
''Xylocopa darwini'', the Galápagos carpenter bee, is the only native species of
bee
Bees are winged insects closely related to wasps and ants, known for their roles in pollination and, in the case of the best-known bee species, the western honey bee, for producing honey. Bees are a monophyletic lineage within the superfamil ...
in the
Galápagos Islands
The Galápagos Islands () are an archipelago of volcanic islands in the Eastern Pacific, located around the equator, west of the mainland of South America. They form the Galápagos Province of the Republic of Ecuador, with a population of sli ...
, to which it is
endemic
Endemism is the state of a species being found only in a single defined geographic location, such as an island, state, nation, country or other defined zone; organisms that are indigenous to a place are not endemic to it if they are also foun ...
. Altogether, only three species of bee are found in the islands.
[ This species is found on 75% of the largest islands. It is ]sexually dimorphic
Sexual dimorphism is the condition where sexes of the same species exhibit different Morphology (biology), morphological characteristics, including characteristics not directly involved in reproduction. The condition occurs in most dioecy, di ...
and is known for its complex behavior. As the only native bee, ''Xylocopa darwini'' serves as an important primary pollinator
A pollinator is an animal that moves pollen from the male anther of a flower to the female carpel, 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 ...
within the plant-pollinator network of the archipelago
An archipelago ( ), sometimes called an island group or island chain, is a chain, cluster, or collection of islands. An archipelago may be in an ocean, a sea, or a smaller body of water. Example archipelagos include the Aegean Islands (the o ...
.
Description
The leaf-cutter bee and the wool carder bee are introduced, making the Galápagos carpenter bee the only native species.[ As a ]sexually dimorphic
Sexual dimorphism is the condition where sexes of the same species exhibit different Morphology (biology), morphological characteristics, including characteristics not directly involved in reproduction. The condition occurs in most dioecy, di ...
species, the male and female bees look different. The female bee is dark and shiny with black setae
In biology, setae (; seta ; ) are any of a number of different bristle- or hair-like structures on living organisms.
Animal setae
Protostomes
Depending partly on their form and function, protostome setae may be called macrotrichia, chaetae ...
, and is commonly found throughout the year. The male is rarer, with a black abdomen and yellow-brown setae.[ A rare specimen in the Smithsonian collection exhibits ]gynandromorphism
Gynandromorphism is the phenomenon that occurs when an individual organism possesses both male and female phenotypes due to genetic chimera of sex chromosomes in cells across the body and is most easily recognized in species that display sex ...
, with a visually female left side and a visually male right side.[
]
Distribution
Galapagos carpenter bees can be found on 9 out of the 12 largest islands, but not all of the islands in the archipelago. These include Isabela, San Cristóbal, Santa Cruz, Santiago, Fernandina, Floreana, Genovesa, Santa Fe, and Española.[
]
Behavior
This insect
Insects (from Latin ') are Hexapoda, hexapod invertebrates of the class (biology), class Insecta. They are the largest group within the arthropod phylum. Insects have a chitinous exoskeleton, a three-part body (Insect morphology#Head, head, ...
gets its common name 'carpenter bee' from the way that females form nests
A nest is a structure built for certain animals to hold eggs or young. Although nests are most closely associated with birds, members of all classes of vertebrates and some invertebrates construct nests. They may be composed of organic materi ...
. They bore holes into the branches
A branch, also called a ramus in botany, is a stem that grows off from another stem, or when structures like veins in leaves are divided into smaller veins.
History and etymology
In Old English, there are numerous words for branch, includi ...
and trunks of trees and lay their eggs within the solitary cavities.[ They prefer to bore holes into soft dead wood, such as the wood of ]sea hibiscus
''Hibiscus tiliaceus'', commonly known as the sea hibiscus or coast cottonwood, is a species of flowering tree in the mallow family, Malvaceae, with a pantropical distribution along coastlines. It has also been introduced to Florida and New Zeal ...
, '' Croton'', palo santo and coral trees.[ Male Galápagos carpenter bees have been recorded exhibiting territorial behavior, and may defend plants from intruders. They patrol the claimed shrub or tree and chase away trespassing animals, but allow female bees to enter the defended area.][
]
Ecological role
These insects serve as an important keystone species
A keystone species is a species that has a disproportionately large effect on its natural environment relative to its abundance. The concept was introduced in 1969 by the zoologist Robert T. Paine. Keystone species play a critical role in main ...
since they are the predominant pollinators of native and introduced plants on the islands.[ They are the most generalized pollinators in the Galápagos ]ecosystem
An ecosystem (or ecological system) is a system formed by Organism, organisms in interaction with their Biophysical environment, environment. The Biotic material, biotic and abiotic components are linked together through nutrient cycles and en ...
, meaning that they consume nectar and pollen from the widest array of different flowers, adding up to at least 84 flowering species.[ They compete for food with other pollinators including ]birds
Birds are a group of warm-blooded vertebrates constituting the class (biology), class Aves (), characterised by feathers, toothless beaked jaws, the Oviparity, laying of Eggshell, hard-shelled eggs, a high Metabolism, metabolic rate, a fou ...
, lizards
Lizard is the common name used for all squamate reptiles other than snakes (and to a lesser extent amphisbaenians), encompassing over 7,000 species, ranging across all continents except Antarctica, as well as most oceanic island chains. The ...
, and other insects.[ Their niche as pollinators is vital to the stability of plant populations, even though most well documented plant species on the archipelago are capable of ]self-pollination
Self-pollination is a form of pollination in which pollen arrives at the stigma of a flower (in flowering plants) or at the ovule (in gymnosperms) of the same plant. The term cross-pollination is used for the opposite case, where pollen from ...
.[ Galapagos carpenter bee populations could be negatively impacted by ]invasive species
An invasive species is an introduced species that harms its new environment. Invasive species adversely affect habitats and bioregions, causing ecological, environmental, and/or economic damage. The term can also be used for native spec ...
through competition and predation. Introduced birds such as the smooth-billed ani
The smooth-billed ani (''Crotophaga ani'') is a bird in the cuckoo family. It is a resident breeding species from southern Florida, the Caribbean, parts of Central America, south to western Ecuador, Brazil, northern Argentina and southern Chile. ...
have been documented preying on the bees, which could significantly affect the unique ecosystem of the archipelago.[
These bees are parasitized by the ]blister beetle
Blister beetles are beetles of the family (biology), family Meloidae, so called for their defensive secretion of a blistering agent, cantharidin. About 7,500 species are known worldwide. Many are conspicuous and some are aposematism, aposematica ...
''Cissites maculata'', and the two species have a phoretic
Phoresis or phoresy is a temporary Commensalism, commensalistic relationship when an organism (a phoront or phoretic) attaches itself to a host organism solely for travel. It has been seen in tick, ticks and mite, mites since the 18th century, ...
relationship. The presence of both the bees and parasitoid
In evolutionary ecology, a parasitoid is an organism that lives in close association with its host (biology), host at the host's expense, eventually resulting in the death of the host. Parasitoidism is one of six major evolutionarily stable str ...
beetles on the islands suggests that they were transported together and colonized the archipelago concurrently.[
]
References
{{Taxonbar, from=Q2085839
darwini
Insects described in 1926
Endemic fauna of the Galápagos Islands