Fore reef location influences spawning success and egg predation in lek-like mating territories of the bird wrasse, Gomphosus varius

Many fish spawn in aggregations, but little is understood about the dynamics governing the success of spawning interactions. Here, we evaluate the influence that location of lek-like mating territories has on spawning interactions of Gomphosus varius. We used direct observations of spawning and egg predation events as well as local population counts to compare the rates of spawning, spawning interruptions, and predation on the eggs of G. varius at Finger Reef, Apra Harbor, Guam. We hypothesized that spawning rates would be highest among seaward locations that facilitate transport of pelagic larvae from reefs and that those territories would subsequently experience higher densities of egg predators, egg predation rates, and spawning interruptions. Male spawning success was highly skewed by mating territory location, with holders of the outer, seaward mating territories being more successful than those males holding territories in the middle and inner areas of the aggregation site. Within the outer territories, male mating success was also skewed by location. Egg predation was observed occasionally and increased linearly with bird wrasse spawning frequency. The population densities of egg predators were distributed equally across the study area. Spawning interruptions occurred most frequently within the inner zone of the spawning aggregation due to greater male-male aggression in intraspecific competition for females and territories. This study provides evidence that reef location influences the spawning success, egg predation rates, and spawning interruption rates of fishes that reproduce using lek-like mating territories.

Lek Territory Size and the Evolution of Leks: A Model and a Test Using an Ungulate With a Flexible Mating System

Despite many decades of research, the evolution of the rare and unusual lek-mating system continues to be debated. The key question is: why do males defend tiny territories clustered together in an aggregation when the costs of doing so are so high? Theory and empirical work on lek evolution typically focus on why males cluster their territories. Surprisingly, the other characteristic feature of classical leks, which is the unusually small size of lek-territories, has received very little attention. Here, I argue that understanding the factors favoring the reduced size of lek-territories can provide fresh insights into the evolution of leks. I used the variable mating system of an Indian antelope, the blackbuck (Antilope cervicapra), to investigate lek territory size. Because there are few quantitative models of mating territory size, I first constructed a spatial simulation model of territory size based on male competition costs and on mating benefits generated by a female bias for mating on central lek-territories, the processes most likely to influence lek-territory size. The model generated much systematic variation in territory size within a territory-cluster and also across territory-clusters varying in the number of territorial males. I tested predictions from the model using comparative data on territory size from six blackbuck populations, and detailed spatial and temporal data from an intensively-studied population. Empirical analyses strongly supported model predictions and assumptions. Based on these findings, I present a novel hypothesis for the small size of classical lek-territories. I suggest that much of the variation in the size of lek-territories can be explained by the competition that arises from a female bias for mating on central territories and that is intensified by the number of territorial males in an aggregation. Thus, the reduced size of classical lek-territories is likely a consequence of a central mating advantage in large aggregations. I present a framework for the evolution of leks that explicitly incorporates the evolution of reduced territory size alongside the evolution of male clustering. This framework can also help explain other forms of mating systems that are based on the defense of mating territories by males.

What doesn’t kill you makes you stronger: detoxification ability as an honest sexually selected signal

Sexual selection maintains colourful signals that increase sexual attractiveness and dominance. Some sexually selected, colourful signals are pigments synthesized from ingested amino acids. The underlying metabolic pathways for these pigments often release toxic byproducts that can reduce individual survival. However, rather than discarding these otherwise harmful byproducts, animals may use them by integrating them into sexually selected traits. We tested this idea using males of the damselfly Hetaerina americana, which bear a red-pigmented wing spot that is sexually selected through male-male competition for mating territories. First, by using chromatography and confocal microscopy, we determined that the red wing spots are generated by ommochrome pigments derived from tryptophan metabolism. Second, we injected a group of males with the toxic precursor of these ommochromes, 3-hydroxy-kynurenine (3-Hk), confirming the toxicity of this compound in adult males. Finally, by using spectrophotometry and confocal microscopy, we showed that adult males injected with a LC50 of 3-Hk had more ommochromes in their wing spots than controls but similar survival, suggesting that the deposition of ommochrome pigment in the wing detoxifies the tryptophan metabolism process. Thus, we report for the first time that sexually selected pigmented signals involve the biochemical treatment of excreted compounds that could otherwise have lethal effects, a hypothesis we call “detoxifying ability signalling”. Our results provide new insights about the origin and maintenance of sexual signals, elucidating a mechanism for the evolution of honest indicators of quality that could have arisen due to natural selection.

