Biological invasions in agricultural settings: insights from evolutionary biology and population genetics

Invasion biology and agriculture are intimately related for several reasons and in particular because many agricultural pest species are recent invaders. In this article we suggest that the reconstruction of invasion routes with population genetics-based methods can address fundamental questions in ecology and practical aspects of the management of biological invasions in agricultural settings. We provide a brief description of the methods used to reconstruct invasion routes and describe their main characteristics. In particular, we focus on a scenario - the bridgehead invasion scenario -, which had been overlooked until recently. We show that this scenario, in which an invasive population is the source of other invasive populations, is evolutionarily parsimonious and may have played a crucial role in shaping the distribution of many recent agricultural pests

Insect Cecropins, Antimicrobial Peptides with Potential Therapeutic Applications

The alarming escalation of infectious diseases resistant to conventional antibiotics requires urgent global actions, including the development of new therapeutics. Antimicrobial peptides (AMPs) represent potential alternatives in the treatment of multi-drug resistant (MDR) infections. Here, we focus on Cecropins (Cecs), a group of naturally occurring AMPs in insects, and on synthetic Cec-analogs. We describe their action mechanisms and antimicrobial activity against MDR bacteria and other pathogens. We report several data suggesting that Cec and Cec-analog peptides are promising antibacterial therapeutic candidates, including their low toxicity against mammalian cells, and anti-inflammatory activity. We highlight limitations linked to the use of peptides as therapeutics and discuss methods overcoming these constraints, particularly regarding the introduction of nanotechnologies. New formulations based on natural Cecs would allow the development of drugs active against Gram-negative bacteria, and those based on Cec-analogs would give rise to therapeutics effective against both Gram-positive and Gram-negative pathogens. Cecs and Cec-analogs might be also employed to coat biomaterials for medical devices as an approach to prevent biomaterial-associated infections. The cost of large-scale production is discussed in comparison with the economic and social burden resulting from the progressive diffusion of MDR infectious diseases

Maternal predator-exposure affects offspring size at birth but not telomere length in a live-bearing fish

The perception of predation risk could affect prey phenotype both within and between generations (via parental effects). The response to predation risk could involve modifications in physiology, morphology, and behavior and can ultimately affect long-term fitness. Among the possible modifications mediated by the exposure to predation risk, telomere length could be a proxy for investigating the response to predation risk both within and between generations, as telomeres can be significantly affected by environmental stress. Maternal exposure to the perception of predation risk can affect a variety of offspring traits but the effect on offspring telomere length has never been experimentally tested. Using a live-bearing fish, the guppy (Poecilia reticulata), we tested if the perceived risk of predation could affect the telomere length of adult females directly and that of their offspring with a balanced experimental setup that allowed us to control for both maternal and paternal contribution. We exposed female guppies to the perception of predation risk during gestation using a combination of both visual and chemical cues and we then measured female telomere length after the exposure period. Maternal effects mediated by the exposure to predation risk were measured on offspring telomere length and body size at birth. Contrary to our predictions, we did not find a significant effect of predation-exposure neither on female nor on offspring telomere length, but females exposed to predation risk produced smaller offspring at birth. We discuss the possible explanations for our findings and advocate for further research on telomere dynamics in ectotherms

Island selection on mammalian life-histories: genetic differentiation in offspring size

BACKGROUND: Since Darwin's pioneering work, evolutionary changes in isolated island populations of vertebrates have continued to provide the strongest evidence for the theory of natural selection. Besides macro-evolutionary changes, micro-evolutionary changes and the relative importance of natural selection vs. genetic drift are under intense investigation. Our study focuses on the genetic differentiation in morphological and life-history traits in insular populations of a small mammal the bank vole Myodes glareolus. RESULTS: Our results do not support the earlier findings for larger adult size or lower reproductive effort in insular populations of small mammals. However, the individuals living on islands produced larger offspring than individuals living on the mainland. Genetic differentiation in offspring size was further confirmed by the analyses of quantitative genetics in lab. In insular populations, genetic differentiation in offspring size simultaneously decreases the additive genetic variation (VA) for that trait. Furthermore, our analyses of differentiation in neutral marker loci (Fst) indicate that VA is less than expected on the basis of genetic drift alone, and thus, a lower VA in insular populations could be caused by natural selection. CONCLUSION: We believe that different selection pressures (e.g. higher intraspecific competition) in an insular environment might favour larger offspring size in small mammals. Island selection for larger offspring could be the preliminary mechanism in a process which could eventually lead to a smaller litter size and lower reproductive effort frequently found in insular vertebrates.peerReviewe

Microallopatric speciation in the relict dung beetle genus Grebennikovius (Coleoptera: Scarabaeidae) in the Eastern Arc Mountains

