Relationships Between Phenotype, Mating Behavior, and Fitness of Queens in the Ant Lasius Niger

Abstract

Abstract. Considerable attention has focused on why females of many species mate with several males. For social hymenopteran insects, efforts have primarily concentrated on determining whether multiple mating increases colony performance due to the increased genetic diversity. Most of these studies are correlative because it is difficult or impossible to experimentally mate queens in most species. Thus, the positive associations found between multiple paternity and colony fitness in some cases may not be due to direct effects of genetic diversity but could, in theory, arise from high-quality queens having more mates. Here we show that in the ant Lasius niger variation in the number of matings covaries with queen phenotype. Young queens that were heavier at the time of the mating flight were significantly more likely to mate with several males. As a result, heavier queens stored more sperm. The initial weight of queens was significantly associated with the probability of surviving mating flights during the two years of the study, with queens of intermediate weight having the highest across-year survival. Queen initial weight was also significantly and positively associated with the quantity of brood at the time of the first worker eclosion as well as colony productivity at the time of hibernation. By contrast, there was little evidence for a positive effect of the number of matings on colony performance when the effect of mate number and queen initial weight were considered simultaneously.

Influence of queen phenotype, investment and maternity apportionment on the outcome of fights in cooperative foundations of the ant Lasius niger

“…To our knowledge, whether egg-laying rate is positively associated with queen mating frequency has not been studied in social insects. The finding that mating status of queens was not associated with head size or initial body weight contrasts with the results of Fjerdingstad & Keller (2004), who reported a positive relationship between queen phenotype and mating behaviour. In their study, heavier queens of L. niger at the time of mating flights were more likely to mate with several males.…”

“…Our genetic analyses are consistent with previous studies showing that L. niger queens can mate with up to four males during large-scale mating flights (Boomsma & van der Have 1998;Fjerdingstad et al 2002;Fjerdingstad & Keller 2004). We found a positive association between queen mating frequency and apportionment of maternity at the time of emergence.…”

Rapid determination of sperm number in ant queens by flow cytometry

“…Queens of all species were of unknown age, and their mating frequency was not determined. Nevertheless, genetic analyses previously showed that queens of L. humile mate once (monandry) (Krieger and Keller, 2000), while queens of L. niger (Boomsma and Van der Have, 1998;Fjerdingstad and Keller, 2004) and P. pygmaea (Trontti et al, 2007) can mate multiply (polyandry). No information is currently available on queen mating frequency for Tapinoma erraticum and Crematogaster scutellaris.…”

“…A usual method consists in dissecting the spermatheca and dispersing sperm cells in a physiological buffer (usually saline) solution, and then counting samples of sperm suspension in aliquots placed in a cell count chamber (e.g., hemacytometers, Makler chamber) under a microscope (Duchateau and Mari n, 1995;Boomsma, 1997, 1998;Fjerdingstad and Keller, 2004;Keller and Passera, 1992;Stein et al, 1996;Tschinkel 1987;Woyciechowski and Krol, 1996). The method can be refined by marking sperm cells with a fluorescent DNA-staining solution (e.g., Hoechst; Sakaluk and O Day, 1984) and counting under a microscope equipped for epifluorescence microscopy, eventually after fixation in glacial acetic acid (Wiernasz et al, 2001).…”

Selfish strategies and honest signalling: reproductive conflicts in ant queen associations

“…Cofounding queens that anticipate queen elimination may therefore invest less in reproduction than singly founding conspecifics, a prediction that has found empirical support (Bernasconi & Strassmann 1999;Cahan 2001). However, abstaining from reproduction is costly to all individuals in the colony because the survival probability of incipient colonies is positively related to the number of workers (Adams & Tschinkel 1995;Sommer & Hö lldobler 1995;Fjerdingstad & Keller 2004). We therefore expect that queens may be able to (i) assess the quantity of developing brood and the number of cohabiting queens, and (ii) adjust their reproductive effort according to the amount of brood, but only when competing queens are present.…”