Фауна сисара Србије - вредновање функционалне улоге и значаја врста у екосистемима

Abstract

Сисари, као разноврсна и широко распрострањена класа, у свим екосистемима које насељавају, суштински доприносе њиховом функциони- сању и стабилности. Као биолошки ресурси, човека снабдевају важним прехрам- беним, одевним и другим производима. У екосистему, обављају три велике групе еколошких функција. Трофичка функција је најзначајнија и огледа се у диверзифи- кацији и повећању редундантности трофичких мрежа чиме доприносе њиховој ста- билности, док врсте већих телесних димензија омогућавају хоризонтални трансфер продукције и јаче предеоно умрежавање екосистема. „Bottom-up контрола“ тока продукције је својство нижих (хербивори), односно „top-down“, виших (предатори), трофичких позиција. Тако ситни сисари својом бројношћу (биомасом) и доступно- шћу контролишу бројност предатора док истовремено карниворни сисари регули- шу биомасу плена. На тај начин се успоставља динамичка равнотежа која одржа- ва стабилност екосистема и структуру трофичке мреже. Хербиворни притисак, са своје стране, доприноси одржању бројних типова отворених станишта и дефинише темпо и ток сукцесије на подручју. Ситни сисари, уз инсекте, представљају и главну трофичку основу за већину омниворних и карниворних животиња различитих кла- са кичмењака. Као градитељске (инжињерске) врсте формирају и одржавају усло- ве опстанка читавим заједницама. Тако, градњом брана дабар изграђује све типове влажних станишта унутар којих се формирају богатије биоценозе чиме се додатно стабилизују акватични екосистеми који су иначе у групи фрагилних система. Као вектори паразита и патогена, сисари представљају важне резервоаре, преносиоце или домаћине многих врста, укључујући оне који се могу пренети на човека и гајене животиње. Одржавањем баланса популација плена, контроле бројности векторских организама, домаћини пружају важне екосистемске услуге човеку, што је посебно значајно у урбаним и пољопривредним екосистемима. У светлу климатских проме- на, сматра да ће ове улоге сисара добијати на значају и постати важни екосистемски сервиси. У Србији су истраживања ових улога тек у повоју, па је валоризација ових сервиса слабо позната. Прелиминарни резултати индикаторских (шакал), “umbrella” (медвед) и “keystone” (вук) врста за сада указују на економски значај сисара у контро- ли популација штетних организама или вектора и домаћина различитих патогена.