The Eastern Arc Mountains (EAMs) in Tanzania and Kenya are renowned for their exceptional species endemism often restricted to isolated mountain blocks. Forest fragmentation during the Pliocene–Pleistocene played a sig- nificant role in shaping the EAMs’ biodiversity by facilitating allopatric speciation between different mountains. However, only a few studies focused on species diversification within the same mountain block. In this article, we investigated the taxonomy and evolution of the dung beetle genus Grebennikovius, endemic to the Uluguru Mountains. Our goal was to unravel factors promoting allopatric speciation within a confined geographic area like the Ulugurus. We used an integrative taxonomic approach, combining phenotypic data and COI barcodes to delimit species and reconstructed a timetree of the genus. Molecular and morphological evidence consistently recovered 4 distinct Grebennikovius species, of which 3 are new to science: G. armiger n. sp., G. basilewskyi (Balthasar, 1960), G. lupanganus n. sp., and G. pafelo n. sp. Grebennikovius represents a rare case of microal- lopatry, with all species occurring in close proximity within different regions of the limited Uluguru forest (∼230 km2). We infer that speciation was driven by the interplay between climate fluctuations during the Miocene and mid-Pleistocene, Uluguru topography, and the stability of rainforest ecological conditions. The latter fac- tor probably favored the loss of wings and a specialization for Uluguru microhabitats, reinforcing population isolation and divergence. This study highlights a unique instance of diversification resulting from small-scale speciation events, providing valuable insights into the evolution of Eastern African rainforest arthropods and underscoring the importance of microhabitats conservation

Molecular Phylogeny of OVOL Genes Illustrates a Conserved C2H2 Zinc Finger Domain Coupled by Hypervariable Unstructured Regions

OVO-like proteins (OVOL) are members of the zinc finger protein family and serve as transcription factors to regulate gene expression in various differentiation processes. Recent studies have shown that OVOL genes are involved in epithelial development and differentiation in a wide variety of organisms; yet there is a lack of comprehensive studies that describe OVOL proteins from an evolutionary perspective. Using comparative genomic analysis, we traced three different OVOL genes (OVOL1-3) in vertebrates. One gene, OVOL3, was duplicated during a whole-genome-duplication event in fish, but only the copy (OVOL3b) was retained. From early-branching metazoa to humans, we found that a core domain, comprising a tetrad of C2H2 zinc fingers, is conserved. By domain comparison of the OVOL proteins, we found that they evolved in different metazoan lineages by attaching intrinsically-disordered (ID) segments of N/C-terminal extensions of 100 to 1000 amino acids to this conserved core. These ID regions originated independently across different animal lineages giving rise to different types of OVOL genes over the course of metazoan evolution. We illustrated the molecular evolution of metazoan OVOL genes over a period of 700 million years (MY). This study both extends our current understanding of the structure/function relationship of metazoan OVOL genes, and assembles a good platform for further characterization of OVOL genes from diverged organisms

Genes, gene flow and adaptation of Diabrotica virgifera virgifera

Diabrotica virgifera virgifera has emerged as a major pest of cultivated maize, due to a combination of its high capacity to inflict economic damage, adaptability to pest management techniques and invasiveness. This review presents a survey of the current state of knowledge about the genetics of D. v. virgifera. In addition, the tools and resources currently available to Diabrotica geneticists are identified, as are areas where knowledge is lacking and research should be prioritized. A substantial amount of information has been published concerning the molecular phylogenetic relationships of D. v. virgifera to other chrysomelids. There is a growing literature focused on the population genetics and evolution of the species. Several adaptations to anthropogenic selection pressure have been studied, with resistance to synthetic insecticides providing some particularly well-characterized examples. A notable deficiency is a lack of studies directed toward the formal genetics of D. v. virgifera

The parasitoid species complex associated with sexual and parthenogenetic Naryciinae (Lepidoptera: Psychidae): Integrating ecological and molecular analyses

This study describes the parasitoid species complex associated with seven closely related species of sexual (Siederia rupi- collella, S. listerella, Dahlica lazuri, D. charlottae and D. lichenella) and parthenogenetic (Dahlica fennicella and D. triquetrella) Naryciinae (Lepidoptera: Psychidae) in Central Finland. A thorough ecological analysis of all the species of parasitoids recorded was combined with analyses of molecular data. Mitochondrial and nuclear DNA data were obtained from all the species in order to (1) detect cryptic species associated with host specialization, (2) assign undescribed males to females, and (3) verify the morphological identification of closely related species. A DNA barcoding technique was employed to identify host species from parasitized larval remains. By sampling more than 10,000 host larvae, of which 25.7% were parasitized, nine parasitoid species were identified mor- phologically, including both koinobionts (Ichneumonidae: Diadegma incompletum, Macrus parvulus, Trachyarus borealis, T. solya- nikovi, T. fuscipes, T. brevipennis and Braconidae: Meteorus affinis) and idiobionts (Ichneumonidae: Orthizema flavicorne, Gelis fuscicornis). Ecological characteristics such as time and mode of host attack, time of emergence and level of specialization differed widely. The results show that differences in parasitoid biology need to be taken into account when studying differences in percentage parasitism of sexual and parthenogenetic Naryciinae. The molecular data revealed that one parasitoid species M. parvulus may con- sist of two cryptic forms associated with the sexual and parthenogenetic hosts, respectively. The data further establishes that T. bre- vipennis and some T. fuscipes are in fact morphotypes of one species. The large variation in mitochondrial DNA within species and its inconsistency with nuclear DNA demonstrate that current species and genus delimitation is inadequate in the Trachyarus species group. Our study shows that it is essential to use DNA barcoding methods when investigating host-parasitoid complexes

Negative density-distribution relationship in butterflies

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