Lecture 10.Wednesday, September 17.
1.Biogeography - Why do things occur where they do? Needlefish distribution is strongly influenced by temperature
Needlefish distribution is strongly influenced by temperature.Occur in water above 23.9C. However - not all species occur in all places. Gondwanaland Distribution Example 1 - Cichlids Gondwanaland Distribution Example 2 - Characiformes Gondwanaland Distribution Example 3 - Osteoglossids Lungfishes Distribution thought to reflect Gondwana connections of southern continents One the classic examples of supports the Gondwanaland super-continent Lauratian Distribution Example #1 - Percidae Lauratian Distribution Example #2 - Esocidae Cypriniformes, Catostomidae
13 genera 70 species Lauratian Distribution Example #3 - Cypriniformes
53 genera 286 species Gondwanaland Distribution Example 1 - Cichlids Cichlidae - 900 species in African rift lakes = species flocks
L. Victoria In NA Great Lakes, 230 total speices - all orders/families Evolve when a new habitat with open niches is invaded In this case these lakes formed, there were no fish in them, once a single type of fish moved there was explosive speciation Molecular Clock Data Indicate that Cichlids diverged after breakup of Gondwanaland Group Activity #1 -Draw the phylogenetic tree & distinguishing
traits for: group a - Myxiniformes, Gnathostomata, Chondrichthyes, Osteichthyes group b - Petromyzontiformes, Elasmobranchii, Holocephali, Sarcopterygii, Actinopterygii group c - Elasmobranchii, Holocephali, Sarcopterygii, Actinopterygii group d - Myxiniformes, Petromyzontiformes, Chondrichthyes, Sarcopterygii Group Activity #3 - Design a dichotomous key that would allow one to distinguish these groups
For example . . . Step 1 - lacks vertebrae--> Myxiniformes if not --> go to step 2 Step 2 - lacks jaws --> Petromyzontiformes if not --> go to step 3 Review Questions: 1.Distinguish between the Intrinsic Limitations hypothesis versus the Vicariance hypothesis for the distribution of fish.What assumptions do each make concerning dispersal? 2.List 2 major geological factors that can affect fish distributions.How does glaciation affect fish distribution? 3.List 4 taxa that show a Gondwanaland distribution.Which ones have clear-cut fossil support?List 3 taxa that show a Lauration distribution. 4.What were the 3 hypotheses for explaining the distribution of cichlids?What evidence is there to support (or reject) each one?How did scientists calibrate a molecular clock for cichlids?How did they use it to estimate the origin of cichlids?Do you think it likely that cichlids migrated between Africa & South America?What is neutral DNA? 5.Speculate on the relative roles of vicariance versus dispersal for marine versus freshwater fish.Do you think their relative importance differs between saltwater and freshwater fish?What evidence does your book present on this matter?