Malawi Cichlids - University of Maryland College of...
Transcript of Malawi Cichlids - University of Maryland College of...
MALAWI CICHLIDS SARAH ROBBINS BSCI462 SPRING 2013
CICHLIDS
Family of fish within the infraclass Teleostei
Over 1600 species discovered, Up to 3000 species predicted
Most commonly found in Africa and South America
Popular in freshwater aquariums, also used as a food source
AFRICAN RIFT LAKES
Found in East Africa’s Great Rift Valley
3 Lakes with Genetically distinct Lineages – Lake Tanganyika, Lake Victoria, and Lake Malawi
Lakes are less than 1 million years old (Smith et. al. 2003)
Cichlid populations in the lakes are genetically divided on very small geographic scales (Streelman et. al.2004)
Environmental stochasticity is common and may be a driving force behind speciation and hybridization in the lakes (Streelman et. al. 2004)
GENETIC CLUSTERS From Loh et. al. (2013)
EXPLOSIVE SPECIATION
Ideal Model
System for
Rapid Adaptive
Radiation
More than 500
species each in
Lake Victoria
and Lake
Malawi
Occurred in 3
bursts
Danley and Kocher (2001)
Stages of Malawi Radiation
CONVERGENT
EVOLUTION
Convergent evolution
between Lakes Malawi
and Tanganyika shows
that cichlids solve
ecological problems in
similar ways (Albertson
2006).
SEXUAL SELECTION
Male-male competition: defense of a mating area
Female choice of bright color patterns
SEXUAL SELECTION
Male-male competition: defense of a mating area
Female choice of bright color patterns
SEX REVERSAL
Recruitment of novel sex
chromosomes to maintain sexual
color dimorphism
Resolution of conflict between sex
determination and maintenance of
color pattern
Example from Roberts (2009): OB
Phenotype
SPECIATION IMPLICATIONS
Novel Sex Determiners may lead to reproductive isolation
From Roberts (2009)
HYBRIDIZATION
Hybridization may
explain high levels of
genetic diversity
within populations
and an increased
number of
speciation events.
Smith 2003:
Hybridization
between two
geographically
isolated
populations led to
an intermediate
species in an area
that was between
the two
populations.
CONSERVATION
THREATS
Overfishing presents a
significant threat to
maintenance of cichlid
populations in the wild
FUTURE DIRECTIONS
Comprehensive study of speciation mechanisms in
cichlids
Genetic basis of pigmentation variation
Sex Reversal vs. Sexual Selection
Conservation efforts to preserve species with rapid
population loss from overfishing
Stricter regulations on fishing
Increased species awareness
Male-biased conservation of highly colored species
LITERATURE CITED
Streelman JT, Gymrek SL, Kidd MR, Kidd C, Robinson RL, Hert E, Ambali AJ, Kocher TD. 2004. Hybridization and contemporary evolution in an introduced cichlid fish from Lake Malawi National Park. Molecular Ecology. 13: 2471-2479.
Lande R, Seehausen O, van Alphen JJM. 2001. Mechanisms of rapid sympatric speciation by sex reversal and sexual selection in cichlid fish. Genetica. 112-113:435-443.
SmithPF, Konings A, Kornfield I. 2003. Hybrid origin of a cichlid population in Lake Malawi: implications for genetic variation and species diversity. Molecular Ecology. 12: 2497-2504.
Roberts RB, Ser J, Kocher TD. 2009. Sexual conflict resolved by invasion of a novel sex determiner in cichlids. Science. 326: 998-1001.
Danley P, and Kocher TD. 2001. Speciation in rapidly diverging systems: lessons from Lake Malawi. Molecular Ecology. 10: 1075-1086.
Albertson RC, Kocher TD. 2006. Genetic and Developmental Basis of Cichlid Tropic Diversity. Heredity. 97: 211-221.
Genner, MJ and Turner GF. 2005. The mbuna cichlids of Lake Malawi: a model for rapid speciation and adaptive radiation. Fish and Fisheries. 6: 1-34.
Knight ME, Van Oppen MJH, Smith HL, Rico C, Hewitt GM, and Turner GF. 1999. Evidence for male-biased dispersal in Lake Malawi cichlids from microsatellites. Molecular Ecology. 8: 1521-1527.
Loh YH, Bezault E, Muenzel FM, Roberts RB, Swofford R, Baluenga M, Kidd CE, Howe AE, Di Palma F, Lindblad-Toh K, Hey J, Seehausen O, Salzburger W, Kocher TD, and Streelman JT. 2013. Origins of shared genetic variation in African cichlids. Mol Biol Evol. 4: 906-917.
PICTURE SOURCES
http://www.cichlids.com/uploads/tx_usercichlids/user_pics/35
84/039_jp_6a453b2f5c.jpg
http://www.nhnz.tv/images/NHNZ%20Programs/LifeForce-
factAF-map.jpg
http://upload.wikimedia.org/wikipedia/commons/thumb/7/7e
/Oreochromis_tanganicae_%28G%C3%BCnther%29.jpg/800px-
Oreochromis_tanganicae_%28G%C3%BCnther%29.jpg