The honey locust, Gleditsia tricanthos, occurs both east and west of the Mississippi River valley in the U.S. from Minnesota to Pennsylvania to Louisiana. In addition, thornless cultivars of honey locust are widely used as ornamental trees in both suburban and urban areas in most of the 48 contiguous states.
Making identifications is a common task in field biology. We need to discriminate between different organisms in the field in order to communicate effectively about them. Some organisms are familiar because we have observed them many times before, but a surprising number of organisms appear "new." To make matters more complicated, the organisms under study in the field should be identified by their scientific names. Even if you are able to associate an organism with its common name, this might only be slightly helpful in identifying which species it actually belongs to.
Field guides and dichotomous keys emphasize the distinctive, yet commonly encountered features of each species. Illustrations in field guides serve as standards or type specimens that can be compared to an unknown specimen. Keys are used to make an identification based on the matching of serially described traits to the specimen.
What field guide or key will you be using? Why did you choose it?
List the features that you will use to identify this tree.
Provide an illustration that you could use for identification
and label the key features.
The reductionistic approach that works well for identification of species can be counterproductive for other kinds of observations. You may tend to dismiss differences between individuals of the same species because you are concentrating on their commonly held features. The variability you encounter in a population or within a single organism should be noted. Your research experiences in the field require these kinds of observations as well.
Examine the leaves of a honey locust.
What are some differences between them?
Here are two images of honey locust leaves taken during early June on the Beloit College campus in Wisconsin.
The difference between the leaves is easily observed. Honey locust trees produce both once-compound (pinnate) and twice-compound (bipinnate) leaves.
Describe how you would go about investigating leaf
production in the honey locust.
What kinds of visual evidence could you collect?
Could you use herbarium specimens as well as living specimens?
Here are some questions past students have addressed:
Do other honey locusts exhibit varying leaf forms?
Is the form related to the leaf position?
Is this a response to an environmental stimulus?
Why are only some of the leaflets affected?
Could the production of different leaf forms be helpful?
Describe the question you have investigated concerning
leaf development in the honey locust.
What conclusions have you reached?
Produce a poster or a web page that could be used
to support your conclusions to your peers.