Field and Laboratory Research  

Other Research Questions 

References

Modifications of Research Exercise 

This research exercise was originally designed for the freshman Chemistry-Biology Laboratory at Juniata College, Huntingdon PA, but it can be easily modified for use in upper-level courses in general ecology, aquatic ecology, limnology, animal ecology, invertebrate zoology, behavioral ecology, evolutionary ecology, or evolutionary biology. 

The first laboratory session can be expanded to include a comparative study of two or more springs.  For example, one can examine the effects of various environmental factors (e.g., water chemistry, velocity, substrate, macrophyte coverage, presence/absence of vertebrate predators, etc.) on macroinvertebrate population sizes and assemblage composition.  In fact, this approach has been applied successfully in the junior-level General Ecology Laboratory course at Juniata College.  Similar comparative studies can also be carried out on the flora of springs.   Furthermore, in springbrooks one can undertake longitudinal surveys of the fauna and flora in relation to changing water temperature and/or other environmental conditions.  Keep in mind that the ecology of springs in North America is little known so even basic ecological surveys of springs in your area would be valuable additions to our knowledge. 
 

 

The section on phylogenetic analysis can be altered to include other taxa besides animals.  And it can be made much more sophisticated, as well.  A wide variety of techniques can be explored using the computer program PAUP 4.0 or other available phylogenetic analysis software (e.g., MacClade, Phylip, Component, Hennig 86, and MEGA; see also Equipment and Materials page). 

The sexual selection portion of this exercise can be changed in many interesting ways, too.  For example, one can allow students to construct their own hypotheses, rather than have them test ones already formulated by their instructor.  Many other amphipod traits besides body length can be examined: e.g., body mass, body color, developmental asymmetry, parasite load (e.g., Ward, 1986; Zohar and Holmes, 1998), size of the gnathopods (which are used by males to hold onto females during amplexus; e.g., Wellborn, 1995), etc.  Recent work on assortative mating and amplexus duration in amphipods and isopods suggests that much of interest can be learned by focusing on female traits, and not just on male traits (e.g., Hatcher & Dunn 1997; Jormalainen, 1998).  One can also examine effects of various sensory, social and environmental factors on amplexus behavior (e.g., mate/predator odors, microhabitat differences, water velocity and population sex ratio; e.g., Lyes, 1979; Ward, 1986; Adams et al., 1989; Ward and Porter, 1993; Wen, 1993; Dick and Elwood, 1996; Mathis and Hosack, 1997; Dunn, 1998), and the interaction of sexual selection with other types of selection: e.g., predatory selection that favors shortened amplexus behavior (Strong, 1973) and small body size (Newman & Waters, 1984; Glazier et al. 1992; Culver et al., 1995; Wellborn, 1995).  The effects of predatory selection can be examined wherever springs with and without fish predators are available (as in Pennsylvania and West Virginia). 

Evidence for sexual selection can be sought in the laboratory, as well as in the field.  One can make simple behavioral observations to test whether large amphipod males out-compete smaller males for females, and whether males prefer larger females.  To do this, collect several amplexing pairs of amphipods.  Separate each pair and measure the length of each male and female.  (Note: paired amphipods can be easily separated without harm by holding them in your hand for a few seconds.  Amphipods do not like warmth and quickly separate to escape this stress.  Only previously paired animals are used in the tests to insure that they are reproductively active).  Then put one male and two females of different length in each of several containers of spring water .  Also in each of several containers put one female and two males of different length.  Observe after one to two days to see who paired with whom! 

This behavioral experiment is a lot of fun for students, and it also exposes them to another kind of statistical test, namely the chi-square test.  Thus, adding this experiment to the present exercise introduces students to all three of the major kinds of statistical tests; those dealing with differences, correlations, and frequencies. 

Finally, the sexual selection component of this exercise can be done with aquatic sowbugs (isopods), if amphipods are not available.  Isopods are also sexually dimorphic, practice precopulatory guarding, and are abundant in many kinds of freshwater habitats. 

Overall, the present exercise is very flexible and can accommodate endless modification in terms of research questions asked, and it can be carried out at any time of the year, wholly or in part, wherever there are freshwater springs or springbrooks available for study. 
 

Independent Research Projects  
 
At Juniata College, many undergraduate students have used the amphipod-spring system to develop their own independent research projects.  These projects have included studies of intraspecific life-history variation, habitat selection, the physiological and ecological effects of water chemistry, inter-population genetic differentiation, the sensory biology of mate attraction, the energetic cost of amplexus behavior, and of various ecological interactions, including size-selective predation, competition, and parasitism (e.g., by the acanthocephalan worm Polymorphus minutus) (see references in Glazier, 1998).  Springs are useful for studying many other ecological and evolutionary phenomena, as well (see also Williams and Williams, 1998).