lecture 13 zoogeography - university of california, santa cruz...2016/08/15  · 4. methods / tests...

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