The Mating System of <Emphasis Type="Italic">Habropoda pallida</Emphasis> Timberlake (Anthophorinae: Apidae)

Males of Habropoda pallida searched for recently emerged females at a location in central Arizona where many females had nested in the preceding year. Patrolling males exhibited a variety of mate locating tactics ranging from inspecting existing emergence holes to patrolling flights around flowering creosote bush. These tactics appear to be under the control of a conditional strategy, given that male behavior shifted during the day. Moreover, some marked males mounted dead females placed on the ground in the emergence area as well as mounting dead females pinned to flowers in the emergence area and at a creosote bush some distance away. At least some males exhibited site fidelity in that numerous males marked within the nest site emergence area were recaptured there; others marked at a creosote bush were also seen again at that plant. The mating system of the bee involves scramble competition with individual males attempting to locate receptive emerging and flower-visiting females before rival males. In keeping with the scramble competition hypothesis, males are considerably smaller on average than females and are only aggressive when trying to push their way past rival males already mounted on a potential mate.     

The Race for Females: The Mating System of the Red Mason Bee, Osmia rufa (L.) (Hymenoptera: Megachilidae)

The ecology of a species strongly influences the strategies with which males and females maximize their lifetime reproductive success. When males and females do not invest equally in offspring, the sex with the higher parental investment becomes a rare resource for the other. The spatial and temporal distribution of the limiting sex forms the basis of the mating system. In nest-constructing Aculeata such as the red mason bee, Osmia rufa, females perform intensive brood care, whereas males do not invest in their offspring but instead compete for access to mates. Receptive females of this species are widely distributed and do not assemble at certain places. Therefore, territorial behavior is not an advantageous mating tactic for males, which instead search for females within individual home ranges usually centered around food plants. The unmarked or defended home ranges of different males may completely overlap. Competitive searching leads to a random distribution of matings among males that is largely independent of body size. The mating system of O. rufa can be described as scramble competition polygyny.     

The mating chances of small males of the cerambycid beetleTrachyderes mandibularis differ in different environments (Coleoptera: Cerambycidae)

Some males of the cerambycid beetle Trachyderes (Dendrobias) mandibularisgained access to mates by defending a patchily distributed food resource, the fruits of saguaro cactus (Cereus giganteus).Male beetles differed greatly in fighting ability because of extreme variation in body size and a striking dimorphism in mandibular weaponry. As is typical in resource defense mating systems, larger males had an advantage in combat. Major males with their large pincer jaws invariably defeated minor males with small cutting jaws, and larger majors usually defeated smaller majors. However, although minor males were at a competitive disadvantage on saguaro fruits, they did not suffer a great penalty in terms of mating probability. In contrast, minor males have a considerably lower probability of mating at desert broom (Baccharis sarothroides)where sap ooze sites are few in number and effectively monopolized by major males (Goldsmith, S. K., Behav. Ecol. Sociobiol.20,111–115, 1987). On saguaros, minor males successfully obtained mates through scramble competition while avoiding direct physical competition with larger, territorial major males. Smaller males of either morph may have succeeded in acquiring mates in part because there were many more ripe saguaro fruits than beetles, which made it impossible for larger major males to monopolize females effectively under these conditions.     

Feeding time strategies of the fringe-toed lizard,Uma inornata,during breeding and non-breeding seasons

Summary I examined the foraging behavior during the breeding and non-breeding seasons, May and July 1986, of the fringe-toed lizard Uma inornata (Iguanidae). During the breeding season males differ from females in their diet and in their foraging time strategy, males exhibiting time minimization and females energy maximization. In May, plant associated foods were selectively eaten. Males concentrated on flowers, a readily available quick energy food, which reduced foraging time and increased time for reproductive activities. Time budgets indicate that males spend over twice as much time in the open and in movement in May than do females. Females at this time restrict their activities to the cover of perennial bushes, and feed primarily on plant foods (flowers and arthropods). Energy maximization appears to be maintained by both sexes in the non-breeding season when food resources diminished to one-half of those in the breeding season. The lizards were less selective in their July feeding habits, broadening their diets to include ground-dwelling arthropods and foliage. Predation by these lizards follows a wait-ambush mode of foraging.     

