scholarly journals Hybridization increases population variation during adaptive radiation

2019 ◽  
Vol 116 (46) ◽  
pp. 23216-23224 ◽  
Author(s):  
Peter R. Grant ◽  
B. Rosemary Grant
Keyword(s):  
Introgressive Hybridization ◽  
Population Variation ◽  
Small Island ◽  
Ecological Niches ◽  
Future Evolution ◽  
Adaptive Radiations ◽  
Geospiza Fortis ◽  
Dated Phylogeny ◽  
Independent Effects ◽  
Short Time

Adaptive radiations are prominent components of the world’s biodiversity. They comprise many species derived from one or a small number of ancestral species in a geologically short time that have diversified into a variety of ecological niches. Several authors have proposed that introgressive hybridization has been important in the generation of new morphologies and even new species, but how that happens throughout evolutionary history is not known. Interspecific gene exchange is expected to have greatest impact on variation if it occurs after species have diverged genetically and phenotypically but before genetic incompatibilities arise. We use a dated phylogeny to infer that populations of Darwin’s finches in the Galápagos became more variable in morphological traits through time, consistent with the hybridization hypothesis, and then declined in variation after reaching a peak. Some species vary substantially more than others. Phylogenetic inferences of hybridization are supported by field observations of contemporary hybridization. Morphological effects of hybridization have been investigated on the small island of Daphne Major by documenting changes in hybridizing populations of Geospiza fortis and Geospiza scandens over a 30-y period. G. scandens showed more evidence of admixture than G. fortis. Beaks of G. scandens became progressively blunter, and while variation in length increased, variation in depth decreased. These changes imply independent effects of introgression on 2, genetically correlated, beak dimensions. Our study shows how introgressive hybridization can alter ecologically important traits, increase morphological variation as a radiation proceeds, and enhance the potential for future evolution in changing environments.

scholarly journals Triad hybridization via a conduit species

2020 ◽  
Vol 117 (14) ◽  
pp. 7888-7896 ◽  
Author(s):  
Peter R. Grant ◽  
B. Rosemary Grant
Keyword(s):  
Introgressive Hybridization ◽  
Term Study ◽  
Future Evolution ◽  
Standing Variation ◽  
Long Term Study ◽  
Novel Traits ◽  
Adaptive Radiations ◽  
Geospiza Fortis ◽  
And Behavior

Introgressive hybridization can affect the evolution of populations in several important ways. It may retard or reverse divergence of species, enable the development of novel traits, enhance the potential for future evolution by elevating levels of standing variation, create new species, and alleviate inbreeding depression in small populations. Most of what is known of contemporary hybridization in nature comes from the study of pairs of species, either coexisting in the same habitat or distributed parapatrically and separated by a hybrid zone. More rarely, three species form an interbreeding complex (triad), reported in vertebrates, insects, and plants. Often, one species acts as a genetic link or conduit for the passage of genes (alleles) between two others that rarely, if ever, hybridize. Demographic and genetic consequences are unknown. Here we report results of a long-term study of interbreeding Darwin’s finches on Daphne Major island, Galápagos.Geospiza fortisacted as a conduit for the passage of genes between two others that have never been observed to interbreed on Daphne:Geospiza fuliginosa, a rare immigrant, andGeospiza scandens, a resident. Microsatellite gene flow fromG. fortisintoG. scandensincreased in frequency during 30 y of favorable ecological conditions, resulting in genetic and morphological convergence.G. fortis,G. scandens, and the derived dihybrids and trihybrids experienced approximately equal fitness. Especially relevant to young adaptive radiations, where species differ principally in ecology and behavior, these findings illustrate how new combinations of genes created by hybridization among three species can enhance the potential for evolutionary change.

scholarly journals Conspecific versus heterospecific gene exchange between populations of Darwin's finches

2010 ◽  
Vol 365 (1543) ◽  
pp. 1065-1076 ◽  
Author(s):  
Peter R. Grant ◽  
B. Rosemary Grant
Keyword(s):  
Gene Flow ◽  
Introgressive Hybridization ◽  
Small Island ◽  
Gene Exchange ◽  
Darwin's Finches ◽  
Galapagos Archipelago ◽  
Darwin’S Finches ◽  
Large Populations ◽  
Geospiza Fortis ◽  
Neighbouring Island

