''Bombus ruderatus'', the large garden bumblebee or ruderal bumblebee, is a species of long-tongued
bumblebee
A bumblebee (or bumble bee, bumble-bee, or humble-bee) is any of over 250 species in the genus ''Bombus'', part of Apidae, one of the bee families. This genus is the only extant group in the tribe Bombini, though a few extinct related genera ...
found in Europe and in some parts of northern Africa.
This species is the largest bumblebee in Britain and it uses its long face and tongue to pollinate hard-to-reach tubed flowers. Bumblebees are key pollinators in many agricultural ecosystems, which has led to ''B. ruderatus'' and other bumblebees being commercially bred and introduced into non-native countries, specifically
New Zealand
New Zealand ( mi, Aotearoa ) is an island country in the southwestern Pacific Ocean. It consists of two main landmasses—the North Island () and the South Island ()—and over 700 smaller islands. It is the sixth-largest island count ...
and
Chile
Chile, officially the Republic of Chile, is a country in the western part of South America. It is the southernmost country in the world, and the closest to Antarctica, occupying a long and narrow strip of land between the Andes to the east a ...
.
Since its introduction in Chile, ''B. ruderatus'' has spread into
Argentina
Argentina (), officially the Argentine Republic ( es, link=no, República Argentina), is a country in the southern half of South America. Argentina covers an area of , making it the second-largest country in South America after Brazil, th ...
as well.
Population numbers have been declining and it has been placed on the Biodiversity Action Plan to help counteract these declines.
Taxonomy and phylogeny
''Bombus ruderatus'' is part of the order
Hymenoptera and the family
Apidae
Apidae is the largest family within the superfamily Apoidea, containing at least 5700 species of bees. The family includes some of the most commonly seen bees, including bumblebees and honey bees, but also includes stingless bees (also used for ...
. ''B. ruderatus'' is in the genus
Bombus
A bumblebee (or bumble bee, bumble-bee, or humble-bee) is any of over 250 species in the genus ''Bombus'', part of Apidae, one of the bee families. This genus is the only extant group in the tribe Bombini, though a few extinct related gener ...
and is one of 239 species of bumblebees, with 23 of those existing in Britain alone.
''B. ruderatus'' is part of the subgenus
Megabombus
The list presented here is a checklist of world bumblebees (Tribe Bombini) based on the ''Bombus'' phylogeny presented by Cameron ''et al'' (2007) and grouped by subgenus following the revision of Williams ''et al'' (2008). The bumblebee fossil rec ...
, along with ''
Bombus hortorum
''Bombus hortorum'', the garden bumblebee or small garden bumblebee, is a species of bumblebee found in most of Europe north to 70°N, as well as parts of Asia and New Zealand. It is distinguished from most other bumblebees by its long tongue ...
''.
''B. ruderatus'' is most closely related to ''B. hortorum''.
Description and identification
The body lengths of ''B. ruderatus'' reach about in queens, in workers and in males. It has a long face and tongue, which is well adapted for feeding on long-tubed flowers. The basic color of the body is black with two yellow bands on its mesonoma—one on its scutellum and one on its
pronotum
The prothorax is the foremost of the three segments in the thorax of an insect, and bears the first pair of legs. Its principal sclerites (exoskeletal plates) are the pronotum ( dorsal), the prosternum (ventral), and the propleuron (lateral) on e ...
—and a single thin yellow band on the
abdomen
The abdomen (colloquially called the belly, tummy, midriff, tucky or stomach) is the part of the body between the thorax (chest) and pelvis, in humans and in other vertebrates. The abdomen is the front part of the abdominal segment of the to ...
.
A black band is located on the interwing and separates the two yellow bands on the
thorax
The thorax or chest is a part of the anatomy of humans, mammals, and other tetrapod animals located between the neck and the abdomen. In insects, crustaceans, and the extinct trilobites, the thorax is one of the three main divisions of the cre ...
.
Similarly, queens are the most difficult to find as the bee is scarce in many areas and queens are less abundant within a colony itself.
Similarities with ''Bombus hortorum''
There are many similarities between ''B. ruderatus'' and ''B. hortorum'', making it difficult to distinguish between the two species.
Due to numerous physical similarities, many scientists have suggested reassessing their current status as two distinct species.
Both bees are similar sizes, are black with two yellow bands, and the drones have similar genitalia.
Although they may be hard to assess at first glance, there are minor physical differences. For example, the width of two yellow bands on the scutellum and pronotum are relatively equal in ''B. ruderatus'', while in ''B. hortorum'', the band on the scutellum tends to be narrower than the band on the pronotum.
Physical variations may exist within a species as well, making it important to use other sources to distinguish between the two species.
Studies of mitochondrial
DNA has shown a 6.2% divergence for
COII and a 9.2% divergence for
cytochrome b
Cytochrome b within both molecular and cell biology, is a protein found in the mitochondria of eukaryotic cells. It functions as part of the electron transport chain and is the main subunit of transmembrane cytochrome bc1 and b6f complexes.
