A natural history thought: box turtles and paw-paw trees
October 23, 2011
Posted by on
I had this thought the other week. I was looking through a field guide on trees of North America. I was looking at the range of where paw-paw trees grow (Asimina triloba). Paw-paws are medium-sized understory trees that are common throughout most of the eastern United States. They have large banana-like leaves and a mango-sized fruit with a sweet, custard-like flavor and texture. The genus Asimina is a group of trees much more common in tropical forests. However, there are a few species of this edible fruited tree that is native to temperate forests of the eastern United States. It’s western range extends from Southwest Michigan down to about a few hours North of the Gulf; its northern range extends from Southwest Michigan down through central Ohio and central Pennsylvania, and on its eastern range down to Northeast Georgia. They are well prized for their non-so-coincidentally tropical tasting fruits that come in early fall.
Earlier that day, I was also looking at the range map for the Eastern Box Turtle (Terrapene carolina carolina). If I had remembered correctly, the range map for the eastern box turtle was nearly the same as it was for the paw-paw tree. I immediately flipped open my field guide on North American reptiles and amphibians and glanced at the range map for the eastern species of the box turtle. It ends up I was right!
My next question was: Is there a relationship with eastern box turtles and paw-paw trees. Looking at the two maps, and knowing a bit about the box turtle’s habitat, I thought that it may be possible that there is a relationship among these two forms of life. Paw-paw trees are common in eastern mesophytic forests. The word mesophytic refers to the moisture and acidity of the soil (the dirt) in these types of forests. Mesophyic forests are middle ground in terms of how wet the soil is and how acidic or basic the soil is. The range of these types of forests matches the range with the paw-paw tree and for the most part, the range of the eastern box turtle. In Michigan, paw-paw trees and eastern box turtles are most common in the Southwest portion of the state – this is where the northernmost area of eastern mesophytic forests are.
So what then, brings paw-paw trees and eastern box turtles together? Well, I’m not sure. To be honest, I am not even really sure there is a close relationship between these two things. One of the characteristics about natural history versus laboratory biology is that you sometimes have to develop hypotheses without having all of the formalized data and observations you would need. This sort of science is neither perfect nor precise. Rather it keeps the mind thinking and it deepens the connection one has with the natural world. Even if my hypothesis that there is an ecological relationship between paw-paw trees and eastern box turtles ends up being a meaningless statement, then at least I can say it was worth the thought.
Paw-paw trees form a canopy over a trail through a forest in Southern Maryland.