scholarly journals Prevalence of disruptive selection predicts extent of species differentiation in Lake Victoria cichlids

2018 ◽  
Vol 285 (1871) ◽  
pp. 20172630 ◽  
Author(s):  
Jacco C. van Rijssel ◽  
Florian N. Moser ◽  
David Frei ◽  
Ole Seehausen
Keyword(s):  
Gene Flow ◽  
Natural Selection ◽  
Genetic Differentiation ◽  
Lake Victoria ◽  
Sister Species ◽  
Disruptive Selection ◽  
Nuptial Coloration ◽  
Ecological Selection ◽  
Evolutionary Response ◽  
Species Pairs

Theory suggests that speciation with gene flow is most likely when both sexual and ecological selection are divergent or disruptive. Divergent sexual and natural selection on the visual system have been demonstrated before in sympatric, morphologically similar sister species of Lake Victoria cichlids, but this does not explain the subtle morphological differences between them. To investigate the significance of natural selection on morphology during speciation, we here ask whether the prevalence of disruptive ecological selection differs between sympatric sister species that are at different stages of speciation. Some of our species pairs do ( Pundamilia ) and others do not ( Neochromis ) differ distinctively in sexually selected male nuptial coloration. We find that (i) evidence for disruptive selection, and for evolutionary response to it, is prevalent in traits that are differentiated between sister species; (ii) prevalence of both predicts the extent of genetic differentiation; and (iii) genetic differentiation is weaker in species pairs with conserved male nuptial coloration. Our results speak to the existence of two different mechanisms of speciation with gene flow: speciation mainly by sexual selection tightly followed by ecological character displacement in some cases and speciation mainly by divergent ecological selection in others.

scholarly journals Genetic architecture of a key reproductive isolation trait differs between sympatric and non-sympatric sister species of Lake Victoria cichlids

2020 ◽  
Vol 287 (1924) ◽  
pp. 20200270
Author(s):  
Anna F. Feller ◽  
Marcel P. Haesler ◽  
Catherine L. Peichel ◽  
Ole Seehausen
Keyword(s):  
Gene Flow ◽  
Reproductive Isolation ◽  
Related Species ◽  
Genetic Architecture ◽  
Lake Victoria ◽  
Sympatric Species ◽  
Sister Species ◽  
Species Pair ◽  
Closely Related Species ◽  
Nuptial Coloration

One hallmark of the East African cichlid radiations is the rapid evolution of reproductive isolation that is robust to full sympatry of many closely related species. Theory predicts that species persistence and speciation in sympatry with gene flow are facilitated if loci of large effect or physical linkage (or pleiotropy) underlie traits involved in reproductive isolation. Here, we investigate the genetic architecture of a key trait involved in behavioural isolation, male nuptial coloration, by crossing two sister species pairs of Lake Victoria cichlids of the genus Pundamilia and mapping nuptial coloration in the F2 hybrids. One is a young sympatric species pair, representative of an axis of colour motif differentiation, red-dorsum versus blue, that is highly recurrent in closely related sympatric species. The other is a species pair representative of colour motifs, red-chest versus blue, that are common in allopatric but uncommon in sympatric closely related species. We find significant quantitative trait loci (QTLs) with moderate to large effects (some overlapping) for red and yellow in the sympatric red-dorsum × blue cross, whereas we find no significant QTLs in the non-sympatric red-chest × blue cross. These findings are consistent with theory predicting that large effect loci or linkage/pleiotropy underlying mating trait differentiation could facilitate speciation and species persistence with gene flow in sympatry.

scholarly journals Extraordinarily rapid life-history divergence between Cryptasterina sea star species

2012 ◽  
Vol 279 (1744) ◽  
pp. 3914-3922 ◽  
Author(s):  
Jonathan B. Puritz ◽  
Carson C. Keever ◽  
Jason A. Addison ◽  
Maria Byrne ◽  
Michael W. Hart ◽  
...  
Keyword(s):  
Life History ◽  
Gene Flow ◽  
Critical Role ◽  
Divergence Time ◽  
Sister Species ◽  
Disruptive Selection ◽  
Sea Star ◽  
Posterior Density ◽  
Sea Stars ◽  
Highest Posterior Density

