On the Morphological Distinctness of the Hybrid between the Sable ...

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The pine marten (Martes martes L., 1758) and, especially, the sable (Martes zibellina L., 1758) are valuable fur bearing species. The marten mainly inhabits ...
ISSN 00124966, Doklady Biological Sciences, 2013, Vol. 448, pp. 52–56. © Pleiades Publishing, Ltd., 2013. Original Russian Text © V.G. Monakhov, O.D. Uspenskaya, 2013, published in Doklady Akademii Nauk, 2013, Vol. 448, No. 6, pp. 732–736.

GENERAL BIOLOGY

On the Morphological Distinctness of the Hybrid between the Sable and Pine Marten V. G. Monakhov and O. D. Uspenskaya Presented by Academician V.N. Bol’shakov November 14, 2011 Received March 11, 2012

DOI: 10.1134/S0012496613010171

The pine marten (Martes martes L., 1758) and, especially, the sable (Martes zibellina L., 1758) are valuable furbearing species. The marten mainly inhabits northwestern Eurasia, whereas the sable range is in the northeast of the continent. However, the ranges of these species overlap in the Ural and Trans Ural regions. The pine marten, either due to its higher ecological flexibility or as a result of hybridization, can replace the sable and occupy the former sable stations [1, 2]. Here, in the zone of transgression, crossing (so called kidussization) occurs between species; their hybrid is called kidus. The phenomenon of interspe cific hybridization of these two valuable furbearing species has not only biological, but also economic importance, because there is a risk of local decrease in the resources of the sable, a more valuable furbearing species. The identification of hybrids between morphologi cally similar species is inevitably connected with methodical difficulties. Not only morphological, but also genetic similarity between the sable and pine mar ten has been retained. However, neither crossing between kiduses accumulation crossing of male sables with female kiduses has yielded offspring thus far [3–5]. Male kiduses are considered reproductively sterile [2], because offspring was obtained only from the female kiduses and male martens; this fact leaves the possibil ity of introgressive hybridization. In the present study, we attempted to reveal cranio logical characteristics of the sable and pine marten hybrids with the help of comparative formalization by the method of geometric morphometry [6–8]. Com parisons have been done on the basis of one cranial construction, namely the bulla ossea region. It is used by a number of authors [9–11] as a diagnostic charac ter of Martes.

Craniological collections of sables, martens, and kiduses (Table 1) from the Zoological Museum of the Moscow State University (collections of the Pechoro Ilychskii State Reserve, the transgression zone), mar tens from the Zoological Museum of the Institute of Plant and Animal Evolution of the Ural Branch of the Russian Academy of Sciences (Talitsa and Sukhoi Log municipalities of Sverdlovsk oblast in the Middle Urals) and sables from the personal collection of A.V. Krutikov (the upper Taz River basin) were stud ied. The animals were identified as hybrids by collec tors (or suppliers) of the material and accepted according to the museum descriptions. Only adult individuals (older than one year) were included in the analysis. The age was determined according to meth ods of Smirnov [12] and Timofeev and Nadeev [13]. Digitized images of the cranium ventral side (with a resolution of 4320 × 2432 pixels, Fig. 1) were pro cessed with the use of the TPS, MorphoJ 1.01c, and IMP software [14]. All the statistical calculations were done with the help of MS Excel 2003, Past 2.07, and Statistica 6.0 software. The cluster analysis was done on the basis of matrix of generalized Mahalanobis dis tances (D2). Twentyseven landmarks were used for characteristics of the shape of bullae osseae and their position relative to the cranium (Fig. 1). Statistically significant differences (p < 0.0001) between sexes were revealed for kiduses as well as pine martens and sables; therefore, the analysis of the shape of bullae osseae took the sex into consideration. All the samples of male and female Martes studied differed statistically significantly (p < 0.0056). The results of canonical discriminant analysis for the samples of the kidus with pine marten and sable samples are presented in Fig. 2. With respect to the first canonical variable accounting for 52.1–63.6% of the intergroup variance, interspecific differences have been found. Male and female kiduses occupy an inter mediate position between sables and pine martens of the PechoroIlychskii National Park. This agrees with

