The Hawaiian Drosophilidae are a lineage of flies within the genus ''

Drosophila ''Drosophila'' () is a genus of flies, belonging to the family Drosophilidae, whose members are often called "small fruit flies" or (less frequently) pomace flies, vinegar flies, or wine flies, a reference to the characteristic of many species ...

.'' This

monophyletic In cladistics for a group of organisms, monophyly is the condition of being a clade—that is, a group of taxa composed only of a common ancestor (or more precisely an ancestral population) and all of its lineal descendants. Monophyletic gro ...

clade includes all of the

endemic Endemism is the state of a species being found 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 found elsew ...

Hawaiian ''Drosophila'' and all members of the genus '' Scaptomyza'', which contains both Hawaiian and non-Hawaiian species. The Hawaiian Drosophilidae are descended from a common ancestor estimated to have lived 25 million years ago. Species of Hawaiian Drosophilidae flies have been studied as

models A model is an informative representation of an object, person or system. The term originally denoted the plans of a building in late 16th-century English, and derived via French and Italian ultimately from Latin ''modulus'', a measure. Models c ...

speciation Speciation is the evolutionary process by which populations evolve to become distinct species. The biologist Orator F. Cook coined the term in 1906 for cladogenesis, the splitting of lineages, as opposed to anagenesis, phyletic evolution within ...

and behavioral evolution. Along with other members of the native Hawaiian ecosystem, the conservations status of many species of Hawaiian Drosophilidae is threatened by habitat loss and introduced predators, among other factors.

Diversity

There are an estimated 1,000 species of Hawaiian Drosophilidae. 689 species have been described, including 273 species in the genus '' Scaptomyza'', of which 148 are

to the Hawaiian archipelago, and 416 Hawaiian endemic species in the genus ''

.'' Within the Hawaiian ''Drosophila'' there are several major groups, including the ''modified-mouthpart'', ''modified-tarsus'', and ''antopocerus'' species groups, and the picture-wing clade.

''Scaptomyza''

The genus '' Scaptomyza'', which contains both Hawaiian and non-Hawaiian species, is the

sister lineage In phylogenetics, a sister group or sister taxon, also called an adelphotaxon, comprises the closest relative(s) of another given unit in an evolutionary tree. Definition The expression is most easily illustrated by a cladogram: Taxon A and t ...

to the Hawaiian ''Drosophila,'' and Hawaiian species in this genus are often included when speaking about the Hawaiian ''Drosophila'' generally. The Hawaiian and non-Hawaiian distribution of ''Scaptomyza'' can be explained as either the result of multiple colonizations of Hawaii, or as the result of one colonization by the common ancestor of ''Scaptomyza'' and Hawaiian ''Drosophila'', followed by several migrations back to continents. ''Scaptomyza'' is one of several genera that are currently nested within the genus ''Drosophila'', rendering it

paraphyletic In taxonomy (general), taxonomy, a group is paraphyletic if it consists of the group's most recent common ancestor, last common ancestor and most of its descendants, excluding a few Monophyly, monophyletic subgroups. The group is said to be pa ...

Hawaiian ''Drosophila''

''Picture-wing'', ''nudidrosophila'', ''ateledrosophila'' (PNA) clade

The picture-wing clade of Hawaiian ''Drosophila'' is named for the intricate patterns of melanin pigment on their wings. This clade includes the ''grimshawi, planitibia,'' and ''adiastola'' species groups, among others. Research on the taxonomy and biology of picture-wing flies in the 1970's led to the description of 105 species, with several more described in the decades since. More recent studies on variation in wing patterns has led to the generation of a database devoted solely to wing diversity in the Hawaiian ''Drosophila'' lineage. These flies have also been extensively studied for their courtship behavior, potential for hybridization between species, and larval ecology. Many species of picture-wing flies breed in rotting bark and stems.

