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Use of Macroinvertebrates to Identify Cultivated
Wetlands in the Prairie Pothole Region

Results


Comparison of Wetland and Upland Samples

Field Samples.  We identified 46 categories of invertebrate remains in our field samples (Table 1), 6 of which were used in our simplified taxonomy (Table 2). Average values of taxon richness and LogCount for field samples differed markedly among the three habitat types (upland, temporary wetland, seasonal wetland) regardless of whether or not weighting was done or if the simplified taxonomy was used (Table 3). When unweighted, taxon richness (F2,60 = 26.21; P < 0.0001) differed among the three habitat types with both wetland types being similar to each other (P = 0.34) but not (P < 0.0001) to the upland. The unweighted LogCount (F2,60 = 17.85; P < 0.0001) also differed by habitat type with wetland types differing from upland (P < 0.0001) and marginally from each other (P = 0.058). Taxon richness for the weighted samples also differed among habitat types (F2,60 = 32.41; P < 0.0001), with both wetland types being fairly similar to each other (P >0.09) but not to the upland (P < 0.0001). The weighted LogCounts also differed by habitat type (F2,60 = 21.06; P < 0.0001), but each was statistically unique (P < 0.03). Using the simplified taxonomy, each of the habitat types were statistically unique, with both taxon richness (F2,60 = 26.93; P < 0.0001) and LogCount (F2,60 = 26.04; P < 0.0001) differing among the three habitat types.

Table 1.  Evidence type used, habitat affinity (HA), frequency of occurrence (F), and mean count of taxa in field samples from upland sites, temporary wetland sites, and seasonal wetland sites.  OW = Obligate Wetland, FW = Facultative Wetland, FA = Facultative, FU = Facultative Upland, OU = Obligate Upland.
Taxon Evidence Type HA Upland Temporary Seasonal
F(%) Mean F(%) Mean F(%) Mean
Gastropoda Fragments FA 24.2 0.34 40.0 1.10 53.1 6.03
Planorbidae Shells OW 8.1 0.44 6.7 0.13 15.6 1.06
    Helisoma Shells OW 0.0 0.00 6.7 0.13 6.2 1.47
    Arminger crista L. Shells OW 1.6 3.23 6.7 1.13 6.2 1.59
    Promenetus exacuous Say Shells OW 0.0 0.00 0.0 0.00 6.2 1.53
    Gyralus Shells OW 8.1 0.48 30.0 2.27 40.6 6.34
    Promenetus umbilicus Cockerell Shells OW 0.0 0.00 10.0 0.13 9.4 3.47
    Planorbula Shells OW 1.6 0.23 3.3 0.07 3.1 0.03
Lymnaeidae Shells OW 12.9 0.68 40.0 30.37 56.2 30.16
Physidae Shells OW 0.0 0.00 10.0 0.47 15.6 5.09
    Aplexa hyphorum L. Shells OW 0.0 0.00 6.7 0.20 9.4 8.25
Truncatillidae Shells OW 8.1 0.42 6.7 0.17 9.4 1.87
Cladocera Eggs OW 4.8 0.05 36.7 10.67 43.7 265.44
Ostracoda Shells OW 0.0 0.00 6.7 2.07 12.5 2.34
Conchostraca Shells OW 0.0 0.00 3.3 0.03 3.1 0.59
Annelida Remains FU 11.3 0.24 6.7 0.10 3.1 0.03
    Oligochaeta (terrestrial) Remains OU 9.7 0.18 10.0 0.20 6.2 0.06
    Nematoda Remains FU 3.2 0.06 3.3 2.77 3.1 0.47
    Nematomorpha Remains FW 1.6 1.23 3.3 0.03 3.1 0.06
Hemiptera (terrestrial) Remains OU 1.6 0.16 0.0 0.00 0.0 0.00
    Corixidae Remains FW 0.0 0.00 6.7 0.13 9.4 0.53
    Notonectidae Remains FW 0.0 0.00 0.0 0.00 3.1 8.94
    Pleidae Remains FW 0.0 0.00 6.7 0.97 0.0 0.00
Trichoptera Cases OW 0.0 0.00 3.3 0.07 12.5 0.12
Diptera Larvae Remains FU 25.8 1.56 43.3 2.40 21.9 0.93
    Chironomidae Larvae Remains FW 0.0 0.00 13.3 1.27 18.7 3.28
Diptera (Adult) Remains OU 9.7 0.23 10.0 0.13 3.1 0.03
Hymenoptera Remains OU 8.1 0.76 10.0 0.17 6.2 0.12
Hymenoptera Eggs OU 1.6 0.10 0.0 0.00 0.0 0.00
Homoptera Remains OU 3.2 0.06 0.0 0.00 0.0 0.00
Homoptera Eggs OU 3.2 0.37 0.0 0.00 0.0 0.00
Odonata (Larvae) Remains OW 1.6 0.02 6.7 0.07 6.2 0.06
Lepidoptera Remains OU 6.4 0.06 3.3 0.03 9.4 0.09
Orthoptera Remains OU 1.6 1.61 3.3 0.10 6.2 0.06
Thysanoptera Remains OU 0.0 0.00 3.3 0.03 9.4 0.09
Unidentified Coleoptera Remains FA 30.6 0.55 36.7 0.83 34.4 0.97
Coleoptera (terrestrial) Remains OU 50.0 1.53 33.3 0.83 46.9 1.03
    Hydrophilidae Remains FW 0.0 0.00 16.7 0.23 18.7 0.47
        Berosus Remains FW 0.0 0.00 13.3 0.20 25.0 0.28
        Hydrochus Remains FW 0.0 0.00 10.0 0.13 6.2 0.06
    Dytiscidae Remains FW 1.6 0.03 20.0 0.30 21.9 0.44
    Haliplidae Remains FW 1.6 0.02 0.0 0.00 18.7 0.25
Collembola Remains FU 3.2 0.03 6.7 0.07 6.2 0.06
Acari Remains FA 4.8 0.06 10.0 0.37 6.2 0.12
Araneida Remains FU 0.0 0.00 6.7 0.10 6.2 0.09
Chilopoda Remains OU 3.2 0.03 0.0 0.00 0.0 0.00

