If asexual animal species are rare, species with asexual females and rare males are even more rare. What’s more, their hybrid offspring were healthy and fertile, too. The males couldn’t mate with females of their own population, but they readily had sex with other species. The males were exceedingly rare–around one in thousand in many cases, and around one in a hundred in a few. And yet in most of the populations they studied, they discovered a few males. The females in these populations can reproduce on their own. They reared cysts from dozens of populations and closely examined the offspring over the course of two generations. In a paper appearing in the Journal of Evolutionary Biology, Marta Maccari of the University of Hull and her colleagues describe a massive survey of brine shrimp from across Europe and Asia. Cornell scientists have suggested that they have remained asexual because they’ve found a way to resist parasites that’s as good as sex– by drying up and blowing away from their pathogens.īut there are other puzzles to the evolution of sex. If the advantages of sex overwhelm its costs for 9,999 species out of every 10,000, then why is the opposite true in the remaining one? One lineage of microscopic animals called bdelloid rotifers has been asexual for 80 million years. To better understand the evolution of sex, a number of biologists are looking to the exceptions to the rule. Populations of sexual animals may be less prone to going extinct because they can adapt to more niches. Or perhaps the rarity of asexual animals is the result of evolution playing out not in short-term competitions, but over vast stretches of time. Perhaps that’s a cost too great to balance the advantage of giving up fathers. That’s a lot of extra DNA to build when a cell divides–which requires a lot of phosphorus and other ingredients. Very often, when an asexual lineage emerges, it gains an extra set of chromosomes. There may be different explanations for different cases. Defenses against ever-evolving parasites might be especially important. Maybe sex lets adaptations evolve faster, because mothers and fathers can combine genes into new combinations. Scientists have given this question a lot of thought, and they’ve come up with some possible answers that they’ve been testing in recent years. Sex must have a powerful advantage that overcomes its disadvantage–what the late biologist John Maynard Smith dubbed the two-fold cost of sex. Down with sex, in other words.īut this has only occurred in only about one in every ten thousand species of animals. Out in the wild, this proliferation should mean that the genes for male-free reproduction should quickly dominate populations. It won’t be long before the asexual population is far bigger than the sexual one. So only half of the sexual population can produce eggs, while every individual in the asexual one can. Sexual species typically produce a roughly even ratio of sons and daughters. Let’s say you’ve got a sexual pair of male and female shrimp in one tank, and two asexual females in the other. You can take that picture of sea monkeys and wipe Dad out.įrom an evolutionary perspective, this father-free way of life has a lot going for it. Their eggs can develop into healthy embryos–and, eventually, adults–without the need of sperm. And in a lot of populations, the females have no need for males. Sea monkeys don’t live in families, for one thing. The real life of sea monkeys (brine shrimp, or Artemia) is a pretty far cry from Ozzie and Harriet. If you are looking for help with one of our products or services, please visit be respectful of copyright. Public archives from lists can be found here. Sync-dev - Firefox sync development discussions Nightly-testers - discussion of features and behavior changes in nightly builds Governance - Discussion of the governance and running of the Mozilla project The google group lists can be subscribed to via the links below or by sending email to the address - product releases and other announcementsĭev-media - For discussion around media in browsers (Video, Audio, WebRTC, etc.)ĭev-platform - discussions around web platform development (gecko)ĭev-security-policy - security-related policies, governance, and related topics including discussion of Mozilla's Root Store Policy and the NSS root certificate store.ĭev-tech-crypto - mozilla's crypto code discussion listĭev-tech-gfx - Gecko platform graphics mailing listĭev-tech-network - Mozilla's network layerĮnterprise - development of features and management of Mozilla products like Firefox for Enterprise environments Some lists remain active and have moved elsewhere. We invite you to join our discussions across all aspects of Mozilla, product development, and maintaining the Open Web in our Discourse forums. Legacy Mailing Lists Mozilla's 'mailman' service has been decommissioned.
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