Seasonal variation in body composition of European roe deer

Seasonal variations in whole-body composition of 43 European roe deer (Capreolus capreolus L.) collected in the southeastern part of Norway were examined. Adult deer showed a defined annual cycle in both body weight and body fat reserves. Fat accumulated in September and October, reaching a maximum of 9.2% of the ingesta-free body weight in does and 10.3% in bucks, in late fall (November and December). The depletion phase started in early January and ended in April. No intersexual differences in amplitude or synchrony of body weight or fat cycle were observed. This contrasts with results in other temperate and northern cervids and could be due to differences in life strategy, particularly reproductive effort (midsummer rut, delayed implantation, and mating territories), in European roe deer.

Territorial behaviour in males of three North American species of bumblebees (Hymenoptera: Apidae, Bombus)

The behaviour of males of the bumblebees Bombus nevadensis nevadensis, B. griseocollis, and B. rufocinctus was examined at sites in Colorado and Montana, U.S.A. Males of all three species defended individual mating territories on which they scent marked plants with cephalic chemicals, which we hypothesize to be sex pheromones. Males aggressively excluded conspecific males from the vicinity of scent-marked plants for several hours each day. At times on certain B. griseocollis territories, the great number of intruding males resulted in a near breakdown of the territorial system, with repeated aggressive interactions and turnover. In preliminary chemical analyses, dichloromethane extracts of heads of B. nevadensis and B. griseocollis were each dominated by single components, while those of B. rufocinctus, in each population studied, had three major components. Extracts of plant parts scent marked by males reveal the presence of the cephalic chemicals not present on unmarked control plants. Mating is initiated on or near territories. The behavioural and morphological correlates of male mating systems in the genus Bombus and other aculeate Hymenoptera are discussed.

Review Lecture: Mammalian mating systems

Male mammals show a diverse array of mating bonds, including obligate monogamy, unimale and group polygyny and promiscuity. These are associated with a wide variety of different forms of mate guarding, including the defence of feeding and mating territories, the defence of female groups and the defence of individual receptive females. Female mating bonds include long-term monogamy, serial monogamy, polyandry and promiscuity. Both male and female mating behaviour varies widely within species. Variation in male mating behaviour is related to the effect of male assistance in rearing young and to the defensibility of females by males. The latter is, in turn, related to female ranging behaviour and to the size and stability of female groups. Much of the variation in mammalian mating bonds and systems of mate guarding can be attributed to differences in these three variables.

Territoriality, Body Size, and Spacing in Males of the Beewolf Philanthus Basilaris (Hymenoptera; Sphecidae)

Abstract1. Males of the digger wasp Philanthus basilaris defend and scent-mark small mating territories. There is a high rate of turnover of males on territories on both a daily and seasonal basis due, in part, to predation on territorial males and the large number of usurpations of territories. 2. The outcome of aggressive interactions on territories is determined by size differences among males, rather than by their status as resident or intruder. As a result, territory holders are larger on average than non-territorial males. The latter, however, remain in the area and attempt to usurp territories or replace residents that have abandoned their perches. Evidence suggests that larger territorial males are also less subject to predation by robberflies and conspecific females. 3. The type of mating system of this species resembles those defined as leks. Males established territories in groups of up to about 50. Nests of females were not found within aggregations of territories. There is a high potential for polygyny due to the lack of maternal care of offspring, dominance interactions which consistently favor larger males and result in intense sexual selection, and asynchronous emergence of females combined with potentially longlived males. Although large males are dominant, no body size related spatial structure to the aggregations could be identified. Aggregations of territories often occur in the same location from year to year, even though males live for only one season.