Reproductive specialization in multiple-queen colonies of the ant Formica exsecta

In polygynous (multiple queens per nest) colonies of socialinsects, queens can increase their reproductive share by layingmore eggs or by increasing the proportion of eggs that developinto reproductive individuals instead of workers. We used polymorphicmicrosatellite loci to determine the genetically effective contributionof queens to the production of gynes (new queens), males, and2 different cohorts of workers in a polygynous population ofthe ant Formica exsecta. For this purpose, we developed a newmethod that can be used for diploid and haplodiploid organismsto quantify the degree of reproductive specialization amongbreeders in societies where there are too many breeders to ascertainparentage. Using this method, we found a high degree of reproductivespecialization among nest-mate queens in both female- and male-producingcolonies (sex ratio is bimodally distributed in the study population).For example, a high effective proportion of queens (25% and79%, respectively) were specialized in the production of malesin female- and male-producing colonies. Our analyses furtherrevealed that in female-producing colonies, significantly fewerqueens contributed to gyne production than to worker production.Finally, we found significant changes in the identity of queenscontributing to different cohorts of workers. Altogether, thesedata demonstrate that colonies of F. exsecta, and probably thoseof many other highly polygynous social insect species, are composedof reproductive individuals differing in their investment togynes, males, and workers. These findings demonstrate a newaspect of the highly dynamic social organization of complexanimal societies.     

Relationship of queen number and queen relatedness in multiple-queen colonies of the fire ant Solenopsis invicta

1. The relationship between the number of queens per nest and their relatedness was examined in the polygyne (multiple queens per nest) social form of the fire ant Solenopsis invicta .
2. No significant relationship between these two variables was found. Moreover, the overall average relatedness among nestmate queens was not significantly different from zero.
3. These findings indicate that polygyne nests of S. invicta do not represent closed societies. Furthermore, they are consistent with continual acceptance of non-nestmate queens throughout a colony's lifetime. This strategy differs from the expectation of kin selection theory that only related queens should be accepted as new reproductives within polygyne colonies.
4. The postulated acceptance of non-nestmate queens is associated with a decrease in the number of parasites, predators and diseases and a concomitant increase in the density of nests in introduced populations, suggesting that the permissive environment experienced by introduced fire ants may have decreased the relative importance of kinship as a stabilizing factor in the evolution of polygyny.     

A comparison of the colony-founding potential of queens from single- and multiple-queen colonies of the fire antSolenopsis invicta

Newly mated queens from the polygyne (multiple-queen) form of S. invicta show a weight polymorphism that correlates with their genotype at the protein locus Gp-9. Although this variation in weight might be expected to translate into variation in the ability of queens to initiate new colonies using stored energy reserves, a systematic examination of the colony-founding ability of newly mated polygyne-derived queens of different weights has never been reported. Here I compare the ability of monogyne-derived queens (Gp-9^BB M), heavy polygyne-derived queens (Gp-9^BB P), and light polygyne-derived queens (Gp-9^Bb P) to initiate their own colonies using only stored energy reserves. Most measurements of the ants' abilities yielded the following scale of competency:Gp-9^BB M>Gp-9^BB P>Gp-9^Bb P. Surprisingly, most mated polygyne-derived queens of even the lighter genotype were capable of rearing considerable numbers of workers in isolation. This ability may be enhanced substantially in the field if such queens cooperate in initiating new nests (pleometrosis). These results are concordant with the growing body of work that implicates a simply inherited genetic polymorphism for the control of a complex social trait in this ant, and they indicate that the modes of reproduction in polygyne fire ants may show considerable diversity.Copyright 2002 The Association for the Study of Animal Behaviour. Published by Elsevier Science Ltd. All rights reserved .     

Reproductive strategy and the life cycle in graptoloid colonies

Urbanek, A. 1990 10 15: Reproductive strategy and the life cycle in graptoloid colonies. Lethaia , Vol. 23, pp. 333–340. Oslo. ISSN 0024–1164.
Graptoloid colonies were clones composed in all probability of hermaphroditic zooids. Their breeding system approaching that of amphicarpic plants, namely distant out crossing combined with selfing, was exceptionally flexible. Moreover, the balanced coexistence of these extreme means of reproduction may be visualized as an evolutionarily stable strategy (ESS). The evolutionary consequences of such a breeding system might have accounted for the overall high rates of graptoloid evolution as well as for the rapid transformations in large populations. Sexual reproduction of graptoloid colonies was complemented by a multiplication through occasional fragmentation of colonies and subsequent regeneration from the fragments. Fragmentation of colonies played an important role in the survival of graptoloid colonies during catastrophic events such as hurricanes and later in recruitment. Fragmentation followed by regeneration, and only later by sexual reproduction of regenerated fragments, constituted the so-called great cycle (GC), whereas the regular course of events initiated by sexual reproduction in an undisturbed (complete) colony resulted in normal colony formation (astogeny) and is termed the small cycle (SC). Thus the adaptive significance of the sexual process in the life cycle is in the restoration of the perfect' pattern of the complete colony, which offered the best hydrodynamic properties and highest fitness. ▭ Graptolithina, Graptoloidea, breeding sysfem, reproductive strategy, fragmentation, life cycle .     

