Жеміс жейтін құстардың тұқымдасы

Family of fruit bats

Megabats constitute the family Pteropodidae of the order Chiroptera (bats). They are also called fruit bats, Old World fruit bats, or—especially the genera Acerodon and Pteropus—flying foxes. They are the only member of the superfamily Pteropodoidea, which is one of two superfamilies in the suborder Yinpterochiroptera. Internal divisions of Pteropodidae have varied since subfamilies were first proposed in 1917. From three subfamilies in the 1917 classification, six are now recognized, along with various tribes. As of 2018, 197 species of megabat had been described. The leading theory of the evolution of megabats has been determined primarily by genetic data, as the fossil record for this family is the most fragmented of all bats. They likely evolved in Australasia, with the common ancestor of all living pteropodids existing approximately 31 million years ago. Many of their lineages probably originated in Melanesia, then dispersed over time to mainland Asia, the Mediterranean, and Africa. Today, they are found in tropical and subtropical areas of Eurasia, Africa, and Oceania. The megabat family contains the largest bat species, with individuals of some species weighing up to and having wingspans up to Not all megabats are large bodied; nearly a third of all species weigh less than They can be differentiated from other bats due to their dog like faces, clawed second digits, and reduced uropatagium. Only members of one genus, Notopteris, have tails. Megabats have several adaptations for flight, including rapid oxygen consumption, the ability to sustain heart rates of more than 700 beats per minute, and large lung volumes. Most megabats are nocturnal or crepuscular, although a few species are active during the daytime. During the period of inactivity, they roost in trees or caves. Members of some species roost alone, while others form colonies of up to a million individuals. During the period of activity, they use flight to travel to food resources. With few exceptions, they are unable to echolocate, relying instead on keen senses of sight and smell to navigate and locate food. Most species are primarily frugivorous and several are nectarivorous. Other less common food resources include leaves, pollen, twigs, and bark. They reach sexual maturity slowly and have a low reproductive output. Most species have one offspring at a time after a pregnancy of four to six months. This low reproductive output means that after a population loss their numbers are slow to rebound. A quarter of all species are listed as threatened, mainly due to habitat destruction and overhunting. Megabats are a popular food source in some areas, leading to population declines and extinction. They are also of interest to those involved in public health as they are natural reservoirs of several viruses that can affect humans.

cladogram|align=right|style=width:30%;line height:85%|caption=Internal relationships of African Pteropodidae based on combined evidence of mitochondrial and nuclear DNA. One species each of Pteropodinae, Nyctimeninae, and Cynopterinae, which are not found in Africa, were included as outgroups. Fructivorae contained one other family, the now defunct Cephalotidae, containing one genus, Cephalotes Gray's spelling was possibly based on a misunderstanding of the suffix of "Pteropus". "Pteropus" comes from Ancient Greek pterón meaning "wing" and poús meaning "foot". The Greek word pous of Pteropus is from the stem word pod ; therefore, Latinizing Pteropus correctly results in the prefix "Pteropod ". French biologist Charles Lucien Bonaparte was the first to use the corrected spelling Pteropodidae in 1838. Dobson selected these names to allude to the body size differences of the two groups, with many fruit eating bats being larger than insect eating bats. Pteropodidae was the only family he included within Megachiroptera. Since 2005, this suborder has alternatively been called "Pteropodiformes". Two superfamilies comprise Yinpterochiroptera: Rhinolophoidea—containing the above families formerly in Microchiroptera—and Pteropodoidea, which only contains Pteropodidae. In 1917, Danish mammalogist Knud Andersen divided Pteropodidae into three subfamilies: Macroglossinae, Pteropinae (corrected to Pteropodinae), and Harpyionycterinae. A 1995 study found that Macroglossinae as previously defined, containing the genera Eonycteris, Notopteris, Macroglossus, Syconycteris, Melonycteris, and Megaloglossus, was paraphyletic, meaning that the subfamily did not group all the descendants of a common ancestor. Subsequent publications consider Macroglossini as a tribe within Pteropodinae that contains only Macroglossus and Syconycteris. In 1984, an additional pteropodid subfamily, Propottininae, was proposed, representing one extinct species described from a fossil discovered in Africa, Propotto leakeyi. In 2018 the fossils were reexamined and determined to represent a lemur. As of 2018, there were 197 described species of megabat, around a third of which are flying foxes of the genus Pteropus.

