Ecogeographical patterns in the incidence of brood parasitism in bees

The percentage of cleptoparasitic species in a fauna of Apoidea decreases from 25–30% at high latitudes to 10–15% in the subtropics. We argue that this pattern should not be explained by an allegedly stronger seasonality at higher latitudes (that would enable parasites to better synchronize with their hosts), but rather by the unpredictability of the climate, and concomitantly host phenology and population size, in (sub)arid climates.     

Nesting ecology of stingless bees and potential threats to their survival within selected landscapes in the northern Volta region of Ghana

Stingless bees are key insects in the tropics, both as pollinators of crops and as contributors to the maintenance of floral diversity through pollination of wild plants. This study investigated the nesting ecology and threats to three stingless bee species: Meliponula bocandei (Spinola), Meliponula ferruginea (Lepeletier) and Dactylurina staudingeri (Gribodo) in three landscapes characterized as forest with logging and wild honey hunting; farmlands that experience annual wild fires and a national park. The study was carried out in July 2011 and February 2012. A total of 93 stingless bee nests were found in 48 ha (density 1.9 nests per ha), 81% in tree cavities and 19% in deserted termite mounds and in the ground. M. ferruginea was the only species using deserted termite mounds (seventeen nests) and in the ground (1 nest). Although tree size (diameter at breast height, DBH >15 cm) and density of large tree were important for nest site selection, there was no influence of tree species. M. bocandei may be restricted in choice of nest site in farmland areas by the absence of trees. Reduced availability of trees in agricultural landscape together with bush burning and wild honey collecting is the main threats to stingless bees survival and abundance which need to be addressed for their successful conservation in Ghana.     

Changes in flowering and abundance of Delphinium nuttallianum (Ranunculaceae) in response to a subalpine climate warming experiment

High‐altitude and high‐latitude sites are expected to be very sensitive to global warming, because the biological activity of most plants is restricted by the length of the short snow‐free season, which is determined by climate. Long‐term observational studies in subalpine meadows of the Colorado Rocky Mountains have shown a strong positive correlation between snowpack and flower production by the forb Delphinium nuttallianum. If a warmer climate reduces annual snowfall in this region then global warming might reduce fitness in D. nuttallianum. In this article we report effects of experimental warming on the abundance and flower production of D. nuttallianum. Plant abundance (both flowering and vegetative plants) was slightly greater on warmed than control plots prior to initiation of the warming treatment in 1991. Since 1994 experimental warming has had a negative effect on D. nuttallianum flower production, reducing both the abundance of flowering plants and the total number of flowers per plant. Flower bud abortion was higher in the heated plots than the controls only in 1994 and 1999. Results from both the warming experiment and analyses of unmanipulated long‐term plots suggest that global warming may affect the fecundity of D. nuttallianum, which may have cascading effects on the pollinators that depend on it and on the fecundity of plants that share similar pollinators.     

Reproduction of Varroa destructor in worker brood of Africanized honey bees (Apis mellifera)

Reproduction and population growth of Varroa destructor was studied in ten naturally infested, Africanized honeybee (AHB) (Apis mellifera) colonies in Yucatan, Mexico. Between February 1997 and January 1998 monthly records of the amount of pollen, honey, sealed worker and drone brood were recorded. In addition, mite infestation levels of adult bees and worker brood and the fecundity of the mites reproducing in worker cells were determined. The mean number of sealed worker brood cells (10,070 ± 1,790) remained fairly constant over the experimental period in each colony. However, the presence and amount of sealed drone brood was very variable. One colony had drone brood for 10 months and another for only 1 month. Both the mean infestation level of worker brood (18.1 ± 8.4%) and adult bees (3.5 ± 1.3%) remained fairly constant over the study period and did not increase rapidly as is normally observed in European honey bees. In fact, the estimated mean number of mites fell from 3,500 in February 1997 to 2,380 in January 1998. In May 2000 the mean mite population in the study colonies was still only 1,821 mites. The fertility level of mites in this study was much higher (83–96%) than in AHB in Brazil(25–57%), and similar to that found in EHB (76–94%). Mite fertility remained high throughout the entire study and was not influenced by the amount of pollen, honey or worker brood in the colonies. This revised version was published online in July 2006 with corrections to the Cover Date.     