Behavioral Responses of Adult Deathwatch Beetles,Xestobium rufovillosum de Geer (Coleoptera: Anobiidae), to Light and Dark

Video tracking equipment was used to quantify the behavior of adult deathwatch beetles, Xestobium rufovillosum in a light/dark choice chamber. Effects of insect age, sex, and mating status on this behavior were analysed. The behavior recorded included the initial direction of movement, the time taken to reach the light or dark zone, the time spent in each zone, the time spent moving in each zone and the distance moved in each zone. The results show that both male and female insects 1–12 days old prefer the light zone. Insects more than 12 days old demonstrate sexually differential photoresponsive behavior. Males show a preference for the light. Females show an increasing preference for the dark, mated females more so than unmated females. The implications of these differences in behavior are discussed in relation to control programmes.     

Use of space by Necromys lasiurus (Rodentia,Sigmodontinae) in a grassland among Atlantic Forest fragments

The spatial patterns presented by the rodent Necromys lasiurus were studied through capture-mark-recapture in a grassland among Atlantic Coastal Forest fragments in Southeastern Brazil. Males moved farther than females. Males moved similar distances in the dry and wet seasons, whereas females moved significantly longer distances in the dry season. Home ranges sizes were estimated for 32 individuals, and varied from 0.02 to 0.52 ha. Males had larger home ranges than females when all data are pooled and in the wet season; in the dry season home ranges of both sexes were of similar sizes. Home range sizes did not vary significantly between seasons for either sex. Home ranges of males overlapped extensively among themselves and with females, whereas females showed mutually exclusive home ranges. The spatial patterns described here are consistent with the results found for this species in different habitats and they suggest that N. lasiurus has a promiscuous mating system.     

Determinants of spatial distribution in a population of the subalpine butterfly Oeneis chryxus

Summary This paper describes temporally varying determinants of the spatial distribution of adults in an insect population and the relationship between that distribution and the mating system. Male Oeneis chryxus butterflies were distributed nonrandomly throughout a sloping Colorado meadow divided horizontally by a dirt road into an upper and lower slope. Over an eight-year period of intensive study, the proportion of males located on the road, the upper slope, and the lower slope varied as a function of population size and sex ratio. In each year, more than half of the male population aggregated on sections of the road in a distinct and recurring pattern that was not correlated with the distribution of any food resource or thermal regime. Females were usually extremely scarce and not distributed in any pattern apparent from the few observations of them. Areas densely occupied by males were associated with visual landmarks. We hypothesize that the male distribution is determined by a pattern of movement of receptive females toward these landmarks. The road offers a thermally favorable environment with an unobstructed view in which to await the passage of scarce females. The mating system in this population has several lek-like features and supports the prediction that landmark mating is a favored strategy under conditions of female scarcity and wide dispersal of resources.     

Hilltopping, leks and female choice in the Carpenter bee Xylocopa (Neoxylocopa) varipuncta

The mating system of the Carpenter bee, Xylocopa (Neoxylocopa) varipuncta Patton, closely resembles the leks of certain vertebrates. Males defend hovering stations at small creosote bushes on ridgetops in the Sonoran Desert, as well as at large ironwood trees in dry washes. Ridgetops, like washes, may provide orientation guides for dispersing females, channelling potential mates to waiting males. During the height of the two month flight season, both males and females were more concentrated on the ridge than in the wash. Males were particularly densely aggregated at or near two prominent peaks on the study ridge. At times, two or more males occupied the same creosote bush. Females visited hovering males infrequently, and exhibited a high degree of freedom in mate choice, usually rejecting males after a close inspection.
The reduction in territorial intolerance exhibited by some males at ridgetop sites may occur: (1) because of the costs of repelling many intruders and (2) because females may choose among males through direct analysis of male phenotype, rather than by selecting a male on the basis of territory position.     

