Effects of fragmentation on plant adaptation to urban environments.

Urban ecosystems are relatively recent and heavily human-altered terrestrial ecosystems with a surprisingly high diversity of animals, plants and other organisms. Urban habitats are also strongly fragmented and subject to higher temperatures, providing a compelling model for studying adaptation to global change. Crepis sancta (Asteraceae), an annual Mediterranean wasteland weed, occupies fragmented urban environments as well as certain unfragmented landscapes in southern France. We tested for shifts in dispersal, reproductive traits and size across a rural-urban gradient to learn whether and how selection may be driving changes in life history in urban and fragmented habitats. We specifically compared the structure of quantitative genetic variation and of neutral markers (microsatellites) between urban and rural and between fragmented and unfragmented habitats. We showed that fragmentation provides a better descriptor of trait variation than urbanization per se for dispersal traits. Fragmentation also affected reproductive traits and plant size though one rural population did conform to this scheme. Our study shows the role of fragmentation for dispersal traits shift in urban environments and a more complex pattern for other traits. We discuss the role of pollinator scarcity and an inhospitable matrix as drivers of adaptation.This article is part of the themed issue 'Human influences on evolution, and the ecological and societal consequences'.

Does inbreeding promote evolutionary reduction of flower size? Experimental evidence from Crepis tectorum (Asteraceae).

PREMISE OF THE STUDY: Small, autogamous flowers have evolved repeatedly in the plant kingdom. While much attention has focused on the mechanisms that promote the shift to autogamy, there is still a paucity of information on the factors that underlie the reduction of flower size so prevalent in selfing lineages. In this study of Crepis tectorum, I examine the role of inbreeding, acting alone or together with selection, in promoting evolutionary reduction of flower size. METHODS: Experimental crosses were performed to produce progeny populations that differed in inbreeding and (or) selection history. Progenies were grown in two different environments and scored for flower size and other characters. KEY RESULTS: Inbreeding depressed flower and fruit size, but also caused changes in flowering time and the number of heads produced. Despite some inconsistencies in the results for the last progeny generation, the decline in flower size was persistent over generations, consistent across environments, and similar in magnitude to the effects of selection for small flower size and the floral reduction inferred to have taken place during the shift toward autogamy within the study species. The floral size reduction was largely independent of changes in overall vigor, and there was considerable adaptive potential in flower size (measured by sib analyses and parent-offspring comparisons) after inbreeding. CONCLUSIONS: The results of this study indicate that inbreeding can promote evolutionary reduction of flower size and highlight the close, persistent association between flower and fruit size in the study species.

[Determination of the mutagenic potential of inorganic compounds of some heavy metals].

The authors determined the mutagenic potential of inorganic compounds, such as tungsten, molybdenum, lead, and copper, as well as waste of a tungsten-molybdenum industrial complex engaged in the exploitation of tungsten and molybdenum deposits, and environmental components, by using a plant test system and species of wild flora. They were shown to be suitable for the determination of genotoxicity of the environment polluted with heavy metals.

Biological investigations aboard biosatellite Cosmos-782.

The Cosmos-782 flight from 25 November to 15 December 1975, carried biological experiments designed to study the effects of weightlessness on insects and fish and on gravitropism and growth in several seed varieties. Investigations carried out on Drosophila melanogaster measured the frequency of recessive lethal mutations and the change in genetic distances in the sex chromosome. The study of Fundulus heteroclitus eggs and fry compared the effects of weightlessness and artificial gravity. Plants experiments studied spatial orientation of over and underground organs of Pinus silvestris and Crepis capillaris seeds. Other investigations used Phycomyces blakesleanus to compare spatial orientation and growth and development in weightlessness and artificial gravity.

The action of space flight factors on the radiation effects of additional gamma-irradiation of seeds.

The action of space flight factors (SFF) on radiosensitivity and the effects of preflight irradiation of air-dried Crepis capillaris (L) Wallr and Arabidopsis thaliana (L) Heynh seeds aboard the spaceships of the Cosmos, Soyuz and Salyut series was studied. The results have shown that vibration and linear acceleration (VA) cause damage of the meristematic embryonic cells and simultaneously decrease the radiosensitivity of seeds. SFF enhance the effect of preflight gamma-irradiation of seeds with respect to a number of characteristics. This can be explained partly by the action of VA. The basis of all observed effects is chromosomal aberrations which are expressed in a series of successive cell divisions and which decrease the survival and fertility of plants that grow from flight-exposed seeds.