This study addresses the extent and consequences of gene exchange between populations of Darwin's finches. Four species of ground finches ( Geospiza ) inhabit the small island of Daphne Major in the centre of the Galápagos archipelago. We undertook a study of microsatellite DNA variation at 16 loci in order to quantify gene flow within species owing to immigration and between species owing to hybridization. A combination of pedigrees of observed breeders and assignments of individuals to populations by the program S tructure enabled us to determine the frequency of gene exchange and the island of origin of immigrants in some cases. The relatively large populations of Geospiza fortis and G. scandens receive conspecific immigrants at a rate of less than one per generation. They exchange genes more frequently by rare but repeated hybridization. Effects of heterospecific gene flow from hybridization are not counteracted by lower fitness of the offspring. As a result, the standing genetic variation of the two main resident populations on Daphne Major is enhanced to a greater extent by introgressive hybridization than through breeding with conspecific immigrants. Immigrant G. fuliginosa also breeds with G. fortis . Conspecific immigration was highest in the fourth species, G. magnirostris . This species is much larger than the other three and perhaps for this reason it has not bred with any of them. The source island of most immigrants is probably the neighbouring island of Santa Cruz. Evolutionary change may be inhibited in G. magnirostris by continuing gene flow, but enhanced in G. fortis and G. scandens by introgressive hybridization.

scholarly journals Adaptive radiation and hybridization in Wallace's Dreamponds: evidence from sailfin silversides in the Malili Lakes of Sulawesi

2006 ◽  
Vol 273 (1598) ◽  
pp. 2209-2217 ◽  
Author(s):  
Fabian Herder ◽  
Arne W Nolte ◽  
Jobst Pfaender ◽  
Julia Schwarzer ◽  
Renny K Hadiaty ◽  
...  
Keyword(s):  
New Species ◽  
Adaptive Radiation ◽  
Introgressive Hybridization ◽  
Reticulate Evolution ◽  
Species Group ◽  
Potential Force ◽  
Major Interest ◽  
Key Factor ◽  
Adaptive Radiations ◽  
Malili Lakes

Adaptive radiations are extremely useful to understand factors driving speciation. A challenge in speciation research is to distinguish forces creating novelties and those relevant to divergence and adaptation. Recently, hybridization has regained major interest as a potential force leading to functional novelty and to the genesis of new species. Here, we show that introgressive hybridization is a prominent phenomenon in the radiation of sailfin silversides (Teleostei: Atheriniformes: Telmatherinidae) inhabiting the ancient Malili Lakes of Sulawesi, correlating conspicuously with patterns of increased diversity. We found the most diverse lacustrine species-group of the radiation to be heavily introgressed by genotypes originating from streams of the lake system, an effect that has masked the primary phylogenetic pattern of the flock. We conclude that hybridization could have acted as a key factor in the generation of the flock's spectacular diversity. To our knowledge, this is the first empirical evidence for massive reticulate evolution within a complex animal radiation.

Long and short time evolution of deep seated gravitational slope deformation: contribution to knowledge of phenomena for the management of alea in the Alpine mountains

2020 ◽  
Author(s):  
Clément Boivin
Keyword(s):  
Time Evolution ◽  
Slope Deformation ◽  
Tectonic Activity ◽  
High Mountain ◽  
Mountain Range ◽  
Short Term ◽  
Future Evolution ◽  
Short Time ◽  
Short Time Evolution

