Download Explosive Speciation

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