Editing Adaptive radiation (section)

=== Cichlids of the African Great Lakes ===
The [[haplochromine]] [[cichlid]] fishes in the [[African Great Lakes|Great Lakes]] of the [[East African Rift]] (particularly in [[Lake Tanganyika]], [[Lake Malawi]], and [[Lake Victoria]]) form the most speciose modern example of adaptive radiation.<ref name="Seehausen">{{Cite book|title=Lake Victoria Rock Cichlids: taxonomy, ecology, and distribution|last=Seehausen|first=Ole|publisher=Verduyn Cichlids|year=1996|isbn=90-800181-6-3}}</ref><ref name="Konings">{{Cite book|title=Tanganyika Cichlids in their natural habitat, 3rd Edition|last=Konings|first=Ad|publisher=Cichlid Press|year=2015|isbn=978-1-932892-18-5|location=El Paso, TX|pages=8, 325–328}}</ref><ref name="Konings2">{{Cite book|title=Malawi Cichlids in their natural habitat, 5th edition|last=Konings|first=Ad|publisher=Cichlid Press|year=2016|isbn=978-1-932892-23-9|location=El Paso, TX}}</ref> These lakes are believed to be home to about 2,000 different species of cichlid, spanning a wide range of ecological roles and morphological characteristics.<ref name="Losos, Jonathan B 20102">{{cite journal|last1=Losos|first1=Jonathan B|year=2010|title=Adaptive Radiation, Ecological Opportunity, and Evolutionary Determinism|url=http://nrs.harvard.edu/urn-3:HUL.InstRepos:9464287|journal=The American Naturalist|volume=175|issue=6|pages=623–639|doi=10.1086/652433|pmid=20412015|s2cid=1657188}}</ref> Cichlids in these lakes fill nearly all of the roles typically filled by many fish families, including those of predators, scavengers, and herbivores, with varying dentitions and head shapes to match their dietary habits.<ref name="Konings2" /> In each case, the radiation events are only a few million years old, making the high level of speciation particularly remarkable.<ref name="Konings2" /><ref name="Konings" /><ref name="Seehausen" /> Several factors could be responsible for this diversity: the availability of a multitude of niches probably favored specialization, as few other fish taxa are present in the lakes (meaning that sympatric speciation was the most probable mechanism for initial specialization).<ref name="Seehausen" /> Also, continual changes in the water level of the lakes during the Pleistocene (which often turned the largest lakes into several smaller ones) could have created the conditions for secondary allopatric speciation.<ref name="Konings2" /><ref name="Seehausen" />

==== Tanganyika cichlids ====
[[Lake Tanganyika]] is the site from which nearly all the cichlid lineages of East Africa (including both riverine and lake species) originated.<ref name="Salzburger">{{Cite journal |author=Salzburger |author2=Mack |author3=Verheyen |author4=Meyer |date=2005|title=Out of Tanganyika: Genesis, explosive speciation, key-innovations and phylogeography of the haplochromine cichlid fishes|journal=BMC Evolutionary Biology|volume=5|issue=17 |pages=17|doi=10.1186/1471-2148-5-17|pmid=15723698 |pmc=554777 |doi-access=free }}</ref> Thus, the species in the lake constitute a single adaptive radiation event but do not form a single [[monophyly|monophyletic]] [[clade]].<ref name="Salzburger" /> Lake Tanganyika is also the least speciose of the three largest African Great Lakes, with only around 200 species of cichlid;<ref name="Konings" /> however, these cichlids are more morphologically divergent and ecologically distinct than their counterparts in lakes Malawi and Victoria, an artifact of Lake Tanganyika's older cichlid fauna. Lake Tanganyika itself is believed to have formed 9–12 million years ago, putting a recent cap on the age of the lake's cichlid fauna.<ref name="Konings" /> Many of Tanganyika's cichlids live very specialized lifestyles. The giant or emperor cichlid (''[[Giant cichlid|Boulengerochromis microlepis]]'') is a piscivore often ranked the largest of all cichlids (though it competes for this title with South America's ''[[Cichla temensis]]'', the speckled peacock bass).<ref name="Konings" /> It is thought that giant cichlids spawn only a single time, breeding in their third year and defending their young until they reach a large size, before dying of starvation some time thereafter.<ref name="Konings" /> The three species of ''[[Altolamprologus]]'' are also piscivores, but with laterally compressed bodies and thick scales enabling them to chase prey into thin cracks in rocks without damaging their skin.<ref name="Konings" /> ''[[Plecodus straeleni]]'' has evolved large, strangely curved teeth that are designed to scrape scales off of the sides of other fish, scales being its main source of food.<ref name="Konings" /> ''[[Gnathochromis permaxillaris]]'' possesses a large mouth with a protruding upper lip, and feeds by opening this mouth downward onto the sandy lake bottom, sucking in small invertebrates.<ref name="Konings" /> A number of Tanganyika's cichlids are shell-brooders, meaning that mating pairs lay and fertilize their eggs inside of empty shells on the lake bottom.<ref name="Konings" /> ''[[Lamprologus callipterus]]'' is a unique egg-brooding species, with 15&nbsp;cm-long males amassing collections of shells and guarding them in the hopes of attracting females (about 6&nbsp;cm in length) to lay eggs in these shells.<ref name="Konings" /> These dominant males must defend their territories from three types of rival: (1) other dominant males looking to steal shells; (2) younger, "sneaker" males looking to fertilize eggs in a dominant male's territory; and (3) tiny, 2–4&nbsp;cm "parasitic dwarf" males that also attempt to rush in and fertilize eggs in the dominant male's territory.<ref name="Konings" /> These parasitic dwarf males never grow to the size of dominant males, and the male offspring of dominant and parasitic dwarf males grow with 100% fidelity into the form of their fathers.<ref name="Konings" /> A number of other highly specialized Tanganyika cichlids exist aside from these examples, including those adapted for life in open lake water up to 200m deep.<ref name="Konings" />