<p>"LONG AND SHORT TIME EVOLUTION OF DEEP SEATED GRAVITATIONAL SLOPE DEFORMATION: CONTRIBUTION TO KNOWLEDGE OF PHENOMENA FOR THE MANAGEMENT OF ALEA IN THE ALPINE MOUNTAINS"</p><p> </p><p>C.Boivin <sup>a</sup>, J.P. Malet <sup>a</sup>, C. Bertrand <sup>b</sup>, F. Chabaux <sup>c</sup>, J. van der Woerd <sup>a</sup>, Y. Thiery <sup>d</sup>, F. Lacquement <sup>d</sup></p><p><sup>a  </sup>Institut de Physique du Globe de Strasbourg – IPGS/DA - UMR 7516 CNRS-Unistra</p><p><sup>b </sup> Laboratoire Chrono-Environnement – LCE / UMR 6249 CNRS – UFC</p><p><sup>c</sup>  Laboratoire d’Hydrologie et de Géochimie de Strasbourg – BISE / UMR 7517 – Unistra</p><p><sup>d</sup>  Bureau de Recherches Géologiques et Minières</p><p> </p><p>          The <strong>Deep Seated Gravitational Slope Deformation (DSGSD)</strong> are defined like a set of rock mass characterized by a generally slow movement and which can affect all the slopes of a valley or a mountain range (Agliardi and al., 2001, 2009; Panek and Klimes., 2016). The DSGSD is identified in many mountains (ex: Alps, Alaska, Rocky Mountains, Andes…) and it can affect both isolated low relief and very high mountain ranges (Panek and Klimes., 2016). This deep instability are identified in many case like the origin zone for important landslide like the example of La Clapière landslide in the Alpes Maritimes (Bigot-Cormier et al., 2005). The DSGSD represent an important object we must understand to anticipate catastrophic landslides.</p><p>          Actually, many factors that could be at the origin or controlling the evolution of DSGSD have been identified such as for example the structural heritage, the climate or the tectonic activity (Agliardi 2000; 2009; 2013; Jomard 2006; Sanchez et al., 2009; Zorzi et al., 2013; Panek and Klimes., 2016; Ostermann and Sanders., 2017; Blondeau 2018). The long-term and short-term evolution of DSGSD is still poorly understood but represents an important point to characterize in order to predict future major landslides. A first inventory of DSGSD began to be carried out by certain studies such as Blondeau 2018 or Crosta et al 2013 in the Alps. These same studies have also started to prioritize the factors controlling the evolution of DSGSD.</p><p>          It is in order to better understand the short-term (<100 years) and long-term (> 100 years) evolution of the DSGSD of the French Alpine massifs and the link with the occurrence of landslides, that this thesis project is developed. The main objective of this project, will be proposed models of the evolution of DSGSD since the last glaciations. But also to propose key interpretations of the future evolution to locate the areas likely to initiate landslides. Two study areas in the French Alpine massifs were chosen because they represent areas of referencing and localization gaps in DSGSD: Beaufortain and Queyras. They have the advantage of having a low lithological diversity making it possible to simplify the identification of the factors influencing the evolution of DSGSD. A geomorphological analysis on satellite data and on the ground is carried out to locate the DSGSD. Several dating (<sup>14</sup>C, <sup>10</sup>Be or <sup>36</sup>Cl) will be carried out to reconstruct the history of these objects and understand the factors that controlled their evolution.</p>

scholarly journals Reproductive isolation of hybrid populations driven by genetic incompatibilities

2014 ◽  
Author(s):  
Molly Schumer ◽  
Rongfeng Cui ◽  
Gil G Rosenthal ◽  
Peter Andolfatto
Keyword(s):  
Reproductive Isolation ◽  
Alternative Model ◽  
Parental Species ◽  
Small Population ◽  
Hybrid Population ◽  
Ecological Niches ◽  
Simple Consequence ◽  
Hybrid Species ◽  
Population Sizes ◽  
Adaptive Radiations

Despite its role in homogenizing populations, hybridization has also been proposed as a means to generate new species. The conceptual basis for this idea is that hybridization can result in novel phenotypes through recombination between the parental genomes, allowing a hybrid population to occupy ecological niches unavailable to parental species. A key feature of these models is that these novel phenotypes ecologically isolate hybrid populations from parental populations, precipitating speciation. Here we present an alternative model of the evolution of reproductive isolation in hybrid populations that occurs as a simple consequence of selection against incompatibilities. Unlike previous models, our model does not require small population sizes, the availability of new niches for hybrids or ecological or sexual selection on hybrid traits. We show that reproductive isolation between hybrids and parents evolves frequently and rapidly under this model, even in the presence of ongoing migration with parental species and strong selection against hybrids. Our model predicts that multiple distinct hybrid species can emerge from replicate hybrid populations formed from the same parental species, potentially generating patterns of species diversity and relatedness that mimic adaptive radiations.

scholarly journals Why are There so Many Bee-Orchid Species? Adaptive Radiation by Intraspecific Competition for Mnemonic Pollinators

2019 ◽  
Author(s):  
Michel Baguette ◽  
Joris Bertrand ◽  
Virginie M. Stevens ◽  
Bertrand Schatz
Keyword(s):  
Adaptive Radiation ◽  
Evolutionary Dynamics ◽  
Evolutionary Relationship ◽  
Ecological Niches ◽  
Local Diversity ◽  
Pollinator Species ◽  
Main Driver ◽  
Adaptive Radiations ◽  
Suitable Habitats ◽  
Species Specific