Institute of Plant and Animal Ecology, Ural Branch, Russian Academy of Sciences, ul. Vos’mogo Marta 202, Yekaterinburg, 620144 Russia 52

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Table 1. The craniological material studied Number of males

Number of females

Martes martes

30

25

Martes zibellina M. martes × M. zibellina (kidus) Martes martes

26 20 16

20 12 17

30 122

21 95

Working name of the sample

Location PechoroIlychskii State Reserve

Pechora

Talitsa and Sukhoi Log Middle Urals municipalities of Sverdlovsk oblast Upper Taz River Taz Total Total

Species

Martes zibellina

217

Table 2. Results of classification of sables, pine martens, and kiduses on the basis of discriminant analysis of the shapes of bullae osseae Number of identified individuals Location (n)

Correct iden tification, %

Pechora, kidus (32) Pechora, pine marten (55) Pechora, sable (45) Middle Urals, pine marten (33) Upper Taz River, sable (51) Total

62.5 70.9 71.1 72.7 84.3 73.15

Pechora, kidus

Pechora, pine marten

Pechora, sable

Middle Urals, pine marten

Upper Taz River, sable

20 4 5 2 0 31

4 39 2 7 0 52

5 3 32 0 8 48

2 9 1 24 0 36

1 0 5 0 43 49

data on the firstgeneration hybrids, which inherit characters of both parental forms and, hence, exhibit a “mixture” of marten and sable morphological char acters. Regarding the shape and position of bullae osseae, kiduses display the greatest differences from sables from the upper Taz River. The results of estimation of correct classifications for the kidus, pine marten, and sable are given in Table 2.

Estimation of the correctness of the classification based on the shape and position of bullae osseae has shown that comparison of the kidus, pine marten, and sable yields, on average, 73.15% correct identifica tions for both samples. The highest percentage of cor rect classifications (84.3% of animals correctly identi fied and classified with their own group) has been obtained for sables from the upper Taz River. The

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21 20

Fig. 1. The diagram of the arrangement of landmarks on the cranium of Martes. DOKLADY BIOLOGICAL SCIENCES

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(a)

Canonical variable 2 (СVA 2), 20.95%

4 5 2

3

0

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−2

−4

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−6 −4 −2 0 2 Canonical variable 1 (СVA 1), 52.06%

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Canonical variable 2 (СVA 2), 23.12%

6 (b)

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0 3 6 Canonical variable 1 (СVA 1), 63.63%

Fig. 2. The positions of (a) male and (b) female (1) kiduses, (2, 4) sables, and (3, 5) pine martens in the space of two first canonical variables: (2, 3) Pechora; (4) Taz; (5) Middle Urals.

lower percentage of correct classifications (62.5%) has been obtained for kiduses from Pechora, three quar ters of incorrectly identified animals were Pechorza sables and martens (the “parents” of the hybrids). Classification of the samples of Martes based on the results of cluster analysis by the method of unweighted pair group method of average means (UPGMA) on the basis of the matrix of generalized Mahalanobis dis

tances (D2) is shown in Fig. 3. The dendrogram dem onstrates that the samples studied can be divided into two distinct, large clusters: sables and pine martens. Females and males from each geographical point fall into a single cluster, which indicates the priority of geographical differences in the character studied. Female and male kiduses form a separate cluster, which is close to pine martens. DOKLADY BIOLOGICAL SCIENCES

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Kidus F Kidus M Marten PI F Marten PI M Marten Talitsa F Marten Talitsa M Sable of the Taz River M Sable of the Taz River F Sable PI F Sable PI M 0

0.2

0.4

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1.2 1.4 Connection distance

Fig. 3. Results of the cluster analysis of compared samples of the sable, pine marten, and kidus on the basis of generalized Mahal anobis distances (D2) by the UPGMA method (F, females; M, males; PI, PechoroIlychskii State Reserve).

