Home About us Contact
|
Home About us Contact | ||
|
|
||
Social Hymenoptera (social + hymenoptera)
Selected AbstractsGenetic population structure, queen supersedure and social polymorphism in a social HymenopteraJOURNAL OF EVOLUTIONARY BIOLOGY, Issue 4 2007K. BARGUM Abstract In social insects, the emergence of multiple queening is linked to changes in a suite of traits such as the reproductive life span of queens, mating patterns and population structure. We investigated queen turnover, colony longevity, spatial distribution patterns and genetic differentiation in a population of the socially polymorphic ant Formica fusca. Genetic differentiation between the social forms was absent, and mating patterns were similar in the two forms. The spatial distribution of single- and multi-queen colonies indicated an absence of colony reproduction by budding in both colony types. However, the rate of queen supersedure was high in multi-queen colonies and absent in single-queen ones. The social structure of colonies remained stable across years, but colony mortality did not differ between the two social forms. These results imply that differences between social types may appear and persist also in sympatry, and that these differences may occur in some traits, but not others, despite the presence of homogenizing gene flow. [source] Caste fate conflict in swarm-founding social Hymenoptera: an inclusive fitness analysisJOURNAL OF EVOLUTIONARY BIOLOGY, Issue 4 2003T. Wenseleers Abstract A caste system in which females develop into morphologically distinct queens or workers has evolved independently in ants, wasps and bees. Although such reproductive division of labour may benefit the colony it is also a source of conflict because individual immature females can benefit from developing into a queen in order to gain greater direct reproduction. Here we present a formal inclusive fitness analysis of caste fate conflict appropriate for swarm-founding social Hymenoptera. Three major conclusions are reached: (1) when caste is self-determined, many females should selfishly choose to become queens and the resulting depletion of the workforce can substantially reduce colony productivity; (2) greater relatedness among colony members reduces this excess queen production; (3) if workers can prevent excess queen production at low cost by controlled feeding, a transition to nutritional caste determination should occur. These predictions generalize results derived earlier using an allele-frequency model [Behav. Ecol. Sociobiol. (2001) 50: 467] and are supported by observed levels of queen production in various taxa, especially stingless bees, where caste can be either individually or nutritionally controlled. [source] Mating biology of the leaf-cutting ants Atta colombica and A. cephalotesJOURNAL OF MORPHOLOGY, Issue 10 2006Boris Baer Abstract Copulation behavior has often been shaped by sexually selected sperm competition or cryptic female choice. However, manipulation of previously deposited ejaculates is unknown in the social Hymenoptera and the degree to which sperm competes after insemination or is actively selected by females has remained ambiguous. We studied the mating process in the leaf-cutting ants Atta colombica and A. cephalotes, which belong to one of the few derived social insect lineages where obligate multiple mating has evolved. As copulations often occur at night and in remote places, direct observations were impossible, so we had to reconstruct the sequential copulation events by morphological analysis of the male and female genitalia and by tracking the process of sperm transfer and sperm storage. We show that Atta male genitalia have two external rows of spiny teeth, which fit into a specialized pouch organ in the female sexual tract. Reconstruction of the sperm storage process indicated that sperm is transferred to the spermatheca during or immediately after ejaculation and without being mixed with sperm and seminal fluids from other males. A convergent mechanism of direct sperm transfer to the spermatheca of queens is known from two species of dwarf honeybees. Direct sperm transfer may restrict female control over the sperm storage process and the number of males that contribute to the stored sperm. J. Morphol. © 2006 Wiley-Liss, Inc. [source] Extreme queen-mating frequency and colony fission in African army antsMOLECULAR ECOLOGY, Issue 8 2004DANIEL J. C. KRONAUER Abstract Army ants have long been suspected to represent an independent origin of multiple queen-mating in the social Hymenoptera. Using microsatellite markers, we show that queens of the African army ant Dorylus (Anomma) molestus have the highest absolute (17.3) and effective (17.5) queen-mating frequencies reported so far for ants. This confirms that obligate multiple queen-mating in social insects is associated with large colony size and advanced social organization, but also raises several novel questions. First, these high estimates place army ants in the range of mating frequencies of honeybees, which have so far been regarded as odd exceptions within the social Hymenoptera. Army ants and honeybees are fundamentally different in morphology and life history, but are the only social insects known that combine obligate multiple mating with reproduction by colony fission and extremely male-biased sex ratios. This implies that the very high numbers of matings in both groups may be due partly to the relatively low costs of additional matings. Second, we were able to trace recent events of colony fission in four of the investigated colonies, where the genotypes of the two queens were only compatible with a mother,daughter relationship. A direct comparison of male production between colonies with offspring from one and two queens, respectively, suggested strongly that new queens do not produce a sexual brood until all workers of the old queen have died, which is consistent with kin selection theory. [source] Reproductive parameters vary with social and ecological factors in the polygynous ant Formica exsectaOIKOS, Issue 4 2008Rolf Kümmerli Due to their haplo-diploid sex determination system and the resulting conflict over optimal sex allocation between queens and workers, social Hymenoptera have become important model species to study variation in sex allocation. While many studies indeed reported sex allocation to be affected by social factors such as colony kin structure or queen number, others, however, found that sex allocation was impacted by ecological factors such as food availability. In this paper, we present one of the rare studies that simultaneously investigated the effects of social and ecological factors on social insect nest reproductive parameters (sex and reproductive allocation, nest productivity) across several years. We found that the sex ratio was extremely male biased in a polygynous (multiple queens per nest) population of the ant Formica exsecta. Nest-level sex allocation followed the pattern predicted by the queen-replenishment hypothesis, which holds that gynes (new queens) should only be produced and recruited in nests with low queen number (i.e. reduced local resource competition) to ensure nest survival. Accordingly, queen number (social factor) was the main determinant on whether a nest produced gynes or males. However, ecological factors had a large impact on nest productivity and therefore on a nest's resource pool, which determines the degree of local resource competition among co-breeding queens and at what threshold in queen number nests should switch from male to gyne production. Additionally, our genetic data revealed that gynes are recruited back to their parental nests after mating. However, our genetic data are also consistent with some adult queens dispersing on foot from nests where they were produced to nests that never produced queens. As worker production is reduced in gyne-producing nests, queen migration might be offset by workers moving in the other direction, leading to a nest network characterized by reproductive division of labour. Altogether our study shows that both, social and ecological factors can influence long-term nest reproductive strategies in insect societies. [source] Advanced eusociality, kin selection and male haploidyAUSTRALIAN JOURNAL OF ENTOMOLOGY, Issue 1 2008Ross H Crozier Abstract, The generation-long primacy of kin selection in explaining the evolution of advanced eusociality in social insects has been challenged in recent papers. Does this challenge succeed? I consider three questions: is kin selection still the unchallengeable explanation for the evolution of eusociality; is the male haploidy of Hymenoptera important in this explanation; and, a subsidiary question of why are there no male workers in Hymenoptera? I briefly trace the origins of kin selection back to Darwin and then consider the explanations of mutualism, group selection, parental manipulation, and kin selection and its variant ,green beard' alleles. I stress that in the kin selection equation, however written, relatedness is deeply intertwined with ecology so that both are essential. Kin selection does remain unchallengeable but, for some, the role of male haploidy has lost favour recently despite several modelling efforts all finding that it favours the evolution of eusociality. Sex allocation is deep at the heart of the evolution of hymenopteran advanced eusociality, indicating the interacting roles of population genetics and general biology. Modellers have also found no reason for a lack of male workers, so that a biological superiority of females for this role is indicated for social Hymenoptera. [source] | ||||||||||