Perform
Diversity CalculationsFlower Communities (A Word version to print out is here)
Introduction
This exercise will familiarize you with the insects, spiders, and other invertebrates that inhabit a limited ecosystem; a patch of wild- or garden flowers. In addition, you will record the behaviors and interactions that occur within and among species and the changes in the species and their activities at different times of day. Your data will be collected over a two-three week period, allowing many opportunities for you to view the complex interactions among the species in your plot. Hopefully, you will learn to appreciate the complexity of even a simple ecosystem. The flower community will be compared to a nearby site without flowers (or, in some other way different from the first). As an example, you might choose a patch of Queen Anne's Lace (Figure 1) as the flowered area, and compare this to nearby tree seedlings (Figure 2).
Some of the more-common visitors to this, and other ecosystems, are ants which belong to the insect order "Hymenoptera". They are often seen foraging on the flower's surface; collecting nectar and pollen (Figure 3). Other hymenopterans seen on the flowers include bees and wasps (Figure 4). Dipteran flies may also be seen resting on the flower heads (Figure 5). You may also see coleopteran beetles eating flowers, the leaves, and stems (Figure 6). Grasshoppers (Orthoptera; Figure 7), true bugs (Hemiptera; Figure 8), and lepidopterans (butterflies and moths; Figure 9) also frequent Queen Anne's Lace. At the site in this example some of the flowers have gone to seed and formed a cup-like enclosure. When the sun brightens, small beetles seek refuge from the sun and often duck into the shaded interior (Figure 10).
The inhabitants of the tree seedlings include Japanese beetles (Figure 11, Coleoptera). Most of these animals spend their day feeding on the leaves, while some may be busy courting and mating. At the example site nearly all the Japanese beetles are associated with the seedlings and not with the flowers. Flies (Diptera) also come to rest on the seedlings (Figure 12), but few other insects visit the trees as compared to the flowers.
Methods
Choose two sites: one with flowers and an alternate habitat located close-by. The flowers don't have to be Queen Anne's Lace, but can be any variety (either domestic or wild). You don't need hundreds of flowers for your observations; in fact, flowers occupying only a square meter or so are preferable since you can pay closer attention to a smaller plot.
Choose a second site with non-flowering plants for observation. The alternate site should receive approximately the same sunlight, moisture, and wind as your primary site. In general, you shouldn't choose sites that receive the full heat of the sun over most of the day since many insects will be driven away. However, it is preferable that your site receives full sunlight during some portion of the day. You should also choose sites that are readily-accessible so you can visit at various times. Finally, avoid locations that are likely to be disturbed by human activities (such as lawn-cutting).
Alternately, you can choose a site in an urban area and compare that to one in a rural area or park. It would also be reasonable to compare a site that has been treated with a pesticide vs. an untreated site, or one located near water verses another in a dry location. Check with your instructor for additional ideas.
You will probably have more success if you look for potential sites in the morning since insect activity is likely to be highest at that time. If, after you begin data collection you find few or no insects through most of the day, abandon that site and choose another location. An hour spent checking out potential sites at different times of the day can avoid a lot of false-starts when you begin collecting your data and keeping your journal.
Plan on visiting the sites for 15-20 min a session. Arrange a schedule so sites are visited some time in in morning (say, between 08:00 and 11:00), in the afternoon (13:00-15:00) and in the evening (17:00-20:00). About five hours of observation at each site is required. If your schedule will not allow visits throughout the day, settle on a main time for recording data and fill-in with an early morning, afternoon, or evening recording whenever possible. If it begins to rain during your observation, or there is other significant weather, record this in your log so you can correlate changes in populations and behavior with the weather.
Print out data sheets to take into the field. An Excel spreadsheet for you to print out can be found here (you'll need several copies). If your data sheet doesn't fit correctly on the page, go to the "Print" and "Print preview" menus and set Excel to print the gridlines, fit to page, and landscape mode. The data are later entered into your computer in the worksheet. You don't need to enter the non-numeric data (such as behavioral observations) but don't lose the original field data since you'll need it for the final report. A suggested data sheet in Excel format is shown in figure thirteen. The first and second columns have entries for the date and time. The third column identifies the site (flowers or grass). This is followed by the current temperature and rainfall. You can retrieve hourly weather data for any date range from this link. Be sure to set the station to "Louisville". You can have the data e-mailed to you. The time-date format is year-month-day-time (24 hr clock). Thus, 2008080115 is August 1st, 2008 at 15:00 (3:00 PM).
