scholarly journals Habitat Choice and Speciation

2012 ◽  
Vol 2012 ◽  
pp. 1-12 ◽  
Author(s):  
Sophie E. Webster ◽  
Juan Galindo ◽  
John W. Grahame ◽  
Roger K. Butlin
Keyword(s):  
Reproductive Isolation ◽  
Local Adaptation ◽  
Ecological Speciation ◽  
Habitat Choice ◽  
Current Evidence ◽  
Evolutionary Mechanisms ◽  
Important Challenge ◽  
Intertidal Gastropod ◽  
Underlying Mechanisms

The role of habitat choice in reproductive isolation and ecological speciation has often been overlooked, despite acknowledgement of its ability to facilitate local adaptation. It can form part of the speciation process through various evolutionary mechanisms, yet where habitat choice has been included in models of ecological speciation little thought has been given to these underlying mechanisms. Here, we propose and describe three independent criteria underlying ten different evolutionary scenarios in which habitat choice may promote or maintain local adaptation. The scenarios are the result of all possible combinations of the independent criteria, providing a conceptual framework in which to discuss examples which illustrate each scenario. These examples show that the different roles of habitat choice in ecological speciation have rarely been effectively distinguished. Making such distinctions is an important challenge for the future, allowing better experimental design, stronger inferences and more meaningful comparisons among systems. We show some of the practical difficulties involved by reviewing the current evidence for the role of habitat choice in local adaptation and reproductive isolation in the intertidal gastropodLittorina saxatilis, a model system for the study of ecological speciation, assessing whether any of the proposed scenarios can be reliably distinguished, given current research.

scholarly journals Sympatric, parapatric or allopatric: the most important way to classify speciation?

2008 ◽  
Vol 363 (1506) ◽  
pp. 2997-3007 ◽  
Author(s):  
Roger K Butlin ◽  
Juan Galindo ◽  
John W Grahame
Keyword(s):  
Reproductive Isolation ◽  
Local Adaptation ◽  
Genetic Basis ◽  
Environmental Gradients ◽  
Sympatric Speciation ◽  
Model System ◽  
Littorina Saxatilis ◽  
The Past ◽  
Intertidal Gastropod

The most common classification of modes of speciation begins with the spatial context in which divergence occurs: sympatric, parapatric or allopatric. This classification is unsatisfactory because it divides a continuum into discrete categories, concentrating attention on the extremes, and it subordinates other dimensions on which speciation processes vary, such as the forces driving differentiation and the genetic basis of reproductive isolation. It also ignores the fact that speciation is a prolonged process that commonly has phases in different spatial contexts. We use the example of local adaptation and partial reproductive isolation in the intertidal gastropod Littorina saxatilis to illustrate the inadequacy of the spatial classification of speciation modes. Parallel divergence in shell form in response to similar environmental gradients in England, Spain and Sweden makes this an excellent model system. However, attempts to demonstrate ‘incipient’ and ‘sympatric’ speciation involve speculation about the future and the past. We suggest that it is more productive to study the current balance between local adaptation and gene flow, the interaction between components of reproductive isolation and the genetic basis of differentiation.

scholarly journals Local adaptation and sexual selection drive intra-island diversification in a songbird lineage: differential divergence in autosomes and sex chromosomes

2018 ◽  
Author(s):  
Yann XC Bourgeois ◽  
Joris AM Bertrand ◽  
Boris Delahaie ◽  
Hélène Holota ◽  
Christophe Thébaud ◽  
...  
Keyword(s):  
Sexual Selection ◽  
Natural Selection ◽  
Reproductive Isolation ◽  
Local Adaptation ◽  
Sex Chromosomes ◽  
Genomic Variation ◽  
Color Variation ◽  
Mating Signals ◽  
Genome Wide