F ...
.
These percentages are higher than the divergences between other distinct species, affirming that these bees are in fact two distinct species.
Nests
Most ''Bombus ruderatus'' nests tend to be subterranean. Queens have been seen to return to their maternal nest site, but will assess it indiscriminately to determine if it is suitable for colonization.
Distribution and habitat
''Bombus ruderatus'' is naturally found in Europe and north Africa, favoring large flower-rich areas of meadowland that support numerous species of plants with long-corolla flowers.
[MacFarlane, R.P.; Gurr, L. 1995. Distribution of bumble bees in New Zealand. New Zealand Entomologist 18: 29-36.] It is vital that pollen and
nectar sources are available within foraging distance of nests from April to September. Specifically in Europe, this species is present in Austria, Belgium, Great Britain, the Czech Republic, Denmark, France, Germany, Italy, Poland, Romania, Spain, and Switzerland.
Since the 1800s it has been used commercially in non-native countries to assist with crop pollination.
In 1885, ''B. ruderatus'' was introduced into New Zealand to pollinate the red clover plant, and in 1982, it was introduced into Chile for the same purpose.
Since 1993, this species has also been seen in Argentina’s
Patagonia
Patagonia () refers to a geographical region that encompasses the southern end of South America, governed by Argentina and Chile. The region comprises the southern section of the Andes Mountains with lakes, fjords, temperate rainforests, and g ...
, thought to have traveled there through the low-altitude sections of the Andes. Many parts of the world, including western Europe and North America, have seen declining populations of their native bumblebees due to many contributing factors.
In Britain specifically,
habitat fragmentation has led to declines in ''B. ruderatus'', in both population size and pollination range.
''B. ruderatus'' is commonly found in
sympatric distribution with ''B. hortorum'', but the latter has seemed to be unaffected by fragmentation, since it is still relatively commonly in Britain.
Conversely, ''B. ruderatus'' has become one of the most rare of the 23 English bumblebees.
Worker-Queen conflict
Biased sex ratio
In New Zealand, colonies started by natural queens of ''Bombus ruderatus'' tended to have a male-biased sex ratio.
Additionally, the two sexes emerged at different times, with males usually emerging before new queens.
Male-biased sex ratios tend to occur when queens have multiple mates.
Larva ejection
In ''Bombus ruderatus'', worker
oviposition has been seen in association with
oophagy
Oophagy ( ) sometimes ovophagy, literally "egg eating", is the practice of
embryos feeding on eggs produced by the ovary while still inside the mother's uterus. The word oophagy is formed from the classical Greek (, "egg") and classical Greek (, ...
, which may include the queen eating eggs deposited by workers.
Larvae ejection was also a common process done by workers and sometimes queens, and involved pulling live larvae out of cells and depositing them outside of the nest.
Analysis of ejected and survivor larvae showed no morphological difference so the reason for ejection is unknown, but female ejection occurred more frequently than male ejection.
Diet
In Argentina, ''Bombus ruderatus'' is most commonly found feeding from plant species from families
Fabaceae,
Alstroemeriaceae
Alstroemeriaceae is a family of flowering plants, with 254 known species in four genera (Christenhusz & Byng 2016 ), almost entirely native to the Americas, from Central America to southern South America. One species of '' Luzuriaga'' occurs in ...
, and
Rosaceae.
Newly emergent queens tend to consume more pollen than the much smaller males.
Parasites
''
Apicystis bombi
''Apicystis bombi'' is a species of parasitic alveolates in the phylum Apicomplexa. It infects bees, especially bumblebees. It is believed to have a cosmopolitan distribution in bumblebees and a sporadic occurrence in honey bees, and causes dise ...
'', a pathogenic protozoan, has been recently found in ''Bombus ruderatus'' species in Argentina.
''Apicystis bombi'' can have many negative effects in bee populations due to it high virulence, its generalism for many different bumblebee species, and its ability to affect both commercially produced and native born colonies.
''Apicystis bombi'' can cause extreme physical and behavior effects within colonies, along with inhibiting colony foundation, both of which increase mortality.
This parasite is thought to have been contracted in ''B. ruderatus'' due to the interaction with another invasive species, ''
Bombus terrestris
''Bombus terrestris'', the buff-tailed bumblebee or large earth bumblebee, is one of the most numerous bumblebee species in Europe. It is one of the main species used in greenhouse pollination, and so can be found in many countries and areas wher ...
''.
''B. terrestris'' was introduced in Argentina in 2006, and before this time, ''Apicystis bombi'' had not been found in any native or invasive species of bee.
The spread of parasites can happen through a process known as pathogen spillover, which may be a contributing factor to the declining bumblebee populations. This has been seen to occur in commercial trading when invasive species pass parasites or illnesses to native species, like in the situation with ''B. terrestris.''
Human importance
Agricultural importance
Bumblebees are important
pollinators
A pollinator is an animal that moves pollen from the male anther of a flower to the female stigma of a flower. This helps to bring about fertilization of the ovules in the flower by the male gametes from the pollen grains.
