SEE-U 2000: Exercise 13

## Exercise 13: Do Roads Affect Biodiversity?
Module 13: Habitat Fragmentation

### Your Question

1. What is the effect of roads with different traffic intensity and road surface on leaf-dwelling insect species diversity in desert ecosystems?

### Background

Many researchers have found significant effects of roads in densely forested areas (see Introduction). However, little to no research has been conducted exploring the effect of roads, or any linear barrier, on desert biodiversity.

Given that the desert is such a fragile ecosystem and that roads are easily constructed in deserts, this is a very important question. This problem will only become worse in the near future. The southwestern US, and Arizona in particular, has one of the most rapidly growing human populations and as well as one of the most active home-construction industries in North America. As populations swell, cities sprawl and intact habitats become fragmented. The first ingression of this population growth into the environment is by road creation.

There is a strong possibility that roads will have little to no effect in deserts. These ecosystems do not have a closed forest canopy and have little to no accumulated leaf litter, unlike the northern forests where most of this research has occurred. The shade derived from a canopy and the cover provided by leaf litter and their environmental consequences are often the cues that animals use to evaluate the relative value of an area. You will be among the first to explore this question in a desert ecosystem.

### Objectives

1. Grasp of the influence that linear barriers such as roads have on animal species diversity
2. Understanding that increasing road use may have negative consequences for local biodiversity
3. Better knowledge of basic ecology of desert arthropod fauna
4. Ability to predict the differential impact of roads of varying surfaces and traffic use intensities in desert ecosystems
5. Understanding of the multifarious effects of roads on biodiversity
6. Learn basics of building an insect reference collection.

### Your Assignment

Your assignment is to evaluate, using the scientific method, whether roads affect desert insect biodiversity.

1. Confer with your lab mates:
   1. Formulate hypotheses
   2. Draw up an experimental plan outlining how your group will collect the data to test these hypotheses
2. The field site is in Tucson Mountain Park (TMP), on and around the Sonoran Arthropod Studies Institute (SASI) property.
   1. This site is bisected by a well-used paved road (the Gates Pass Road), and has other less traveled dirt roads
   2. Common small tree and shrub species at this site are that are frequented by leaf-dwelling insect fauna are: Ironwood (Olneya tesota), Mesquite (Prosopis sp.), Palo Verde (Cercidium floridum), Burbush (? Franseria/Ambrosia sp.[?])
3. Insect sampling methods
   Once you have an experimental plan, you will need to implement it. The following insect sampling methods may be used:
   1. First small tree species can be sampled using beating sheets, shrubs using a sweep net
   2. One person beats branches and another aspirates the insects, but not spiders
      1. Priority in collecting: those insects that are quick to escape (homopterans and orthopterans), then ants
      2. All arthropods that are on the beating sheet should be collected
   3. Beating and sweeping efforts should be standardized
      1. Beating: Working quickly—place the 1m x 1m beating sheet under a branch on the tree and quickly beat the branches immediately above the sheet for 10 seconds
         1. The beater should then hold the sheet while the aspirator collects the insects
         2. One beating per tree
      2. Sweeping: with sturdy sweep net, students should quickly sweep entire shrub and collect all insects that are in the sweep net.
      3. All insects that have been collected in the aspirators are then transferred to 70% ethanol vials for later sorting
   4. Sorting (at SASI, in the conference and educational facilities):
      1. Sort the taxa to morphospecies
   5. Create a reference collection
4. Analyze and write-up results, prepare group presentations

Evaluation:

1. Orally summarize your experimental results and conclusions (15 min. max. per group).
2. Participate in discussion of other groups’ presentations. Based on your analyses of other data, do you agree or have additional insights?
3. Submit in your journal answers to the following questions, referring to the experimental results for justification:
   1. How could the effects of roads be mitigated in these ecosystems?
   2. Would it be possible to retain roads, but manage the surrounding habitat differently and thereby reduce the road effects?
   3. What were some of the possible reasons why you observed what you did? How do you think that roads effect biodiversity? What are the proximate mechanisms?

Resource materials:

1. Reference insect collection and other ID materials
2. Rondeau et al. ‘Annotated Flora and Vegetation of the Tucson Mountains’ (spp list, not a field guide)

### Key Skills

1. Increased facility with ecological sampling design
2. Improved skill at constructing biodiversity estimates
3. Competence with conducting rapid biodiversity impact assessment
4. Skill at insect morphospecies determination
5. Ability to sample plant-dwelling arthropods, including familiarity with sweep netting and foliage beating
6. Dexterity with pinned insect preparation for museum collections

### Timetable

1. Total elapsed time to perform the experiment : One very long day or 1.25 Days
   - Day Prior—Late Afternoon (Weds)
     - Lecture
     - Field preparation—Keep lecture and prep short so as not to cut into Ethic Chat time
   - Field Day (Thurs)
     - Travel to TMP, brainstorming, laying out transects and sampling points, insect collection, specimen sorting to morphospecies, data analyses, and oral presentation should all be done in one day
2. Total elapsed hands-on time : approximately 12 hours
   - Day Prior—Late Afternoon (Weds)—1 hr
     - Lecture = 0.5 hour
     - Field prep = 0.5 hr
   - Field Day (Thurs)—11 hrs
     - Drive to TMP / SASI = 2 hours
     - Transect construction = 1 hour
     - Insect collection = 1.5 hours
     - Specimen sorting = 2 hours
     - Data analyses and talk preparation = 2 hours
     - Oral presentation = 0.5 hour
     - Drive back to B2C = 2 hours

### Procedural Notes

1. This experiment builds on many skills that were acquired during the community diversity module (Module 5) and as such, not that much time is necessary to accomplish each step.
2. The estimate of 11.5 hours is likely overgenerous. It is possible that the experiment could take as little as 9.5 hours, if hurried.
3. We need to obtain permission from TMP to use their land for the experiment
4. Potentially, the TAs could come out before the experiment and lay out the transects and mark the trees to be used. This could also happen when the TAs are at B2C to set up the class in middle July.
   - Along the same lines, the TAs could go out and do an initial collection of the insects that we would be collecting, mount them up, and then have a reference collection before the class begins.
   - This would take about two days of work
5. If insect ref collection not created, then need to have other ID materials on hand at SASI
6. Need to develop plant ID sheet for the 4 woody plants to be sampled
7. Instructor and TAs need to remind students of desert field safety night before
8. If students wear insect repellant, will that affect the results of their sampling?

### Materials Needed

1. Dissecting microscopes (SASI has three (?), but we should bring at least 9 more),
   - However, we could also get by with just using hand lenses or mounted magnifying/lamps to do the sorting
2. Sturdy sweep nets (4)
3. Beating sheets (4)
4. Collecting vials, loaded with ethanol—preferably clear plastic snap cap tubes (cheap and easy to use)
5. Sorting trays (petri dish lids—10)
6. Soft forceps (10)
7. Measuring tape, 150 m long (2)
8. Field-appropriate gear (clothing, food, water, etc.)
9. Field identification sheet/guide for woody plant species to be sampled
10. Reference insect collection, or other ID materials

Authors: J. Danoff-Burg, T. Kittel
Revision date: 5 June 2000