Adaptive radiations occur mostly in response to environmental variation through the evolution of key eco-morphological innovations that allow emerging species to occupy new ecological niches. However, rapid phenotypic evolution and the evolution of key novelties are likely to also occur when a couple or few species are engaged into narrow ecological interactions. To demonstrate coevolution is a difficult task; only elusive evidences confirm that coevolution is a driver of speciation and diversification. Here we propose that the adaptive radiation of the Mediterranean orchid genus Ophrys, which gave rise to ca. 350 species since the apparition of the genus is due to the particular co-evolutionary dynamics between these plants and their pollinators. We suggest that the pollination by sexual swindle used by Ophrys orchids is the main driver of this coevolution. Flowers of each Ophrys species mimic sexually receptive females of one particular insect species, mainly bees. Male bees are attracted by pseudo-pheromones emitted by Ophrys flowers that are similar to the sexual pheromones of their females. Males lured by the flower shape, color and hairiness attempt to copulate with the flower, which glues pollen on their bodies. Pollen is eventually transferred to the stigma of another flower of the same Ophrys species during similar copulation attempts. Three observations led us to propose the scenario of an asymmetric co-evolutionary relationship between Ophrys and their pollinators. Firstly, there is a strong intra-specific competition among Ophrys individuals for the attraction of their species-specific pollinators, which is due to the high learning and memorization abilities of bees that record the pheromone signatures of kin or of previously courted partner to avoid (further) copulation attempts. Mnemonic pollinators induce thus a strong selective pressure for variation in the pseudo-pheromones emitted by individual flowers, which will potentially generate shifts in pollinator species, and hence Ophrys speciation. These pollinator shifts are adaptive for new Ophrys species because they may benefit from a competitor-free space. Secondly, such shifts in pollinator species are due to the random crossing of peaks in the olfactory landscape of the pollinator guild that is syntopic to each particular Ophrys population. This selective process on individual, random variation in pseudo-pheromone bouquets is followed by directional selection on flower phenotypes that will reinforce the attraction of the new pollinator. Thirdly, pollinators use the pseudo-pheromones emitted by Ophrys to locate suitable habitats from a distance within complex landscapes. Pollinators stay fixed for a while in these habitats by the local diversity of pseudo-pheromones, which increases their probability of encounter with a receptive female and hence the reproduction probability of both sexes. Conversely, pollinators disperse out of small suitable habitats once they have memorized the local diversity of sexual pseudo-pheromone bouquet or if fecundated Ophrys flowers repel pollinators, which decreases the probability of geitonogamy (plant advantage) but limit pollinator mating with locally emergent insect females, thus limiting inbreeding and favoring gene flow (pollinator advantage). Finally, we propose several research avenues that emerged according to this scenario of adaptive radiation by assymetric coevolution between Ophrys species and their pollinators.

scholarly journals Morphological ghosts of introgression in Darwin’s finch populations

2021 ◽  
Vol 118 (31) ◽  
pp. e2107434118
Author(s):  
Peter R. Grant ◽  
B. Rosemary Grant
Keyword(s):  
Evolutionary History ◽  
Genomic Data ◽  
Evolutionary Divergence ◽  
Gene Exchange ◽  
Future Evolution ◽  
Large Form ◽  
Large Samples ◽  
As Species ◽  
History Of ◽  
Geospiza Fortis

Many species of plants, animals, and microorganisms exchange genes well after the point of evolutionary divergence at which taxonomists recognize them as species. Genomes contain signatures of past gene exchange and, in some cases, they reveal a legacy of lineages that no longer exist. But genomic data are not available for many organisms, and particularly problematic for reconstructing and interpreting evolutionary history are communities that have been depleted by extinctions. For these, morphology may substitute for genes, as exemplified by the history of Darwin’s finches on the Galápagos islands of Floreana and San Cristóbal. Darwin and companions collected seven specimens of a uniquely large form of Geospiza magnirostris in 1835. The populations became extinct in the next few decades, partly due to destruction of Opuntia cactus by introduced goats, whereas Geospiza fortis has persisted to the present. We used measurements of large samples of G. fortis collected for museums in the period 1891 to 1906 to test for unusually large variances and skewed distributions of beak and body size resulting from introgression. We found strong evidence of hybridization on Floreana but not on San Cristóbal. The skew is in the direction of the absent G. magnirostris. We estimate introgression influenced 6% of the frequency distribution that was eroded by selection after G. magnirostris became extinct on these islands. The genetic residuum of an extinct species in an extant one has implications for its future evolution, as well as for a conservation program of reintroductions in extinction-depleted communities.

scholarly journals Possible human impacts on adaptive radiation: beak size bimodality in Darwin's finches

