ranges due to the costs of longer migrations as ranges expand poleward. In species with large ranges, high latitude breeding populations may employ different migratory strategies allowing them to persist far from other c...
Ants exhibit many complex social organization strategies. One particularly elaborate strategy is supercoloniality, in which a colony consists of many interconnected nests (=polydomy) with many queens (=polygyny). In many species of Formica ants, an ancient queen number supergene determines whether a colony is monogyne (=headed by single queen) or p...
The study of social parasitism faces numerous challenges arising from the intricate and intranidal host–parasite interactions and the rarity of parasites compared to their free-living counterparts. As a result, our understanding of the ecology and evolution of most social parasites remains limited. Using whole-genome and reduced-representation sequ...
Desertification is a major threat to biodiversity in arid areas of the world, partly because many organisms in these regions already exist at or near the limits of their movement and physiology. Here, we used molecular data to investigate patterns of persistence and dispersal in an ecologically and economically important carpenter bee (Xylocopa gri...
Genomic analyses of hybrid zones provide excellent opportunities to investigate the consequences of introgression in nature. In combination with phylogenomics analyses, hybrid zone studies may illuminate the role of ancient and contemporary gene flow in shaping variation of phylogenetic signals across the genome, but this avenue has not been explor...
Vocal rhythm plays a fundamental role in sexual selection and species recognition in birds, but little is known of its genetic basis due to the confounding effect of vocal learning in model systems. Uncovering its genetic basis could facilitate identifying genes potentially important in speciation. Here we investigate the genomic underpinnings of r...
Genetic introgression, allele exchange across species boundaries, is a commonly recognized feature of animal evolution. Under such a paradigm, contemporary contact zones provide first-hand insight into the geographic, phenotypic, and genetic details of introgression. Also, when mate choice phenotypes are conspicuous and variable in hybrids, contact...
Antagonistic selection has long been considered a major driver of the formation and expansion of sex chromosomes. For example, sexually antagonistic variation on an autosome can select for suppressed recombination between that autosome and the sex chromosome, leading to a neo-sex chromosome. Autosomal supergenes, chromosomal regions containing tigh...
Bird song mediates speciation but little is known about its genetic basis because of the confounding effect of vocal learning in model systems. Rhythm, in particular, transcends acoustic communication across the animal kingdom and plays a fundamental role in sexual selection and species recognition in birds. Here we investigated the genomic underpi...
Gene flow can affect evolutionary inference when species are undersampled. Here, we evaluate the effects of gene flow and geographic sampling on demographic inference of two hummingbirds that hybridize, Allen's hummingbird (Selasphorus sasin) and rufous hummingbird (S. rufus). Using whole-genome data and extensive geographic sampling, we find wides...
In organisms reproducing sexually, speciation occurs when increasing divergence results in pre- or post-zygotic reproductive isolation between lineages. Studies focusing on reproductive isolation origin in early stages of speciation are common and many rely on genomic scans to infer introgression providing limited information on the genomic archite...
Models of both sex chromosome evolution and the genetic basis of local adaptation suggest that selection acts to lock beneficial combinations of alleles together in regions of reduced or suppressed recombination. Drawing inspiration from such models, we apply similar logic to investigate whether an autosomal supergene underlying colony social organ...
Despite their paramount importance in molecular ecology and conservation, genetic diversity and structure remain challenging to quantify with traditional genotyping methods. Next-generation sequencing holds great promises, but this has not been properly tested in highly mobile species. In this article, we compared microsatellite and RAD-sequencing...
Islands have been characterized as natural laboratories because of their distinct and often identifiable role in promoting genetic variation and population differentiation, but they have also been considered as evolutionary sinks of biodiversity. Here, we extend classical studies of island biogeography based in the Eastern Mediterranean to compare...
In organisms reproducing sexually, speciation occurs when increasing divergence results in pre- or post-zygotic reproductive isolation between lineages. Studies focusing on reproductive isolation origin in early stages of speciation are common. Many rely on indirect measures of introgression providing limited information on the genomic architecture...
Identifying mechanisms limiting hybridization is a central goal of speciation research. Here, we studied pre‐mating and post‐mating barriers to hybridization between two ant species, Formica selysi and Formica cinerea. These species hybridize in the Rhône valley in Switzerland, where they form a mosaic hybrid zone, with limited introgression from F...
