Bird nests function to protect parents, eggs or offspring against fluctuations in the environment. In Blue Tits (Cyanistes caeruleus) producing first or replacement clutches, we examined relationships between nest height (a measure of nest size) and several parameters of breeding performance that are often quantified in long-term avian field studies. We artificially increased the cost of reproduction in randomly selected females by removing the whole first clutch and nest material after about 5 days of incubation. This experiment resulted in replacement nests. Experimentally increasing the range of breeding conditions across females, we expected to have more power to detect a positive correlation between nest height and breeding success. However, we found that nest height was not significantly related to any of the breeding traits investigated (clutch size, number of hatchlings, number of fledglings, hatching success, fledging success, chick mass), after controlling for factors frequently investigated in long-term monitoring programs and known to influence breeding performance (female age, year, clutch type as a proxy of egg-laying date). We conclude that the identification of the exact underlying mechanisms causing relationships between nest characteristics and breeding performance will require more experimental study and the exploitation of larger datasets, both within and across avian model systems.Zusammenfassung Vogelnester schützen Elternvögel, Eier oder Jungvögel vor Schwankungen in der Umwelt. Wir haben bei Blaumeisen (Cyanistes caeruleus), die Erst-oder Ersatzgelege produzierten, die Beziehungen zwischen Nesthöhe (einem Maß für Nestgröße) und mehreren Bruterfolgsparametern, die oftmals in Langzeitfeldstudien an Vögeln quantifiziert werden, untersucht. Wir haben für zufällig ausgewählte Weibchen die Kosten der Fortpflanzung experimentell erhöht, indem wir das gesamte Erstgelege sowie Nistmaterial nach etwa fünf Tagen Bebrütung entfernt haben. Dieses Experiment hatte Ersatznester zur Folge. Unsere Erwartung war, dass wir eine positive Korrelation zwischen Nesthöhe und Bruterfolg eher entdecken können, wenn wir die Brutbedingungen für Weibchen experimentell variabler machen. Wir fanden jedoch, dass die Nestgröße nicht signifikant mit irgendeinem der untersuchten Brutparameter (Gelegegröße, Anzahl geschlüpfter und ausgeflogener Jungvögel, Schlupf-und Ausfliegeerfolg, Körpermasse der Küken) zusammenhing, nachdem wir Faktoren, die in Langzeitstudien häufig untersucht werden und bekanntermaßen die Fortpflanzungleistung beeinflussen (Weibchenalter, Jahr, Gelegetyp als Maß für Legedatum), berücksichtigt hatten. Wir schlussfolgern, dass für die Ermittlung der genauen Mechanismen, die Zusammenhänge zwischen Nestmerkmalen und Fortpflanzungleistung verursachen, mehr experimentelle Untersuchungen und grö-ßere Datensätze benötigt werden, sowohl innerhalb als auch zwischen verschiedenen Vogel-Modellsystemen.

Phenological traits often show variation within and among natural populations of annual plants. Nevertheless, the adaptive value of post-anthesis traits is seldom tested. In this study, we estimated the adaptive values of pre- and post-anthesis traits in two stressful environments (water stress and interspecific competition), using the selfing annual species Arabidopsis thaliana. By estimating seed production and by performing laboratory natural selection (LNS), we assessed the strength and nature (directional, disruptive and stabilizing) of selection acting on phenological traits in A. thaliana under the two tested stress conditions, each with four intensities. Both the type of stress and its intensity affected the strength and nature of selection, as did genetic constraints among phenological traits. Under water stress, both experimental approaches demonstrated directional selection for a shorter life cycle, although bolting time imposes a genetic constraint on the length of the interval between bolting and anthesis. Under interspecific competition, results from the two experimental approaches showed discrepancies. Estimation of seed production predicted directional selection toward early pre-anthesis traits and long post-anthesis periods. In contrast, the LNS approach suggested neutrality for all phenological traits. This study opens questions on adaptation in complex natural environment where many selective pressures act simultaneously.

Demographic changes are known to leave footprints on genetic polymorphism. Together with the increased availability of large polymorphism data sets, coalescent-based methods allow inferring the past demography of populations from their present-day patterns of genetic diversity. Here, we analyzed both nuclear (20 noncoding regions) and mitochondrial (HVS-I) resequencing data to infer the demographic history of 66 African and Eurasian human populations presenting contrasting lifestyles (nomadic hunter-gatherers, nomadic herders, and sedentary farmers). This allowed us to investigate the relationship between lifestyle and demography and to address the long-standing debate about the chronology of demographic expansions and the Neolithic transition. In Africa, we inferred expansion events for farmers, but constant population sizes or contraction events for hunter-gatherers. In Eurasia, we inferred higher expansion rates for farmers than herders with HVS-I data, except in Central Asia and Korea. Although isolation and admixture processes could have impacted our demographic inferences, these processes alone seem unlikely to explain the contrasted demographic histories inferred in populations with different lifestyles. The small expansion rates or constant population sizes inferred for herders and hunter-gatherers may thus result from constraints linked to nomadism. However, autosomal data revealed contraction events for two sedentary populations in Eurasia, which may be caused by founder effects. Finally, the inferred expansions likely predated the emergence of agriculture and herding. This suggests that human populations could have started to expand in Paleolithic times, and that strong Paleolithic expansions in some populations may have ultimately favored their shift toward agriculture during the Neolithic.

