Showing papers by "Etienne Danchin published in 2018"
TL;DR: It is found that fruitflies have five cognitive capacities that enable them to transmit mating preferences culturally across generations, potentially fostering persistent traditions (the main marker of culture) in mating preference.
Abstract: Despite theoretical justification for the evolution of animal culture, empirical evidence for it beyond mammals and birds remains scant, and we still know little about the process of cultural inheritance. In this study, we propose a mechanism-driven definition of animal culture and test it in the fruitfly. We found that fruitflies have five cognitive capacities that enable them to transmit mating preferences culturally across generations, potentially fostering persistent traditions (the main marker of culture) in mating preference. A transmission chain experiment validates a model of the emergence of local traditions, indicating that such social transmission may lead initially neutral traits to become adaptive, hence strongly selecting for copying and conformity. Although this situation was suggested decades ago, it previously had little empirical support.
122 citations
TL;DR: This work integrated biological mechanisms that interfere with the response to selection, and explored their potential combined effect for explaining the apparent evolutionary stasis of wild populations and the conservation of wildlife.
Abstract: Although there are many examples of contemporary directional selection, evidence for responses to selection that match predictions are often missing in quantitative genetic studies of wild populations. This is despite the presence of genetic variation and selection pressures – theoretical prerequisites for the response to selection. This conundrum can be explained by statistical issues with accurate parameter estimation, and by biological mechanisms that interfere with the response to selection. These biological mechanisms can accelerate or constrain this response. These mechanisms are generally studied independently but might act simultaneously. We therefore integrated these mechanisms to explore their potential combined effect. This has implications for explaining the apparent evolutionary stasis of wild populations and the conservation of wildlife.
95 citations
TL;DR: The pea aphid transgenerational phenotypic response to ladybird predators during 27 generations of experimental evolution in the absence of initial genetic variation was monitored to highlight the importance of integrating several components of non-genetic inheritance to detect evolutionary responses to environmental changes.
Abstract: Transgenerational phenotypic plasticity is a fast non-genetic response to environmental modifications that can buffer the effects of environmental stresses on populations. However, little is known about the evolution of plasticity in the absence of standing genetic variation although several non-genetic inheritance mechanisms have now been identified. Here we monitored the pea aphid transgenerational phenotypic response to ladybird predators (production of winged offspring) during 27 generations of experimental evolution in the absence of initial genetic variation (clonal multiplication starting from a single individual). We found that the frequency of winged aphids first increased rapidly in response to predators and then remained stable over 25 generations, implying a stable phenotypic reconstruction at each generation. We also found that the high frequency of winged aphids persisted for one generation after removing predators. Winged aphid frequency then entered a refractory phase during which it dropped below the level of control lines for at least two generations before returning to it. Interestingly, the persistence of the winged phenotype decreased and the refractory phase lasted longer with the increasing number of generations of exposure to predators. Finally, we found that aphids continuously exposed to predators for 22 generations evolved a significantly weaker plastic response than aphids never exposed to predators, which, in turn, increased their fitness in presence of predators. Our findings therefore showcased an example of experimental evolution of plasticity in the absence of initial genetic variation and highlight the importance of integrating several components of non-genetic inheritance to detect evolutionary responses to environmental changes.
34 citations
TL;DR: The results suggest that finding sexual mates may have been involved in overwintering aggregations in H. undecimnotata, an aphidophagous species from Southern and Eastern Europe as well as Asia.
Abstract: Aggregation during diapause is a common phenomenon in arthropods that nevertheless remains poorly understood. The most commonly claimed benefit is that survival is higher in aggregations but animal aggregations could also be driven by sexual selection. In this perspective, we investigated whether aggregations in insects could be part of their mating system. We studied the overwintering aggregations of the ladybird Hippodamia undecimnotata (Schneider), an aphidophagous species from Southern and Eastern Europe as well as Asia. We collected ladybirds at three aggregation sites in Southwest France, during two overwintering periods (2013-2014 and 2014-2015). We checked their reproductive status by counting the viable sperm cells in the sperm storage organs of both males and females, and by assessing the ovarian status of females. We also investigated if mating behaviour occurred in these aggregations. We found that males have a high quantity of viable sperm cells (70-95%) in their reproductive organs throughout the overwintering periods. In contrast, although most females (85-95%) had empty spermatheca at the onset of the aggregations in autumn, the majority (65-91%) had numerous viable sperm in their spermatheca at the time of dispersal from the aggregation in early spring. Furthermore, frequent copulations were observed towards the end of the overwintering period, few weeks before dispersal. These results suggest that finding sexual mates may have been involved in overwintering aggregations in H. undecimnotata.
