The “Balance of Nature”—Evolution of a Panchreston
In this new perspective, Daniel Simberloff discusses the notion of a “balance of nature”. He takes us on a historical tour, from the early Greeks – who believed balance was maintained by the gods (with aid from human and animal sacrifice) – via the interventionist God of the Middle Ages, to the delicate balance implied by Darwin, with constant emphasis on competition. Recent research, by contrast, recognises the term as somewhat defunct, and the more dynamic aspects of nature, punctuated with natural and human-induced disturbances, are emphasised. Yet the idea of a “balance” lives on in the popular imagination.
Sticky Chromosomes Get Stretched
The characteristic ‘X’ shape of chromosomes during cell division arises because the sister chromatids remain connected at the centromere, a region of the chromosome that contains long stretches of repetitive and physically compacted DNA called heterochromatin. A new study in PLOS Biology this week dissected the roles of heterochromatin and the centromeres in cohesion of sister chromatids. Raquel Oliveira, William Sullivan and colleagues tested fruit fly strains where stretches of heterochromatin were inappropriately inserted in chromosomal regions distant from the centromere. They found that this did cause increased cohesion (through greater loading of the clamp protein Cohesin), and therefore induced stretching of the chromosomes during cell division. This finding could be of some relevance to human cancers, where rearrangements involving heterochromatic regions often occur.
To Mate or not to Mate: How Female Flies Choose
Although male courtship has been studied extensively in Drosophila, the neural basis for female receptivity remains unknown (see also this paper on a related topic). Joseph Moeller Schinaman, Rui Sousa-Neves and colleagues attempted to map some of the circuitry of female mate choice, exploiting a quirk of flies that have mutations in the gene encoding the transcription factor DATILÓGRAFO. The gene is named – in Portuguese – after the odd typist-like leg movements of the mutant flies, but the researchers also noticed that the female mutants had no interest in the males. They established that DATILÓGRAFO was required in three regions of the brain, including the olfactory lobe, for normal mating receptivity.