sou · GZB337 · 2011-04-20 00:00:00 — 2005), population sizes of the other sub-populations in the historical range are also low, leading to significant conservation concerns (Aspi et al. 2006, Aspi et al. conservation concern for all the sub-populations in the proximate historical geographical range, the evaluation panel finds it a realistic goal to obtain Favourable Conservation Status for the Fennoscandian- Karelian grey wolf population, with effective population sizes (Ne) that secure a potential for future evolution (500 or more). This number corresponds to census population sizes (N) of some thousands (at least 3,000–5,000) individuals. Population sizes of these magnitudes would secure long-term sustainability of the population, addressing both genetic and demographic requirements (Frankham et al. 2002; Traill et al. The evaluation panel stresses that the key to obtaining Favourable Conservation Status involves transnational collaboration and agreements involving , , and . Emphasis must be on 1) securing sufficient connectivity among the present sub-populations, preferably through natural migration or alternatively artificial translocations and 2) securing sufficiently high population sizes within the present fragments (subpopulations) of the historical range. All together this could lead to a total population size fulfilling the requirements for Favourable Conservation Status. Can the Scandinavian population in itself meet requirements for Favourable Conservation Status? In the proceedings the panel concluded that Favourable Conservation Status should be evaluated and achieved at the level of the historical population range, in practical terms Fennoscandia and Karelia. In practice this can be considered a feasible goal, disregarding political aspects. For arguments sake, however, the panel also briefly considered whether Favourable Conservation Status could be achieved solely within the Scandinavian subpopulation, thus disregarding the sub-populations from Karelia and and disregarding the definitions of populations and reporting units put forward in the reporting guidelines for the EU Habitat Directive Article 17. The panel finds that the most imminent genetic problem with the Scandinavian sub-population is the extremely high inbreeding coefficient of ca. This level of inbreeding is greater than that found in offspring from matings between full siblings, and substantial inbreeding depression due to a genetic load (harmful alleles that will be expressed under inbreeding) has been demonstrated in Scandinavian wolves (Liberg et al. 2005, Räikkonen et al. Inbreeding cannot be reduced by increasing population sizes, although this would have the positive effect of reducing the rate of future inbreeding accumulation. A reduction of inbreeding can only be achieved by introducing new genetic material to the sub-population (Frankham et al. , either natural immigration or artificial translocation is required to reduce inbreeding to an acceptable level. Once this has been achieved, the census population size of the Scandinavian subpopulation would have to number in the thousands (3,000–5,000) in order to fulfill the criteria for Favourable Conservation Status. In principle, it would thus be possible to obtain Favourable Conservation Status for the Scandinavian sub-population but 1) this does not address conservation requirements for other remnants of the historical wolf population and 2) although the evaluation panel focuses on biological issues, it is the impression of the panel that a grey wolf population size of this magnitude is not politically acceptable. Meeting requirements for Favourable Conservation Status on a transnational scale. Given that FCS for the wolf cannot be achieved within the Scandinavian peninsula, what should contribution to the extended population be? It will be close to impossible to give an exact figure for this, since it depends on a number of factors, for instance the sizes of the Scandinavian, Finnish and Russian subpopulations, the level of gene flow between them and the area of suitable habitat found in the different countries. Considering only the size of the countries/regions (: ; : ; : ; Kola-Karelia with neighbouring provinces: ), a population of 3 000 wolves divided equally would give 700, and 500 each and 1 300 animals. However, taking the amount of suitable habitat, human habitations and infrastructure into account, the available areas would have to be adjusted substantially. But numbers might still need to be considerably higher than today in the Scandinavian peninsula. In short, a number of considerations will have to be taken into account when assessing the contribution of individual countries to a transnational population with Favourable Conservation Status, but the relative proportions of suitable habitat could be a good starting point for the assessment. The different hypotheses presented by the research groups regarding recommended population sizes, immigration rates and urgency of decreasing inbreeding. The panel was asked to identify and evaluate the different hypotheses presented by research groups concerning recommended population sizes, immigration rates and the urgency of decreasing inbreeding. These opposing views are most clearly expressed in the recommendations provided in a report to in 2009 (Liberg et al. In this report, two different sets of recommendations are provided. The first set is provided by Liberg, Sand, , and Bensch; in the following, we refer to this group of scientists as the Liberg et al. The second set of recommendations is provided by Laikre and , and in the following they are referred to as the Laikre & group. Despite the disagreements among groups, the evaluation panel also finds it important to stress that it is impressed by the high quality of the science that has been conducted during the monitoring and assessment of the conservation status of Scandinavian wolves. Reconstructing a pedigree of a wild carnivore population must be considered a unique achievement, and overall the conservation ecology and genetics research on Scandinavian wolves ranks very highly in the conservation biology sciences. I) The views and recommendations of the Liberg et al. group are described in the following. 