On the basis of analysis of samples of male and female sables and pine martens, statistically significant differences of bullae osseae shapes have been revealed. The sable shows a tendency towards a more prolonged and rounded shape of bullae osseae, so that their area is visually larger in twodimensional representation. Martens have narrower, angular bullae osseae; as a result, their area is less in twodimensional representa tion. An earlier study [15] on craniometrical characters of sympatric (PechoroIlychskii) Martes and their hybrids showed that kiduses had intermediate param eters without displaying significant differences from the original species from the zone of transgression. In our case, statistically significant differences in the shape of the bulla ossea construction of martens, sables, and kiduses have been obtained, with kiduses occupying an intermediate but distinctly separate position among the compared samples (Fig. 2). It may be assumed that, in the Martes studied, the shape and mutual positions of bullae osseae correlate with the characteristics of their way of life. The pine marten is more adapted to wood life conditions than the sable and actively uses this additional ecological niche. Therefore, in the course of evolution, the char acters of martens connected with the development of the vestibular apparatus have been fixed. The sable, with their way of life the hearing is more developed in comparison with the marten. It might be supposed that in ecology these differences are reflected in the structure and, as a result, the shape and position of the bulla ossea construction. DOKLADY BIOLOGICAL SCIENCES

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By using the geometric morphometric method in the study of the shape and position of bullae osseae, it has been determined that the sable, pine marten, and kidus exhibit statistically significant interspecific, sex related, and geographical differences. Kiduses occupy an intermediate position between the parental forms and correspond to the classical notion about the status of interspecific F1 hybrids. A combination of sable and pine marten morphological characters is characteristic of these hybrids. The method used (discriminant anal ysis) allows classifying individuals of the Martes spe cies studied with an accuracy of 62–85% and may have the practical importance for identification of the orig inal forms and their hybrids. The study of hybrids and analysis of its data makes it possible to determine the speciesspecific ranges of morphological parameters in more detail, and the study of the phenomenon of hybridization is promis ing for the development of general biology. ACKNOWLEDGMENTS This study was supported by the Presidium of RAS (project no. 12P452002). REFERENCES 1. Yurgenson, P.B., Tr. PechoroIlychsk. Gos. Zapoved nika, 1947, vol. 5, pp. 145–180. 2. Grakov, N.N., Lesnaya kunitsa (Pine Marten), Mos cow: Nauka, 1981. 3. Portnova, N.T., Krolikovod. Zverovod., 1941, no. 6, pp. 22–23.

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4. Grakov, N.N., Sb. Nauch.Tekh. Inform. VNIIOZ, 1970, no. 30, pp. 48–53. 5. Grakov, N.N., Sb. Nauch.Tekh. Inform. VNIIOZ, 1971, no. 34, pp. 20–25. 6. Bookstein, F.L., Morphometric Tools for Landmark Data, Cambridge: Cambridge Univ. Press, 1991. 7. Pavlinov, I.Ya., Voltsit, O.D., and Rossolimo, O.L., Zh. Obshch. Biol., 1994, vol. 55, no. 1, pp. 110–120. 8. Rohlf, F.J., Syst. Biol., 1998, vol. 47, no. 1, pp. 147– 158. 9. Novikov, G.A., Khishchnye mlekopitayushchie fauny SSSR (Predatory Mammals of the Fauna of the Soviet Union), Moscow: Akad. Nauk SSSR, 1956. 10. Stroganov, S.U., Zveri Sibiri: khishchnye (Mammals of Siberia: Carnivores), Moscow, 1962.

11. Geptner, V.G., Naumov, N.P., Yurgenson, P.B., et al., Mlekopitayushchie Sovetskogo Soyuza (Mammals of the Soviet Union), Moscow: Vysshaya Shkola, 1967, vol. 2, part 1. 12. Smirnov, V.S., Tr. Inst. Biol. UF AN SSSR, 1960, vol. 14, pp. 97–112. 13. Timofeev, V.V. and Nadeev, V.N., Sobol’ (The Sable), Moscow: Zagotizdat, 1955. 14. Zelditch, M.L., Swiderski, D.L., Sheets, H.D., et al., Geometric Morphometrics for Biologist: A Primer, New York: Elsevier, 2004. 15. Pishchulina, S.L., Meshcherskii, I.G., and Rozhnov, V.V., Zhivotnyi mir gornykh territorii (The Fauna of Moun tainous Areas), Moscow: KMK, 2009.

DOKLADY BIOLOGICAL SCIENCES

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2013