The Resource-Based Mating System of the Mediterranean Pollen Wasp Ceramius fonscolombei Latreille 1810 (Hymenoptera, Vespidae, Masarinae)

Males of C. fonscolombei patrol and perch at water collection sites or at plants of Reseda, both of which are important resources for female brood care. The mating system can be classified as resource defense polygyny modified by the existence of alternative male mating tactics. Occupying temporary territories at watercollection sites constitutes the primary tactic which is more profitable for larger males. The secondary tactic of patrolling at flowers provides a nonaggressive alternative through which smaller males gain at least some mating success. Males at water collection sites occupy considerably smaller ranges but spend a higher proportion of time patrolling than males at flowers. They frequently grapple with other males, an activity that is absent at flowers. Males at water collection sites copulate about 2.5 times more frequently than males at flowers. The copulation frequency of the males at water collection sites is positively correlated with their body size, while copulation frequency is negatively correlated with body size at flowers. Males patrolling at water collection sites and males patrolling at flowers do not differ in body size, indicating that the decision between alternative mating tactics is not made relative to body size but is influenced by other factors.     

Relative Effect of Food Supplementation and Natural Resources on Female Red Deer Distribution in a Mediterranean Ecosystem

ABSTRACT Supplementary feeding is a widespread game management practice in several red deer (Cervus elaphus) populations, with important potential consequences on the biology of this species. In Mediterranean ecosystems food supplementation occurs in the rutting period, when it may change mating system characteristics. We studied the role of food supplementation relative to natural resources in the spatial distribution, aggregation, and mean harem size of females in Iberian red deer (Cervus elaphus hispanicus) during the rut. We studied 30 red deer populations of southwestern Spain, 63% of which experienced supplementary feeding. Using multivariate spatial analyses we found that food supplementation affected distribution of females in 95% of the populations in which it occurred. Green meadows present during the mating season acted as an important natural resource influencing female distribution. Additionally, the level of female aggregation and mean harem size were significantly higher in those populations in which food supplementation determined female distribution than in populations in which female distribution did not depend on supplementary feeding. Because female aggregation and mean harem size are key elements in sexual selection, supplementary feeding may constitute an important anthropogenic element with potential evolutionary implications for populations of Iberian red deer.     

Beetle pollination of peacock moraeas (Iridaceae) in South Africa

The peacock moraeas are South African geophytes withIris-like flowers that are characterized by broad outer tepals with iridescent spots. Three of the seven species were studied and found to be exclusively visited and pollinated by beetles. The primary pollinators were hopliine (Scarabaeidae) beetles in the generaPeritrichia, Monochelus, Anisonyx andAnisochelus. These beetles visit flowers for nectar, pollen and mating.Peritrichia rufotibialis was the primary pollinator ofMoraea villosa, P. abdominalis was the primary pollinator ofM. tulbaghensis, whileMonochelus sp. nov. was the primary pollinator of the third species,M. neopavonia. High levels of fruit set attest to the effectiveness of these beetles as pollinators. Average fruit set ranged from 83.5 ± 34.8% (M. villosa) to 97.2 ± 11.6% (M. tulbaghensis). Average seed set in the various populations was more variable, but was also quite high, ranging from 77.3 ± 40.8 (M. villosa) to 342.2 ± 115.0 (M. neopavonia) seeds per capsule. Although hopliine beetles are abundant and diverse in southern Africa and commonly visit flowers, this is the first well-documented report of pollination by these beetles.     

