A major goal of ecology is to understand the factors that shape interactions among species. In this study, I explored the little-known associations between beetles and macrofungal fruiting bodies to characterize patterns of beetle-fungus association and to investigate sources of variation in the structure of these trophic interactions. First, I characterized the composition and diversity of beetle-sporocarp associations at two sites in the Appalachian Mountains and foothills, and evaluated the extent to which beetle community structure varied with fungal species, sporocarp age, and sporocarp dry mass. My results showed that beetle abundance and diversity differed among fungal species and were positively associated with sporocarp age and dry mass. I also found evidence of a nested structure in beetle-sporocarp interactions, wherein specialists on both sides of the association interact preferentially with more generalized species. Next, I performed a field study of beetle-sporocarp associations over two summers to evaluate the factors related to interaction breadth in trophic associations. I found evidence that interaction breadth varies with the palatability of the food organism (as indicated by sporocarp toughness and sporocarp age) and showed that beetle interaction breadth was negatively correlated with sporocarp persistence. I found strong intraseasonal variation in interaction breadth, but no evidence that this variation was structured by precipitation or differences in beetle community composition. In my third chapter, I conducted a field experiment to investigate (1) the importance of an individual food organism's physical properties in determining its relative importance in the beetle-sporocarp interaction network and (2) whether the structure of the beetle-sporocarp interaction network cycles predictably with the time of day. My results show that size and density of individual food organisms may be important factors in determining their relative importance in an interaction network, and offer the first evidence of diurnal cycling in the structure of interaction networks.

Hypogeous fungi perform various functions in the forest ecosystems, they form the mycorrhizal relationship with plants and serve as the food source of some animals. Main aims of this dissertation were to ascertain the diversity and distribution of hypogeous fungi in Lithuania, to compare the communities of hypogeous and epigeous mycorrhizal fungi, and to explore the composition of fungi in small mammal diet. Using various research methods (an analysis of the literature data, the critical examination of the herbarium specimens, the search of the fruit-bodies by raking the soil, an examination of the fecal pellets of small mammals) in total 29 species of hypogeous fungi have been ascertained in Lithuania. The taxonomic structure, distribution and fructification phenology of hypogeous fungi has been analysed. The data on the structure and dynamics of communities of hypogeous and epigeous mycorrhizal fungi in spruce, oak and mixed tree stands were presented. The influence of abiotic and biotic factors on the species composition and fructification of fungi was assessed. The peculiarities of small mammal mycophagy in different tree stands were described. / Požeminiai grybai atlieka įvairias funkcijas miško ekosistemose, sudaro mikorizes su augalais ir yra kai kurių gyvūnų maisto šaltinis. Disertacinio darbo pagrindiniai tikslai buvo išaiškinti Lietuvos požeminių grybų rūšių įvairovę ir paplitimą, palyginti mikorizinių požeminių ir antžeminių grybų bendrijas, išaiškinti grybų sudėtį smulkiųjų žinduolių maisto racione. Pritaikius skirtingus tyrimo metodus (literatūros duomenų analizę, kritišką herbariuminių pavyzdžių tyrimą, grybų vaisiakūnių paiešką grėbliukais suardytame dirvožemyje, smulkiųjų žinduolių ekskrementų tyrimą), nustatyta, kad dabar Lietuvoje žinomos 29 požeminių grybų rūšys. Išnagrinėta požeminių grybų taksonominė struktūra, paplitimas ir fruktifikacijos fenologija. Pateikti duomenys apie požeminių ir antžeminių mikorizinių makromicetų bendrijų struktūrą ir dinamiką eglynuose, ąžuolyne ir mišriame medyne. Įvertinta abiotinių ir biotinių veiksnių įtaka grybų rūšių sudėčiai ir fruktifikacijai. Išnagrinėti kai kurių smulkiųjų žinduolių mikofagijos ypatumai skirtingos sudėties medynuose.

Požeminiai grybai atlieka įvairias funkcijas miško ekosistemose, sudaro mikorizes su augalais ir yra kai kurių gyvūnų maisto šaltinis. Disertacinio darbo pagrindiniai tikslai buvo išaiškinti Lietuvos požeminių grybų rūšių įvairovę ir paplitimą, palyginti mikorizinių požeminių ir antžeminių grybų bendrijas, išaiškinti grybų sudėtį smulkiųjų žinduolių maisto racione. Pritaikius skirtingus tyrimo metodus (literatūros duomenų analizę, kritišką herbariuminių pavyzdžių tyrimą, grybų vaisiakūnių paiešką grėbliukais suardytame dirvožemyje, smulkiųjų žinduolių ekskrementų tyrimą), nustatyta, kad dabar Lietuvoje žinomos 29 požeminių grybų rūšys. Sudarytas Lietuvos požeminių grybų išplėstinis konspektas, grybų makro- ir mikrostruktūros iliustruotos spalvotomis fotografijomis. Išnagrinėta požeminių grybų taksonominė struktūra, paplitimas ir fruktifikacijos fenologija. Pateikti duomenys apie požeminių ir antžeminių mikorizinių makromicetų bendrijų struktūrą ir dinamiką eglynuose, ąžuolyne ir mišriame medyne. Įvertinta abiotinių ir biotinių veiksnių įtaka grybų rūšių sudėčiai ir fruktifikacijai. Išnagrinėti kai kurių smulkiųjų žinduolių mikofagijos ypatumai skirtingos sudėties medynuose. / Hypogeous fungi perform various functions in the forest ecosystems, they form the mycorrhizal relationship with plants and serve as the food source of some animals. Main aims of this dissertation were to ascertain the diversity and distribution of hypogeous fungi in Lithuania, to compare the communities of hypogeous and epigeous mycorrhizal fungi, and to explore the composition of fungi in small mammal diet. Using various research methods (an analysis of the literature data, the critical examination of the herbarium specimens, the search of the fruit-bodies by raking the soil, an examination of the fecal pellets of small mammals) in total 29 species of hypogeous fungi have been ascertained in Lithuania. An annotated checklist of hypogeous fungi of Lithuania was compiled, fungal macro- and microstructures were illustrated with color photographs. The taxonomic structure, distribution and fructification phenology of hypogeous fungi has been analysed. The data on the structure and dynamics of communities of hypogeous and epigeous mycorrhizal fungi in spruce, oak and mixed tree stands were presented. The influence of abiotic and biotic factors on the species composition and fructification of fungi was assessed. The peculiarities of small mammal mycophagy in different tree stands were described.

Both testate amoebae and fungi are common inhabitants of coniferous litter. Their interactions in this environment were rarely studied, although they reach high biodiversity and can play a significant role in nutrient cycling in this environment. In this study, a cultivation of litter needles in the damp chambers was used to investigate interactions between fungi and testate amoebae. Observation of spruce litter needles in environmental scanning electron microscope was used to better characterize testate amoebae communities directly on the needles. Additionally, two experiments changing the biotic conditions in the microcosm were used to follow a principle of the interactions. Three species of testate amoebae from litter needles were able to colonize the filter paper on the bottom of the damp chambers. Occurrence of Phryganella acropodia and Assulina muscorum on the filter paper was significantly fuelled by the presence of mycelium. Assulina muscorum was associated with the fungal spores and Arcella discoides was attracted by sporulating colonies of Cladosporium spp. in the damp chambers. By contrast, no association of putatively mycophagous Phryganella acropodia with fungal spores was observed. Arcella discoides was attracted both by live and death mycelium in additional experiment. Interestingly, the...