Six double-stranded DNA Streptomyces bacteriophages, HotFries, Moozy, RavenPuff, Scap1, Rainydai, and SenditCS, were isolated using the phytopathogen Streptomyces scabiei as a host. These phages have been identified as Siphoviridae and members of cluster BI by genomic analysis.
Bacteriophages are known to display a broad range of host spectra, typically infecting a small set of related bacterial species. The transfer of bacteriophages between more distant clades of bacteria has often been postulated, but remains mostly unaddressed. In this work we leverage the sequencing of novel cluster of phages infecting Streptomyces bacteria and the availability of large numbers of complete phage genomes in public repositories to address this question. Using phylogenetic and comparative genomics methods, we show that several clusters of Actinobacteria-infecting phages are more closely related between them, and with a small group of Firmicutes phages, than with any other Actinobacteriophage lineage. These data indicate that this heterogeneous group of phages shares a common ancestor with well-defined genome structure. Analysis of genomic %GC content shows that these Actinobacteriophages are poorly adapted to their Actinobacteria hosts, suggesting that this phage lineage originated in an ancestor of the Firmicutes, adapted to high %GC content members of this phylum and later migrated to the Actinobacteria.
Speciation by sexual selection is generally modeled as the co-evolution of female preferences and elaborate male ornaments leading to behavioral (sexual) reproductive isolation. One prediction of these models is that female preference for conspecific males should evolve earlier than male preference for conspecific females in sexually dimorphic species with male ornaments. We tested that prediction in darters, a diverse group of freshwater fishes with sexually dimorphic ornamentation. Focusing on the earliest stages of divergence, we tested preference for conspecific mates in males and females of seven closely related species pairs. Contrary to expectation, male preference for conspecific females was significantly greater than female preference for conspecific males. Males in four of the fourteen species significantly preferred conspecific females; whereas, females in no species significantly preferred conspecific males. Relationships between the strength of preference for conspecifics and genetic distance revealed no difference in slope between males and females but a significant difference in intercept, also suggesting that male preference evolves earlier than females'. Our results are consistent with other recent studies in darters and suggest that the co-evolution of female preferences and male ornaments may not best explain the earliest stages of behavioral isolation in this lineage.
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