Student exercises using “Fishes of the world”
These exercises can be used to supplement what students learn in the lab and/or lecture ( see page xiii). They can be used to have students write a paper (in journal style). They will focus attention on a specific problem while student goes through the classification to address the following topics.
1. LOCAL TAXONOMIC DIVERSITY RELATIVE TO WORLD DIVERSITY
Compare the local diversity (freshwater and marine if relevant separately) as seen in local guides with the total word diversity. E.g., does the local ichthyofauna seem representative of the diversity in the world fauna? Make the analysis at the ordinal and superordinal level.
Find out what is known of the local diversity in fossil fishes. What is the oldest known fossil fish?
2. CHARACTER ANALYSIS
• Make an analysis of the multiple occurrence of , e.g., pelvic fin absence in extant fishes (by going through ordinal/family descriptions).
• In how many of the 515 families is the pelvic fin absent in at least some specimens of some species, and in all species within the family?
• Of the approximately 28,000 species of fishes, in how many species is the pelvic fin absent (either absent in ancestral state or lost)?
• In how many monophyletic (holophyletic) lineages has the pelvic fin been lost?
• What, if any, relationship exists between family size and % of species lacking the fin in actinopterygians? E.g., how does the percentage of actinopterygians lacking the pelvic fins belonging to monotyic families, families with 1-4 species, compare to those belonging to families exceeding 100 species, 300 species? Explanation/testable speculations?
• What if any correlations with other characters exist in pelvic fin absence—e.g., body shape ? Explanation/testable speculations?
3. HABITAT AND SPECIES RICHNESS ANALYSIS
How many of the 453 actinopterygian families have species or some individuals of species in both marine and freshwater habitats. At the family, subordinal, and ordinal level (as an indicator of evolutionary divergence), how much of a zoogeographic barrier do you think the marine or freshwater habitat provides?
4. THE TAXON NUMBERS PUZZLE
Plot the number of species per family using the sequence in the Appendix, pages 469-483 (or some portion thereof) along with any auxillary information you chose with respect to A & B below, and determine (separately for Chondrichthyes and Actinopterygii or some smaller level):
A) the frequency distribution of number of species per family (i.e., how many families have 1, 2, 3, 4, 5 or 1-10, 11-20, etc species). What questions do any “asymmetrical distributions” suggest? Are there any differences between marine/freshwater habitats, superordinal position, etc?
B) the % of families with 50% of the species per order? ). What questions do any “asymmetrical distributions” suggest? [interestingly, as seen from the text, in many families a few genera have 50% or more of the species—is this an artifact or a reflection that some lineages are more prone to speciational events per unit time or have low extinction rates. Attempts by me to find something meaningful here in 1970s after the first edition went no-where—and I could not find the right statistical analysis to show if the observed patterns might be random or not. What can you do?]
5. MAKE A KEY
Making an efficient and fail-safe key using only easily seen external features useful for quick field identification is a difficult task! Try making a key to family level of fishes found in your favorite ocean or continent.
6. PLATE TECTONICS AND FRESHWATER FISHES
Obtain information on plate tectonics. Find some freshwater taxa (subfamily to order level) whose distributions might be explained in terms of plate tectonics. Find some for which dispersal might be a more plausible explanation.
7. MARINE FISH DISTRIBUTIONS
What marine fish families are in the eastern Pacific and the western Atlantic? How might such a distribution be explained?
Joseph S. Nelson. 12 March 2006