Testing the Predation-Diversification Hypothesis for the Cambrian—Ordovician Radiation

2016 ◽  
Vol 20 (4) ◽  
pp. 312-321 ◽  
Author(s):  
Julián Simón López-Villalta
Keyword(s):  
Diversification Hypothesis

scholarly journals Multi-modal signal evolution in birds: re-examining a standard proxy for sexual selection

2018 ◽  
Vol 285 (1889) ◽  
pp. 20181557 ◽  
Author(s):  
Christopher R. Cooney ◽  
Hannah E. A. MacGregor ◽  
Nathalie Seddon ◽  
Joseph A. Tobias
Keyword(s):  
Sexual Selection ◽  
Interspecific Interactions ◽  
Habitat Type ◽  
Negative Relationship ◽  
Key Factors ◽  
Phenotypic Data ◽  
Species Pairs ◽  
Multiple Alternative ◽  
Mating Signal ◽  
Diversification Hypothesis

Sexual selection is proposed to be an important driver of speciation and phenotypic diversification in animal systems. However, previous phylogenetic tests have produced conflicting results, perhaps because they have focused on a single signalling modality (visual ornaments), whereas sexual selection may act on alternative signalling modalities (e.g. acoustic ornaments). Here, we compile phenotypic data from 259 avian sister species pairs to assess the relationship between visible plumage dichromatism—a standard index of sexual selection in birds—and macroevolutionary divergence in the other major avian signalling modality: song. We find evidence for a strong negative relationship between the degree of plumage dichromatism and divergence in song traits, which remains significant even when accounting for other key factors, including habitat type, ecological divergence and interspecific interactions. This negative relationship is opposite to the pattern expected by a straightforward interpretation of the sexual selection–diversification hypothesis, whereby higher levels of dichromatism indicating strong sexual selection should be related to greater levels of mating signal divergence regardless of signalling modality. Our findings imply a ‘trade-off’ between the elaboration of visual ornaments and the diversification of acoustic mating signals, and suggest that the effects of sexual selection on diversification can only be determined by considering multiple alternative signalling modalities.

Ethnic origin and access to electronic health services

2016 ◽  
Vol 22 (4) ◽  
pp. 791-803 ◽  
Author(s):  
Gustavo S Mesch
Keyword(s):  
Health Care ◽  
Health Services ◽  
Health Care Services ◽  
Medical Information ◽  
Minority Groups ◽  
Ethnic Origin ◽  
Disadvantaged Groups ◽  
Care Services ◽  
Internet Users ◽  
Diversification Hypothesis

E-health holds the promise of changing the delivery of health care by extending and enhancing its reach, and democratizing and improving the access of disadvantaged groups to health care services. This study investigated ethnic inequalities in access to e-health information, communication and electronic services in Israel. Based on the diversification hypothesis, we expected that disadvantaged ethnic groups would be more likely to use e-health services to compensate for their lack of social capital. Data gathered from a representative sample of Internet users in Israel (n=1371) provided partial support for the hypothesis, indicating that in multicultural societies, disadvantaged groups are more motivated than the majority group to use the Internet to access medical information. However, despite expectations, minority groups were less likely to access e-health services. Implications of the findings are discussed.

scholarly journals Phylogeny, time divergence, and historical biogeography of the South AmericanLiolaemus alticolor-bibroniigroup (Iguania: Liolaemidae)

PeerJ ◽  
2018 ◽  
Vol 6 ◽  
pp. e4404 ◽  
Author(s):  
Sabrina N. Portelli ◽  
Andrés S. Quinteros
Keyword(s):  
A Priori ◽  
Morphological Characters ◽  
Sensu Stricto ◽  
Total Evidence ◽  
Divergence Times ◽  
The South ◽  
Distribution Ranges ◽  
Andean Uplift ◽  
Diversification Hypothesis ◽  
Relaxed Clock

The genusLiolaemuscomprises more than 260 species and can be divided in two subgenera:EulaemusandLiolaemus sensu stricto. In this paper, we present a phylogenetic analysis, divergence times, and ancestral distribution ranges of theLiolaemus alticolor-bibroniigroup (Liolaemus sensu strictosubgenus). We inferred a total evidence phylogeny combining molecular (Cytband12Sgenes) and morphological characters using Maximum Parsimony and Bayesian Inference. Divergence times were calculated using Bayesian MCMC with an uncorrelated lognormal distributed relaxed clock, calibrated with a fossil record. Ancestral ranges were estimated using the Dispersal-Extinction-Cladogenesis (DEC-Lagrange). Effects of somea prioriparameters of DEC were also tested. Distribution ranged from central Perú to southern Argentina, including areas at sea level up to the high Andes. TheL. alticolor-bibroniigroup was recovered as monophyletic, formed by two clades:L. walkeriandL. gracilis, the latter can be split in two groups. Additionally, many species candidates were recognized. We estimate that theL. alticolor-bibroniigroup diversified 14.5 Myr ago, during the Middle Miocene. Our results suggest that the ancestor of theLiolaemus alticolor-bibroniigroup was distributed in a wide area including Patagonia and Puna highlands. The speciation pattern follows the South-North Diversification Hypothesis, following the Andean uplift.