''Antopocerus'', ''modified-tarsus'', ''ciliated-tarsus'' (AMC) clade

The ''antopocerus'' species group includes 15 species of flies, notable for their large adult body size and egg size, as well as the prominent antennae on males. ''Antopocerus'' was previously considered as a distinct genus, before being sunk into the genus ''Drosophila'' based on their phylogenetic position within other Hawaiian lineages. Species of ''antopocerus'' flies have been described from the islands of

Maui The island of Maui (; Hawaiian: ) is the second-largest of the islands of the state of Hawaii at 727.2 square miles (1,883 km2) and is the 17th largest island in the United States. Maui is the largest of Maui County's four islands, which ...

Molokai Molokai , or Molokai (), is the fifth most populated of the eight major islands that make up the Hawaiian Islands, Hawaiian Islands archipelago in the middle of the Pacific Ocean. It is 38 by 10 miles (61 by 16 km) at its greatest length an ...

Lanai Lanai ( haw, Lānai, , , also ,) is the sixth-largest of the Hawaiian Islands and the smallest publicly accessible inhabited island in the chain. It is colloquially known as the Pineapple Island because of its past as an island-wide pineapple pl ...

Hawaii Hawaii ( ; haw, Hawaii or ) is a state in the Western United States, located in the Pacific Ocean about from the U.S. mainland. It is the only U.S. state outside North America, the only state that is an archipelago, and the only stat ...

, and one species from

Oahu Oahu () (Hawaiian language, Hawaiian: ''Oʻahu'' ()), also known as "The Gathering place#Island of Oʻahu as The Gathering Place, Gathering Place", is the third-largest of the Hawaiian Islands. It is home to roughly one million people—over t ...

. The ''modified-tarsus'' species group is so named because of the variation in the shape and structure of front tarsi of males. These tarsal modifications include flattened, spoon-shaped structures, elongated cilia, and clusters of bristles, and are thought to be used in mating displays. ''Antopocerus'' and ''modified-tarsus'' flies largely breed in rotting leaves.

''Modified-mouthparts'' species group

The ''modified-mouthparts'' species group is named for the divergent forms of labellar structures relative to other ''Drosophila'' species. This large group of flies has received relatively less study, in part due to their rarity and because many species are not attracted to typical ''Drosophila'' baits. These flies show a remarkable diversity in breeding ecology, with the majority of species using more than one host family for larval feeding. There are more than 100 described species of ''modified-mouthparts'' flies, distributed throughout all major Hawaiian islands.

''Haleakalae'' species group

''Haleakalae'' species are typically small, slender, and with shiny black bodies. Rearing records indicate that members of this group breed exclusively on fungus. There are more than 50 described species of ''Haleakalae'' flies, distributed throughout all major Hawaiian islands. These species are characterized by their simple courtship displays, relative to some picture-wing species, and the short filaments on their eggs. Some species also have a black rim on the labellum.

''Rustica'' species group

This enigmatic species group includes three species, described from

, and

, that been historically difficult to place within Hawaiian ''Drosophila'' because they display traits similar to multiple other groups. These traits include a sclerotized rim on the labellum, reminiscent of several ''haleakalae'' species, and tarsi with cilia, reminiscent of ''ciliated-tarsus'' species in the AMC clade.

Research

Hawaii speciation (Drosophila and Cyanea colonization)

Hawaiian ''Drosophila'' have been studied as models of speciation, population genetics and genomics, as well as for evolution of behavior and evolutionary development (aka

evo-devo Evolutionary developmental biology (informally, evo-devo) is a field of biological research that compares the developmental processes of different organisms to infer how developmental processes evolved. The field grew from 19th-century beginni ...

). Research in the 1970s-80s by Hampton L. Carson and others studying patterns of

chromosome banding A karyotype is the general appearance of the complete set of metaphase chromosomes in the cells of a species or in an individual organism, mainly including their sizes, numbers, and shapes. Karyotyping is the process by which a karyotype is disce ...

