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== Effect of pesticide exposure on ''B. terrestris'' == |
== Effect of pesticide exposure on ''B. terrestris'' == |
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In their 2014 study published in ''[[Functional Ecology]]'' researchers using Radio-Frequency Identification (RFID) tagging technology on the bees, found that a sublethal exposure to either a [[neonicotinoid]] ([[imidacloprid]]) and/or a [[pyrethroid]] (?-[[cyhalothrin]]) over a four-week period caused an impairment of the bumble bee's ability to [[forage]].<ref name="Gill_Raine_2014">{{cite journal |journal=Functional Ecology |title=Chronic impairment of bumblebee natural foraging behaviour induced by sublethal pesticide exposure |first1=Richard J. |last1=Gill |first2=Nigel E. |last2=Raine |date=7 July 2014 |accessdate=4 October 2014 |doi=10.1111/1365-2435.12292 }}</ref> |
In their 2014 study published in ''[[Functional Ecology]]'' researchers using Radio-Frequency Identification (RFID) tagging technology on the bees, found that a sublethal exposure to either a [[neonicotinoid]] ([[imidacloprid]]) and/or a [[pyrethroid]] (?-[[cyhalothrin]]) over a four-week period caused an impairment of the bumble bee's ability to [[forage]].<ref name="Gill_Raine_2014">{{cite journal |journal=Functional Ecology |title=Chronic impairment of bumblebee natural foraging behaviour induced by sublethal pesticide exposure |first1=Richard J. |last1=Gill |first2=Nigel E. |last2=Raine |date=7 July 2014 |accessdate=4 October 2014 |doi=10.1111/1365-2435.12292 }}</ref> Research published in 2015 showed that bees prefer solutions containing neonicotinoids, even though the consumption of these pesticides caused them to eat less food overall. This work implies that treating flowering crops with such pesticides presents a sizeable hazard to foraging bees.<ref name="Neonicotinoids">{{cite journal|last=Kessler|first=Sebastien C|coauthors=et al|date=7 May 2015|title=Bees prefer foods containing neonicotinoid pesticides|journal=Nature|publisher=Macmillan Publishing Ltd|volume=521|pages= 74–76|issn= 0028-0836|url=http://www.nature.com/nature/journal/v521/n7550/full/nature14414.html}}</ref> |
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==Environmental concerns== |
==Environmental concerns== |
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Revision as of 09:36, 24 September 2015
| Bombus terrestris | |
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| Species: | B. terrestris
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| Bombus terrestris | |
Bombus terrestris, the buff-tailed bumblebee or large earth bumblebee is one of the most numerous bumblebee species in Europe. Bombus terrestris is the largest of the bumblebee species.[1] Bombus terrestris is one of the main species used in greenhouse pollination, and consequently can be found in many countries and areas where it is not native; Tasmania for example [2] It is a eusocial insect that is characterized by unique Hymenopteran sex ratios, where male drones dominate most colonies. The queen of B. terrestris is often highly dominant over her colony and exhibits behaviors such as altering the sex ratio in her favor over the workers and controlling queen larval development with pheromones. However, after aggression breaks out in the nest, the workers can usually gain control and restart the colony cycle. Interestingly, the queen is monandrous and only mates with one male after leaving the nest, despite the potential genetic benefits from polyandrous mating. B. terrestris demonstrates interesting learning tactics with flower color and alloethism in foraging behaviors. They have also been implicated in a number of bee pathology studies.