scholarly journals Revisiting the first case of insect-bacteria cospeciation: phylogenetic incongruence between aphids and their obligate endosymbiont at subfamily level

2014 ◽  
Author(s):  
Lin Liu ◽  
Xiaolei Huang ◽  
Yuan Wang ◽  
Gexia Qiao
Keyword(s):  
Common Ancestor ◽  
Horizontal Transmission ◽  
Subunit Gene ◽  
Phylogenetic Incongruence ◽  
Endosymbiotic Bacteria ◽  
First Case ◽  
Dehydrogenase Gene ◽  
Host Phylogeny ◽  
Theoretical Evidence ◽  
Diversification Hypothesis

It has been widely accepted that aphids and their primary endosymbiotic bacteria Buchnera have strictly parallel diversification relationship. As the first reported case of insect-bacteria cospeciation, this parallel diversification hypothesis has been prevalent, in spite of its basis of limited taxonomic sampling and recent doubts. Here we revisit the evolutionary relationships between aphids and Buchnera by using much more taxa and genomic data (16S rDNA, ATP synthase β-subunit gene, and gluconate-6-phosphate dehydrogenase gene) to reconstruct the Buchnera phylogeny and test its congruence with the host phylogeny. Comparisons of the Buchnera phylogeny with morphology- and molecular-based aphid phylogenies indicate phylogenetic incongruence between aphids and Buchnera at subfamily level. Current empirical and theoretical evidence indicate two potential mechanisms underlying this incongruence: one is variation in evolutionary rates of Buchnera genomes among different aphid lineages; the other is horizontal transmission of Buchnera during the radiation of extant aphid subfamilies and tribes from their common ancestor.

The Inclusion and Selection of Medicinal Plants in Traditional Pharmacopoeias—Evidence in Support of the Diversification Hypothesis

2009 ◽  
Vol 64 (1) ◽  
pp. 68-79 ◽  
Author(s):  
Nélson Leal Alencar ◽  
Thiago Antonio de Sousa Araújo ◽  
Elba Lúcia Cavalcanti de Amorim ◽  
Ulysses Paulino de Albuquerque
Keyword(s):  
Medicinal Plants ◽  
Diversification Hypothesis ◽  
Selection Of

scholarly journals Intraspecific Competition and the Promotion of Ecological Specialization

2021 ◽  
Author(s):  
Abdel H. Halloway ◽  
Joel S. Brown
Keyword(s):  
Resource Use ◽  
Intraspecific Competition ◽  
Niche Breadth ◽  
Evolutionary Model ◽  
Ecological Specialization ◽  
Secondary Resources ◽  
Cast Doubt ◽  
The Face ◽  
Game Theoretic ◽  
Diversification Hypothesis

AbstractThe evolution of ecological specialization can be summed up in a single question: why would a species evolve a more-restricted niche space? Various hypotheses have been developed to explain the promotion or suppression of ecological specialization. One hypothesis, competitive diversification, states that increased intraspecific competition will cause a population to broaden its niche breadth. With individuals alike in resource use preference, more individuals reduce the availability of preferred resources and should grant higher fitness to those that use secondary resources. However, recent studies cast doubt on this hypothesis with increased intraspecific competition reducing niche breadth in some systems. We present a game-theoretic evolutionary model showing greater ecological specialization with intraspecific competition under specific conditions. This is in contrast to the competitive diversification hypothesis. Our analysis reveals that specialization can offer a competitive advantage. Largely, when facing weak competition, more specialized individuals are able to acquire more of the preferred resources without greatly sacrificing secondary resources and therefore gain higher fitness. Only when competition is too great for an individual to significantly affect resource use will intraspecific competition lead to an increased niche breadth. Other conditions, such as a low diversity of resources and a low penalty to specialization, help promote ecological specialization in the face of intraspecific competition. Through this work, we have been able to discover a previously unseen role that intraspecific competition plays in the evolution of ecological specialization.

scholarly journals Inequality, Social Networks, and Internet Use: Exploring the Implications of the Social Diversification Hypothesis

2020 ◽  
Vol 1 (2) ◽  
pp. 1-19
Author(s):  
Eric Tsetsi ◽  
Stephen A. Rains
Keyword(s):  
Social Networks ◽  
Internet Use ◽  
Social Resources ◽  
Network Size ◽  
Disadvantaged Groups ◽  
Internet Users ◽  
The Social ◽  
Nationally Representative ◽  
Diversification Hypothesis ◽  
The Relationship

The social diversification hypothesis (SDH) suggests that in multicultural societies Internet use can help mitigate structural inequalities in access to social resources. Whereas traditionally disadvantaged groups are predicted to use the Internet to expand and diversify their social networks, advantaged groups use it to maintain existing connections. The present study investigates this central prediction of the SDH by examining the relationship between Internet and social network site (SNS) use and inequalities in network size and diversity based on race, sex, and education among a nationally representative sample of U.S. adults. The results largely contradict the SDH. Internet and SNS use were associated with greater networked-based inequalities stemming from education. The relationships between education and indicators of network size and diversity were stronger among Internet users than non-users and stronger among SNSs users than Internet-only users. Network inequalities directly related to race, sex, and education were also explored.

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