Genetic considerations on wolf conservation in Italy

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    Genetic considerations on wolfconservation in ItalyLuigi Boitani aa Dipartimento di Biologia Animale e dell'Uomo , Universitdi Roma , Viale dell'Universit 32, 00185, Roma, ItalyPublished online: 14 Sep 2009.

    To cite this article: Luigi Boitani (1984) Genetic considerations on wolf conservation in Italy,Bolletino di zoologia, 51:3-4, 367-373, DOI: 10.1080/11250008409439476

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  • Boll. Zool. 51: 367-373 (1984)

    Genetic considerations on wolf conservation in Italy*

    LUIGI BOITANI Dipartimento di Biologia Animale e dell'Uomo. Universiti di Rorna Vide dell'Universit9 32, 00185 Roma (1taP;r)

    ABSTRACT

    Quantitative genetic theories are being ap- plied to the wolf population in Italy to work out future conservation options. Inbreeding depression. random phenotype changes, decrease of genetic variance may affect powerfully a po- pulation'of very low numbers such as that of the Italian wolf; hybridization with dogs might have helped the wolf because of the small num- bers to overcome some of these problems at the expense of genetic "purity". From the present scanty data, three schemes for the future of the wolf are presented and their pessimistic pre- dictions discussed while stressing the urgent need of a research and monitoring program for the genetic structure of the population.

    * Pa er read at the 111 Congr. Ass. A. Ghigi, h e h in Bellagio (CO), 1983.

    (Receimd 18 December 1983)

    INTRODUCTION

    The field of conservation has. grown steadily from a first phase based mainly on empiricism to the latest approaches which have a solid background on popu- lation and ecosystem biology; I n recent years an .additional theoretical input has come from genetic and evolutionary the- ories, which have often given new per- spective to old problems of preservation and conservation: the result is a much more dynamic concept of conservation, whose first priority now is to maintain the potentialities for evolutionary proces- ses rather than to freeze the contempo- rary picture of the biological world. The first major input in this direction was given by the island biogeography theory (MacArthur & Wilson, 1967; Diamond & May, 1976; Wilcox, 1980) and, more recently, by the quantitative genetic ap- proach to the conservation of genetic di- versity (Soul& & Wilcox, 1980; Frankel & Soul&, 1981).

    These new theoretical approaches are based on an impressive amount of data from different sources that, while contri- buting to the definition of a theoretical , framework for future action, give only a few sporadic examples of real application. In this paper I present an attempt to apd ply such theories to the actual situation of the wolf (Cunir Izrpz~r) in Italy, with the aim of verifying and discussing the management options for its effective short-term and long-term conservation.

    THE WOLF IN ITALY

    Wolves survive in Italy in the central and southern Apennines, numbering about 100 in 1973 (Zimen & Boitani, 1975) on a total range of 8 500 km2; in the winter of 1983 a new census gave about 220 wolves for a total area of 13 500 km2 with a mean density of 1 wolf/60 km2 (Boitani & Zimen, in prep.), showing a

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  • L. BOITANI - 368

    remarkable increase in both number and distribution area during the ten year pe- riod.

    The structure of the distribution area and the dispersal dynamics over the last decade have just been described by Boi- tani & Fabbri (1983): two main sub-areas, in central and southern Italy. There is little, if any, possibility of genetic exchan- ge. Cagnolaro et al. (1974) reported on the changes of wolf distribution in Italy between 1900 and 1970: the wolf disap- peared from the Alps by the end of last century. At that time it was still present throughout most of the mountain and hilly areas of the Apennines. Distribution seems to have shrunk drastically in the two decades after World War I1 and we may assume that in the early Seventies the wolf populations was numerically lowest, following a strong extermination effort by extensive use of poison baits.

    Poison baits were banned in 1976 and this helped the wolf population to recover: today the wolf is slowly recolonizing the former range and the actual ecological conditions of the Apennines seem suitable to allow this dispersal up to the post-war level, i.e. about 15 000-20 000 km2 (a figure worked ont from data of Cagno- laro et a!. (1974)).

    Italy has a population of free-ranging dogs of about 850 000 and among them about 80 000 are to be considered feral, without dependency on or control from man. These dogs are distributed throug- hout the wolf range (Boitani & Fabbri, 1983): competition occurs between dog and wolf, and there is cross-breeding (Boi- tani, 1982). So far direct evidence of

  • GEKETICS OF THE WOLF 369

    In a small population the forces of ge- netic drift are especially powerful, as each generation carries only a fraction of the total gene pool of the previous generation: this process is the cause of an increase of homozygosity and a gradual loss of genetic variability, independently from the paral- lel processes of selection and mutation. Loss of genetic variability through genetic drift is much more detrimental than that caused by a bottleneck, provided that the population is allowed a fast recovery after the bottleneck (the Adam and Eve situa- tion).

