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1. Gut microbiome composition of wild western lowland gorillas is associated with individual age and sex factors

   https://doi.org/10.1002/ajpa.23842  

   Pafčo, Barbora ; Sharma, Ashok K. ; Petrželková, Klára J. ; Vlčková, Klára ; Todd, Angelique ; Yeoman, Carl J. ; Wilson, Brenda A. ; Stumpf, Rebecca ; White, Bryan A. ; Nelson, Karen E. ; et al ( April 2019 , American Journal of Physical Anthropology)

   Environmental and ecological factors, such as geographic range, anthropogenic pressure, group identity, and feeding behavior are known to influence the gastrointestinal microbiomes of great apes. However, the influence of individual host traits such as age and sex, given specific dietary and social constraints, has been less studied. The objective of this investigation was to determine the associations between an individual's age and sex on the diversity and composition of the gut microbiome in wild western lowland gorillas.

   Publicly available 16S rRNA data generated from fecal samples of different groups ofGorilla gorillagorillain the Central African Republic were downloaded and bioinformatically processed. The groups analyzed included habituated, partially habituated and unhabituated gorillas, sampled during low fruit (dry,n = 28) and high fruit (wet,n = 82) seasons. Microbial community analyses (alpha and beta diversity and analyses of discriminant taxa), in tandem with network‐wide approaches, were used to (a) mine for specific age and sex based differences in gut bacterial community composition and to (b) asses for gut community modularity and bacterial taxa with potential functional roles, in the context of seasonal food variation, and social group affiliation.

   Both age and sex significantly influenced gut microbiome diversity and composition in wild western lowland gorillas. However, the largest differences were observed between infants and adults in habituated groups and between adults and immature gorillas within all groups, and across dry and wet seasons. Specifically, although adults always showed greater bacterial richness than infants and immature gorillas, network‐wide analyses showed higher microbial community complexity and modularity in the infant gorilla gut. Sex‐based microbiome differences were not evident among adults, being only detected among immature gorillas.

   The results presented point to a dynamic gut microbiome inGorillaspp., associated with ontogeny and individual development. Of note, the gut microbiomes of breastfeeding infants seemed to reflect early exposure to complex, herbaceous vegetation. Whether increased compositional complexity of the infant gorilla gut microbiome is an adaptive response to an energy‐limited diet and an underdeveloped gut needs to be further tested. Overall, age and sex based gut microbiome differences, as shown here, maybe mainly attributed to access to specific feeding sources, and social interactions between individuals within groups.

    

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2. Longitudinal dynamics and behavioural correlates of telomeres in male wire‐tailed manakins

   https://doi.org/10.1111/1365-2435.13715  

   Vernasco, Ben J. ; Dakin, Roslyn ; Majer, Ariana D. ; Haussmann, Mark F. ; Brandt Ryder, T. ; Moore, Ignacio T. ; Angelier, ed., Frédéric ( December 2020 , Functional Ecology)

   Building on the predictions of state‐dependent life‐history theory, telomeres are hypothesized to either correlate with or function as an adaptive, proximate mediator of an individual's behaviour and life‐history strategy. To further understand the relationship between telomeres, behaviour and life‐history strategies, we measured male behaviour, telomere lengths and telomere dynamics in a free‐living population of known‐age, male wire‐tailed manakinsPipra filicauda.

   Male wire‐tailed manakins perform coordinated displays with other males at leks and these displays form the basis of long‐term coalition partnerships. Males exhibit consistent individual differences in the number of social partners within their social network and the frequency of social interactions. Male sociality is also positively correlated with both social rise and reproductive success.

   We measured male behaviour using a telemetry‐based, proximity datalogging system and blood telomere lengths were quantified using qPCR. We examined the relationships between telomere length, telomere dynamics, social status, and male behaviour. We also quantified the repeatability of telomere lengths, examined age‐related changes in telomere length, and tested for instances of telomere elongation that exceed residual error in telomere length.

   Telomere length was found to be highly repeatable. More social males exhibited shorter telomeres and higher rates of telomere attrition. Telomeres did not significantly vary with age within or between individuals in either of the male social classes. Two out of 25 individuals exhibited patterns telomere elongation that exceeded residual error in telomere measurements.

   Here we show that telomeres consistently vary between male wire‐tailed manakins and these differences are related to variation in male social behaviour. In this relatively long‐lived species, telomeres appear to be flexible traits that can increase or decrease in length. Overall, this study provides observational support for the hypothesis that telomeres act as a molecular marker that relates to behaviour in a state‐dependent manner. We also provide insight into the molecular consequences of individual variation in male social behaviour.

   A freePlain Language Summarycan be found within the Supporting Information of this article.

