Exotic Bee Research Articles

Home-and-away comparisons of life history traits indicate enemy release and founder effects of the solitary bee, Megachile sculpturalis

Occurrences of introduced and invasive pollinators are increasing worldwide. To predict the potential impacts of exotic bees on native ecosystems we need to understand their ecological interactions. Life history traits are fundamental for understanding ecological interactions and often help to explain the spread of exotic species. We conducted home-and-away comparisons of life history traits of the first invasive bee in Europe, the sculptured resin bee Megachile sculpturalis Smith 1853. We compiled information on nest architecture, offspring, natural enemies, body size and phenology using published literature, museum specimen, data from citizen science initiatives, field observations and reared specimen. Megachile sculpturalis uses a broad variety of nesting materials for brood cell construction, including even plastic at the exotic range. Body size at warm temperate climate was similar in the native and exotic ranges, but phenology shifted forward by about one month (28.9 ± 3.3 SE days) in the exotic ranges. The abundance of natural enemies was similar between native and exotic ranges but specialist enemies were missing in the exotic ranges. These trait shifts may be explained by founder effects or ecological filtering. The comparison of life history traits in native and exotic ranges sheds light on the ecological-evolutionary process of this quickly spreading species and provides a better understanding of invasion processes in solitary bees.

Nesting biology and nest structure of the exotic bee Megachile sculpturalis.

From the 1990s, the Southeast Asia native giant resin bee Megachile sculpturalis (Smith, 1853) was introduced first to North America, and then to many countries in Europe. Despite increasing studies on its invasive potential and geographical expansion, information on nesting behaviour of this species is still extremely scarce. To increase knowledge on the nesting biology of M. sculpturalis, we studied multiple aspects of nesting and pollen provisioning in three consecutive years in artificial nests in Bologna, Italy. We observed 166 bees visiting nests, and followed individual nesting behaviour and success of 41 adult females. We measured cavity diameter in 552 nests and characterised the structure in 100 of them. More than 95% of nest diameters ranged between 0.6 and 1.2 cm, overlapping with several sympatric species of cavity-nesting hymenopterans in the study area. Most nests had a first chamber from the entrance of variable length without brood, followed by an average of about two brood cells with a mean length of 2.85 ± 0.13 cm each. The pollen stored in brood cells was almost monofloral, belonging to the ornamental plant Styphnolobium japonicum (L.) Schott. We estimated that a single female should visit ≈180 flowers to collect enough pollen for a single brood cell. These results fill knowledge gaps on the nesting biology and nest structure of the exotic M. sculpturalis, and they are discussed in relation to possible competition with native bees for nesting sites and foraging resources.

In Search of Apis mellifera pomonella in Kazakhstan.

Apis mellifera pomonella is one of two subspecies that represent the eastern limits of honey bee (Apis mellifera) distribution, and it is important to understand its biogeography and evolution. Despite this, A. m. pomonella was not investigated after its discovery 20 years ago. In particular, it is not known if it was hybridized or not with exotic subspecies introduced by beekeepers. In this study, we analysed the variation in honey bee forewing shape in Kazakhstan. Bees were collected from apiaries, where the origin of the queens was not controlled by beekeepers; they formed a group called "local bees", and apiaries where queens declared as either A. m. carnica or A. m. mellifera were obtained from queen breeders. The two later groups were called "exotic bees". We showed that local bees are still distinct from exotic ones. However, some samples showed signs of introgression with exotic subspecies from lineage C. In terms of wing shape, the local bees were most similar to lineage O. We concluded that the local bees most likely represented A. m. pomonella. We provided wing images and identification data, which can help to identify A. m. pomonella and protect it in the future. It is interesting that the nearby honey bee population sourced from China, which is not separated by any clear barrier to gene flow, belonged to lineage M.

