As human worldwide human activities continue to develop natural lands for human use, conservation programs to conserve natural areas and mitigate development through restoration efforts are becoming increasingly common. In order to evaluate the success of these restoration efforts, scientists have applied a wide variety of techniques to measure the diversity of species occurring in restored areas. Many of these techniques focus on the use of bioindicators – certain organisms whose presence is highly correlated to the quality of the restored habitat. These species – or groups of closely related species – tend to require that specific natural resources are present in their environment, and, if restoration actions successfully increase the amount of these resources that are available, then the bioindicator will also become increasingly common. By focusing on organisms known to be useful bioindicators, studies surveying restored areas can reduce the effort required to determine the success of these restoration projects, allowing more efficient and informative monitoring programs.
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| Figure 1. Camponotus americanus, a member of Subordinate Camponotini, and a species that might occur in similarly conducted samples in the American Midwest. Photo from http://bugguide.net/node/view/328928/bgpage |
Previous studies throughout tropical rainforest and arid regions in northern Australia have found that ants are one such group of bioindicator; Gollan et al. (2011) show that these same methods can also be applied to temperate regions as well. In this study, the researchers selected 12 sites from within a temperate river catchment within a grassland area of southeast Australia. The chosen sites differed in the amount and type of vegetation present, and they were classified into four classes: mature woodlands, older revegetation (7-10 years post-restoration), young revegetation (less than 3 years post-restoration), and unplanted grassland. In each site, the researchers sampled insects using pitfall traps, designed to contain and collect any insects that stumble into them. After classifying the sampled ants according to morphospecies, which group together difficult to distinguish species with similar ecological functions, the researchers compared the number of species present in each of the four classes of site vegetation. Though they identified more than 20,000 ants from 68 different species, Gollan et al. (2011) found that the collection of ant species present at a site varied more within each vegetation class than between sites of different vegetation classes, showing that analyzing ant communities as a whole does not provide much information on the quality of the restored area. However, when they limited their analyses to certain functional groups – groups of morphospecies lumped together by shared interspecific interactions and food sources – they found that different functional groups responded in vastly different ways to habitat quality. In particular, one group known as Subordinate Camponotini, was common in mature woodlands, moderately present in revegetated areas, and absent in unplanted grasslands, as it likely responds to the availability of its food sources in the different types of vegetation.
Despite being shown to be valid bioindicators in a wide range of habitats, analyses of habitat quality through measurement of ant communities has seen limited use in the United States. In proposed research, I am interested in exploring the applicability of this system in riparian areas here in the Midwest. In addition to the effects of agriculture, many rivers in the Midwest have been channelized, and these various control methods have resulted in substantial changes to the flooding patterns these rivers have experienced. As periodic disturbance by flooding is key to maintaining the health of riparian areas, human-induced modifications to flooding history may have had widespread impact on the communities of these riparian areas. In my proposed project, I will sample ants in riparian areas with different flooding histories and compare these communities using the methods of Gollan et al (2011). By looking at diversity of different functional groups, as well as overall diversity, I aim to identify the effects that changes to the flooding regime of rivers in the American Midwest has on the quality of adjacent riparian areas.
Reference:
Gollan, J., L. Lobry de Bruyn, N. Reid, D. Smith, & L. Wilkie. 2011. Can ants be used as ecological indicators of restoration progress in dynamic environments? A case study in a revegetated riparian zone. Ecological Indicators 11: 1517-1525.
If you were to do such a project, would you include some sort of "control" or "restoration target" communities for the sake of comparison? What if those are mostly gone, because riparian areas have been so powerfully disturbed?
ReplyDeleteI wonder if historical ant collections in natural history museums might be helpful. Meg Schmitt, a student in BIO 305 ("Evolution of the Iowa Flora") a few years ago, estimated the plant community structure of a local remnant prairie, using historical Grinnell College Herbarium specimens. Her data closely resembled the structure of a larger prairie sampled by other researchers in a single year.
How are you defining "quality" of the adjacent riparian areas? (i.e. what forms of biodiversity from McGill et al. (2015) would you be considering in your analysis?) Perhaps the type of quality/biodiversity you're interested in will help you find what bioindicator is most appropriate to use for your study.
ReplyDelete^Just a possible suggestion, not saying ants are a bad bioindicator
Sounds like a fascinating endeavor—I appreciate the focus on riparian zones and the potential implications of your work in addressing watershed health and quality.
ReplyDeleteBut I am curious to know if you plan to “standardize” your riparian zones of interest? You mention you will be looking at channelized areas and thus sites with different flood histories, but would your examination encompass zones that are near urbanized areas and those that are more rurally located? If so, do you believe neighboring land usage might have a stronger effect on the communities of ants found? Perhaps having a more extensive “checklist” of the properties you are looking for in your riparian areas might help limit your spatial scale of analysis. You mention that you wanted to examine the Midwest, but that might prove to be quite a herculean task (“that’s a lot of ground to cover”) :-).
In addition, has there been previous research on post-flood recovery of ants or invertebrates in general? How rapidly are they able to recover?
The paper you site for this blog post has given some insight to the use of ants as bioindicators. However, the study also used ants within woodlands and grasslands, the river catchment assumed more resistant to flooding than the highly-channelized rivers in the Midwest.
ReplyDeleteGiven the disparity between Gollan's research site and your own, do you believe that ants will still be a useful bio-indicator, especially as below-ground dwelling arthropods whose habitat may be destroyed by a flooding event? As mentioned in previous comments, the selection of spatial scale over which you sample will be very important here, for example, habitat directly within flooded area vs. habitat adjacent to flooded area where the ecosystem may still be impacted as a result of that flooding. Have there been any species examined within the context of flood research in previous work?
Being able to make accurate comparisons between sites not located on a gradient (i.e., which may differ in many aspects other than flooding) will be quite the challenge!