Low mating frequency of queens in the stingless bee Scaptotrigona postica and worker maternity of males.

Kin selection models of intracolonial conflict over the maternity of males predict that social hymenopteran workers should favour the production of sons and nephews over brothers when the effective mating frequency (me) of the queen is low (me2. Stingless bees have been used to support these models in that me within the group is considered low and workers are thought often to monopolise the parentage of males. We genetically analysed 20 worker and 20 male pupae from each of 10 colonies of the stingless bee Scaptotrigona postica (= Scaptotrigona aff. depilis) using six microsatellite loci and demonstrate queen monandry in eight nests and apparent low me in the other two. However, four colonies contained an additional matriline, possibly due to queen supersedure (serial polygyny), which complicated their genetic structure. Across colonies, workers were responsible for the maternity of 13% of all males. These data are broadly in agreement with predictions from kin selection theory, though the question remains open as to why workers do not secure a greater share of male maternity in this and other stingless bee species in which workers are more closely related to nephews than brothers.

Self-assessment by males during energetically costly contests over precopula females in amphipods

In animal contests, individuals can either engage in mutual assessment of both their own and their opponent's resource-holding potential (RHP) and adjust their behaviour according to estimated differences, or instead persist in accordance with thresholds determined by assessment of just their own RHP. We examined the predictions of alternative mutual assessment and self-assessment models for decision rules in contest resolution during struggles between males over females in precopula in the amphipod Gammarus pulex. Contest duration was positively related to the weight of the loser but not the weight of the winner. Our results support the hypothesis that males rely on information about their own RHP in determining contest behaviour and do not use information about their opponent. Fighting was energetically costly, and energy reserves were depleted during contests. Contest duration was associated with the physiological state of the loser (but not the winner) at the end of the contest, and to a lesser extent his size, further supporting self-assessment. (c) 2006 The Association for the Study of Animal Behaviour. Published by Elsevier Ltd. All rights reserved.

Paternity frequency and maternity of males in some stingless bee species

In monogynous hymenopteran societies, the number of mates of a queen strongly influences the potential for conflict between workers and queens over the maternity of males. Queens always 'prefer' their own sons to sons of workers, regardless of queen mating frequency. When a queen mates once, workers are more closely related to, and therefore are expected to prefer, their own sons and then sons of sisters to sons of the queen. However, if effective paternity frequency exceeds 2, workers on average should prefer queen-produced males to males produced by their sisters. We studied the queen mating frequency of seven stingless bee species: the Mexican species Scaptotrigona mexicana , S. pectoralis and the Australian species Austroplebeia symei , Trigona clypearis , T. hockingsi , T. mellipes and T. sapiens . We then determined whether males arise from eggs laid by workers or queens in A. symei , T. clypearis , T. hockingsi and T. mellipes . We show that all seven species investigated are most likely singly mated and that the queen dominates reproduction. This indicates that the queen's mating frequency alone does not determine whether workers or the queen produces the males.

Doubly duped males: the sweet and sour of the orchid's bouquet

Flowers of the orchid genus Ophrys resemble female insects, and thereby sexually deceive, attract and are pollinated by male insects. Floral bouquet is thought to play a major role in this sexual mimicry, although the search for functional odour components has been something of a chemical ecologist's Holy Grail. Two new papers unravel the exquisite intricacy of the chemical deception by the orchid.

Large body size for winning and large swords for winning quickly in swordtail males, Xiphophorus helleri

Contestants can either assess their own resource-holding potential relative to their opponent (mutual assessment) or rely solely on the assessment of their own fighting ability (self-assessment). To discriminate between these possibilities, we staged dyadic territorial contests between 'size-matched' male swordtails. These contests consist of a combination of ritualized displays and direct fighting. Although size differences were small, winners were larger than losers and smaller fish tended to be winners only when the size difference was negligible. Body size, however, did not influence contest duration and there was no increase in contest duration with mean body size; thus, there is no support for self-assessment in these animals. We also examined the effects of the sword, which comprises a sexually selected extension used in female choice that reduces swimming efficiency but increases acceleration. The length of the sword (adjusted for body size) did not differ between winners and losers; however, losers conceded earlier if the opponent had a large sword for its body size but this decision was independent of the loser's own sword length. Losers thus assessed the swords of winners, which precludes self-assessment; however, because winners appeared not to assess the swords of losers, this does not fully support the idea of mutual assessment. (c) 2008 The Association for the Study of Animal Behaviour. Published by Elsevier Ltd. All rights reserved.