The fossil record for pteropodid bats is the most incomplete of any bat family. Although the poor skeletal record of Chiroptera is probably from how fragile bat skeletons are, Pteropodidae still have the most incomplete despite generally having the biggest and most sturdy skeletons. It is also surprising that Pteropodidae are the least represented because they were the first major group to diverge. Several factors could explain why so few pteropodid fossils have been discovered: tropical regions where their fossils might be found are under sampled relative to Europe and North America; conditions for fossilization are poor in the tropics, which could lead to fewer fossils overall; and even when fossils are formed, they may be destroyed by subsequent geological activity. It is estimated that more than 98% of pteropodid fossil history is missing. Even without fossils, the age and divergence times of the family can still be estimated by using computational phylogenetics. Pteropodidae split from the superfamily Rhinolophoidea (which contains all the other families of the suborder Yinpterochiroptera) approximately 58 Mya (million years ago). the cynopterines likely originated on the Sunda Shelf based on results of a Weighted Ancestral Area Analysis of six nuclear and mitochondrial genes. From these regions, pteropodids colonized other areas, including continental Asia and Africa. Megabats reached Africa in at least four distinct events. The four proposed events are represented by (1) Scotonycteris, (2) Rousettus, (3) Scotonycterini, and (4) the "endemic Africa clade", which includes Stenonycterini, Plerotini, Myonycterini, and Epomophorini, according to a 2016 study. It is unknown when megabats reached Africa, but several tribes (Scotonycterini, Stenonycterini, Plerotini, Myonycterini, and Epomophorini) were present by the Late Miocene. How megabats reached Africa is also unknown. It has been proposed that they could have arrived via the Middle East before it became more arid at the end of the Miocene. Conversely, they could have reached the continent via the Gomphotherium land bridge, which connected Africa and the Arabian Peninsula to Eurasia. The genus Pteropus (flying foxes), which is not found on mainland Africa, is proposed to have dispersed from Melanesia via island hopping across the Indian Ocean; this is less likely for other megabat genera, which have smaller body sizes and thus have more limited flight capabilities. A 2017 study of bat ontogeny (embryonic development) found evidence that megabat embryos at first have large, developed cochlea similar to echolocating microbats, though at birth they have small cochlea similar to non echolocating mammals. This evidence supports that laryngeal echolocation evolved once among bats, and was lost in pteropodids, rather than evolving twice independently. Megabats in the genus Rousettus are capable of primitive echolocation through clicking their tongues. Some species—the cave nectar bat (Eonycteris spelaea), lesser short nosed fruit bat (Cynopterus brachyotis), and the long tongued fruit bat (Macroglossus sobrinus)—have been shown to create clicks similar to those of echolocating bats using their wings. Both echolocation and flight are energetically expensive processes. Echolocating bats couple sound production with the mechanisms engaged for flight, allowing them to reduce the additional energy burden of echolocation. Instead of pressurizing a bolus of air for the production of sound, laryngeally echolocating bats likely use the force of the downbeat of their wings to pressurize the air, cutting energetic costs by synchronizing wingbeats and echolocation. The loss of echolocation (or conversely, the lack of its evolution) may be due to the uncoupling of flight and echolocation in megabats.

Megabats are threatened by habitat destruction by humans. Deforestation of their habitats has resulted in the loss of critical roosting habitat. Deforestation also results in the loss of food resource, as native fruit bearing trees are felled. Habitat loss and resulting urbanization leads to construction of new roadways, making megabat colonies easier to access for overharvesting. Additionally, habitat loss via deforestation compounds natural threats, as fragmented forests are more susceptible to damage from typhoon force winds. while human persecution stemming from perceived damage to crops is also a large source of mortality. Some megabats have been documented to have a preference for native fruit trees over fruit crops, but deforestation can reduce their food supply, causing them to rely on fruit crops. Culling campaigns can dramatically reduce megabat populations. In Mauritius, over 40,000 Mauritian flying foxes were culled between 2014 and 2016, reducing the species' population by an estimated 45%. Megabats are also killed by electrocution. In one Australian orchard, it is estimated that over 21,000 bats were electrocuted to death in an eight week period. Farmers construct electrified grids over their fruit trees to kill megabats before they can consume their crop. The grids are questionably effective at preventing crop loss, with one farmer who operated such a grid estimating they still lost of fruit to flying foxes in a year. Some electrocution deaths are also accidental, such as when bats fly into overhead power lines. Climate change causes flying fox mortality and is a source of concern for species persistence. Extreme heat waves in Australia have been responsible for the deaths of more than 30,000 flying foxes from 1994 to 2008. Females and young bats are most susceptible to extreme heat, which affects a population's ability to recover. Megabats are threatened by sea level rise associated with climate change, as several species are endemic to low lying atolls. As many megabat species are located in the tectonically active Ring of Fire, they are also threatened by volcanic eruptions. Flying foxes, including the endangered Mariana fruit bat, have been nearly exterminated from the island of Anatahan following a series of eruptions beginning in 2003.