Search for: All records

Abstract Characterizing molecular underpinnings of plastic traits and balanced polymorphisms represent 2 important goals of evolutionary biology. Fire ant gynes (pre-reproductive queens) provide an ideal system to study potential links between these phenomena because they exhibit both supergene-mediated polymorphism and nutritional plasticity in weight and colony-founding behaviour. Gynes with the inversion supergene haplotype are lightweight and depend on existing workers to initiate reproduction. Gynes with only the ancestral, non-inverted gene arrangement accumulate more nutrient reserves as adults and, in a distinct colony-founding behaviour, initiate reproduction without help from workers. However, when such gynes overwinter in the natal nest they develop an environmentally induced lightweight phenotype and colony-founding behaviour, similar to gynes with the inversion haplotype that have not overwintered. To evaluate the extent of shared mechanisms between plasticity and balanced polymorphism in fire ant gyne traits, we assessed whether genes with expression variation linked to overwintering plasticity may be affected by the evolutionary divergence between supergene haplotypes. To do so, we first compared transcriptional profiles of brains and ovaries from overwintered and non-overwintered gynes to identify plasticity-associated genes. These genes were enriched for metabolic and behavioural functions. Next, we compared plasticity-associated genes to those differentially expressed by supergene genotype, revealing a significant overlap of the 2 sets in ovarian tissues. We also identified sequence substitutions between supergene variants of multiple plasticity-associated genes, consistent with a scenario in which an ancestrally plastic phenotype responsive to an environmental condition became increasingly genetically regulated. 

Critical particle size can be determined with known surface energy. The surface enthalpy of yttrium titanate pyrochlores was determined to be 4.07 ± 0.32 J m⁻² by calorimetry, and the lower limit of critical particle size for this is around 5.0 nm. 

Frogs are ideal organisms for studying sex chromosome evolution because of their diversity in sex chromosome differentiation and sex-determination systems. We review 222 anuran frogs, spanning ~220 Myr of divergence, with characterized sex chromosomes, and discuss their evolution, phylogenetic distribution and transitions between homomorphic and heteromorphic states, as well as between sex-determination systems. Most (~75%) anurans have homomorphic sex chromosomes, with XY systems being three times more common than ZW systems. Most remaining anurans (~25%) have heteromorphic sex chromosomes, with XY and ZW systems almost equally represented. There are Y-autosome fusions in 11 species, and no W-/Z-/X-autosome fusions are known. The phylogeny represents at least 19 transitions between sex-determination systems and at least 16 cases of independent evolution of heteromorphic sex chromosomes from homomorphy, the likely ancestral state. Five lineages mostly have heteromorphic sex chromosomes, which might have evolved due to demographic and sexual selection attributes of those lineages. Males do not recombine over most of their genome, regardless of which is the heterogametic sex. Nevertheless, telomere-restricted recombination between ZW chromosomes has evolved at least once. More comparative genomic studies are needed to understand the evolutionary trajectories of sex chromosomes among frog lineages, especially in the ZW systems. 

Abstract Reproduction is a fundamental aspect of life that affects all levels of biology, from genomes and development to population dynamics and diversification. The first Tree of Sex database synthesized a vast diversity of reproductive strategies and their intriguing distribution throughout eukaryotes. A decade on, we are reviving this initiative and greatly expanding its scope to provide the most comprehensive integration of knowledge on eukaryotic reproduction to date. In this perspective, we first identify important gaps in our current knowledge of reproductive strategies across eukaryotes. We then highlight a selection of questions that will benefit most from this new Tree of Sex project, including those related to the evolution of sex, modes of sex determination, sex chromosomes, and the consequences of various reproductive strategies. Finally, we outline our vision for the new Tree of Sex database and the consortium that will create it (treeofsex.org). The new database will cover all Eukaryota and include a wide selection of biological traits. It will also incorporate genomic data types that were scarce or non-existent at the time of the first Tree of Sex initiative. The new database will be publicly accessible, stable, and self-sustaining, thus greatly improving the accessibility of reproductive knowledge to researchers across disciplines for years to come. Lastly, the consortium will persist after the database is created to serve as a collaborative framework for research, prioritizing ethical standards in the collection, use, and sharing of reproductive data. The new Tree of Sex consortium is open, and we encourage all who are interested in this topic to join us. 

Boron displays many unusual structural and bonding properties due to its electron deficiency. Here we show that a boron atom in a boron monoxide cluster (B 9 O − ) exhibits transition-metal-like properties. Temperature-dependent photoelectron spectroscopy provided evidence of the existence of two isomers for B 9 O − : the main isomer has an adiabatic detachment energy (ADE) of 4.19 eV and a higher energy isomer with an ADE of 3.59 eV. The global minimum of B 9 O − is found surprisingly to be an umbrella-like structure ( C 6v , 1 A 1 ) and its simulated spectrum agrees well with that of the main isomer observed. A low-lying isomer ( C s , 1 A′) consisting of a BO unit bonded to a disk-like B 8 cluster agrees well with the 3.59 eV ADE species. The unexpected umbrella-like global minimum of B 9 O − can be viewed as a central boron atom coordinated by a η 7 -B 7 ligand on one side and a BO ligand on the other side, [(η 7 -B 7 )-B-BO] − . The central B atom is found to share its valence electrons with the B 7 unit to fulfill double aromaticity, similar to that in half-sandwich [(η 7 -B 7 )-Zn-CO] − or [(η 7 -B 7 )-Fe(CO) 3 ] − transition-metal complexes. The ability of boron to form a half-sandwich complex with an aromatic ligand, a prototypical property of transition metals, brings out new metallomimetic properties of boron.