AbstractRecently diverged taxa showing marked phenotypic and ecological diversity are optimal systems to test the relative importance of two major evolutionary mechanisms, adaptation to local ecological conditions by natural selection, or mechanisms of reproductive isolation such as assortative mating mediated by sexually selected mating signals or post-zygotic incompatibilities. Whereas local adaptation is expected to affect many loci throughout the genome, traits acting as mating signals are expected to be located on sex chromosomes and have a simple genetic basis. We used genome-wide markers to test these predictions in Reunion Island’s gray-white eye (Zosterops borbonicus), which has recently diversified into five distinct plumage forms. Two of them correspond to a polymorphic highland population that is separated by a steep ecological gradient from three distinct lowland forms that show narrow contact zones in plumage color traits, yet no association with environmental variables. An analysis of population structure using genome-wide SNP loci revealed two major clades corresponding to highland and lowland forms, respectively, with the latter separated further into three independent lineages corresponding to plumage forms. Coalescent tests of alternative demographic scenarios provided support for divergence of highland and lowland lineages with an intensification of gene flow in the last 60,000 years. Landscapes of genomic variation revealed that signatures of selection associated with elevation are found at multiple regions across the genome, whereas most loci associated with the lowland forms are located on the Z sex chromosome. A gene ontology analysis identified TYRP1, a Z-linked color gene, as a likely candidate locus underlying color variation among lowland forms. Our results are consistent with the role of natural selection in driving the divergence of locally adapted highland populations, and the role of sexual selection in differentiating lowland forms through reproductive isolation mechanisms, showing that both modes of lineage divergence can take place at very small geographic scales in birds.

scholarly journals No evidence for genetic differentiation in juvenile traits between Belgian and French populations of the invasive tree Robinia pseudoacacia

2018 ◽  
Vol 151 (1) ◽  
pp. 5-17 ◽  
Author(s):  
Xavier P. Bouteiller ◽  
Frédéric Barraquand ◽  
Pauline Garnier-Géré ◽  
Noémie Harmand ◽  
Yec’han Laizet ◽  
...  
Keyword(s):  
Life History ◽  
Genetic Differentiation ◽  
Local Adaptation ◽  
Life History Traits ◽  
Genetic Interaction ◽  
Robinia Pseudoacacia ◽  
Neutral Evolution ◽  
Evolutionary Mechanisms ◽  
Invasive Tree

Background – The role of evolution in biological invasion studies is often overlooked. In order to evaluate the evolutionary mechanisms behind invasiveness, both quantitative and population genetics studies are underway on Robinia pseudoacacia L., one of the worst invasive tree species in Europe.Methods – A controlled experiment was set up using 2000 seeds from ten populations in Southern France and ten populations in Belgium. Seedlings were cultivated in two climatic chambers set at 18°C and 22°C. Early development life history traits (e.g. seedling phenology) and functional traits (e.g. growth rates) were monitored. Genotyping using SNP markers was used to evaluate the genetic differentiation among the populations and a QST – FST comparison was done in order to test for the role of selection.Results – Populations exhibited a strong plasticity to temperature for all measured traits, the warmer environment being generally more suitable, irrespective of their origin. No significant departure from neutral evolution was evidenced by the QST – FST comparisons, although we found a slightly significant differentiation at the molecular level. Conclusion – Plasticity for the functional and life history traits was evidenced but no genetic interaction suggesting no possible evolution of plasticity at those traits. Moreover, no support for genetic differentiation and local adaptation was found among studied populations within invasive range, raising two main questions: first, what is the role of selection on functional and life-history traits; and second, is the elapsed time since first introduction sufficient to allow evolution and local adaptation?

scholarly journals The Role of Parasitism in Adaptive Radiations—When Might Parasites Promote and When Might They Constrain Ecological Speciation?

2012 ◽  
Vol 2012 ◽  
pp. 1-20 ◽  
Author(s):  
Anssi Karvonen ◽  
Ole Seehausen
Keyword(s):  
Reproductive Isolation ◽  
Parasite Species ◽  
Ecological Speciation ◽  
Divergent Selection ◽  
Divergent Evolution ◽  
Selective Agents ◽  
Adaptive Radiations ◽  
Recurrent Patterns ◽  
Single Versus

Research on speciation and adaptive radiation has flourished during the past decades, yet factors underlying initiation of reproductive isolation often remain unknown. Parasites represent important selective agents and have received renewed attention in speciation research. We review the literature on parasite-mediated divergent selection in context of ecological speciation and present empirical evidence for three nonexclusive mechanisms by which parasites might facilitate speciation: reduced viability or fecundity of immigrants and hybrids, assortative mating as a pleiotropic by-product of host adaptation, and ecologically-based sexual selection. We emphasise the lack of research on speciation continuums, which is why no study has yet made a convincing case for parasite driven divergent evolution to initiate the emergence of reproductive isolation. We also point interest towards selection imposed by single versus multiple parasite species, conceptually linking this to strength and multifariousness of selection. Moreover, we discuss how parasites, by manipulating behaviour or impairing sensory abilities of hosts, may change the form of selection that underlies speciation. We conclude that future studies should consider host populations at variable stages of the speciation process, and explore recurrent patterns of parasitism and resistance that could pinpoint the role of parasites in imposing the divergent selection that initiates ecological speciation.