Social structure of perennial Vespula squamosa wasp colonies

Many social species show variation in their social structure in response to different environmental conditions. For example, colonies of the yellowjacket wasp Vespula squamosa are typically headed by a single reproductive queen and survive for only a single season. However, in warmer climates, V. squamosa colonies sometimes persist for multiple years and can grow to extremely large size. We used genetic markers to understand patterns of reproduction and recruitment within these perennial colonies. We genotyped V. squamosa workers, pre‐reproductive queens, and males from perennial colonies in the southeastern United States at 10 polymorphic microsatellite loci and one mitochondrial DNA locus. We found that V. squamosa from perennial nests were produced by multiple reproductives, in contrast to typical annual colonies. Relatedness of nestmates from perennial colonies was significantly lower than relatedness of nestmates from annual colonies. Our analyses of mitochondrial DNA indicated that most V. squamosa perennial colonies represented semiclosed systems whereby all individuals belonged to a single matriline despite the presence of multiple reproductive females. However, new queens recruited into perennial colonies apparently mated with non‐nestmate males. Notably, perennial and annual colonies did not show significant genetic differences, supporting the hypothesis that perennial colony formation represents an instance of social plasticity. Overall, our results indicate that perennial V. squamosa colonies show substantial changes to their social biology compared to typical annual colonies and demonstrate variation in social behaviors in highly social species.     

Towards a solution of the plankton paradox: the importance of physiology and life history

Phytoplankton communities reveal an astonishing biodiversity, whereas classical competition theory seems to suggest that only a few competing species can survive. Recently we suggested a new solution to this plankton paradox. In theory, at least, competition between multiple species can generate complex dynamics that can support a large number of species. How likely is it then, in reality, that competitive chaos indeed promotes biodiversity? To obtain some insight, we simulated multispecies competition according to five different physiological scenarios. For random species parameters, biodiversity was generally low. Assuming plausible physiological trade‐offs, the simulations revealed switches back and forth between equilibrium and nonequilibrium dynamics, and a higher biodiversity. An extremely high biodiversity, with sometimes more than 100 species on three resources, was observed in simulations that assumed a cyclic relation between competitive abilities and resource contents. We conclude that physiological and life‐history patterns have a major impact on the likelihood of nonequilibrium dynamics and on the biodiversity of plankton communities.     

Social prophylaxis: group interaction promotes collective immunity in ant colonies

Life in a social group increases the risk of disease transmission. To counteract this threat, social insects have evolved manifold antiparasite defenses, ranging from social exclusion of infected group members to intensive care. It is generally assumed that individuals performing hygienic behaviors risk infecting themselves, suggesting a high direct cost of helping. Our work instead indicates the opposite for garden ants. Social contact with individual workers, which were experimentally exposed to a fungal parasite, provided a clear survival benefit to nontreated, naive group members upon later challenge with the same parasite. This first demonstration of contact immunity in Social Hymenoptera and complementary results from other animal groups and plants suggest its general importance in both antiparasite and antiherbivore defense. In addition to this physiological prophylaxis of adult ants, infection of the brood was prevented in our experiment by behavioral changes of treated and naive workers. Parasite-treated ants stayed away from the brood chamber, whereas their naive nestmates increased brood-care activities. Our findings reveal a direct benefit for individuals to perform hygienic behaviors toward others, and this might explain the widely observed maintenance of social cohesion under parasite attack in insect societies.     

Behavioural traits of colony founders affect the life history of their colonies

Social arthropods are a major feature in terrestrial ecosystems, and understanding the factors leading to their success is of broad interest. Although many studies have attempted to link colonies' phenotypic composition with their productivity, no study has linked phenotypic composition with the number of offspring colonies formed in the field. I tested whether the behavioural composition of newly founded colonies predicted colony life history patterns in the social spider Anelosimus studiosus. Individual A. studiosus exhibit either an 'aggressive' or 'docile' behavioural type (BT) and BT composition varies among colonies. I constructed artificial colonies of known BT composition and monitored their performance under two conditions: (1) foreign heterospecific spiders present and (2) foreign spiders removed. When heterospecifics were present, colonies founded by docile individuals were invaded by heterospecific spiders more quickly, grew more rapidly in size, produced more offspring colonies per year, but suffered reduced longevity. The life history trade-offs (reproduction, longevity) experienced by colonies resemble those experienced by individuals.     