Most supergenes discovered so far are young, occurring in one species or a few closely related species. An ancient supergene in the ant genus Formica presents an unusual opportunity to compare supergene‐associated phenotypes and the factors that influence the persistence of polymorphism in different species. We investigate the genetic architecture...
Behaviours are challenging to describe. Here, we apply k-mer analysis to characterize complex courtship behaviours at four hierarchical levels: elements, displays, bouts and repertoires, on two species of hummingbirds and their hybrids. During courtship, male rufous hummingbirds, Selasphorus rufus, perform three types of displays: shuttles (S), hal...
Desertification is a major threat to biodiversity in arid areas of the world, in part because many organisms in these regions are already existing at or near the limits of their movement and physiology. Here, we used molecular data to investigate patterns of persistence and dispersal in an ecologically and economically important carpenter bee (Xylo...
Significance
Some social insects exhibit split sex ratios, wherein a subset of colonies produce future queens and others produce males. This phenomenon spawned many influential theoretical studies and empirical tests, both of which have advanced our understanding of parent–offspring conflicts and the maintenance of cooperative breeding. However, pr...
Supergenes, regions of the genome with suppressed recombination between sets of functional mutations, contribute to the evolution of complex phenotypes in diverse systems. Excluding sex chromosomes, most supergenes discovered so far appear to be young, being found in one species or a few closely related species. Here, we investigate how a chromosom...
Unravelling when divergent lineages constitute distinct species can be challenging, particularly in complex scenarios combining cryptic diversity and phylogenetic discordances between different types of molecular markers. Combining a phylogenetic approach with the study of contact zones can help to overcome such difficulties. The Podarcis hispanicu...
Researchers seeking to generate genomic data for non‐model organisms are faced with a number of trade‐offs when deciding which method to use. The selection of reduced representation approaches versus whole genome re‐sequencing will ultimately affect the marker density, sequencing depth, and the number of individuals that can multiplexed. These fact...
Researchers seeking to generate genomic data for non-model organisms are faced with a number of trade-offs when deciding which method to use. The selection of reduced representation approaches versus whole genome re-sequencing will ultimately affect the marker density, sequencing depth, and the number of individuals that can multiplexed. These fact...
Introgressive hybridization can be a powerful force impacting patterns of evolution at multiple taxonomic levels. We aimed to understand how introgression has affected speciation and diversification within a species complex of jumping spiders. The Habronattus americanus subgroup is a recently radiating group of jumping spiders, with species now in...
Sexually reproducing organisms usually invest equally in male and female offspring. Deviations from this pattern have led researchers to new discoveries in the study of parent-offspring conflict, genomic conflict, and cooperation. Some social insect species exhibit the unusual population-level pattern of split sex ratio, wherein some colonies speci...
Allen's Hummingbird comprises two subspecies, one migratory (Selasphorus sasin sasin) and one nonmigratory (S. s. sedentarius). The nonmigratory subspecies, previously endemic to the California Channel Islands, apparently colonized the California mainland on the Palos Verdes Peninsula some time before 1970 and now breeds throughout coastal southern...
Sex chromosomes are classically predicted to stop recombining in the heterogametic sex, thereby enforcing linkage between sex-determining (SD) and sex-antagonistic (SA) genes. With the same rationale, a pre-existing sex asymmetry in recombination is expected to affect the evolution of heterogamety, e. g. a low rate of male recombination might favor...
Recent empirical studies have demonstrated that speciation with gene flow is more common than previously thought. From a conservation perspective, the potential negative effects of hybridization raise concerns on the genetic integrity of endangered species. However, introgressive hybridization has also been growingly recognized as a source of diver...
Species radiations have long served as model systems in evolutionary biology.1,2 However, it has only recently become possible to study the genetic bases of the traits responsible for diversification and only in a small number of model systems.3 Here, we use genomes of 36 species of North, Central, and South American warblers to highlight the role...
It has long been of interest to identify the phenotypic traits that mediate reproductive isolation between related species, and more recently, the genes that underpin them. Much work has focused on identifying genes associated with animal colour, with the candidate gene CYP2J19 identified in laboratory studies as the ketolase converting yellow diet...
Background:
The study of speciation has expanded with the increasing availability and affordability of high-resolution genomic data. How the genome evolves throughout the process of divergence and which regions of the genome are responsible for causing and maintaining that divergence have been central questions in recent work. Here, we use three p...
Premise:
Delimiting biodiversity units is difficult in organisms in which differentiation is obscured by hybridization, plasticity, and other factors that blur phenotypic boundaries. Such work is more complicated when the focal units are subspecies, the definition of which has not been broadly explored in the era of modern genetic methods. Eastwoo...