28 citations
TL;DR: The identification of functional novel R genes in wild Arachis species responsible for triggering effective defense cascades can contribute to the crop genetic improvement and enhance peanut resilience to RKN.
Abstract: The Root-Knot Nematode (RKN), Meloidogyne arenaria, significantly reduces peanut grain quality and yield worldwide. Whilst the cultivated species has low levels of resistance to RKN and other pests and diseases, peanut wild relatives (Arachis spp.) show rich genetic diversity and harbor high levels of resistance to many pathogens and environmental constraints. Comparative transcriptome analysis can be applied to identify candidate resistance genes. Transcriptome analysis during the early stages of RKN infection of two peanut wild relatives, the highly RKN resistant Arachis stenosperma and the moderately susceptible A. duranensis, revealed genes related to plant immunity with contrasting expression profiles. These included genes involved in hormone signaling and secondary metabolites production and also members of the NBS-LRR class of plant disease resistance (R) genes. From 345 NBS-LRRs identified in A.duranensis reference genome, 52 were differentially expressed between inoculated and control samples, with the majority occurring in physical clusters unevenly distributed on eight chromosomes with preferential tandem duplication. The majority of these NBS-LRR genes showed contrasting expression behaviour between A. duranensis and A. stenosperma, particularly at 6 days after nematode inoculation, coinciding with the onset of the Hypersensitive Response in the resistant species. The physical clustering of some of these NBS-LRR genes correlated with their expression patterns in the contrasting genotypes. Four NBS-LRR genes exclusively expressed in A. stenosperma are located within clusters on chromosome Aradu. A09, which harbors a QTL for RKN resistance, suggesting a functional role for their physical arrangement and their potential involvement in this defense response. The identification of functional novel R genes in wild Arachis species responsible for triggering effective defense cascades can contribute to the crop genetic improvement and enhance peanut resilience to RKN.
23 citations
TL;DR: Drosophila females seem to have evolved a mate-copying ability independently of sex ratio, and a capacity to adapt their choosiness to male availability, which suggests that, as in many animal species, individuals, especially females, can adapt their mate choice depending on the current sex ratio.
Abstract: In many sexually reproducing species, individuals can gather information about potential mates by observing their mating success. This behavioral pattern, that we call mate-copying, was reported in the fruit fly Drosophila melanogaster where females choosing between 2 males of contrasting phenotypes can build a preference for males of the phenotype they previously saw being chosen by a demonstrator female. As sex ratio is known to affect mate choice, our goal was to test whether mate-copying is also affected by encountered sex ratios. Thus, we created a gradient of sex ratio during demonstrations of mate-copying experiments by changing the number of females observing from a central arena 6 simultaneous demonstrations unfolding in 6 peripheral compartments of a hexagonal device. We also tested whether the sex ratio experienced by females during demonstrations affected their choosiness (male courtship duration and double courtship rate) in subsequent mate-choice tests. Experimental male:female sex ratio during demonstrations did not affect mate-copying indices, but positively affected the proportion of both males courting the female during mate-choice tests, as well as male courtship duration, the latter potentially explaining the former relationship. As expected, the sex ratio affected female choosiness positively, and Drosophila females seem to have evolved a mate-copying ability independently of sex ratio, and a capacity to adapt their choosiness to male availability. This suggests that, as in many animal species, individuals, especially females, can adapt their mate choice depending on the current sex ratio.
21 citations
TL;DR: It is shown that females of either the Curly-wing (Cy) or the wild-type (WT) phenotype, after observing another female preferring to copulate with a fitness-lowering Cy male over a WT male, increased their preference for the usually nonpreferred Cy phenotype, indicating that mate-copying also exists for costly variants in invertebrates.