Life history plays a critical role in governing microevolutionary processes such as gene flow and adaptation, as well as macroevolutionary processes such speciation. Here, we use multilocus phylogeographic analyses to examine a speciation event involving spectacular life-history differences between sister species of sea stars. Cryptasterina hystera has evolved a suite of derived life-history traits (including internal self-fertilization and brood protection) that differ from its sister species Cryptasterina pentagona , a gonochoric broadcast spawner . We show that these species have only been reproductively isolated for approximately 6000 years (95% highest posterior density of 905–22 628), and that this life-history change may be responsible for dramatic genetic consequences, including low nucleotide diversity, zero heterozygosity and no gene flow. The rapid divergence of these species rules out some mechanisms of isolation such as adaptation to microhabitats in sympatry, or slow divergence by genetic drift during prolonged isolation. We hypothesize that the large phenotypic differences between species relative to the short divergence time suggests that the life-history differences observed may be direct responses to disruptive selection between populations. We speculate that local environmental or demographic differences at the southern range margin are possible mechanisms of selection driving one of the fastest known marine speciation events.

scholarly journals The Pleistocene species pump past its prime: evidence from European butterfly sister species

2020 ◽  
Author(s):  
Sam Ebdon ◽  
Dominik R. Laetsch ◽  
Leonardo Dapporto ◽  
Alexander Hayward ◽  
Michael G. Ritchie ◽  
...  
Keyword(s):  
Gene Flow ◽  
Contact Zone ◽  
Sister Species ◽  
Transcriptome Data ◽  
Last Interglacial ◽  
Species Divergence ◽  
Glacial Cycles ◽  
Contact Zones ◽  
Genome Wide ◽  
Species Pairs

AbstractThe Pleistocene glacial cycles had a profound impact on the ranges and genetic make-up of organisms. Whilst it is clear that the contact zones that have been described for many sister taxa are secondary and have formed during the last interglacial, it is unclear when the taxa involved began to diverge. Previous estimates based on small numbers of loci are unreliable given the stochasticity of genetic drift and the contrasting effects of incomplete lineage sorting and gene flow on gene divergence. Here we use genome-wide transcriptome data to estimate divergence for 18 sister species pairs of European butterflies showing either sympatric or contact zone distributions. We find that in most cases species divergence predates the mid-Pleistocene transition or even the entire Pleistocene period. We also show that although post divergence gene flow is restricted to contact zone pairs, they are not systematically younger than sympatric pairs. This suggests that contact zones are not limited to the embryonic stages of the speciation process, but can involve notably old taxa. Finally, we show that mitochondrial and nuclear divergence are only weakly correlated and mitochondrial divergence is higher for contact-zone pairs. This suggests a possible role of selective sweeps affecting mitochondrial variation in maintaining contact zones.Impact SummaryThe influence of the Pleistocene glacial cycles on structuring species and genetic diversity in temperate taxa has permeated biogeographic and phylogeographic thinking for decades. Although phylogeographic studies have repeatedly claimed that the Pleistocene acted as a species pump, systematic tests of this idea based on robust estimates of species divergence are lacking. Here we estimate divergence times for all sister species pairs of European butterfly using genome-wide transcriptome data. We find that most species pairs are substantially older than the onset of Pleistocene glacial cycling. We also show that post divergence gene flow is restricted to pairs that form contact-zones. However, in contrast to expectations under a null model of allopatric speciation contract zone pairs are not necessarily younger than sympatric pairs.

scholarly journals Global drivers of diversification in a marine species complex

2019 ◽  
Author(s):  
Catarina N.S. Silva ◽  
Nicholas P. Murphy ◽  
James J. Bell ◽  
Bridget S. Green ◽  
Guy Duhamel ◽  
...  
Keyword(s):  
Gene Flow ◽  
Genetic Differentiation ◽  
Continental Shelf ◽  
Demographic History ◽  
Significant Proportion ◽  
Secondary Contact ◽  
Larval Duration ◽  
Genome Wide ◽  
Extant Species ◽  
Species Pairs

AbstractInvestigating historical gene flow in species complexes can indicate how environmental and reproductive barriers shape genome divergence before speciation. The processes influencing species diversification under environmental change remain one of the central focal points of evolutionary biology, particularly for marine organisms with high dispersal potential. We investigated genome-wide divergence, introgression patterns and inferred demographic history between species pairs of all extant rock lobster species (Jasus spp.), a complex with long larval duration, that has populated continental shelf and seamount habitats around the globe at approximately 40°S. Genetic differentiation patterns revealed the effects of the environment and geographic isolation. Species associated with the same habitat structure (either continental shelf or seamount/island) shared a common ancestry, even though the habitats were not adjacent. Differences in benthic temperature explained a significant proportion (41.3%) of the genetic differentiation. The Eastern Pacific species pair of J. caveorum and J. frontalis retained a signal of strict isolation following ancient migration, whereas species pairs from Australia and Africa and seamounts in the Indian and Atlantic oceans included events of introgression after secondary contact. Parameters estimated for time in isolation and gene flow were congruent with genetic differentiation metrics suggesting that the observed differentiation patterns are the product of migration and genetic drift. Our results reveal important effects of habitat and demographic processes on the divergence of species within the genus Jasus providing the first empirical study of genome-wide drivers of diversification that incorporates all extant species in a marine genus with long pelagic larval duration.

