The tetrakas, also known as the Malagasy warblers, are a recently validated family of

songbird A songbird is a bird belonging to the suborder Passeri of the perching birds (Passeriformes). Another name that is sometimes seen as the scientific or vernacular name is Oscines, from Latin ''oscen'', "songbird". The Passeriformes contains 5,00 ...

s. They were formally named Bernieridae in 2010. The family currently consists of eleven

species A species () is often defined as the largest group of organisms in which any two individuals of the appropriate sexes or mating types can produce fertile offspring, typically by sexual reproduction. It is the basic unit of Taxonomy (biology), ...

(in eight

genera Genus (; : genera ) is a taxonomic rank above species and below family as used in the biological classification of living and fossil organisms as well as viruses. In binomial nomenclature, the genus name forms the first part of the binomial s ...

) of small forest birds. These birds are all

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 ...

Madagascar Madagascar, officially the Republic of Madagascar, is an island country that includes the island of Madagascar and numerous smaller peripheral islands. Lying off the southeastern coast of Africa, it is the world's List of islands by area, f ...

. In 1934, the

monophyly In biological cladistics for the classification of organisms, monophyly is the condition of a taxonomic grouping being a clade – that is, a grouping of organisms which meets these criteria: # the grouping contains its own most recent comm ...

of this group was proposed by

Finn Salomonsen Finn Salomonsen (31 January 1909 – 23 April 1983) was a Danish ornithologist. He is best known for his work on the birds of Greenland. His interest in Greenland began at the age of 16 when he made a trip with Lehn Schioler to the Upernavik Dis ...

but the traditional assignments of these birds were maintained, mistaken by their

convergent evolution Convergent evolution is the independent evolution of similar features in species of different periods or epochs in time. Convergent evolution creates analogous structures that have similar form or function but were not present in the last comm ...

and the lack of dedicated research. The families to which the Malagasy warblers were formerly assigned—Pycnonotidae (

bulbul The bulbuls are members of a family, Pycnonotidae, of medium-sized passerine songbirds, which also includes greenbuls, brownbuls, leafloves, and bristlebills. The family is distributed across most of Africa and into the Middle East, tropic ...

s) and even more so Timaliidae (

Old World babbler The Old World babblers or Timaliidae, are a family (biology), family of mostly Old World passerine birds. They are rather diverse in size and coloration, but are characterised by soft, fluffy plumage. These are birds of tropical areas, with the g ...

s) and the

Old World warbler The Old World warblers are a large group of birds formerly grouped together in the bird family Sylviidae. They are not closely related to the New World warblers. The family held over 400 species in over 70 genera, and were the source of much taxo ...

—were used as " wastebin taxa", uniting unrelated lineages that were somewhat similar

ecological Ecology () is the natural science of the relationships among living organisms and their environment. Ecology considers organisms at the individual, population, community, ecosystem, and biosphere levels. Ecology overlaps with the closely re ...

ly and morphologically. It was not until the analysis of

mtDNA Mitochondrial DNA (mtDNA and mDNA) is the DNA located in the mitochondria organelles in a eukaryotic cell that converts chemical energy from food into adenosine triphosphate (ATP). Mitochondrial DNA is a small portion of the DNA contained in ...

cytochrome ''b'' and

16S rRNA 16S ribosomal RNA (or 16Svedberg, S rRNA) is the RNA component of the 30S subunit of a prokaryotic ribosome (SSU rRNA). It binds to the Shine-Dalgarno sequence and provides most of the SSU structure. The genes coding for it are referred to as ...

as well as

nDNA Nuclear DNA (nDNA), or nuclear deoxyribonucleic acid, is the DNA contained within each cell nucleus of a eukaryotic organism. It encodes for the majority of the genome in eukaryotes, with mitochondrial DNA and plastid DNA coding for the rest. It ...

RAG-1 and

RAG-2 The recombination-activating genes (RAGs) encode parts of a protein complex that plays important roles in the rearrangement and recombination of the genes encoding immunoglobulin and T cell receptor molecules. There are two recombination-activa ...

exon An exon is any part of a gene that will form a part of the final mature RNA produced by that gene after introns have been removed by RNA splicing. The term ''exon'' refers to both the DNA sequence within a gene and to the corresponding sequence ...

sequence In mathematics, a sequence is an enumerated collection of objects in which repetitions are allowed and order matters. Like a set, it contains members (also called ''elements'', or ''terms''). The number of elements (possibly infinite) is cal ...

data, that the long-proposed grouping was accepted.

Taxonomy and systematics

The family contains 11 species divided into 8 genera. The first

phylogeny A phylogenetic tree or phylogeny is a graphical representation which shows the evolutionary history between a set of species or Taxon, taxa during a specific time.Felsenstein J. (2004). ''Inferring Phylogenies'' Sinauer Associates: Sunderland, M ...

of the Bernieridae to include all eleven recognized species was performed by Younger et al. 2019: Notably, this phylogeny suggests that the genus '' Xanthomixis'' is

paraphyletic Paraphyly is a taxonomic term describing a grouping that consists of the grouping's last common ancestor and some but not all of its descendant lineages. The grouping is said to be paraphyletic ''with respect to'' the excluded subgroups. In co ...

, with '' X. tenebrosa'' more closely related to '' Crossleyia xanthophrys'' than to the other members of ''Xanthomixis''. Additionally, ''

Bernieria madagascariensis The long-billed bernieria (''Bernieria madagascariensis''), formerly known as long-billed greenbul and sometimes as common tetraka or long-billed tetraka, is a songbird species endemic to Madagascar. It is the only species placed in the genus '' ...

'' appears to be composed of three deeply diverging lineages, which may each deserve species status. However, official taxonomic descriptions of these discoveries are yet to be published. Several Bernierids are very poorly known and were described by science only very recently.

Appert's tetraka Appert's tetraka formerly known as Appert's greenbul (''Xanthomixis apperti'') is a small passerine bird endemism, endemic to the south-west of Madagascar. The species was only described in 1972, and has been the subject of considerable taxonomic ...

was only described in 1972 and the cryptic warbler in 1996. The Appert's tetraka, along with the dusky tetraka are threatened by habitat loss, and are listed as vulnerable. Most members of this family live in the humid

rainforest Rainforests are forests characterized by a closed and continuous tree Canopy (biology), canopy, moisture-dependent vegetation, the presence of epiphytes and lianas and the absence of wildfire. Rainforests can be generally classified as tropi ...

s in the east of

, though a few species are found in the drier southwest of the island. They feed on

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, ...

s and will form

mixed-species feeding flock A mixed-species feeding flock, also termed a mixed-species foraging flock, mixed hunting party or informally bird wave, is a flock of usually insectivorous birds of different species that join each other and move together while foraging. These ar ...

s of up to six species while foraging. Additionally, Bernierid species are the only known hosts for the

feather mite Feather mites are the members of diverse mite Superfamily (zoology), superfamilies: * superorder Acariformes ** Psoroptidia *** Analgoidea *** Freyanoidea *** Pterolichoidea * superorder Parasitiformes ** Dermanyssoidea They are ectoparasites on ...

genus '' Bernierinyssus''.

Taxonomy and systematics

References

Further reading