Taxonomy and Phylogenetics
B. terrestris is part of the order Hymenoptera, which is composed of ants, bees, wasps, and sawflies and the family Apidae, which specifically consists of bees. It is also part of the subfamily Apinae, which includes most species of bees within the family. It is in the genus Bombus, which includes all of the bumblebees. There are two documented subspecies: Bombus terrestris terrestris and Bombus terrestris sassaricus. [3] Two closely related species, B. canariensis and B. maderensis, are thought to have evolved from European B. terrestris strains and then diverged on the Canary Islands and Maderia respectively. [4]
Description and Identification
B. terrestris are pollen-storing bees that generally feed and forage on nectar and pollen. [5] These bees can navigate their way back to the nest from a distance as far away as 13 km (8.1 mi), although most forage within 5 km of their nest.[6] The queen is 2.0–2.7 cm long, while the workers are 1.5–2.0 cm. The latter are characterized by their white-ended abdomens and look (apart from their yellowish bands being darker in direct comparison) just like those of the white-tailed bumblebee, B. lucorum, a close relative. The queens of B. terrestris have the namesake buff-white abdomen ("tail") tip; this area is white like in the workers in B. lucorum. B. terrestris are unique compared to other bees in that their caste of workers exhibits a wide variation in worker size with thorax sizes ranging from 2.3 to 6.9 mm and masses ranging from 68 to 754 mg. [5]
Distribution and Habitat
B. terrestris is most commonly found throughout Europe and generally occupies temperate climates. Though it can survive in a wide variety of habitats and there are populations in the near East, the Mediterranean Islands, and Northern Africa as well. [4] They form comb like nest structures with eggcells, each containing several eggs. The queen will layer these eggcells on top of one another. Colonies produce between 300-400 bees on average. [3]
Colony Cycle
The first bumblebees to be seen in spring are the queens; only the queen hibernates through the winter. The queen is much bigger than the workers, which appear later. As soon as the queen has found some nectar, to replenish her energy reserves, she starts looking for a suitable site to build her nest.
The queen then lays a small batch of diploid eggs to begin with. Once these hatch, she tends the larvae, feeding them with nectar and pollen. When the larvae are grown, they pupate, and about two weeks later, the first worker bumblebees emerge. This is known at the initiation phase of the colony. [3] Workers will forage for nectar and pollen for the colony, and tend later generations of larvae. The workers are smaller than the queen, and only live for a few weeks. The foraging range and frequency of workers depends on the quality and distribution of available food, but most workers forage within a few hundred meters of their nest. [7]
This first phase can lasts a variable amount of time in B. terrestris, after which the switch point is reached, when the queen begins to lay some unfertilized eggs, which develop into male bees. [3] When the male drones emerge from the nest, they do not return, foraging only for themselves. They seek out new queens and mate with them. Remaining diploid eggs receive extra food and pupate to become new queens, though with pheromones the queen can control to some extent against the workers' inclination to invest more in larvae around this time, to ensure that not too many become queens. The colony persists until the competition point is reached, when workers begin egg laying and outright aggression between workers and between the worker and the queen begins. This is a very predictable point that occurs at about 30 days. [3]
Usually the worker-queen conflict will force the queen out and the new workers will become queenless. A "false queen" might take control of the colony for a short period. [8] The colony cycle starts again when the newly hatched queens leave the nest in search of a mate and a nest for themselves to start a new colony.
Reproduction
Mating System
B. terrestris is thought to be a mainly singly mating species. This is unusual for social insect queens where mating with several males (polyandry) has been shown to have several benefits. The lack of multiple mating by B. terrestris queens may be partly caused by male interference in the process. B. terrestris males plug the female's sexual tract with a sticky secretion during mating which appears to reduce the female's ability to successfully mate with other males for several days.[9] While there may be genetic fitness benefits in colony heterogeneity from a polyandrous mating system, bumblebees are also likely monandrous due to social constraints and risks associated with multiple matings. Finding multiple mates might be energetically costly and expose the queen to higher predation risks. Additionally, while queens may prefer multiple matings to ensure more genetic variability and viable offspring, the queen-worker conflict dictates that workers will be more apt to raise larvae from one male. [10] This is due to haplodiploidy in Hymenopteran social insects in which males (drones) are haploid and females (workers and queens) are diploid. This confers greater genetic similarity between sister workers (75%) than between mother and offspring (50%), making kin selection stronger between sisters. This selective force would be reduced if workers were the offspring of multiple males, which might lead to increased conflict in the nest.
