Toxic hydrogen sulphide and dark caves: pronounced male life-history divergence among locally adapted Poecilia mexicana (Poeciliidae)

Chronic environmental stress is known to induce evolutionary change. Here, we assessed male life‐history trait divergence in the neotropical fish Poecilia mexicana from a system that has been described to undergo incipient ecological speciation in adjacent, but reproductively isolated toxic/nontoxic and surface/cave habitats. Examining both field‐caught and common garden–reared specimens, we investigated the extent of differentiation and plasticity of life‐history strategies employed by male P. mexicana. We found strong site‐specific life‐history divergence in traits such as fat content, standard length and gonadosomatic index. The majority of site‐specific life‐history differences were also expressed under common garden–rearing conditions. We propose that apparent conservatism of male life histories is the result of other (genetically based) changes in physiology and behaviour between populations. Together with the results from previous studies, this is strong evidence for local adaptation as a result of ecologically based divergent selection.     

The genetical theory of kin selection

Natural selection operates both directly, via the impact of a trait upon the individual's own fitness, and indirectly, via the impact of the trait upon the fitness of the individual's genetically related social partners. These effects are often framed in terms of Hamilton's rule, rb - c > 0, which provides the central result of social-evolution theory. However, a number of studies have questioned the generality of Hamilton's rule, suggesting that it requires restrictive assumptions. Here, we use Fisher's genetical paradigm to demonstrate the generality of Hamilton's rule and to clarify links between different studies. We show that confusion has arisen owing to researchers misidentifying model parameters with the b and c terms in Hamilton's rule, and misidentifying measures of genotypic similarity or genealogical relationship with the coefficient of genetic relatedness, r. More generally, we emphasize the need to distinguish between general kin-selection theory that forms the foundations of social evolution, and streamlined kin-selection methodology that is used to solve specific problems.     

Association of Mc1r variants with ecologically relevant phenotypes in the European ocellated lizard, Lacerta lepida

A comprehensive knowledge on the genetic basis of coloration is crucial to understand how new colour phenotypes arise and how they contribute to the emergence of new species. Variation in melanocortin‐1 receptor (Mc1r), a gene that has been reported as a target for repeated evolution in a wide range of vertebrate taxa, was assessed in European ocellated lizards (Lacerta lepida) to search for associations with melanin‐based colour phenotypes. Lacerta lepida subspecies’ distribution is associated with the three major bio‐climatic regions in the Iberian Peninsula. A nonconserved and derived substitution (T162I) was associated with the L. l. nevadensis phenotype (prevalence of brown scales). Another substitution (S172C) was associated with the presence of black scales in both L. l. lepida and L. l. iberica, but no mutations were found to be associated with the higher proportion of black in L. l. iberica. Extensive genotyping of Mc1r along the contact zone between L. l. nevadensis and L. l. lepida revealed low gene flow (only two hybrids detected). The implications of these findings are discussed in the context of previous knowledge about the evolutionary history of ocellated lizards.     

Patterns of cranial shape diversification during the phylogenetic branching process of New World monkeys (Primates: Platyrrhini)

One of the central topics in evolutionary biology is understanding the processes responsible for phenotypic diversification related to ecological factors. New World monkeys are an excellent reference system to investigate processes of diversification at macroevolutionary scales. Here, we investigate the cranial shape diversification related to body size and ecology during the phylogenetic branching process of platyrrhines. To investigate this diversification, we used geometric morphometric techniques, a molecular phylogenetic tree, ecological data and phylogenetic comparative methods. Our statistical analyses demonstrated that the phylogenetic branching process is the most important dimension to understand cranial shape variation among extant platyrrhines and suggested that the main shape divergence among the four principal platyrrhine clades probably occurred during the initial branching process. The phylogenetic conservatism, which is the retention of ancestral traits over time within the four principal platyrrhine clades, could be the most important characteristic of platyrrhine cranial shape diversification. Different factors might have driven early shape divergence and posterior relative conservatism, including genetic drift, stabilizing selection, genetic constraints owing to pleiotropy, developmental or functional constraint, lack of genetic variation, among others. Understanding the processes driving the diversification among platyrrhines will probably require further palaeontological, phylogenetic and comparative studies.     

Environmental variability can select for optimism or pessimism

We propose operational definitions of reproductive optimism and pessimism; optimism involves behaving in a way that gives too much weight (in terms of producing surviving offspring) to positive events, pessimism gives too much weight to negative events. Natural selection maximizes the long-term growth of a lineage rather than short-term measures such as numbers of offspring. Consequently, optimism or pessimism can be favoured by natural selection, even though such biases appear irrational from a short-term perspective. We investigate the evolution of optimism in a metapopulation. The circumstances of a patch change over time, independently of other patches. With sufficient dispersal between patches, stochasticity affects members of a lineage largely independently and optimism is favoured. With little dispersal, the temporal fluctuations of a patch affect many members similarly; pessimism is then favoured. Our results establish that the spatial and temporal structure of the environment is crucial in determining the direction of evolved biases.     

The Effect of Hole Transport Material Pore Filling on Photovoltaic Performance in Solid‐State Dye‐Sensitized Solar Cells

A detailed investigation of the effect of hole transport material (HTM) pore filling on the photovoltaic performance of solid‐state dye‐sensitized solar cells (ss‐DSCs) and the specific mechanisms involved is reported. It is demonstrated that the efficiency and photovoltaic characteristics of ss‐DSCs improve with the pore filling fraction (PFF) of the HTM, 2,2’,7,7’‐tetrakis‐(N, N ‐di‐ p ‐methoxyphenylamine)9,9’‐spirobifluorene(spiro‐OMeTAD). The mechanisms through which the improvement of photovoltaic characteristics takes place were studied with transient absorption spectroscopy and transient photovoltage/photocurrent measurements. It is shown that as the spiro‐OMeTAD PFF is increased from 26% to 65%, there is a higher hole injection efficiency from dye cations to spiro‐OMeTAD because more dye molecules are covered with spiro‐OMeTAD, an order‐of‐magnitude slower recombination rate because holes can diffuse further away from the dye/HTM interface, and a 50% higher ambipolar diffusion coefficient due to an improved percolation network. Device simulations predict that if 100% PFF could be achieved for thicker devices, the efficiency of ss‐DSCs using a conventional ruthenium‐dye would increase by 25% beyond its current value.     

Low‐Temperature Behaviour of Charge Transfer Excitons in Narrow‐Bandgap Polymer‐Based Bulk Heterojunctions

Photoluminescence studies of the charge transfer exciton emission from a narrow‐bandgap polymer‐based bulk heterojunction are reported. The quantum yield of this emission is as high as 0.03%. Low temperature measurements reveal that while the dynamics of the singlet exciton is slower at low temperature, the dynamics of the charge transfer exciton emission is temperature independent. This behavior rules out any diffusion process of the charge transfer excitons and energy transfer from these interfacial states toward lower lying states. Photoluminescence measurements performed on the device under bias show a reduction (but not the total suppression) of the charge transfer exciton recombination. Finally, based on the low temperature results the role of the charge transfer excitons and the possible pathways to populate them are identified.