Forb stability, dwarf shrub stability and species asynchrony regulate ecosystem stability along an experimental precipitation gradient in a semi-arid desert grassland.

Precipitation pattern changes may affect plant biodiversity, which could impact ecosystem stability. However, the effects of changes in precipitation regime on ecosystem stability and their potential mechanisms are still unclear. We conducted a 3-year field manipulation experiment with five precipitation treatments (-40%, -20%, 0% (CK), +20% and +40% of ambient growing season precipitation) in a semi-arid desert grassland to examine the effects of precipitation alterations on functional group stability, species asynchrony, and diversity, and the underlying mchanisms of ecosystem stability using structural equation modelling. Alterations in precipitation had different effects on community biomass and functional group biomass. Moreover, ecosystem stability was mainly driven by forb stability (path coefficient = 0.79). Changes in precipitation had significant effects on soil dissolved inorganic N (P < 0.01) further affecting ecosystem stability through species asynchrony (path coefficient = 0.25). Dwarf shrubs had a stabilizing effect on ecosystem stability (path coefficient = 0.32), mainly via deep roots. Ecosystem stability tended to be lower in the -40% (4.72) and +40% (2.74) precipitation treatments. The common reduction in species asynchrony and stability of forb and dwarf shrub functional groups resulted in lower ecosystem stability under the -40% treatment. The lower stability under the +40% treatment might be ascribed to unimproved dwarf shrub stability. Higher dwarf shrub and forb stability contributed to higher ecosystem stability under normal precipitation changes (±20% treatments) and CK. Species diversity was not a crucial driver of ecosystem stability. Our results indicate that precipitation alteration can regulate ecosystem stability via functional group stability (e.g. forb stability, dwarf shrub stability) and species asynchrony in a semiarid desert grassland.

Social stability via management of natal males in captive rhesus macaques (Macaca mulatta).

Keystone individuals are expected to disproportionately contribute to group stability. For instance, rhesus macaques (Macaca mulatta) who police conflict contribute towards stability. Not all individuals' motivations align with mechanisms of group stability. In wild systems, males typically disperse at maturity and attempt to ascend via contest competition. In a captive system, dispersal is not naturally enabled - individuals attempt to ascend in their natal groups, which can be enabled by matrilineal kin potentially destabilizing group dynamics. We relocated select high-ranking natal males from five groups and assessed group stability before and after. We quantified hierarchical metrics at the individual and group level. After removal, we found significantly higher aggression against the established hierarchy (reversals), indicative of opportunistic attempts to change the hierarchy. Mixed-sex social signaling became more hierarchical, but the strength of this effect varied. Stable structure was not uniformly reached across the groups and alpha males did not all benefit. Indiscriminate natal male removal is an unreliable solution to group instability. Careful assessment of how natal males are embedded within their group is necessary to balance individual and group welfare.

Comparative approaches in social network ecology.

Social systems vary enormously across the animal kingdom, with important implications for ecological and evolutionary processes such as infectious disease dynamics, anti-predator defence, and the evolution of cooperation. Comparing social network structures between species offers a promising route to help disentangle the ecological and evolutionary processes that shape this diversity. Comparative analyses of networks like these are challenging and have been used relatively little in ecology, but are becoming increasingly feasible as the number of empirical datasets expands. Here, we provide an overview of multispecies comparative social network studies in ecology and evolution. We identify a range of advancements that these studies have made and key challenges that they face, and we use these to guide methodological and empirical suggestions for future research. Overall, we hope to motivate wider publication and analysis of open social network datasets in animal ecology.

Social Network Changes in Cotton-Top Tamarins (Saguinus oedipus) after the Birth of New Infants.

Cotton-top tamarins (Saguinus oedipus) are characterized by a system of cooperative breeding where helpers, in addition to the reproductive pair, contribute to infant care. Grooming interactions between individuals play an important role in establishing social relationships, creating an interconnected social network in the group. We used social network analysis to investigate the social structure of two groups of cotton-top tamarins with different sizes and compositions and study whether they remain stable after the birth of new infants. We also investigated the possible correlation between the time spent carrying infants and an increase in the grooming centrality. We found that group A (n = 13) had a stable grooming network that showed consistent stability after the birth, although group B (n = 8 and no adult helpers) changed its grooming network and showed a lower density after the birth. Infant carrying was not correlated with increased grooming centrality after the birth. These findings highlight the usefulness of social network analysis in the study of group structure in cooperatively breeding primates and suggest that the birth of offspring has a greater impact on the stability of groups without adult helpers.