, mating behavior, and

hybridization Hybridization (or hybridisation) may refer to: *Hybridization (biology), the process of combining different varieties of organisms to create a hybrid *Orbital hybridization, in chemistry, the mixing of atomic orbitals into new hybrid orbitals *Nu ...

helped resolve relationships between species and contributed to understanding of evolution on islands. The genome of ''

Drosophila grimshawi ''Drosophila grimshawi'' is a species In biology, a species is the basic unit of classification and a taxonomic rank of an organism, as well as a unit of biodiversity. A species is often defined as the largest group of organisms in which ...

'' was selected to be one of the landmark 12 ''Drosophila'' genomes sequenced in 2007. Since then the genome size of multiple species have been investigated, revealing genomic expansions in multiple lineages composed primarily of

satellite DNA Satellite DNA consists of very large arrays of tandemly repeating, non-coding DNA. Satellite DNA is the main component of functional centromeres, and form the main structural constituent of heterochromatin. The name "satellite DNA" refers to the p ...

and

noncoding Non-coding DNA (ncDNA) sequences are components of an organism's DNA that do not encode protein sequences. Some non-coding DNA is transcribed into functional non-coding RNA molecules (e.g. transfer RNA, microRNA, piRNA, ribosomal RNA, and regula ...

sequences.

Ecology and reproduction

Like many other members of the family

Drosophilidae The Drosophilidae are a diverse, cosmopolitan family of flies, which includes species called fruit flies, although they are more accurately referred to as vinegar or pomace flies. Another distantly related family of flies, Tephritidae, are true f ...

, Hawaiian species are largely

saprophagous Saprotrophic nutrition or lysotrophic nutrition is a process of chemoheterotrophic extracellular digestion involved in the processing of decayed (dead or waste) organic matter. It occurs in saprotrophs, and is most often associated with fungi ( ...

. Female flies lay their eggs in a wide array of substrates, including rotting bark, leaves, fruit, sap, and fungi. Across species there is substantial diversity in the choice of host organism, using as many as 34 families of Hawaiian native flowering plants as hosts. Many individual species are highly host specific and breed in only one substrate type from one or a few species. Several groups of Hawaiian Drosophilidae show more unusual breeding habits for Drosophilidae flies, such as the ''cytrandrae'' species group (''Scaptomyza cyrtandrae'' and ''S. neocyrtandrae'')'','' which breed on fresh '' Cytrandra'' leaves, and the ''Scaptomyza'' subgenus '' Titanochaeta,'' which breed in spider egg sacs. There is significant variation in reproductive morphology across species, including the number of

ovariole An ovariole is a tubular component of the insect ovary, and the basic unit of egg production. Each ovariole is composed of a germarium (the germline stem cell niche) at the anterior tip, a set of developing oocytes contained within follicles, and ...

s in the ovary, the shape of the

ovipositor The ovipositor is a tube-like organ used by some animals, especially insects, for the laying of eggs. In insects, an ovipositor consists of a maximum of three pairs of appendages. The details and morphology of the ovipositor vary, but typical ...

, and the size and shape of eggs. Research on the evolution of these traits suggests that variation is related to differences in the substrate where flies lay eggs.

Status and conservation

Surveys of species abundance over time have shown a general decline in the number of Hawaiian Drosophilidae flies, along with other organisms in the native Hawaiian ecosystem. Currently 13 species are listed as federally

endangered An endangered species is a species that is very likely to become extinct in the near future, either worldwide or in a particular political jurisdiction. Endangered species may be at risk due to factors such as habitat loss, poaching and inva ...

: '' Drosophila aglaia'', '' D. differens'', '' D. digressa,'' '' D. hemipeza'', '' D. heteroneura'', '' D. montgomeryi'', '' D. musaphilia'', '' D. neoclavisetae'', '' D. obatai'', '' D. ochrobasis'', '' D. sharpi,'' '' D. substenoptera'', and '' D. tarphytrichia.'' One species, '' D. mulli'', is listed as

threatened Threatened species are any species (including animals, plants and fungi) which are vulnerable to endangerment in the near future. Species that are threatened are sometimes characterised by the population dynamics measure of ''critical depensat ...