Different rewards in female and male flowers can explain the evolution of sexual dimorphism in plants

Insects use floral signals to find rewards in flowers, transferring pollen in the process. In unisexual plants, the general view is that staminate (male) and pistillate (female) flowers obtain conspecific pollen transfers by advertising their rewards with similar floral signals. For female plants lacking food rewards, this can lead to floral mimicry and pollination by deceit. In this study, we challenge this view by presenting evidence for different rewards offered by flowers on females and males, as a mechanism promoting sexual dimorphism in Leucadendron xanthoconus (Proteaceae), a clearly sexually dimorphic shrub. The tiny beetle pollinators Pria cinerascens (Nitidulidae) depend entirely on the plants they pollinate for survival and reproduction. Male flowers provide mating and egglaying sites, and food for adults and larvae. Female flowers lack nectar and function to shelter pollinators from rain. Their flower heads have cup‐shaped display leaves, and are more closed than are those in males. On rainy days, flowers on females received 30% more visits than did flowers on males, and 90% more than they did on sunny days. When we removed display leaves in females, intact flower heads received 14 times more P. cinerascens visits than did manipulated flower heads, indicating that the cup shape attracts the beetles. In both sexes, having many flowers increased the probability of visits and the number of P. cinerascens visiting a plant. In males, the number of larvae was positively correlated with floral‐display size, while in females, seed set (pollen transfers) showed no relationship with floral‐display size. Ninety‐five per cent of the ovules received pollen and 52% matured into seeds. We explain the sexual dimorphism in L. xanthoconus as a result of an intimate partnership with P. cinerascens pollinators, in conjunction with a rainy climate. Pollinators favour large male floral displays, because they offer a reliable food source for adults and larvae. Frequent rains drive the P. cinerascens to leave males in search of the protection offered by females. Because females offer shelter, an essential resource that is not offered by male plants, they receive sufficient pollen independent of their floral‐display size. This pollination system promotes the evolution of sexually dimorphic floral signals, guiding pollinators to different rewards in male and female flowers. © 2005 The Linnean Society of London, Biological Journal of the Linnean Society, 2005, 85 , 97–109.     

Ontogeny of territoriality in the desert clickerLigurotettix coquilletti (Orthoptera: Acrididae)

Field observations and experiments showed that settlement prior to reproductive maturation strongly influenced territorial success in the desert clicker(Ligurotettix coquilletti), an acridid grasshopper in which males defend individual host plants (Larrea tridentata bushes) as mating arenas. High tendencies to move and reposition among the host plants were displayed in two distinct episodes. The first occurred during early nymphal development, and it resulted in many individuals settling on high-qualityLarrea bushes. Prior work showed thatL. coquilletti that fed on foliage from these specific bushes exhibited higher relative growth rates and therefore were expected to eclose sooner. Early-eclosing males enjoyed a priority advantage in defending high-quality bushes as mating territories, and they consequently encountered more females and mated more frequently. Despite the distribution of most insects on high-quality bushes at the time of eclosion, though, a second movement episode occurred shortly thereafter. This reshuffling contrasts markedly with the site fidelity of mature adult males, most of which settle on mating territories, and it may function as a means of examining an enlarged sample of potential sites. The above results imply that territorial success of maleL. coquilletti does not result from retaining sites defended by the parents. This point is also supported by the finding that females do not oviposit particularly close to theLarrea bushes in which they reside regardless of their quality; most egg pods are deposited in bare soil midway between the bushes. Nonetheless, certain oviposition sites may be conducive to earlier hatch, and this can lead to earlier eclosion and ultimately to defense of a valuable territory. Therefore, the parental generation, through selective oviposition, may yet influence the success of their male offspring.     

