Divergence in male mating tactics between two populations of the soapberry bug: I. Guarding versus nonguarding

I compared male allocation to prolonged mate guarding versusnot guarding between two populations of the soapberry bug (Jaderahaematoloma) that differ in adult sex ratio: Oklahoma, USA (mean± SD adult sex ratio, 2.70 ± 0.95 males per female),and Florida, USA (1.09 ± 0.26 males per female). To predictthe reproductive performance of each mating tactic in each population,I collected data on search time per mating, time required forguarding to be effective, sperm competition, female rematingpropensity, and female resistance to guarding. Search time alonediffered significantly between the populations, being much greaterin Oklahoma (estimated as 26.2 h per mate) than in Florida (estimatedas 9.6 h per mate). For males in each region, these data wereused to model the costs and benefits of guarding for differentnumbers of oviposition bouts versus not guarding. The reproductiverate of nonguarders in Oklahoma is exceeded by that of guarderswho remain with a female for more than one oviposition bout,but in Florida, the reproductive rate of nonguarders is onlyexceeded by that of guarders who remain with a female for atleast three ovipositions. Consistent with the model, Oklahomamales in field arenas guarded more frequently than did Floridamales. However, nonguarding was common in both populations,and guarding durations were highly variable.     

The direction of mothers' and daughters' preferences and the heritability of male ornaments in red jungle fowl (Gallus gallus)

We used a breeding design involving 18 sires and 108 dams tostudy the heritabilities of male ornaments in red jungle fowl(Gallus gallus). Ornaments used by females to choose mates showedlow heritabilities, with the exception of comb and wattle measures.The general absence of heritability suggests that a geneticcovariance did not exist at the time of this study between mostmale ornaments and female preferences for those ornaments. Thisresult is contrary to a key prediction of the arbitrary or Fisherianhypothesis of sexual selection. Comb size and color are condition-dependenttraits that reflect short-term changes in health, and comb sizeof males was positively correlated with offspring weight. Ourresults are consistent with the expectation of good-genes hypothesesthat male ornaments reflect the ability of males to withstandenvironmental stresses.     

The influence of nest predation on mating strategies under polygyny

The mating status of an advertising male is one important factorfor female assessment. In species where already-mated malestry to attract additional females at some distance from theirmate, mating status may be difficult to assess. Limitationsin the time available to breed and a decrease in reproductivesuccess over the breeding season could make the costs outweighthe benefits of a time-consuming mate assessment process, whichautomatically postpones the onset of breeding. Time and energyconstraints will then limit the behavioral options for femalesin search of breeding opportunities, and females would suffera cost when assessing male mating status. Female choice maythen be better understood by analyzing the behavioral optionsfor females; the success of a strategy in which costly assessmentsare avoided and females choose mates indiscriminately, disregardingmating status ("fast" strategy), could be compared to the successof a strategy in which females carefully try to assess matingstatus ("coy" strategy). Nest predation should be included insuch an analysis because it influences the amount of male assistancefemales of polygynous males receive, as nest predation for onlyone of a polygynous male's two females leads to more male assistancefor the other female. In this study, I compare the outcome ofa "fast" strategy with that of a "coy" strategy under differentrates of nest predation. Although high probabilities of becominga mate of a polygynous male associated with a fitness reductiondecrease the relative success of a "fast" strategy, simulationsshow that high rates of nest predation considerably lower thedifference in the outcome of the two strategies. Therefore,the cost of assessing mating status must be relatively smallto be economical.     

Conformity in mate choice,the overlooked social component of animal and human culture

Although conformity as a major driver for human cultural evolution is a well-accepted and intensely studied phenomenon, its importance for non-human animal culture has been largely overlooked until recently. This limited for decades the possibility of studying the roots of human culture. Here, we provide a historical review of the study of conformity in both humans and non-human animals. We identify gaps in knowledge and propose an evolutionary route towards the sophisticated cultural processes that characterize humanity. A landmark in the study of conformity is Solomon Asch's famous experiment on humans in 1955. By contrast, interest in conformity among evolutionary biologists has only become salient since the turn of the new millennium. A striking result of our review is that, although studies of conformity have examined many biological contexts, only one looked at mate choice. This is surprising because mate choice is probably the only context in which conformity has self-reinforcing advantages across generations. Within a metapopulation, i.e. a group of subpopulations connected by dispersing individuals, dispersers able to conform to the local preference for a given type of mate have a strong and multigenerational fitness advantage. This is because once females within one subpopulation locally show a bias for one type of males, immigrant females who do not conform to the local trend have sons, grandsons, etc. of the non-preferred phenotype, which negatively and cumulatively affects fitness over generations in a process reminiscent of the Fisher runaway process. This led us to suggest a sex-driven origin of conformity, indicating a possible evolutionary route towards animal and human culture that is rooted in the basic, and thus ancient, social constraints acting on mating preferences within a metapopulation. In a generic model, we show that dispersal among subpopulations within a metapopulation can effectively maintain independent Fisher runaway processes within subpopulations, while favouring the evolution of social learning and conformity at the metapopulation scale; both being essential for the evolution of long-lasting local traditions. The proposed evolutionary route to social learning and conformity casts surprising light on one of the major processes that much later participated in making us human. We further highlight several research avenues to define the spectrum of conformity better, and to account for its complexity. Future studies of conformity should incorporate experimental manipulation of group majority. We also encourage the study of potential links between conformity and mate copying, animal aggregations, and collective actions. Moreover, validation of the sex-driven origin of conformity will rest on the capacity of human and evolutionary sciences to investigate jointly the origin of social learning and conformity. This constitutes a stimulating common agenda and militates for a rapprochement between these two currently largely independent research areas.     

