Oddziaływania roślinożernych bezkręgowców na makrofity zanurzone

Pieczyńska, Ewa

doi:0013-2969

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Title: Oddziaływania roślinożernych bezkręgowców na makrofity zanurzone

Abstract:

Multiple (both beneficial and detrimental) influences of herbivorous invertebrates on submerged freshwater macrophytes are reviewed and discussed on the basis of the literaturę. Traditionally, direct herbivory on living macrophytes has been considered unimportant, it having been assumed that the majority of herbivores prefer to feed on senescing plants, detritus of plant origin and the periphyton colonising macrophyte surfaces. However, morę recent reviews of this topie show that consumption of live macrophytes by animals may be a widespread phenomenon, of importance in determining macrophyte abundance.The extent of herbivory was shown to vary broadly both among species and among water bodies. The largest noted reductions in macrophyte biomass were usually caused by vertebrates (fish and birds) and large invertebrates (crayfishes), but the impact of other invertebrates may also be important.Macrophytes can be eaten without being killed, and at most sites animals consume only part of the available plant biomass. Many grazers destroy much morę tissue than they eat. Fragmentation, defoliation, loss of leaf area (holes, surface abrasion) and canals from mining animals have been observed in many localities. Secondary effects of the partial consumption of plant tissue are also of great importance. These include infections of grazing scars by microorganisms or further destruction caused by wave action. Depending on the type and scalę of injury, as well as the internal and external factors determining tolerance to herbivory, plants damaged during grazing may experience a limitation of growth (or even die in some cases) but may also continue to grow, in some cases even faster than plants remaining undamaged. In contrast to the rich literaturę on terrestrial plants, there is only very scarce information on post-damage growth in freshwater macrophytes. However, it is known that some macrophytes can regenerate fiom smali fragments, and that fragmentation may be very important in plant propagation. The further fate of plant fragments depends primarily on the production of new lateral shoots. In many cases after the shoot fragments have died, the young lateral shoots detaching from them continue to grow and form new viable plants. Plant fragments detached in the course of feeding can remain within the parental population or may float away, with some of them fal ling to the bottom while others float in the water column. Thus, the post-damage survival and growth of plants are strongly influenced by environmental conditions.The extent of herbivory is influenced by both the constitutive and induced defences of macrophytes. Plant structure (morphology, toughness), chemistry and nutritional value are determinants of animal feeding choices. Although most of the work on plant defences against herbivores derives from studies of terrestrial ecosystems, it has recently been accepted commonly that freshwater macrophytes are defended chemically against herbivores. Many classes of Chemical deterrents have been found in aquatic plants, but direct Chemical interactions between macrophytes and their consumers are documented in only a few cases.The beneficial effects of herbivores on macrophyte growth are primarily associated with the removal of the periphyton colonizing the macrophyte surface, as well as with the enrichment of the nutrient pool, mainly in nitrogen and phosphorus released by feeding invertebrates […].