scholarly journals Introgression between ecologically distinct species following increased salinity in the Colorado Delta- Worldwide implications for impacted estuary diversity

PeerJ ◽  
2017 ◽  
Vol 5 ◽  
pp. e4056 ◽  
Author(s):  
Clive L.F. Lau ◽  
David K. Jacobs
Keyword(s):  
At Risk ◽  
Gulf Of California ◽  
Extinction Risk ◽  
Habitat Destruction ◽  
Sister Species ◽  
Past Century ◽  
Salinity Regime ◽  
Salinity Gradients ◽  
Evolutionary Response ◽  
Species Pairs

We investigate hybridization and introgression between ecologically distinct sister species of silverside fish in the Gulf of California through combined analysis of morphological, sequence, and genotypic data. Water diversions in the past century turned the Colorado River Delta from a normal estuary to a hypersaline inverse estuary, raising concerns for the local fauna, much of which is endangered. Salinity differences are known to generate ecological species pairs and we anticipated that loss of the fresher-water historic salinity regime could alter the adaptive factors maintaining distinction between the broadly distributed Gulf-endemicColpichthys regisand the narrowly restricted Delta-endemicColpichthys hubbsi, the species that experienced dramatic environmental change. In this altered environmental context, these long-isolated species (as revealed by Cytochromebsequences) show genotypic (RAG1, microsatellites) evidence of active hybridization where the species ranges abut, as well as directional introgression fromC. regisinto the range center ofC. hubbsi. Bayesian group assignment (STRUCTURE) on six microsatellite loci and multivariate analyses (DAPC) on both microsatellites and phenotypic data further support substantial recent admixture between the sister species. Although we find no evidence for recent population decline inC. hubbsibased on mitochondrial sequence, introgression may be placing an ancient ecological species at risk of extinction. Such introgressive extinction risk should also pertain to other ecological species historically sustained by the now changing Delta environment. More broadly, salinity gradient associated ecological speciation is evident in silverside species pairs in many estuarine systems around the world. Ecological species pairs among other taxa in such systems are likely poorly understood or cryptic. As water extraction accelerates in river systems worldwide, salinity gradients will necessarily be altered, impacting many more estuary and delta systems. Such alteration of habitats will place biodiversity at risk not only from direct effects of habitat destruction, but also from the potential for the breakdown of ecological species. Thus, evolutionary response to the anthropogenic alteration of salinity gradients in estuaries merits investigation as the number of impacted systems increases around the globe, permitting parallel study of multiple systems, while also permitting a conservation management response to help preserve this little championed component of biodiversity.

scholarly journals Introgression between ecologically distinct species following increased salinity in the Colorado Delta- Worldwide implications for impacted estuary diversity

2017 ◽  
Author(s):  
Clive L.F. Lau ◽  
David K. Jacobs
Keyword(s):  
At Risk ◽  
Gulf Of California ◽  
Extinction Risk ◽  
Habitat Destruction ◽  
Sister Species ◽  
Past Century ◽  
Salinity Regime ◽  
Salinity Gradients ◽  
Evolutionary Response ◽  
Species Pairs

We investigate hybridization and introgression between ecologically distinct sister species of silverside fish in the Gulf of California through combined analysis of morphological, sequence, and genotypic data. Water diversions in the past century turned the Colorado River Delta from a normal estuary to a hypersaline inverse estuary, raising concerns for the local fauna, much of which is endangered. Salinity differences are known to generate ecological species pairs and we anticipated that loss of the fresher-water historic salinity regime could alter the adaptive factors maintaining distinction between the broadly distributed Gulf-endemic Colpichthys regis and the narrowly restricted Delta-endemic Colpichthis hubbsi, the species that experienced dramatic environmental change. In this altered environmental context, these long-isolated species (as revealed by Cytochrome b sequences) show genotypic (RAG1, microsatellites) evidence of active hybridization where the species ranges abut, as well as directional introgression from C. regis into the range center of C. hubbsi. Bayesian group assignment (STRUCTURE) on six microsatellite loci and multivariate analyses (DAPC) on both microsatellites and phenotypic data further support substantial recent admixture between the sister species. Although we find no evidence for recent population decline in C. hubbsi based on mitochondrial sequence, introgression may be placing an ancient ecological species at risk of extinction. Such introgressive extinction risk should also pertain to a number of other ecological species historically sustained by the now changing Delta environment. More broadly, salinity gradient associated ecological speciation is evident in silverside species pairs in many estuarine systems around the world. Ecological species pairs among other taxa in such systems are likely poorly understood or cryptic. As water extraction accelerates in river systems worldwide, salinity gradients will necessarily be altered, impacting many more estuary and delta systems. Such alteration of habitats will place biodiversity at risk not only from direct effects of habitat destruction, but also from the potential for the breakdown of ecological species. Thus, evolutionary response to the anthropogenic alteration of salinity gradients in estuaries merits investigation as the number of impacted systems increases around the globe, permitting parallel study of multiple systems, while also permitting a conservation management response to help preserve this little championed component of biodiversity.

