Žurnal obŝej biologii

Hypotheses on the origin of life on Earth are discussed in the frame of alternative ideas concerning processes of abiogenesis, formation of protometabolic systems, beginnings of initial protocells. Arguments in favor of independent origin of archaea and bacteria are considered. Based on this information, a new view on the problem of life’s origin is presented. As supposed, life might have aroused multiple times and asynchronously in various local geochemical conditions dependent on many natural factors.

EIPF (Endophytic Insect-Pathogenic Fungi) is an ecologically flexible group of hypocrealean and some other fungi, capable of combining varied lifestyles: free-living saprotrophic, endophytic in plants and pathogenic in insects. For EIPFs, inhabiting insects is temporary and results in the death of their hosts, but they can also form relatively long-term, mutually beneficial consortia with plants. Transition from insects to plants or from plants to insects typically occurs not through direct contact, but after a free-living period in soil or other environment. Penetration of EIPF conidia through the plant and insect cuticles is accomplished through similar pathways, involving similar adhesin molecules. Host plants protect endophytic fungi from environmental factors and provide a source of carbon nutrition. EIPFs in turn can suppress phytophages and phytopathogens and stimulate host plant growth and immunity. Nitrogen transfer from dead insects to plants via EIPFs has been proven, representing a unique branch of the nitrogen cycle in nature.

In order to study the phenomenon of unstable sexual dimorphism (USD) in syntopic populations of sympatric rodent species (Bank vole, Pigmy wood mouse), the variability of the size and shape of the mandible of males and females from five localities of the floodplain forests of the Sakmara, Samara and Ural rivers (Southern Urals) was compared. In age-homogeneous samples of underyearlings of both sexes, sexual dimorphism (SD) was compared by centroid size (SSD) and mandible shape (ShSD) using geometric morphometrics. The favorable habitat conditions were indirectly assessed by the proportion of species in the catch and their abundance per 100 catches per day, and the fatness index (IF, %). SSD – size sexual dimorphism was often, but not always, manifested in favorable conditions for the species (high abundance and proportion of species, and IF) and was not expressed in pessimal conditions (low abundance and proportion of species, and IF), whereas ShSD – shape sexual dimorphism, on the contrary, was expressed to the greatest extent in pessimal conditions. Negative regression relationships were found that are similar for both species, and for the entire sample set, significant negative coefficients of linear correlation were found between the values of the ShSD (according to Mahalanobis distances, D) and the species' shares in catches (r = −0.76), as well as their abundance (r = −0.78) and fatness indices (r = −0.85), this reflects the strengthening of the ShSD in pessimal conditions for development. Since the ShSD of mandibles in rodent species is regularly high in adverse conditions, it can be used for environmental monitoring purposes as an indirect indicator of a rapid morphogenetic response to pessimal conditions and as one of the signs of the onset of local biotic crisis phenomena after exposure to climatic, anthropogenic and/or biotic factors.