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This Week in Nature: Feb 8, 2018

In this week's Nature, an international research team presents an analysis of the genomes of 60 different citrus varieties ranging from the Chinese mandarin to the Chandler pummelo, providing a new evolutionary framework for this genus of fruit plants. The researchers find that today's citrus trees are descended from at least 10 natural citrus species, and propose that citrus diversified during the late Miocene epoch through a rapid southeast Asian radiation that correlates with a marked weakening of the monsoons. "A second radiation enabled by migration across the Wallace line gave rise to the Australian limes in the early Pliocene epoch," they report. In looking at the domestication of commercial citrus fruits, the investigators show that genes from the pummelo may have influenced mandarins. GenomeWeb also covers this, here.

And in Nature Ecology & Evolution, US and German scientists publish the genome sequence of the marbled crayfish, a new and invasive species of freshwater crayfish believed to have resulted when the related slough crayfish, which are often kept as pets, acquired a third full set of chromosomes. The researchers sequenced the genomes of 11 marbled crayfish originating from both the wild and the pet trade, as well as slough crayfish and other related species. They found that the marbled crayfish are almost genetically identical, but that one set of chromosomes is distinct from the other two — indicating that the animals descended from two distinct slough crayfish. Further analysis indicates that the marbled crayfish population has exploded in the past 10 years and now numbers in the millions. "Our study closes an important gap in the phylogenetic analysis of animal genomes and uncovers the unique evolutionary history of an emerging invasive species," the authors write. The Scan has more on this, here.