Sex Ratios
Due to the variability in switch point amount B. terrestris colonies, there are varying levels of sex ratios among nests. Early switching colonies have a much larger number of males (17.4:1), which may give them a competitive advantage in mating with later emerging queens. Late switching colonies have fewer males and a more even sex ratio of 1.3:1, thus indicating the queen's control over her colony as she would prefer a 1:1 ratio since she is equally related to both sons and daughters. On the other hand, workers would prefer a 1:3 ratio as they are more related to each other than their mother. Even though early and late switching colonies are usually balanced in the population, the overall demographic is still male biased. This creates an overall sex ratio of 4:1, males to females. [3] This is unusual for social insects, which usually have a 1:3 sex ratio indicative of worker colony control.
Reproductive Suppression
Queen bees can control oogenesis in worker bees via juvenile hormone (JH), which regulates egg development. In queenless in B. terrestris workers, the corpus allata, which secretes JH, was noticeably enlarged compared to queenright workers. JH concentrations were also higher the hemolymph of queenless workers. [11]This suggests that the presence of a queen is enough to prevent workers from laying eggs, which helps her maintain genetic control over her colony's brood. The mechanism through which the queen induces this behavior is likely through pheromones.
Behavior
Dominance Hierarchy
Workers start out at the bottom of the dominance hierarchy in the social colony. As they age, they move up closer to the position of the queen. Queen-side workers are often egg layers and interact more frequently with the queen. This social position may pay later after the competition point is reached. When the queen is overthrown by the aggression of the workers, likely the most dominant worker will have the best likelihood of contributing more eggs to the colony brood and perhaps climb to the position of “false queen.” The queen appears to maintain a constant distance of social dominance from her workers at all points in the cycle, suggesting that she is displaced from the sheer number of workers later in the cycle. [8]
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Foraging Behavior
B. terrestris bees exhibit alloethism in foraging behavior, where larger bees are more often found foraging outside the nest and will return to the nest with larger amounts of nectar and pollen. It is possible that larger bees might be able to withstand greater temperature variation, avoid predation, and travel larger distances making them selectively advantageous. Distinct social roles based on morphology might be beneficial for individuals of the colonies, by making the colony run more efficiency. Small bees can be reared more cheaply and kept for in-nest tasks, while only some larvae will be fed enough to become large foraging bees. [5]
Learning
Bumblebees and honeybees are extremely influenced by innate preferences for blue and yellow color. When they have no previous training they will often just visit flowers that naturally attract them. However, it is generally thought that bees will learn to visit more nectar rewarding flowers after experience associates the reward with the color of the petals. This has been demonstrated in B. terrestris where bees trained on artificially colored flowers will pick a similar color to the one they were trained with when tested with an array of flower choices. [12]
Disease
Effects of Foraging on Resistance
Foraging is considered energetically costly and it is possible that individuals that spend more time foraging suffer costs to their overall fitness. For example, B. terrestris is often vulnerable to parasitism by conopid flies in Central Europe and it has been hypothesized that foragers might suffer higher incidences of parasites due to the increased metabolic costs of flying. This was demonstrated in a population in which foraging workers had significantly lower levels of encapsulation of an experimental parasitic egg when compared to non-foraging workers. This suggests that foragers have compromised immune systems due increased energetic expenses and might be predisposed to fly parasites. [13]
Effects of Polyandry on Resistance
While B. terrestris is a singly mating species, it might be beneficial to mate with multiple males in a polyandrous system to attain greater genetic variability for resistance against disease. However, artificially increasing the number of mates a B. terrestris queen obtains through artificial insemination has shown that the increased genetic variability in her offspring confers greater resistance to the most common bumblebee parasite, Crithidia bombi. [10] However, the average reproductive success between one and multiple matings is not linear. Queens that mated once and mated four times had a higher fitness than those that mated twice. [10] This suggests that there might be a barrier to increasing matings, which might be why colonies are usually monandrous.
