Unbalanced biparental care during colony foundation in two subterranean termites

Parental care is a major component of reproduction in social organisms, particularly during the foundation steps. Because investment into parental care is often costly, each parent is predicted to maximize its fitness by providing less care than its partner. However, this sexual conflict is expected to be low in species with lifelong monogamy, because the fitness of each parent is typically tied to the other's input. Somewhat surprisingly, the outcomes of this tug‐of‐war between maternal and paternal investments have received important attention in vertebrate species, but remain less known in invertebrates. In this study, we investigated how queens and kings share their investment into parental care and other social interactions during colony foundation in two termites with lifelong monogamy: the invasive species Reticulitermes flavipes and the native species R. grassei. Behaviors of royal pairs were recorded during six months using a non‐invasive approach. Our results showed that queens and kings exhibit unbalanced investment in terms of grooming, antennation, trophallaxis, and vibration behavior. Moreover, both parents show behavioral differences toward their partner or their descendants. Our results also revealed differences among species, with R. flavipes exhibiting shorter periods of grooming and antennation toward eggs or partners. They also did more stomodeal trophallaxis and less vibration behavior. Overall, this study emphasizes that despite lifelong monogamy, the two parents are not equally involved in the measured forms of parental care and suggests that kings might be specialized in other tasks. It also indicates that males could play a central, yet poorly studied role in the evolution and maintenance of the eusocial organization.     

miR-21 differentially regulates IL-1β and IL-10 expression in human decidual cells infected with streptococcus B

Intrauterine infections caused by bacteria like group B streptococcus (GBS) and the subsequent activation of the maternal inflammatory response have been long suspected to be the underlying cause of preterm labor. The inflammatory network triggered by maternal decidua has been widely described and includes the secretion of pro- and anti-inflammatory cytokines as IL-1β and IL-10; however, the mechanisms that regulate their secretion have not been completely elucidated. MicroRNAs (miRNAs) are critical modulators of the inflammatory response by regulating cytokine expression in several cell types. Here, we explored the role of miR-21 in the expression of IL-1β and IL-10 in human decidual stromal cells (DSCs) exposed in vitro to GBS. We observed that IL1B and IL10 expression at the mRNA level was increased in DSCs after GBS infection. IL-10 but not IL-1β secretion was detected in the culture supernatants. We found a higher miR-21 expression (22-fold) in infected DSCs as compared with non-infected cells. miR-21 functional analysis revealed that DSCs transfected with an antagomiR vs. miR-21 significantly increased the secretion of IL-1β but decreased that of IL-10 in DSCs cells infected with GBS. Our results suggest that miR-21 participates in balancing the inflammatory response in infected decidua through at least IL-1β and IL-10 regulation. This is the first study attributing a functional role of miR-21 in the regulation of key molecules involved in the inflammatory response in infected DSCs, providing new insights into the epigenetic control of human decidual inflammation.     

Individual‐ versus group‐optimality in the production of secreted bacterial compounds

How unicellular organisms optimize the production of compounds is a fundamental biological question. While it is typically thought that production is optimized at the individual‐cell level, secreted compounds could also allow for optimization at the group level, leading to a division of labor where a subset of cells produces and shares the compound with everyone. Using mathematical modeling, we show that the evolution of such division of labor depends on the cost function of compound production. Specifically, for any trait with saturating benefits, linear costs promote the evolution of uniform production levels across cells. Conversely, production costs that diminish with higher output levels favor the evolution of specialization–especially when compound shareability is high. When experimentally testing these predictions with pyoverdine, a secreted iron‐scavenging compound produced by Pseudomonas aeruginosa, we found linear costs and, consistent with our model, detected uniform pyoverdine production levels across cells. We conclude that for shared compounds with saturating benefits, the evolution of division of labor is facilitated by a diminishing cost function. More generally, we note that shifts in the level of selection from individuals to groups do not solely require cooperation, but critically depend on mechanistic factors, including the distribution of compound synthesis costs.     

The evolution of female multiple mating in social hymenoptera

Abstract The evolution of female multiple mating is a highly controversial topic, especially in social insects. Here we analyze, using comparative analyses and simulation models, the merits of two major contending hypotheses for the adaptive value of polyandry in this group. The hypotheses maintain that, respectively, the resulting genotypic diversity among offspring within a colony: (1) mitigates against the effects of parasites; or (2) favors adaptive division of labor. Only two of 11 phylogenetically uncontrolled comparative analyses supported an association between polyandry and the complexity of division of labor (measured here using worker caste polymorphism or polyethism) as proposed by hypothesis 2, and after controlling for phylogeny there were no significant associations. In contrast, a previous study demonstrated such an association for parasite load as expected under hypothesis 1. In addition, we used simulation models to track the spread of an initially rare allele for double mating in a population of single-mating alleles, thus analyzing the crucial first step from monandry to polyandry. We find that double mating evolves consistently under antagonistic coevolution given that parasites exert sufficient selection intensity. In contrast, selection for enhanced division of labor resulted in only an erratic appearance of polyandry in highly (and mostly negatively) autocorrelated environments where no coevolutionary dynamics were allowed. Together, we interpret these results to suggest that parasites, and the antagonistic coevolutionary pressures they exert, may play an important role in the evolution of polyandry in social hymenopteran populations.     

Does terbutaline damage the developing heart?

