Does the potential strength of sexual selection differ between mating systems with and without defensive behaviours? A meta-analysis.

The Darwin-Bateman paradigm predicts that females enhance their fitness by being choosy and mating with high-quality males, while males should compete to mate with as many females as possible. In many species, males enhance their fitness by defending females and/or resources used by females. That is, males directly defend access to mating opportunities. However, paternity analyses have repeatedly shown that females in most species mate polyandrously, which contradicts traditional expectations that male defensive behaviours lead to monandry. Here, in an extensive meta-analysis, encompassing 109 species and 1026 effect sizes from across the animal kingdom, we tested if the occurrence of defensive behaviours modulates sexual selection on females and males. If so, we can illuminate the extent to which males really succeed in defending access to mating and fertilisation opportunities. We used four different indices of the opportunity for sexual selection that comprise pre-mating and/or post-mating episodes of selection. We found, for both sexes, that the occurrence of defensive behaviours does not modulate the potential strength of sexual selection. This implies that male defensive behaviours do not predict the true intensity of sexual selection. While the most extreme levels of sexual selection on males are in species with male defensive behaviours, which indicates that males do sometimes succeed in restricting females' re-mating ability (e.g. elephant seals, Mirounga leonina), estimates of the opportunity for sexual selection vary greatly across species, regardless of whether or not defensive behaviours occur. Indeed, widespread polyandry shows that females are usually not restricted by male defensive behaviours. In addition, our results indicate that post-mating episodes of selection, such as cryptic female choice and sperm competition, might be important factors modulating the opportunity for sexual selection. We discuss: (i) why male defensive behaviours fail to lower the opportunity for sexual selection among females or fail to elevate it for males; (ii) how post-mating events might influence sexual selection; and (iii) the role of females as active participants in sexual selection. We also highlight that inadequate data reporting in the literature prevented us from extracting effect sizes from many studies that had presumably collected the relevant data.

Heat-hardening effects on mating success at high temperature in Drosophila melanogaster.

Reproduction is strongly influenced by environmental temperature in insects. At high temperature, mating success could be influenced not only by basal (non-inducible) thermotolerance but also by inducible plastic responses. Here, mating success at high temperature was tested in flies carrying contrasting genotypes of heat resistance in Drosophila melanogaster. The possible heat-hardening effect was tested. Mating success did not differ between heat-resistant and heat-sensitive genotypes when tested both at high (33 °C) and benign (25 °C) temperature, independently of the heat-hardening status. Importantly, heat-hardening pre-treatment increased in a 70% the number of matings at 33 °C in a mass-mating experiment. Further, mating latency at 33 °C was shorter with heat hardening than without it in single-pair assays Heat-hardening had previously been showed to improve short-term thermotolerance in many organisms including Drosophila, and the present results show that heat hardening also improve mating success at elevated temperature. Previous exposures to a mild heat stress improve short-term mating success as a plastic response of ecological relevance. Such heat-hardening effects on mating success should be relevant for predicting potential evolutionary responses to any possible current scenery of global warming, as well as in sterile insect release programs for pest control in elevated temperature environments.

To be or not to be? Mating success and survival trade-offs when switching between alternative reproductive tactics.

Hormones underlie the decision of assuming a territorial or a nonterritorial role, with territorial individuals usually having higher hormonal levels than nonterritorial individuals. As a territorial status is linked to higher mating opportunities, it is unclear why animals do not keep high hormonal levels and one explanation is that this would imply survival costs. We have tested this using males of the territorial damselfly Argia emma in the field. We increased juvenile hormone (JH) levels using methoprene in both territorial and nonterritorial males and predicted that: (i) males will keep (the case of territorial males) or become (the case of nonterritorial males) territorial after hormonal increase, and (ii) there will be an increase in mating success for nonterritorial males only and an impaired survival for both male tactics. Hormonally treated males remained or became territorial but had their survival impaired compared with control groups. Also, hormonally treated, ex-nonterritorial males increased their mating success compared with the other control, nonterritorial males. The reduced survival can be explained proximally by the energy devoted either to the enhanced aggression showed during territory defence or immune function (as detected previously in damselflies). Although nonterritorial males may increase their mating success by switching to a territorial tactic, they are possibly unable to do it naturally as JH is dietary dependent and usually nonterritorial animals are in poorer condition than territorial animals.

Production of Sexuals and Mating Frequency in the Stingless Bee Tetragonisca angustula (Latreille) (Hymenoptera, Apidae).

Queen, worker, and male production was studied for 1 year in three queenright colonies of Tetragonisca angustula (Latreille). We sampled brood combs monthly and noticed that the number of brood cells and production of individuals were similar among colonies. Although the production of queens did not vary significantly, the frequencies of workers, males, and the number of cells among the combs varied over time. The production of males was highly seasonal, occurring mostly from February to April, coinciding with the period of intense brood cells production, when colonies produced more males and less workers, resulting in a negative correlation. Although the frequency of queens has not varied in time, the seasonal availability of males affected the mating frequency and the time spent since emergence until fertilization of queens. In the T. angustula colonies studied, the population dynamics was highly seasonal and the mating success depended of male production, according to the season.

Are larger and/or more symmetrical Drosophila melanogaster (Diptera, Drosophilidae) males more successful in matings in nature?