The nutritional contribution of males affects the feeding behavior and spatial distribution of females in a bruchid beetle,<Emphasis Type="Italic"> Bruchidius dorsalis</Emphasis>

The relationship between the quality/quantity of male investment and the feeding behavior of females was investigated in a bruchid weevil, Bruchidius dorsalis (Fahraeus), whose males donate nutrition via seminal fluid to females. Experiments on the effect of feeding regimes of both sexes on the mating frequency of females showed that females mated at a higher frequency if given low-quality food or poor male investment. On the other hand, the experiment that examined the effect of male investment quality on female feeding behavior showed that females receiving the high-quality investment exhibited feeding behavior less often. These results suggest that male investment and feeding behavior play the same role for B. dorsalis females. These experiments also showed that there are sex-related asymmetries in mating and feeding behaviors: females mated more often but males fed more often. Moreover, a field census suggested that only males visited non-host flowers to feed on the pollen and nectar during the non-flowering period of the host plants; females always stayed on the host plants irrespective of the flowering phenology. These results suggest that in B. dorsalis courtship role reversal and sex-specific feeding modes are fairly fixed and obligatory, and that male investment, derived from sexual selection, could affect the feeding behavior and spatial distribution of both sexes, which may have far-reaching impact in various ecological contexts.     

Spatial distributions of male and female strawberry poison frogs and their relation to female reproductive resources

In many species with a resource-based mating system, males defend resources to increase their attractiveness to females. In the strawberry poison frog, Dendrobates pumilio, suitable tadpole-rearing sites appear to be a limited resource for females. Territorial males have been suggested to defend tadpole-rearing sites to increase their access to females. In this study we investigate the spatial association between tadpole-rearing sites and the sexes as well as the spatial association of males and females. If strawberry poison frogs have resource defense polygyny, we expect males and females to be associated with tadpole-rearing sites and that females will deposit their offspring in tadpole-rearing sites inside the territories of their mates. To test this hypothesis, home range and core area sizes were calculated for both sexes and the association patterns were compared in two areas that differed in their abundance of tadpole-rearing sites. Home ranges and core areas of females were much larger than male home ranges. Females showed a clumped distribution in the vicinity of tadpole-rearing sites. Males were not clumped and were less associated with tadpole-rearing sites. Females generally did not use tadpole-rearing sites in the territory of their mates and we therefore conclude that males did not defend tadpole-rearing sites for females. Our data are consistent with the general assumption that female distribution is influenced by resource distribution and that male distribution depends on female distribution. Nevertheless, the distribution of D. pumilio females was also influenced by male spacing patterns. Males probably initially establish their core areas where female density is high and then females move among territories to sample males. Males compete vigorously for places with high female density, the defense of which is likely important for enhancing their mating success. In general, the spacing patterns did not differ between populations but the sex ratio was strongly female biased in the habitat with more tadpole-rearing sites, reflecting the direct reliance of females on these resources.     

Alternative mating strategies in a desert grasshopper: evidence of density-dependence

Field observations revealed that, on a given day, male mating behaviour in a population of the grasshopper Ligurotettix coquilletti ranged from little or no stridulation (inactive) to relatively persistent singing (active signalling). Inactive males were usually located in the territories of active signallers. Actively signalling male achieved more matings, and also more frequently approached and mounted females in incidents terminating in the male departing the female without copulating. Individuals switched between inactive and actively-signalling behaviour during their adult lives, and males that were usually active signallers achieved greater lifetime mating success. Thus, we obtained no evidence to support the hypothesis that variation in mating behaviour was maintained by negative frequency-dependent selection. By comparing the behaviour of males in two field plots maintained at different population densities, however, we found that high density was directly related to a higher incidence of inactive behaviour. Males perched on creosote (Larrea tridentata) bushes (their host plant), and certain bushes. Mating behaviour was independent of body size and, while young (<7 days old) males tended to be inactive, neither age nor the time of adult maturation during the season could fully account for the incidence of inactive behaviour among males. Instead, we suggest that the adoption of inactive behaviour resulted partly from aggressive encounters between males.     