    It has been clearly demonstrated that a direct correlation exists between hetero- zygosity and fitness of a population: a!- though drawn on a wide array of examples (often also contradictory), evidence for this correlation can be considered rather satisfactory (Frankel & Soul&, 1981). Pa- rallel to a decrease in heterozigosity we should expect a gradual erosion of fitness. Franklin (1980) discusses three main ef- fects that can be observed at the level of the phenotype, as consequences of genetic drifts: 1) a decrease of genetic variance, as genetic drift outweighs production of genetic variance by mutation, leading to further loss of fitness; 2) random changes in the phenotype, especially changes in the means of quantitative traits, suggesting faster evolutionary rates in highly frac- tioned populations; 3) inbreeding depres- sion.

    This last effect appears to be of para- mount importance for our issue. Inbre- eding effects are now accepted as univer- sal effects and very little can be argued against them. In inbreeding conditions the traits that will be mostly affected are those with dominance, in favour of the re- cessive oces which will be fixed; but sin- ce a disproportionate number of recessive alleles are deleterious, the phenotypic es- pression of these recessive genes will end in a decrease of fitness. In fact the first

    traits with dominance to be changed are those connected with reproduction, and me might expect inbred lines to have a signi- ficant reduction in fertility, fecundity, lit- ter size, and developmental rate. But also behavioural traits are affected by inbre- eding and it is interesting to cite the de- cline of competitive ability, as shown in experiments with Drosophilu (Latter & Robertson, 1962) and with Peroiiziscrrs (Garten, 1976) among others. As in- breeding can lead to fixation of delete- rious recessive alleles, but also to their eli- mination, the question is which of these processes has the faster rate. Data availa- ble from different sources (summarized by Frankel & Soul&, 1981) point clearly to fiiation. Hence extinction follows when the inbreeding depression is accumulated at a faster rate than any source of variation can counteract or selection can eliminate.

    Inbreeding is measured by a coefficient f which increases by 1/2Ne per genera- tion, where Ne is the effective population size. Calculation of a tolerable value for f through reliable models of population genetics is almost impossible to do owing to the very restrictive assumptions requ- ired; however, using the empirical appro- ach of some animal breeders, Franklin (1980) suggests setting at one percent the safety threshold for a natural population. It should however be pointed out that even at that rate the minimum population size required is 50 individuals. They would face a loss of 25% of their genetic varia- tion in 20-30 generations, if maintained at the same number. By working out the same formula Sou!& (1980) found that the expected number of generations, until ex- tinction due to inbreeding occurs, is about 1.5 times the effective population size at a given moment. For further comments on inbreeding theory see Cavalli-Sforza & Bodmer (1971), Wright (1977), and Fran- kel & Soul; (1981).

    Kimura & Crow (1963) gave a detailed

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  • 370 L. BOITASI

    treatment of the Ne concept and the ways to calculate it. Ne is related to N (total number) often by a factor of 3 or 4 or even more, depending on several causes, which are of extreme importance when we apply the above considerations to the ac- tual population values.

    Effective population size (Ne) depends on:

    a) unbalanced sex ratio, and can be WOK- ked out by the formula

    where Nm and Nf are the numbers of males and females respectively;

    number), b) variance in family size (or progeny

    4 N

    2 4 - 8 Ne=-

    where d is the variance in progeny number;

    c) fluctuation in population size, 1 1 1

    Ne where Nt is the effective size at the tth genera tion;

    b) non-random interbreeding because of spatial distribution pat terns.

    Based on all the above considerations, and supporting them with all the possible warning on their limits, Franklin (1980) suggests adopting as a basic rule for short- term fitness and survival Ne=50 as the minimum affordable population size, and to enlarge this figure by an order of ma- gnitude (Ne=500) if the objective is to ensure long-term survival and continuing evolutionary potential. The figure Ne= 500 seems to mark the threshold where genetic drift would be counterbalanced by

    selection forces, i.e. where genetic varian- ce is lost at the same rate as it is renewed by mutation. Although these last figures are based on rather scanty data, they can be counterchecked for their validity by mathematical models (Frankel & SoulC, 1981).

    The same authors who worked out the- se figures warn against any blind sp- plication to real situations and they in- dicate the urgent need of genetic analysis and monitoring of animal populations be- fore and during conservation management. However, these preliminary considerations can be used to show interesting trends 2s a first basis for general guidelines for ma- nagement and to stimulate the discussion on the possible conservations options. I now attempt to do so.

