Plastic and heritable variation in shell thickness of the intertidal gastropod Nucella lapillus associated with risks of crab predation and wave action, and sexual maturation

The intertidal snail Nucella lapillus generally has thicker shells at sites sheltered from wave action, where crabs are abundant and pose a high risk of predation, than at exposed sites where crabs are rare. We studied two populations showing the opposite trend. We reciprocally transplanted snails between field sites and measured shell length, width and lip thickness of those recaptured 12 months later. Snails transplanted to the sheltered site grew larger than sheltered-site residents, which in turn grew larger than transplants to the exposed site. Relative shell-lip thickness was greater in residents at the exposed site than at the sheltered site. Transplants from shelter to exposure developed relatively thicker shells than their controls and relatively thinner shells from exposure to shelter. Progeny of the two populations were reared for 12 months in a common garden experiment presenting effluent from crabs feeding on broken conspecifics as the treatment and fresh sea-water as the control. The crab-effluent treatment decreased foraging activity, concomitantly reducing cumulative somatic growth and reproductive output. Juveniles receiving crab-effluent grew slower in shell length while developing relatively thicker shell lips than controls, the level of response being similar between lineages. F(2) progeny of the exposed-site lineage showed similar trends to the F(1)s; sheltered-site F(2)s were too few for statistical analysis. At sexual maturity, shell-lip thickness was greater in snails receiving crab-effluent than in controls, indicating plasticity, but was also greater in the exposed-site than in the sheltered-site lineage, indicating heritable variation, probably in degree of sexual thickening of the shell lip. Results corroborate hypotheses that 'defensive' shell thickening is a passive consequence of starvation and that heritable and plastic control of defensive shell morphology act synergistically. Shell thickening of juveniles was similar between lineages, contrary to hypotheses predicting differential strengths of plasticity in populations from low- or high-risk habitats.publishe

Parental care results in a greater mutation load, for which it is also a phenotypic antidote

Benevolent social behaviours, such as parental care, are thought to enable mildly deleterious mutations to persist. We tested this prediction experimentally using the burying beetle Nicrophorus vespilloides, an insect with biparental care. For 20 generations, we allowed replicate experimental burying beetle populations to evolve either with post-hatching care ('Full Care' populations) or without it ('No Care' populations). We then established new lineages, seeded from these experimental populations, which we inbred to assess their mutation load. Outbred lineages served as controls. We also tested whether the deleterious effects of a greater mutation load could be concealed by parental care by allowing half the lineages to receive post-hatching care, while half did not. We found that inbred lineages from the Full Care populations went extinct more quickly than inbred lineages from the No Care populations-but only when offspring received no post-hatching care. We infer that Full Care lineages carried a greater mutation load, but that the associated deleterious effects on fitness could be overcome if larvae received parental care. We suggest that the increased mutation load caused by parental care increases a population's dependence upon care. This could explain why care is seldom lost once it has evolved

The evolutionary demise of a social interaction: experimentally induced loss of traits involved in the supply and demand of care

Phenotypic plasticity enables animals to adjust their behavior flexibly to their social environment—sometimes through the expression of adaptive traits that have not been exhibited for several generations. We investigated how long social adaptations can usefully persist when they are not routinely expressed, by using experimental evolution to document the loss of social traits associated with the supply and demand of parental care. We allowed populations of burying beetles Nicrophorus vespilloides to evolve in two different social environments for 48 generations in the lab. In “Full Care” populations, traits associated with the supply and demand of parental care were expressed at every generation, whereas in “No Care” populations we prevented expression of these traits experimentally. We then revived trait expression in the No Care populations at generations 24, 43, and 48 by allowing parents to supply post-hatching care and compared these social traits with those expressed by the Full Care populations. We found that offspring demands for care and male provision of care in the No Care populations were lost sooner than female provision of care. We suggest that this reflects differences in the strength of selection for the expression of alternative traits in offspring, males and females, which can enhance fitness when post-hatching care is disrupted

Optimizing the profit from a complex cascade of hydroelectric stations with recirculating water

