Prediction of the minimum effective size of a population viable in the long term

Abstract

The establishment of the minimum size for a viable population (MVP) has been used as a guidance in conservation practice to determine the extinction risks of populations and species. A consensus MVP rule of 50/500 individuals has been attained, according to which a minimum effective population size of Ne = 50 is needed to avoid extinction due to inbreeding depression in the short term, and of Ne = 500 to survive in the long term. However, the large inbreeding loads (B) usually found in nature, as well as the consideration of selection affecting genetic diversity, have led to a suggestion that those numbers should be doubled (100/1000). Purging of deleterious mutations can also be a main factor affecting the suggested rules. In a previous simulation study, the reduction of B by the action of purging pointed towards an MVP intermediate between the two rules for short term survival. Here, we focused on the consequences of purging in the establishment of MVPs for long term survival. We performed computer simulations of populations under the action of purging, drift, new mutation, and environmental effects on fitness to investigate the extinction times and the loss of genetic diversity for a range of effective population sizes. Our results indicate that purging can reduce the MVP needed for a population to persist in the long term, with estimates close to Ne = 500 for species with moderately large reproductive rates. However, MVP values appear to be of at least Ne = 1000 when the species´ reproductive rates are low.

Co‐occurrence patterns of endangered Sakhalin taimen and introduced rainbow trout in Hokkaido, Japan, inferred by environmental DNA metabarcoding

“…Based on this relationship (435.4 copies per 380 ± 45 individuals), an approximate estimate can be made of the population abundance (Figure 3). This suggests that only seven river systems in Hokkaido meet the general requirement for the minimum effective population sizes for a population to persist in the long term; namely, the effective population size of 500 or 1,000 according to Franklin (1980) or Pérez‐Pereira et al (2022) respectively. Given that the effective population size is usually smaller than the census population size in the wild (Araki, Waples & Blouin, 2007), at least 10 out of the 17 river systems (58.8%) host Sakhalin taimen populations potentially at risk of extinction.…”

Testing the efficacy of different molecular tools for parasite conservation genetics: a case study using horsehair worms (Phylum Nematomorpha)

“…For C. formosanus, however, way more events were recorded from the Stairway Plot analyses. That said, it is surprising that this species, which is regarded as the most common in Taiwan, is showing signs of decline-although the current Ne should still be way larger than enough to sustain the population (Franklin, 1980;Pérez Pereira et al, 2022). The recent demographic decrease might be the result of extirpation events (Legendre et al, 2008) possibly caused by changes in land use in Taiwan (De Vivo and Huang, 2022), given that hairworms are sensitive to human activities and pollution (Poinar, 2008;Sato et al, 2014;Chiu et al, 2016;Achiorno et al, 2018).…”

“…These tools can be important for inferring a population’s cryptic genetic diversity and changes in effective population size ( Ne ) over time (Criscione, 2013, 2016; Strobel et al , 2019). Ne is known to greatly influence the genetic diversity and viability of populations (Criscione et al , 2005; Franklin, 1980; Pérez□Pereira et al , 2022), but estimating it in parasites may come with some caveats depending on the studied system (Criscione and Blouin, 2005; Strobel et al , 2019). That being said, estimates of Ne can be helpful for considering the taxa’s conservation status (Franklin, 1980; Pérez□Pereira et al , 2022).…”

“…Ne is known to greatly influence the genetic diversity and viability of populations Franklin, 1980;Pérez Pereira et al, 2022), but estimating it in parasites may come with some caveats depending on the studied system Strobel et al, 2019). That being said, estimates of Ne can be helpful for considering the taxa's conservation status (Franklin, 1980;Pérez Pereira et al, 2022). Unfortunately, the current lack of data makes it difficult for researchers to enact timely conservation plans, putting some species at risk of extinction (Carlson et al, 2017(Carlson et al, , 2020Poulin, 2021).…”

Global assessment of effective population sizes: consistent taxonomic differences in meeting the 50/500 rule

“…The 50/500 rule recommends a minimum N̂ e of 50 to avoid inbreeding in the short-term, and a minimum N̂ e of 500 to allow sufficient genetic diversity for adaptation in the long-term (Franklin, 1980; Jamieson & Allendorf, 2012). Although the 50/500 criteria is increasingly incorporated into minimum viable population size assessments (e.g., IUCN Red List, Convention on Biological Diversity; Hoban, 2020; Laikre et al, 2020; Mace et al, 2008), the broad applicability of this criteria in conservation is heavily debated (Frankham et al, 2013; Franklin et al, 2014; Jamieson & Allendorf, 2012; Laikre et al, 2021), and some authors recommend increasing the minimum thresholds to 100 and 1000 to maintain populations’ fitness and adaptive potential (Frankham, 2014; García-Dorado, 2015; Jamieson & Allendorf, 2012; Pérez-Pereira et al, 2022).…”