Insights into sexual reproduction and morph compatibility of the distylous Nymphoides fallax Ornduff (Menyanthaceae)

Nymphoides fallax Ornduff (Menyanthaceae) is an aquatic distylous plant endemic to the Mexican and Guatemalan highlands. Although vegetative reproduction is frequently reported for Nymphoides species, evidence suggests a high prevalence of sexual reproduction in N. fallax. This study aimed: (i) to test homomorphic self-incompatibility, (ii) to describe aspects of floral phenology, estimate the pollen/ovule ratio and the viability of pollen grains, (iii) to evaluate floral morph proportion in natural populations, and (iv) to identify the assemblage of floral visitors, estimating their frequency and capacity to transport N. fallax pollen. The studied populations were located in Central Mexico. We carried out a controlled pollination experiment with eight treatments (n = 80), and we also estimated pollen/ovule ratio and observed floral phenology aspects. We counted the proportion of floral morphs in seven natural populations and observed the presence of visitors to 891 flowers in three natural populations. We observed pollen on the insects using scanning electron microscopy. Our findings showed that N. fallax has diurnal flowers with one-day anthesis, high stigma receptivity, high pollen viability, and intramorph self-incompatibility. The average pollen/ovule ratio (5.1 × 103) was consistent with xenogamy. Five natural populations were found to have both morphs in approximately equal proportions, and two populations consisted only of the long-style morph. An assemblage of 28 floral visitor taxa was observed in 944 visits. The most frequent visitors were exotic bees (Apis mellifera: 43.5 %) and native dipterans (Ephydridae family: 33.3 %; Stratiomyidae and Syrphidae: 7.2 %). Pollen grains were observed attached to the bodies of the most frequent visitors, suggesting that they are potentially effective pollinators. This research expands the knowledge of heterostylous syndrome and sexual reproduction in N. fallax.

Are native bees in Brazil at risk from the exposure to the neonicotinoid imidacloprid?

All across the world, different countries use Ecological risk assessments (ERA) of pesticides to pollinators as a regulatory tool to understand the safety of pesticide use in agriculture. However, pesticide application is still recognized as one of the main stress factors causing a decline in the global population of bees. In all ERA procedures, the effects of pesticides on the honey bee species Apis mellifera are used as a reference for the effects on all different bee species. To evaluate if tropical native bees are protected by the current risk assessment procedures and to propose improvements to the methods, we assessed the ecological risk of the neonicotinoid imidacloprid posed to native and exotic bee species. The risk was assessed through a low (TIER I) and an intermediate (TIER II) level of analysis. For TIER I the USEPA BeeREX model was used and for TIER II the Species Sensitivity Distribution (SSD) approach was adopted. For the imidacloprid exposure conditions, four different crops were taken into consideration; bean, passion fruit, sunflower and tomato. The imidacloprid risk on native species was assessed both by extrapolating the effects obtained to Apis species, and by using ecotoxicological data from tests performed with native species. In TIER I, the risks calculated through empirical data showed that more than 50% of the non-Apis species presented risk levels of 28–180% higher than those obtained with the extrapolation factor used in the Brazilian pesticide regulation. In TIER II, the SSDs showed that most of the native bees are more sensitive to imidacloprid than the Africanized A. mellifera. This is the first study in which an ERA of a pesticide was conducted on tropical bee species. Here we also present some gaps and perspectives for future studies aiming to improve the risk assessment of pesticides in terrestrial environments.

Invader complexes or generalist interactions? Seasonal effects of a disturbance gradient on plants and floral visitors

Disturbances can facilitate the spread of exotic plants, which establish mutualisms with exotic bees, constituting invader complexes. However, a disturbance-mediated increase in flower resources can also promote native floral visitors due to the fact that plant-pollinator interactions are generalist. We experimentally tested these ideas in northern Patagonian woodlands. In three sites, we examined the effect of harvesting intensity (HI) (0%, 30%, 50%, 70% of biomass removal) on flower density (exotic: herbs; native: herbs, shrubs, trees) and floral visitor density (exotic: honey bees, bumblebees; native: bees and wasps, hoverflies, other flies, beetles, ants). For four years, we made observations throughout the flowering period to test seasonality. HI had the most substantial positive effect on native herbs, followed by shrubs, and it was null on trees. The effects on the floral density of exotic herbs depended on site. HI enhanced the density of exotic bumblebees, native bees and wasps, and hoverflies; but it had no effect on honey bees, and it showed variable effects on the other floral-visitor groups. Although seasonality was relevant, there was no strong interaction with HI. In general, HI enhanced the density of native and exotic floral visitors, which is better explained by generalist interactions rather than by invader complexes.