Supergenes, clusters of tightly linked genes, play a key role in the evolution of complex adaptive variation [1, 2]. Although supergenes have been identified in many species, we lack an understanding of their origin, evolution, and persistence [3]. Here, we uncover 20-40 Ma of evolutionary history of a supergene associated with polymorphic social o...
Several lines of evidence support that north-Italian and Ticinese tree frogs, recently called
Hyla perrini, represent a distinct species, formerly considered as Hyla intermedia. However, a nomenclatural clause for electronic publishing of species names according to the Code of International Nomenclature caused that the new name has been unavailable...
The canonical model of sex-chromosome evolution predicts that, as recombination is suppressed along sex chromosomes, gametologs will progressively differentiate, eventually becoming heteromorphic. However, there are numerous examples of homomorphic sex chromosomes across the tree of life. This homomorphy has been suggested to result from frequent s...
Despite increasing appreciation of the speciation continuum, delimiting and describing new species is a major yet necessary challenge of modern phylogeography to help optimize conservation efforts. In amphibians, the lack of phenotypic differences between closely-related taxa, their complex, sometimes unresolved phylogenetic relationships, and thei...
Hybrid zones provide a key natural context within which to study the barriers between incipient species. In some avian hybrid zones, there is indirect evidence of selection against hybrid offspring, yet the source of that selection is often unclear. We examined the frequency distribution of hybrids between Myrtle Warblers (Setophaga coronata corona...
Parasites can play a role in speciation, by exerting different selection pressures on different host lineages, leading to reproductive barriers in regions of possible interbreeding. Hybrid zones therefore offer an ideal system to study the effect of parasites on speciation. Here, we study a hybrid zone in the foothills of the Rocky Mountains where...
Detailed evaluations of genomic variation between sister species often reveal distinct chromosomal regions of high relative differentiation (i.e., “islands of differentiation” in FST), but there is much debate regarding the causes of this pattern. We briefly review the prominent models of genomic islands of differentiation and compare patterns of g...
Genomic analyses have demonstrated that species often have semipermeable boundaries with highly variable levels of introgression among loci. Studying these processes in hybrid zones may shed light on the fraction of the genome that participates in reproductive isolation. The Iberian wall lizard (Podarcis hispanicus) species complex is a good model...
The process of speciation is often equated to the acquisition of reproductive isolation. This is a process typically envisioned as being correlated to divergence time: as time progresses the more likely it will be for diverging taxa to experience restrictions to gene exchange. This correlation has been tested and verified in a wide range of taxa; h...
Non‐recombining genomic variants underlie spectacular social polymorphisms, from bird mating systems to ant social organization. Because these “social supergenes” affect multiple phenotypic traits linked to survival and reproduction, explaining their persistence remains a substantial challenge. Here, we investigate how large non‐recombining genomic...
Dobzhansky‐Muller (DM) incompatibilities involving sex chromosomes have been proposed to account for Haldane's rule (lowered fitness among hybrid offspring of the heterogametic sex) as well as Darwin's corollary (asymmetric fitness costs with respect to the direction of the cross). We performed simulation studies of a hybrid zone to investigate the...
Identifying the genetic bases for colour patterns has provided important insights into the control and expression of pigmentation and howthese characteristics influence fitness. However, much more is known about the genetic bases for traits based on melanin pigments than for traits based on another major class of pigments, carotenoids. Here, we use...
Genomic analysis have demonstrated that many hybrid zones are semipermeable boundaries where introgression can be highly variable, with some alleles introgressing and recombining into genomic background of the other species while others are less able to cross the species boundary. This way we can infer which fraction of the genome is counter select...
Restriction site‐associated DNA sequencing (RAD‐seq) provides high‐resolution population genomic data at low cost, and has become an important component in ecological and evolutionary studies. As with all high‐throughput technologies, analytic strategies require critical validation to ensure precise and unbiased interpretation.
To test the impact o...
We demonstrate a genotyping-by-sequencing approach to identify homomorphic sex chromosomes and their homolog in a distantly related reference genome, based on non-invasive sampling of wild-caught individuals, in the moor frog Rana arvalis. Double-digest RADseq libraries were generated using buccal swabs from 30 males and 21 females from the same po...
When related taxa hybridize extensively, their genomes may become increasingly homogenized over time. This mixing via hybridization creates conservation challenges when it reduces genetic or phenotypic diversity and when it endangers previously distinct species via genetic swamping [1]. However, hybridization also facilitates admixture mapping of t...
