Editing Megabat (section)

===Evolutionary history===
====Fossil record and divergence times====
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.<ref>{{Cite journal |last1=Brown |first1=Emily E. |last2=Cashmore |first2=Daniel D. |last3=Simmons |first3=Nancy B. |last4=Butler |first4=Richard J. |date=2019-03-25 |editor-last=Mannion |editor-first=Philip |title=Quantifying the completeness of the bat fossil record |url=https://onlinelibrary.wiley.com/doi/epdf/10.1111/pala.12426 |journal=Palaeontology |language=en |publisher=Paleobiology Database |volume=62 |issue=5 |pages=757–776 |doi=10.1111/pala.12426 |bibcode=2019Palgy..62..757B |s2cid=133901426 |issn=0031-0239}}</ref> 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.<ref>{{cite journal|last1=Eiting|first1=T. P.|last2=Gunnell|first2=G. F.|year=2009|title=Global Completeness of the Bat Fossil Record|journal=Journal of Mammalian Evolution|volume=16|issue=3|pages=157|doi=10.1007/s10914-009-9118-x|s2cid=5923450}}</ref> It is estimated that more than 98% of pteropodid fossil history is missing.<ref name="Teeling 2005">{{cite journal|doi=10.1126/science.1105113|pmid=15681385|title=A Molecular Phylogeny for Bats Illuminates Biogeography and the Fossil Record|journal=Science|volume=307|issue=5709|pages=580–584|year=2005|last1=Teeling|first1=E. C.|last2=Springer|first2=M. S.|last3=Madsen|first3=O.|last4=Bates|first4=P.|last5=O'Brien|first5=S. J.|last6=Murphy|first6=W. J.|bibcode=2005Sci...307..580T|s2cid=25912333| url=https://courses.cit.cornell.edu/bionb4240/Reprints/Bat%20phylogeny%20Teeling%20et%20al%202005.pdf}}</ref> 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&nbsp;Mya (million years ago).<ref name="Teeling 2005"/> The ancestor of the [[crown group]] of Pteropodidae, or all living species, lived approximately 31&nbsp;Mya.<ref name="Almeida 2009"/>

====Biogeography====
[[File:Oceania UN Geoscheme - Map of Melanesia cropped.jpg|thumb|upright=1.2|alt=A map of Oceania with the islands of Melanesia highlighted in pink.|Melanesia, where many megabat subfamilies are likely to have originated]]
The family Pteropodidae likely originated in [[Australasia]] based on [[biogeography|biogeographic reconstructions]].<ref name="Almeida 2016"/> Other biogeographic analyses have suggested that the [[Melanesia]]n Islands, including [[New Guinea]], are a plausible candidate for the origin of most megabat subfamilies, with the exception of Cynopterinae;<ref name="Almeida 2011">{{cite journal|doi=10.1186/1471-2148-11-281|pmid=21961908|pmc=3199269|title=Evolutionary relationships of the old world fruit bats (Chiroptera, Pteropodidae): Another star phylogeny?|journal=[[BMC Evolutionary Biology]]|volume=11|page=281|year=2011|last1=Almeida|first1=F. C.| last2=Giannini|first2=N. P.|last3=Desalle|first3=R.|last4=Simmons|first4=N. B. |issue=1 |doi-access=free |bibcode=2011BMCEE..11..281A }}</ref> the cynopterines likely originated on the [[Sunda Shelf]] based on results of a Weighted Ancestral Area Analysis of six nuclear and mitochondrial genes.<ref name="Almeida 2009">{{cite journal|doi=10.1016/j.ympev.2009.07.035|pmid=19660560|title=The phylogenetic relationships of cynopterine fruit bats (Chiroptera: Pteropodidae: Cynopterinae)|journal=[[Molecular Phylogenetics and Evolution]]|volume=53|issue=3|pages=772–783|year=2009|last1=Almeida|first1=F. C.|last2=Giannini|first2=N. P.|last3=Desalle|first3=Rob|last4=Simmons|first4=N. B.|hdl=11336/74530|hdl-access=free}}</ref> 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]];<ref>{{cite journal|doi=10.1016/j.ympev.2009.02.010|pmid=19249376|title=Multiple colonisations of the western Indian Ocean by Pteropus fruit bats (Megachiroptera: Pteropodidae): The furthest islands were colonised first|journal=Molecular Phylogenetics and Evolution|volume=51|issue=2|pages=294–303|year=2009|last1=O'Brien|first1=J.|last2=Mariani|first2=C.|last3=Olson|first3=L.|last4=Russell|first4=A. L.|last5=Say|first5=L.|last6=Yoder|first6=A. D.|last7=Hayden|first7=T. J.|bibcode=2009MolPE..51..294O }}</ref> this is less likely for other megabat genera, which have smaller body sizes and thus have more limited flight capabilities.<ref name="Almeida 2016"/>