Effects of plant diversity on semiarid grassland stability depends on functional group composition and dynamics under N and P addition.

Exogenous fertilization could efficiently improve grassland productivity and promote grassland restoration. Increasing fertilization may profoundly affect community stability, whereas the underlying compensatory dynamics among functional groups in regulating grassland stability remain unclear. Three different grasslands, annuals forb (AF) community, perennial grass (PG) community and perennial forb (PF) community, on semiarid Loess Plateau were selected. We designed a 3-year split-plot experiment (main-plot: 0, 25, 50, and 100 kg N ha-1 yr-1; subplot: 0, 20, 40 and 80 kg P2O5 ha-1 yr-1) to explore how N and P addition affects community stability and its relationship with species richness, species asynchrony and functional group stability. Temporal stability differed largely between functional groups under N and P addition, perennial forbs or grasses had higher stability than perennial legumes or annuals and biennials. Decreased stability of PG and PF communities was primarily due to reduced species asynchrony under N addition alone, while it attributed to increased dominance of perennial legumes after P addition alone. 50 and 100 kg N ha-1 yr-1 combined with P addition significantly increased dominance of annuals and biennials, but decreased stability of annuals and biennials, which caused significant declines in stability of the three communities. Significant species richness decline induced by N and P addition only occurred in AF community, which suppressed AF community stability through reducing species asynchrony. AF community stability was regulated by additively negative effect of diversity decline and decreased annuals and biennials stability. Whereas, in PG and PF communities, nutrient-induced changes of functional groups stability were the main driver of community stability rather than diversity. Our study highlights the role of functional group composition and dynamics in regulating the effects of diversity on community stability and rational N and P combined addition was essential for conserving stability of different grasslands on semiarid Loess Plateau.

Behavioral and physiological responses to instability in group membership in wild male woolly monkeys (Lagothrix lagotricha poeppigii).

In group-living species, integrating into a new social group after dispersal is an important life history milestone associated with physical and social challenges. Generally, this process seems to be accompanied by heightened glucocorticoid (GC) concentrations; however, most studies of physiological responses to group transfer have been conducted on species with despotic social relationships, where integrating individuals are often targets of frequent aggression. Here we present data on fecal glucocorticoid (fGC) concentrations during periods of unstable group membership for male woolly monkeys (Lagothrix lagotricha poeppigii), a species with extremely low rates of male-male aggression and generally tolerant male-male associations. We collected data on males in four study groups at the Tiputini Biodiversity Station, Ecuador, and observed three attempted transfer events, involving a total of four adult males, in one study group. We observed only three instances of overt aggression (chases) between males across the entire study period, though male display behaviors were more frequent. We tested whether rates of displays were higher during periods of unstable group membership using a generalized linear mixed model (LMM). We also examined whether male status, group stability, and the occurrence of intergroup encounters affected fGC concentrations using LMMs. Contrary to our predictions, rates of display behaviors were not higher during periods of unstable group membership. However, both transient/integrating males and those who were already group members showed elevated fGC concentrations during these unstable periods. Our results suggest that even in species with tolerant male-male relationships, the integration of unfamiliar individuals can provoke an increase in GCs.

Intermittent breeding is associated with breeding group turnover in a cooperatively breeding bird.

Intermittent breeding, in which an adult skips a breeding opportunity, can represent a non-adaptive constraint or an adaptive response to the tradeoff between current and future reproduction. In group-living animals, the social group may also affect the frequency of reproduction, but this possibility has received little attention. Here we use an 11-year data set to investigate intermittent breeding in the greater ani (Crotophaga major), a tropical bird that nests in stable breeding groups containing several unrelated co-breeding females. Population-wide, an average of 62% of females laid eggs in a given year (range 35-84%), and the average female failed to lay eggs once every 3.2 years. We found little support for the hypothesis that intermittent breeding reflects a tradeoff between current and future reproduction: breeding in year t did not affect a female's likelihood of breeding in year t + 1, and clutch size in year t did not affect clutch size in year t + 1. Increases in clutch size were associated with decreases in egg mass for eggs laid at the end of that clutch, but this did not affect subsequent nesting attempts. However, reproductive skipping was associated with changes in group membership. Females whose groups changed in composition after year t were significantly less likely to breed in year t + 1 than females whose groups remained stable. These results indicate that breeding group stability influences the frequency of reproduction, suggesting that transitions between groups may be costly to females and their mates.