Confounding effects of spatial variation on shifts in phenology

Shifts in the timing of life history events have become an important source of information about how organisms are responding to climate change. Phenological data have generally been treated as purely temporal, with scant attention to the inherent spatial aspects of such data. However, phenological data are tied to a specific location, and considerations of sampling design, both over space and through time, can critically affect the patterns that emerge. Focusing on flowering phenology, we describe how purely spatial shifts, such as adding new study plots, or the colonization of a study plot by a new species, can masquerade as temporal shifts. Such shifts can look like responses to climate change but are not. Furthermore, the same aggregate phenological curves can be composed of individuals with either very different or very similar phenologies. We conclude with a set of recommendations to avoid ambiguities arising from the spatiotemporal duality of phenological data.     

Patterns of parasite infection in bumble bees (Bombus spp.) of Northern Virginia

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Increasing precision in randomised field experiments: barnacle microtopography as a predictor of Littorina abundance

We investigated whether measurements of barnacle microtopography could be used as covariates to increase precision in randomised field experiments with intertidal Littorina populations. We used image analysis to quantify the microtopography of the barnacles within 100 cm2 quadrats in July 1994 using as variables: number of barnacles, number of dead empty barnacles, mean distance to nearest neighbouring barnacle, total area covered by barnacles, and number of pockets of different size-classes [extra-small (< 0.15 cm2), small (0.15 and < 0.30 cm2), medium ( 0.30 and < 0.45 cm2), large ( 0.45 and < 0.60 cm2), and extra-large (0.60 cm2)] at least 75% surrounded by barnacles. We then used these variables to predict the abundance of Littorina spp. in the same quadrat. Two variables: the number of extra-small pockets and the number of small pockets accounted for 50% of the variation in total littorinid snail abundance among quadrats for January 1995 and for 47% of the variation for August 1994 but for only 16% of the variation for June 1994. However the single variable, the number of barnacles, accounted for 29–36% of the variation in snail abundance on these dates and can be measured without special equipment. The best combination of covariates was the number of extra-small pockets alone. The number of extra-small pockets between barnacles may be influencing the snail abundance by providing a refuge from wave shock and heat stress/desiccation. We suggest that the availability of these refuges among the barnacles could act as a density-dependent regulator of the total population size of a particular species of Littorina.     

From micro- to macroevolution: brood parasitism as a driver of phenotypic diversity in birds

A fundamental question in biology is how diversity evolves and why some clades are more diverse than others. Phenotypic diversity has often been shown to result from morphological adaptation to different habitats. The role of behavioral interactions as a driver of broadscale phenotypic diversity has received comparatively less attention. Behavioral interactions, however, are a key agent of natural selection. Antagonistic behavioral interactions with predators or with parasites can have significant fitness consequences, and hence act as strong evolutionary forces on the phenotype of species, ultimately generating diversity between species of both victims and exploiters. Avian obligate brood parasites lay their eggs in the nests of other species, their hosts, and this behavioral interaction between hosts and parasites is often considered one of the best examples of coevolution in the natural world. In this review, we use the coevolution between brood parasites and their hosts to illustrate the potential of behavioral interactions to drive evolution of phenotypic diversity at different taxonomic scales. We provide a bridge between behavioral ecology and macroevolution by describing how this interaction has increased avian phenotypic diversity not only in the brood parasitic clades but also in their hosts.     

Non-Euglossine bees also function as pollinators of Sinningia species (Gesneriaceae) in southeastern brazil

Pollination by male and female Euglossini bees, euglossophily, was suggested for a number of neotropical Gesneriaceae species. Information on bee species other than Euglossini as pollinators of neotropical members of this family is limited, and in the tribe Sinningieae data about bee pollination are still lacking. Here, we report on floral biology and bee pollination of four Sinningia species: S. schiffneri, S. eumorpha, S. villosa, and Sinningia "canastrensis". The flower features, such as corolla size, shape, and colour, are very different among the four species, but all conform to the melittophilous syndrome. The average nectar volume and sugar amount is low in S. schiffneri, S. eumorpha, and Sinningia "canastrensis", when compared to that of S. villosa, but low nectar amounts is a general feature of Sinningia species. The main pollinators of the four species are: small Tapinotaspidini (Trigonopedia ferruginea) of S. schiffneri, large Bombini (Bombus morio) and large Centridini (Epicharis morio) of S. eumorpha, large Euglossini (Eulaema cingulata and Eufriesea surinamensis) of S. villosa, and large Euglossini (Eufriesea violascens) and Megachilini (Megachile sp.) of Sinningia "canastrensis". Out of the four species, only S. villosa is exclusively Euglossini-pollinated. The marked differences in flower features and nectar production of these Sinningia species may reflect their pollination by distinct groups of bees. These results strengthen the idea of multiple origins for the pollination systems involving bees within this genus, which is highly supported by molecular phylogenetic analyses.     

