13.01.2011 г.

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Abstract


          Many domestic animals and pets return to natural and urban environment and prolong their evolution. The result of evolution is change of ecological system and appearance of a new xenobionts. Some of them may become as a new pests having negative importance for humanity. Redomesticated animals may attack people and some of the animals may transmit infection decease. Such a problems are actual for modern Russian cities. The ecological niches for redomesticated animals may increase under periods of social instability. The process of a new pests appearance by redomestication may be monitored and controlled by use of approaches based on methods of ecology, ethology and genetics. According to global ecology principles (V.Vernadsky) there are no free ecological niche. If urban environment is available for vertebrate pest, this pest will proliferate and niche would be occupied. According to G.Gause law, one species is accorded to one ecological niche. Artificial coexistence of dogs and cats in homes accelerate microevolution of them toward divergence. Redomesticated animals got competition with wild animals and often suffocate the lasts. E.g.  far-east fish rotan gotten rivers of Petersburg district from aquariums forced out some useful fishes of the region. According to ethology principles (K.Lorents), sometimes redomesticated animals have higher intellect than wild ones. It is cause of their win during ecological competition. Occupation of urban and wild environment take place under genetic principles of domestication and redomestication (D.Belyaev). Biphyletic animals (having two genetic sources) diverge to directions of  both ancestors. Redomesticated dogs in Russia are more close to wolf, in Sinai - to jackal. Under redomestication the level of variability of animals decrease.
   
          Appearance of a new biological objects under urban environment induces many problems that may be resolved by complex biological methods.     
 

Introduction


          Human activity needs of theoretical prediction of its ecological results. The level of population genetics and applied mathematics insure possibility to make such a prediction. Important direction of humankind activity is domestication and redomestication of animals as result of interaction between social and natural processes. Those processes may found new pests within both natural and synanthropic environment.

          Theory of domestication was suggested by D.K.Belyaev1,.2. According to him, domestication is the process of hereditary reorganization of wild animals and plants into domestic and cultivated forms according to interest of man. In its strictest sense it refers to the initial stage of man’s mastery of wild animals and plants. The fundamental distinction of domesticated animals and plants from their wild ancestors is that they are created by man’s labor to meet his specific requirement of whims and are adapted to the condition he alone maintains for them.  Without man’s continuous care and solicitude, domesticated animals and plants could not exist.
 
          At this article I shell consider domestication and redomestication of  vertebrate animals (not plants) as source of a new pests. What means domesticated behavior? The main criterion here is the ability of animals to have direct contact with man, not to be afraid of man, to obey him and to reproduce under the condition created by him, which constitutes the necessary condition for the economical use of animals. It is obvious that selection for behavior has been unconsciously carried out by man since the earliest stages of animal domestication. Selection for domesticated behavior seems to result in breaking up previously integrated ontogenic systems and this leads to multiple phenotypic effect that seem genetically unrelated to the selected character, namely tame behavior. In a genetic and biochemical sense, what may be selected for are changes in the regulation of genes - that is, in the timing and the amount of gene expression rather that changes in the in individual structure genes. Selection, having such an effect is called destabilizing selection (D.K.Belyaev)2. The  selection becomes destabilizing when it affects, directly or indirectly, the system of neuroendocrine control of ontogenesis. The population result of such a selection is increase of variability. Domestic animal are more varied that wild ones.
 
          Homeostasis of biological systems suggests resistance to human domestication activity. Under decrease of human selective and destabilizing press the back process of redomestication begins. The processes are reciprocal but not symmetrical. Redomestication consists of the following processes:
    Genetical stabilization and getting phenotype close to natural ancestor.
    Getting a new character including increase of fitness and intellect.
    Divergency to ancestors in their number was more that one. E.g. redomesticated dogs (Canis familiaris) in Europe and North Asia are evolving to wolf (Canis lupus), in Middle Asia and North Africa - to jackal (Canis aureus).
 