    THE WOLF CASE

    Referring to the theoretical background given by Soul& & Wilcox (1980), Theber- ge (1983) discusses the need to maintain gene flow among local wolf population as a means of counteracting the possible gap generated by different evolutionary rates of both environmental conditions and wolf genetic adaptations. He underlines the low potential for adaptive change in the wolf due also to philopatry and social structure of the populations and he stres- . ses the detrimental effect of inbreeding on such conditions. Theberge (1983) ac- cepts Soulit & Wilcoxs assumptions on in- breeding effects and he calls for wise ma- nagement of wolf populations by providing gene flows among the isolated demes of different habitat patches. Shields (1983) challenges the conclusions of Theberge by showing the high adaptive value of intra- deme low variability when this means a higher fitness maintained by favourable homozygosis: the total variability of the species is maintained by inter-deme varia- bility and a small flow between demes is enough to generate beneficial variation.

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  • GENETICS OF THE WOLF 37 1

    This model implies the existence of a megapopulation (Shields, 1983) to ensu- re that the fragmented population struc- ture maximizes the species evolutionary potential, as suggested by Wright (1931). A further issue discussed by Shields (1983) is that normally inbreeding species, such as the wolf, are expected to suffer little inbreeding depression:

  • 372 L. BOITAKI

    are now in strong and dangerous conflict with human activities (Boitani & Fabbri, in press). Although general habitat con- ditions would be suitable, wolf presence has a difficult, and often unbearable, im- pact on human activities recently esta- blished in those new areas before the ad- vent of the wolf.

    It does not seem practicable to propose and enforce wolf protection over all these areas that today, excluding human factors, are potentially ecologically suitable. The actual range of 13500 km2 in 1983 np- pears already the maximum affordable, though with minor adjustments in size and distribution, unless the whole socio- economic approach to the use of natupl resources by Italian society be modified.

    I t will be difficult for the wolves even to maintain fully the actual position; in any case, even if they succeed, this will still mean stabilizing at the minimum level necessary for short-term fitness. Any evolutionary potential would be excluded: in fact, by adding an order of magnitude to the actual figure to obtain Ne=500 needed for long-term sutvival, we reach at least N=2000 wolves all over Italy. To hold this population at the present day density, we mould require a suitable area of 120 000 km2, well above one third of Italys overall extension (330 000 km2). And it is difficult to conceive a signifi- cantly higher density for the wolf. Mo- reover, by applying the formula for the expected number of generations to the extinction due to inbreeding depression, we find that extinction would occur in 30 generations at the 1973 level and in 75 at todays population level. Past po- pulation levels (XIX century) as assumed by former distribution areas and patterns were above any dangerous level, mainly because of the connections existing with central European populations. Population numbers in the first half of this centuty may have faced dangerous thresholds, but

    the lack of m y data precludes comparison: in any case, wolf control by man has nf- fected the picture and we are unable to estimate the potential natural evolution of the population.

    DISCUSSION

    Being aware of the speculative value of the above considerations, I nevertheless believe that, disregarding crude numbers, we can discuss the future population trends and the management options open to conservationists concerned with Italian wolves.

    We probably have to accept gratefully hybridization with the dog that has al- lowed the wolf population to reach a re- latively safe level. For future short-term survival there appear to be three schemes:

    1) We accept todays situation and watch the wolfs gene pool slowly being eroded by hybridization eventually to di- sappear.

    2) Assuming that we are able to elimi- nate completely and within a short time feral dogs from the wolf range, we shall return to the condition of a wolf popula- tion at mere survival level, a t the very edge of extinction. Moreover we should be prepared to accept any random shift caused by genetic drift in an ucpiedictable direction: again this should mean the loss - of todays Italian wolf.

    3) We decide to halt drastically the na- tural trend and set up a program of arti- ficial management of the genetic structure of the wolf population. This could he achieved by enclosing wolf packs in (at least 15-20) large enclosures, and work out a programmed reproduction scheme within and among the different enclosure$. By affecting social structures, overlapping generations, progeny variance, etc. we night be able to reduce considerably the gap between N and Ne.

    However this third scheme excludes any conservation of wolves in the wild and

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  • GEAFTICS OF THE WOLF

    it resembles a situation where several zoos prenei\.e the viability of a species for pos- sible arid unpredictable future reintroduc- tions (where?). Alternatively, artificial management could be run in parallel with an effort to implement scheme number 2.