Abstract: Mate-copying is a form of social learning in which witnessing sexual interactions between conspecifics biases an observer female's future mate-choice We show in the fruit fly that females of either the Curly-wing (Cy) or the wild-type (WT) phenotype, after observing another female preferring to copulate with a fitness-lowering Cy male over a WT male, increased their preference for the usually nonpreferred Cy phenotype Thus, mate-copying also exists for costly variants in invertebrates
15 citations
TL;DR: Experimental evidence for mate copying in males of Drosophila melanogaster in which females can actively reject males and prevent copulation is reported, suggesting that male fruit flies can also perform mate copying.
14 citations
TL;DR: This work compared the genomes and transcriptomes of parthenogenetic and sexual Panagrolaimus species to identify systems that contribute to these striking abilities.
Abstract: Most animal species reproduce sexually, but parthenogenesis, asexual reproduction of various forms, has arisen repeatedly. Parthenogenetic lineages are usually short lived, though in some environments parthenogenesis may be advantageous. Panagrolaimus nematodes have colonised environments ranging from arid deserts to arctic and antarctic biomes. Many are parthenogens, and most have cryptobiotic (anhydrobiotic and/or cryobiotic) abilities. We compared the genomes and transcriptomes of parthenogenetic and sexual Panagrolaimus species to identify systems that contribute to these striking abilities. The parthenogens are triploids of hybrid origin. All Panagrolaimus have acquired genes through horizontal gene transfer, some of which are likely to contribute to cryptobiosis.
14 citations
TL;DR: Providing an atlas of epigenetic factors relevant to the plant-parasitic lifestyle and/or asexual mode of reproduction of RKN is an informative resource that will enable researchers to explore their potential role in adaptation of these parasites to their environment.
Abstract: The renewed interest in epigenetics has led to the understanding that both the environment and individual lifestyle can directly interact with the epigenome to influence its dynamics. Epigenetic phenomena are mediated by DNA methylation, stable chromatin modifications and non-coding RNA-associated gene silencing involving specific proteins called epigenetic factors. Multiple organisms, ranging from plants to yeast and mammals, have been used as model systems to study epigenetics. The interactions between parasites and their hosts are models of choice to study these mechanisms because the selective pressures are strong and the evolution is fast. The asexually reproducing root-knot nematodes (RKN) offer different advantages to study the processes and mechanisms involved in epigenetic regulation. RKN genomes sequencing and annotation have identified numerous genes, however, which of those are involved in the adaption to an environment and potentially relevant to the evolution of plant-parasitism is yet to be discovered. Here, we used a functional comparative annotation strategy combining orthology data, mining of curated genomics as well as protein domain databases and phylogenetic reconstructions. Overall, we show that (i) neither RKN, nor the model nematode Caenorhabditis elegans possess any DNA methyltransferases (DNMT) (ii) RKN do not possess the complete machinery for DNA methylation on the 6th position of adenine (6mA) (iii) histone (de)acetylation and (de)methylation pathways are conserved between C. elegans and RKN, and the corresponding genes are amplified in asexually reproducing RKN (iv) some specific non-coding RNA families found in plant-parasitic nematodes are dissimilar from those in C. elegans. In the asexually reproducing RKN Meloidogyne incognita, expression data from various developmental stages supported the putative role of these proteins in epigenetic regulations. Our results refine previous predictions on the epigenetic machinery of model species and constitute the most comprehensive description of epigenetic factors relevant to the plant-parasitic lifestyle and/or asexual mode of reproduction of RKN. Providing an atlas of epigenetic factors in RKN is an informative resource that will enable researchers to explore their potential role in adaptation of these parasites to their environment.
11 citations
TL;DR: Results suggest that multiple gains and losses of parasitic abilities and adaptations to different environmental conditions account for the broad host spectrum and wide geographic distribution of M. incognita.