Table 2.  Simplified taxa evidence type used, habitat affinity (HA), frequency of occurrence (F), and average count in field samples from upland sites, temporary wetland sites, and seasonal wetland sites (OW = Obligate Wetland).
Taxon Evidence Type HA Upland Temporary Seasonal
F(%) Mean F(%) Mean F(%) Mean
Planorbidae Shells OW 11.3 1.47 33.3 3.87 50.0 15.5
Lymnaeidae Shells OW 12.9 0.68 40.0 30.37 56.2 30.16
Physidae Shells OW 0.0 0.00 16.7 0.67 21.9 13.34
Cladocera Eggs OW 4.8 0.05 36.7 10.67 43.75 265.44
Ostracoda Shells OW 0.0 0.00 6.7 2.07 12.5 2.34
Trichoptera Cases OW 0.0 0.00 3.3 0.07 12.5 0.12

Table 3.  Adjusted marginal means and standard errors (in parentheses) of numbers of species from field samples and LogCount; unweighted (all taxa), weighted (all taxa), and with simplified taxonomy. Means within column not sharing the same superscript are significantly different (P = 0.05).
Habitat Unweighted Weighted Simplified taxonomy
Number of Species LogCount Number of Species LogCount Number of Species LogCount
Upland 2.53a
(0.39)
3.03a
(0.82)
0.85a
(0.28)
1.08a
(0.67)
0.28a
(0.17)
0.47a
(0.47)
Temporary 4.94b
(0.51)
7.20b
(1.15)
2.97b
(0.38)
4.94b
(0.96)
1.35b
(0.22)
3.28b
(0.67)
Seasonal 5.91b
(0.49)
10.46c
(1.12)
3.91b
(0.36)
8.00c
(0.93)
1.97c
(0.22)
5.19c
(0.64)

Incubated Samples.  We successfully incubated invertebrates representing 15 taxa (Table 4), which we grouped into 5 taxa in our simplified taxonomy (Table 5). For our incubated samples, we found that the differences in taxon richness and LogCount among the three habitat types (upland, temporary wetland, seasonal wetland) were even greater than found for the field samples, regardless of whether or not weighting was done or the simplified taxonomy used (Table 6). Using unweighted data, the three habitat types differed from one another for both taxon richness (F2,60 = 60.23; P < 0.0001) and LogCount (F2,60 = 42.33; P < 0.0001). Similarly for the weighted samples, we found that both taxon richness (F2,60 = 60.56; P < 0.0001) and LogCount (F2,60 = 42.19; P < 0.0001) differed among habitat types. In all cases for both weighted and unweighted samples, each of the habitat types was statistically unique (P < 0.05). The results for the analysis using the simplified taxonomy were similar for taxon richness and LogCount, with a large difference among habitat types for LogCount (F2,60 = 48.26; P < 0.0001) and each of the habitat types being distinctive (P < 0.05).

Scattered Plot Graph: Weighted LogCount vs. Weighted Taxon Richness
Figure 1.   Relationship of LogCount and the number of invertebrate taxa, weighted by habitat affinity, for visually derived field data using complete taxonomy for 62 intensively farmed temporary and seasonal wetlands in the Prairie Pothole Region. The line, weighted LogCount = 3-4(weighted taxon richness), separated wetland and upland sites with the minimal number of classification errors (21.8%). Thirty upland observations are hidden in the lower, lefthand corner.


Scattered Plot Graph: Weighted LogCount vs. Weighted Taxon Richness
Figure 2.   Relationship of LogCount and the number of invertebrate taxa, weighted by habitat affinity, for visually derived field data using complete taxonomy for 62 intensively farmed temporary and seasonal wetlands in the Prairie Pothole Region. Twenty-five upland sites where samples were incorrectly collected from within wetland areas are identified as wetland sites. Thirty upland observations are hidden in the lower, lefthand corner.

