Non-random host tree infestation by the Neotropical liana Marcgravia longifolia.

The question whether or not tropical lianas infest host trees randomly or they exert host selection has implications for the structure and dynamics of tropical rainforests, particularly if colonization by lianas impacts host fitness. In this study, we present evidence that the Neotropical liana Marcgravia longifolia (Marcgraviaceae) infests host trees non-randomly. We identified host trees to species or genus level for 87 of the 100 M. longifolia individuals found in the study area of the Estación Biológica Quebrada Blanco (EBQB) in north-eastern Peruvian Amazonia. Data on host availability were taken from two 1-ha plots sampled at EBQB as part of a large-scale tree inventory in western Amazonia. Of the total of 88 tree genera with two or more individuals present in the inventory, 18 were represented amongst hosts. Host genera with a probability of colonization higher than expected by chance were Eschweilera (Lecythidaceae), Pouteria (Sapotaceae), Brosimum (Moraceae), and Hymenaea (Fabaceae). These findings suggest that M. longifolia exerts some level of host selectivity, but the mechanisms for this are completely unknown. Given the large number of animal species (41 bird species, three primate species) that are dispersing the seeds of M. longifolia and that have diverse ecological strategies, directed seed dispersal is unlikely to account for the observed patterns of host infestation.

Social interactions and activity patterns of old Barbary macaques: Further insights into the foundations of social selectivity.

Human aging is accompanied by a decrease in social activity and a narrowing in social networks. Studies in nonhuman primates may provide valuable comparative insights in which way aging impacts social life, in the absence of cultural conventions and an awareness of a limited lifetime. For female Barbary macaques at "La Forêt des Singes" in Rocamadour, France, we previously reported an age-associated decrease in active grooming time and network size. Here, we aimed to extend these findings by investigating in which way physical decline, spatial proximity, and aggression vary with age in female Barbary macaques. We analyzed >1,200 hr of focal observations for 46 females aged 5-29 years. As expected, older females engaged less frequently in challenging locomotor activity, such as climbing or running, than younger ones. The previously reported decrease in grooming time was not due to shorter grooming bout duration. Instead, active grooming bouts lasted even longer, which discounts the idea that manual fatigue explains the shift in grooming pattern. We found that older females tended to be spatially reclusive and that they were less frequently the targets of aggression. Although older females showed aggressive behaviors at similar rates as younger females, the proportion of low-level aggression (i.e., threats) increased with age. We suggest that these threats are not simply a signal of dominance, but also function to deter approaches by others. Overall, these findings are in line with the idea that older females aim to avoid potentially negative interactions, specifically if these are costly. In sum, these findings support the idea that shifts in female Barbary macaques' grooming activity, do not simply result from physical deterioration, but are instead due to a higher selectivity in the choice of social partners.

Associated motivational salience impacts early sensory processing of human faces.

Facial expressions of emotion have an undeniable processing advantage over neutral faces, discernible both at behavioral level and in emotion-related modulations of several event-related potentials (ERPs). Recently it was proposed that also inherently neutral stimuli might gain salience through associative learning mechanisms. The present study investigated whether acquired motivational salience leads to processing advantages similar to biologically determined origins of inherent emotional salience by applying an associative learning paradigm to human face processing. Participants (N=24) were trained to categorize neutral faces to salience categories by receiving different monetary outcomes. ERPs were recorded in a subsequent test phase consisting of gender decisions on previously associated faces, as well as on familiarized and novel faces expressing happy, angry or no emotion. Previously reward-associated faces boosted the P1 component, indicating that acquired reward-associations modulate early sensory processing in extrastriate visual cortex. However, ERP modulations to emotional - primarily angry - expressions expanded to subsequent processing stages, as reflected in well-established emotion-related ERPs. The present study offers new evidence that motivational salience associated to inherently neutral stimuli can sharpen sensory encoding but does not obligatorily lead to preferential processing at later stages.

Estimation of baboon daily travel distances by means of point sampling - the magnitude of underestimation.

Daily travel distance (DTD), the distance an animal moves over the course of the day, is an important metric in movement ecology. It provides data with which to test hypotheses related to energetics and behaviour, e.g. impact of group size or food distribution on DTDs. The automated tracking of movements by applying GPS technology has become widely available and easy to implement. However, due to battery duration constraints, it is necessary to select a tracking-time resolution, which inevitably introduces an underestimation of the true underlying path distance. Here we give a quantification of this inherent systematic underestimation of DTDs for a terrestrial primate, the Guinea baboon. We show that sampling protocols with interval lengths from 1 to 120 min underestimate DTDs on average by 7 to 35 %. For longer time intervals (i.e. 60, 90, 120 min), the relative increase of deviation from the "true" trajectory is less pronounced than for shorter intervals. Our study provides first hints on the magnitude of error, which can be applied as a corrective when estimating absolute DTDs in calculations on travelling costs in terrestrial primates.