AGGREGATION FORMATION AND ASSORTATIVE MATING IN TWO MELOID BEETLES

Males and females of the meloid beetles Lytta magister and Tegrodera aloga form large aggregations in Sonoran Desert habitat. Males and females of L. magister fly to prominent ridgetop landmarks, where they feed on flowering shrubs, mate (probably just once in any one aggregation), and disperse, with the group forming and disbanding in a few days. Males and females of T. aloga form very large, mobile bands that march across the desert flatland feeding and mating; females probably leave after a single copulation, with the result that the group becomes increasingly male-biased in its sex ratio. The aggregations persist for a minimum of 2–3 weeks. Great variation in body size characterizes both species. Positive assortative mating occurs in L. magister but not in T. aloga, possibly because males and females of the two species incur different costs and benefits for selective mating. It is probable that body size in Lytta correlates both with female fecundity and with male spermatophore size or amount of cantharidin contributed during copulation. This should favor males that mate with large females while also favoring females that mate with large males. If large individuals pair off, this will leave smaller individuals to settle for one another, leading to positive assortative mating. The same argument may not apply to T. aloga, perhaps because its copulations are shorter and its aggregations longer-lived, and therefore any one mating does not eliminate chances to copulate again within the band.     

ECOLOGICAL ASPECTS OF SEX EXPRESSION IN SUBDIOECIOUS SCHIEDEA GLOBOSA (CARYOPHYLLACEAE)

The importance of ecological factors such as sex lability, spatial segregation, and resource allocation in the evolution of dioecy were examined in Schiedea globosa. S. globosa is a subdioecious species with equal numbers of plants possessing strictly male or female function and a small proportion of hermaphrodites. The propensity for labile sex expression was under both environmental and genetic control; some plants with male function became hermaphroditic (by producing female flowers) under better growing conditions in the field and in the greenhouse. There was some spatial segregation of the sexes. Because of sex lability, more hermaphrodites than males occurred on moister slopes. Although there were not measurable sex-related differences in mortality within or between two flowering seasons, more females than males and hermaphrodites occurred at the bottom of slopes. Males and females produced the same number of ramets and inflorescences, but females had a greater number of flowers per inflorescence. Males and females had the same number of ovules (vestigial in males), but females had larger ovules and longer stigmas. Hermaphrodites and males had the same amount of pollen per flower despite the production of fruit by the hermaphrodites. In hermaphrodites, there was no apparent tradeoff within flowers between pollen production and ovule production. These results indicate that spatial segregation, sex lability, and environmental conditions influence allocation patterns of S. globosa, and in combination with high inbreeding depression and selling rates, may promote the further evolution of dioecy in S. globosa.     

Field-cage experiments on host fidelity in a pair of sympatric phytophagous ladybird beetles

Using field cages, we tested the hypothesis that two phytophagous ladybird beetles, Henosepilachna niponica (Lewis) and Henosepilachna yasutomii Katakura (Coleoptera: Coccinellidae: Epilachninae), are reproductively isolated from each other by their host fidelity alone. We planted host plants of the two species [the thistle Cirsium alpicola Nakai (Asteraceae) for H. niponica and the blue cohosh, Caulophyllum robustum Maxim. (Berberidaceae), for H. yasutomii] in 7 × 7 m cages (BT cages), and planted the two host plants and the beetles’ common food plant, the Japanese nightshade, Solanum japonense Nakai (Solanaceae), in other cages (BJT cages). We then released overwintered reproducing beetles into these cages and recorded their dispersal, the distribution of egg masses, and the incidence of copulations. In BT cages, the beetles moved almost exclusively between their own host plants, and all females laid eggs exclusively on their own host plants. In BJT cages, the beetles moved between their own host plants and the Japanese nightshade, resulting in occasional interspecific mating on the same nightshade plant. Females of both species laid eggs on their own host plants as well as on the Japanese nightshade. These results indicate that host fidelity functions as a strong barrier against gene flow between H. niponica and H. yasutomii. However, this barrier can easily be broken down if a third plant species bridges the beetle populations.