Insects are the maj ...
of crops and flowers, some of which are important for economic and agricultural reasons.
Bumblebees tend to be more effective pollinators than
honeybees since they can fly at lower temperatures.
Honeybee pollination has been seen to decrease as the season progresses due to decreasing temperatures, while pollination of bumblebees usually remains relatively constant.
In 1982, ''Bombus ruderatus'' was brought to
Chile
Chile, officially the Republic of Chile, is a country in the western part of South America. It is the southernmost country in the world, and the closest to Antarctica, occupying a long and narrow strip of land between the Andes to the east a ...
to be used as a pollinator of the
red clover
''Trifolium pratense'', the red clover, is a herbaceous species of flowering plant in the bean family Fabaceae, native to Europe, Western Asia, and northwest Africa, but planted and naturalized in many other regions.
Description
Red clove ...
, which is a small legume used for its seeds.
Chile is an important exporter in red clover seeds and thus their agricultural and economic success may depend on the effectiveness of bee pollination.
Most pollination of red clover is done by honeybees, but their pollination decreases in late summer to early fall, leading to less seed recovery.
''B. ruderatus'' was introduced in order to compensate for late season decreases in pollination. Although there have been positive agricultural benefits from increased seed production, negative consequences, in terms of decreased native populations have been observed as well.
Effects of invasion into non-native countries
Invasive species may be very harmful to native species by outcompeting them for resources or by passing illnesses through pathogen spillover.
For example, the introduction of ''Bombus ruderatus'' and ''Bombus terrestris'' in Argentina have been shown to decrease the population of the native species, ''
Bombus dahlbomii
''Bombus dahlbomii'', also known as the moscardón, is a species of bumblebee endemic to southern South American temperate forests. ''B. dahlbomii'' is one of the largest bee species in the world, with matured queens growing up to long.King, A. ...
''.
This can be seen in the comparison of the visitation frequency of the two species. Since the introduction of ''B. ruderatus'', the visitation frequency of ''
Bombus dahlbomii
''Bombus dahlbomii'', also known as the moscardón, is a species of bumblebee endemic to southern South American temperate forests. ''B. dahlbomii'' is one of the largest bee species in the world, with matured queens growing up to long.King, A. ...
'' to certain plants has decreased, while it has increased in ''B. ruderatus''.
Although a large part of the decline of ''Bombus dahlbomii'' populations in southern South America could be due to the introduction of ''Apicystis bombi'' by ''B. terrestris'', resource and foraging competition with ''B. ruderatus'' has further facilitated the decline of the native ''
Bombus dahlbomii
''Bombus dahlbomii'', also known as the moscardón, is a species of bumblebee endemic to southern South American temperate forests. ''B. dahlbomii'' is one of the largest bee species in the world, with matured queens growing up to long.King, A. ...
''.
In general, ''B. dahlbomii'' tends to be more successful in areas where ''B. ruderatus'' or ''B. terrestris'' has not yet colonized.
Declines in ''B. ruderatus'' and other bumblebee populations
In recent years, many countries have seen decreases in bee populations, specifically bumblebees. Some possible explanations could include
habitat fragmentation,
climate change
In common usage, climate change describes global warming—the ongoing increase in global average temperature—and its effects on Earth's climate system. Climate change in a broader sense also includes previous long-term changes to ...
,
disease
A disease is a particular abnormal condition that negatively affects the structure or function of all or part of an organism, and that is not immediately due to any external injury. Diseases are often known to be medical conditions that a ...
,
agrochemicals, and other factors.
As stated previously, ''B. ruderatus'' has seen a population decline in Britain and has disappeared completely from many of its previous sites.
Declines in bee populations can lead to other ecological issues, such as declines in the success of plant species that rely on their pollination.
Counteracting declining bee populations
Recently, the
European Union
The European Union (EU) is a supranational political and economic union of member states that are located primarily in Europe. The union has a total area of and an estimated total population of about 447million. The EU has often been de ...
has introduced agri-environment plans that can be used to pay farmers to manage their land in a way that benefits bee species.
Britain adopted the
Environmental Stewardship scheme with the goal of enhancing the supply of pollen and nectar sources for bumblebees.
These plans hope to counteract some of the issues that commercial developments have caused. For example, intense crop management with decreased mixed farming has led to “botanical simplification” of habitats, which may have contributed to decreased bumblebee populations by decreasing the quality and quantity of resources and habitats.
Photos of ''B. ruderatus''
File:Hibiscus syriacus Bombus ruderatus 1 Luc Viatour.jpg , ''B. ruderatus'' on ''Hibiscus syriacus''
References
External links
BiolibFauna europaeaNational ArchivesArkive.org
{{Taxonbar, from=Q263784
Bumblebees
Hymenoptera of Africa
Hymenoptera of Europe
Insects of North Africa
Insects described in 1775
Taxa named by Johan Christian Fabricius
Hymenoptera of New Zealand