In modern reversible hydroelectric power stations it is possible to reverse the turbine and pump water up from a downstream reservoir to an upstream one. This allows the use of the same volume of water repeatedly and was speci cally developed for hydro-electric stations operating with in- su cient water supply. Pumping water upstream is usually done at times of low demand for electricity, to build up reserves in order to be able to produce energy during peak hours, thus balancing the load and making a pro t on the price di erence. In this paper, we consider a branched model for hydroelectric power stations interacting in a complex cascade arrangement. The goal of this study is to provide guidance in decision-making aimed at maximizing the pro t. A detailed analysis is made of a simpler reservoir con guration, which indicates that even though the problem is nonlinear, a bang-bang type of control is optimal, where the power stations are operated at maximum rates of flow. Some simple relationships between price and timing of decisions are calculated directly. A numerical algorithm is also developed.This problem was brought by Redes Energéticas Nacionais to the 69th European Study Group with Industry, April 20–24, 2009, Departamento de Matemática da Universidade de Coimbra, Portugal. Andrei Korobeinikov and Mark McGuinness are very grateful to the organizers of the 69th ESGI for financial support and for their kind and generous hospitality. Andrei Korobeinikov and Mark McGuinness are supported by the Mathematics Applications132 Optimizing the profit from a complex cascade of hydroelectric stations with recirculating water Consortium for Science and Industry, funded by the Science Foundation Ireland Mathematics Initiative Grant 06/MI/005. Mark McGuinness also thanks OCCAM in Oxford for supporting his travels. Marta Pascoal is partially funded by the Portuguese FCT under project POSC/U308/1.3/NRE/04

Release from intralocus sexual conflict? Evolved loss of a male sexual trait demasculinizes female gene expression

Funding: Bioinformatic analyses were supported by the University of St Andrew Bioinformatics Unit (Wellcome Trust ISSF award 105621/Z/14/Z). This work was supported by funding to N.W.B. from the UK Natural Environment Research Council which is gratefully acknowledged (NE/I027800/1, NE/G014906/1, NE/L011255/1).The loss of sexual ornaments is observed across taxa, and pleiotropic effects of such losses provide an opportunity to gain insight into underlying dynamics of sex-biased gene expression and intralocus sexual conflict (IASC). We investigated this in a Hawaiian field cricket, Teleogryllus oceanicus, in which an X-linked genotype (flatwing) feminises males’ wings and eliminates their ability to produce sexually selected songs. We profiled adult gene expression across somatic and reproductive tissues of both sexes. Despite the feminising effect of flatwing on male wings, we found no evidence of feminised gene expression in males. Instead, female transcriptomes were more strongly affected by flatwing than males’, and exhibited demasculinised gene expression. These findings are consistent with a relaxation of IASC constraining female gene expression through loss of a male sexual ornament. In a follow-up experiment we found reduced testes mass in flatwing males, whereas female carriers showed no reduction in egg production. In contrast, female carriers exhibited greater measures of body condition. Our results suggest sex-limited phenotypic expression offers only partial resolution to intralocus sexual conflict, owing to pleiotropic effects of the loci involved. Benefits conferred by release from intralocus conflict could help explain widespread loss of sexual ornaments across taxa.PostprintPeer reviewe

Testing the role of trait reversal in evolutionary diversification using song loss in wild crickets

The mechanisms underlying rapid macro evolution are controversial.One largely untested hypothesis that could inform this debate is that evolutionary reversals might release variation in vestigial traits, which then facilitate subsequent diversification. We evaluated this idea by testing key predictions about vestigial traits arising from sexual trait reversal in wild field crickets. In Hawaiian Teleogryllus oceanicus, the recent genetic loss of sound producing and amplifying structures on male wings eliminates their acoustic signals.Silence protects these ‘flatwing’ males from an acoustically orienting parasitoid and appears to have evolved independently more than once.Here we report that flatwing males show enhanced variation in vestigial resonator morphology under varied genetic backgrounds. Using laser Doppler vibrometry, we found that these vestigial sound-producing wing features resonate at highly variable acoustic frequencies well outside the normal range for this species. These results satisfy two important criteria for a mechanism driving rapid evolutionary diversification: sexual signal loss was accompanied by a release of vestigial morphological variants, and these could facilitate the rapid evolution of novel signal values. Widespread secondary trait losses have been inferred from fossil and phylogenetic evidence across numerous taxa, and our results suggest that such reversals could play a role in shaping historical patterns of diversification

Sexual selection and population divergence II. Divergence in different sexual traits and signal modalities in field crickets (Teleogryllus oceanicus).