Global meta‐network of legume crops and floral visitors reveals abundance of exotic bees

AbstractLegume crops (family Fabaceae, order Fabales) constitute a relevant component of the human food supply. In view of the global decline in crop production, as a result of increasing threats (such as habitat fragmentation and land use change) to pollinators, knowledge concerning legume floral visitors can contribute to world food security. In this study, a synthesis was performed of global data on interactions between legume crops and their floral visitors, in order to improve understanding of the structure of crop‐floral visitor interactions and the roles of different species. A literature review was conducted using three databases, considering 15 legumes of economic importance, enabling the construction of a meta‐network of plant‐floral visitor interactions. Soybean, alfalfa and common bean received the highest numbers of floral visitor species. A total of 208 floral visitor species were recorded, distributed in eight orders. The most diverse group was Hymenoptera (mainly bees), followed by Lepidoptera. The European honeybee Apis mellifera interacted with the highest number of plant species. Modularity analysis identified eight modules that included more than one order of floral visitors. Most species were classified as peripherals, with few links restricted to their own module. The three connector species were the bees Bombus pascuorum, B. terrestris and Megachile rotundata. The only network hub was A. mellifera. The predominance of bees seemed to be related to the predominant floral morphology among the crops. The connector and hub species were typically generalists, and all except one species (B. pascuorum) were used as managed pollinators. The crops studied have an important role in global pollination resilience, maintaining a diversified fauna of pollinators other than bees.

Beekeeping in the Desert: Foraging Activities of Honey Bee during Major Honeyflow in a Hot-Arid Ecosystem

This study investigated the outgoing and pollen-gathering foraging activities of Apis mellifera jemenitica (AMJ) and Apis mellifera carnica (AMC) under a hot-arid environment in the presence of nectar-rich melliferous Ziziphus nummularia flora. The data revealed the differential effects of weather conditions and Z. nummularia flora on the foraging activities of the studied honey bee subspecies in the Rawdat-Khuraim oasis in central Saudi Arabia. Z. nummularia exhibited two flowering seasons, from June–July (season I) and August–October (season II), with a significantly higher mean flowering density observed during season II (404 flowers/m2) than during season I (235 flowers/m2). AMJ showed significantly higher foraging activities (outgoing and pollen-gathering) than AMC (exotic bees) during all months in each flowering season. The mean outgoing and pollen-gathering foraging rates of AMJ (32.40 ± 0.67 and 4.88 ± 0.40 workers/colony/min, respectively) were significantly higher than those of AMC (15.93 ± 1.20 and 2.39 ± 0.23 workers/colony/min, respectively). The outgoing and pollen-gathering foraging activities of the two subspecies fluctuated throughout the different times of day. Foraging activities were considerably high at sunrise (SR) and low at noon (N) during both flowering seasons. We also observed seasonal variations in the foraging activities of both bee subspecies. The mean foraging activities (outgoing and pollen-gathering) were slightly higher in season I (27.43 ± 1.21 and 4.46 ± 0.45 workers/colony/min, respectively) than in season II (21.71 ± 0.86 and 3.02 ± 0.22 workers/colony/min, respectively). The thermal window analysis revealed a significant difference between the flight activities (bees exiting and returning to the nest throughout the day) of AMJ and AMC; AMJ had a higher temperature threshold than AMC. The outgoing and pollen-gathering foraging activities within each bee subspecies were positively correlated. The present study can help researchers understand the performances of honeybees and the association of their performances with weather and nectar-rich flora conditions.

Nesting, Sex Ratio and Natural Enemies of the Giant Resin Bee in Relation to Native Species in Europe.

