Abstract.-Incipient sexual isolation between genotypes, lines, or populations of the same species is commonly measured in Drosophila by choice tests. Results of these tests are known to be influenced, in an undetermined manner, by the mating propensity of competitors and by discriminatory factors during courtship. We have approached the problem by measuring male and female propensities in separate, independent tests, and by examining whether these estimates could explain the results of the choice tests. First, male and female choice tests were used to measure sexual isolation between populations of Drosophila melanogaster and between populations of D. simulans. Significant deviations from random mating occurred in 31 out of 48 tests, in agreement with the propensity values of the tested genotypes. We conclude that mating propensity instead of discrimination is directly involved in the estimation of sexual isolation in our populations, and advise against the application of male and female choice tests to assess intraspecific isolation without a proper knowledge of the mating propensities of competing individuals. Second, multiple choice tests were used to assess isolation between D. melanogaster populations. In examining the dynamics of matings throughout the test, we show that if competing individuals differ in mating propensities and tests are long enough to allow most matings to happen, a spurious sexual isolation can appear. We recommend that multiple choice tests be terminated once 50 percent of matings had been observed.Key words.-Drosophila, mating choice tests, mating propensity, sexual isolation.Received March 10, 1997.The role of sexual isolation in species formation is one of the most interesting questions in evolutionary biology. Sexual isolation is a form of reproductive isolation arising from behavioral differences between potential mates. The elaborate courtship of most Drosophila species provides good material for the study of sexual behavior. Since Sturtevant's (1915) pioneering work, students of Drosophila have tried to understand how mating differences and sexual selection could lead to speciation.At the intraspecific level, incipient sexual isolation can be seen as a tendency to mate homogamically rather than heterogamically. The underlying divergence in mating behavior between two conspecific strains can be studied in different ways. Unfortunately, a direct analysis of behavioral differences is laborious, time-consuming, and requires a lot of practice and experience (Spiess 1970;Burnet and Connolly 1981;Cobb et al. 1985Cobb et al. , 1986. As a result, the most commonly used designs for measuring sexual isolation in Drosophila are the male choice, female choice, and multiple choice tests (see Parsons 1973), which measure the frequencies of intra-and interstrain matings. The male choice test consists on introducing a male from one strain with a female from his own strain and a female from another strain, in a mating chamber, and recording the types of mating that occur. In the female choice tes...

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Members of the Streptomyces albidoflavus clade, identified by 16S rRNA sequencing and phylogenetic analyses, are widespread among predominant terrestrial lichens (Flavoparmelia caperata and Xanthoria parietina) and diverse intertidal and subtidal marine macroalgae, brown red and green (Phylum Heterokontophyta, Rhodophyta, and Chlorophyta) from the Cantabrian Cornice. In addition to these terrestrial and coastal temperate habitats, similar strains were also found to colonize deep-sea ecosystems and were isolated mainly from gorgonian and solitary corals and other invertebrates (Phylum Cnidaria, Annelida, Echinodermata, Arthropoda, and Porifera) living up to 4700-m depth and at a temperature of 2-4 °C in the submarine Avilés Canyon. Similar strains have been also repeatedly isolated from atmospheric precipitations (rain drops, snow, and hailstone) collected in the same area throughout a year observation time. These ubiquitous strains were found to be halotolerant, psychrotolerant, and barotolerant. Bioactive compounds with diverse antibiotic and cytotoxic activities produced by these strains were identified by high-performance liquid chromatography (HPLC) and database comparison. These include antibacterials (paulomycins A and B), antifungals (maltophilins), antifungals displaying also cytotoxic activities (antimycins and 6-epialteramides), and the antitumor compound fredericamycin. A hypothetical dispersion model is here proposed to explain the biogeographical distribution of S. albidoflavus strains in terrestrial, marine, and atmospheric environments.

The lack of effective governance is a major concern in small-scale fisheries. The implementation of governance that encompasses the three pillars of sustainability (social, economic, and ecological) is still a worldwide challenge. We examined nine stalked barnacle fisheries (Pollicipes pollicipes) across Southwest Europe to better understand the relationship between governance elements and sustainability. Our results show that nested spatial scales of management, the access structure, co-management, and fisher’s participation in monitoring and surveillance promote sustainability. However, it is not the mere presence of these elements but their level of implementation that drives sustainability. Efforts should be placed in the accomplishment of a minimum combination of local scales of management, access rights through individual quotas, instructive-consultative co-management and functional participation. Surpassing this threshold in future governance structures will start to adequately promote social, economic and ecologically sustainability in small-scale fisheries.

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