1.First, they clearly acknowledge that the Scandinavian wolf subpopulation is strongly inbred and that there are signs of inbreeding depression. However, they also do not find that the signs of inbreeding depression are that severe. An average size of 3.5 is not alarming, although a size of 6 is observed from 3 pairs of non-inbred Scandinavian wolves. The population is still growing by 10–per year so the loss of genetic diversity is going slower than expected. At the same time, however, the problem of inbreeding and inbreeding depression cannot be ignored, so securing gene flow into the subpopulation is considered a necessary step, but not to the extent that immediate measures should be taken and inbreeding should be drastically decreased. 2.Further, they emphasize a published study (Bensch et al. 2006) that seems to suggest a mechanism of general selection for high heterozygosity which should slow down the expected loss of heterozygosity in the population. 3.Given that they do not find the level of inbreeding to be immediately alarming, they recommend an adaptive approach starting with the least controversial management options. They therefore recommend an initial goal of having 2 effective immigrants per generation in order to decrease inbreeding. They further recommend waiting for natural immigration, i.e. over a five year period natural immigration corresponding to 2 effective migrants should occur. If this goal is not achieved, then other measures, notably translocation of wolves must be considered. The genetic and demographical status of the population should still be followed and the pedigree upgraded and continued. 4.In order to facilitate natural immigration of wolves from , a protected corridor along the coast is suggested. 5.Concerning the longer-term recommendation by Allendorf & (2002) that conservation programs should seek to retain of exisiting heterozygosity over a 100 year period, the Liberg et al. group suggests lowering the goal to retaining heterozygosity over 100 years. Given the estimated generation time of wolves this corresponds to an effective population size (Ne) of 50. Moreover, assuming a ratio between effective population size (Ne) and census population size (N) of 0.25, this corresponds to a minimum census population size of 200 However, given the uncertainty of estimating Ne/N ratios a census population size of 300 is recommended. The evaluation panels assessment of these issues is provided below, point by point. 1.The panel certainly agrees that the Scandinavian wolf subpopulation is strongly inbred and that there are signs of An overall inbreeding coefficient of ca. 0.3 must be considered very high and should be taken very seriously. Moreover, it has been found that the genetic load in the sub-population corresponds to ca. 6 lethal equivalents associated with reproduction (litter-size-reducing equivalents) (Liberg et al. 2005) and 5.4 lethal equivalents associated with recruitment to a breeding postion (breeding-failure equivalents) (Bensch et al. This must be considered a high genetic load. There are apparently many detrimental recessive alleles in the population, which should raise significant concerns that inbreeding leads to significant inbreeding depression. The statement that the sub-population has so far grown by 10–per year despite inbreeding (and illegal hunting) is correct, but this cannot be taken as evidence that inbreeding depression does not occur (in comparsion, in the average growth of population in 1996–2006 has been ; λ= 1.211). Given that there is an abundance of prey and that the Scandinavian wolf subpopulation is far below carrying capacity, it is not a paradox that the population grows despite inbreeding depression. This can be considered a balance between population growth rate in a beneficial environment and lowered fitness (and thereby population growth) resulting from inbreeding depression, where the effects of the beneficial environment still overrides the effects of inbreeding depression. With increasing inbreeding in the years to come (unless counteracted by immigration) this balance might turn. Moreover, the overall low genetic diversity due to the extreme founder event of the sub-population means that there is limited genetic variation to respond to sudden events, notably emergence of new diseases, in which case the overall subpopulation could be at risk. In total, the evaluation panel finds that introduction of new genetic material into the subpopulation should have a high immediate priority. 2.The panel read and discussed the paper by Bensch et al. (2006) with much interest. The panel finds it plausible that the observation of maintenance of heterozygosity at the analysed markers is genuine. Indeed, patterns resembling this have also been observed in some inbreeding experiments with model organisms such as Drosophila (Demontis et al. However, the panel would dispute the interpretation that this provides evidence for a general mechanism of selection for heterozygosity (a genome-wide effect) as opposed to selection against homozygotes at specific loci with deleterious alleles (a genic effect). Given the extremely low number of founders of the Scandinavian sub-population linkage disequilibrium is expected to be very high. , selection against homozygotes at a specific locus could affect a large region of the chromosome, including the analysed molecular markers. As a likely alternative hypothesis the panel suggests that the observed results actually represent inbreeding depression in action; there is strong selection against deleterious homozygotes at specific loci, and due to the strong linkage disequilibrium