Simple SummaryAlien bee species could have detrimental effects; in particular, they may compete with native bee species for floral resources or nesting sites. Here, we first studied the interaction in artificial trap nests, installed in a semi-urban area of north-western Italy, between the first exotic bee in Europe, Megachile sculpturalis, and native wild bees. Second, we evaluated the performance of the exotic bee by means of the sex ratio, and we screened for the presence of natural enemies affecting its brood. Our results showed that M. sculpturalis brood cells cohabited tunnels with the native Osmia cornuta. Given the exotic cells’ position within tunnels and their resin-based material, exotic cells may act as a block for native bee emergence. Moreover, our study revealed a strong male-biased sex ratio, suggesting a suboptimal reproductive trend for the M. sculpturalis local population. Additionally, we documented for the first time the presence of three natural enemies on the brood of the exotic bee that are common on native co-nesting bees. These novel findings broaden the knowledge on solitary bee invasions.Megachile sculpturalis (Smith, 1853) is the first exotic bee species in Europe. Its remarkably fast expansion across this continent is leading to a growing concern on the extent of negative impacts to the native fauna. To evaluate the interactions of exotic bees with local wild bees, we set up trap nests for above-ground nesting bees on a semi-urban area of north-western Italy. We aimed to investigate the interaction in artificial traps between the exotic and native wild bees and to assess offspring traits accounting for exotic bee fitness: progeny sex ratio and incidence of natural enemies. We found that the tunnels occupied by exotic bees were already cohabited by O. cornuta, and thus the cells of later nesting alien bees may block the native bee emergence for the next year. The progeny sex ratio of M. sculpturalis was strongly unbalanced toward males, indicating a temporary adverse population trend in the local invaded area. In addition, we documented the presence of three native natural enemies affecting the brood of the exotic bee. Our results bring out new insights on how the M. sculpturalis indirectly competes with native species and on its performance in new locations.

Competition between a native and introduced pollinator in unmanaged urban meadows

There is little understanding of the role of exotic bees in the observed pollinator decline. Recent models of species invasions predict that aggressive species have more impact; applying this theory to pollinators suggests that aggressive territorial Anthidium (Megachilidae) bees, whose range is expanding globally, could have high impacts on native bees. We examined exploitation and interference competition for floral resources between Anthidium and native bees in unmanaged urban meadows in Montreal, Canada. First, we conducted a survey of floral visits by Anthidium and native bee genera. We found high niche overlap with Megachile (Megachilidae), one of the most common genera of native pollinators in the area, suggesting high potential for exploitation competition. Second, we tested for interference competition between Anthidium and Megachile with behavioural observations of foraging on a common introduced host plant (Lotus corniculatus, Fabaceae). This presence of Anthidium decreased patch residence and number of floral visits by Megachile bees, suggesting that Anthidium has a significant per capita effect on foraging behavior of Megachile.

Bioecological and Behavioral Interaction between Pollinating Bees and the Pioneer Shrub Ludwigia nervosa in Degraded Area Suggests an Exotic Bee as Its Major Pollinator.

Simple SummaryLudwigia nervosa plants are commonly found in humid environments in the process of regeneration; however, little is known about reproductive contribution to attracting bees in fragmented environments. Therefore, we aimed to identify the bees visiting the flowers, and whether during pollen and/or nectar collection they performed pollination. The absence of pollen limitation shows that there was sufficient and efficient deposition of pollen in L. nervosa flowers during the visit, guaranteeing the formation of larger fruits and seeds with high germinative potential.The flowers of plants of the genus Ludwigia are an important source of food for several species of bees. In the current study, we conducted an experiment with the aim to describe the reproductive biology and phenology of L. nervosa; to identify the species of visiting bees; analyze the foraging behavior of bees; and to investigate whether the reproductive success of the species is related to the foraging activity of bees. We found that the flowers received visits from several native bee species (n = 7), in addition of the exotic honey bees which came to be the dominant species. During visits the majority of the bees foraged in both resources, pollen and nectar. The significantly higher production of fruits in open pollinated pollination experiment compared to artificial cross pollination, suggests honey bees as effective pollinator of this plant species in the study site. Pollen deposition occurs efficiently, given the absence of pollen limitation. Despite massive visitation of honey bees, Ludwigia nervosa is attractive to native bees, and therefore it may help to sustain population of both native and exotic pollinators in fragmented humid areas.

