The Red List`s evaluation criteria are based on the “50/500 rule”. This indicates that to avoid inbreeding depression (the loss of “fitness” due to genetic problems), an effective population size of at least 50 individuals in a population is required. An emerging rule of thumb is that if a population begins to fall below several thousand individuals, it has a high probability of disappearing. “Our research suggests that the 50/500 rule is at least an order of magnitude too small to effectively avoid extinction,” says Dr. Traill. “This does not necessarily mean that populations of less than 5,000 people are condemned. But it underscores the challenge small populations face in adapting to a rapidly changing world. A long-standing idea in species recovery strategies is the so-called “50/500” rule. This states that at least 50 adults are required to avoid the harmful effects of inbreeding and 500 to avoid extinction due to the inability to develop to cope with environmental changes.
I spent the morning visiting the Quantcast team, which has some pretty exciting things in mind, and at the end I chatted with co-founder Paul Sutter about what Paul calls the “5-50-500” rule. I found it quite informative, not only as a goal to evaluate Quantcast`s progress, but more generally as a useful way to think about the steps of a startup. […] Recommendations for 50/500 rules, Red List criteria and population viability analyses. The one we missed. 100/1000 is the new 50/500. Multiply by 10 for the census population size at inbreeding and […] So, sensational analogies about the apocalypse aside, do people follow the same rule? We`re not entirely sure, but the evidence suggests that most species from very different groups follow pretty much the same trend. The 50/500 rule has been used as a conservation guiding principle for the assessment of the minimum effective population size (N(e)). There is a lot of confusion in the recent literature about how the value of 500 should be applied to assess extinction risk and set priorities in conservation biology. Here, we argue that confusion arises when the genetic basis of a short-term N(e) of 50 is used to prevent inbreeding depression in order to justify a long-term N(e) of 500 to maintain evolutionary potential. This confusion can lead to misleading conclusions about how genetic arguments alone are sufficient to set minimum thresholds for viable populations (PVPs) to assess the risk of extinction of endangered species, particularly those that point out that MVPs would need to multiply by the thousands to maintain evolutionary potential.
[…] You may remember Dick Frankham, Barry Brook and I recently wrote a review in Biological Conservation that challenges the status quo regarding the famous 50/500 “rule” in conservation management (effective population size [Ne] = 50 to avoid inbreeding depression in the short term, and Ne = […] But if you just look at the genetic arguments, the 50/500 rule is starting to collapse. As a basic assumption in many IUCN Red List criteria, it is extremely important to make the rule “correct”. Let`s get back to the details. As already mentioned, the so-called “50/500” rule has been in existence for more than 30 years and continues to be a general guideline for management in almost all circles of small population management. Basically, the rule states that to avoid inbreeding depression (i.e. loss of “fitness” due to genetic problems), an effective population size (Ne) of at least 50 individuals in a population is required. To avoid eroding evolutionary potential (the ability of a population to evolve to cope with environmental change), a Ne of at least 500 is required. […] The 50/500 Rule in Conservation Great blog post presenting the results of a new article (sub) on why the 50/500 rule in conservation is too weak. The argument is mainly based on the fact that 50 and 500 are actual population sizes and not census sizes, a fact overlooked in the application of the idea. […] Under the direction of the eminent conservation geneticist, Professor Richard Frankham, and including my longtime partner in scientific crime, Professor Barry Brook, we have just published a comprehensive review of the “50/500” rule that has existed since the work of Franklin and Soulé in 1980. To avoid eroding evolutionary potential (the ability of a population to evolve to cope with future environmental changes), an effective population of at least 500 people is needed.
[…] to identify the concept of the avenue effect, and this is also the essential reading of my book. We now know that inbreeding depression (a type of avenue effect) contributes massively to the risk of extinction, and so we should take Warder Clyde Allee`s concept seriously (although Warder never […] This means that the number of effective individuals is less than the total population. On average, the ratio is about 0.1 to 0.2; That is, an effective individual (genetically speaking) for the five to ten members of the population. “Often they aim to entertain dozens or hundreds of individuals when thousands are actually needed. Our review found that populations below about 5,000 had unacceptably high extinction rates. This suggests that many conservation restoration goals are simply too small to do much good in the long run. There is a clear trend towards insularity, survival of genetic bottlenecks, and the r strategy to allow for much lower-than-average MVPs. Conversely, taxa that are easily affected by inbreeding depression – with high MVPs – are often decidedly K strategists, with low population densities, while occurring over a wide range. An MVP of 500 to 1,000 has often been given as an average for terrestrial vertebrates when inbreeding or genetic variability is unknown.   When inbreeding effects are included, MVP estimates for many species are in the thousands. Based on a meta-analysis of traill et al.
about vertebrates “an inter-species frequency distribution of MVP with a median of 4169 individuals (95% CI = 3577–5129)”.  […] of in situ and animal management in captivity (you can read the last argument of the revision here). Apart from that, it is useful to visualize some of the data on Ne from the current […] This idea fits perfectly with the image of Noah`s animals walking “twice two” in the ark. But the science of “minimally viable populations” tells us a different story. As usual, VCMike your best ideas come when you quote other people! For those who don`t know, Dick Frankham was also my thesis supervisor in the late 1990s. That must be the reason I became so good. 🙂 Well, an “idealized” population is just that – it`s not a real thing. In a perfect world, a breeding pair would be completely independent of it, so it would have no chance of producing offspring with genetic defects, since each parent does not give harmful alleles to a specific place.
Of course, real populations rarely behave this way, so some pairs have some degree of “kinship.” You know what happens – when the population becomes smaller, the chances of breeding with a parent increase and you get inbreeding. There is, of course, a discussion about the accuracy of PVAs, as a variety of assumptions are usually required for forecasting; The important consideration, however, is not absolute accuracy, but the dissemination of the concept that each species actually has an MVP that can be approximated, at least in the interest of conservation biology and biodiversity action plans.  Thank you for such an interesting idea! We will look at it and come back with observations, perhaps 🙂 This article was originally published on The Conversation.