Exercise is Medicine for the Aging Brain

2017 ◽  
Vol 6 (1) ◽  
pp. 22-29 ◽  
Author(s):  
Teresa Liu-Ambrose ◽  
John R. Best
Keyword(s):  
Physical Activity ◽  
Older Adults ◽  
Target Population ◽  
Current Evidence ◽  
Lifestyle Factor ◽  
Aging Brain ◽  
Cognitive Health ◽  
Modifying Factors ◽  
Underlying Mechanisms

Cognitive decline is a common feature of aging. Physical activity is a modifiable lifestyle factor that has been identified as positively impacting cognitive health of older adults. Here, we review the current evidence from epidemiological (i.e., longitudinal cohort) and intervention studies on the role of physical activity and exercise in promoting cognitive health in older adults both with and without cognitive impairment. We highlight some of the potential underlying mechanisms and discuss some of the potential modifying factors, including exercise type and target population, by reviewing recent converging behavioral, neuroimaging, and biomarker evidence linking physical activity with cognitive health. We conclude with limitations and future directions for this rapidly expanding line of research.

scholarly journals Ecological Adaptation and Speciation: The Evolutionary Significance of Habitat Avoidance as a Postzygotic Reproductive Barrier to Gene Flow

2012 ◽  
Vol 2012 ◽  
pp. 1-15 ◽  
Author(s):  
Jeffrey L. Feder ◽  
Scott P. Egan ◽  
Andrew A. Forbes
Keyword(s):  
Gene Flow ◽  
Avoidance Behavior ◽  
Ecological Speciation ◽  
Habitat Choice ◽  
Model Systems ◽  
Current Evidence ◽  
Evolutionary Significance ◽  
Population Divergence ◽  
Phytophagous Insects ◽  
Habitat Avoidance

Habitat choice is an important component of most models of ecologically based speciation, especially when population divergence occurs in the face of gene flow. We examine how organisms choose habitats and ask whether avoidance behavior plays an important role in habitat choice, focusing on host-specific phytophagous insects as model systems. We contend that when a component of habitat choice involves avoidance, there can be repercussions that can have consequences for enhancing the potential for specialization and postzygotic reproductive isolation and, hence, for ecological speciation. We discuss theoretical and empirical reasons for why avoidance behavior has not been fully recognized as a key element in habitat choice and ecological speciation. We present current evidence for habitat avoidance, emphasizing phytophagous insects, and new results for parasitoid wasps consistent with the avoidance hypothesis. We conclude by discussing avenues for further study, including other potential roles for avoidance behavior in speciation related to sexual selection and reinforcement.

scholarly journals Larval Performance in the Context of Ecological Diversification and Speciation inLycaeidesButterflies

2012 ◽  
Vol 2012 ◽  
pp. 1-13 ◽  
Author(s):  
Cynthia F. Scholl ◽  
Chris C. Nice ◽  
James A. Fordyce ◽  
Zachariah Gompert ◽  
Matthew L. Forister
Keyword(s):  
Reproductive Isolation ◽  
Host Plants ◽  
Oviposition Preference ◽  
Ecological Speciation ◽  
Larval Performance ◽  
Ecological Traits ◽  
Ecological Diversification ◽  
Behavioral Traits ◽  
Plant Effects