. Threats to the conservation of Hawaiian Drosophilidae include loss-of-habitat, in part due to invasive pigs, goats, rats, deer, and cattle, as well as introduced predators such as big-headed ants, yellow crazy ants, and yellowjacket wasps. In addition, invasive plants such as ''

Psidium cattleianum ''Psidium cattleyanum (World Plants : Psidium cattleianum)'', commonly known as Cattley guava, strawberry guava or cherry guava, is a small tree (2–6 m tall) in the Myrtaceae (myrtle) family. The species is named in honour of English hor ...

'', ''

Lantana camara ''Lantana camara'' (common lantana) is a species of flowering plant within the verbena family (Verbenaceae), native to the American tropics. It is a very adaptable species, which can inhabit a wide variety of ecosystems; once it has been introduc ...

'', ''

Melinis minutiflora ''Melinis minutiflora'', commonly known as molasses grass, is a species of grass. It is a perennial grass native to Africa, where it occurs in disjunct populations (an arc from central Angola to Cameroon in western central africa, the areas arou ...

'', and ''

Rubus argutus ''Rubus argutus'' is a North American species of prickly bramble in the rose family. It is a perennial plant native to the eastern and south-central United States. Common names are sawtooth blackberry or tall blackberry after its high growth. ...

'' can overwhelm native host plant species and outcompete them for access to sunlight. Flammable grass species such as ''

'' also contribute to rapidly spreading forest fires. These threats are especially relevant because many native host plants for Hawaiian Drosophilidae are already very rare.

Species groups

The following is a list of species groups contained within the Hawaiian Drosophilidae lineage: * '' Scaptomyza'' genus (273 described species) * Hawaiian ''Drosophila'' (416 described species) ** ''antopocerus, modified-tarsus, ciliated tarsus'' (AMC) clade ***''antopocerus'' species group ***''modified-tarsus'' species group **''picture-wing, nudidrosophila, ateledrosophila'' (PNA) clade ***''adiastola'' species group ***''grimshawi'' species group ***''ateledrosophila'' species group ***''nudidrosophila'' species group ***''picticornis'' species group ***''planitibia'' species group **''haleakalae'' species group ** ''modified-mouthpart'' species group ** ''rustica'' species group

Gallery

File:Scaptomyza flava.jpg, ''

Scaptomyza flava ''Scaptomyza flava'' is an herbivorous leaf mining fly species in the family Drosophilidae. In Latin, '' flava'' means golden or yellow. The fly is amber to dark brown in color and approximately 2.5 mm in length. In Europe and New Zealand th ...

'' File:Scaptomyza pallida 06.JPG, '' Scaptomyza pallida'' File:Drosophila silvestris Kilohana 5161a.jpg, ''

Drosophila silvestris ''Drosophila silvestris'' is a large species of fly in the family Drosophilidae that are primarily black with yellow spots. As a rare species of fruit fly endemic to Hawaii (“the Big Island”), the fly often experiences reproductive isolatio ...

'' File:Drosophila setosimentum.jpg, '' Drosophila setosimentum'' File:Drosophila villosipedis.jpg, '' Drosophila villosipedis'' File:Drosophila picticornis.jpg, '' Drosophila picticornis'' File:Drosophila primaeva.jpg, '' Drosophila primaeva'' File:Drosophila sproati.jpg, '' Drosophila sproati'' File:Scaptomyza cyrtandrae.jpg, '' Scaptomyza cyrtandrae'' File:Drosophila glabriapex.jpg, '' Drosophila glabriapex'' File:Drosophila mimica.jpg, '' Drosophila mimica''

References

{{Taxonbar, from=Q105038844 Drosophila Endemic fauna of Hawaii