We have previously reported that Bmdsx, a homologue of the sex-determining gene doublesex (dsx), was sex-specifically expressed in various tissues of the silkworm. The primary transcript of Bmdsx is alternatively spliced in males and females to yield sex-specific mRNAs that encode male-specific (BmDSXM) and female-specific (BmDSXF) polypeptides. In the studies reported here, we expressed BmDSXF in males from a ubiquitous promoter and examined its regulatory activities. We show that BmDSXF functions as a positive regulator of the hexameric storage protein termed SP1 and vitellogenin genes that are predominantly expressed in females. We also show that expression of BmdsxF in males results in the repression of the pheromone-binding protein gene that is preferentially expressed in males. Gel-mobility shift assays demonstrated that BmDSX proteins bind to the sequence (ACATTGT) between −95 and −89 nt relative to the transcriptional initiation site of the vitellogenin gene. These results strongly suggest that Bmdsx is a final regulatory gene in the hierarchy of regulatory genes controlling the expression of female-specific protein in Bombyx mori.

Transgenic Analysis of the Biological Functions of a Doublesex Homologue in Bombyx mori

Ecosystem engineers have been widely studied for terrestrial systems, but global trends in research encompassing the range of taxa and functions have not previously been synthesised. We reviewed contemporary understanding of engineer fauna in terrestrial habitats and assessed the methods used to document patterns and processes, asking: (a) which species act as ecosystem engineers and with whom do they interact? (b) What are the impacts of ecosystem engineers in terrestrial habitats and how are they distributed? (c) What are the primary methods used to examine engineer effects and how have these developed over time? We considered the strengths, weaknesses and gaps in knowledge related to each of these questions and suggested a conceptual framework to delineate "significant impacts" of engineering interactions for all terrestrial animals. We collected peer-reviewed publications examining ecosystem engineer impacts and created a database of engineer species to assess experimental approaches and any additional covariates that influenced the magnitude of engineer impacts. One hundred and twenty-two species from 28 orders were identified as ecosystem engineers, performing five ecological functions. Burrowing mammals were the most researched group (27%). Half of all studies occurred in dry/arid habitats. Mensurative studies comparing sites with and without engineers (80%) were more common than manipulative studies (20%). These provided a broad framework for predicting engineer impacts upon abundance and species diversity. However, the roles of confounding factors, processes driving these patterns and the consequences of experimentally adjusting variables, such as engineer density, have been neglected. True spatial and temporal replication has also been limited, particularly for emerging studies of engineer reintroductions. Climate change and habitat modification will challenge the roles that engineers play in regulating ecosystems, and these will become important avenues for future research. We recommend future studies include simulation of engineer effects and experimental manipulation of engineer densities to determine the potential for ecological cascades through trophic and engineering pathways due to functional decline. We also recommend improving knowledge of long-term engineering effects and replication of engineer reintroductions across landscapes to better understand how large-scale ecological gradients alter the magnitude of engineering impacts.

https://besjournals.onlinelibrary.wiley.com/doi/pdf/10.1111/1365-2656.12819

A global database and “state of the field” review of research into ecosystem engineering by land animals

Climatic parameters are able to influence the timing of phenological events affecting the degree of synchrony among plant species, their interactions, and reproductive success. Shrubs of Malpighiaceae family in the Brazilian Tropical Savanna present sequential flowering phenology. We verified variations in climatic factors (temperature and precipitation) over a period of 10 years (2005–2014) and correlated them with the onset of flowering of four of these Malpighiaceae species. Furthermore, we tested whether the phenological synchronization among species has changed over time affecting the herbivory and fruit set. Herbivory and fruit production were recorded during three reproductive seasons (2008/2009, 2011/2012, 2013/2014). We developed a mathematical model to estimate the flower and fruit production in response to phenological changes for the next 5 years. Results show that climatic factors changed, influencing the onset of species flowering. The degree of overlap among species also changed and the effects on species interactions were species specific. The mathematical model successfully presented a tendency on flower and fruit production contributing to the predictions of the outcomes in response to phenological changes. We confirm the effects of climate changes on plant phenological events and the importance of feature plasticity for better performance of species.

