Evolution of Eusociality in Termites

Thorne, Barbara L.

doi:10.1146/annurev.ecolsys.28.1.27

Cited by 291 publications

(263 citation statements)

References 102 publications

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“…Our results are consistent with a long history of research supporting competition and enemy pressure as primary selective pressures favoring the evolution of sociality and reproductive skew in social insects (Lin and Michener 1972;West-Eberhard 1975;Evans 1977;Strassmann and Queller 1989;Alexander et al 1991;Crespi 1994;Stern and Foster 1996;Brockmann 1997;Shellman-Reeve 1997;Thorne 1997;Queller and Strassmann 1998) and cooperatively breeding vertebrates (Emlen 1982(Emlen , 1991Brown 1987). In many vertebrates and some insects, cooperative breeding appears to be favored by habitat saturation, that is, the extreme scarcity of suitable, unoccupied territory.…”

Section: Discussionsupporting

confidence: 90%

“…In several taxa, notably ants and termites, highly cooperative social life has resulted in both marked ecological dominance and much higher population densities than in noneusocial relatives (Oster and Wilson 1978;Wilson 1990). Recent attempts to explain the taxonomically scattered origins of eusociality outside the Hymenoptera have focused more specifically on the coincidence of strong enemy pressure with the use of enclosed nest sites that are valuable, defensible, and that foster kin interactions (Alexander et al 1991;Crespi 1994;Thorne 1997). Queller and Strassmann (1998) have termed this suite of characteristics the ''fortress defender'' mode of eusociality as opposed to the ''life insurer'' mode common in Hymenoptera.…”

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Multiple Origins of Eusociality Among Sponge-Dwelling Shrimps (Synalpheus)

et al. 2000

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Abstract. As the most extreme expression of apparent altruism in nature, eusociality has long posed a central paradox for behavioral and evolutionary ecology. Because eusociality has arisen rarely among animals, understanding the selective pressures important in early stages of its evolution remains elusive. Employing a historical approach to this problem, we used morphology and DNA sequences to reconstruct the phylogeny of 13 species of sponge-dwelling shrimps (Synalpheus) with colony organization ranging from asocial pair-bonding through eusociality. We then used phylogenetically independent contrasts to test whether sociality was associated with evidence of enhanced competitive ability, as suggested by hypotheses invoking an advantage of cooperation in crowded habitats. The molecular, morphological, and combined data each strongly supported three independent origins of monogynous, multigenerational (eusocial) colony organization within this genus. Phylogenetically independent contrasts confirmed that highly social taxa, with strong reproductive skew, have significantly higher relative abundance within the host sponge than do less social taxa, a result that was robust to uncertainty in tree topology and varying models of character change. A similar tendency for highly social species to share their sponge with fewer congener species was suggestive, but not significant. Because unoccupied habitat appears to be limiting for many sponge-dwelling shrimp species, these data are consistent with hypotheses that cooperative social groups enjoy a competitive advantage over less organized groups or individuals, where independent establishment is difficult, and that enemy pressure is of central importance in the evolution of animal sociality.

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Section: Discussionsupporting

confidence: 90%

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Multiple Origins of Eusociality Among Sponge-Dwelling Shrimps (Synalpheus)

et al. 2000

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“…These older instars can function as workers and they can develop into soldiers or two types of reproductives: winged sexuals that found a new nest elsewhere or neotenic reproductives that inherit the natal breeding position when the current reproductives are unhealthy or die. This life type is considered to be phylogenetically basal [17,18], and characteristic for dampwood termites (Termopsidae), drywood termites (Kalotermitidae) and a few Rhinotermitidae (e.g. Prorhinotermes; figure 1a).…”

Section: Introductionmentioning

confidence: 99%

Brood care and social evolution in termites

et al. 2012

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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 imply that early social evolution in termites was driven by benefits of increased defence, while eusociality in Hymenoptera and cooperative breeding in birds and mammals are primarily based on brood care.

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“…There are several other major differences between the Isoptera and Hymenoptera (1), most notably (i) isopteran workers can be either sex, whereas worker hymenopterans are always female; and (ii) immature isopterans resemble adults and are included in the worker caste, whereas immature hymenopterans require continual care by adult workers. For these reasons, it is believed that eusociality evolved independently in the Isoptera and Hymenoptera (2,3). The order Isoptera is divided into the lower and higher termites on the basis of two distinguishing characteristics: the dependence of lower termites on protozoan symbionts for cellulose digestion and the adult status of workers in higher termites, which precludes further differentiation by workers.…”

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Social exploitation of hexamerin: RNAi reveals a major caste-regulatory factor in termites

Zhou

Scharf

2006

Proc. Natl. Acad. Sci. U.S.A.

221

211

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Lower termites express a unique form of eusocial polyphenism in that totipotent workers can differentiate into either soldier or reproductive caste phenotypes. In this initial effort using RNA interference in termites, we found that two hexamerin genes, Hex-1 and Hex-2, participate in the regulation of caste polyphenism. Our methodology involved a dual gene-silencing approach that used a single short-interfering RNA fragment to silence the two homologous hexamerin genes. We performed validation studies that evaluated effects on nontarget housekeeping genes, silencing of a nonhousekeeping control gene, and effects at the protein level. We found that the two hexamerin proteins, which are inducible by the morphogenetic juvenile hormone and which constitute a significant proportion of total termite protein, suppress juvenile-hormone-dependent worker differentiation to the soldier caste phenotype. This mechanism allows termite colonies to retain high proportions of altruistic worker caste members, thus apparently enhancing colony-inclusive fitness. These findings demonstrate a unique status quo regulatory mechanism for termite worker caste retention and provide an example of previously undescribed preadult developmental͞caste-regulatory genes from any social insect.sociogenomics ͉ RNA interference ͉ short-interfering RNA ͉ juvenile hormone ͉ phenotypic plasticity

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Evolution of Eusociality in Termites

Cited by 291 publications

References 102 publications

Multiple Origins of Eusociality Among Sponge-Dwelling Shrimps (Synalpheus)

Multiple Origins of Eusociality Among Sponge-Dwelling Shrimps (Synalpheus)

Brood care and social evolution in termites

Social exploitation of hexamerin: RNAi reveals a major caste-regulatory factor in termites

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