Research on hybridization between species provides unparalleled insights into the pre- and post-zygotic isolating mechanisms that drive speciation. In social organisms, colony-level incompatibilities may provide additional reproductive barriers not present in solitary species, and hybrid zones offer an opportunity to identify these barriers. Here,...
Appendix S1.
Text S1. Seven scaffolds from the draft genome of Rana temporaria, containing, respectively, the five Dmrt1 exons, Kank1 intron 1, and Dmrt3 intron 1.
Text S2. Transcript sequences of R. temporaria Dmrt1 in five froglets.
Text S3. Concatenated sequences of three Dmrt1 polymorphic sites for 26 individuals from Ammarnäs and Tvedöra.
Appendix S2
Table S1. Primer pairs and PCR conditions for amplifying Dmrt1 transcript and individual exons.
Table S2. Primers pairs and PCR conditions for genotyping.
Table S3. Between‐sex F
ST values in Ammarnäs and Tvedöra.
Patterns of sex-chromosome differentiation and gonadal development have been shown to vary among populations of Rana temporaria along a latitudinal transect in Sweden. Frogs from the northern-boreal population of Ammarnäs displayed well-differentiated X and Y haplotypes, early gonadal differentiation, and a perfect match between phenotypic and geno...
The patterns of sex determination and sex differentiation have been shown to differ among geographic populations of common frogs. Notably, the association between phenotypic sex and linkage group 2 (LG2) has been found to be perfect in a northern Swedish population, but weak and variable among families in a southern one. By analyzing these populati...
Populations that have experienced long periods of geographic isolation will diverge over time. The application of high-throughput sequencing technologies to study the genomes of related taxa now allows us to quantify, at a fine scale, the consequences of this divergence across the genome. Throughout a number of studies, a notable pattern has emerge...
Identifying homology between sex chromosomes of different species is essential to understanding the evolution of sex determination. Here, we show that the identity of a homomorphic sex chromosome pair can be established using a linkage map, without information on offspring sex. By comparing sex-specific maps of the European tree frog Hyla arborea,...
Empirical studies on the relative roles of occasional XY recombination versus sex-chromosome turnover in preventing sex-chromosome differentiation may shed light on the evolutionary forces acting on sex-determination systems. Signatures of XY recombination are difficult to distinguish from those of homologous transitions (i.e., transitions in sex-d...
Sex-chromosome differentiation in Rana temporaria varies strikingly among populations or families: whereas some males display well-differentiated Y haplotypes at microsatellite markers on linkage group 2 (LG2), others are genetically undistinguishable from females. We analyzed with RADseq markers one family from a Swiss lowland population with no d...
Background: Hybridization between incipient species is expected to become progressively limited as their genetic divergence increases and reproductive isolation proceeds. Amphibian radiations and their secondary contact zones are useful models to infer the timeframes of speciation, but empirical data from natural systems remains extremely scarce. H...
Contrasting with birds and mammals, poikilothermic vertebrates often have homomorphic sex chromosomes, possibly resulting from high rates of sex-chromosome turnovers and/or occasional X-Y recombination. Strong support for the latter mechanism was provided by four species of European tree frogs, which inherited from a common ancestor (~ 5 Mya) the s...
Western Palearctic tree frogs (Hyla arborea group) represent a strong potential for evolutionary and conservation genetic research, so far underexploited due to limited molecular resources. New microsatellite markers have recently been developed for Hyla arborea, with high cross-species utility across the entire circum-Mediterranean radiation. Here...
Complex adaptive polymorphisms are common in nature, but what mechanisms maintain the underlying favorable allelic combinations [1-4]? The convergent evolution of polymorphic social organization in two independent ant species provides a great opportunity to investigate how genomes evolved under parallel selection. Here, we demonstrate that a large,...
Occasional XY recombination is a proposed explanation for the sex-chromosome homomorphy in European tree frogs. Numerous laboratory crosses, however, failed to detect any event of male recombination, and a detailed survey of NW-European Hyla arborea populations identified male-specific alleles at sex-linked loci, pointing to the absence of XY recom...
A simple way to quickly optimize microsatellites in non-model organisms is to re-use loci available in closely related taxa; however, this approach can be limited by the stochastic and low cross-amplification success experienced in some groups (e.g. amphibians). An efficient alternative is to develop loci from transcriptome sequences. Transcriptomi...