Climate changes affecting biotic interactions, phenology, and reproductive success in a savanna community over a 10-year period

Ant pollination of Paepalanthus lundii (Eriocaulaceae) in Brazilian savanna.

Queen pheromones are chemical signals that mediate reproductive division of labor in eusocial animals. Remarkably, queen pheromones are composed of identical or chemically similar compounds in some ants, wasps and bees, even though these taxa diverged >150MYA and evolved queens and workers independently. Here, we measure the transcriptomic consequences of experimental exposure to queen pheromones in workers from two ant and two bee species (genera: Lasius, Apis, Bombus), and test whether they are similar across species. Queen pheromone exposure affected transcription and splicing at many loci. Many genes responded consistently in multiple species, and the set of pheromone-sensitive genes was enriched for functions relating to lipid biosynthesis and transport, olfaction, production of cuticle, oogenesis, and histone (de)acetylation. Pheromone-sensitive genes tend to be evolutionarily ancient, positively selected, peripheral in the gene coexpression network, hypomethylated, and caste-specific in their expression. Our results reveal how queen pheromones achieve their effects, and suggest that ants and bees use similar genetic modules to achieve reproductive division of labor. Queen pheromones are used by eusocial insects to regulate all aspects of colony life. Here, Holman et al. compare the effects of queen pheromone on gene expression and splicing in four eusocial insect species, giving insight into the mechanism and evolution of division of reproductive labour.

/pdf/comparative-transcriptomics-of-social-insect-queen-3oqvlenr9e.pdf

Comparative transcriptomics of social insect queen pheromones

1. Variation in plant phenology allows plants to escape from herbivory. Insect herbivores manipulate their host plants by producing shelters, which they inhabit, and are protected against natural enemies and/or unfavourable environmental conditions. Environmental modifications induced by living organisms are characterised as ecosystem engineering.



2. In the Brazilian savanna, the interaction between the Malpighiaceae shrub, Byrsonima intermedia, and its main herbivore, the caterpillar Cerconota achatina, a shelter-building organism, was studied.



3. It was focused on whether the phenological development of the host plant affects the caterpillars' infestation, and whether C. achatina acts as an ecosystem engineer by building shelters. All plant variables (number of leaves, flowers, buds, fruits and herbivores) were measured fortnightly. Phenological data were correlated with climatic information. The impact of the caterpillars acting as ecosystem engineers was measured experimentally.



4. Infestation levels of C. achatina covaried with the phenology of their host plant B. intermedia. It suggests that plant phenology might be an important factor in determining the abundances of this ecosystem engineer species.

Host plant phenology may determine the abundance of an ecosystem engineering herbivore in a tropical savanna

Studies on animal behaviour have suggested a link between personality and energy expenditure. However, most models assume constant variation within individuals, even though individuals vary between observations. Such variation is called intraindividual variation in behaviour (IIV). We investigate if IIV in the duration of the startle response is associated with metabolic rates (MR) in the hermit crab Pagurus bernhardus . We repeatedly measured startle response durations and MR during each observation. We used double hierarchical generalized linear models to ask whether among and IIV in behaviour was underpinned by MR. We found no association between the mean duration of the startle responses and either routine MR or MR during startle response. Nevertheless, we found that IIV increased with MR during startle responses and decreased with routine MR. These results indicate that crabs with higher MR during startle responses behave less predictably, and that predictability is reduced during exposure to elevated temperatures.

/pdf/the-opposite-effects-of-routine-metabolic-rate-and-metabolic-2of4oal87y.pdf

The opposite effects of routine metabolic rate and metabolic rate during startle responses on variation in the predictability of behaviour in hermit crabs