Comparative resistance in Buckfast and Canadian stocks of honey bees (Apis mellifera L.) to infestation by honey bee tracheal mites (Acarapis woodi (Rennie))

The results of bioassay and colony evaluation demonstrated that British and Texas Buckfast honey bee stocks had one-third to one-half the mean prevalence and abundance of tracheal mites as Canadian standard stock, indicating that Buckfast stocks are less susceptible to tracheal mites than Canadian standard stock. Hybrid Canadian and Buckfast stocks exhibited resistance characteristics similar to only one of their parental stocks, suggesting the colony has an unknown effect on the expression of a bee's resistance to mites. A high correlation (r _s=0.66) between abundance values from the bioassay and colony evaluations indicates that the bioassay can be used to screen bees for mite resistance.     

Social parasitism in fire ants (Solenopsis spp.): a potential mechanism for interspecies transfer of Wolbachia

One possible mechanism for interspecific transfer of Wolbachia is through the intimate contact between parasites and their hosts. We surveyed 10 species of fly parasitoids (Pseudacteon spp.) and one inquiline social parasite, Solenopsis daguerrei, for the presence and sequence identity (wsp gene) of Wolbachia. Two Wolbachia variants infecting S. daguerrei were identical to known variants infecting the two common ant host species, Solenopsis invicta and Solenopsis richteri, suggesting possible transfers of Wolbachia between this parasite and their hosts have occurred. Our data also revealed an unexpectedly high diversity of Wolbachia variants within S. daguerrei: up to eight variants were found within each individual, which, to our knowledge, is the highest reported number of Wolbachia variants infecting a single individual of any host species.     

Population regulation of brook trout (Salvelinus fontinalis) in Hunt Creek,Michigan: a 50‐year study

1. Fisheries models generally are based on the concept that strong density dependence exists in fish populations. Nonetheless, there are few examples of long‐term density dependence in fish populations. 2. Using an information theoretical approach (AIC) with regression analyses, we examined the explanatory power of density dependence, flow and water temperature on the per capita rate of change and growth (annual mean total length) for the whole population, adults, 1+ and young‐of‐the‐year (YOY) brook trout (Salvelinus fontinalis) in Hunt Creek, Michigan, USA, between 1951 and 2001. This time series represents one of the longest quantitative population data sets for fishes. 3. Our analysis included four data sets: (i) Pooled (1951–2001), (ii) Fished (1951–65), (iii) Unfished (1966–2001) and (iv) Temperature (1982–2001). 4. Principle component analyses of winter flow data identified a gradient between years with high mean daily winter flows, high daily maximum and minimum flows and frequent high flow events, and years with an opposite set of flow characteristics. Flows were lower during the Fished Period than during the Unfished Period. Winter temperature analyses elucidated a gradient between warm mean, warm minimum and maximum daily stream temperatures and a high number of minimum daily temperatures >6.1 °C, and years with the opposite characteristics. Summer temperature analyses contrasted years with warm summer stream temperatures vs years with cool summer stream temperatures. 5. Both YOY and adult densities varied several‐fold during the study. Regression analysis did not detect a significant linear or nonlinear stock–recruitment relationship. AIC analysis indicated that density dependence was present in 15 of 16 cases (four population segments × four data sets) for both per capita rate of increase (w_i values 0.46–1.00) and growth data (w_i values 0.28–0.99). The almost ubiquitous presence of density dependence in both population and growth data is concordant with results from other trout populations and other studies in Michigan.     

