genus
Genus (; : genera ) is a taxonomic rank above species and below family (taxonomy), family as used in the biological classification of extant taxon, living and fossil organisms as well as Virus classification#ICTV classification, viruses. In bino ...
of
frog
A frog is any member of a diverse and largely semiaquatic group of short-bodied, tailless amphibian vertebrates composing the order (biology), order Anura (coming from the Ancient Greek , literally 'without tail'). Frog species with rough ski ...
s in the family Eleutherodactylidae.Hedges, S. B., W. E. Duellman, and M. P. Heinicke . 2008. New World direct-developing frogs (Anura: Terrarana): molecular phylogeny, classification, biogeography, and conservation. Zootaxa 1737: 1-182. Many of the 200 species of the genus are commonly known as "rain frogs" or "robber frogs", due to their sharp, high-pitched, insect-like calls. They are found from the southern United States south to Central America, and reach their greatest diversity in the Caribbean.
Species
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 ...
to
Puerto Rico
; abbreviated PR), officially the Commonwealth of Puerto Rico, is a Government of Puerto Rico, self-governing Caribbean Geography of Puerto Rico, archipelago and island organized as an Territories of the United States, unincorporated territo ...
are often referred to as coquís, of which the best-known species is the common coquí (''E. coqui''), which is both a national symbol of
Puerto Rico
; abbreviated PR), officially the Commonwealth of Puerto Rico, is a Government of Puerto Rico, self-governing Caribbean Geography of Puerto Rico, archipelago and island organized as an Territories of the United States, unincorporated territo ...
and a notorious
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 ...
in
Hawaii
Hawaii ( ; ) is an island U.S. state, state of the United States, in the Pacific Ocean about southwest of the U.S. mainland. One of the two Non-contiguous United States, non-contiguous U.S. states (along with Alaska), it is the only sta ...
. Two ''Eleutherodactylus'' species, '' E. limbatus'' and '' E. iberia'', are among the smallest known frogs, measuring only 8.5 mm in length (only slightly larger than ''
Paedophryne amauensis
''Paedophryne amauensis'', also known as the New Guinea Amau frog, is a species of microhylid frog endemic to eastern Papua New Guinea. At in snout-to-vent length, it was once considered the world's smallest known vertebrate. (See also Ecolo ...
'', which measures around 7.7 mm).
Etymology
The name "Eleutherodactylus" is derived from the
Greek
Greek may refer to:
Anything of, from, or related to Greece, a country in Southern Europe:
*Greeks, an ethnic group
*Greek language, a branch of the Indo-European language family
**Proto-Greek language, the assumed last common ancestor of all kno ...
words for ‘free-toed’, composed of the Ancient Greek ' (, ‘free, unbound’) and ' (, ‘finger, toe’).
Most species are small, slender, and cryptically colored, with three to five free toes. A few, such as the web-footed coquí (''E. karlschmidti'') of Puerto Rico, do have completely webbed feet.
Distribution and habitat
Species of ''Eleutherodactylus'' are found throughout the Neotropics, including the southern United States, Mexico, Central America, and the Caribbean. Additionally, the common coquí (''E. coqui'') has been introduced to several islands in the
Hawaii
Hawaii ( ; ) is an island U.S. state, state of the United States, in the Pacific Ocean about southwest of the U.S. mainland. One of the two Non-contiguous United States, non-contiguous U.S. states (along with Alaska), it is the only sta ...
an archipelago, as well as elsewhere in the Pacific.
They can be terrestrial, arboreal, or aquatic, typically living in forests or
riparian
A riparian zone or riparian area is the interface between land and a river or stream. In some regions, the terms riparian woodland, riparian forest, riparian buffer zone, riparian corridor, and riparian strip are used to characterize a ripar ...
areas, and feeding primarily upon
arthropod
Arthropods ( ) are invertebrates in the phylum Arthropoda. They possess an arthropod exoskeleton, exoskeleton with a cuticle made of chitin, often Mineralization (biology), mineralised with calcium carbonate, a body with differentiated (Metam ...
s. Many ''Eleutherodactylus'' species have highly restricted ranges and are found on only one island or in one or a few localities. Even some of these restricted species can occur at very high densities.
Reproduction and development
All species of ''Eleutherodactylus'' are characterized by direct development, in which eggs hatch directly into small frogs, completely bypassing the
tadpole
A tadpole or polliwog (also spelled pollywog) is the Larva, larval stage in the biological life cycle of an amphibian. Most tadpoles are fully Aquatic animal, aquatic, though some species of amphibians have tadpoles that are terrestrial animal, ...
stage. This adaptation (shared by few other frog genera, e.g. '' Myobatrachus'') may be largely responsible for their ecological and evolutionary success. Most species are characterized by parental behaviors, such as egg-guarding by either the male or female parent. In some cases, even young froglets are attended by parents. Another extinct Puerto Rican species, the golden coquí (''E. jasperi''), gave birth to live young. Many species (for example, Cook's robber frog, ''E. cooki''), also of Puerto Rico, exhibit
sexual dimorphism
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 ...
in size and color.