An animal's decision to enter into a fight depends on the interaction between perceived resource value (V) and fighting costs (C). Both could be altered by predictable environmental fluctuations. For intertidal marine animals, such as the sea anemone Actinia equina, exposure to high flow during the tidal cycle may increase V by bringing more food. It may also increase C via energy expenditure needed to attach to the substrate. We asked whether simulated tidal cycles would alter decisions in fighting A. equina We exposed some individuals to still water and others to simulated tidal cycles. To gain insights into V, we measured their startle responses before and after exposure to the treatments, before staging dyadic fights. Individuals exposed to flow present shorter startle responses, suggesting that flowing water indicates high V compared with still water. A higher probability of winning against no-flow individuals and longer contests between flow individuals suggests that increased V increases persistence. However, encounters between flow individuals were less likely to escalate, suggesting that C is not directly related to V. Therefore, predictable environmental cycles alter V and C, but in complex ways.

https://royalsocietypublishing.org/doi/pdf/10.1098/rsbl.2017.0011

How does environment influence fighting? The effects of tidal flow on resource value and fighting costs in sea anemones

Eusociality, the ultimate level of social organization, requires reproductive division of labor, and a sophisticated system of communication to maintain societal homeostasis. Reproductive division of labor is maintained by physiological differences between reproductive and sterile castes, typically dictated by pheromonal queen fertility signals that suppress worker reproduction. Intriguingly, reproduction and pheromonal signalling share regulatory machinery across insects.The gene Doublesex (Dsx) controls somatic sex determination and differentiation, including the development of ovaries and secondary sexual characteristics, such as pheromonal signalling. We hypothesized that this regulatory network was co-opted during eusocial evolution to regulate reproductive division of labor. Taking advantage of the breakdown in reproductive division of labor that occurs in honey bees when workers commence to lay eggs in the absence of a queen, we knocked down Dsx to observe effects on ovary development and fertility signal production. As expected, treated workers had lower levels of egg yolk protein, for which Dsx is a cis-regulatory enhancer in other insects, and greatly reduced ovary development. Also as expected, while control workers increased their levels of pheromonal fertility signals, treated workers did not, confirming the role of Dsx in regulating pheromone biosynthesis. We further found that Dsx is part of a large network enriched for regulatory proteins, which is also involved during early larval development, and upregulated in queen-destined larvae. Thus, the ancient developmental framework controlling sex specification and reproduction in solitary insects has been exapted for eusociality, forming the basis for reproductive division of labor and pheromonal signalling pathways.

/pdf/the-doublesex-sex-determination-pathway-regulates-jfjaaj2ski.pdf

The Doublesex sex determination pathway regulates reproductive division of labor in honey bees

Venoms have convergently evolved in all major animal lineages and are ideal candidates to unravel the genomic processes underlying convergent trait evolution. However, few animal groups have been studied in detail, and large-scale comparative genomic analyses to address toxin gene evolution are rare. The hyper-diverse hymenopterans are the most speciose group of venomous animals, but the origin of their toxin genes has been largely overlooked. We combined proteo-transcriptomics with comparative genomics compiling an up-to-date list of core bee venom proteins to investigate the origin of 11 venom genes in 30 hymenopteran genomes including two newly sequenced genomes of stingless bees. We found a more distinct pattern in which toxin genes originated predominantly by single gene co-option, a prevalent mechanism in parasitoid wasps. These are always accompanied by parallel expansion events in other bee and hymenopteran sister gene groups. The short toxic peptides melittin and apamin appear to be unique to bees, a result supported by a novel machine learning approach. Based on the syntenic pattern we propose here Anthophilin1 as a bee-unique gene family that includes apamin and MCDP. It appears that bees co-adapted their venom genes which predominantly already existed before the aculeate ovipositor evolved to a stinger which exclusively injects venom. Our results provide insight into the large-scale evolution of bee venom compounds, and we present here the first study revealing general processes of venom evolution at a comparative genomic level for this mega-diverse Hymenoptera.

/pdf/bee-core-venom-genes-predominantly-originated-before-czhbxzj7.pdf

Mariana Velasque

Papers

Host plant phenology may determine the abundance of an ecosystem engineering herbivore in a tropical savanna

The opposite effects of routine metabolic rate and metabolic rate during startle responses on variation in the predictability of behaviour in hermit crabs

How does environment influence fighting? The effects of tidal flow on resource value and fighting costs in sea anemones

The Doublesex sex determination pathway regulates reproductive division of labor in honey bees

Bee core venom genes predominantly originated before aculeate stingers evolved