9,490 research outputs found
Effects of group composition and level of selection in the evolution of cooperation in artificial ants
Since ants and other social insects have long generation time, it is very difficult for biologists to study the origin of complex social organization by guided evolution (a process where the evolution of a trait can be followed during experimental evolution). Here we use colonies of artificial ants implemented as small mobile robots with simple vision and communication abilities to explore these issues. In this paper, we present results concerning the role of relatedness (genetic similarity) and levels of selection (individual and colony-level selection) on the evolution of cooperation and division of labor in simulated ant colonies. In order to ensure thorough statistical analysis, the evolutionary experiments, herein reported, have been carried out using "minimalist" simulations of the collective robotics evolutionary setup. The results show that altruistic behaviors have low probability of emerging in heterogeneous colonies evolving under individual-level selection and that colonies with high genetic relatedness display better performance
Causes and Consequences of Intraspecific Variation in Behavior of the Red Imported Fire Ant
Organisms vary at the individual and population level in many ecologically relevant traits. This study documents and quantifies colony-level variation in ecologically important behaviors of a widespread invasive social insect, demonstrates multitrophic ecological effects of this colony-level variation, and explores genetic factors that may affect and predict behavior at the colony-level.
I quantified significant, persistent regional and colony-level variation in the red imported fire ant (Solenopsis invicta) in behaviors such as extra-nest activity, exploration, and resource discovery speed and recruitment effort. Colony behavior correlated with both colony productivity and colony growth. Using single-lineage colonies, I estimated broad-sense heritability of between 0.45 and 0.5 for the observed colony behaviors.
I created experimental microcosms comprised of fire ant colonies, plants, and insect herbivores. Differences in fire ant colony behavior linked to carbohydrate attraction directly impacted herbivore mortality and indirectly impacted plant damage.
I quantified colony differences colony differences in the expression of the fire ant foraging gene (sifor) as well as colony-level differences in behavior for fire ant colonies collected from across a large area of Texas. Expression of sifor was more than three-fold higher in fire ant foragers than in fire ant workers in the interior of the nest, and colony-level differences in sifor expression of foragers and interior workers correlated with colony behavior. Higher sifor expression in foragers correlated with higher foraging activity, exploratory activity, and recruitment to nectar in fire ant colonies.
Finally, I explored the hypothesis that fire ant foundress groups could maximize inclusive fitness benefits and alter cooperative and competitive behaviors in response to cues indicating higher relatedness of foundresses. I found that group and queen performance was significantly affected by group composition. Groups composed of foundresses that were less likely to be related produced no more workers than queens founding alone, while groups composed of foundresses from the same site produced the most workers of all group types.
The conclusions of this study have widespread implications for many social insects and their ecological interactions. By further exploring these effects at the mechanistic, organismal, and ecological level we will improve our understanding of collective behavior, social evolution, and intraspecific variation
SamACO: variable sampling ant colony optimization algorithm for continuous optimization
An ant colony optimization (ACO) algorithm offers
algorithmic techniques for optimization by simulating the foraging behavior of a group of ants to perform incremental solution
constructions and to realize a pheromone laying-and-following
mechanism. Although ACO is first designed for solving discrete
(combinatorial) optimization problems, the ACO procedure is
also applicable to continuous optimization. This paper presents
a new way of extending ACO to solving continuous optimization
problems by focusing on continuous variable sampling as a key
to transforming ACO from discrete optimization to continuous
optimization. The proposed SamACO algorithm consists of three
major steps, i.e., the generation of candidate variable values for
selection, the ants’ solution construction, and the pheromone
update process. The distinct characteristics of SamACO are the
cooperation of a novel sampling method for discretizing the
continuous search space and an efficient incremental solution
construction method based on the sampled values. The performance
of SamACO is tested using continuous numerical functions
with unimodal and multimodal features. Compared with some
state-of-the-art algorithms, including traditional ant-based algorithms
and representative computational intelligence algorithms
for continuous optimization, the performance of SamACO is seen
competitive and promising
Behavioural response of workers to repeated intergroup encounters in the harvester ant Messor barbarus
This is the author accepted manuscript. The final version is available from Springer via the DOI in this record.The evolution of cooperation in animal societies is often associated with the evolution of hostility
towards members of other groups. It is usually predicted that groups under attack from outsiders
should respond by becoming more cohesive or cooperative. However, the responses of individuals
to real or simulated intergroup encounters vary widely, for reasons that are poorly understood. We
tested how groups of workers of the harvester ant, Messor barbarus, responded to exposure to
members of a different colony versus members of their own colony, and how previous exposure to
an intruder affected the intensity of the within-group response. We found that workers increased in
activity and had more contact with one another immediately following exposure to an ant from a
different colony, but also showed a similar behavioural response to presentations involving an ant
from their own colony. However, exposure to an intruder from a different colony resulted in much
stronger behavioural responses to a second intruder, encountered shortly afterwards. Our results
are consistent with studies of social vertebrates which suggest that exposure to intruders results in
increased social cohesion. Our results also show that exposure to an intruder primes group members
to respond more strongly to future intrusions. Our findings highlight a disconnect between the
assumptions of theoretical models which study the effect of intergroup conflict on social evolution
over many generations, and the short-term behavioural responses that are the usual focus of studies
of intergroup conflict in insects and vertebrates.Natural Environment Research Council (NERC
The foundress’s dilemma: group selection for cooperation among queens of the harvester ant, Pogonomyrmex californicus
abstract: The evolution of cooperation is a fundamental problem in biology, especially for non-relatives, where indirect fitness benefits cannot counter within-group inequalities. Multilevel selection models show how cooperation can evolve if it generates a group-level advantage, even when cooperators are disadvantaged within their group. This allows the possibility of group selection, but few examples have been described in nature. Here we show that group selection can explain the evolution of cooperative nest founding in the harvester ant Pogonomyrmex californicus. Through most of this species’ range, colonies are founded by single queens, but in some populations nests are instead founded by cooperative groups of unrelated queens. In mixed groups of cooperative and single-founding queens, we found that aggressive individuals had a survival advantage within their nest, but foundress groups with such non-cooperators died out more often than those with only cooperative members. An agent-based model shows that the between-group advantage of the cooperative phenotype drives it to fixation, despite its within-group disadvantage, but only when population density is high enough to make between-group competition intense. Field data show higher nest density in a population where cooperative founding is common, consistent with greater density driving the evolution of cooperative foundation through group selection.The final version of this article, as published in Scientific Reports, can be viewed online at: https://www.nature.com/articles/srep2982
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