A STEP IN SPECIATION
The Analysis of Field Observations
Adapted from Investigation 9.4 in Biological Science - An
Ecological Approach (BSCS GreenVersion) 1987, Kendall/Hunt
Publishing Co.
BACKGROUND: The small salamanders of the genus
Ensatina are strictly terrestrial. They even lay their eggs on
land. Nevertheless, these salamanders need a moist
environment and do not thrive in arid regions. In California,
the species Ensatina eschscholtzii has been studied by R.C.
Stebbins at the University of California at Berkeley. This
investigation is based on his work.
PROCEDURE:
PART A – COLLECTION AREAS:
1. Imagine that you are working with Stebbins' salamander specimens, some of which
are pictured on the colored sheets provided.
a. In the list below, the salamanders are identified by subspecies (a subspecies is
a geographically restricted population that differs consistently from other
populations of the same species). For example, the first one is Ensatina
eschscholtzii croceator, shortened to E.e. croceator where "croceator" indicates a
particular subspecies population of Ensatina eschscholtzii.
b. The parentheses after each subspecies name contain a number and a color.
The number is the total of individuals Stebbins had available for his study. The color is
the one you should use for that subspecies when you plot its collection area on the
California map.
c. The letter before the subspecies name indicates the corresponding salamander
picture on the color sheet. For example, E.e. eschscholtzii is picture b on the color
sheet.
Ensatina salamander specimens list
a. E.e. croceator (15; brown)
b. E.e. eschscholtzii (219; red)
c. E.e. klauberi (71; blue)
d. E.e. oregonensis (373; purple)
e. E.e. picta (230; yellow)
f. E.e. platensis (120; green)
g. E.e. xanthoptica (271; orange)
d. You may wonder if there are salamanders in some areas for which you have no
records. You also may wonder if there might be additional subspecies for which you
have no specimens. A biologist faced with these questions would leave the
laboratory and go into the field to collect more specimens. Imagine that you have
done this and returned with the following data:
Additional specimens found at a later time
h. Unidentified population 8 (44; pink)
i. Unidentified population 9 (13; burgundy)
k. Unidentified population 11 (131; turquoise); no pictures available
l. Unidentified population 12 (31; black); no pictures available
Note: Gold colored squares mark where Ensatina were not found
2. A distribution map of Ensatina eschscholtzii in California has been created for you. To the
best of your ability, place the pictures of the salamanders in the correct locations on the map.
3. Use the grid and the pictures to answer the questions on the data sheet.
Biology Unit 1
Part 3 – population genetics
Name: ___________________________
Date ______________Pd: 1 2 6 7 8
A STEP IN SPECIATION
The Analysis of Field Observations – answer sheet
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Discussion Questions:
1. Are the species evenly spread out in the state of California? Explain why or why not based
on the preferred habitat and basic needs of the salamanders.
2. Does the coloration of the salamanders follow a pattern based on geographical location?
Briefly explain the patterns observed.
3. Noting the coloration patterns and the habitat locations of the salamanders, name the
type of isolation occurring in the salamander subspecies.
4. Describe the coloration and location of subspecies E.e. eschscholtzii (specimen b) and E.e.
klauberi (specimen c). Is there any overlap between their distributions? Where?
5. Describe in words or make a colored drawing predicting the appearance of salamander K
based on its location.
6. Stebbins does not consider the unidentified salamanders 8, 9, and 11 as new subspecies.
What is the biological term that describes species K?
7. Why is it unlikely that E.e. picta and E.e. xanthoptica would ever produce offspring?
8. How do the results of the additional collections made in 36Z and 40Z differ from the results in
other places where multiple salamander types are in close proximity to each other?
9. Which specimen on the map could be considered a separate species from E.e. eschscholtzii?
Explain why.
Application:
10. Suppose that an earthquake due to volcanic activity in northern California caused the
western coastline to fall away from the continent forming an island. How would this event
affect the evolution of the Ensatina species?