Table 2 Descriptive statistics for the continuous predictor variables used to assess the occurrence and abundance of freshwater snail species in the Ethiopian Rift Valley

Altitude (m)

1655–1699

1678.9 ± 7

1681

1618–1645

1633.3 ± 5.3

1634

Water depth (m)

0.2–2.0

0.7 ± 0.4

0.6

0.1–1.2

0.5 ± 0.2

0.5

Transparency (m)

0.1–0.6

0.2 ± 0.1

0.2

0.1–0.8

0.3 ± 0.1

0.2

Ambient temperature (°C)

18–30

25 ± 2.9

26

16–30

23.7 ± 2.9

24

Water temperature (°C)

14.2–27.6

22 ± 3

22.2

15.2–30.2

21.9 ± 3.8

21.8

Dissolved oxygen (mg/l)

0.1–16

4.7 ± 2.7

4.5

0.3–21.5

6.5 ± 3.6

6.2

Oxygen saturation (%)

1.1–209

66 ± 38.7

60.4

4.4–349

96.1 ± 62.2

91.4

Chemical oxygen demand (mg/l)

7.9–50.4

19.8 ± 8.1

18.4

3.4–41.3

15.7 ± 7.3

16.2

Electrical conductivity (μS/cm)

137.3–2015

757 ± 431.1

902

233–3680

893 ± 590.7

700

pH

5.4–9.6

8.2 ± 0.9

8.9

3.1–9.8

7.5 ± 1.6

8.1

Turbidity (NTU)

2.8–247

24.6 ± 43.5

14.1

1.8–159

32 ± 34.8

13.9

Chlorophyll-a (µg/l)

12.7–41.4

15.5 ± 4.5

14.1

12.6–33.1

14.9 ± 2.8

13.9

Total suspended solids (mg/l)

90.8–687.2

268.8 ± 174

200.8

87.2–759.6

170.1 ± 111.7

145.6

Chloride (mg/l)

5–87

34.7 ± 18.7

38

16–252.9

37.1 ± 33.6

26

Nitrate (mg/l)

0–130.3

7 ± 17.3

0.5

0–95.3

8.4 ± 17.8

0.5

Ammonia (mg/l)

0–5.1

0.7 ± 0.9

0.4

0–5.1

0.8 ± 1.1

0.3

Total phosphorus (mg/l)

0–24.7

1.9 ± 3.4

1.0

0–11.1

1.2 ± 1.5

0.8

Orthophosphate (mg/l)

0–23.9

1.1 ± 2.8

0.4

0–7.8

0.5 ± 0.9

0.3

Alkalinity (mg/l)

78–896

381.4 ± 185.9

404

164–1414

376.1 ± 230.5

304

Total hardness (mg/l)

22–184

51.5 ± 23.4

46

52–316

116.4 ± 45.1

112

Calcium (mg/l)

14–114

32.4 ± 18.4

26

32–196

71.6 ± 34.6

60

Magnesium (mg/l)

0–76

19.1 ± 12.8

18

4–190

44.8 ± 29.9

44

Canopy cover (%)

0–100

21.5 ± 32.2

0

0–100

29.5 ± 35.7

10

Predator abundance (n)

0–153

19.4 ± 23.5

10

0–43

9.2 ± 9.4

1

Competitor abundance (n)

0–5

0.3 ± 0.8

0

0–79

2.9 ± 11.8

0