The Asian giant resin bee Megachile sculpturalis Smith 1853 (Hymenoptera: Apoidea: Megachilidae), a new exotic species for the bee fauna of Mallorca (Balearic Islands, Spain)

Megachile sculpturalis Smith 1853 is found for the first time on the island of Mallorca (Balearic Islands, Spain). This is the first time that this exotic bee is reported from an island and is the southernmost record in Europe so far. Specimens were found in five distant locations throughout the island, which points out the current broad distribution of this species within the island and suggests that the introduction of M. sculpturalis may have happened earlier than 2020 and went unnoticed. M. sculpturalis females were found mainly feeding and collecting pollen from Sophora japonica L. 1767 (= Styphnolobium japonicum (L.) Schott 1830) and Parkinsonia aculeata L. 1753, two exotic ornamental trees. Potential entry means and impacts of this exotic bee on local biodiversity are discussed. Island ecosystems are highly vulnerable to the negative impacts produced by exotic species. Judging from the evidence of negative effects described in the literature so far, we recommend that the invasive potential and the impact of this species on native plants and pollinators within the insular context of the Balearic Islands be addressed in the future.

Occurrence and ecological data on an exotic solitary bee accidentally introduced in Brazil

Currently, there is a global concern regarding exotic species due to, among other factors, their great ability to reproduce and spread rapidly through the novel environment. As such, these species often compete for nesting places and food resources or convey pathogens. Anthidium manicatum (Linnaeus) (Hymenoptera: Megachilidae) is a non-native solitary bee occurring in Brazil. This study aimed to collect data about the occurrence sites of this species to investigate the historical sequence of its spread throughout the country. Based on this, we estimated population data such as the number of males and females, phenology and bioclimatic niche overlap with native species. The occurrence records were retrieved from speciesLink and Global Biodiversity Information Facility. All analyses were performed in R. The collected data demonstrate that, except for the 1960s, the records of the occurrence of A. manicatum in Brazil are few and constant, being notified since the mid-1930s in at least nine Brazilian states. In total, 778 individuals were sampled, with males being recorded about 1.7 times more than females. This species seems to be bivoltine, with generations in May and November. Anthidium manicatum showed a low and moderate bioclimatic niche overlap with two native species, Anthidium sertanicola Moure & Urban and Anthidium latum Schrottky, respectively. These data provide relevant information on the biology and status of A. manicatum in Brazil. However, since most Brazilian scientific collections have not digitalized their data in the platforms consulted here, some ecological features described here may be underestimated.

Impact of Invasive Bees on Plant-Pollinator Interactions and Reproductive Success of Plant Species in Mixed Nothofagus antarctica Forests.

Invasive social bees can alter plant-pollinator interactions with detrimental effects on both partners. However, most studies have focused on one invasive bee species, while the interactions among two or more species remain poorly understood. Also, many study sites had a history of invasive bees, being hard to find sites with historical low abundances. In Patagonia, Bombus ruderatus (F.) invasion begun in 1993 and B. terrestris (L.) in 2006. Though honey bees (Apis mellifera L.) introduction started in 1859, their density is still low in some parts. By experimentally increasing honey bee densities, we evaluated the effect of honey bees and bumblebees floral visitation on native pollinator floral visitation, pollen deposition, and reproductive success of three plant species in mixed Nothofagus antarctica forests of northern Patagonia: Oxalis valdiviensis, Mutisia spinosa and Cirsium vulgare. Our results show that exotic bees became the main floral visitors. No negative association was found between invasive bee and native pollinator visitation rates, but there was evidence of potential competition between honey bees and bumblebees. Floral neighborhood diversity played an important role in pollinator behavior. Conspecific pollen deposition was high for all species, while deposition of heterospecific pollen was very high in M. spinosa and C. vulgare. Not as expected, honey bees visitation rate had a negative effect on heterospecific pollen deposition in C. vulgare. For O. valdiviensis, exotic visitation rates increased conspecific pollen deposition, which was positively related to reproductive success. Although exotic bees became main floral visitors, their contribution to reproductive success was only clear for one species.

