Frequent colony fusions provide opportunities for helpers to become reproductives in the termite Zootermopsis nevadensis (original) (raw)
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Proceedings of the …, 2003
We present new hypotheses and report experimental evidence for powerful selective forces impelling the evolution of both eusociality and the soldier caste in termites. Termite ancestors likely had a nesting and developmental life history similar to that of the living family Termopsidae, in which foraging does not occur outside the host wood, and nonsoldier helpers retain lifelong options for differentiation into reproductives. A local neighborhood of families that live exclusively within a limited resource results in interactions between conspecific colonies, high mortality of founding reproductives, and opportunities for accelerated inheritance of the nest and population by offspring that differentiate into nondispersing neotenic reproductives. In addition, fertile reproductive soldiers, a type of neotenic previously considered rare and docile, frequently develop in this intraspecific competitive context. They can be highly aggressive in subsequent interactions, supporting the hypothesis that intercolonial battles influenced the evolution of modern sterile termite soldier weaponry and behaviors.
Nonrelatives inherit colony resources in a primitive termite
Proceedings of the National Academy of Sciences, 2009
The evolution of eusociality, especially how selection would favor sterility or subfertility of most individuals within a highly social colony, is an unresolved paradox. Eusociality evolved independently in diverse taxa, including insects (all ants and termites; some bees, wasps, thrips, and beetles), snapping shrimp, and naked mole rats. Termites have received comparatively less focus than the haplodiploid Hymenoptera (ants, bees, and wasps); however, they are the only diploid group with highly complex colonies and an ...
Chapter 7 The Ecology of Social Evolution in Termites
2008
Judith Korb Department Biology I, University of Regensburg, 93040 Regensburg, Germany judith.korb@biologie.uni-regensburg.de Abstract Termites (Isoptera) belong to the classical eusocial insects and their resemblance to ant colonies is so striking that they are commonly known as ‘white ants’. However, the termites evolved social life independently, long before the ants. Their different ancestry also is reflected in several fundamental differences in the organization of the colonies. This chapter aims at summarizing the state-of-the-art in termite research and comparing the results with other social invertebrate and vertebrate systems in an attempt to reveal common principles underlying social evolution. First, I provide an overview of termites’ biology and classification. I continue with a summary on the ‘hunt’ for a genetical explanation of the evolution of termite’ eusociality. Using a case study, I summarize ecological factors favoring cooperation in a lower termite and show the ...
Brood care and social evolution in termites
Proceedings of the Royal Society B: Biological Sciences, 2012
Cooperative brood care is assumed to be the common driving factor leading to sociality. While this seems to be true for social Hymenoptera and many cooperatively breeding vertebrates, the importance of brood care for the evolution of eusociality in termites is unclear. A first step in elucidating this problem is an assessment of the ancestral condition in termites. We investigated this by determining the overall level of brood care behaviour across four termite species that cover the phylogenetic diversity of the lower termites. Brood care was low in the three species (all from different families) that had an ancestral wood-dwelling lifestyle of living in a single piece of wood that serves as food and shelter. In the fourth species, a lower termite that evolved outside foraging, brood care was more common. Together with data for higher termites, this suggests that brood care in termites only becomes important when switching from a wood-dwelling to a foraging lifestyle. These results...
Molecular Ecology, 2004
Temporal and spatial analyses are seldom utilized in the study of colony genetic structure, but they are potentially powerful methods which can yield novel insights into the mechanisms underlying variation in breeding systems. Here we present the results of a study which incorporated both of these dimensions in an examination of genetic structure of subterranean termites in the genus Reticulitermes ( primarily R. flavipes ). Most colonies of this species (70%) were simple families apparently headed by outbred primary reproductives, while most of the remaining (27% of the total) colonies contained low effective numbers of moderately inbred reproductives. Mapping the spatial distribution of colony foraging sites over time revealed that despite the high colony density, the absolute foraging boundaries of most R. flavipes colonies were persistent and exclusive of other conspecific colonies, which suggests that this species is more territorial than has been implied by laboratory studies of intraspecific aggression. Nevertheless, we found a single colony (3% of all colonies) which contained the offspring of more than two unrelated reproductives. Although other studies have also described subterranean termite colonies with a similarly complex genetic composition, we demonstrate here that such colonies can form under natural conditions via the fusion of whole colonies. This study underscores how repeated sampling from individual colonies over time and space can yield information about colony spatial and genetic structure that cannot be obtained from conventional analyses or sampling methods.