hitch-hiking selection extends far along the chromosomes, which includes the studied markers. This interpretation is also consistent with recent population genetic theory. Pamilo and Pálsson (1998) found that selection against homozygous deleterious alleles is expected to cause increased heterozygosity at linked marker loci when there is strong linkage disequilibrium in small populations. They also noted that this effect may generate associations between fitness and heterozygosity at individual markers suggestive of selection for heterozygosity. It should also be noted that a later study of Scandinavian grey wolves using many more markers (250 microsatellite markers as opposed to 31 in Bensch et al. 2006) failed to observe a general homozygote excess (Hagenblad et al. 2009), although differences in the study designs make it difficult to draw a direct comparison between the two studies. In total, the panel finds that the results suggesting selection for heterozygosity are scientifically interesting, but the interpretation is far from clear-cut. The panel discourages using this result in a practical conservation context as an argument for accepting high inbreeding levels. It should be added that during the panels discussions with the Liberg et al. group there was also a general consensus about interpreting these results cautiously and not using them as a scientific basis for management recommendations. 3.It is not evident why it is recommended that immigration should be at least two effective migrants per generation. Assuming an effective population size of 50 and assuming immigration from an infinitely large population, the results provided by Laikre & (Fig. 2.a) in the report by Liberg 4.The evaluation panel finds that the suggestion to create a protected migration corridor along the Bay of Bothnia coast could be a major step towards connecting the wolf subpopulations in and . This could greatly increase the for obtaining Favourable Conservation Status for the total Fennoscandian-Karelian wolf population. The panel is unable to provide detailed comments on the expected efficiency of a corridor of the size and location suggested. 5.The panel discussed and evaluated the guidelines by Allendorf & (2002) stating that the recommended effective population size should fulfil the criterion that of heterozygosity be retained over a 100 year period. The panel also discussed this issue with one of the authors (). On one side, the panel finds it important to have a specific and welldefined goal for how much loss of genetic diversity that can be accepted. On the other side, there is not really a strong biological argument as to whether the target should be , or for that matter. In general, the panel finds that it is not a fruitful discussion whether the target should be 90 or . The key issue for the Scandinavian grey wolves is the demographic history and its genetic consequences. The extremely low number of founders and the lack of gene flow have led to very high inbreeding coefficients. , the panel finds that the target should be to bring the inbreeding down to an acceptable level using the combination of the two parameters immigration and population size that will fulfil that target within a reasonable time frame. II) The views and recommendations of the Laikre & group are described in the following, based on their contributions to the same report (Liberg et al. 1.Laikre and suggest an international metapopulation of Ne= 500-5000 to sustain evolutionary potential. If Ne /N = 0.25, then this corresponds to a census population size of 2000- 20000. This goal should be achieved by international collaboration with the neighbouring countries. 2.If short term viability is considered, then the recommendations of Allendorf & (2002) should be followed (retention of of existing heterozygosity for 100 years) This would correspond to Ne= 200. It is discussed which among a range of suggested Ne /N that should be assumed. However, if it is assumed that Ne /N are 0.20 – 0.25, then this would correspond to a recommended population size of 800–1000 individuals (as opposed to 300 recommended by the Liberg et al. 3.If only around 200 wolves are allowed to persist, then the goal of retaining heterozygosity can only be achieved by immigration corresponding to at least 4 effective migrants per generation. 4.It is argued that inbreeding should be reduced by immigration by taking immediate measures (natural gene flow or translocations). This is due to the fact that the inbreeding coefficient already is very high, that there is a considerable genetic load in the population and that significant inbreeding depression already occurs. A goal of reducing the current inbreeding coefficient to < 0.1 could be achieved over 5 to 20 years by immigration corresponding to 5 to 10 effective migrants per generation. This depends to a significant extend on the effective population size of the donor population (e.g. ); the lower the Ne in the donor population, the more difficult will it be to decrease inbreeding. 5.It is argued that inbreeding depression is probably underestimated as apart from size it is not specifically monitored. Observed defects such as cryptorchism are likely to be heritable and reflect recessive deleterious alleles. In this case, a frequency of observed cryptorchism of 0.08 would correspond to a frequency of 0.27 of the deleterious recessive allele. Simulations suggest that because deleterious alleles have already reached such high frequencies, very high effective population sizes would be required (Ne of ca. 200) in order to avoid further increase of recessive allele frequencies. 6.Pedigree information could be used more efficiently, e.g. by using the relative kinship estimates of the individuals to identify the genetically important individuals that should be protected from hunting. The evaluation panels assessment of these issues is provided below, point by point. 