          Occupation of a new ecological niche having a new relation with man by other biological species. Some of redomesticated species become new serious pests. The same species may be useful or pest in dependence on situation.


 
Adaptation of redomesticated animals for synanthropic environment


          The urban environment is a field of discontinues microevolution. It is attractive to many animal species, namely for its greater food supply, deficiency of predators, as well as microclimate conditions.  All this deviations from conditions in the wild usually contribute to an increase population density in some vertebrate species. Such disproportionate concentrations are usually connected not only with considerable economic losses but also with health hazards man following from the synanthropic lifestyle of certain species. For instance, feral cats in food manufacturing plants and storage houses etc. 3
 
          Adaptation for synanthropic environment takes place according to principles of global ecology according to theory of Vernadsky4.
 
1. The  biosphere  mass is  constant. According  to  modern data this wet mass is:
     Mb = 250 000 000 000 ton.
2. Biosphere is organized as ecological pyramid (Fig.1). It describes relations between  producents and consuments. Every following flow has mass less 10 - 100 times
3. The range  distribution of species within orders and classes is asymmetrical5. That is, majority of species belongs to some orders. The distribution of specimens within species is asymmetrical too.
The theoretical figure of such a distribution is demonstrated in fig.2 and accorded to formula:

f(n) = A + B e-Cn, where A, B, C - constants
 
Let minimal  number of specimens needed for stable population is
Nk. According to population genetics, it may be 150 - 200. Let Nk' would be minimal number of specimens needful for recurrent detection of species in nature. Species from K' to K would be hidden species. Between hidden and dominant species rare species exist too.
     The species, which population close to extinction (K - the size of population), must be  listed in Red Book. The number of organisms per generum is:

N = Mg/mav
 
Where, Mg  -  biomass  of  generum, m.av - average mass of organism within taxon.  General number of specimens is distributed according to fig.2. Under human activity rare species may become dominant and vice versa. But the general distribution of biological mass between species is stable. The change of status of species - wild - domesticated - redomesticated may be followed by it variability using principles of phenogenetic indication6 - "the previous and future state of species may be indicating by its variability and level of sexual dimorphism".
 

 
Negative ecological results of redomestication
 
 
 
          1. The fish rotan  (Perccotus glehni, Perciformes) from Far East of Russia was domesticated as aquarium fish. At aborigine region it existed in nature under system of stable ecological connections and relations. Getting by redomesticated from aquariums synanthropic water ecosystems of Petersburg region it distorted here ecological connections. Fitness of redomesticated fish appeared to be higher that of aborigine fishes. Competition with here aborigine fish species (Perca fluvuatilis et al.) decreased fish resources. Hence, process of domestication - redomestication of usual fish produced a new pest.

          2. Migrating pigeon (Ecopistes migratorius) is a species disappearing in XIX century. The proclamated cause of extinction to be intensive hunting. Ecologists have no significant testimonies of absolute disappearance of high populated small size animals by anthropogenic pressure. The most probable cause of species extinction is competition with European pigeon (Columba livia) that took place according to Gause7 law. Higher fitness of European pigeon suggested suffocation of aborigine species in both synanthropic and natural landscapes.
          Hence the same species may be both domesticated and redomesticated, both useful and pest.

          3. Feral cat (Felis catus) population in synanthropic ecological systems. Adaptation for a new ecological niche is accompanied by genetically reconstruction5,8. The coefficient of variation (CV) of quantitative traits of domesticated cats is 0.15 - 0.25. Redomesticated cats have data 0.1 - 0.15 (own measure on St. Petersburg population). The coefficient of qualitative morphological variability
 
            m      2
VQL =  (∑ √pi)
           i=1
 
where m - number of morphs. Wild cats have mean VQL  equal 1 - 1.4, domesticated one - 1.4 - 2.0. Redomesticated animals have intermediate mean. Population of such a cats in St.Petersburg is between 50 000 - 200 000 (own measure).
 
