Tentative Genus-level Tolerance Values of Chinese Mayflies (Ephemeroptera)
Abstract
Tolerance values are tentatively assigned to 52 genera belonging to 16 families of Chinese mayflies based on previously reported data and collection experience. This preliminary work is an attempt to provide a private opinion of genus-level tolerance values of Chinese mayflies to workers on using macroinvertebrates to monitor water quality.
Tolerance value (sometimes named Biotic Index value, Morse, Yang & Tian 1994) of aquatic insect taxa play key role in using aquatic insects to monitor water quality. Only when tolerance values are assigned to the taxa, they may be used to compute Biotic Index which are further used to classify water quality type, then to evaluate water body polluted or not. In other words, without tolerance values of aquatic insect taxa, we can not use aquatic insects to monitor water quality.
Assigning tolerance values to taxa is a complex and time-consuming work. Lenat (1993 and personal communication) said that at least three steps should be performed to do that. First, without any previous information on this issue, a group of investigators who annexed to water pollution work can assign initial tolerance values to taxa. Those data are called "expert opinion". Second, a large data base including precise taxa identification knowledge and system, known water quality rank and related sample should be work out and established. Finally, based on data base and "expert opinion" mentioned above, a more objective taxa tolerance values may be assigned.
Unfortunately, up to present time, the Chinese mayflies (Ephemeroptera) are poorly known. At most of time, a large portion of mayfly collection can not be classified correctly at the genus level, especially in Heptageniidae and Baetidae. Further, there are few researchers working on mayfly taxonomy in China and the relationship between mayflies and water quality have not been studied. We can find too few experts to make "expert opinion". In addition, the work of relating certain mayfly taxa to certain water rank, as far as we know, has not begun yet.
But from the year 1994 on, in China, using aquatic macroinvertebrates to monitor water quality has carried out in larger extent than before and developed rapidly. As one of major parts of aquatic benthos, mayflies are indispensable either in using EPT (Ephemeroptera, Plecoptera, Trichoptera) method or using all macroinvertebrates method to monitor water quality (see Lenat and Barbour, 1993). Furthermore, there are only limited taxa tolerance values referred to Chinese mayflies (Morse, Yang & Tian, 1994). Some domestic and endemic genera were not included or were not given tolerance values. And the most important, in recent five years, more genera have been found and recorded in Chinese mainland (Tong and Dudgeon, 2000a, 2000b, 2000c; Zhou et al., 2000a, 2000b), and in my collection, there are some undescribed new genera and new record genera. So tolerance values data are urgently in need to amend or assign to Chinese mayflies.
METHODS
1. to the genera that occur in both China and North America, we copy the data proposed by Lenat (1993);2. to the genera that do not occur in North America but have found in China, we try assigning them tolerance values based on: a) close related genera value data in phylogeny; b) distribution data; c) my collection experience and records; d) tolerance values of those genera living together with those in question.
RESULTS
The tolerance values of Chinese 52 genera belonging to 16 families from update classification system listed in the following table. The Chinese genus taxa which may be invalid, or rare found, or larvae unknown are not included.
TABLE Tolerance values of 52 mayfly genera in 16 familes known from China. * = data from Lenat (1993) on North Carolina mayfly taxa. / = distribution data are unclear or questionable, but those taxa are expected common in China. More information is in discussion.
