Faculty Opinions recommendation of The role of gene flow asymmetry along an environmental gradient in constraining local adaptation and range expansion.

AbstractWe study the establishment probabilities of locally adapted mutations using a multitype branching process framework. We find a surprisingly simple and intuitive analytical approximation for the establishment probabilities in a symmetric two-deme model under the assumption of weak (positive) selection. This is the first analytical closed-form approximation for arbitrary migration rate to appear in the literature. We find that the establishment probability lies between the weak and the strong migration limits if we condition the origin of the mutation to the deme where it is advantageous. This is not the case when we condition the mutation to first occur in a deme where it is disadvantageous. In this case we find that an intermediate migration rate maximizes the probability of establishment. We extend our results to the cases of multiple demes, two demes with asymmetric rates of gene flow, and asymmetric carrying capacities. The latter case allows us to illustrate how density regulation can affect establishment probabilities. Finally we use our results to investigate the role of gene flow on the rate of local adaptation and identify cases in which intermediate amounts of gene flow facilitate the rate of local adaptation as compared to two populations without gene flow.

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Assortative mating and the role of phenotypic plasticity in male competition: implications for gene flow among host-associated parasitoid populations

Biology Letters ◽

10.1098/rsbl.2008.0369 ◽

2008 ◽

Vol 4 (5) ◽

pp. 508-511 ◽

Cited By ~ 5

Author(s):

Lee M Henry

Keyword(s):

Gene Flow ◽

Phenotypic Plasticity ◽

Local Adaptation ◽

Assortative Mating ◽

Host Species ◽

Relative Size ◽

Mating Preference ◽

Adult Males ◽

Mating Preferences

Local adaptation is promoted when habitat or mating preferences reduce gene flow between populations. However, gene flow is not only a function of dispersal but also of the success of migrants in their new habitat. In this study I investigated mating preference in conjunction with phenotypic plasticity using Aphidius parasitoids adapted to different host species. Males actively attempted to assortatively mate, but actual mating outcomes were strongly influenced by the relative size of the adult males. Results are discussed in the context of assortative mating in combination with the success of migrant males in mitigating gene flow between host-associated parasitoid populations.

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Adaptive Divergence under Gene Flow along an Environmental Gradient in Two Coexisting Stickleback Species

Genes ◽

10.3390/genes12030435 ◽

2021 ◽

Vol 12 (3) ◽

pp. 435

Author(s):

Thijs M. P. Bal ◽

Alejandro Llanos-Garrido ◽

Anurag Chaturvedi ◽

Io Verdonck ◽

Bart Hellemans ◽

...

Keyword(s):

Gene Flow ◽

Brackish Water ◽

Environmental Gradient ◽

Spatial Scales ◽

Morphological Differentiation ◽

Genotyping By Sequencing ◽

Adaptive Divergence ◽

Linkage Groups ◽

Closely Related Species ◽

Genomic Patterns

There is a general and solid theoretical framework to explain how the interplay between natural selection and gene flow affects local adaptation. Yet, to what extent coexisting closely related species evolve collectively or show distinctive evolutionary responses remains a fundamental question. To address this, we studied the population genetic structure and morphological differentiation of sympatric three-spined and nine-spined stickleback. We conducted genotyping-by-sequencing and morphological trait characterisation using 24 individuals of each species from four lowland brackish water (LBW), four lowland freshwater (LFW) and three upland freshwater (UFW) sites in Belgium and the Netherlands. This combination of sites allowed us to contrast populations from isolated but environmentally similar locations (LFW vs. UFW), isolated but environmentally heterogeneous locations (LBW vs. UFW), and well-connected but environmentally heterogenous locations (LBW vs. LFW). Overall, both species showed comparable levels of genetic diversity and neutral genetic differentiation. However, for all three spatial scales, signatures of morphological and genomic adaptive divergence were substantially stronger among populations of the three-spined stickleback than among populations of the nine-spined stickleback. Furthermore, most outlier SNPs in the two species were associated with local freshwater sites. The few outlier SNPs that were associated with the split between brackish water and freshwater populations were located on one linkage group in three-spined stickleback and two linkage groups in nine-spined stickleback. We conclude that while both species show congruent evolutionary and genomic patterns of divergent selection, both species differ in the magnitude of their response to selection regardless of the geographical and environmental context.

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Premating barriers in young sympatric snail species

Scientific Reports ◽

10.1038/s41598-021-84407-2 ◽

2021 ◽

Vol 11 (1) ◽

Author(s):

Arina L. Maltseva ◽

Marina A. Varfolomeeva ◽

Arseniy A. Lobov ◽

Polina O. Tikanova ◽

Egor A. Repkin ◽

...