Structured fusion lasso penalized multi-state models.

Multi-state models generalize survival or duration time analysis to the estimation of transition-specific hazard rate functions for multiple transitions. When each of the transition-specific risk functions is parametrized with several distinct covariate effect coefficients, this leads to a model of potentially high dimension. To decrease the parameter space dimensionality and to work out a clear image of the underlying multi-state model structure, one can either aim at setting some coefficients to zero or to make coefficients for the same covariate but two different transitions equal. The first issue can be approached by penalizing the absolute values of the covariate coefficients as in lasso regularization. If, instead, absolute differences between coefficients of the same covariate on different transitions are penalized, this leads to sparse competing risk relations within a multi-state model, that is, equality of covariate effect coefficients. In this paper, a new estimation approach providing sparse multi-state modelling by the aforementioned principles is established, based on the estimation of multi-state models and a simultaneous penalization of the L1 -norm of covariate coefficients and their differences in a structured way. The new multi-state modelling approach is illustrated on peritoneal dialysis study data and implemented in the R package penMSM. Copyright © 2016 John Wiley & Sons, Ltd.

Motivational Shifts in Aging Monkeys and the Origins of Social Selectivity.

As humans age, they become more selective regarding their personal goals [1] and social partners [2]. Whereas the selectivity in goals has been attributed to losses in resources (e.g., physical strength) [3], the increasing focus on emotionally meaningful partners is, according to socioemotional selectivity theory, driven by the awareness of one's decreasing future lifetime [2]. Similar to humans, aging monkeys show physical losses [4] and reductions in social activity [2, 5-7]. To disentangle a general resource loss and the awareness of decreasing time, we combined field experiments with behavioral observations in a large age-heterogeneous population of Barbary macaques (Macaca sylvanus) at La Forêt des Singes. Novel object tests revealed a loss of interest in the nonsocial environment in early adulthood, which was modulated by the availability of a food reward. Experiments using vocal and visual representations of social partners indicated that monkeys maintained an interest in social stimuli and a preferential interest in friends and socially important individuals into old age. Old females engaged in fewer social interactions, although other group members continued to invest in relationships with them. Consequently, reductions in sociality were not due to a decrease in social interest. In conclusion, some of the motivational shifts observed in aging humans, particularly the increasing focus on social over nonsocial stimuli, may occur in the absence of a limited time perspective and are most likely deeply rooted in primate evolution. Our findings highlight the value of nonhuman primates as valuable models for understanding human aging [8, 9].

Do monkeys compare themselves to others?

Social comparisons are a fundamental characteristic of human behaviour, yet relatively little is known about their evolutionary foundations. Adapting the co-acting paradigm from human research (Seta in J Pers Soc Psychol 42:281-291, 1982. doi: 10.1037//0022-3514.42.2.281), we examined how the performance of a partner influenced subjects' performance in long-tailed macaques (Macaca fascicularis). Using parallel testing in touch screen setups in which subjects had to discriminate familiar and novel photographs of men and women, we investigated whether accuracy and reaction time were influenced by partner performance and relationship quality (affiliate vs. non-affiliate). Auditory feedback about the alleged performance of the co-actor was provided via playback; partner performance was either moderately or extremely better or worse than subject performance. We predicted that subjects would assimilate to moderately different comparison standards as well as to affiliates and contrast away from extreme standards and non-affiliates. Subjects instantly generalized to novel pictures. While accuracy was not affected by any of the factors, long reaction times occurred more frequently when subjects were tested with a non-affiliate who was performing worse, compared to one who was doing better than them (80% quantile worse: 5.1, better: 4.3 s). For affiliate co-actors, there was no marked effect (worse: 4.4, better: 4.6 s). In a control condition with no auditory feedback, subjects performed somewhat better in the presence of affiliates (M = 77.8% correct) compared to non-affiliates (M = 71.1%), while reaction time was not affected. Apparently, subjects were sensitive to partner identity and performance, yet variation in motivation rather than assimilation and contrast effects may account for the observed effects.