Biology of a weakly social bee, Exoneura (Exoneurella) setosa (Hymenoptera : Apidae) and implications for social evolution in Australian allodapine bees

1998 ◽  
Vol 46 (3) ◽  
pp. 221 ◽  
Author(s):  
Tania Neville ◽  
Michael P. Schwarz ◽  
Simon M. Tierney
Keyword(s):  
Group Size ◽  
Social Evolution ◽  
Sensu Stricto ◽  
Brood Production ◽  
Brood Rearing ◽  
Large Group ◽  
Basal Position ◽  
Social Bee

Australian allodapine bees provide excellent material for comparative approaches to understanding social evolution. The subgenus Exoneurella occupies a cladistically basal position in the Australian Exoneura group and comprises only four species. We describe sociality in one Exoneurella species, E. setosa, and combine this with other data to infer some patterns of social evolution in allodapines. E. setosa rears a first brood solitarily, although staggered brood production and the production of a second brood in some nests leads to a situation where older, recently emerged brood have the ability to help rear their younger siblings and this overlaps with opportunities to lay eggs. This is similar to the situation for two other phylogenetically distal species of Exoneurella, as well as for members of the genus Braunsapis, which is used as an outgroup for Exoneura. When combined with other studies, our results suggest that the opportunity for sib-rearing is a plesiomorphic trait for Australian allodapines and this has been largely lost in a distal subgenus, Exoneura sensu stricto. Instead, multifemale brood-rearing colonies in this latter group mostly comprise individuals of the same generation, and species exhibit large group size, univoltinism and kin cofounding. This suggests that evolution can favour semisociality and quasisociality, even when eusociality has already arisen.

Social Behaviour in an Australian Allodapine Bee Exoneura (Brevineura) xanthoclypeata (Hymenoptera : Apidae)

1997 ◽  
Vol 45 (4) ◽  
pp. 385 ◽  
Author(s):  
Simon M. Tierney ◽  
Michael P. Schwarz ◽  
M. Adams
Keyword(s):  
Social Behaviour ◽  
Social Evolution ◽  
Extended Period ◽  
Sensu Stricto ◽  
Extensive Study ◽  
Egg Laying ◽  
Brood Production ◽  
Brood Rearing ◽  
Reproductive Differentiation ◽  
Two Factors

The allodapine bees are well suited for comparative studies of social evolution because of the wide variation in social behaviour within and between genera. There are three main clades in the endemic Australian genus Exoneura. Two groups (Exoneura sensu stricto and Exoneurella) have received extensive study. In this paper we provide the first detailed study of social behaviour in the third group, Brevineura, based on a heathland population of Exoneura (B.) xanthoclypeata Rayment. This species has two seasonal pulses of egg-laying and brood rearing occurs throughout most of the year, including winter. This extended period of egg-laying and brood development differs from the two other Australian Exoneura subgenera and provides extensive opportunities for eusocial-like sib-rearing. Dissection data indicate that reproductive differentiation among adult nestmates is well developed and dependent on body size, with smaller females being mostly or entirely non-reproductive. Per capita brood production is dramatically higher in multi-female nests than in single-female nests and relatedness between adult nestmates is moderately high (r ≈ 0·5). These two factors suggest that local fitness enhancement may be occurring and our limited sex allocation data suggest female-biased ratios. Because of the opportunities for sib-rearing in this species, local fitness enhancement has the potential to lower selective thresholds for eusociality.

An ecological basis for large group size in Colobus angolensis in the Nyungwe Forest, Rwanda

2001 ◽  
Vol 39 (1) ◽  
pp. 83-92 ◽  
Author(s):  
Cheryl Fimbel ◽  
Amy Vedder ◽  
Ellen Dierenfeld ◽  
Felix Mulindahabi
Keyword(s):  
Group Size ◽  
Large Group ◽  
Colobus Angolensis ◽  
Ecological Basis

scholarly journals The Effects of Group Size and Time on the Formation of Online Communities: Evidence From Reddit

2018 ◽  
Vol 4 (4) ◽  
pp. 205630511881590 ◽  
Author(s):  
Elliot Panek ◽  
Connor Hollenbach ◽  
Jinjie Yang ◽  
Tyler Rhodes
Keyword(s):  
Multilevel Analysis ◽  
Group Size ◽  
Online Communities ◽  
Cohort Effect ◽  
Active Member ◽  
Group Discussions ◽  
Large Group ◽  
Group Member

These studies examine the influence of group size and the passage of time on two characteristics of online communities: dispersion of participation in group discussions and active member turnover from month to month. We used multilevel analysis to examine the dynamics of user contributions to discussions on Reddit, a popular website that hosts large-group discussions, across 30 groups over 6 years. As groups grow in size, participation becomes more highly concentrated among fewer members while turnover decreases. As time passes, participation becomes more widely dispersed while group member turnover increases. An increase in group member turnover appears to be the result of both a maturation effect (as each group ages, turnover increases) as well as a cohort effect (groups formed at a later date have higher turnover than groups formed earlier). We can conclude from these results that as time progresses and groups become larger, they become less community-like, but in different ways.