scholarly journals Disruptive sexual selection on male nuptial coloration in an experimental hybrid population of cichlid fish

2008 ◽  
Vol 363 (1505) ◽  
pp. 2861-2870 ◽  
Author(s):  
Rike B Stelkens ◽  
Michele E.R Pierotti ◽  
Domino A Joyce ◽  
Alan M Smith ◽  
Inke van der Sluijs ◽  
...  
Keyword(s):  
Gene Flow ◽  
Mate Choice ◽  
Cichlid Fish ◽  
Hybrid Population ◽  
Disruptive Selection ◽  
Male Mating ◽  
Mating Preferences ◽  
Nuptial Coloration ◽  
Female Mating ◽  
Female Mating Preferences

Theory suggests that genetic polymorphisms in female mating preferences may cause disruptive selection on male traits, facilitating phenotypic differentiation despite gene flow, as in reinforcement or other models of speciation with gene flow. Very little experimental data have been published to test the assumptions regarding the genetics of mate choice that such theory relies on. We generated a population segregating for female mating preferences and male colour dissociated from other species differences by breeding hybrids between species of the cichlid fish genus Pundamilia . We measured male mating success as a function of male colour. First, we demonstrate that non-hybrid females of both species use male nuptial coloration for choosing mates, but with inversed preferences. Second, we show that variation in female mating preferences in an F 2 hybrid population generates a quadratic fitness function for male coloration suggestive of disruptive selection: intermediate males obtained fewer matings than males at either extreme of the colour range. If the genetics of female mate choice in Pundamilia are representative for those in other species of Lake Victoria cichlid fish, it may help explain the origin and maintenance of phenotypic diversity despite some gene flow.

scholarly journals Introgression between ecologically distinct species following increased salinity in the Colorado Delta- Worldwide implications for impacted estuary diversity

2017 ◽  
Author(s):  
Clive L.F. Lau ◽  
David K. Jacobs
Keyword(s):  
At Risk ◽  
Gulf Of California ◽  
Extinction Risk ◽  
Habitat Destruction ◽  
Sister Species ◽  
Past Century ◽  
Salinity Regime ◽  
Salinity Gradients ◽  
Evolutionary Response ◽  
Species Pairs

We investigate hybridization and introgression between ecologically distinct sister species of silverside fish in the Gulf of California through combined analysis of morphological, sequence, and genotypic data. Water diversions in the past century turned the Colorado River Delta from a normal estuary to a hypersaline inverse estuary, raising concerns for the local fauna, much of which is endangered. Salinity differences are known to generate ecological species pairs and we anticipated that loss of the fresher-water historic salinity regime could alter the adaptive factors maintaining distinction between the broadly distributed Gulf-endemic Colpichthys regis and the narrowly restricted Delta-endemic Colpichthis hubbsi, the species that experienced dramatic environmental change. In this altered environmental context, these long-isolated species (as revealed by Cytochrome b sequences) show genotypic (RAG1, microsatellites) evidence of active hybridization where the species ranges abut, as well as directional introgression from C. regis into the range center of C. hubbsi. Bayesian group assignment (STRUCTURE) on six microsatellite loci and multivariate analyses (DAPC) on both microsatellites and phenotypic data further support substantial recent admixture between the sister species. Although we find no evidence for recent population decline in C. hubbsi based on mitochondrial sequence, introgression may be placing an ancient ecological species at risk of extinction. Such introgressive extinction risk should also pertain to a number of other ecological species historically sustained by the now changing Delta environment. More broadly, salinity gradient associated ecological speciation is evident in silverside species pairs in many estuarine systems around the world. Ecological species pairs among other taxa in such systems are likely poorly understood or cryptic. As water extraction accelerates in river systems worldwide, salinity gradients will necessarily be altered, impacting many more estuary and delta systems. Such alteration of habitats will place biodiversity at risk not only from direct effects of habitat destruction, but also from the potential for the breakdown of ecological species. Thus, evolutionary response to the anthropogenic alteration of salinity gradients in estuaries merits investigation as the number of impacted systems increases around the globe, permitting parallel study of multiple systems, while also permitting a conservation management response to help preserve this little championed component of biodiversity.