Differences in preference for species-specific female calls between acoustically experienced and acoustically naive maleRibautodelphax planthoppers (Homoptera: Delphacidae)

Males of the planthopper Ribautodelphax imitanswere exposed to playbacks of either conspecific or heterospecific (R. imitantoides)female calls during their development from egg to adult, and thereafter these, as well as naive males,were offered a two- way choice between these calls. Males of all treatments approached the conspecific call significantly more often. However, males primed by the conspecific call chose the heterospecific call almost four times less often than did males primed by heterospecific calls or naive males, thus showing that the preference for conspecific calls can be partly learned. Males primed by heterospecific calls performed very similarly to completely naive males, suggesting that the signal recognition mechanism is much less sensitive to heterospecific calls than to conspecific calls. Males with experience of the conspecific female call tended to take more time to reach the call source in the trials than both other types of males. The evolutionary implications of these findings are discussed.     

Repeatability of mate choice in female red jungle fowl

We staged female mate choice trials between pairs of males andrepeated the process for each female to determine the repeatabilityof female preference for males in red jungle fowl (Gallus gallus)in the first and second half of the breeding season. We measuredmale morphological traits (the size and color of the comb andthe brightness of the hackle feathers) that females are knownto use in choosing a mate. In the first half of the breedingseason, females showed repeatability in their choices of matewith respect to the male's comb characters. Females did notshow a repeatable preference with respect to male hackle feathers,and we found no repeatability of mate choice in the second halfof the season. Females seem to primarily look at the male'scomb when choosing a mate, and other ornaments seem only ofsecondary importance.[Behav Ecol 7: 243-246 (1996)]     

Behavioral responses of a sex-role reversed pipefish to a gradient of perceived predation risk

Conspicuous behaviors such as courtship and mating often makeanimals susceptible to predation. When perceiving themselvesat an elevated level of risk, animals frequently reduce conspicuousbehaviors in tradeoff for a decrease in probability of beingpreyed upon. In the present study, we used two experiments toexamine the effect of perceived predation risk from cod (Gadusmorhud) on nonreproductive and reproductive behaviors in thesex-role reversed pipefish (Syngnathus typhle). In the firstexperiment, no differences due to predation risk were detectedin the nonreproductive behaviors of either males or females.In the second experiment, predation risk had significant effectson reproductive behaviors. Pipefish were allowed to court andcopulate at four different predation levels. We created predationlevels differing in perceived predation risk by controllingthe number of sensory modes through which pipefish could detectthe presence of a cod. As predation risk increased, pipefishcopulated and courted less frequently, swam alone (displayedand searched for conspecifics) less often, and waited longerbefore commencing courtship. These changes in behavior minimizedthe amount of time spent above the eelgrass and presumably reducedconspicuousness to visual predators. Pipefish also copulatedafter a smaller amount of courtship as predation risk increased,indicating that they may trade information concerning mate qualityfor a reduction in predation risk. No differences were foundin any response variable between males and females. The roleof operational sex ratios and intersexual competition in determiningwhich sex assumes greater costs in mate acquisition is questioned.     

No evidence of inbreeding avoidance or inbreeding depression in a social carnivore

Dispersal by young mammals away from their natal site is generallythought to reduce inbreeding, with its attendant negative fitnessconsequences. Genetic data from the dwarf mongoose, a pack-livingcarnivore common in African savannas, indicate that there areexceptions to this generalization. In dwarf mongoose populationsin the Serengeti National Park, Tanzania, breeding pairs arecommonly related, and close inbreeding has no measurable effecton offspring production or adult survival. Inbreeding occursbecause average relatedness among potential mates within a packis high, because mating patterns within the pack are randomwith respect to the relatedness of mates, and because dispersaldoes little to decrease the relatedness among mates. Young femalesare more likely to leave a pack when the dominant male is aclose relative but are relatively infrequent dispersers. Youngmales emigrate at random with respect to the relatedness ofthe dominant female and tend to disperse to packs that containgenetically similar individuals.[Behav Ecol 7: 480–489(1996)]     

Female 15-spined sticklebacks detect males with empty nests by non-visual cues

Reproductive female 15-spined sticklebacks Spinachia spinachia chose water flowing from an unmated nesting male rather than water flowing from no male. Since the female could see neither the male nor his nest, this result suggests that she received non-visual signals.     

Reproductive and subsocial behaviour in the ovoviviparous leaf beetle Gonioctena sibirica (Coleoptera: Chrysomelidae)

Abstract.

• 1 In the spring, females of the leaf beetle Gonioctena sibirica deposited larvae on the ventral surface of growing young leaves situated on the apical position of shoots of the willow Salix bakko.
• 2 The parent females remained with the larvae usually on the underside of the basal part of leaves, facing toward the base of shoots. When other arthropods approached, the females temporarily moved towards these intruders, showing aggressive behaviour such as swinging the body or stamping the legs. Many females remained with their larvae until the larvae grew into the final (fourth) instar. No female produced an additional brood in the field.
• 3 Broods from which parent females were experimentally removed suffered higher mortality than those in which females were left intact. Arthropods such as spiders and ants were observed preying on the larvae. In contrast, the survivorship of broods from which females were removed and intruders were excluded with a sticky substance applied to the base of twigs was not different from that of control broods. These results demonstrate that the main mortality factor of offspring is pedestrian arthropod predators and females physically repel the predators.
• 4 Potentially alternative reproductive strategies, such as producing a large number of offspring by iteroparity and/or larger brood(s) with less or no care, seem to be inhibited in G.sibirica by larval dependence on growing young leaves which are temporally limited and by ovoviviparity which may have limited brood size.