An Assessment of an electronic feeding system and “dynamic” grouping in loose-housed sows

1986 ◽  
Vol 1986 ◽  
pp. 120-120
Author(s):  
R.J. Lambert ◽  
M. Ellis ◽  
P. Rowlinson
Keyword(s):  
Group Size ◽  
Well Being ◽  
Feeding System ◽  
Group Management ◽  
Large Group

Recently, sow-activated electronic concentrate dispensers allowing dry sows to be group-housed and individually fed have been seriously considered as an alternative to the close confinement of pregnant sows. For the system to be economic, each feeding unit needs to be used to its maximum potential, while at the same time considering the well-being of the animals.Previous work has established that levels of aggression may be minimised within a set group size and the maximum number of sows per feeder may be increased to over 30 by feeding only once per day on this system (Lambert et al., 1985). With groups of this size, the practical aspects of large group management need to be considered.

scholarly journals Group size effects in social evolution

2018 ◽  
Vol 457 ◽  
pp. 211-220 ◽  
Author(s):  
Jorge Peña ◽  
Georg Nöldeke
Keyword(s):  
Group Size ◽  
Size Effects ◽  
Social Evolution

scholarly journals The multinomial index: a robust measure of reproductive skew

2020 ◽  
Vol 287 (1936) ◽  
pp. 20202025
Author(s):  
Cody T. Ross ◽  
Adrian V. Jaeggi ◽  
Monique Borgerhoff Mulder ◽  
Jennifer E. Smith ◽  
Eric Alden Smith ◽  
...  
Keyword(s):  
Group Size ◽  
Social Evolution ◽  
Natural Populations ◽  
R Package ◽  
Reproductive Skew ◽  
Primate Species ◽  
Highly Sensitive ◽  
Highly Nonlinear ◽  
Population Comparisons ◽  
Negative Effect

Inequality or skew in reproductive success (RS) is common across many animal species and is of long-standing interest to the study of social evolution. However, the measurement of inequality in RS in natural populations has been challenging because existing quantitative measures are highly sensitive to variation in group/sample size, mean RS, and age-structure. This makes comparisons across multiple groups and/or species vulnerable to statistical artefacts and hinders empirical and theoretical progress. Here, we present a new measure of reproductive skew, the multinomial index, M , that is unaffected by many of the structural biases affecting existing indices. M is analytically related to Nonacs’ binomial index, B , and comparably accounts for heterogeneity in age across individuals; in addition, M allows for the possibility of diminishing or even highly nonlinear RS returns to age. Unlike B , however, M is not biased by differences in sample/group size. To demonstrate the value of our index for cross-population comparisons, we conduct a reanalysis of male reproductive skew in 31 primate species. We show that a previously reported negative effect of group size on mating skew was an artefact of structural biases in existing skew measures, which inevitably decline with group size; this bias disappears when using M . Applying phylogenetically controlled, mixed-effects models to the same dataset, we identify key similarities and differences in the inferred within- and between-species predictors of reproductive skew across metrics. Finally, we provide an R package, SkewCalc , to estimate M from empirical data.

scholarly journals First- and second-order sociality determine survival and reproduction in cooperative cichlids

2015 ◽  
Vol 282 (1819) ◽  
pp. 20151971 ◽  
Author(s):  
Arne Jungwirth ◽  
Michael Taborsky
Keyword(s):  
Social Organization ◽  
Group Size ◽  
Reproductive Output ◽  
Local Population ◽  
Cichlid Fish ◽  
Evolution Of Cooperation ◽  
Large Group ◽  
Indirect Fitness ◽  
Fitness Benefits ◽  
Different Levels

Cooperative breeders serve as a model to study the evolution of cooperation, where costs and benefits of helping are typically scrutinized at the level of group membership. However, cooperation is often observed in multi-level social organizations involving interactions among individuals at various levels. Here, we argue that a full understanding of the adaptive value of cooperation and the evolution of complex social organization requires identifying the effect of different levels of social organization on direct and indirect fitness components. Our long-term field data show that in the cooperatively breeding, colonial cichlid fish Neolamprologus pulcher , both large group size and high colony density significantly raised group persistence. Neither group size nor density affected survival at the individual level, but they had interactive effects on reproductive output; large group size raised productivity when local population density was low, whereas in contrast, small groups were more productive at high densities. Fitness estimates of individually marked fish revealed indirect fitness benefits associated with staying in large groups. Inclusive fitness, however, was not significantly affected by group size, because the direct fitness component was not increased in larger groups. Together, our findings highlight that the reproductive output of groups may be affected in opposite directions by different levels of sociality, and that complex forms of sociality and costly cooperation may evolve in the absence of large indirect fitness benefits and the influence of kin selection.

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