| Taxa | Known or expected Chinese Distribution | Tolerance value |
|---|---|---|
| Austremerellidae | ||
| 1. Vietnamella | South, Middle | Very low (0-0.5?) |
| Baetidae | ||
| 2. Acentrella | / | 3.6* |
| 3. Alainites | / | |
| 4. Baetiella | / | |
| 5. Baetis | Throughout | 1.2-8.0* |
| 6. Centroptilum | / | 6.3* |
| 7. Cloeodes | North? | |
| 8. Cloeon | Throughout? | 7.4* |
| 9. Fallceon | / | |
| 10. Labiobaetis | / | |
| 11. Nigrobaetis | / | |
| 12. Procloeon | / | |
| Caenidae | ||
| 13. Brachycercus | South, West, Northeast | 3.5* |
| 14. Caenis | Throughout | 7.6* |
| 15. Clypeocaenis | South | Median (3.5-5.0?) |
| Ephemerellidae | ||
| 16. Cincticostella | Throughout | Low (0-1.0?) |
| 17. Drunella | North, West | 0-1.3* |
| 18. Ephacerella | Throughout | Very low (0-0.5?) |
| 19. Ephemerella | North | 0-4.0* |
| 20. Serratella | Throughout | 0-2.7* |
| 21. Torleya | Throughout | Very low (0-0.5?) |
| 22. Uracanthella | Throughout | Low to median (1.5-4) |
| Ephemeridae | ||
| 23. Ephemera | Throughout | 0-2.2* |
| Heptageniidae | ||
| 24. Afronurus | Throughout | Median (3.0-5.0?) |
| 25. Cinygma | / | Very low (0-0.5?) |
| 26. Cinygmina | Throughout | Median (3.0-5.0?) |
| 27. Cinygmula | West | 0* |
| 28. Ecdyonurus | / | Low (0-1.0?) |
| 29. Epeorus | Throughout | 1.0-2.0* |
| 30. Heptagenia | Throughout | 0.5-2.8* |
| 31. Paegniodes | South | Very low (0-0.5?) |
| 32. Rhithrogena | Throughout | 0-0.4* |
| 33. Thalerosphyrus | South | Very low (0-0.5?) |
| Isonychiidae | ||
| 34. Isonychia | Throughout | 3.8* |
| Leptophlebiidae | ||
| 35. Choroterpes | Throughout | Very low (0-0.5?) |
| 36. Choroterpides | South | Low (0-1.0?) |
| 37. Habrophlebiodes | South | Very low (0-1.0?) |
| 38. Isca | South | Very low (0-0.5?) |
| 39. Leptophlebia | 6.4* | |
| 40. Paraleptophlebia | North, Middle | 1.2* |
| 41. Thraulus | South | Low (0.5-1.5?) |
| Neoephemeridae | ||
| 42. Neoephemera | West | 2.1* |
| 43. Potamanthellus | Throughout | High (5-7?) |
| Oligoneuridae | ||
| 44. Oligoneuriella | Northeast | Very low (0?) |
| Palingeniidae | ||
| 45. Anagenesia | Northeast | Very low (0?) |
| Polymitarcidae | ||
| 46. Ephoron | South | 1.5* |
| Potamanthidae | ||
| 47. Potamanthus | Throughout | 1.6* |
| 48. Rhoenanthus | Throughout | Low (1.0-1.5) |
| Prosopistomatidae | ||
| 49. Prosopistoma | South, Middle | Very low (0?) |
| Siphlonuridae | ||
| 50. Ameletus | North, West | 2.1* |
| 51. Siphlonurus | North, West | 2.6* |
| Teloganodidae | ||
| 52. Teloganodes | South | Very low (0-0.5) |
DISCUSSION
The tolerance values listed in this paper are tentative, preliminary, subjective and with private biases. Readers are cautioned to use them. But this is the first attempt to assign tolerance value to most known mayfly genera from China.
The tolerance values are classified into 5 ranks: very low (0-1.0), low (1.0-3.0), median (3.0-5.0), high (5.0-7.0) and very high (7.0-10.0).
During the recent 25 years, the classification system of Baetidae has changed dramatically (Lugo-Ortiz and McCaffertry, 1998; Lugo-Ortiz et al., 1999; Kluge and Novikova, 1992; Waltz and McCafferty, 1987a, 1987b, 1997). Based on larval characters, many new genera have been erected and some genera have been degraded. In addition, almost all the Chinese baetid species were described in adult stage only in the previous works. So at present time, those species lacking definite data on adult-larva association can not be adequately allocated at the generic level. Fortunately, genera Acentrella, Alainites, Baetiella, Labiobiella, Nigrobaetis belong to Baetis-complex and some type species of them are previously in genus Baetis. In our own opinion, their tolerance values may refer to that of Baetis.
Concerning Clypeocaenis . All caenid genera have relatively high tolerance values. On the other hand, this genus has the same feeding habit as Isonychia. So we assign "median" to it.
Uracanthella has only one species U. rufa. This species was previously classified into Serratella, and it is found throughout Oriental and Paelearctic region. So we assign "low to median" to it.
The species of Prosopistoma were collected from lotic water in stream or river (Tong and Dudgeon, 2000c; Liu et al., 1984; Soldán and Braasch, 1984; my collection records). The other mayflies collected in same habitat include Serratella, Drunella, Cincticostella, Torleya (Ephemerellidae), Epeorus (Heptageniidae), Clypeocaenis (Caenidae). From their limited distribution area, living habitat and specialized habit, it is expected to have a lower tolerance value.
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