Biological investigations on the orbital station "Salyut-5".

Genetic and embryological investigations were continued on the orbital station Salyut-5. The effect of space flight factors on dry Crepis capillaris (L) Wallr seeds and seedlings, dry Arabidopsis thaliana (L) Heynh seeds, Polyporus brumalis Pers. ex. Fries culture as well as on spawn development and fish behaviour was studied. Space flight factors are shown to have adverse effects with respect to some characteristics in seeds and seedlings, and to change the morphology of the fungus. Fishes appear to adapt themselves to weightlessness.

Biological experiments carried out aboard the biological satellite Cosmos-936.

Experiments to study the effect of weightlessness on the emergence and development of cell organelles and genetic structures were carried out during 18.5 days aboard the biological satellite Cosmos-936. The experiments were conducted on the fruit fly Drosophila melanogaster Orgeon-R. Their purpose was to investigate possible chromosomal aberrations and gene mutations in the sex chromosomes of males and females. The investigations showed that the frequency of mutations in the progeny of specimens exposed to weightlessness did not differ from the controls. The experiments with higher plants were performed on the seedlings of Crepis capillaris and Zea mays grown from seeds aboard the biosatellite. The cytological examination of Crepis capillaris chromosomes demonstrated that there were no structural chromosome changes in the experimental and control variants. Maize seedlings grown in weightlessness and examined later in the laboratory showed that cells of the root meristem cultivated in weightlessness were much larger than the controls. Mitochondria of seedlings exposed to weightlessness were swollen and had a low content of membranous material.

Biological investigations of higher and lower plants aboard Soyuz 19.

Biological investigations carried out aboard Soyuz 19 consisted of three independent complex experiments. All biological materials aboard the spacecraft were kept in "Biocat" thermostats which maintained the required temperature. The objective of the experiment "Genetic investigations" was to determine the effect of space flight factors on the heredity of lower (Chlamydomonas reinhardi Dang) and higher (Crepis capillaris (L) Wallr and Arabidopsis thaliana (L) Heynh) plants, and on the radiosensitivity of plant seeds and the radiation effect of prior gamma-irradiation. The space flight factors decreased the survival of Chlamydomonas cells and A. thaliana plants of the first generation. They decreased the germination of seeds, increased the rate of chlorophyll mutations and embryonal lethals, produced no effect on the rate of visible mutations in unicellular algae, increased the rate of chromosome aberrations in root meristem cells C. capillaris, induced disturbances in mitosis of unicellular algae and modified the effect of prior gamma-irradiation. The experiment "Growth of micro-organisms" was conducted with a culture of Proteus vulgaris in a growth chamber. After return to the laboratory the experimental and control variants were studied for twenty-two tests. The control and experimental material differed in the average cell size, biomass distribution, the character of haemotaxis, the rate of cell migration over the substratum surface, dehydrogenase activity, ribosomal aggregation, and ultrastructural peculiarities of cells. The experiment "Embryological investigations" was carried out to study the effect of space flight factors on embryogenesis of the bony fish Brachyodanio rerio. No abnormalities were noted in the course or rate of the development of spawn cultivated in a special thermostat.

Effects of space flight factors on the heredity of higher and lower plants.

The effects were studied of a long-term space exposure (72 days) aboard the Salyut orbital station on the following: dry seeds of Crepis capillaris (L.) Wallr. and Arabidopsis thaliana (L.) Heynh, haploid and diploid strains of Saccharomyces cerevisiae mutant for adenine locus (ad) and strain LARG-I of Chlorella vulgaris Beijer. A modifying effect of space factors on radiobiological action of gamma-irradiation from 137Cs was determined with the higher plant seeds and Chlorella culture. For this, the material was partly irradiated prior to, and partly after the flight at doses of 3, 30 and 10 kr for C. capillaris, A. thaliana and Chl. vulgaris, respectively. It was shown that: (1) Space factors caused reduced survival of Arabidopsis seedlings and Chlorella and yeast cultures, reduced productivity of Chlorella cells, increased mutability of Chlorella and yeast cells and increased frequency of chromosome aberrations in cells of Crepis root meristem. There are, however, a few exceptions: cell germination of C. capillaris was enhanced while mutability of A. thaliana seeds declined. (2) Space factors increased the adverse effects of the pre-flight irradiation on all the parameters of the cultures tested. (3) Space factors had no genetic effect on the objects tested. They have, however, caused a stronger inhibition of seed germination and augmenting survival of A. thaliana seedlings and Chlorella cells.