====Echolocation====
Megabats are the only family of bats incapable of [[larynx|laryngeal]] echolocation. It is unclear whether the common ancestor of all bats was capable of echolocation, and thus echolocation was lost in the megabat lineage, or multiple bat lineages independently evolved the ability to echolocate (the superfamily [[Rhinolophoidea]] and the suborder [[Yangochiroptera]]). This unknown element of bat evolution has been called a "grand challenge in biology".<ref>{{cite book | vauthors = Teeling EC, Jones G, Rossiter SJ |chapter=Phylogeny, Genes, and Hearing: Implications for the Evolution of Echolocation in Bats |date=2016 |pages=25–54 | veditors = Fenton MB, Grinnell AD, Popper AN, Fay RN |series=Springer Handbook of Auditory Research |publisher=Springer | location = New York |doi=10.1007/978-1-4939-3527-7_2 |isbn=9781493935277 |title=Bat Bioacoustics |volume=54 }}</ref> 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.<ref>{{cite journal|doi=10.1038/s41559-016-0021|pmid=28812602|title=Prenatal development supports a single origin of laryngeal echolocation in bats|journal=Nature Ecology & Evolution|volume=1|issue=2|pages=21|year=2017|last1=Wang|first1=Zhe|last2=Zhu|first2=Tengteng|last3=Xue|first3=Huiling|last4=Fang|first4=Na|last5=Zhang|first5=Junpeng|last6=Zhang|first6=Libiao|last7=Pang|first7=Jian|last8=Teeling|first8=Emma C.|last9=Zhang|first9=Shuyi|s2cid=29068452}}</ref> Megabats in the genus ''Rousettus'' are capable of primitive echolocation through clicking their tongues.<ref>{{cite journal | last1= Holland| first1= R. A.| last2= Waters| first2= D. A.| last3= Rayner| first3= J. M.| title = Echolocation signal structure in the Megachiropteran bat Rousettus aegyptiacus Geoffroy 1810 | journal = [[The Journal of Experimental Biology]] | volume = 207 | issue = Pt 25 | pages = 4361–4369 | date = December 2004 | pmid = 15557022 | doi = 10.1242/jeb.01288 | bibcode= 2004JExpB.207.4361H| s2cid= 2715542}}</ref> Some species&mdash;the [[cave nectar bat]] (''Eonycteris spelaea''), [[lesser short-nosed fruit bat]] (''Cynopterus brachyotis''), and the [[long-tongued fruit bat]] (''Macroglossus sobrinus'')&mdash;have been shown to create clicks similar to those of echolocating bats using their wings.<ref name=Boonman2014>{{cite journal | last1 = Boonman| first1= A.| last2= Bumrungsri| first2= S.| last3= Yovel| first3= Y. | title = Nonecholocating fruit bats produce biosonar clicks with their wings | journal = Current Biology | volume = 24 | issue = 24 | pages = 2962–2967 | date = December 2014 | pmid = 25484290 | doi = 10.1016/j.cub.2014.10.077 | s2cid= 17789233| doi-access = free | bibcode= 2014CBio...24.2962B}}</ref>

Both echolocation and [[Bat flight|flight]] are energetically expensive processes separately, although no increase in flight energy expenditure was found for two species of echolocating bats compared with other bats and birds .<ref>{{cite journal | last1= Speakman| first1= J. R.| last2= Racey| first2= P. A. | title = No cost of echolocation for bats in flight | journal = Nature | volume = 350 | issue = 6317 | pages = 421–423 | date = April 1991 | pmid = 2011191 | doi = 10.1038/350421a0 | bibcode = 1991Natur.350..421S | s2cid= 4314715}}</ref> 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.<ref>{{cite journal | last1=  Lancaster| first1= W. C.| last2= Henson| first2= O. W.| last3= Keating| first3= A. W. | title = Respiratory muscle activity in relation to vocalization in flying bats | journal = The Journal of Experimental Biology | volume = 198 | issue = Pt 1 | pages = 175–191 | date = January 1995 | doi= 10.1242/jeb.198.1.175| pmid = 7891034| bibcode= 1995JExpB.198..175L|url=http://jeb.biologists.org/content/jexbio/198/1/175.full.pdf }}</ref> The loss of echolocation (or conversely, the lack of its evolution) may be due to the uncoupling of flight and echolocation in megabats.<ref name="Book" /> The larger average body size of megabats compared to echolocating bats<ref name="Hutcheon 2004" /> suggests a larger body size disrupts the flight-echolocation coupling and made echolocation too energetically expensive to be conserved in megabats.<ref name="Book">{{cite book |last=Altringham |first=J. D. | name-list-style = vanc |year=2011 |chapter=Echolocation and other senses| title=Bats: From Evolution to Conservation|location=New York |publisher=[[Oxford University Press]] |isbn=9780199207114 }}</ref>