Wild bee declines linked to plant‐pollinator network changes and plant species introductions

Abstract The mutualistic interactions of plant‐pollinator networks provide myriad economic, ecological, and cultural constituents without which there would be severe environmental and societal consequences. Plant‐pollinator networks are becoming increasingly vulnerable to disturbance through intensifying anthropogenic land use and climate change. Wild bees are central to pollination and documenting unique regional interactions between wild bees and floral hosts provides powerful insights into local ecology and biodiversity in addition to the potential to detect temporal network variation. This study characterises the changes in a northern New England wild bee plant‐pollinator network over the past 125 years and reveals a striking increase in exotic bee and plant taxa over time. Here we document that declining wild bee species have historic ties to threatened and endangered plant species. These data provide a rare insight into the fragile nature of plant‐pollinator networks. Notable specialist interactions between native taxa that were recorded in historical networks have been lost, most likely due to local extirpation of these now threatened and endangered plant species. Subsequent monitoring and conservation efforts focused on habitat restoration for declining wild bee and plant taxa are fundamental to the future preservation of regional native diversity.

Avocado crops as a floral resource for native bees of Chile

BackgroundChile is the second largest avocado producer in the world. However, there have been few studies on interactions between native bees and avocado pollination in a Chilean environment. The flowering period of avocado is very sensitive to temperature fluctuations and so environmental conditions, particularly cool temperatures, can have a strong influence on its floral behaviour. Thus, we aimed to determine whether temperature also influences bee visitation rates to avocado flowers or if this was due to the number of available flowers. Moreover, we proposed to verify the attractiveness of avocado flowers to native bees and compare flower handling time and type of floral resource collected between managed and native bees.MethodsAn avocado orchard of “Hass” cultivar located in the Mediterranean region of Chile was studied during the flowering season of 2016. The frequency of exotic and native bee species in flowers, floral phenology, and environmental temperature were analysed, and the foraging behaviours of exotic and native bee species in avocado flowers compared.ResultsFive Chilean native and two exotic species were recorded visiting avocado flowers at the studied orchard. The bees generally sought nectar rather than pollen. The European honeybee (Apis mellifera) was the most frequent flower visitor, followed by the native species Colletes cyanescens and Cadeguala occidentalis. There was a strong positive correlation between temperature and number of visits, but no significant correlation between number of open flowers and number of visits.ConclusionsNative Chilean bees visited avocado flowers and some of them were frequent floral visitors. They generally sought for nectar rather than pollen and were as fast as honeybees handling avocado flowers. The environmental temperature plays a key role in the frequency of bees in avocado flowers. The warmer weather is related to the higher number of bees visits to avocado flowers.

Bee hotels host a high abundance of exotic bees in an urban context

Bee hotels are increasingly set up by land managers in public parks to promote wild bee populations. However, we have very little evidence of the usefulness of bee hotels as tools to help the conservation of wild bees within cities. In this study, we installed 96 bee hotels in public parks of Marseille (France) for a year and followed their use as a nesting substrate by the local fauna. The most abundant species that emerged from bee hotels was the exotic bee species Megachile sculpturalis, representing 40% of all individuals. Moreover, we only detected four native bee species all belonging to the Osmia genus. More worryingly, we found a negative correlation between the occurrence of M. sculpturalis in bee hotels and the presence of native bees. One hypothesis to explain this result might be linked to the described territorial and aggressive behaviour of M. sculpturalis toward the nests built by the native fauna. This study raises the question about the usefulness of bee hotels for the conservation of native bees especially within cities harbouring high abundance of exotic bees. We provide here concrete advices to land managers to build bee hotels that can both host native bees and prevent the installation of M. sculpturalis.

Does urbanization favour exotic bee species? Implications for the conservation of native bees in cities.