Threats from Disease
Deformed wing virus (DMV) is normally a honeybee pathogen that results in reduced and crumpled wings, making those individuals inviable. This virus is thought to have spread to B. terrestris and in 2004 as many as 10% of queen bees bred commercially in Europe were found dead with deformed wings. This was confirmed when B. terrestris colonies tested positive for DMV RNA. This could be a broad range pathogen among bees or perhaps it has been infecting new hosts recently after transmission from honeybees. [14]
Domestication
Since 1987, B. terrestris has been bred commercially for use as a pollinator for European greenhouse crops, particularly tomatoes — a task which was previously carried out by human hand.[15][16] B. terrestris has been commercially reared in New Zealand since the early 1990s[17][18] and is now used in at least North Africa, Japan, Korea, and Russia, with the global trade in bumblebee colonies probably exceeding 1 million nests per year.[19]
Effect of pesticide exposure on B. terrestris
In their 2014 study published in Functional Ecology researchers using Radio-Frequency Identification (RFID) tagging technology on the bees, found that a sublethal exposure to either a neonicotinoid (imidacloprid) and/or a pyrethroid (?-cyhalothrin) over a four-week period caused an impairment of the bumble bee's ability to forage.[20] Research published in 2015 showed that bees prefer solutions containing neonicotinoids, even though the consumption of these pesticides caused them to eat less food overall. This work implies that treating flowering crops with such pesticides presents a sizeable hazard to foraging bees.[21]
Environmental concerns
In 2008, the Australian government banned the live import of B. terrestris into Australia on the grounds that it would present a significant risk of becoming a feral species and thereby present a threat to native fauna and flora.[22] In 2004, this bumblebee was classified as a 'Key Threatening Process' by the Scientific Committee of the New South Wales Department of Environment.[23] It is also classified as an "invasive alien species" in Japan.[16]
This species was introduced to Chile in 1998. It has crossed into Argentina, and is spreading at about 275 km per year. Where it occurs, the only bumblebee native to southern South America, Bombus dahlbomii, disappears within weeks. The previously introduced (1982) Bombus ruderatus is also seriously affected. The cause is thought to be the parasite Apicystis bombi, an organism carried by the buff-tails, but which has no adverse effect on that species.[24]
References
- ^ Bumblebee species, retrieved 4 October 2014
- ^ Semmens, T.D., E. Turner, and R. Buttermore. (1993). "Bombus terrestris (L.) (Hymenoptera: Apidae) now established in Tasmania". Australian Journal of Entomology. 32 (4): 346.
{{cite journal}}: CS1 maint: multiple names: authors list (link) - ^ a b c d e f Duchateau, M. J. and H. H. W. Velthuis (1988). "Development and reproductive strategies in Bombus terrestris colonies". Behavior. 107: 186–207.
- ^ a b 10. Widmer, A., P. Schmid-Hempel, and A. Estoup, and A. Scholl (1998). "Population genetic structure and colonization history of Bombus terrestris s.l. (Hymenoptera: Apidae) from the Canary Islands and Madeira". Heredity. 81: 563–572.
{{cite journal}}: horizontal tab character in|author=at position 4 (help)CS1 maint: multiple names: authors list (link) CS1 maint: numeric names: authors list (link) - ^ a b c Goulson, D., J. Peat, J. C. Stout, J. Tucker, B. Darvill, L. C. Derwent, and W. O. H. Hughes (2002). "Can alloethism in workers of the bumblebee, Bombus terrestris, be explained in terms of foraging efficiency?". Animal Behaviour. 64: 123–130.
{{cite journal}}: CS1 maint: multiple names: authors list (link) - ^ Louisa Cheung (July 26, 2006). "Homing instinct of bees surprises". BBC News.
- ^ Stephan Wolf & Robin F. A. Moritz (2008). "Foraging distance in Bombus terrestris L. (Hymenoptera: Apidae)". Apidologie. 39 (4). EDP Sciences: 419–427. doi:10.1051/apido:2008020.