In contrast with mammals and birds, most poikilothermic vertebrates feature structurally undifferentiated sex chromosomes, which may result either from frequent turnovers, or from occasional events of XY recombination. The latter mechanism was recently suggested to be responsible for sex-chromosome homomorphy in European tree frogs (Hyla arborea)....
Differences in seasonal migratory behaviours are thought to be an important component of reproductive isolation in many organisms. Stable isotopes have been used with success in estimating the location and qualities of disjunct breeding and wintering areas. However, few studies have used isotopic data to estimate the movements of hybrid offspring i...
Speciation is a fundamental evolutionary process, the knowledge of which is crucial for understanding the origins of biodiversity. Genomic approaches are an increasingly important aspect of this research field. We review current understanding of genome-wide effects of accumulating reproductive isolation and of genomic properties that influence the...
Documenting and preserving the genetic diversity of populations, which conditions their long-term survival, has become a major issue in conservation biology. The loss of diversity often documented in declining populations is usually assumed to result from human disturbances; however, historical biogeographic events, otherwise known to strongly impa...
Comparative genomic studies are revealing that, in sharp contrast with the strong stability found in birds and mammals, sex determination mechanisms are surprisingly labile in cold-blooded vertebrates, with frequent transitions between different pairs of sex chromosomes. It was recently suggested that, in context of this high turnover, some chromos...
Studies of hybrid zones can inform our understanding of reproductive isolation and speciation. Two species of brown lemur (Eulemur rufifrons and E. cinereiceps) form an apparently stable hybrid zone in the Andringitra region of south-eastern Madagascar. The aim of this study was to identify factors that contribute to this stability. We sampled anim...
Contrasting with the situation found in birds and mammals, sex chromosomes are generally homomorphic in poikilothermic vertebrates. This homomorphy was recently shown to result from occasional X-Y recombinations (not from turnovers) in several European species of tree frogs (Hyla arborea, H. intermedia and H. molleri). Because of recombination, how...
Hybridization has many and varied impacts on the process of speciation. Hybridization may slow or reverse differentiation by allowing gene flow and recombination. It may accelerate speciation via adaptive introgression or cause near-instantaneous speciation by allopolyploidization. It may have multiple effects at different stages and in different s...
Explaining the evolution of sociality is challenging because social individuals face disadvantages that must be balanced by intrinsic benefits of living in a group. One potential route towards the evolution of sociality may emerge from the avoidance of dispersal, which can be risky in some environments. Although early studies found that local compe...
Combining nuclear (nuDNA) and mitochondrial DNA (mtDNA) markers has improved the power of molecular data to test phylogenetic and phylogeographic hypotheses and has highlighted the limitations of studies using only mtDNA markers. In fact, in the past decade, many conflicting geographic patterns between mitochondrial and nuclear genetic markers have...
Hybridization has presented a challenge for taxonomists and conservation biologists, since hybridizing forms could be stable evolutionary entities or ephemeral forms that are blending together. However, hybrid zones also provide a unique opportunity for evolutionary biologists who study the interaction between gene flow and reproductive isolation i...
Hybrid zones between species provide natural systems for the study of processes involved in divergence, reproductive isolation and speciation. Townsend's Dendroica townsendi and black-throated green D. virens warblers are phenotypically and genetically divergent groups that occur in western and eastern North America respectively, with potential for...
High-fidelity 'proofreading' polymerases are often used in library construction for next-generation sequencing projects, in an effort to minimize errors in the resulting sequence data. The increased template fidelity of these polymerases can come at the cost of reduced template specificity, and library preparation methods based on the AFLP techniqu...
Hybrid speciation was once thought to be rare in animals, but over the past decade, improved molecular analysis techniques and increased research attention have allowed scientists to uncover many examples. In this issue, two papers (Elgvin et al. 2011; Hermansen et al. 2011) present compelling evidence for the hybrid origin of the Italian sparrow b...
Several animal species have recently been shown to have hybrid origins, but no avian examples have been documented with molecular evidence. We investigate whether the Audubon’s warbler (Dendroica auduboni), one of four visually distinct species in the yellow-rumped warbler complex, has originated through hybridization between two other species in t...
Hybrid zones between species provide natural systems for the study of processes involved in divergence, reproductive isolation and speciation. Townsend's Dendroica townsendi and black-throated green D. virens warblers are phenotypically and genetically divergent groups that occur in western and eastern North America respectively, with potential for...