Are larger and/or more symmetrical Drosophila melanogaster (Diptera, Drosophilidae) males more successful in matings in nature? Sexual selection in Drosophila melanogaster, related to body size and fluctuating asymmetry in wing length and number of sex comb teeth in males, was tested in natural conditions. Males collected in copula were significantly larger than those collected as a single, while no difference in mean number of sex comb teeth between copulating and single males was observed. On the other hand, single males had greater asymmetry both for wing length and number of sex comb teeth than their mating counterparts. It looks like that symmetry of these bilateral traits also may play a role in sexual selection in this dipteran species in nature.

São maiores e/ou mais simétricos os machos de Drosophila melanogaster (Diptera, Drosophilidae) com mais sucesso nos acasalamentos na natureza? A seleção sexual em Drosophila melanogaster foi testada em condições naturais. Os machos coletados em cópula foram significativamente maiores do que na amostra controle, enquanto que diferenças no número médio de dentes do pente sexual não foram estatisticamente significativas. Por outro lado, os machos que não estavam copulando no momento da coleta foram mais assimétricos, tanto em relação ao comprimento das asas como em relação ao número de dentes do pente sexual. Parece que a simetria dos traços bilaterais pode ter um papel na seleção sexual desta espécie na natureza.

Inicio de la época reproductiva y tiempo de defensa del territorio en machos de Colinus leucopogon (Galliformes: Odontophoridae)

Reproductive season onset and time invested in territory defense in Colinus leucopogon males (Galliformes: Odontophoridae). The factors that determine the onset of the reproductive season and the relationship between territory defense and mating success of Colinus leucopogon males are unknown. Here I report on climatic variables influencing the time of permanence on the territory, and how this affects the species mating success. I also analyze the relationship between the time devoted by males on territory defense and the relationship of song and territorial characteristics. The onset of the reproductive season was determined by an amount of rain greater than 14.3mm during March, favouring the food availability and nesting places abundance, and also allowed an increase in the reproductive success of Colinus leucopogon. The time invested in territory defense by males was not related with their mating success. Moreover, the duration in territory defense was similar for males that paired, compared with those that did not. In addition, song and territory characteristics were not related with males invested time in their territory defense. Therefore, this could be another reason explaining the lack of a relationship between the duration in the territories by males and pair formation, and suggests that song characteristics strongly influence the formation of pairs in this species. Rev. Biol. Trop. 59 (1): 363-372. Epub 2011 March 01.

Los factores que determinan el inicio de la época reproductiva, y la relación entre el tiempo que un macho de Colinus leucopogon defiende su territorio con el éxito reproductivo del mismo son desconocidos. Por lo tanto aquí se reporta el efecto de variables climáticas sobre el inicio de la época reproductiva, y el efecto de la duración de los machos en su territorio con el éxito de adquirir pareja. También se analiza la relación entre la duración de los machos en su territorio con las características del canto y el territorio. Precipitaciones superiores a 14.3mm en marzo determinaron el inicio de la época reproductiva. Esto favoreció el incremento de alimento y sitios para anidar, lo que podría incrementar el éxito reproductivo de la especie. La duración de los machos dentro de su territorio no se asoció con la adquisición de pareja, debido a que machos que logran emparejarse duraron un tiempo similar en sus territorios, que machos que no se emparejaron. Las características del canto y el territorio tampoco se relacionaron con la duración del macho dentro de su territorio. Por lo tanto esto puede ser otra causa para que no se haya encontrado una relación entre la duración del macho en su territorio con la formación de parejas, ya que las características del canto son las que más influyen en la formación de parejas en esta especie.

Atividade reprodutiva de Physalaemus signifer (Anura, Leptodactylidae) em ambiente temporário

The breeding activity of Physalaemus signifer (Girard, 1853) was monitored from July 1999 to July 2000 in a temporary pond in Palmital, Municipality of Saquarema, State of Rio de Janeiro, Atlantic Rain Forest, Brazil. Males were sexually actives only in four nights, arriving at the pond on the early rainy season. Males in amplexus were larger and spent more nights in the reproductive aggregation than solitary ones. The number of nights was correlated with the mass of the males. Males adopted satellite behavior as alternative tactic for mate acquisition. Changes between calling and satellite tactics were observed in different nights. Calling males were not larger and heavier than satellite ones. Satellite behavior seemed to be related with the order of arrival on the pond. Size and mass of males did not influence the results of fights. Resident males won the majority of agonistics combats. Three types of vocalizations are described: advertisement, territorial, and encounter calls.

Atividade reprodutiva de Physalaemus signifer (Anura, Leptodactylidae) em ambiente temporário

The breeding activity of Physalaemus signifer (Girard, 1853) was monitored from July 1999 to July 2000 in a temporary pond in Palmital, Municipality of Saquarema, State of Rio de Janeiro, Atlantic Rain Forest, Brazil. Males were sexually actives only in four nights, arriving at the pond on the early rainy season. Males in amplexus were larger and spent more nights in the reproductive aggregation than solitary ones. The number of nights was correlated with the mass of the males. Males adopted satellite behavior as alternative tactic for mate acquisition. Changes between calling and satellite tactics were observed in different nights. Calling males were not larger and heavier than satellite ones. Satellite behavior seemed to be related with the order of arrival on the pond. Size and mass of males did not influence the results of fights. Resident males won the majority of agonistics combats. Three types of vocalizations are described: advertisement, territorial, and encounter calls.