Adaptation of population for synanthropic environment suggested the following problems:

Competition and predation of useful animals.
Transmission of decease.
Induction of allergy.
Contamination of city.
Rare - direct aggression against man.
          4.Redomesticated dogs (Canis familiaris). Their evolution is going into two directions - restoration of wolf and jackal characters. Restoration is accompanying by increase of intellect and complicated social behavior - see Lorentz 9,10. The most aggressive are specimens having intermediate state between domesticated and redomesticated state because of their ethological unstability and absence of pattern of environment adaptation. Under wild nature redomesticated dogs began struggle for existence in ecological niche against wild animals. Unique adaptive possibility insure success of such an animals under this struggle. They appear to become a new pests both for synanthropic and natural ecological systems.
 
 
Conclusion. From pets to pests.
 

          Human activity produced new pests, both in synanthropic and natural biocenosis. Resistance and homeostasis of every biological system is higher than desruptive possibilities of humankind. Local disasters result in the death of many organisms. The laws of global  ecology, however, say that unoccipated places are filled immediately. Even the most considerable ecological disasters are unable to significantly change the mass of the biosphere. A reduction of the mass in the one place is always compensated by an increase in another place. An increase of anthropogenic pressure in Western Europe, e.g. has resulted in a significant decrease in  the combined mass of animals and plants. At the same time, the opposite processes are taking place in European Russia. The number of animals and plants is increased. Many hidden      species and species with new characters including pests are between them.
       
          Human-made disasters are such smaller in scale that natural ones. Appearance of a new pests is example of natural resistance against anthropogenic pressure10. We must keep in mind the following ecological principles4,7.
         
          There are no free ecological niches. Every new one made by humankind would be occupied by any species or morphs.
          Every specimen of every species suffocated by man would be exchanged by another specimen or species. The structure and size of ecological pyramid (Fig.2) is constant. A new biological object may be more useful or more dangerous than the old one.
   
          The general stability of biosphere doesn’t mean stability and prosperity of any concrete species including Homo sapiens.

          Management of redomesticated vertebrate pests must be based on methods of three sciences:
i. Ecology (Gause, Vernadsky et.al.) which suggests for decrease of free ecological niche for pests.
ii. Genetics (Dobzhansky) for control of microevolution of pests in dependence of antropogenic press.
iii. Ethology (Lorentz) for control of their behavior.


References

1 Belyaev D.K. (1974). Domestication, plant and animals // Encyclopedia Britanica, Helen Hemingway Benton, p. 936 - 942.
2 Belyaev D.K. (1979) Destabilization as a factor in domestication // J.Heredity, 70:301-308.
3 Rodl P. (1999)  Regulating populations of synanthropic vertebrates in the Czech republic//Proc.3rd Intern Conference on Urban Pests, Czech Univ of Agric., Praha, p.515 - 518.
4 Vernadsky  V.I. (1975)  Thinking  of  naturalist. Moscow, Nauka (Science). 175 pp. (Russ).
5 Sapunov V.B. (1999) The effect of pesticides on evolutionary ecology of pests//Proc.3rd Intern Conference on Urban Pests,Czech Univ of Agric., Praha, p.551 - 557.
6 Sapunov V.B. (1990) Phenogenic indication of population as a new approache to ecological forecast//Abstr. V Intern Congr Ecol., Yokohama, Japan. P. 336.
7 Gause G., (1934)  Struggle for existance. N.Y., A.P.,
8 Dobzhansky Th. (1937) Genetics and the origin of species. Columb.Univ. Press, N.Y., 1937.
9 Lorenz K. (1990) Das sogenannte Bose (Zur Naturgeschichte der Agression). Taschenbuch Verlag. Munchen.
10 Proceedings of the 6th International Conference on Urban Pests., Budapest, 2008. 513 p.   
 
 
 
 
Comments for figures

Fig.1.Ecological pyramid
Fig.2.Distribution of species in relation to number of specimens.

 

 

Материал поступил в редакцию 11.01.2011 
 

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