Biology subjects

Grandjean, F.

Publications and source records attributed to Grandjean, F..

4 recordsLinked to original sources

bioRxiv2023

Temporal stability of sex ratio distorter prevalence in natural populations of the isopod Armadillidium vulgare

AbstractIn the terrestrial isopod Armadillidium vulgare, many females produce progenies with female-biased sex ratios due to two feminizing sex ratio distorters (SRD): Wolbachia endosymbionts and a nuclear non-mendelian locus called the f element. To investigate the potential impact of these SRD on the evolution of host sex determination, we analyzed their temporal distribution in six A. vulgare populations sampled up to six times over 12 years, for a total of 29 time points. SRD distribution was heterogeneous among populations despite their close geographic locations, so that when one SRD was frequent in a population, the other SRD was rare. In contrast with spatial heterogeneity, our results overall did not reveal substantial temporal variability in SRD prevalence within populations, suggesting equilibria in SRD evolutionary dynamics may have been reached or nearly so. Temporal stability was also generally reflected in mitochondrial and nuclear variation. Nevertheless, in a population, a Wolbachia strain replacement coincided with changes in mitochondrial composition but no change in nuclear composition, thus constituting a typical example of mitochondrial sweep caused by endosymbiont rise in frequency. Rare incongruence between Wolbachia strains and mitochondrial haplotypes suggested the occurrence of intraspecific horizontal transmission, making it a biologically relevant parameter for Wolbachia evolutionary dynamics in A. vulgare. Overall, our results provide an empirical basis for future studies on SRD evolutionary dynamics in the context of multiple sex determination factors co-existing within a single species, to ultimately evaluate the impact of SRD on the evolution of host sex determination mechanisms and sex chromosomes.

evolutionary biology↗

bioRxiv2022

Distribution of sex ratio distorters in natural populations of the isopod Armadillidium vulgare

In the isopod Armadillidium vulgare, many females produce progenies with female-biased sex ratios, due to two feminizing sex ratio distorters (SRD): Wolbachia endosymbionts and the f element. We investigated the distribution and population dynamics of these SRD and mitochondrial DNA variation in 16 populations from Europe and Japan. Confirming and extending results from the 1990s, we found that the SRD are present at variable frequencies in populations, and that the f element is overall more frequent than Wolbachia. The two SRD never co-occur at high frequency in any population, suggesting an apparent mutual exclusion. We also detected Wolbachia or the f element in some males, which likely reflects insufficient titer to induce feminization or presence of masculinizing alleles. Our results are consistent with a single integration event of a Wolbachia genome in the A. vulgare genome at the origin of the f element, which contradicts an earlier hypothesis of frequent losses and gains. We identified strong linkage between Wolbachia strains and mitochondrial haplotypes, but no association between the f element and mitochondrial background. Our results open new perspectives on SRD evolutionary dynamics in A. vulgare, the evolution of genetic conflicts and their impact on the variability of sex determination systems.

evolutionary biology↗

bioRxiv2020

More from less: Genome skimming for nuclear markers for animal phylogenomics, a case study using decapod crustaceans

Low coverage genome sequencing is rapid and cost-effective for recovering complete mitochondrial genomes for animal phylogenomics. The recovery of high copy number nuclear genes, including histone H3, 18S and 28S ribosomal RNAs, is also possible using this approach. In this study, we explore the potential of the genome skimming (GS) to recover additional nuclear genes from shallow sequencing projects. Using an in silico baited approach, we recover three additional core histone genes (H2A, H2B and H4) from our existing collection of low coverage decapod crustacean dataset (99 species, 69 genera, 38 families, 10 infraorders). Phylogenetic analyses based on various combinations of mitochondrial and nuclear genes for the entire decapod dataset and 40 species of crayfish (Infraorder Astacidea) found that the evolutionary rates for different classes of genes varied widely. The highlight being a very high level of congruence found between trees from the six nuclear genes and those derived from the mitogenome sequences for freshwater crayfish. These findings indicate that nuclear genes recovered from the same genome skimming datasets designed to obtain mitogenomes can be used to support more robust and comprehensive phylogenetic analyses. Further, a search for additional intron-less nuclear genes identified several high copy number genes across the decapod dataset and recovery of NaK, PEPCK and GAPDH gene fragments is possible at slightly elevated coverage, suggesting the potential and utility of GS in recovering even more nuclear genetic information for phylogenetic studies from these inexpensive and increasingly abundant datasets.

evolutionary biology↗

bioRxiv2018

A story of nasal horns: A new species of Iguana Laurenti, 1768 (Squamata, Iguanidae) in Saint Lucia, St Vincent & the Grenadines, and Grenada (Southern Lesser Antilles) and its implications for the taxonomy of the genus Iguana

The Lesser Antilles, in the Eastern Caribbean, were long considered to have only two species in the genus Iguana Laurenti 1768: the Lesser Antillean iguana Iguana delicatissima, which is endemic to parts of the Lesser Antilles, and the common green iguana Iguana iguana, which also occurs throughout Central and South America. However, herpetologists and reptile collectors have pointed out strong physical differences between some of the island populations of Iguana iguana and those from the continent. Drawing on both morphological and genetic data, this paper describes a third species Iguana insularis sp. nov. from the southern Lesser Antilles, specifically the countries of Saint Lucia, St Vincent & the Grenadines, and Grenada. The new species is described based on the following unique combination of characters: Presence of high median and medium to small lateral horns on the snout; Small subtympanic plate not exceeding 20% of the eardrum size; Two or three scales of decreasing size anterior to the subtympanic plate; Fewer than ten small to medium triangular gular spikes; Medium sized dewlap; Low number of small to medium dispersed nuchal tubercles; Dark brown iris, with the white of the eye visible; Oval, prominent nostril; Short and relatively flat head; High dorsal spines; No swelling of the jowls in reproductively active males; Colour of head, body and tail changing from green to pale grey or creamy white in old adults; Vertical black stripes on body and tail, fading with age in some populations. This paper furthermore distinguishes two subspecies: Iguana insularis insularis from the Grenada Bank (comprising Grenada and the Grenadine islands), and Iguana insularis sanctaluciae from Saint Lucia. The form on the island of Saint Vincent has not been identified. Both subspecies are globally threatened by unsustainable hunting (including the pet trade) and by invasive alien species, including hybridization from invasive iguanas from South and Central America (I. iguana and I. rhinolopha, considered here as full species) that have become established in all three countries. The authors call for stronger measures to conserve the remaining purebred Iguana insularis sp. nov. throughout its range and for further research to identify other cryptic species and subspecies of Iguana in the Lesser Antilles.

zoology↗