Age‐related telomere shortening is considered a hallmark of the ageing process. However, a recent cross‐sectional ageing study of relative telomere length (rTL) in bats failed to detect a relationship between rTL and age in the long‐lived genus Myotis (M. myotis and M. bechsteinii), suggesting some other factors are responsible for driving telomere dynamics in these species. Here, we test if longitudinal rTL data show signatures of age‐associated telomere attrition in M. myotis and differentiate which intrinsic or extrinsic factors are likely to drive telomere length dynamics. Using quantitative polymerase chain reaction, rTL was measured in 504 samples from a marked population, from Brittany, France, captured between 2013 and 2016. These represent 174 individuals with an age range of 0 to 7+ years. We find no significant relationship between rTL and age (p = .762), but demonstrate that within‐individual rTL is highly variable from year to year. To investigate the heritability of rTL, a population pedigree (n = 1744) was constructed from genotype data generated from a 16‐microsatellite multiplex, designed from an initial, low‐coverage, Illumina genome for M. myotis. Heritability was estimated in a Bayesian, mixed model framework, and showed that little of the observed variance in rTL is heritable (h2 = 0.01–0.06). Rather, correlations of first differences, correlating yearly changes in telomere length and weather variables, demonstrate that, during the spring transition, average temperature, minimum temperature, rainfall and windspeed correlate with changes in longitudinal telomere dynamics. As such, rTL may represent a useful biomarker to quantify the physiological impact of various environmental stressors in bats.

During meiosis, crossover rates are not randomly distributed along the chromosome and their location may have a strong impact on the functioning and evolution of the genome. To date, the broad diversity of recombination landscapes among plants has rarely been investigated and a formal comparative genomic approach is still needed to characterize and assess the determinants of recombination landscapes among species and chromosomes. We gathered genetic maps and genomes for 57 flowering plant species, corresponding to 665 chromosomes, for which we estimated large-scale recombination landscapes. We found that the number of crossover per chromosome spans a limited range (between one to five/six) whatever the genome size, and that there is no single relationship across species between genetic map length and chromosome size. Instead, we found a general relationship between the relative size of chromosomes and recombination rate, while the absolute length constrains the basal recombination rate for each species. At the chromosome level, we identified two main patterns (with a few exceptions) and we proposed a conceptual model explaining the broad-scale distribution of crossovers where both telomeres and centromeres play a role. These patterns correspond globally to the underlying gene distribution, which affects how efficiently genes are shuffled at meiosis. These results raised new questions not only on the evolution of recombination rates but also on their distribution along chromosomes.

22Bacteria from the genus Flavobacteriaceae often show low susceptibility to antibiotics. With the 23 exception of two Chryseobacterium spp. isolates that were positive for the florfenicol resistance 24 gene floR, no clinical resistance genes were identified by microarray in 36 Flavobacteriaceae isolates 25 from salmonid fish that could grow in ≥ 4 mg/L florfenicol. Whole genome sequence analysis of the 26 floR positive isolates revealed the presence of a region that contained the antimicrobial resistance 27 (AMR) genes floR, a tet(X) tetracycline resistance gene, a streptothricin resistance gene and a 28 chloramphenicol acetyltransferase gene. In silico analysis of 377 published genomes for 29Flavobacteriaceae isolates from a range of sources, confirmed that well-characterized resistance 30 gene cassettes were not widely distributed in bacteria from this group. Efflux pump-mediated 31 decreased susceptibility to a range of antimicrobials was confirmed in both floR positive isolates 32 using an efflux pump inhibitor (phenylalanine-arginine β-naphthylamide) assay. The floR isolates 33 possessed putative virulence factors, including production of siderophores and, haemolysins, and 34 were mildly pathogenic in rainbow trout. Results support the suggestion that, despite the detection 35 of floR, susceptibility to antimicrobials in Flavobacteriaceae is mostly mediated via intrinsic 36 mechanisms rather than the horizontally acquired resistance genes more normally associated with 37Gram-negative bacterial pathogens such as Enterobacteriaceae. 38 39

Brazier Thomas and Cherif Emira should be considered joint first authors.

During meiosis, crossover rates are not randomly distributed along the chromosome and therefore they locally influence the creation of novel genotypes and the efficacy of selection. To date, the broad diversity of recombination landscapes among plants has rarely been investigated, undermining the overall understanding of the constraints driving the evolution of crossover frequency and distribution. The determinants that shape the local crossover rate and the diversity of the resulting landscapes among species and chromosomes still need to be assessed in a formal comparative genomic approach. We gathered genetic maps and genomes for 57 flowering plant species, corresponding to 665 chromosomes, for which we estimated large-scale recombination landscapes. Chromosome length drives the basal recombination rate for each species, but within species we were intrigued to notice that the chromosome-wide recombination rate is proportional to the relative size of the chromosome. Moreover, for larger chromosomes, crossovers tend to accumulate at the ends of the chromosome leaving the central regions as recombination-free regions. Based on identified crossover patterns and testable predictions, we proposed a conceptual model explaining the broad-scale distribution of crossovers where both telomeres and centromeres are important. Finally, we qualitatively identified two recurrent crossover patterns among species and highlighted that these patterns globally correspond to the underlying gene distribution. In addition to the positive correlation between recombination and gene density, we argue that crossover patterns are essential for the efficiency of chromosomal genetic shuffling, even though the ultimate evolutionary potential forged by the diversity of recombination landscapes remains an open question.

Invasive species are significant contributors to global changes and constitute a severe threat to biodiversity. Yet invasions offer an incredible framework to understand how small and low-diverse introduced populations adapt to novel environmental conditions and succeed in colonizing large areas. However, due to the insufficient data on the origin of the first introduced propagule and the first stage of invasion, reconstructing a species’ invasion history is challenging. Here, we applied genetic clustering methods and explicit admixture tests combined with ABC models and Machine Learning algorithms to describe the phylogeography of native and invasive populations and infer the most probable demographic invasion scenarios of Pseudorasbora parva, a highly invasive freshwater fish and the healthy carrier of a novel lethal fungi-like pathogen (Sphaerothecum destruens), which is responsible for the decline of several fish species in Europe. We found that the current genetic structuring of the native P. parva range has been shaped by waves of gene flow originating from southern and northern Chinese populations. Furthermore, our results strongly suggest that the invasive genetic diversity is the outcome of past recurrent global invasion pathways of admixed native populations. Our study also illustrates how the combination of admixture tests, ABC, Machine Learning can be used to detect high-resolution demographic signatures and reconstruct an integrative biological invasion history.

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