Like ecological communities, which vary in species composition, eukaryote genomes differ in the amount and diversity of transposable elements (TEs) that they harbor. Because TEs have a considerable impact on the biology of their host species, we need to better understand whether their dynamics reflects some form of organization or is primarily driven by stochastic processes. Here we borrow ecological concepts on species diversity to explore how interactions between TEs can contribute to structure TE communities within their genomic ecosystem. Whereas the niche theory predicts a stable diversity of TEs because of their divergent characteristics, the neutral theory of biodiversity predicts the assembly of TE communities from stochastic processes acting at the level of individual TE. Contrary to ecological communities, however, TE communities are shaped by selection at the level of their ecosystem, i.e., the host individual. Developing ecological models specific to the genome will thus be pre-requisite for modeling the dynamics of TEs. Towards an ecology of the genomeTransposable elements (TEs) constitute a large proportion of many multicellular eukaryote genomes, from 4% in the yeast Saccharomyces cerevisiae to more than 70 % in some plants and amphibians, and 45% in human [1]. The mobility and amplification of TEs represent a major source of genomic variation either by virtue of their insertion or by triggering a variety of small-and large-scale chromosomal rearrangements. Once inserted, most TE copies serve no immediate function and thus their sequences progressively decay by accumulating mutations at the neutral rate of the species and eventually disappear. Occasionally, some TE copies may be co-opted by the genome to function either as coding sequences or as regulatory elements [2]. Whereas TEs can be said to contribute genetic variation and therefore innovation [1][2][3][4][5][6], their uncontrolled movement and proliferation pose a threat to genome integrity. Indeed, TEs are an important cause of deleterious mutations and illnesses, including in humans [7][8], and therefore several host-encoded mechanisms exist to silence or restrict their activity [9][10][11][12].TEs are classified into different classes and subclasses on the basis of their structural organization and of mechanisms of transposition (DNA transposons, Long Terminal Repeat (LTR) retrotransposons, non-LTR retrotransposons…) [1], and further divided into families and sub-families (see Box 1). Genomes of different organisms contain widely differing numbers of TE families and of TE copy numbers per family (Box 1). The main challenge we are facing is therefore to understand to what extent the contrasted patterns and variations that Corresponding author: Venner, we see across genomes in the amount and diversity of TEs reflect some sort of organization, or whether they are largely idiosyncratic, i.e., the result of stochastic processes. The dynamics of TEs has been modeled on the basis of their transposition and excision rates and their fitne...

International audienceInsects comprise relevant biological models for investigating nutrient acquisition and allocation processes in the context of life-history ecology and evolution. However, empirical investigations are still partly limited by the lack of availability of simple methods for simultaneously estimating the four major energetic components (i.e. lipids, free sugars, glycogen and proteins) in the same individual. In the present work, we validate a fast, reproducible and cheap method for overcoming this problem that uses different solvents successively. First, proteins are solubilized in a phosphate-lysis buffer and then quantified according to the classical Bradford assay procedure. In a second step, a chloroform-methanol mixture is added to the aqueous phase, which allows assay of the total lipid fraction, as well as the free sugars and glycogen in the same insect homogenate. In addition, a micro-separation procedure is adapted to partition the total lipids into neutral (mainly stored lipids) and polar (mainly structural lipids) components. Although these assays are conducted sequentially in the same individual, the sensitivity of our method remains high: the estimated amount of each energetic compartment does not differ from that obtained with former, partial methods. Our method should thus largely improve our knowledge about nutrient acquisition and allocation among insects not only in laboratory-reared individuals, but also in animals caught in the wild. Descriptions and recommendations are given at each step of the protocol to adapt the procedure to various insect species. Finally, to prevent misinterpretation of data generated in accordance with this protocol, the limits of our method are discussed in the light of life-history studies