Discussion: hidden communities



  • Analising the data on species composition, distribution and abundabce of amoebae we may note that the distribution is very heterogenous. For example, in stereotype samples taken from the same place all the year round, show tha no one species was found in all of the samples (i.e. with 100% frequency). Moreover, most of species were noted only one-two times during all the period of observations and should be considered to be rare. Taking into acount very small migration rates of amoebae (even if consider floating foms), we should search for another explanation of the rapid, sufficient and sometimes repetitive succession of amoebae communities. These results together with the qualitative data, which show that the abundance of every species may undergo sufficient variations from sample to sample forced us to apply the model of so-called "hidden communities" to amoebae community.


  • We suggest that the discovery of amoebae species depends more on the sencivity and specificity of our methods and reflects the relative abundance of different species. Only species, which have sufficient for the method used abundance are discovered. This is clear if we remember the specifity of enrichment cultivation methods, which are the only suitable for amoebae, and were discussed in the literature many times. Thus, analising the sample we cannot stay that we discovered all species which exists in this site. We have in our hands so-called "observed" community. In case we will use other method, including more culture media or will treat larger amount of sediments the observed community will be more comprehensive. However, potential community always goes beyong the observed one, and represents the source of mobility of species composition. Which species will be dominant at the moment depends on the concrete combination of physical, chemical and other factors at this moment. Hidden, "potential" community is much more homogenous though the lake than the results of our single samples. However, definitely it is not totally homogenous, as there are limitation factors will eliminate species in different ecotops even in potential community.
  • And another point we should take into account in this connection. Amoebae, as well as other protists, exists in another time and size scale. Our sampling once per month seems to be equal to the attempts to represent the bottom macrofauna taking one sample 10 km2 in square one time per 200 years and treat several kilograms of it. Such sample will give some data, but it will be difficult to call them representative.



    So, in the light of above told we should conclude:

  • Amoebae fauna of the habitat like lake or pond (not to say about marine areas) cannot be estimated by mean of several samples of the upper layer of bottom sediments. These samples will result in the occurrence of occasional "observed communities" and will not estimate even the potential diversity. May be later, when we will have much more data of this sort we will be able to calculate coefficients of corrections for such data. But by now only monitoring study of the, including sampling and treatment of the cores of sediments can give reliable data on amoebae biodiversity in benthic habitats.

  • Amoebae are hightly abundant in freshwater benthos. This not a new statement, suggested many times by different authors now is confirmed by at least one correct comparison of amoebae and ciliate abundance. Amoebae play one of the major roles in the mass and energy flows in freshwater benthos. We have data for further comparisons.

  • The model of hidden communities, been applied to amoebae, seems to suitable to explain the abnormalities and absence of clear dynamics of species composition of amoebae. If assummed, it requires to re-evaluate the very most of previous data on amoebae biodiversity and biogeography.