Culex tritaeniorhynchus: Failure to detect heterosis in the life table characteristics of outcrossed laboratory colonies

Intra and interstrain crosses were made between unselected and inbred adults of the Balloki and Peshawar, Pakistan, laboratory colonies of C. tritaeniorhynchus and life tables were constructed for their progeny. No overall heterosis effects were detected. Inbreeding severely reduced fertility and fecundity and lowered the innate capacity for increase. Interstrain crosses among inbred adults restored some vigor, but all life table estimates relating to fecundity were significantly less than crosses among the unselected adults. Thus, outcrosses among laboratory-adapted colonies did not appear to impart marked heterosis and would probably not enhance the vigor of males used for genetic control.

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Zusammenfassung Intra- und Interstammkreuzungen wurden zwischen unselektionierten und ingezüchteten Insekten der Balloki- und Peshawar-Laboratoriumskolonien von C. tritaeniorhynchus durchgeführt und es wurden Life Tables für ihre Nachkommenschaft erstellt. Dabei konnten keine allgemeinen Heterosis-effekte festgestellt werden. Inzucht verminderte die Fertilität und Fekundität stark und reduzierte die genetische Vermehrungsfähigkeit. Interstammkreuzungen zwischen Inzuchtinsekten brachte etwas Vigor zurück, aber alle Life Table-Schätzungen im Hinblick auf Fekundität waren gesichert tiefer als bei Kreuzungen zwischen nicht selektionierten Insekten. Demnach scheinen Kreuzungen zwischen verschiedenen dem Laboratorium angepassten Kolonien keine ausgeprägte Heterosis zu bringen. Sie würden wahrscheinlich die Qualität von Männchen und Weibchen, die für die genetische Bekämpfung verwendet werden, nicht verbessern.

     

蚂蚁的社会生活

蚂蚁全都属于全社会性昆虫,蚂蚁在自然界的地位和作用十分重要,优势极为明显。蚂蚁社会具有明显的等级分化和个体分工。简要介绍了军蚁、切叶蚁和食蜜露蚂蚁的觅食行为和社会生活。     

Queen recruitment in a multiple-queen population of the fire ant Solenopsis invicta

We assessed patterns of new queen recruitment in a polygyne(multiple queens per nest) population of the fire ant Solenopsisinvicta in its introduced range. Newly recruited queens wereidentified using four physiological markers, and genotypic datafrom nuclear and mitochondrial markers were used to estimaterelatedness of new nest mate queens to each other and to theolder nest mate queens. In total, 1.7% of the queens collectedin late spring and early summer were deemed to be new recruits.The relatedness of these queens to each other and to the olderqueens within nests was not significantly different from zero,suggesting that newly recruited queens represent a random sampleof potential reproductive queens in the population. Moreover,the number of new queens recruited within nests was not correlatedwith the number of older queens present and did not differ significantlyfrom a Poisson distribution. Thus, queen recruitment in this populationof S. invicta appears to occur at random with respect to thenumber of older queens present within nests.     

Social transfer of pathogenic fungus promotes active immunisation in ant colonies

Due to the omnipresent risk of epidemics, insect societies have evolved sophisticated disease defences at the individual and colony level. An intriguing yet little understood phenomenon is that social contact to pathogen-exposed individuals reduces susceptibility of previously naive nestmates to this pathogen. We tested whether such social immunisation in Lasius ants against the entomopathogenic fungus Metarhizium anisopliae is based on active upregulation of the immune system of nestmates following contact to an infectious individual or passive protection via transfer of immune effectors among group members--that is, active versus passive immunisation. We found no evidence for involvement of passive immunisation via transfer of antimicrobials among colony members. Instead, intensive allogrooming behaviour between naive and pathogen-exposed ants before fungal conidia firmly attached to their cuticle suggested passage of the pathogen from the exposed individuals to their nestmates. By tracing fluorescence-labelled conidia we indeed detected frequent pathogen transfer to the nestmates, where they caused low-level infections as revealed by growth of small numbers of fungal colony forming units from their dissected body content. These infections rarely led to death, but instead promoted an enhanced ability to inhibit fungal growth and an active upregulation of immune genes involved in antifungal defences (defensin and prophenoloxidase, PPO). Contrarily, there was no upregulation of the gene cathepsin L, which is associated with antibacterial and antiviral defences, and we found no increased antibacterial activity of nestmates of fungus-exposed ants. This indicates that social immunisation after fungal exposure is specific, similar to recent findings for individual-level immune priming in invertebrates. Epidemiological modeling further suggests that active social immunisation is adaptive, as it leads to faster elimination of the disease and lower death rates than passive immunisation. Interestingly, humans have also utilised the protective effect of low-level infections to fight smallpox by intentional transfer of low pathogen doses ("variolation" or "inoculation").     