==== Malawi cichlids ====
The cichlids of Lake Malawi constitute a "species flock" of up to 1000 endemic species.<ref name="Konings2" /> Only seven cichlid species in Lake Malawi are not a part of the species flock: the Eastern happy (''[[Astatotilapia calliptera]]''), the sungwa (''[[Serranochromis robustus]]''), and five tilapia species (genera ''[[Oreochromis]]'' and ''[[Coptodon]]'').<ref name="Konings2" /> All of the other cichlid species in the lake are descendants of a single original colonist species, which itself was descended from Tanganyikan ancestors.<ref name="Salzburger" /> The common ancestor of Malawi's species flock is believed to have reached the lake 3.4 million years ago at the earliest, making Malawi cichlids' diversification into their present numbers particularly rapid.<ref name="Konings2" /> Malawi's cichlids span a similarly range of feeding behaviors to those of Tanganyika, but also show signs of a much more recent origin. For example, all members of the Malawi species flock are [[mouthbrooder|mouth-brooders]], meaning the female keeps her eggs in her mouth until they hatch; in almost all species, the eggs are also fertilized in the female's mouth, and in a few species, the females continue to guard their fry in their mouth after they hatch.<ref name="Konings2" /> Males of most species display predominantly blue coloration when mating. However, a number of particularly divergent species are known from Malawi, including the piscivorous ''[[Nimbochromis livingstonii|Nimbochromis livingtonii]]'', which lies on its side in the substrate until small cichlids, perhaps drawn to its broken white patterning, come to inspect the predator - at which point they are swiftly eaten.<ref name="Konings2" />

==== Victoria's cichlids ====
Lake Victoria's cichlids are also a species flock, once composed of some 500 or more species.<ref name="Seehausen" /> The deliberate introduction of the Nile Perch (''[[Nile perch|Lates niloticus]]'') in the 1950s proved disastrous for Victoria cichlids, and the collective biomass of the Victoria cichlid species flock has decreased substantially and an unknown number of species have become extinct.<ref name="Goldschmidt">{{Cite book|title=Darwin's Dreampond: Drama in Lake Victoria|last=Goldschmidt|first=Tijs|publisher=The MIT Press|year=1996|isbn=978-0262071789|location=Cambridge, MA}}</ref> However, the original range of morphological and behavioral diversity seen in the lake's cichlid fauna is still mostly present today, if endangered.<ref name="Seehausen" /> These again include cichlids specialized for niches across the trophic spectrum, as in Tanganyika and Malawi, but again, there are standouts. Victoria is famously home to many piscivorous cichlid species, some of which feed by sucking the contents out of mouthbrooding females' mouths.<ref name="Goldschmidt" /> Victoria's cichlids constitute a far younger radiation than even that of Lake Malawi, with estimates of the age of the flock ranging from 200,000 years to as little as 14,000.<ref name="Seehausen" />