2006 ◽  
Vol 273 (1596) ◽  
pp. 1887-1894 ◽  
Author(s):  
Andrew P Hendry ◽  
Peter R Grant ◽  
B Rosemary Grant ◽  
Hugh A Ford ◽  
Mark J Brewer ◽  
...  
Keyword(s):  
Adaptive Radiation ◽  
Human Activities ◽  
Human Impacts ◽  
Adaptive Landscape ◽  
Hybrid Fitness ◽  
Evolutionary Diversification ◽  
Adaptive Landscapes ◽  
Adaptive Radiations ◽  
Geospiza Fortis ◽  
Beak Size

Adaptive radiation is facilitated by a rugged adaptive landscape, where fitness peaks correspond to trait values that enhance the use of distinct resources. Different species are thought to occupy the different peaks, with hybrids falling into low-fitness valleys between them. We hypothesize that human activities can smooth adaptive landscapes, increase hybrid fitness and hamper evolutionary diversification. We investigated this possibility by analysing beak size data for 1755 Geospiza fortis measured between 1964 and 2005 on the island of Santa Cruz, Galápagos. Some populations of this species can display a resource-based bimodality in beak size, which mirrors the greater beak size differences among species. We first show that an historically bimodal population at one site, Academy Bay, has lost this property in concert with a marked increase in local human population density. We next show that a nearby site with lower human impacts, El Garrapatero, currently manifests strong bimodality. This comparison suggests that bimodality can persist when human densities are low (Academy Bay in the past, El Garrapatero in the present), but not when they are high (Academy Bay in the present). Human activities may negatively impact diversification in ‘young’ adaptive radiations, perhaps by altering adaptive landscapes.

scholarly journals Fission and fusion of Darwin's finches populations

2008 ◽  
Vol 363 (1505) ◽  
pp. 2821-2829 ◽  
Author(s):  
B.Rosemary Grant ◽  
Peter R Grant
Keyword(s):  
Introgressive Hybridization ◽  
Sympatric Species ◽  
Small Island ◽  
Song Type ◽  
Recent Past ◽  
Galapagos Archipelago ◽  
Beak Shape ◽  
History Of ◽  
Evolutionary Consequences ◽  
Species Hybrids

This study addresses the causes and evolutionary consequences of introgressive hybridization in the sympatric species of Darwin's ground finches ( Geospiza ) on the small island of Daphne Major in the Galápagos archipelago. Hybridization occurs rarely (less than 2% of breeding pairs) but persistently across years, usually as a result of imprinting on the song of another species. Hybrids survive well under some ecological conditions, but not others. Hybrids mate according to song type. The resulting introgression increases phenotypic and genetic variation in the backcrossed populations. Effects of introgression on beak shape are determined by the underlying developmental genetic pathways. Introgressive hybridization has been widespread throughout the archipelago in the recent past, and may have been a persistent feature throughout the early history of the radiation, episodically affecting both the speed and direction of evolution. We discuss how fission through selection and fusion through introgression in contemporary Darwin's finch populations may be a reflection of processes occurring in other young radiations. We propose that introgression has the largest effect on the evolution of interbreeding species after they have diverged in morphology, but before the point is reached when genetic incompatibilities incur a severe fitness cost.

scholarly journals A key metabolic gene for recurrent freshwater colonization and radiation in fishes

Science ◽  
2019 ◽  
Vol 364 (6443) ◽  
pp. 886-889 ◽  
Author(s):  
Asano Ishikawa ◽  
Naoki Kabeya ◽  
Koki Ikeya ◽  
Ryo Kakioka ◽  
Jennifer N. Cech ◽  
...  
Keyword(s):  
Fatty Acid ◽  
Fatty Acid Desaturase ◽  
Ecological Niches ◽  
Desaturase Gene ◽  
Genomic Analyses ◽  
Freshwater Habitats ◽  
Adaptive Radiations ◽  
Close Relatives ◽  
Transgenic Manipulation ◽  
Do So

Colonization of new ecological niches has triggered large adaptive radiations. Although some lineages have made use of such opportunities, not all do so. The factors causing this variation among lineages are largely unknown. Here, we show that deficiency in docosahexaenoic acid (DHA), an essential ω-3 fatty acid, can constrain freshwater colonization by marine fishes. Our genomic analyses revealed multiple independent duplications of the fatty acid desaturase gene Fads2 in stickleback lineages that subsequently colonized and radiated in freshwater habitats, but not in close relatives that failed to colonize. Transgenic manipulation of Fads2 in marine stickleback increased their ability to synthesize DHA and survive on DHA-deficient diets. Multiple freshwater ray-finned fishes also show a convergent increase in Fads2 copies, indicating its key role in freshwater colonization.

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