The role of ecology in diversification has been widely investigated, though few groups have been studied in enough detail to allow comparisons of different ecological traits that potentially contribute to reproductive isolation. We investigated larval performance within a species complex ofLycaeidesbutterflies. Caterpillars from seven populations were reared on five host plants, asking if host-specific, adaptive larval traits exist. We found large differences in performance across plants and fewer differences among populations. The patterns of performance are complex and suggest both conserved traits (i.e., plant effects across populations) and more recent dynamics of local adaptation, in particular forL. melissathat has colonized an exotic host. We did not find a relationship between oviposition preference and larval performance, suggesting that preference did not evolve to match performance. Finally, we put larval performance within the context of several other traits that might contribute to ecologically based reproductive isolation in theLycaeidescomplex. This larger context, involving multiple ecological and behavioral traits, highlights the complexity of ecological diversification and emphasizes the need for detailed studies on the strength of putative barriers to gene flow in order to fully understand the process of ecological speciation.

scholarly journals Physical activity for brain health in older adults

2018 ◽  
Vol 43 (11) ◽  
pp. 1105-1112 ◽  
Author(s):  
Teresa Liu-Ambrose ◽  
Cindy K. Barha ◽  
John R. Best
Keyword(s):  
Physical Activity ◽  
Older Adults ◽  
Current Evidence ◽  
Brain Health ◽  
Future Directions ◽  
Biological Sex ◽  
Promising Strategy ◽  
Dementia Prevention ◽  
Underlying Mechanisms

Physical activity is a promising strategy for dementia prevention and disease modification. Here, we provide a narrative review of the current evidence from epidemiological and intervention studies on the role of physical activity and exercise in promoting cognitive health in older adults both without and with cognitive impairment. We highlight some of the potential underlying mechanisms and discuss biological sex as a potential moderating factor. We conclude with limitations and future directions for this rapidly expanding line of research.

scholarly journals Immunosuppression in Malaria: Do Plasmodium falciparum Parasites Hijack the Host?

Pathogens ◽  
2021 ◽  
Vol 10 (10) ◽  
pp. 1277
Author(s):  
Carlos Lamsfus Calle ◽  
Benjamin Mordmüller ◽  
Anurag Singh
Keyword(s):  
Potential Role ◽  
Cell Types ◽  
Current Evidence ◽  
Specific Cell ◽  
Different Types ◽  
Immune Defect ◽  
Underlying Mechanisms ◽  
Cellular Components ◽  
Heterologous Antigens

Malaria reflects not only a state of immune activation, but also a state of general immune defect or immunosuppression, of complex etiology that can last longer than the actual episode. Inhabitants of malaria-endemic regions with lifelong exposure to the parasite show an exhausted or immune regulatory profile compared to non- or minimally exposed subjects. Several studies and experiments to identify and characterize the cause of this malaria-related immunosuppression have shown that malaria suppresses humoral and cellular responses to both homologous (Plasmodium) and heterologous antigens (e.g., vaccines). However, neither the underlying mechanisms nor the relative involvement of different types of immune cells in immunosuppression during malaria is well understood. Moreover, the implication of the parasite during the different stages of the modulation of immunity has not been addressed in detail. There is growing evidence of a role of immune regulators and cellular components in malaria that may lead to immunosuppression that needs further research. In this review, we summarize the current evidence on how malaria parasites may directly and indirectly induce immunosuppression and investigate the potential role of specific cell types, effector molecules and other immunoregulatory factors.

Response Interference as a Mechanism Underlying Implicit Measures

2008 ◽  
Vol 24 (4) ◽  
pp. 218-225 ◽  
Author(s):  
Bertram Gawronski ◽  
Roland Deutsch ◽  
Etienne P. LeBel ◽  
Kurt R. Peters
Keyword(s):  
Task Performance ◽  
Psychological Research ◽  
Implicit Measures ◽  
Mediation Model ◽  
Response Interference ◽  
Relevant Evidence ◽  
Moderated Mediation Model ◽  
Stimulus Features ◽  
Underlying Mechanisms

Over the last decade, implicit measures of mental associations (e.g., Implicit Association Test, sequential priming) have become increasingly popular in many areas of psychological research. Even though successful applications provide preliminary support for the validity of these measures, their underlying mechanisms are still controversial. The present article addresses the role of a particular mechanism that is hypothesized to mediate the influence of activated associations on task performance in many implicit measures: response interference (RI). Based on a review of relevant evidence, we argue that RI effects in implicit measures depend on participants’ attention to association-relevant stimulus features, which in turn can influence the reliability and the construct validity of these measures. Drawing on a moderated-mediation model (MMM) of task performance in RI paradigms, we provide several suggestions on how to address these problems in research using implicit measures.

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