Social interactions in kittiwake colonies: social facilitation and/or favourable social environment

A video study of social facilitation was carried out on a kittiwake, Rissa tridactyla, colony. For the analysis, the video sequences were divided into adjacent periods of 15 s. The temporal limits of each behaviour could thus be defined and its length taken into account. There were significant differences between the behaviour of neighbouring birds during the mating of a pair and that shown at other times. A comparison of the frequencies of behaviours shown by neighbouring birds during the two alternating stages of mating (Mounting and Copulation) permitted two kinds of behaviours, which differed during mating, to be distinguished. (1) The behaviours that differed between Copulation and Mounting reveal the reaction of the neighbouring birds to Copulation (but no evidence of social facilitation could be found). (2) The behaviours that differed only between Mating sequences (case sequences) and other sequences (control sequences) had probably started before the mating started. Consequently, the temporal clustering of activities in colonies may be due to the effect of particular behaviours which could favour the appearance of certain other behaviour. This mechanism (Favourable Social Environment) can act simultaneously with social facilitation. It raises the possibility that social environment may influence greatly the production of young in colonial birds.     

Lethal mutants and truncated selection together solve a paradox of the origin of life

Background

Many attempts have been made to describe the origin of life, one of which is Eigen''s cycle of autocatalytic reactions [Eigen M (1971) Naturwissenschaften 58, 465–523], in which primordial life molecules are replicated with limited accuracy through autocatalytic reactions. For successful evolution, the information carrier (either RNA or DNA or their precursor) must be transmitted to the next generation with a minimal number of misprints. In Eigen''s theory, the maximum chain length that could be maintained is restricted to nucleotides, while for the most primitive genome the length is around . This is the famous error catastrophe paradox. How to solve this puzzle is an interesting and important problem in the theory of the origin of life.

Methodology/Principal Findings

We use methods of statistical physics to solve this paradox by carefully analyzing the implications of neutral and lethal mutants, and truncated selection (i.e., when fitness is zero after a certain Hamming distance from the master sequence) for the critical chain length. While neutral mutants play an important role in evolution, they do not provide a solution to the paradox. We have found that lethal mutants and truncated selection together can solve the error catastrophe paradox. There is a principal difference between prebiotic molecule self-replication and proto-cell self-replication stages in the origin of life.

Conclusions/Significance

We have applied methods of statistical physics to make an important breakthrough in the molecular theory of the origin of life. Our results will inspire further studies on the molecular theory of the origin of life and biological evolution.     

Social stress,mortality and aggression in colonies and burrowing habitats

High mortality was found within six mixed-sex groups of Long-Evans rats living in burrowing habitats with 58% of subordinate males dying within 4 mo. of group formation. By contrast, no subordinate deaths occured during this time in six identical adult groups(3 males and 3 females) housed in similar (1 m square) colony cages without burrows. Although aggression against intruders was also much greater in habitats than colonies --through 400 days postformation--subordinate deaths did not appear to result from direct physical injury. It seems that mimicing key features of the rat's environment enhances intermale conflict and social stress, even while providing partial protection from biting attack. Behav. Proc.:     

Social parasitism by workers in queenless and queenright Apis cerana colonies

We examined worker reproduction in queenless and queenright Apis cerana colonies to determine if they are parasitized by workers from other nests. The results demonstrate that 2-6% of workers in queenright colonies are from another nest (non-natal), but these workers are not statistically more likely to have activated ovaries than natal workers, and are therefore unlikely to be active parasites. However, in queenless colonies we found a significant difference between the proportion of non-natal (72.7%) and natal (36.3%) workers with activated ovaries. Non-natal workers also had significantly higher reproductive success than natal workers: 1.8% of workers were non-natal, but these laid 5.2% of the eggs and produced 5.5% of the pupae. Unlike A. florea, the proportion of non-natal workers does not increase in queenless nests.