Sexual selection can target many different types of traits. However, the relative influence of different sexually selected traits during evolutionary divergence is poorly understood. We used the field cricket Teleogryllus oceanicus to quantify and compare how five traits from each of three sexual signal modalities and components diverge among allopatric populations: male advertisement song, cuticular hydrocarbon (CHC) profiles and forewing morphology. Population divergence was unexpectedly consistent: we estimated the among-population (genetic) variance-covariance matrix, D, for all 15 traits, and Dmax explained nearly two-thirds of its variation. CHC and wing traits were most tightly integrated, whereas song varied more independently. We modeled the dependence of among-population trait divergence on genetic distance estimated from neutral markers to test for signatures of selection versus neutral divergence. For all three sexual trait types, phenotypic variation among populations was largely explained by a neutral model of divergence. Our findings illustrate how phenotypic integration across different types of sexual traits might impose constraints on the evolution of mating isolation and divergence via sexual selection.Funding was provided by Natural Environment Research Council grants to N.W.B. (NE/G014906/1, NE/L011255/1, NE/I027800/1), a University of California Pacific Rim Research Grant to N.W.B. (08.T.PRRP.05.0029), an Erasmus exchange grant to support M.M., a University Royal Society Fellowship and Royal Society Equipment Grant to J.H., and a BBSRC David Phillips Fellowship to A.J.W

Rapid evolution and gene expression : a rapidly-evolving Mendelian trait that silences field crickets has widespread effects on mRNA and protein expression

A major advance in modern evolutionary biology is the ability to start linking phenotypic evolution in the wild with genomic changes that underlie that evolution. We capitalised on a rapidly-evolving Hawaiian population of crickets (Teleogryllus oceanicus) to test hypotheses about the genomic consequences of a recent Mendelian mutation of large effect which disrupts the development of sound-producing structures on male forewings. The resulting silent phenotype, flatwing, persists because of natural selection imposed by an acoustically-orienting parasitoid, but it interferes with mate attraction. We examined gene expression differences in developing wing buds of wild-type and flatwing male crickets using RNA-seq and quantitative proteomics. Most differentially expressed (DE) transcripts were down-regulated in flatwing males (625 up vs. 1716 down), whereas up and down-regulated proteins were equally represented (30 up and 34 down). Differences between morphs were clearly not restricted to a single pathway, and we recovered annotations associated with a broad array of functions that would not be predicted a priori. Using a candidate gene detection test based on homology we identified 30% of putative Drosophila wing development genes in the cricket transcriptome, but only 10% were DE. In addition to wing related annotations, endocrine pathways and several biological processes such as reproduction, immunity and locomotion were DE in the mutant crickets at both biological levels. Our results illuminate the breadth of genetic pathways that are potentially affected in the early stages of adaptation.PostprintPeer reviewe

Field cricket genome reveals the footprint of recent, abrupt adaptation in the wild.

Evolutionary adaptation is generally thought to occur through incremental mutational steps, but large mutational leaps can occur during its early stages. These are challenging to study in nature due to the difficulty of observing new genetic variants as they arise and spread, but characterizing their genomic dynamics is important for understanding factors favoring rapid adaptation. Here, we report genomic consequences of recent, adaptive song loss in a Hawaiian population of field crickets (Teleogryllus oceanicus). A discrete genetic variant, flatwing, appeared and spread approximately 15 years ago. Flatwing erases sound-producing veins on male wings. These silent flatwing males are protected from a lethal, eavesdropping parasitoid fly. We sequenced, assembled and annotated the cricket genome, produced a linkage map, and identified a flatwing quantitative trait locus covering a large region of the X chromosome. Gene expression profiling showed that flatwing is associated with extensive genome-wide effects on embryonic gene expression. We found that flatwing male crickets express feminized chemical pheromones. This male feminizing effect, on a different sexual signaling modality, is genetically associated with the flatwing genotype. Our findings suggest that the early stages of evolutionary adaptation to extreme pressures can be accompanied by greater genomic and phenotypic disruption than previously appreciated, and highlight how abrupt adaptation might involve suites of traits that arise through pleiotropy or genomic hitchhiking