Studying the current distribution of genetic diversity in humans has important implications for our understanding of the history of our species. We analyzed a set of linked STR and SNP loci from the paternally inherited Y chromosome to infer the past demography of 55 African and Eurasian populations, using both the parametric and nonparametric coalescent-based methods implemented in the BEAST application. We inferred expansion events in most sedentary farmer populations, while we found constant effective population sizes for both nomadic hunter-gatherers and seminomadic herders. Our results differed, on several aspects, from previous results on mtDNA and autosomal markers. First, we found more recent expansion patterns in Eurasia than in Africa. This discrepancy, substantially stronger than the ones found with the other kind of markers, may result from a lower effective population size for men, which might have made male-transmitted markers more sensitive to the out-of-Africa bottleneck. Second, we found expansion signals only for sedentary farmers but not for nomadic herders in Central Asia, while these signals were found for both kind of populations in this area when using mtDNA or autosomal markers. Expansion signals in this area may result from spatial expansion processes and may have been erased for the Y chromosome among the herders because of restricted male gene flow.

Menopause, the permanent cessation of ovulation, occurs in humans well before the end of the expected lifespan, leading to an extensive post-reproductive period which remains a puzzle for evolutionary biologists. All human populations display this particularity; thus, it is difficult to empirically evaluate the conditions for its emergence. In this study, we used artificial neural networks to model the emergence and evolution of allocation decisions related to reproduction in simulated populations. When allocation decisions were allowed to freely evolve, both menopause and extensive post-reproductive life-span emerged under some ecological conditions. This result allowed us to test various hypotheses about the required conditions for the emergence of menopause and extensive post-reproductive life-span. Our findings did not support the Maternal Hypothesis (menopause has evolved to avoid the risk of dying in childbirth, which is higher in older women). In contrast, results supported a shared prediction from the Grandmother Hypothesis and the Embodied Capital Model. Indeed, we found that extensive post-reproductive lifespan allows resource reallocation to increase fertility of the children and survival of the grandchildren. Furthermore, neural capital development and the skill intensiveness of the foraging niche, rather than strength, played a major role in shaping the age profile of somatic and cognitive senescence in our simulated populations. This result supports the Embodied Capital Model rather than the Grand-Mother Hypothesis. Finally, in simulated populations where menopause had already evolved, we found that reduced post-reproductive lifespan lead to reduced children’s fertility and grandchildren’s survival. The results are discussed in the context of the evolutionary emergence of menopause and extensive post-reproductive life-span.

The transition from hunting and gathering to plant and animal domestication was one of the most important cultural and technological revolutions in human history. According to archeologists and paleoanthropologists, this transition triggered major demographic expansions. However, few genetic studies have found traces of Neolithic expansions in the current repartition of genetic polymorphism, pointing rather toward Paleolithic expansions. Here, we used microsatellite autosomal data to investigate the past demographic history of 87 African and Eurasian human populations with contrasted lifestyles (nomadic huntergatherers, semi-nomadic herders and sedentary farmers). Likely due to the combination of a higher mutation rate and the possibility to analyze several loci as independent replicates of the coalescent process, the analysis of microsatellite data allowed us to infer more recent expansions than previous genetic studies, potentially resulting from the Neolithic transition. Despite the variability in their location and environment, we found consistent expansions for all sedentary farmers, while we inferred constant population sizes for all hunter-gatherers and most herders that could result from constraints linked to a nomadic or semi-nomadic lifestyle and/or competition for land between herders and farmers. As an exception, we inferred expansions for Central Asian herders. This might be linked with the arid environment of this area that may have been more favorable to nomadic herders than to sedentary farmers. Alternatively, current Central Asian herders may descent from populations who have first experienced a transition from hunter-gathering to sedentary agropastoralism, and then a second transition to nomadic herding.

An error was made when presenting results of the CARE study by Bianchi et al. The sentence: 'They found a sensitivity of 100% (for all three trisomies) (95% confidence interval (CI): 99.8-100), at a specificity of 99.7 and 99.8% for trisomies 21 and 18, respectively' should have read: 'While detecting all eight cases of the three trisomies, this study found a specificity of 99.7 for trisomy 21 (95% CI: 99.3-99.9) and 99.8 for trisomy 18 (95% CI: 99.6-100).

An interest in producing sounds during play behaviour might be a forerunner for music. Thus, we explored object play behaviour involving sounds in cockatiels (Nymphicus hollandicus). We provided them with several objects producing sounds and recorded sound production, spontaneous warbles and drumming during breeding, pre- and post-breeding. Birds manipulated the objects in a playful way. They manipulated them less during breeding than during pre- and post-breeding, but the proportion of manipulations producing sounds were higher during post-breeding and breeding than during pre-breeding. Males manipulated the objects more frequently and produced more sounds than females. Youngsters manipulated the objects more than adults. One bird repeatedly put a bell on a xylophone; we discuss several possible explanations for the behaviour, including tool use. Only males warbled and drummed, and during breeding only. Our results suggest an enriching effect of the objects on the birds. Many aspects of musicality remain to be studied.