Lecture 21 - Pleiostocen glaciation

1. Continental vs. Oceanic Islands

• Continental islands (historical contact with continental land mass)

– Sri Lanka-India, New Guinea/Tasmania-Australia, British Isles-

Europe, Trinidad-Venezuela

• Oceanic islands – resident fishes or their ancestors must have been derived from marine fishes or sufficiently salt-tolerant (arose from ocean)

– New Zealand

– Hawaiian Islands

– Galapagos Islands

– Bermuda (complete absence of ostariophysans and other

primary FW fishes)

2. Stability over Geological Time

• e.g., eastern coastlines of SA and NA relatively stable, with little or no tectonic activity and less extreme climatic and geological conditions

• Has resulted in much larger inland fish faunas

3. Stream Capture

• Geological changes in drainages over time

– e.g., action of water can lower divide between stream courses until one becomes diverted or captured by another

• Can transfer aquatic fauna into a new drainage

– In upland areas, transfer usually occurs in one direction

– In lowland areas (e.g., marshes and wetlands), transfers can go both ways because there are fewer barriers to movement

4. Changes in Seal Level

• Coastal rivers can be joined due to lowering of sea levels

– Rivers once isolated from each other by marine or estuarine conditions

– Can join farther out on the continental shelf if sea level lowered

• Lowering of sea levels can connect formerly separate landmasses (e.g., across Isthmus of Panama and Bering Strait)

• Most frequently related to glaciation

5. Pleistocene Glaciation

• Most important factor affecting fish distribution in Canada

• Ice covered much of northern NA and Eurasia at least 4 times during last 1.7 my

• Fish perished or were pushed (largely) southwards as glaciers advanced

Wisonsin Glaciation

• Laurentide and Cordilleran ice sheets in Canada and northern USA (Alaska largely ice free)

• Fish pushed into one or more glacial refugia

• At least five or six refugia in North America

• Mississippi most significant refuge/refugium in terms of number of species and geographic area recolonized

– e.g., of 91 FW fishes in Ontario, 72 spp. recolonized from Mississippian refugium (Mandrak and Crossman 1992)

Recolonization

• Fish reinvaded as glaciers retreated northward

• During deglaciation, enormous volumes of water produced, which gave way to temporary glacial lakes (e.g., Glacial Lake Agassiz) and spillways

• Drainage divides were often inundated and watersheds temporarily connected by large meltwater lakes, providing opportunities for fish to disperse from refugia into newly deglaciated regions

• The Laurentian Great Lakes are the result of glacial scour and pooling of meltwater at the rim of the receding ice

• Niagara Falls also a product of Pleistocene glaciation

Postglacial colonization of Manitoba

• MB completely covered by the Laurentide Ice Sheet until approx. 11,000 years ago

• Glacial Lake Agassiz (meltwater lake) covered much of MB as ice melted ca. 11,000 – 7800 years ago

– Its discharge and inflow channels provided routes for fish to enter MB from glacial refugia

– Then spread through the lake or its marginal waters

• e.g., Lake Agassiz discharged into Mississippi River through Minnesota Spillway and into precursors of Lake Superior and Lake Michigan, and then into the Mississippi River

1st time intervals in which Manitoba’s FW fishes arrived

Cold-water species which colonized MB as the Laurentide Ice Sheet melted (during glacial recession)

– Species typically widely-distributed across Canada

– e.g., lake trout, brook trout, Arctic grayling likely passed through during deglaciation

– Also, at least some fish that survived glaciation along east coast of NA probably followed Arctic Ocean and Hudson Bay coastline as it emerged from the melting ice (e.g., Arctic charr, threespine stickleback)

• Accounts for 36/91 species of fishes that spawn in FW in MB

2nd time intervals in which Manitoba’s FW fishes arrived

Fishes that reached MB after the Laurentide Ice Sheet melted and Lake Agassiz had drained into Hudson Bay (during postglacial times)

