Abdulaziz S. Alqarni

Population genomics of the honey bee reveals strong signatures of positive selection on worker traits

Significance Most hypotheses explaining the evolution of sociality in insects assume that positive selection drives the evolution of worker traits. Yet we know little about the extent of natural selection acting on social insects. We produced a map of positive selection for the honey bee through analysis of 40 individual genomes. We found strong evidence of positive selection acting on genes and regulatory sequences, and we discovered that mutations in worker-biased proteins tend to have greater fitness effects than mutations in queen-biased proteins. We also found many instances of positive selection acting on genes that influence worker traits, suggesting that worker phenotypes represent a major vector for adaptation in social insects. Most theories used to explain the evolution of eusociality rest upon two key assumptions: mutations affecting the phenotype of sterile workers evolve by positive selection if the resulting traits benefit fertile kin, and that worker traits provide the primary mechanism allowing social insects to adapt to their environment. Despite the common view that positive selection drives phenotypic evolution of workers, we know very little about the prevalence of positive selection acting on the genomes of eusocial insects. We mapped the footprints of positive selection in Apis mellifera through analysis of 40 individual genomes, allowing us to identify thousands of genes and regulatory sequences with signatures of adaptive evolution over multiple timescales. We found Apoidea- and Apis-specific genes to be enriched for signatures of positive selection, indicating that novel genes play a disproportionately large role in adaptive evolution of eusocial insects. Worker-biased proteins have higher signatures of adaptive evolution relative to queen-biased proteins, supporting the view that worker traits are key to adaptation. We also found genes regulating worker division of labor to be enriched for signs of positive selection. Finally, genes associated with worker behavior based on analysis of brain gene expression were highly enriched for adaptive protein and cis-regulatory evolution. Our study highlights the significant contribution of worker phenotypes to adaptive evolution in social insects, and provides a wealth of knowledge on the loci that influence fitness in honey bees.

The indigenous honey bees of Saudi Arabia (Hymenoptera, Apidae, Apis mellifera jemenitica Ruttner): Their natural history and role in beekeeping

Abstract Apis mellifera jemenitica Ruttner (= yemenitica auctorum: vide Engel 1999) has been used in apiculture throughout the Arabian Peninsula since at least 2000 BC. Existing literature demonstrates that these populations are well adapted for the harsh extremes of the region. Populations of Apis mellifera jemenitica native to Saudi Arabia are far more heat tolerant than the standard races often imported from Europe. Central Saudi Arabia has the highest summer temperatures for the Arabian Peninsula, and it is in this region where only Apis mellifera jemenitica survives, while other subspecies fail to persist. The indigenous race of Saudi Arabia differs from other subspecies in the region in some morphological, biological, and behavioral characteristics. Further taxonomic investigation, as well as molecular studies, is needed in order to confirm whether the Saudi indigenous bee populations represent a race distinct from Apis mellifera jemenitica, or merely an ecotype of this subspecies.

Nectar of Ziziphus spina-christi (L.) willd (Rhamnaceae):dynamics of secretion and potential for honey production

Abstract The nectar secretion of Ziziphus flowers was studied by removing and measuring the nectar every four hours, for two consecutive days, from 88 flowers of four trees (‘repeated sampling’). In another 120 flowers from the same trees, the accumulated sugar was measured at the end of the flowering stage. The mass of the nectar sugar was determined following the washing technique. The total amount of sugar per tree was calculated by multiplying the number of flowers per tree by the average mass of nectar sugar secreted per flower. The average mass of sugar produced per flower in repeated sampling was 0.79±0.54 mg/flower (range 0.09 - 2.48 mg). The average mass of sugar per flower for each of the four investigated trees was 1.43±0.53 mg, 0.72±0.27 mg, 0.94±0.39 mg and 0.37±0.26 mg, respectively. The differences among trees was statistically significant. For accumulated nectar, the overall average mass of sugar per flower was 0.55±0.23 mg (range 0.06 - 1.29 mg) and the average values for flowers on the investigated trees of Z. spina-christi were 0.69±0.26 mg, 0.41±0.16 mg, 0.51±0.16 mg and 0.53±0.21 mg; these variations were statistically significant. The average mass of nectar sugar calculated for the flowers with accumulated nectar sampling was significantly lower than the average mass of sugar recorded for repeated nectar sugar samplings (0.79±0.54 mg). According to this study, one Ziziphus tree is estimated to produce 3.6 kg of honey (range 2.2 - 5.2 kg), equivalent to about 900 kg of honey/ha (range 550 - 1300 kg). These figures indicate the high potential value of the plant for honey production. Nectar secretion was positively correlated with temperature, indicating the adaptation of the tree to hot climates.