Insectes Sociaux, 2006
The life of a colony of subterranean termites, such as Coptotermes formosanus Shiraki (Isoptera: Rhinotermitidae), has natural inbreeding and outbreeding cycles. Reproductives of mature colonies can be replaced by their offspring, which increases the degree of inbreeding in each generation. High degrees of inbreeding may lead to inbreeding depression. In this study we focused on mechanisms for inbreeding avoidance during swarming that do not require kin recognition. We investigated genetic differentiation between swarm aggregations (isolation by distance), genetic diversity within swarm aggregations (multiple colony origin) and genetic differentiation between sexes. Alates were collected from fi ve swarm aggregations in New Orleans, La. The genetic make-up of each swarm aggregation was then described by microsatellite genotyping. Alates from the different swarm aggregations were genetically differentiated; however, no isolation by distance up to at least 1000 m was detected. The dispersal distance of alates was suffi cient to guarantee mixing of an average of 13 colonies within swarm aggregations. On average, eleven percent of all possible pairs of alates in each swarm aggregation were putative full siblings. Genotypic frequencies differed signifi cantly between males and females. This could not be explained by sex-biased dispersal. We hypothesize sex-biased investment at the colony level to account for this difference. Genetic differentiation between the sexes and dispersal distances suffi cient to promote high genetic diversity within swarm aggregations each facilitate inbreeding avoidance. These observations are consistent with the results of previous studies demonstrating that the majority of simple family colonies in Louisiana populations are headed by unrelated and outbred pairs of reproductives.
Loss of males from mixed-sex societies in termites
Background: Sexual reproduction is the norm in almost all animal species, and in many advanced animal societies, both males and females participate in social activities. To date, the complete loss of males from advanced social animal lineages has been reported only in ants and honey bees (Hymenoptera), whose workers are always female and whose males display no helping behaviors even in normal sexual species. Asexuality has not previously been observed in colonies of another major group of social insects, the termites, where the ubiquitous presence of both male and female workers and soldiers indicate that males play a critical role beyond that of reproduction. Results: Here, we report asexual societies in a lineage of the termite Glyptotermes nakajimai. We investigated the composition of mature colonies from ten distinct populations in Japan, finding six asexual populations characterized by a lack of any males in the reproductive, soldier, and worker castes of their colonies, an absence of sperm in the spermathecae of their queens, and the development of unfertilized eggs at a level comparable to that for the development of fertilized eggs in sexual populations of this species. Phylogenetic analyses indicated a single evolutionary origin of the asexual populations, with divergence from sampled sexual populations occurring about 14 million years ago. Asexual colonies differ from sexual colonies in having a more uniform head size in their all-female soldier caste, and fewer soldiers in proportion to other individuals, suggesting increased defensive efficiencies arising from uniform soldier morphology. Such efficiencies may have contributed to the persistence and spread of the asexual lineage. Cooperative colony foundation by multiple queens, the single-site nesting life history common to both the asexual and sexual lineages, and the occasional development of eggs without fertilization even in the sexual lineage are traits likely to have been present in the ancestors of the asexual lineage that may have facilitated the transition to asexuality.
Mechanisms of inbreeding avoidance in the one-piece drywood termite Neotermes chilensis
Insectes Sociaux, 2015
Inbreeding depression refers to a decrease in fitness components in the offspring of closely related sexual pairs. Given the disadvantages of inbreeding depression, it is of interest to study the mechanisms involved in its avoidance, particularly in social insects. In termites, colonies are founded by dispersing individuals. Two types of mechanisms may account for inbreeding avoidance: indirect mechanisms that occur before the dispersing individuals come into contact (sex-biased production at colony level, sex-biased emergence timing, dispersal, and sex-biased dispersal), and an active mechanism (kin recognition) that occurs when dispersing individuals come into contact. We have used ecological, behavioral and genetic approaches to study the mechanisms of inbreeding avoidance along the complete process of colony foundation by Neotermes chilensis, i.e., from the production of dispersing individuals in the colony to the production of siblings by the newly formed reproductive pair. This is the first report to address both indirect and active mechanisms of inbreeding avoidance in the same study, in the same termite species, and through the complete process of colony foundation. The results show that dispersal is the main indirect mechanism of inbreeding avoidance and that kin recognition is unlikely as an active mechanism of inbreeding avoidance.