Spatial distribution of benthic macroinvertebrates in the Erhai basin of southwestern China

Figures & data

Figure 1. Location of sampling sites in the Erhai basin and identification of the four final groups denoted by TWINSPAN analysis.

Figure 2. CCA biplot showing significant environmental factors.

Table 1. Community trait and environmental variables (means) of the Erhai basin streams and results of the K–W test among the four groups.

Variable	Group A	Group B	Group C	Group D	K–W test	p-value
Community trait
Shannon–Wiener	2.27	2.24	1.81	0.81	21.06	0.0001
Evenness	0.76	0.69	0.62	0.37	17.12	0.0010
Richness	20	26	19	8	22.57	<0.0001
Environmental
COD (mg L^−1)	1.57	1.96	3.09	2.70	7.28	0.0635
Ca (mg L^−1)	10.38	23.38	22.03	18.26	10.19	0.0170
NO3–N (mg L^−1)	0.11	0.21	0.78	0.45	22.43	<0.0001
TP (mg L^−1)	0.04	0.05	0.15	0.32	10.53	0.0146
Streambed width (m)	4.6	2.6	4.2	10.2	6.38	0.0947
Altitude (m)	2,385	2,199	2,043	1,891	22.02	<0.0001
QHEI	52	42	28	34	25.79	<0.0001
Note: K–W, Kruskal–Wallis.

Table 2. Optimum and tolerance values generated by the weighted-averaging regression analyses of benthic macroinvertebrate for NO₃–N, altitude, and QHEI in the Erhai basin.

Taxon	Number of occurrences	NO3–N (mg L^−1)		Altitude (m)		QHEI
		Optimum	Tolerance	Optimum	Tolerance	Optimum	Tolerance
Aracina	23	0.15^a	0.15	2323	218	49.8^a	5.3
Antocha bifida	32	0.22	0.20	2242	297	45.6	10.4
A. morimotoi	28	0.18^a	0.12	2258	235	47.2	8.6
Baetis sp.	41	0.36	0.34	2164	194	39.7	12.0
Ceratopsyche sp.	25	0.14^a	0.09	2310	223	48.3	7.6
Diptera	29	0.64	0.55	2047	223	34.5	12.7
Eukiefferiella sp.	40	0.34	0.34	2154	234	39.1	11.1
Gammarus sp.	33	0.51	0.46	2098	156	36.0	10.2
Guttilelopia sp.	36	0.15^a	0.17	2300	295	48.9	11.1
Heptagenia sp.	29	0.31	0.45	2158^a	107	34.5	9.1
Iron sp.	24	0.19	0.29	2238	213	42.8	11.7
Macronychus glabratus	39	0.31	0.39	2212	222	42.5	12.5
Nemoura sp.	26	0.14^a	0.08	2457	273	50.2	7.7
Parakiefferiella sp.	23	0.79	0.59	2061^a	97	29.2	7.8
Simulium sp.	42	0.57	0.51	2104	255	33.8	14.5
Stenelmis sp.	26	0.24	0.20	2261	199	47.5	7.0
Tanytarsus sp.	33	0.83	0.53	2050	189	31.9	11.8
Tubificidae	35	0.65	0.52	1961	176	30.2	11.9
Notes: Only taxa that occurred in at least 20 of 44 sites are listed.
^aIndicates a potential indicator taxon.

Figure 3. Observed NO₃–N, altitude, and QHEI values at the 44 sites plotted against predicted values calculated from a weighted-averaging regression model.