The
species identifications are common names you make up for insects so you can
recognize them from one day to the next. Thus, names like "big red ant", "green
grasshopper", and "little flies" are acceptable. A sketch in your notebook will
be helpful, at least for showing their size.
If you have a digital camera take pictures of
the various species. The count column is where you
record the number of each species you saw on a particular date and time. If
there are too many to count, estimate the number (perhaps as greater than 50).
It's more important that you describe the behavior than try and count a bunch of
constantly-moving beasties.
VISTA USERS READ THIS TO RUN THE PROGRAMS
Many of your specimens can be identified as to their order by using an identification key (it could be very difficult for some of the larval forms and non-insect species). Identification keys are available on the internet (a good one is here) or your instructor may provide one. You may be able to identify some individuals using the pictures provided with this laboratory. A computer-based key to the insects is available in both PC format and for the Palm computer platform. A picture key to major insect orders is here. Insect anatomy is here. Practice with the above pictures to make sure you see how to use the key or check out the tutorial here. If you are unable to identify an insect to its order, just include it in your report under the name you used. Other arthropods you are likely to see include spiders (Arachnids) and wood lice (Crustaceans; Figure 14).
The last column is used to record the behavior of the animals. Of course, while recording the locations and behaviors of your animals, you should remain relatively quiet (talk in whispers if you have a partner) and should move slowly so you don't scare away skittish creatures like butterflies, dragonflies, and wasps. If you don't sit quietly, many insects won't even visit your site.
In many instances, you may not be sure exactly what a particular insect is up to. In those cases, feel free to guess, or provide a description of the behavior ("the brown bug keeps turning in circles while tapping its legs). If you're looking at a complicated behavior, such as feeding by spiders, describe that in detail (how does the spider handle the prey?). Don't only pay attention to animals visiting the flower heads! Examine the stem, leaves, soil, and other plants in your study area. Record these locations along with the behaviors. If there are numerous animals of the same species all doing different things, list all their behaviors in this column separately. If you run out of room, continue on the back of the data sheet by putting a number in the column on the front and a matching number on the back.
The Report
After two-three weeks, move your numeric data over to a spreadsheet. Figure 15 depicts a sample data set for one site. You will have two such tables (they can be on the same spreadsheet. Starting at cell A2, I listed the species, then the orders under column B. Columns C through F contain the counts of each species over the four-day experiment (you'll have more days). I then had Excel sort the data (including the numbers!) first by order, then by species to organize the data alphabetically.
I then created a column to hold the sum over all days for each species. The earthworms, for example, have a total of 11 individuals while the totals of all species represents 1324 individuals (see yellow highlights). You can use Excel's built-in summation function to calculate the row and column totals.
Finally, for each of the orders I determined the total number of individuals by adding up the counts for all the species within an order. For annelida, that was easy since there was only one species. For the coleopterans we had two species, so their counts were summed (in green highlight; 103 + 61 = 164). For the hymenoptera we had three species and a count of 290. Again, you can use Excel's built-in functions to calculate the totals.
Figure 16 compares the total number of individuals within each order for the two sites. Note that the flower community had more orders represented when compared to the grass community in this example. You should also plot the animals by species that visit each site (Figure 17; Sort by total animal counts and then plot only the top ten species for each site).
Other plots you should attempt are the total number of species at each site by time of day (morning, afternoon, and evening). This will show you if there is a time of day when animals are most active at each site. By plotting the total number of animals at each plot by day you can determine if some weather condition (very warm, rain, etc.) affect the total number of animals that visit each site. Be careful when interpreting these two graphs since the results may be dependent on each other. If, for example, it rained every day that you collected your morning data and you found few animals at that time, you can't be sure that the reduced numbers are because of the time of day, the weather, or some combination of both.
Run the species diversity calculations by comparing the species-mix at each site (Your instructor may also ask you to do the comparisons by time; learn more about the calculations here). Interpret your results.
Describe the behavioral interactions you saw both within and among your species. What behaviors, in general, seemed to be most prevalent? Which behaviors did you find interesting?
Do some species seem to dominate either of the systems? If so, what might be their effect on the system as a whole?
Are there some morphological, physical, or behavioral adaptations that might explain the dominance of one species over another at a particular habitat?
Why were some species found almost entirely in one habitat or the other? What allows some species to occupy both habitats?
Perform
Diversity Calculations
Required Readings
Optional Readings