Keyword(s):

Gene Flow ◽

Snail Species ◽

Sympatric Populations ◽

Gastropod Species ◽

Shell Size ◽

Closely Related Species ◽

Partial Canonical Correspondence Analysis ◽

In The Wild ◽

Isolation Index

AbstractSympatric coexistence of recently diverged species raises the question of barriers restricting the gene flow between them. Reproductive isolation may be implemented at several levels, and the weakening of some, e.g. premating, barriers may require the strengthening of the others, e.g. postcopulatory ones. We analysed mating patterns and shell size of mates in recently diverged closely related species of the subgenus Littorina Neritrema (Littorinidae, Caenogastropoda) in order to assess the role of premating reproductive barriers between them. We compared mating frequencies observed in the wild with those expected based on relative densities using partial canonical correspondence analysis. We introduced the fidelity index (FI) to estimate the relative accuracy of mating with conspecific females and precopulatory isolation index (IPC) to characterize the strength of premating barriers. The species under study, with the exception of L. arcana, clearly demonstrated preferential mating with conspecifics. According to FI and IPC, L. fabalis and L. compressa appeared reliably isolated from their closest relatives within Neritrema. Individuals of these two species tend to be smaller than those of the others, highlighting the importance of shell size changes in gastropod species divergence. L. arcana males were often found in pairs with L. saxatilis females, and no interspecific size differences were revealed in this sibling species pair. We discuss the lack of discriminative mate choice in the sympatric populations of L. arcana and L. saxatilis, and possible additional mechanisms restricting gene flow between them.

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Molecular Signatures of Reticulate Evolution within the Complex of European Pine Taxa

Forests ◽

10.3390/f12040489 ◽

2021 ◽

Vol 12 (4) ◽

pp. 489

Author(s):

Bartosz Łabiszak ◽

Witold Wachowiak

Keyword(s):

Gene Flow ◽

Reticulate Evolution ◽

Modeling Framework ◽

Closely Related Species ◽

Interspecific Gene Flow ◽

Nucleotide Sequence Variation ◽

History Of ◽

Best Fitting ◽

Species Integrity

Speciation mechanisms, including the role of interspecific gene flow and introgression in the emergence of new species, are the major focus of evolutionary studies. Inference of taxonomic relationship between closely related species may be challenged by past hybridization events, but at the same time, it may provide new knowledge about mechanisms responsible for the maintenance of species integrity despite interspecific gene flow. Here, using nucleotide sequence variation and utilizing a coalescent modeling framework, we tested the role of hybridization and introgression in the evolutionary history of closely related pine taxa from the Pinus mugo complex and P. sylvestris. We compared the patterns of polymorphism and divergence between taxa and found a great overlap of neutral variation within the P. mugo complex. Our phylogeny reconstruction indicated multiple instances of reticulation events in the past, suggesting an important role of interspecific gene flow in the species divergence. The best-fitting model revealed P. mugo and P. uncinata as sister species with basal P. uliginosa and asymmetric migration between all investigated species after their divergence. The magnitude of interspecies gene flow differed greatly, and it was consistently stronger from representatives of P. mugo complex to P. sylvestris than in the opposite direction. The results indicate the prominent role of reticulation evolution in those forest trees and provide a genetic framework to study species integrity maintained by selection and local adaptation.

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Rhinocerotidae from the early Miocene of the Negev (Israel) and implications for the dispersal of early Neogene rhinoceroses

Journal of Paleontology ◽

10.1017/jpa.2021.64 ◽

2021 ◽

pp. 1-12

Author(s):

Luca Pandolfi ◽

Ran Calvo ◽

Ari Grossman ◽

Rivka Rabinovich

Keyword(s):

Southeast Asia ◽

South Asian ◽

North Africa ◽

Range Expansion ◽

New Records ◽

Ct Scanning ◽

Early Miocene ◽

Early Neogene ◽

Postcranial Remains

Abstract A revision of the rhinocerotid material from the Negev (Israel), dating back to the early Miocene (MN3 in the European Mammal Biochronology), highlights the presence of Brachypotherium and a taxon close to Gaindatherium in the Levantine corridor. A juvenile mandible, investigated using CT scanning, displays morphologically distinct characters consistent with Brachypotherium cf. B. snowi rather than with other Eurasian representatives of this genus. Some postcranial remains from the Negev, such as a humerus, display features that distinguish it among Miocene taxa. We attribute these postcrania to cf. Gaindatherium sp., a taxon never recorded outside the Siwaliks until now. This taxon dispersed into the Levantine region during the late early Miocene, following a pattern similar to other South Asian taxa. Brachypotherium cf. B. snowi probably occurred in the Levantine region and then in North Africa during the early Miocene because its remains are known from slightly younger localities such as Moghara (Egypt) and Jebel Zelten (Libya). The occurrence cf. Gaindatherium sp. represents a previously unrecorded range expansion out of Southeast Asia. These new records demonstrate the paleogeographic importance of the Levantine region showcasing the complex role of the Levantine corridor in intercontinental dispersals between Asia and Europe as well as Eurasia and Africa.

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

Biological Journal of the Linnean Society ◽

10.1093/biolinnean/blz129 ◽

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.

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