A growing body of research indicates that cities can support diverse bee communities. However, urbanization may disproportionately benefit exotic bees, potentially to the detriment of native species. We examined the influence of urbanization on exotic and native bees using two datasets from Michigan, USA. We found that urbanization positively influenced exotic-but not native-bee abundance and richness, and that this association could not be explained by proximity to international ports of entry, prevalence of exotic flora or urban warming. We found a negative relationship between native and exotic bee abundance at sites with high total bee abundance, suggesting that exotic bees may negatively affect native bee populations. These effects were not driven by the numerically dominant exotic honeybee, but rather by other exotic bees. Our findings complicate the emerging paradigm of cities as key sites for pollinator conservation.

Daily fluctuations in pollination effectiveness explain higher efficiency of native over exotic bees in Lepechinia floribunda (Lamiaceae).

Despite Stebbins' principle of the most efficient pollinator being proposed decades ago, the most important pollinators are still mainly identified using the frequency of visits to flowers. This shortcoming results in a gap between the characterization of the flower visitors of a plant species and a reliable estimation of the plant fitness consequences of the mutualistic interaction. The performance of a mutualistic visitor depends on its abundance, behaviour, effectiveness (pollen removal and deposition per unit time) and efficiency (seed set per unit time) conditioned by the temporal matching between pollinator activity and temporal patterns of maturation of the sexual functions of flowers. Although there have been recent attempts to provide a conceptual and methodological framework to characterize pollinators' performance, few have combined all key elements of visitors and plants to provide an accurate estimation of pollinators' performance under natural conditions. We complement information on the flower biology and mating system of the sub-shrub Lepechinia floribunda (Lamiaceae) to provide a daily quantitative estimation of performance (effectiveness and efficiency) of the more abundant pollinators, i.e. native bumble-bees (Bombus spp.) and leafcutter bees (Megachile sp.), and the exotic honey-bee (Apis mellifera). Unlike honey-bees or leafcutter bees, native bumble-bees matched the daily pattern of nectar production and stigma receptivity, and showed higher effectiveness and efficiency. Despite the overabundance of honey-bees, visits occurred mainly when stigmas were not receptive, thus reducing the honey-bees' overall performance. Bumble-bees appear to be the most important pollinators and potential historical mediators of reproductive trait evolution in L. floribunda. Because the production of seeds by bumble-bees involved fewer pollen grains for plants and less investment in floral display than honey-bees, contemporary and expected changes in pollinator abundance may affect future L. floribunda floral evolution. If bumble-bees were to be further displaced by anthropogenic disturbance or by competition with honey-bees, their lower efficiency will select for a larger floral display increasing reproductive costs. This scenario may also impose selection to reduce dichogamy to match honey-bee foraging activity.

Expression of heat shock proteins in adult honey bee (Apis mellifera L.) workers under hot-arid subtropical ecosystems.

Heat stress elicits the expression of heat shock proteins (HSPs) in honey bee subspecies. These highly conserved proteins have significant role in protecting cells from thermal-induced stresses. Honey bees in subtropical regions face extremely dry and hot environment. The expression of HSPs in the nurses and foragers of indigenous (Apis mellifera jemenitica) and imported European (Apis mellifera ligustica and Apis mellifera carnica) honey bee subspecies after heat shock treatment were compared using SDS-PAGE. Hsp70 and Hsp82 were equally expressed in the nurses of all tested bee subspecies when exposed to 40 °C and 45 °C for 4 h. The forager bees exhibited differential expression of HSPs after heat stress. No HSPs was expressed in the foragers of A. m. jemenitica, and Hsp70 was expressed only in the foragers of A. m. ligustica and A. m. carnica at 40 °C. A prominent diversity in HSPs expression was also exhibited in the foragers at 45 °C with one HSP (Hsp70) in A. m. jemenitica, two HSPs (Hsp40 and Hsp70) in A. m. carnica, and three HSPs (Hsp40, Hsp60 and Hsp70) in A. m. ligustica. No HSPs was expressed in the control nurse and forager bees at any of the tested temperatures. These findings illustrated the differences in HSP expression among nurse and forager bees. It is obvious that the native foragers are more heat tolerant with least HSPs expression than exotic bee races. Further investigations will help to understand the potential role of HSPs in the adaptability, survival, and performance of bee subspecies in harsh climate of the subtropical regions.