1. Background 2. Continental drift and Glaciations 3. Zoogeographic areas 4. Methods / Tests Lecture 13 Zoogeography
1. Background
2. Continental drift and Glaciations
3. Zoogeographic areas
4. Methods / Tests
Lecture 13 Zoogeography
• Geographic distribution of animals past and present
• The challenge is to discern patterns among current distributions of taxa and how these patterns relate to their evolutionary history
• We will look at how and why different fishes got to where they are today
Lecture 13 Zoogeography
Alfred Russel Wallace (1823-1913)
The Malay Archipelago20 April 1854 (arrived in Singapore) - 1 April 1862
Zoogeography- father of biogeography
Wallace’s line
Wallace was the first to realize that distribution of related species is fundamentally linked to geologic history of places the species inhabit
Wallace’s line
The Formation of Zoogeographic Regions
Two main hypotheses:
• Dispersal
• Vicariance
DISPERSAL
1. Start with one continuous population. Then, a colonist floats to an island on a raft.
2. Finish with two populations isolated from one another.
Island
Continent
VICARIANCE
1. Start with one continuous population. Then a chance event occurs that changes the landscape (river changes course).
2. Finish with two populations isolated from one another.
River
River changes course
Continental Drift
Continental Drift
• Current arrangement of continents creates barriers among marine species
• Can separate populations of freshwater fishes
Continental Drift
Continental Drift
Glaciation
Glaciation
• Glaciations result in lower sea levels, which changes the dynamics of currents and ultimately gene flow
• Temperate fishes were massively displaced by glaciation• retreating glaciers left behind postglacial
lakes
Glaciation
120m below current sea level
Glaciation
Esocidae (pikes and muskie)
Glaciation
Glaciation
speciation events coincide with sea level lows
Parrotfishes(Scaridae)
Marine Zoogeographic Regions
Four major zones
1. Indo-West Pacific
2. Western Atlantic
3. Eastern Pacific
4. Eastern Atlantic
Marine Zoogeographic RegionsIndo-West Pacific
• ~3000 spp.
Contains coral triangle
Marine Zoogeographic RegionsIndo-West Pacific
coral triangle
• global maxima of marine biodiversity• ~500 spp of reef building coral (10x the amount in the
western Atlantic)• number of taxa decrease as one proceeds eastward
across Pacific plate
Marine Zoogeographic RegionsIndo-West Pacific
Marine Zoogeographic RegionsWestern Atlantic
• ~1200 spp.
Marine Zoogeographic RegionsWestern Atlantic
Marine Zoogeographic RegionsWestern Atlantic
Amazon river divides coral reef fish fauna into northern and southern parts by freshwater outflow
Bottom trawls underneath the outflow reveal coral reef species assemblage but with sponges
Genetic analyzes reveal there is some connectivity between the North and the South…
Marine Zoogeographic RegionsWestern Atlantic
Marine Zoogeographic RegionsWestern Atlantic
A. bahianus
A. coeruleus
A. chirurgus
Three species of surgeonfishes in the genus Acanthurus were sampled throughout the Western Atlantic basin• genetic connectivity was estimated
The amazon outflow effected geneflow in each species uniquely• strong barrier in A. bahianus
• modest barrier A. coeruleus
• no effect in A. chiurgus
Marine Zoogeographic RegionsEastern Pacific
Marine Zoogeographic RegionsEastern Pacific
• Related to and only recently separated from the western Atlantic around 3 mybp• fewer spp of fishes and corals
• Geminate species
• The eastern Pacific barrier acts as a distance barrier• limits 86% of reef species from central Pacific
Eastern Pacific Barrier
Alva-Campbell et al 2010
Holacanthus Distribution
Geminate Spp.?
H. tricolor
H. bermudensis
H. ciliaris
H. clarionensis
H. limbaughi
H. passer
H. africanus
1/100
1/1001/100
1/100
1/97
1/99
1/100
1/98
1/100
1/100
9.0 8.0 7.0 6.0 5.0 4.0 3.0 2.0 1.0 0.0
Mya
TWA
TEP
HTR_PAN_050704
HTR_CABR_020601
HBE_MKF_080701
HBE_MKF_110701
HCI_CABR_020601
HCI_MKF_080701
HCL_APA_050701
HLI_CLI_041001
HLI_CLI_041002
HPA_MUE_061202
HPA_MUE_061201
HAF_CVE_0999289
FIGURE1
0.9
Tariel, Longo, & Bernardi 2016
Holacanthus RADseq Phylogenygeminate sister clades
Vicariance or dispersal?
Marine Zoogeographic RegionsEastern Atlantic & Mediterranean
Marine Zoogeographic RegionsEastern Atlantic & Mediterranean
• Sparse coral cover in the tropical Gulf of Guinea
• Depauperate in spp (~ 600)
• After completion of Suez Canal, Lessepsian migrants have begun to invade the Mediterranean
After completion of Suez Canal, Lessepsian migrants have begun to invade the Mediterranean