• Accounts for 43/91 species (Table II)

4000 years ago

Time when connections between north and south basins formed in Lake Winnipeg which formed 7700 years ago

Lake Winnipeg basins

• East side/south basin of Lake Winnipeg overlies western boundary of the Canadian Shield

• South basin turbid

• West side/north basin is in prairie region and is underlain by flat-lying Paleozoic limestone beds

– Lacks clay sediments deposited by glacial Lake Agassiz, making north basin clear and relatively cool

6 refugia in North America

• Mississippi

• Missouri

• Atlantic

• Pacific

• Beringia

• Nahanni

Biogeogrpahic zones

1. Nearctic

2. Paleoarctic

3. Middle America

4. Neotropical

5. Oriental

6. Ethiopian

7. Australian

1. Nearctic

Part of Holarctic

• Centrarchidae and Ictaluridae

• Percopsiformes (Percopsidae, Aphredoderidae, Amblyopsidae)

• Fundulidae and Cyprinodontidae (euryhaline)

• Relict groups of archaic fishes (e.g., bowfin, gars, hiodontids – although fossil bowfins in Europe, Asia, SA; fossil hiodontids in northeastern Asia

• With some exceptions (e.g., northern pike), differences at species level

2. Palearctic

Includes temperate Asia (part of holarctic)

– e.g., two endemic cottoid families in ancient Lake Baikal

• And shares number of FW families with tropical Africa and Asia

– e.g., families (e.g., Cobitidae, Anabantidae, Channidae, Mastacembelidae, Clariidae) perhaps derived from fish carried on the Indian landmass from Africa to Asia and then into temperate Asia and, in some cases (e.g., loaches) in Europe

– Siluridae and Balitoridae also shared by Oriental and Palearctic regions

3. Middle America

• Central American and southern Mexico

• Interesting mix of North (e.g., centrarchids, cyprinids, ictalurids) and South (cichlids, characids, pimelodids) American faunas with local endemism (Goodeidae, Profundulidae, Poeciliidae, Anablepidae)

4. Neotropical

• SA isolated for some time prior to connection to Middle America

• Separated from Africa ca. 112–150 mya

• Richest in Characiformes (with several endemic families) and Siluriformes (likewise); also many cichlid and gymnotiform spp.

– Characiformes and Cichlidae shared with Africa, but fauna of each continent appear to be monophyletic

• Other Neotropical families closely related to marine groups and probably evolved in inland shallow seas and large lakes of the region

– e.g., Pomatotrygonidae, Clupeidae, Engraulidae, Belonidae, Sciaenidae, Soleidae

• Species rich (ca. 8000 spp. of FW fishes)

5. Oriental

 Land connections to Palearctic and Ethiopian regions

– Although Himalayas form boundary to the north, dry areas of the Middle East form boundary to the west

• Rich in ostariophysan fishes, esp. cypriniforms and siluriforms

• Several endemic catfish families

• Other shared families include Synbranchidae, Mastacembelidae, Channidae

6. Ethiopian

• Africa (except Atlas mountains), Madagascar, and southern 2/3 of Arabia

• Almost entirely surrounded by ocean

• Endemic families include archaic families of primitive bony fishes:

– Protopteridae and Polypteridae

– Pantodontidae

– Gymnarchidae and Mormyridae

• Other endemic families include Malapteruridae and Mochokidae (Siluriformes)

• Estimated 2500–3000 spp

7. Australian

• Only ca. 200 FW spp.

• Most in families that are largely marine or estuarine (e.g.,cgobies, atherinids, catfishes)

• Or diadromous (e.g., lamprey families Geotriidae,cMordacidae) and galaxiids

• Plus three archaic FW fish spp.

– Australian lungfish

– Two osteoglossids (Scleropages spp.)

• Major groups of continental FW fishes lacking (minnows, loaches, catfishes, anabantoids, channids)