Classification of Sites

For the field data with the complete taxonomy, we found that when both variables were weighted by wetland affinity, the line that separated the data with the fewest (27/124 = 21.8%) classification errors was defined by: LogCount = 3 - 4(Taxon Richness) Most of the errors (25 of 27) represented upland sites classified as wetlands (Figures 1 and 2). The simplified taxonomy produced a slightly higher error rate; 29 of 124 (23.4%) sites were misclassified. Among the numerous lines that yielded the best results was the same one generated from the complete taxonomy analysis: LogCount = 3 - 4(Taxon Richness). Ten upland sites were misclassified as wetland, and 19 wetland sites (13 temporary and 6 seasonal) were misclassified as upland. In contrast to the complete taxonomy, we found that using the simplified taxonomy correctly classified more of the upland sites and fewer of the wetlands.

For the aquarium data, we found satisfactory the simple rule that classified sites as wetland if either number of taxa > 0 or LogCount > 0. This rule, with the complete taxonomy, yielded seven wetland sites (six temporary and one seasonal) classified as upland, and seven upland sites classified as wetland, for an overall error rate of 14/124 = 11.3%. With the simplified taxonomy, the rule misclassified the same sites as with the complete taxonomy, as well as an additional seasonal wetland site that was misclassified as upland; the overall error rate was 15/124 = 12.1%.

Table 4.  Taxa, habitat affinity, frequency of occurrence (F), and average number incubated from samples from upland sites, temporary wetland sites, and seasonal wetland sites (FW = Facultative Wetland, OW = Obligate Wetland).
Taxon Habitat Affinity Upland Temporary Seasonal
F(%) Mean F(%) Mean F(%) Mean
Cladocera              
    Ceriodaphnia sp. OW 1.6 0.16 13.3 55.83 15.7 14.87
    Daphnia sp. OW 3.2 0.03 6.7 7.60 15.6 32.16
    Macrothrix sp. OW 1.6 0.34 6.7 14.93 0.0 0.0
    Moina sp. OW 4.8 1.06 53.3 31.60 62.5 96.16
    Simocephalus sp. OW 0.0 0.00 0.0 0.00 12.5 78.12
Ostracoda OW 1.6 0.05 26.7 1.73 46.9 8.16
Copepoda              
    Calanoida OW 0.0 0.00 16.7 0.57 12.5 1.84
    Cyclopoida OW 0.0 0.00 0.0 0.00 3.1 0.06
Anostraca              
    Branchinecta lindahli Packard OW 1.6 0.05 23.3 4.20 31.2 4.87
    Streptocephalus dorothae Mackin OW 0.0 0.00 0.0 0.00 6.2 0.12
Conchostraca              
    Eulimnadia sp. OW 3.2 0.06 16.7 0.50 18.7 1.09
Aquatic Oligochaeta OW 0.0 0.00 0.0 0.00 3.1 0.03
Diptera              
    Chironomidae FW 0.0 0.00 0.0 0.00 3.1 0.03
Coleoptera              
    Berosus fraturnus LeConte (adults) FW 0.0 0.00 3.3 0.07 3.1 0.03
    Berosus fraturnus LeConte (larvae) OW 0.0 0.00 3.3 0.07 0.0 0.00

Table 5.  Simplified taxa, habitat affinity, frequency of occurrence (F), and average count incubated from samples from upland sites, temporary wetland sites, and seasonal wetland sites (OW = Obligate Wetland).
Taxon Habitat Affinity Upland Temporary Seasonal
F(%) Mean F(%) Mean F(%) Mean
Cladocera OW 8.1 1.11 60.0 95.03 75.0 143.19
Ostracoda OW 1.6 0.05 26.7 1.73 46.9 8.16
Copepoda OW 0.0 0.00 16.7 0.57 15.6 1.91
Anostraca OW 1.6 0.05 23.3 4.20 31.2 5.00
Conchostraca OW 3.2 0.06 16.7 0.50 18.7 1.09

Table 6.  Adjusted marginal means and standard errors (in parentheses) of numbers of species incubated from samples and LogCount; unweighted (all taxa), weighted (all taxa), and with simplified taxonomy.  Means within column not sharing the same superscript are significantly different (P = 0.05).
Habitat Unweighted Weighted Simplified Taxonomy
Number of Species LogCount Number of Species LogCount Number of Species LogCount
Upland 0.19a
(0.16)
0.27a
(0.44)
0.19a
(0.16)
0.27a
(0.44)
0.15a
(0.11)
0.21a
(0.33)
Temporary 1.72b
(0.20)
3.96b
(0.76)
1.73b
(0.20)
3.96b
(0.59)
1.44b
(0.15)
3.47b
(0.45)
Seasonal 2.34c
(0.20)
6.31c
(0.57)
2.32c
(0.20)
6.29c
(0.57)
1.88b
(0.14)
5.15c
(0.43)


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