    As conservation is not just a biological technique, but also an ethical approach to natural resources, it is of particular inte- rest to note that todays knowledge of bio- logy proffers only the above three options, all of them pessimistic: I will leave them open for discussion. Pessimism increases on considering that to reach a safety level for long-term survival seems definitely im- possible for the Italian situation: isolation will push our wolves to extinction or to the speciation of a new wolf-dog predator.

    Were the biological background of the- se speculations completely confirmed, the- re would be no escape for pessimism. But, as it is not so, some optimism is permissible.

    For this reason it is urgent to investi- gate the present situation and to start the regular monitoring of the population struc- ture throughout the range. Only by this approach may we hope to find a fourth management option or, a t least, to learn the dynamics of these evolutionary pro- cesses. From a strictly scientific point of view this may well be a unique situation that no-scientist could miss.

    REFERENCES

    Boitani L., 1982 - Wolf and dog competition in Italv. I11 Theriol. Coneressus. Helsinki. Au- gusi 1982. I n press.

    Boitani L. & Fabbri L., 1983 - Strategia di con- servazione del Lupo in Italia. 1st. Naz. Biol. Selvaggina, Bologna, 72: 1-31.

    Boitani L. & Zimen E., in prep. - The Abruzzo Wolf.

    Cagnolaro L., Rosso D., Spagnesi hI. & Venturi B., 1974 - Inchiesta sulla distribuzione del Lupo in Italia e nel Ticino. Lab. Biol. Appl. Caccia-Ric. Biol. Selv., GI.

    Cavalli-Sforza L.L. 8: Bodmer W.F., 1971 - The genetics of Human Populations. W.H. Fre- eman and Co., San Francisco.

    Diamond JAI. 8: May R.hl., 1972 - Island bo- geography and the design of natural reserves. In: Theoretical Ecology: Principles and Ap plications, ed. R.N. h l y. pp. 163-186. Black- well Sc. Publ., Oxford.

    Frankel O.H. & Souli ALE., 1981 - Conservation and Evolution. Cambridge U. P. Cambridge.

    Franklin I.A., 1980 - Evolutionary change in small populations. In: Souls M.E. and \Vilcox B.A. eds., op. cit., pp. 135-150.

    Garten C.T., 1976 - Relationships between ag- gressive behaviour and genic heterozygosity in the oldfield mouse Perotrzysczis polionotus. Evolution, 30: 59-72.

    Kimura hi. & Crow J.F., 1963 - The measure- ment of effective population number. Evo- lution, 17: 279-288.

    Latter B.D.H. & Robertson A., 1962 - The effect of inbreeding and artificial selection on re- productive fitnes:. Genet. Res. Camb., 3: 110-138.

    L$rner I.hl,, 1954 - Genetic homeostasis. Oliver and Boyd, Edinburgh. Dover, New York, ed. 134 PP.

    hIacArthur R.H. & Wilson E.O., 1967 - The theory of island biogeography. Princeron U.P. Princeton.

    Senner J.W., 1980 - Inbreeding depression and the survival of zoo populations. In: Soul6 h1.E. & \Vilcox B.A. eds., op. cit., pp. 209- 224.

    Shields \V.hl., 1983 - Genetic considerations in the management of the wolf and other large vertebrates: an alternative view. In: Wolves in Canada and Alaska. Carbyn L.N. (ed.), Can. \Vildl. Serv. Rep. Series N. 5.

    Souli hl.E., 1980 - Thresholds for survival: maintaining fitness and evolutionary poten- tial. In: Souli h1.E. and \Vilcos B.A. (eds.), op. cit., pp. 151-170.

    Souli M E . & \Vilcox B.A. (eds.), 1980 - Con- servation Biology: An evolutionary-ecological perspective. Sinauer Associates, Sunderland, hlass.

    Theberge J.B., 1983 - Considerations in wolf management related to genetic variability and adaptive change. In: Wolves in Canada and Alaska. Carbyn L.N. (ed.), Can. Wildl. Serv. Rep. Series N. 5.

    Zimen E. & Boitani L., 1975 - Number and distribution of wolves in Italy. Z.f. Sauge- tierkunde Bd. 40: 102-112.

    Wilcos B.A., 1980 - Insular ecology and conser- vation. In: Soul6 hl.E. 8: Wilcox B.A. (eds.), op. cit., pp. 95-118.

    Wright S., 1931 - Evolution in Mendelian popu- lations. Genetics. 1G: 97-159.

    Wright S., 1977 - Evolution and the genetics of populations. Vol. 3, Exp. results and Evol. Deductions. Univ. Chicago Press, Chicago.

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