Study on ''Eleutherodactylus'' and '' Lithobates'' amphibians shows that number of offsprings instead of body size may help to find which species require conservation from being extinct.
Taxonomy
Fossil record
The oldest fossil of ''Eleutherodactylus'' is a partial humerus from the
Early Oligocene
The Rupelian is, in the geologic timescale, the older of two age (geology), ages or the lower of two stage (stratigraphy), stages of the Oligocene epoch (geology), Epoch/series (stratigraphy), Series. It spans the time between . It is preceded b ...
-aged San Sebastián Limestone of Puerto Rico, likely not long after the genus first dispersed to the Caribbean from South America.
Late Oligocene
The Chattian is, in the geologic timescale
The geologic time scale or geological time scale (GTS) is a representation of time based on the rock record of Earth. It is a system of chronological dating that uses chronostratigraphy (the pro ...
-aged ''Eleutherodactylus'' fossils are also known from
sinkhole
A sinkhole is a depression or hole in the ground caused by some form of collapse of the surface layer. The term is sometimes used to refer to doline, enclosed depressions that are also known as shakeholes, and to openings where surface water ...
Florida
Florida ( ; ) is a U.S. state, state in the Southeastern United States, Southeastern region of the United States. It borders the Gulf of Mexico to the west, Alabama to the northwest, Georgia (U.S. state), Georgia to the north, the Atlantic ...
, USA, indicating that ''Eleutherodactylus'' were formerly native to Florida (only present today as introduced species), and had likely dispersed out of the Caribbean to the North American mainland early on in their evolution. They appear to have been one of the dominant frog taxa in the region at the time, with over 174 individual remains known from these deposits. Preserved frog remains referred to ''Eleutherodactylus'' have been reported from
Miocene
The Miocene ( ) is the first epoch (geology), geological epoch of the Neogene Period and extends from about (Ma). The Miocene was named by Scottish geologist Charles Lyell; the name comes from the Greek words (', "less") and (', "new") and mea ...
aged
Dominican amber
Dominican amber is amber from the Dominican Republic derived from resin of the extinct tree '' Hymenaea protera''.
Dominican amber differentiates itself from Baltic amber by being nearly always transparent, and it has a higher number of fossil in ...
.
Phylogenetics
The basis of forming this genus has been morphological, but sequence comparisons of
protein
Proteins are large biomolecules and macromolecules that comprise one or more long chains of amino acid residue (biochemistry), residues. Proteins perform a vast array of functions within organisms, including Enzyme catalysis, catalysing metab ...
-encoding
DNA
Deoxyribonucleic acid (; DNA) is a polymer composed of two polynucleotide chains that coil around each other to form a double helix. The polymer carries genetic instructions for the development, functioning, growth and reproduction of al ...
,
mitochondrial
A mitochondrion () is an organelle found in the cells of most eukaryotes, such as animals, plants and fungi. Mitochondria have a double membrane structure and use aerobic respiration to generate adenosine triphosphate (ATP), which is used ...
DNA, and
ribosomal
Ribosomes () are macromolecular machines, found within all cells, that perform biological protein synthesis (messenger RNA translation). Ribosomes link amino acids together in the order specified by the codons of messenger RNA molecules to fo ...
RNA
Ribonucleic acid (RNA) is a polymeric molecule that is essential for most biological functions, either by performing the function itself (non-coding RNA) or by forming a template for the production of proteins (messenger RNA). RNA and deoxyrib ...
have shown geographic range is a much more consistent predictor of
cladistics
Cladistics ( ; from Ancient Greek 'branch') is an approach to Taxonomy (biology), biological classification in which organisms are categorized in groups ("clades") based on hypotheses of most recent common ancestry. The evidence for hypothesiz ...
for this group of frogs. The climbing habits of many species have evolved independently. All true members of the genus have been clustered into
subgenera
In biology, a subgenus ( subgenera) is a taxonomic rank directly below genus.
In the International Code of Zoological Nomenclature, a subgeneric name can be used independently or included in a species name, in parentheses, placed between the ge ...
, but many less-related species require more genetic data before they are to be officially classified elsewhere. The theory that the eleutherodactyline colonization of
Central America
Central America is a subregion of North America. Its political boundaries are defined as bordering Mexico to the north, Colombia to the southeast, the Caribbean to the east, and the Pacific Ocean to the southwest. Central America is usually ...
and the
Caribbean
The Caribbean ( , ; ; ; ) is a region in the middle of the Americas centered around the Caribbean Sea in the Atlantic Ocean, North Atlantic Ocean, mostly overlapping with the West Indies. Bordered by North America to the north, Central America ...
from their origins in South America occurred during the
Cretaceous
The Cretaceous ( ) is a geological period that lasted from about 143.1 to 66 mya (unit), million years ago (Mya). It is the third and final period of the Mesozoic Era (geology), Era, as well as the longest. At around 77.1 million years, it is the ...
has fallen out of favor. The
fossil record
A fossil (from Classical Latin , ) is any preserved remains, impression, or trace of any once-living thing from a past geological age. Examples include bones, shells, exoskeletons, stone imprints of animals or microbes, objects preserved ...