    

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3. Human‐like adrenal development in wild chimpanzees: A longitudinal study of urinary dehydroepiandrosterone‐sulfate and cortisol

   https://doi.org/10.1002/ajp.23064  

   Sabbi, Kris H. ; Muller, Martin N. ; Machanda, Zarin P. ; Otali, Emily ; Fox, Stephanie A. ; Wrangham, Richard W. ; Emery Thompson, Melissa ( November 2019 , American Journal of Primatology)

   The development of the adrenal cortex varies considerably across primates, being most conspicuous in humans, where a functional zona reticularis–the site of dehydroepiandrosterone‐sulfate (DHEA/S) production–does not develop until middle childhood (5–8 years). Prior reports suggest that a human‐like adrenarche, associated with a sharp prepubertal increase in DHEA/S, may only occur in the genusPan. However, the timing and variability in adrenarche in chimpanzees remain poorly described, owing to the lack of longitudinal data, or data from wild populations. Here, we use urine samples from East African chimpanzees (Pan troglodytes schweinfurthii)collected over 20 years at Kanyawara in Kibale National Park, Uganda, to trace the developmental trajectories of DHEAS (n = 1,385 samples, 53 individuals) and cortisol (n = 12,726 samples, 68 individuals). We used generalized additive models (GAM) to investigate the relationship between age, sex, and hormone levels. Adrenarche began earlier in chimpanzees (~2–3 years) compared with what has been reported in humans (6–8 years) and, unlike humans, male and female chimpanzees did not differ significantly in the timing of adrenarche nor in DHEAS concentrations overall. Similar to what has been reported in humans, cortisol production decreased through early life, reaching a nadir around puberty (8–11 years), and a sex difference emerged with males exhibiting higher urinary cortisol levels compared with females by early adulthood (15–16 years). Our study establishes that wild chimpanzees exhibit a human‐like pattern of cortisol production during development and corroborates prior reports from captive chimpanzees of a human‐like adrenarche, accompanied by significant developmental increases in DHEAS. While the role of these developmental hormone shifts are as yet unclear, they have been implicated in stages of rapid behavioral development once thought unique to humans, especially in regard to explaining the divergence of female and male social behavior before pubertal increases in gonadal hormones.

    

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4. The slow emergence of gaze‐ and point‐following: A longitudinal study of infants from 4 to 12 months

   https://doi.org/10.1111/desc.13457  

   Tang, Yueyan ; Gonzalez, Marybel Robledo ; Deák, Gedeon O. ( November 2023 , Developmental Science)

   Acquisition of visual attention‐following skills, notably gaze‐ and point‐following, contributes to infants' ability to share attention with caregivers, which in turn contributes to social learning and communication. However, the development of gaze‐ and point‐following in the first 18 months remains controversial, in part because of different testing protocols and standards. To address this, we longitudinally testedN = 43 low‐risk, North American middle‐class infants' tendency to follow gaze direction, pointing gestures, and gaze‐and‐point combinations. Infants were tested monthly from 4 to 12 months of age. To control motivational differences, infants were taught to expect contingent reward videos in the target locations. No‐cue trials were included to estimate spontaneous target fixation rates. A comparison sample (N = 23) was tested at 9 and 12 months to estimate practice effects. Results showed gradual increases in both gaze‐ and point‐following starting around 7 months, and modest month‐to‐month individual stability from 8 to 12 months. However, attention‐following did not exceed chance levels until after 6 months. Infants rarely followed cues to locations behind them, even at 12 months. Infants followed combined gaze‐and‐point cues more than gaze alone, and followed points at intermediate levels (not reliably different from the other cues). The comparison group's results showed that practice effects did not explain the age‐related increase in attention‐following. The results corroborate and extend previous findings that North American middle‐class infants' attention‐following in controlled laboratory settings increases slowly and incrementally between 6 and 12 months of age.

   A longitudinal experimental study documented the emergence and developmental trajectories of North American middle‐class infants' visual attention‐following skills, including gaze‐following, point‐following, and gaze‐and‐point‐following.

   A new paradigm controlled for factors including motivation, attentiveness, and visual‐search baserates. Motor development was ruled out as a predictor or limiter of the emergence of attention‐following.

   Infants did not follow attention reliably until after 6 months, and following increased slowly from 7 to 12 months.

   Infants' individual trajectories showed modest month‐to‐month stability from 8 to 12 months of age.

    

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5. Simple inheritance, complex regulation: Supergene‐mediated fire ant queen polymorphism

   https://doi.org/10.1111/mec.15581  

   Arsenault, Samuel V. ; King, Joanie T. ; Kay, Sasha ; Lacy, Kip D. ; Ross, Kenneth G. ; Hunt, Brendan G. ( August 2020 , Molecular Ecology)

   The fire antSolenopsis invictaexists in two alternate social forms: monogyne nests contain a single reproductive queen and polygyne nests contain multiple reproductive queens. This colony‐level social polymorphism corresponds with individual differences in queen physiology, queen dispersal patterns and worker discrimination behaviours, all evidently regulated by an inversion‐based supergene that spans more than 13 Mb of a “social chromosome,” contains over 400 protein‐coding genes and rarely undergoes recombination. The specific mechanisms by which this supergene influences expression of the many distinctive features that characterize the alternate forms remain almost wholly unknown. To advance our understanding of these mechanisms, we explore the effects of social chromosome genotype and natal colony social form on gene expression in queens sampled as they embarked on nuptial flights, using RNA‐sequencing of brains and ovaries. We observe a large effect of natal social form, that is, of the social/developmental environment, on gene expression profiles, with similarly substantial effects of genotype, including: (a) supergene‐associated gene upregulation, (b) allele‐specific expression and (c) pronounced extra‐supergenetrans‐regulatory effects. These findings, along with observed spatial variation in differential and allele‐specific expression within the supergene region, highlight the complex gene regulatory landscape that emerged following divergence of the inversion‐mediatedSbhaplotype from its homologue, which presumably largely retained the ancestral gene order. The distinctive supergene‐associated gene expression trajectories we document at the onset of a queen’s reproductive life expand the known record of relevant molecular correlates of a complex social polymorphism and point to putative genetic factors underpinning the alternate social syndromes.

    

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