Gene flow of Acanthaster planci (L.) in relation to ocean currents revealed by microsatellite analysis

Population outbreaks of the coral-eating starfish, Acanthaster planci , are hypothesized to spread to many localities in the Indo-Pacific Ocean through dispersal of planktonic larvae. To elucidate the gene flow of A. planci across the Indo-Pacific in relation to ocean currents and to test the larval dispersal hypothesis, the genetic structure among 23 samples over the Indo-Pacific was analysed using seven highly polymorphic microsatellite loci. The F -statistics and genetic admixture analysis detected genetically distinct groups in accordance with ocean current systems, that is, the Southeast African group (Kenya and Mayotte), the Northwestern Pacific group (the Philippines and Japan), Palau, the North Central Pacific group (Majuro and Pohnpei), the Great Barrier Reef, Fiji, and French Polynesia, with a large genetic break between the Indian and Pacific Oceans. A pattern of significant isolation by distance was observed among all samples ( P =  0.001, r  = 0.88, n  = 253, Mantel test), indicating restricted gene flow among the samples in accordance with geographical distances. The data also indicated strong gene flow within the Southeast African, Northwestern Pacific, and Great Barrier Reef groups. These results suggest that the western boundary currents have strong influence on gene flow of this species and may trigger secondary outbreaks.     

Strongly biased sex ratio in cuckoo wasp Chrysura hirsuta (Hymenoptera: Chrysididae), a parasitoid of the mason bee Osmia orientalis

We examined the rate of parasitism and sex ratio of the cuckoo wasp Chrysura hirsuta (Gerstaecker) (Hymenoptera: Chrysididae) that emerged from nests of the mason bee Osmia orientalis Benoist (Hymenoptera: Megachilidae) in Nara, Japan. Nests of O. orientalis were found in empty shells of two snail species, Satsuma japonica (Pfeiffer) and Euhadra amaliae (Kobelt). The percentage of parasitism by cuckoo wasps per all collected cocoons tended to be high (20–50%) even though interannual variation and the average number of cocoons per nest did not differ across snail shell species within each year. Our results from three years of observation, combined with previous reports, showed that the adult sex ratio of C. hirsuta was strongly female‐biased, which suggests that the species reproduces by thelytokous parthenogenesis.     

Allometry of territory size and metabolic rate as predictors of self-thinning in young-of-the-year Atlantic salmon

1. Self-thinning is a progressive decline in population density caused by competitively induced losses in a cohort of growing individuals and can be depicted as: log₁₀ (density) = c − β log₁₀ (body mass).
2. In mobile animals, two mechanisms for self-thinning have been proposed: (i) the space hypothesis predicts that maximum population density for a given body size is the inverse of territory size, and hence, the self-thinning slope is the negative of the slope of the allometric territory-size relationship; (ii) the energetic equivalence hypothesis predicts that the self-thinning slope is the negative of the slope of the allometric metabolic rate relationship, assuming a constant supply of energy for the cohort.
3. Both hypotheses were tested by monitoring body size, population density, food availability and habitat for young-of-the-year Atlantic salmon ( Salmo salar ) in Catamaran Brook, New Brunswick. The results were consistent with the predictions of the space hypothesis. Observed densities did not exceed the maximum densities predicted and the observed self-thinning slope of −1·16 was not significantly different from the slope of −1·12, predicted by the allometry of territory size for the population under study.
4. The observed self-thinning slope was significantly steeper than −0·87, predicted by the allometry of metabolic rate, perhaps because of a gradual decline in food abundance over the study period. The decline in density was more rapid in very shallow sites and may have been partly caused by a seasonal change in water depth and an ontogenetic habitat shift rather than solely by competition for food or space.
5. The allometry of territory size may be a useful predictor of self-thinning in populations of mobile animals competing for food and space.     

Double insurance of paternity by a novel type of mating plug in a monandrous solitary mason bee Osmia bicornis (Hymenoptera: Megachilidae)

Males of some hymenopteran species are able to behaviourally induce unreceptivity to mating in females by a post‐copulatory display (post‐copulatory courtship). This method of preventing further inseminations requires a high degree of female cooperation by the female and is especially susceptible to manipulations. If mating chances are low and sexual competition between males high, males can be expected to evolve additional mechanisms to protect their fertilization opportunities. This hypothesis was checked in the red mason bee Osmia bicornis (Linnaeus, 1758; syn. Osmia rufa). Males of this species were found to use a mating plug as a reinsurance to protect their paternity, although they induce females' monandry by a post‐copulatory display. Male accessory gland secretions transferred during ejaculation form a plastic, spongy plug in the females' vagina that also contains the spermatozoa. This mating plug does not hinder rivals to mate with the female but prevents intermixing of the sperm. Thus, the sperm precedence of the first male is secured. The plug is ejected by the female after approximately 1 day when the spermatheca has been completely filled with sperm. The male accessory gland supply is sufficient for the formation of two to three plugs only and is not replenished. This pattern fits well with the low mating opportunities of O. bicornis males. The evolution of a mating plug in addition to the behavioural induction of unreceptivity to mate in females is discussed. © 2015 The Linnean Society of London, Biological Journal of the Linnean Society, 2015, 115 , 28–37.     

