Data Analysis: Virginia Opossum
Its ancestors evolved in South America, but invaded North America after the formation of the Isthmus of Panama about 3 million years ago. It is the only marsupial considered to be native to North America.
The climate patterns of North America vary across the range of the species.
1. Does the animal exhibit variations depending on where it lives? How could you find out?
2. Phenotypes of two opossums. What differences are observable?
Examine the scatter plots showing phenotypes and latitudes.
Latitude represents the distance from the earth’s equator.
Equator = 0°
3. Caption this graphic. What does the map show?
4. Which plots show evidence that phenotypes differ depending on latitude? Rank each plot from 1 to 5, where 5 is a strong correlation and 1 is a weak correlation. Be able to justify your choices.
5. Based on your rankings, which features show the largest differences based on latitude? Write a short summary paragraph for the data.
Features shown on graphs:
Bergmann's rule is an ecogeographical rule that states that within a broadly distributed taxonomic clade, populations and species of larger size are found in colder environments, and species of smaller size are found in warmer regions.
Gloger's rule is an ecogeographical rule which states that within a species of endotherms, more heavily pigmented forms tend to be found near the equator.
Allen's rule. The principle holds that in a warm-blooded animal species, the limbs, ears, and other appendages of the animals living in cold climates tend to be shorter than in animals of the same species living in warm climates.
6. Which rule is illustrated by these rabbits?
Where would you expect to find each of these rabbits (equator, temperat, or arctic)?
Ecogeographical Rules
7. Summarize what this graphic is trying to show:
A
B
C
A
B
C
Read the abstract from this research. �“Scatter plots of the relationship between phenotypic traits and latitude.”�(An abstract is a summary of an article, usually included at the beginning.)
Explain the first paragraph in a way that a 5th grader could understand.
Phenotypic variation along environmental gradients can provide evidence suggesting local adaptation has shaped observed morphological disparities.These differences, in traits such as body and extremity size, as well as skin and coat pigmentation, may affect the overall fitness of individuals in their environments.
The Virginia opossum (Didelphis virginiana) is a marsupial that shows phenotypic variation across its range, one that has recently expanded into temperate environments. It is unknown, however, whether the variation observed in the species fits adaptive ecogeographic patterns, or if phenotypic change is associated with any environmental factors.
Using phenotypic measurements of over 300 museum specimens of Virginia opossum, collected throughout its distribution range, we applied regression analysis to determine if phenotypes change along a latitudinal gradient. Then, using predictors from remote-sensing databases and a random forest algorithm, we tested environmental models to find the most important variables driving the phenotypic variation.
Explain the second paragraph in a way that a 5th grader could understand.
Explain the third paragraph in a way that a 5th grader could understand.
Source: Pubmed
We found that despite the recent expansion into temperate environments, the phenotypic variation in the Virginia opossum follows a latitudinal gradient fitting three adaptive ecogeographic patterns codified under Bergmann's, Allen's and Gloger's rules.
Temperature seasonality was an important predictor of body size variation, with larger opossums occurring at high latitudes with more seasonal environments. Annual mean temperature predicted important variation in extremity size, with smaller extremities found in northern populations. Finally, we found that precipitation and temperature seasonality as well as low temperatures were strong environmental predictors of skin and coat pigmentation variation; darker opossums are distributed at low latitudes in warmer environments with higher precipitation seasonality.
These results indicate that the adaptive mechanisms underlying the variation in body size, extremity size and pigmentation are related to the resource seasonality, heat conservation, and pathogen-resistance hypotheses, respectively. Our findings suggest that marsupials may be highly susceptible to environmental changes, and in the case of the Virginia opossum, the drastic phenotypic evolution in northern populations may have arisen rapidly, facilitating the colonization of seasonal and colder habitats of temperate North America.
Explain the second paragraph in a way that a 5th grader could understand.
Explain the third paragraph in a way that a 5th grader could understand.
Source: Pubmed
Do you think humans traits can be applied to these rules? �How would you find out?