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Explosive Speciation: Homage to Santa Tanganyika S Division Teleostei Subdivision Euteleostei Superorder Acanthoperygiii ES I ER R PE A. H P OR M CO e rd o 9 rs cichlids embiotocids pomacentrids Pharyngeal jaw morphology = div. of prey types scarids labrids Perciformes, suborder Labroidei ~ 100 spp. ~ 350 spp. ~ 900 spp. •1350 species and 112 genera (Nelson 2006) •2000 species and 200 genera (Greenwood and Stiassny) 1998) •3rd largest family of fishes What are #1 and #2? NOT A Cichlid! ______________ ______________ Why are there so many cichlid species? East African Rift Valley African Great Lakes Tanganyika 9-12 MY OLD Deepest (>1000 m) Tanganyika Fishes 328 SPP*, 215 CICHLIDS, 213 ENDEMICS * Midpoint of estimates from Les Kaufman (2007) VICTORIA < 1 MY OLD largest Shallow Plateau Victoria Fishes 515 SPP*, 450 CICHLIDS, 445 ENDEMICS Malawi 4.5-8.6 MY OLD Malawi Fishes 903 SPP*, 850 CICHLIDS, 845 ENDEMICS Dried up within last 15,000 years! How do 450 cichlids evolve in 15,000 years? (fastest speciation rate ever reported for a vertebrate!) Species Flock: A monophyletic group of distinct ecologically diverse species that have evolved in an isolated macrohabitat. Adaptive Radiation “The greatest example of adaptive radiation known in the animal kingdom” “Had Darwin been collecting fishes in the African Great Lakes, he probably would have had a nervous breakdown” Radiation into feeding niches Cichlid tooth types Maxilla decoupled from suspensorium –more ways to protrude jaws and vary gape, protrusion, biting force, etc. Genyochromis-scale eater, Malawai Haplochromis compressiceps Malawi eye biter ? Haplochromis cyaneus Victorian Zooplanktivore Petrotilapia-Algal Rock Scraper-Malawi Perissodus-Tanganyikan Scale Eater Perissodus microlepis is a cichlid fish with an interesting specialization. They eat scales from other fish and come in two forms. "Left handed" forms attack the right side of fishes and "right handed" forms attack the left side. An interesting adaptation is that the jaws of these fishes are curved to the left or the right depending on which type they are: The victims survive, though becoming wary of attackers from either side. If the population of left-handed scale eaters were to exceed that of right-handed scale eaters, however, the fish would become more wary of attacks from the right side. As a result, the right-handed scale eaters would have an advantage, and their population would increase. These forces ensure that the relative populations of left- and righthanded fish remain roughly equal. This has usually been taken to be an example of frequency dependent natural selection. Field observation on _______________: a unique hunting behavior by the predatory cichlid, Haplochromis livingstoni, of Lake Malawi McKaye (1980) “Tweezer Teeth” Lake Tanganyika Radiation into habitat Mbuna =_________________________ Aufwuchs “Utaka”- Open Water, Zooplanktivores, Lake Malawi Sandfloor Habitats Cyathopharynx furcifer Most are drab! Surf Zone –Tanganyikan “Goby” Cichlids Surf Zone adaptation: _________________ GOBY TILEFISH SUNFISH RED SNAPPER SEABASS JAWFISH TOADFISH WRASSE PARROTFISH SNOOK Tanganyika Cyphotilapia Malawi Crytocara Petrotilapia Petrochromis Which species are most closely related? Common ancestor! Lamprologus, 4 cm Boulengerochromis, 80 cm “Meyer (1993) demonstrated via mitochondrial DNA analysis that the cichlids of Lake Victoria are genetically more similar to one another than they are to morphologically similar cichlids from Lakes Tanganyika and Malawi” Molecular Phylogenetics and Evolution Volume 40, Issue 2 , August 2006, Pages 383-388 Nuclear markers reveal that inter-lake cichlids’ similar morphologies do not reflect similar genealogy Daud Kassama, Shingo Sekib, Michio Horic and Kosaku Yamaokaa, , Convergent Evolution!! Sympatric Speciation Definition: ________________________________ No physical barrier to gene flow—harder to imagine than allopatric speciation Uncommon, but more widely accepted now Gene flow has been reduced between flies that feed on different food varieties, even though they both live in the same geographic area. ALLOPATRIC SPECIATION! Are Victorian cichlids older than 15,000 years? Refugia from Nile Perch? 1 genus, 2 spp., Baikal oilfishes Comephorus dybowskii, little Baikal oilfish 8 genera, 24 spp Other Examples of Flocks •Lake Baikal Sculpins •Great Lakes Whitefishes •Lake Lanao Cyprinids •Why Lakes??? Baikal yellowfin, Cottocompehorus grewingki Cichlid Reproduction I. Substrate spawners II. Mouth-brooders ~ 20% of fish families exhibit parental care Nest site preparation Egg guarding Guarding of fry by both parents •Monogamous and aggressive Tennessee Aquarium, Feb 08 S. American Cichlid Tank Discus •Mucus feeding Neolamprologus brichardi Tanganyikan Cooperative Breeder •Territory defense • clean and fan eggs • clean breeding substrate •Stay for a year •Why???????????? More common in african cichlids Derived Egg mimics Adaptive significance? _____________________ ________ _____________________ •young forage near female •In and out for several weeks posthatching What is going on here? ____________ Cichlid Conservation Issues TILAPIA Aquarium Trade and Aquaculture Efficient Escape and dispersal ability (94 countries) Ecological implications Cichla ocellarus-Peacock bass Nile perch, Centropomidae Introduced into Lake Victoria in the early 1960’s _________________ Lake Victoria’s Endemic Haplochromine Cichlids ~ 445 endemics • Predation • “Other” ecological changes 51 spp. 33 spp. 39 spp. 123 spp. Total global fish extinctions = ca. 285 Approximately HALF are from Lake Victoria The largest modern extinction of vertebrate species ever documented Smoked, not sun-dried •Deforestation •Increased Turbidity and Nutrient Runoff Lake Victoria cichlids Consequences of Higher Turbidity? loss of planktivores + nutrient loading = Nile perch Nile tilapia blue-green algal blooms (and fish kills) Nile Perch Fishery • Lates down •35% decrease 1992-2002 • Foreigners • Most exported, Publix? •Some Victorian Cichlids only exist in aquaria! • Satellite lakes • Rocky areas