scholarly journals Natural selection maintains species despite widespread hybridization in the desert shrub Encelia

2020 ◽  
Author(s):  
Christopher D DiVittorio ◽  
Sonal Singhal ◽  
Adam B Roddy ◽  
Felipe Zapata ◽  
David D Ackerly ◽  
...  
Keyword(s):  
Gene Flow ◽  
Natural Selection ◽  
Field Experiments ◽  
Population Genomics ◽  
Coastal Dunes ◽  
Species Boundaries ◽  
Hybrid Zones ◽  
Desert Shrubs ◽  
Species Complexes ◽  
Species Pairs

ABSTRACTNatural selection is an important driver of genetic and phenotypic differentiation between species. A powerful way to test the role of natural selection in the formation and maintenance of species is to study species complexes in which potential gene flow is high but realized gene flow is low. For a recent radiation of New World desert shrubs (Encelia: Asteraceae), we use fine-scale geographic sampling and population genomics to determine patterns of gene flow across two hybrid zones formed between two independent pairs of species with parapatric distributions. After finding evidence for extremely strong selection at both hybrid zones, we use a combination of field experiments, high-resolution imaging, and physiological measurements to determine the ecological basis for selection at one of the hybrid zones. Our results identify multiple ecological mechanisms of selection (drought, salinity, herbivory, and burial) that together are sufficient to maintain species boundaries despite high rates of hybridization. Given that multiple pairs of species hybridize at ecologically divergent parapatric boundaries in the adaptive radiation of Encelia, such mechanisms may maintain species boundaries throughout this group.SIGNIFICANCE STATEMENTIn Baja California, the deserts meet the coastal dunes in a narrow transition visible even from satellite images. We study two species pairs of desert shrubs (Encelia) that occur across this transition. Although these species can interbreed, they remain distinct. Using a combination of genetics, field experiments, 3D-imaging, and physiological measurements, we show that natural selection counteracts the homogenizing effects of gene exchange. The different habitats of these species create multiple mechanisms of selection - drought, salinity, herbivory, and burial, which together maintain these species in their native habitats and their hybrids in intermediate habitats. This study illustrates how environmental factors influence traits and fitness and how this in turn maintain species, highlighting the importance of natural selection in speciation.

scholarly journals Intense Browsing by Sika Deer (Cervus Nippon) Drives the Genectic Differentiation of Hairy Nettle (Urtica Thunbergiana) Populations

2021 ◽  
Author(s):  
Tetsuo I. Kohyama ◽  
Mei Yoshida ◽  
Masahito T. Kimura ◽  
Hiroaki Sato
Keyword(s):  
Gene Flow ◽  
Natural Selection ◽  
Genetic Differentiation ◽  
Genetic Drift ◽  
Sika Deer ◽  
Cervus Nippon ◽  
Deer Browsing ◽  
Principal Coordinates ◽  
Outlier Loci ◽  
Two Populations

Abstract Many studies have inferred the way in which natural selection, genetic drift and gene flow shape the population genetic structures, but very few have quantified the population differentiation under spatially and temporally varying levels of selection pressure, population fluctuation and gene flow. In Nara Park (6.6 km2; NP), central Japan, where several hundred sika deer (Cervus nippon) have been protected for more than 1,200 years, heavily- or moderately-haired nettle (Uritica thunbergiana) populations have evolved probably in response to intense deer browsing. Here, we analysed the genetic structure of two populations from NP and five from surrounding areas using amplified fragment length polymorphism markers. A total of 546 marker loci were genotyped from 210 individuals. A Bayesian method estimated 5.5% of these loci to be outliers, which are putatively under natural selection. Neighbour-joining, Bayesian clustering and principal coordinates analyses using all-loci, non-outlier loci and outlier loci datasets showed that the two populations from NP formed a cluster distinct from the surroundings. These results indicate the genome-wide differentiation of the populations from NP and the surroundings. Moreover, these imply that: (1) gene flow is limited between these populations and thus genetic drift is a major factor causing the differentiation; and (2) natural selection imposed by intense deer browsing has contributed to some extent to the differentiation. In conclusion, sika deer seems to have counteracted genetic drift to drive the genetic differentiation of hairy nettles in NP. This study suggests that a single herbivore species could lead genetic differentiation among plant populations.

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