Stable social relationships between unrelated females increase individual fitness in a cooperative bird.

Social animals often form long-lasting relationships with fellow group members, usually with close kin. In primates, strong social bonds have been associated with increased longevity, offspring survival and reproductive success. However, little is known about the fitness effects of social bonds between non-kin, especially outside of mammals. In this study, we use long-term field research on a cooperatively breeding bird, the greater ani (Crotophaga major), to ask whether adult females benefit by remaining in long-term associations with unrelated, co-breeding females. We find that females that have previously nested together synchronize their reproduction more rapidly than those nesting with unfamiliar partners, which leads to lower competition and higher fledging success. Importantly, although previous experience with a co-breeding female influenced reproductive synchrony, the degree of reproductive synchrony did not influence whether co-breeding females remained together in subsequent years, ruling out the alternate hypothesis that highly synchronized females are simply more likely to remain together. These results indicate that switching groups is costly to females, and that social familiarity improves reproductive coordination. Stable social relationships therefore have significant fitness consequences for cooperatively nesting female birds, suggesting that direct benefits alone may favour the evolution of associations between non-relatives and contribute to long-term group stability.

The Categorical Stability of Gambling Motives Among Community-Recruited Gamblers: A Longitudinal Assessment.

Over the past decade, several motivational models have been proposed to explain the role of motives in gambling disorder. In the model captured by the four-factor Gambling Motives Questionnaire Financial (GMQ-F), gamblers are described as being primarily motivated to gamble for 'coping', 'enhancement', 'social', and 'financial' reasons. Although this model has received significant empirical support; to date, research assessing the role of motives in gambling disorder has been primarily cross-sectional in nature. Thus, the extent to which gambling motives remain stable over time has yet to be explored. In the current study, the stability versus fluidity of self-assessed gambling motives was investigated using the Quinte Longitudinal Study, a longitudinal dataset of gambling behaviour collected over 5 years. Gambling motives of 2795 gamblers were examined over all five annual assessments. The total proportion of gamblers who stayed in the same primary motive category across each of the 5 consecutive assessments was 22%, indicating substantial fluidity in category membership. Substantial movement between categories was seen for each GMQ-F group, as well as an additional group of non-classified motives. Logistic regression analyses suggest that greater resistance to gambling fallacies significantly predicted stability between the baseline assessment and a follow-up 1 year later, but gambling severity did not. Potential limitations in the study design and opportunities for future research are discussed.

Long-term-stability of relationship structure in family groups of common marmosets, and its link to proactive prosociality.

Cooperatively breeding, group-living common marmosets show differentiated relationships, where more strongly bonded dyads within a group engage more in affiliative interactions than less strongly bonded ones. Intriguingly, recent results suggest that strong bonds do not only occur between breeding partners but between individuals from any sex or status, and that strong-bond partners exhibit correlated oxytocin fluctuations (dyadic oxytocin synchrony, OTS) over a period of six weeks. To date, it is unclear whether such relationships are stable over time and whether they are also reflected in higher partner-specific proactive prosociality. To assess the long-term stability of the relationship structure of common marmoset family groups, we investigated whether hormonal and behavioral markers of group structure (dyadic OTS, dyadic affiliation, and individual group integration) in common marmoset families remained stable over a period of six months. We collected baseline urinary OT and social behavior of 36 dyads from three family groups in a non-reproductive period (period A), and again six months later, around the birth of new infants (period B). Patterns of dyadic OTS, dyadic affiliation, and individual group integration were consistent between the two study periods. Oxytocin data from a fourth group (10 dyads), collected in two non-reproductive periods separated by a period of more than five years, could replicate this finding. Furthermore, OTS was also correlated with proactive prosociality that was assessed experimentally for 38 dyads during an earlier study. These results suggest that differentiated relationships are stable over time, even between group members other than the breeding pair, and that more strongly bonded partners also show higher levels of proactive prosociality. Future studies are necessary to identify whether these relationships have an adaptive function, perhaps with regard to positive consequences on cooperativeness.