, combined with
molecular clock
The molecular clock is a figurative term for a technique that uses the mutation rate of biomolecules to deduce the time in prehistory when two or more life forms diverged. The biomolecular data used for such calculations are usually nucleot ...
analyses, indicate the subgenera were probably founded by small groups of individuals by flotsam dispersal from South America during the
Eocene
The Eocene ( ) is a geological epoch (geology), epoch that lasted from about 56 to 33.9 million years ago (Ma). It is the second epoch of the Paleogene Period (geology), Period in the modern Cenozoic Era (geology), Era. The name ''Eocene'' comes ...
or
Oligocene
The Oligocene ( ) is a geologic epoch (geology), epoch of the Paleogene Geologic time scale, Period that extends from about 33.9 million to 23 million years before the present ( to ). As with other older geologic periods, the rock beds that defin ...
epochs.
Land bridge
In biogeography, a land bridge is an isthmus or wider land connection between otherwise separate areas, over which animals and plants are able to cross and colonize new lands. A land bridge can be created by marine regression, in which sea le ...
s would have been limited to facilitating dispersal between
West Indian
A West Indian is a native or inhabitant of the West Indies (the Antilles and the Lucayan Archipelago). According to the ''Oxford English Dictionary'' (''OED''), the term ''West Indian'' in 1597 described the indigenous inhabitants of the West In ...
islands, however, the Oligocene division of
Hispaniola
Hispaniola (, also ) is an island between Geography of Cuba, Cuba and Geography of Puerto Rico, Puerto Rico in the Greater Antilles of the Caribbean. Hispaniola is the most populous island in the West Indies, and the second-largest by List of C ...
and
Cuba
Cuba, officially the Republic of Cuba, is an island country, comprising the island of Cuba (largest island), Isla de la Juventud, and List of islands of Cuba, 4,195 islands, islets and cays surrounding the main island. It is located where the ...
resulted in further speciation. The distribution of the subgenus '' Syrrhopus'' is most likely due to a secondary dispersal to Central America from the
Greater Antilles
The Greater Antilles is a grouping of the larger islands in the Caribbean Sea, including Cuba, Hispaniola, Puerto Rico, and Jamaica, together with Navassa Island and the Cayman Islands. Seven island states share the region of the Greater Antille ...
during the
Miocene
The Miocene ( ) is the first epoch (geology), geological epoch of the Neogene Period and extends from about (Ma). The Miocene was named by Scottish geologist Charles Lyell; the name comes from the Greek words (', "less") and (', "new") and mea ...
Pliocene
The Pliocene ( ; also Pleiocene) is the epoch (geology), epoch in the geologic time scale that extends from 5.33 to 2.58 ''
Sensu stricto
''Sensu'' is a Latin word meaning "in the sense of". It is used in a number of fields including biology, geology, linguistics, semiotics, and law. Commonly it refers to how strictly or loosely an expression is used in describing any particular c ...
'', however, it should exclude clades with distributions south of the
Panama Canal
The Panama Canal () is an artificial waterway in Panama that connects the Caribbean Sea with the Pacific Ocean. It cuts across the narrowest point of the Isthmus of Panama, and is a Channel (geography), conduit for maritime trade between th ...
West Indian
A West Indian is a native or inhabitant of the West Indies (the Antilles and the Lucayan Archipelago). According to the ''Oxford English Dictionary'' (''OED''), the term ''West Indian'' in 1597 described the indigenous inhabitants of the West In ...
West Indian
A West Indian is a native or inhabitant of the West Indies (the Antilles and the Lucayan Archipelago). According to the ''Oxford English Dictionary'' (''OED''), the term ''West Indian'' in 1597 described the indigenous inhabitants of the West In ...
Hispaniola
Hispaniola (, also ) is an island between Geography of Cuba, Cuba and Geography of Puerto Rico, Puerto Rico in the Greater Antilles of the Caribbean. Hispaniola is the most populous island in the West Indies, and the second-largest by List of C ...
North
North is one of the four compass points or cardinal directions. It is the opposite of south and is perpendicular to east and west. ''North'' is a noun, adjective, or adverb indicating Direction (geometry), direction or geography.
Etymology
T ...
/
Central America
Central America is a subregion of North America. Its political boundaries are defined as bordering Mexico to the north, Colombia to the southeast, the Caribbean to the east, and the Pacific Ocean to the southwest. Central America is usually ...
n and
Cuba
Cuba, officially the Republic of Cuba, is an island country, comprising the island of Cuba (largest island), Isla de la Juventud, and List of islands of Cuba, 4,195 islands, islets and cays surrounding the main island. It is located where the ...