The large carpenter bees of central Saudi Arabia, with notes on the biology of Xylocopa sulcatipes Maa (Hymenoptera, Apidae, Xylocopinae)

Abstract The large carpenter bees (Xylocopinae, Xylocopa Latreille) occurring in central Saudi Arabia are reviewed. Two species are recognized in the fauna, Xylocopa (Koptortosoma) aestuans (Linnaeus) and Xylocopa (Ctenoxylocopa) sulcatipes Maa. Diagnoses for and keys to the species of these prominent components of the central Saudi Arabian bee fauna are provided to aid their identification by pollination researchers active in the region. Females and males of both species are figured and biological notes provided for Xylocopa sulcatipes. Notes on the nesting biology and ecology of Xylocopa sulcatipes are appended. As in studies for this species from elsewhere, nests were found in dried stems of Calotropis procera (Aiton) (Asclepiadaceae) and Phoenix dactylifera L. (Arecaceae).

A new species of Chalicodoma from Saudi Arabia with modified facial setae (Hymenoptera, Megachilidae)

Abstract Some bees and pollen wasps have independently evolved simple, stiff, erect, apically-curved, curly or hooked facial setae as adaptations to collect pollen from nototribic flowers. A distinctive new species of Chalicodoma Lepeletier de Saint Fargeau subgenus Pseudomegachile Friese from Saudi Arabia with such morphological adaptations, Chalicodoma riyadhense sp. n., is described and figured. The species was captured visiting flowers of Blepharis ciliaris (L.) (Acanthaceae). The occurrence of modified facial setae is documented and discussed for the first time in eight other species of Pseudomegachile, and a key to the genera and subgenera of Megachilini currently confirmed for Saudi Arabia is provided.

Nectar secretion dynamics and honey production potentials of some major honey plants in Saudi Arabia

The contribution of a bee plant species to honey production depends on the plant’s nectar secretion quality and quantity, which is mainly governed by biotic and abiotic factors. The aim of the current study, was to investigate the nectar secretion dynamics and honey production potential of 14 major bee plant species of the target area. We examined the quantity and dynamics of nectar sugar per flower five times a day using a nectar sugar washing technique and direct measuring of nectar with calibrated capillary tubes. The average nectar sugar amount of the species varied from 0.41 mg/flower to 7.7 mg/flower (P < 0.0001). The honey sugar per flower was used to extrapolate the honey production potential per plant and per hectare of land. Accordingly the honey production potential of the species observed to vary from 14 kg/hectare in Otostegia fruticosa to 829 kg/hectare in Ziziphus spina-christi. The nectar secretion dynamics of the species generally showed an increasing trend early in the morning, peaking toward midday, followed by a decline but different species observed to have different peak nectar secretion times. Generally, the tree species secreted more nectar sugar/flower than the herbs. The nectar secretion amount of the species was positively correlated with the ambient temperature, indicating the adaptation of the species to hot climatic conditions. However, different species were observed to have a different optimum temperature for peak nectar secretion. Despite the limited rainfall and high temperature of the area, many plants were found to have good potential for honey production. The monetary value of honey per hectare of the studied honeybee plant species can be of equal or greater than the per-hectare monetary value of some cultivated crops that require numerous inputs. In addition, the information generated is believed to be useful in apiary site selection and to estimate the honey bee colony carrying capacity of an area.