- ^ a b van Honk, C. and P. Hogeweg (1981). "The ontogeny of the social structure in a captive Bombus terrestris colony". Behavioral Ecology and Sociobiology. 9 (2): 111–119.
- ^ Annette Sauter, Mark J. F. Brown, Boris Baer & Paul Schmid-Hempel (2001). "Males of social insects can prevent queens from multiple mating". Proceedings of the Royal Society B. 268 (1475): 1449–1454. doi:10.1098/rspb.2001.1680. PMC 1088762. PMID 11454287.
{{cite journal}}: CS1 maint: multiple names: authors list (link) - ^ a b c Baer, B. and P. Schmid-Hempel (2001). "Unexpected consequences of polyandry for parasitism and fitness in the bumblebee, Bombus terrestris". Evolution. 55 (8): 1639–1643.
- ^ Roseler, P. F. (1977). "Juvenile hormone control of oogenesis in bumblebee workers, B. terrestris". Journal of Insect Physiology. 23: 985–992.
- ^ Gumbert, A (2000). "Color choices by bumble bees (Bombus terrestris): Innate preferences and generalization after learning". Behavioral Ecology and Sociobiology. 48 (1): 36–43.
- ^ Konig, C. and P. Schmid-Hempel (1995). "Foraging and immunocompetence in workers of the bumblebee, Bombus terrestris L.". Proceedings of the Royal Society of London B. 260: 225–227.
- ^ Genersch, E., C. Yue, I. Fries, J. R. de Miranda (2006). "Detection of Deformed wing virus, a honey bee viral pathogen, in bumble bees (Bombus terrestris and Bombus pascuorum) with wing deformities". Journal of Insect Pathology. 91: 61–63.
{{cite journal}}: CS1 maint: multiple names: authors list (link) - ^ Anon. "Natural pollination". Koppert Biological Systems. Koppert B.V. Retrieved 18 September 2011.
- ^ a b Matsumura, Chizuru; Jun Yokoyama; Izumi Wasitani (August 2004). "Invasion Status and Potential Ecological Impacts of an Invasive Alien Bumblebee, Bombus terrestris L. (Hymenoptera: Apidae) Naturalized in Southern Hokkaido, Japan" (PDF). Global Environmental Research. AIRIES: 51–66.
- ^ Velthuis, H. H. W. and van Doorn, A. (April 2004) 'The breeding, commercialization and economic value of bumblebees.' in B. M. Freitas and J. O. P. Pereira (eds) Solitary Bees Conservation, Rearing and Management for Pollination. Federal University of Ceara, Brasil, pp. 135-149
- ^ http://biobees.co.nz/biology.html
- ^ Dave Goulson (2010). "Bumblebees. Behaviour, Ecology and Conservation" Oxford University Press.
- ^ Gill, Richard J.; Raine, Nigel E. (7 July 2014). "Chronic impairment of bumblebee natural foraging behaviour induced by sublethal pesticide exposure". Functional Ecology. doi:10.1111/1365-2435.12292.
{{cite journal}}:|access-date=requires|url=(help) - ^ Kessler, Sebastien C (7 May 2015). "Bees prefer foods containing neonicotinoid pesticides". Nature. 521. Macmillan Publishing Ltd: 74–76. ISSN 0028-0836.
{{cite journal}}: Unknown parameter|coauthors=ignored (|author=suggested) (help) - ^ "Bumblebee rejected for live import". Australian Government. 26 October 2008. Retrieved 1 January 2009.
{{cite web}}: Cite has empty unknown parameter:|coauthors=(help) - ^ Paul Adam (February 2004). "Introduction of the large earth bumblebee, Bombus terrestris - key threatening process listing". NSW Government. Retrieved 1 January 2009.
{{cite web}}: Cite has empty unknown parameter:|coauthors=(help) - ^ Goulson, Dave (2013). "Argentinian invasion!". Buzzword. 21: 17–18.
External links
- What Harm Could Exotic Bumblebees Do in Australia? - a report by Australian Native Bee Research Centre