1.The panel agrees with the recommendation of aiming towards an international metapopulation with an effective population size of at least 500. The panel reached a similar conclusion when evaluating the options for obtaining Favourable Conservation Status (see above). However, as a small note the panel would prefer not to use the term metapopulation in this context, as in many definitions this concept involves extinction-recoloniza- tion dynamics among sub-populations, but there is no evidence of these dynamics in undisturbed grey wolf populations. 2.As explained in the panels evaluation of point 5 regarding the Liberg et al. group (see above), the panel on one side finds it important to have a stated conservation goal, but on the other side also finds it somewhat arbitrary that the goal should be to retain at least heterozygosity over 100 years. However, the real issue concerns the high level of inbreeding in Scandinavian grey wolves and how to reduce it. 3.The panel agrees with the rationale per se, but again finds that emphasis should be on reducing the level of inbreeding. 4.The panel agrees that the level of inbreeding is very high and even without further evidence of physical defects caused by inbreeding depression, the high genetic load already demonstrated corresponding to six lethal equivalents for size and 5.4 lethal equivalents for recruitment to breeding status should raise significant concerns (Liberg et al. 2005; Bensch et al. It can always be argued to which level inbreeding should be reduced; reducing it to below 0.1 over a time scale of 20 years appears to be a realistic goal. In any case, considering the genetic load and very high inbreeding coefficient in Scandinavian grey wolves the panel finds it important to take steps to introduce new genetic material as soon as possible. As a matter of fact, the panel has some concerns that the recommendations for number of effective migrants may be on the optimistic side. These recommendations are made on the basis of Fig. 2.a in Laikre & Rymans contribution to the report, which specifically assumes immigration from an infinitely large donor population into a Scandinavian sub-population with Ne of 50. However, the nearest donor population (the Finnish subpopulation) is far from infinite, and Ne has been estimated at ca. 40 (Aspi et al. This would suggest that Fig. 2.b provides a more realistic scenario, where both the donor population and the Scandinavian subpopulation have an Ne of 50. Fig. 2.b shows that under these circumstances it will be difficult to obtain a permanent decrease of inbreeding coefficient. However, Fig. 2.b may also not be realistic, if gene flow occurs from presumably larger sub-populations (notably Karelia-Kola) into the Finnish sub-population, or if the effective gene flow is substantially greater than that expected from neutral expectations – as has been observed in several cases of genetic rescue (e.g. et al. 2002; Saccheri & Brakefield 2002). The true picture is expected to lie somewhere between Fig. 2.a and 2.b. The panel would recommend further analyses, for instance using individual based modelling as conducted by in another part of the report (Liberg et al. 2009), which should specifically take the costs of inbreeding into account. These simulations could involve immigration into a Scandinavian subpopulation of Ne=50 from a Finnish subpopulation of Ne=40 which again is connected by gene flow involving a larger Karelian-Kola population of Ne=100. This type of approach might provide the most realistic tool for determining the number of effective migrants required for reducing the inbreeding coefficient below 0.1. 5.The panel agrees that inbreeding depression is likely to have been underestimated as it has not been specifically monitored. It is possible (though not proven) that the observed physical defects could reflect inbreeding depression due to homozygosity for deleterious recessive alleles. If this is indeed the case, then it is correct that physical deformities of a relatively low frequency (e.g. 0.08) corresponds to a high frequency (e.g. 0.27) of the deleterious recessive allele. It is also correct that if deleterious recessive alleles have been allowed to reach such high frequencies then there is a non-negligible risk that they may spread further due to random genetic drift. The simulations by Laikre & illustrate this point. However, the conclusion that Ne should be at least 200 in order to avoid further spread depends on the specific allele frequencies and the assumed selection coefficients. The panel therefore does not regard an Ne of 200 as a specific management recommendation, but rather consider these simulations as illustrating the seriousness of the inbreeding that has accumulated and the need for reducing inbreeding before it increases further. 6.The panel agrees that the pedigree represents a unique resource that should be utilized as much as possible in practical management. This issue was discussed with the Liberg et al. group, who expressed a high awareness of this issue. The panel was informed that the pedigree was immediately available on request, to scientists and the general public alike. There was a general consensus that the pedigree should be used to identify individuals that were particularly genetically valuable to the subpopulation, e.g. by representing an important part of the founder genetic diversity or showing particularly low kinship with other individuals. These individuals should then be protected from hunting. However, the viewpoint was also expressed that micro-management would not be feasible, where particular individuals with high kinship and inbreeding were targeted for hunting, based on the pedigree information. The panel finds that the pedigree is particularly valuable for monitoring inbreeding depression, which would also necessitate further detailed recording of emerging physical defects or negative developments in important life-history parameters. The Liberg et al.