BACKGROUND: β₂‐Adrenoceptor (βAR) agonists, such as terbutaline, are widely used to arrest preterm labor. They also cross the placenta where they stimulate receptors in fetal tissues, which in turn use βAR input for trophic control of cell replication and differentiation. METHODS: As rats are altricial, we administered terbutaline in two different postnatal exposure periods (10 mg/kg given daily on Days 2–5 or 11–14). RESULTS: Hearts were examined twenty‐four hours after the last dose and on postnatal day 30 for cardiac damage. Neither treatment paradigm caused an increase in cardiac abnormalities compared to controls but quantitative analysis of the number of nuclei indicated reductions in females. CONCLUSIONS: These findings do not support earlier case reports of outright myocardial necrosis after terbutaline tocolysis in human infants. Nevertheless, the significant statistical association between terbutaline and cardiac anomalies in epidemiological studies suggest that terbutaline may sensitize the developing heart to other insults that affect development. Birth Defects Res B 68:449–455, 2003. © 2003 Wiley‐Liss, Inc.     

Labor specialization and the formation of markets for food in a Shipibo subsistence economy

Traditionally, the Shipibo economy was subsistence-based with shifting cultivation supplying calories, principally in the form of plantains and root crops, while fishing and hunting provided animal proteins to the diet. Some men, who recently began producing rice for sale in regional markets, now allocate less time to wild food procurement. Moreover, this trend has been accompanied by the nucleation of households, a growing cash market for agricultural labor, and the intravillage sale of faunal foods. This paper shows that with cash cropping, some Shipibo now freely distribute less food to others in relation to the amount they produce. To account for this change, a theory is developed based on time allocation and patterns of economic behavior reported throughout the Amazon. This theory is then applied to explain specialization and the formation of cash markets for food labor among the Shipibo.     

Sucrose response thresholds of honey bee (Apis mellifera) foragers are not modulated by brood ester pheromone

Division of labor is a hallmark of eusocial insects and their ecological success can be attributed to it. Honey bee division of labor proceeds along a stereotypical ontogenetic path based on age, modulated by various internal and external stimuli. Brood pheromone is a major social pheromone of the honey bee that has been shown to affect honey bee division of labor. It elicits several physiological and behavioral responses; notably, regulating the timing of the switch from performing in-hive tasks to the initiation of foraging. Additionally, brood pheromone affects future foraging choice. In honey bees, sucrose response threshold is a physiological correlate of age of first foraging and foraging choice. Brood pheromone has been shown to modulate sucrose response threshold in young bees, but its effects on sucrose response thresholds of bees in advanced behavioral states (foragers) are not known. In this study we examined the sucrose response thresholds of two different task groups, foragers (pollen and non-pollen) and non-foraging bees, in response to honey bee brood pheromone. Sucrose response thresholds were not significantly different between brood pheromone treatment and controls among both non-pollen and pollen foragers. However, the sucrose response threshold of non-foraging bees was significantly higher in the brood pheromone treatment group than in the control group. The switch to foraging task is considered a terminal one, with honey bee lifespan being determined at least partially by risks and stress accompanying foraging. Our results indicate that foragers are physiologically resistant to brood pheromone priming of sucrose response thresholds.     

The evolution of queen control over worker reproduction in the social Hymenoptera

A trademark of eusocial insect species is reproductive division of labor, in which workers forego their own reproduction while the queen produces almost all offspring. The presence of the queen is key for maintaining social harmony, but the specific role of the queen in the evolution of eusociality remains unclear. A long‐discussed scenario is that a queen either behaviorally or chemically sterilizes her workers. However, the demographic and ecological conditions that enable such manipulation are still debated. We study a simple model of evolutionary dynamics based on haplodiploid genetics. Our model is set in the commonly observed case where workers have lost the ability to lay female (diploid) eggs by mating, but retain the ability to lay male (haploid) eggs. We consider a mutation that acts in a queen, causing her to control the reproductive behavior of her workers. Our mathematical analysis yields precise conditions for the evolutionary emergence and stability of queen‐induced worker sterility. These conditions do not depend on the queen's mating frequency. We find that queen control is always established if it increases colony reproductive efficiency, but can evolve even if it decreases colony efficiency. We further derive the conditions under which queen control is evolutionarily stable against invasion by mutant workers who have recovered the ability to lay male eggs.     

青藏高原气候变化对农牧民开垦的影响

自1980年代后期以来,青藏高原持续变暖趋势明显,且增温幅度高于我国其他地区。基于遥感数据和种植适宜性模型的一些研究表明,该地区足够的农业热量资源增加了适宜耕种土地的面积,为农牧民的开垦行为创造了有利的条件。然而,对农牧民是否开垦以及开垦原因的实证研究,以及农牧民如何平衡气候变化带来的开垦机遇、风险和人口压力,仍然缺少认识。以青藏高原的3个典型产粮区域("一江两河"地区、河湟谷地、壤塘县)为研究区,利用605户农户家庭调研数据,分析了影响农牧民开垦行为的影响因素。计量结果表明,农牧民感知冬季持续时间的整体变化趋势、家庭总人口、抚养比与农牧民开垦行为呈显著正相关关系;农牧民感知降水的整体变化趋势、人均打工年收入、户主受教育水平、是否借贷、居住地距集镇距离与农牧民开垦行为呈显著负相关关系。随着城镇化的不断加快,农牧民对非农工作的认可度越来越高,加之政府的管制,使得开垦现象并不普遍。由于农牧民的开垦对青藏高原的生态环境极有可能造成不可逆的负面影响,应该提供更多的非农就业机会,促进农业集约化,加强监管,以降低开垦的可能性。