As a diverse, widely distributed class of vertebrates, mammals make an essential contribution to stability and functioning of all ecosystems they inhabit. Unfortunately the systematic integral research on significance and role of this fauna or individual species in various ecosystems and habitats was never performed in Serbia. However, the idioecological research on certain species and taxa has yielded certain data on their status, role and significance. The most recent studies included intensive research of bat and large carnivore faunas, providing important results on determining their roles in ecosystems or habitats. The trophic function is the most important and reflected in diversification and increase in redundancy of trophic networks, contributing to their stability, while species with larger body size enable horizontal transfer of production among the ecosystems and stronger biome networking of said ecosystems. The “bottom-up” control of production flow is characteristic for lower (herbivores) while “top-down” is characteristic to higher trophic positions (predators). Therefore the large carnivores (wolf, bear and lynx), as predators on top of their trophic pyramids, primarily control the abundance of populations of their natural prey. On the other hand, their predatory pressure and competition may also control abundance and distribution of medium-sized carnivores (mesocarnivores), and further in a cascade fashion of small carnivores as well. On the other hand, souslik is an important prey species for several species of birds of prey (i.e. Saker Falcon Falco cherrug, Imperial Eagle Aquila heliaca) and survival and population size of these birds essentially depends on availability of this steppe species. The influence of such species within the ecosystems sets them as umbrella species, and their protection additionally indirectly protects all other plant and animal communities sharing the same area. Identification of species with important roles in ecosystem functioning, including umbrella species, keystone species or flagship species, makes protection and conservation of ecosystems and biodiversity much more effective as it enables easy management decisions important for nature conservation. Therefore they may be used for choosing the areas of interest for conservation of nature and biodiversity, or simplify assessment of minimal and optimal areas necessary for proper protection. The keystone species are organic species that in comparison to their population numbers have a disproportionally high impact on stability and functioning of the ecosystems they inhabit. This concept is currently widely accepted in modern conservation biology, as focused protection of a single species may preserve whole communities and ecosystems. A typical example of keystone species and their importance in ecosystem or biome diversityincludes large carnivores with wide territories. Protecting just bears with a home range of up to several thousands of km2 may preserve whole forested mountain areas in Serbia, their wildlife communities and biodiversity as a whole. On the other hand, bats also play a very important role within the specific type of cave ecosystem. They are responsible for the main introduction of organic matter crucial to the whole cave ecosystem. Guano (bat droppings) is a main source of nutrients in this relatively isolated system. Large colonies may produce significant amounts of guano, creatingfavourable living conditions for other cave organisms. Data on presence, abundance and population density for certain mammal species may provide important information on present conditions, stability and threat status of the ecosystem. In essence these are indicator species, defining the characteristics and conditions of habitats, ecosystems or overall environment. Today they are included in various forms of population monitoring. The monitoring results include not only information on density, abundance or population dynamics of the monitored species but also on conditions in the ecosystem inhabited by the indicator species. The mere presence of souslik (Spermophilus citellus) or mole-rat (Spalax leucodon) in steppe habitats indicates well-preserved fragile habitats of this type. In addition to providing information on present conditions in natural ecosystems, the indicator species may also provide important information on processes within the ecosystems altered by anthropogenic activity. Under the negative influence of direct or indirect anthropogenic changes, most organic species react with decrease in population numbers and range size. To the contrary, the opportunistic species show increase in range and abundance. The best examples of range spread and population increase in modern times are wild boar (Sus scrofa) and golden jackal (Canis aureus), species with ecological plasticity and able to use anthropogenic resources, primarily of nutritional type. The direct role of indicator species within the ecosystems would be to indicate the present conditions of ecosystem quality through their status, through direct ecosystem services (provisioning services), while the indirect role pertains to the ecological status of these organisms enabling bioindication of support and regulation ecosystem services. These important species may also be important indicators of intangible (cultural, recreational, scientific) ecosystem services. As engineer species, some mammals may form and sustain the habitat conditions favourable for survival of whole communities. Engineer species may be any organic species creating, sustaining, significantly modifying or disrupting the ecosystem theyinhabit. Due to their unique ability to create and modify the characteristics of the ecosystem, these species have an immense impact on biodiversity and heterogeneity at the microhabitat and biome level. The best example of engineer species are probably beavers – European (Castor fiber) and Canadian (Castor canadensis). As engineer species, beavers are among rare animals that may alter the hydrological and biotic characteristics of aquatic and surrounding wetland habitats in a similar way to anthropic activity. Through construction of their dams they create all types of wetland habitats, forming richer biocoenoses and additionally stabilizing the aquatic regime. This leads to increase in heterogeneity of the whole area, habitat types and biodiversity at ecosystem and biome level. In addition, the beaver diet may significantly influence the pathways and speed of succession and structure of plant and animal communities. Due to their evident influence on aquatic ecosystems, they may be also designated as keystone species in aquatic habitats. As parasite and pathogen vectors, mammals represent important reservoirs, transmitters or hosts for numerous species, including those that may be transferred to humans and farmed animals. By maintaining the balance in prey populations and population control of vector organisms, the hosts provide important ecosystem services to humans, and this is particularly important in urban and agricultural ecosystems. Due to spread of mosquitoes and mosquitoborne diseases, including malaria and West Nile virus, there is an increase in risk of infection for human populations (including the population in Serbia). In light of climatic changes it is believed that these aspects of mammal populations will increase in significance and become important ecosystem services. In Serbia, the research on these aspects is still in the initial phase so the valorisation of these services is poorly known. The preliminary results of indicator species (golden jackal), “umbrella species” (brown bear) and “keystone species” (wolf) presently indicate economic importance of mammals in population control of detrimental organisms or as vectors and hosts of various pathogens. According to the existing (albeit scarce) literature and the results of modern research, it may be concluded that mammals play a very important role in conservation, stability and functioning of ecosystems in Serbia. From the aspect of functioning and stability of the ecosystems, certain mammal species certainly stand out and may be designated as keystone, umbrella, indicator or engineer species. They not only have a significant impact on sustaining the ecosystem vitality and biodiversity conservation, but they also provide important ecological services with numerous beneficial and useful aspects to lives of all of us.