Population dynamics of three songbird species in a nestbox population in Central Europe show effects of density,climate and competitive interactions

Unravelling the contributions of density‐dependent and density‐independent factors in determining species population dynamics is a challenge, especially if the two factors interact. One approach is to apply stochastic population models to long‐term data, yet few studies have included interactions between density‐dependent and density‐independent factors, or explored more than one type of stochastic population model. However, both are important because model choice critically affects inference on population dynamics and stability. Here, we used a multiple models approach and applied log‐linear and non‐linear stochastic population models to time series (spanning 29 years) on the population growth rates of Blue Tits Cyanistes caeruleus, Great Tits Parus major and Pied Flycatchers Ficedula hypoleuca breeding in two nestbox populations in southern Germany. We focused on the roles of climate conditions and intra‐ and interspecific competition in determining population growth rates. Density dependence was evident in all populations. For Blue Tits in one population and for Great Tits in both populations, addition of a density‐independent factor improved model fit. At one location, Blue Tit population growth rate increased following warmer winters, whereas Great Tit population growth rates decreased following warmer springs. Importantly, Great Tit population growth rate also decreased following years of high Blue Tit abundance, but not vice versa. This finding is consistent with asymmetric interspecific competition and implies that competition could carry over to influence population dynamics. At the other location, Great Tit population growth rate decreased following years of high Pied Flycatcher abundance but only when Great Tit population numbers were low, illustrating that the roles of density‐dependent and density‐independent factors are not necessarily mutually exclusive. The dynamics of this Great Tit population, in contrast to the other populations, were unstable and chaotic, raising the question of whether interactions between density‐dependent and density‐independent factors play a role in determining the (in) stability of the dynamics of species populations.     

Perfume-collecting male euglossine bees as pollinators of a basal angiosperm: the case of Unonopsis stipitata (Annonaceae)

Pollination of Unonopsis stipitata (Annonaceae) by males of two perfume-collecting bees, Euglossa imperialis and Eulaema bombiformis (Euglossini) is described. This is the first detailed account of this pollination mode in a member of a basal angiosperm family. Pollinator behaviour, identification of the odour bouquet and electrophysiological reaction of one of the two pollinators to the odour bouquet were determined. The collected odour is produced by 'osmophores' located adaxially on the petals. Starch and polysaccharides accumulated in petals are metabolized during odour emission. Mainly monoterpenes were detected in the scent samples, among them trans-carvone oxide. This molecule is thought by several authors to be the key attractant for male Eulaema bees and may be pivotal for convergent evolution of the perfume-collecting syndrome among dicotyledonous and monocotyledonous plants. It is speculated that Unonopsis , which on the basis of molecular age dating is considered a relatively recent genus of the Annonaceae (being 15–30 million years old), has diversified in relation to male euglossine bee pollinators.     

Pollination in a cryptically dioecious plant Decaspermum parviflorum (Lam.) A. J. Scott (Myrtaceae) by pollen-collecting bees in Sulawesi, Indonesia

Decaspermum parviflorum is a common shrub or treelet in clearings in eastern Sulawesi, Indonesia. It is widely distributed in SE Asia. It produces numerous white flowers and small blue-black fruits. Individual shrubs were of two types in 1:1 ratio, one bearing staminate flowers, the other bearing flowers with both stamens and carpels. The 'hermaphrodite' flowers were shown to have sterile pollen so the species is functionally dioecious. The flowers and floral sprays of the two sexes differed in several measurements: the male flowers had more anthers and were larger and more numerous, making the corporate visual image of male sprays more than twice as large as that for sprays of female flowers. Flowers, individuals of which last only one day, opened only every second day, when all bushes flower synchronously. When the anthers burst in the morning, pollen and sterile pollen was collected vigorously by a variety of bees, mostly Apis dorsata and Nomia spp. Most of the pollen was collected within 1 h of anthesis. Anthesis in males takes place about 20 min earlier than in females; insect visitation follows this pattern. The minute quantity of nectar was collected by only few insects and mostly after the pollen had gone, if at all. Fruits were eaten by birds. The species displays many features typical of dioecious tropical plants with the unusual feature of pollen being the main food reward for pollinators. It was pollinated effectively in Sulawesi.