Nesting Biology of the Leafcutting Bee Megachile minutissima (Hymenoptera: Megachilidae) in Central Saudi Arabia

ABSTRACT The leafcutting bee Megachile (Eutricharaea) minutissima Radoszkowski is a widely distributed species in the Middle East and a promising pollinator of alfalfa. We provide information on the nest architecture, foraging behavior, phenology, and host plants of a wild population of M. minutissima studied between March 2010 and September 2012 in Amariah, a typical desert in central Saudi Arabia. Bees nested in preexisting cavities in the sandy, dry, and loose soil, and built between 2 and 14 leaf-lined brood cells per nest. Females built and provisioned 1–2 cells per day, each consisting of a large oval piece from which the cell cup was made and a small semiround piece that was used as cell cap; however, occasionally small oval pieces were also used in the latter. Cells were built from leaves of Ricinus communis L. (Euphorbiaceae), a locally abundant plant. Both sexes were captured from March to October at flowers of 11 species (10 families), indicating some degree of polylecty as well as either bivoltinism or multivoltinism. We also provide comparative taxonomie comments that will assist bee researchers to easily recognize this species.

Allodapine Bees in the Arabian Peninsula (Hymenoptera: Apidae): A New Species of Braunsapis from the Sarawat Mountains, with an Overview of the Arabian Fauna

ABSTRACT An interesting new species of allodapine bee (Xylocopinae: Allodapini: Allodapina) is described and figured from males and females captured in the Sarawat Mountains near al-Baha, representing the first records of the tribe for Saudi Arabia. Braunsapis alqarnii Engel and Michener, new species, is similar to the small species of the genus known from Africa and Madagascar but is distinguished on the basis of several features, most notably the male hind legs and terminalia. Notes are provided on the known allodapine fauna of the Arabian Peninsula, with a key to the species.

A new wild, pollinating bee species of the genus Tetraloniella from the Arabian Peninsula (Hymenoptera, Apidae)

Abstract A new species of the eucerine bee genus Tetraloniella Ashmead (Apinae: Eucerini) is described and figured from central Saudi Arabia and Qatar. Tetraloniella (Tetraloniella) persiciformis sp. n. is distinguished on the basis of coloration, integumental sculpturing, male metafemoral structure, and male terminalia. A floral record of Pulicaria undulata (L.) C.A. Mey. (Compositae) is noted for some of the material. Females superficially resemble those of Tarsalia persica (Warncke) (Ancylaini) in overall coloration but can be distinguished by the typical generic and tribal characters.

Systropha androsthenes in Saudi Arabia (Hymenoptera: Halictidae)

The rophitine bee genus Systropha Illiger (Rophitinae: Rophitini) is a distinctive element of the Old World halictid fauna. The genus comprises 28 species (Patiny and Michez, 2006, 2007; Eardley and Urban, 2006) distributed from Spain and Morocco in the west to westernmost China in the East (e.g., Niu et al., 2005), and from Germany in the north to South Africa in the south. Most floral records suggest that many species of Systropha are specialists on Convolvulaceae, particularly Convolvulus L. although some visit other genera in the family such as Merremia Dennst. ex Endl., Calystegia R. Br., and Ipomoea L., carrying abundant loads of pollen all over the body in addition to the metatibial scopa. The biology and immature stages of Systropha have been described by Malyshev (1925), Batra and Michener (1966), Grozdanić and Mučalica (1966), Grozdanić and Vasić (1968), Fraberger and Ayasse (2007), and Rozen and Özbek (2008). Herein we provide the first formal record of Systropha for Saudi Arabia, and expand the currently documented distribution of S. androsthenes from Oman and the United Arab Emirates (Baker, 1996; Patiny and Michez, 2006) further in the Arabian Peninsula. The species was captured at flowers of Convolvulus arvensis L., known locally as Ullaique.