Abstract: The most devastating nematodes to worldwide agriculture are the root-knot nematodes with Meloidogyne incognita being the most widely distributed and damaging species. This parasitic and ecological success seem surprising given its supposed obligatory clonal reproduction. Clonal reproduction has been suspected based on cytological observations but, so far, never confirmed by population genomics data. At the species level, M. incognita is highly polyphagous with thousands of host plants. However, the host range varies among different M. incognita isolates that may present distinct and more restricted host compatibilities. Historically, four ‘host races’ had been defined as a function of ranges of compatible and incompatible plants. We sequenced the genomes of 11 isolates across Brazil, covering these four distinct races to assess (i) how clonal reproduction is and (ii) how the level of genome variability associates with biological traits such as the host races, affected agronomic culture, and geographical distribution. By aligning the genomic reads of the isolates to the M. incognita reference genome assembly, we identified SNV and small-scale insertions/deletions. Analysis of linkage disequilibrium and 4-gametes test, showed no sign of recombination, confirming the clonal mode of reproduction of M. incognita. We showed that there are relatively few point variations between the different isolates, and these variations show no significant association with either the host races, the geographical origin of the samples or the host plant on which they have been collected. Due to the lack of phylogenetic signal underlying their existence, we recommend the discontinuation of the terminology “race”. Overall, these results suggest that multiple gains and losses of parasitic abilities and adaptations to different environmental conditions account for the broad host spectrum and wide geographic distribution of M. incognita. Hence, this nematode constitutes a model species to study adaptability without sexual recombination and overall low genomic variations in animals.
TL;DR: It is shown that there are relatively low point variations between the different isolates, despite their various different ecological characteristics, which suggest that multiple independent adaptations to different hosts and environmental conditions have occurred and illustrate the high adaptive potential of this agricultural pest.
Abstract: The most devastating nematodes to worldwide agriculture are the root-knot nematodes with Meloidogyne incognita being considered as the most ubiquitous. At the species level, M. incognita is polyphagous with thousands of host plants. However, this wide host range seems to be due to an assemblage of different isolates that each have distinct and more restricted host compatibilities. In this species, four host races have been defined as a function of distinct ranges of compatible and incompatible plants. To assess whether there is an evolutionary signal underlying these host races, we sequenced the genomes of 11 isolates across these four different races. By aligning the genomes of the isolates to the M. incognita reference genome, we identified SNPs and small-scale insertions/deletions. We showed that there are relatively low point variations between the different isolates, despite their various different ecological characteristics. Furthermore, these variations neither correlate with the four host races, the geographical origin of the samples nor the host plant on which they have been collected. These results suggest that multiple independent adaptations to different hosts and environmental conditions have occurred and illustrate the high adaptive potential of this agricultural pest despite its clonal mode of reproduction. Although the recognition of variation in M. incognita host range exists, we recommend the discontinuation of the terminology 9race9 considering there is no genetic signal underlying and supporting the concept of races in M. incognita.
TL;DR: The phylogenetic and gene structure analyses indicate that at least one gene encoding a putative cellulolytic GH45 was present in the last common ancestor of the Phytophaga, and that GH45 xyloglucanases evolved several times independently in these beetles.
Abstract: Cellulose, a major polysaccharide of the plant cell wall, consists of β-1,4-linked glucose moieties forming a molecular network recalcitrant to enzymatic breakdown. Although cellulose is potentially a rich source of energy, the ability to degrade it is rare in animals and was believed to be present only in cellulolytic microbes. Recently, it has become clear that some animals encode endogenous cellulases belonging to several glycoside hydrolase families (GHs), including GH45. GH45s are distributed patchily among the Metazoa and, in insects, are encoded only by the genomes of Phytophaga beetles. This study aims to understand both the enzymatic properties and the evolutionary history of GH45s in these beetles. To this end, we tested the enzymatic abilities of 37 GH45s derived from five species of Phytophaga beetles and learned that beetle-derived GH45s degrade three different substrates: amorphous cellulose, xyloglucan and glucomannan. Our phylogenetic and gene structure analyses indicate that at least one gene encoding a putative cellulolytic GH45 was present in the last common ancestor of the Phytophaga, and that GH45 xyloglucanases evolved several times independently in these beetles. The most closely related clade to Phytophaga GH45s contained fungal sequences, suggesting this GH family was acquired by horizontal gene transfer from fungi. Other than in insects, arthropod GH45s do not share a common origin and appear to have emerged at least three times independently.
05 Dec 2018