Canis rufus is an example of animal whose conservational needs have been questioned because of its possible hybrid status. Control of hybridization has been defended and done in the wild to theoretically save the species. However, control of hybridization may not be the solution. Hybridization may be a phenomenon misconceived by many modern evolutionary biologists, and conservation guidelines over control on anthropogenic impacts may need revisions in order to respect the new perspectives on hybridization’s role in evolution. The term “cladogamy” is being proposed to substitute “hybridization” and to refer to the crossing between two any given clades, due to difficulties from scientists and eventual arbitrary means of separating species from lower taxa. 1. Introduction Animal hybridization is a theme often viewed as harmful to conservation [1] and to ecological/evolutionary processes [2] or at least bizarre/uncommon [3]. Mayr and the biological species concept seem to have given hybridization an unnatural image. Though botanists share a consensus on the importance of plant hybridization for their evolution, zoologists have tended to regard hybridization as an unnatural process [4]. Mayr proposed that “hybridization between species was an unusual “breakdown of isolating mechanisms”, that it was caused mainly by human-induced environmental changes, and had little importance for the understanding of species and speciation, thus adding to the impression that there was no middle ground between species and varieties”, as discussed by Mallet [5]. In fact, Mallet [4] admitted that the influence of Mayr has led to an almost eugenic view on hybridization among zoologists, in contrast with botanists. Hewitt has considered hybrid zones to be important for evolutionary studies [6] and Mallet has defended that they are natural phenomena that require protection disregarding taxonomic status [7]. As to conservation, a notorious evidence of the strength of this almost eugenic view on hybridization is that the US Endangered Species Act of 1973 declares that hybrids are not worthy of conservation, in contrast to pure species [8]. Allendorf et al., 2001 [1], in turn, recognize that hybridization among animals may not be less natural than that in plants; still, they treat the subject as a high danger to biodiversity—especially in, but not restricted to, cases where hybridization is of anthropogenic causes. This work intends to review the effects of hybridization amongst animal populations and infer the importance this particular phenomenon has regarding evolution and
References
[1]
F. W. Allendorf, R. F. Leary, P. Spruell, and J. K. Wenburg, “The problems with hybrids: setting conservation guidelines,” Trends in Ecology & Evolution, vol. 16, no. 11, pp. 613–622, 2001.
[2]
O. Seehausen, G. Takimoto, D. Roy, and J. Jokela, “Speciation reversal and biodiversity dynamics with hybridization in changing environments,” Molecular Ecology, vol. 17, no. 1, pp. 30–44, 2008.
[3]
E. Mayr, Systematics and Origin of Species, Columbia University Press, New York, NY, USA, 1942.
[4]
J. Mallet, “Hybridization as an invasion of the genome,” Trends in Ecology & Evolution, vol. 20, no. 5, pp. 229–237, 2005.
[5]
J. Mallet, “Hybridization, ecological races and the nature of species: empirical evidence for the ease of speciation,” Philosophical Transactions of the Royal Society B, vol. 363, no. 1506, pp. 2971–2986, 2008.
[6]
G. M. Hewitt, “Hybrid zones-natural laboratories for evolutionary studies,” Trends in Ecology & Evolution, vol. 3, no. 7, pp. 158–167, 1988.
[7]
J. Mallet, “A species definition for the modern synthesis,” Trends in Ecology & Evolution, vol. 10, no. 7, pp. 294–299, 1995.
[8]
S. J. O'Brien and E. Mayr, “Bureaucratic mischief: recognizing endangered species and subspecies,” Science, vol. 251, no. 4998, pp. 1187–1188, 1991.
[9]
E. Mayr, This Is Biology: The Science of the Living World, Belknap Press, 1998.
[10]
S. J. Arnold, J. C. Avise, J. Ballou, et al., Genetic Management Considerations for Threatened Species with a Detailed Analysis of the Florida Panther (Felis Concolor Coryi), USFWS, Washington, DC, USA, 1991.
[11]
R. L. Mayden, “A hierarchy of species concepts: the denoument in the saga of the species problem,” in Species: The Units of Diversity, M. F. Claridge, H. A. Dawah, and M. R. Wilson, Eds., pp. 381–423, Chapman and Hall, London, UK, 1997, Florida panther (Felis concolor coryi), Washington, DC, USA, USFWS, 1991.
[12]
C. R. Darwin, On the Origin of Species by Means of Natural Selection, or the Preservation of Favoured Races in the Struggle for Life, John Murray, London, UK, 1859.
[13]
B. M. von Holdt, J. P. Pollinger, D. A. Earl et al., “A genome-wide perspective on the evolutionary history of enigmatic wolf-like canids,” Genome Research, vol. 21, no. 8, pp. 1294–1305, 2011.
[14]
J. R. Adams, B. T. Kelly, and L. P. Waits, “Using faecal DNA sampling and GIS to monitor hybridization between red wolves (Canis rufus) and coyotes (Canis latrans),” Molecular Ecology, vol. 12, no. 8, pp. 2175–2186, 2003.
[15]
R. J. Fredrickson and P. W. Hedrick, “Dynamics of hybridization and introgression in red wolves and coyotes,” Conservation Biology, vol. 20, no. 4, pp. 1272–1283, 2006.
[16]
F. Hailer and J. A. Leonard, “Hybridization among three native North American Canis species in a region of natural sympatry,” PLoS ONE, vol. 3, no. 10, Article ID e3333, 2008.
[17]
J. H. Bohling and L. P. Waits, “Assessing the prevalence of hybridization between sympatric Canis species surrounding the red wolf (Canis rufus) recovery area in North Carolina,” Molecular Ecology, vol. 20, no. 10, pp. 2142–2156, 2011.
[18]
J. Audubon and J. Bachman, The Quadrupeds of North America, vol. 2, New York, NY, USA, 1851.
[19]
L. Y. Rutledge, P. J. Wilson, C. F. C. Klütsch, B. R. Pattersonb, and B. N. White, “Conservation genomics in perspective: a holistic approach to understanding Canis evolution in North America,” Biological Conservation, vol. 155, pp. 186–192, 2012.
[20]
L. Y. Rutledge, C. J. Garroway, K. M. Loveless, and B. R. Patterson, “Genetic differentiation of eastern wolves in Algonquin Park despite bridging gene flow between coyotes and grey wolves,” Heredity, vol. 105, no. 6, pp. 520–521, 2010.
[21]
R. Kays, A. Curtis, and J. J. Kirchman, “Rapid adaptive evolution of northeastern coyotes via hybridization with wolves,” Biology Letters, vol. 6, no. 1, pp. 89–93, 2010.
[22]
C. D. Jiggins and J. Mallet, “Bimodal hybrid zones and speciation,” Trends in Ecology & Evolution, vol. 15, no. 6, pp. 250–255, 2000.
[23]
J. Mallet, “Hybrid speciation,” Nature, vol. 446, no. 7133, pp. 279–283, 2007.
[24]
P. R. Grant and B. R. Grant, “Unpredictable evolution in a 30-year study of Darwin's finches,” Science, vol. 296, no. 5568, pp. 707–711, 2002.
[25]
M. Ridley, Evolution, Blackwell Science, Oxford, UK, 1996.
[26]
M. L. Arnold and S. A. Hodges, “Are natural hybrids fit or unfit relative to their parents?” Trends in Ecology & Evolution, vol. 10, no. 2, pp. 67–71, 1995.
[27]
B. R. Grant and P. R. Grant, “High survival of Darwin's finch hybrids: effects of beak morphology and diets,” Ecology, vol. 77, no. 2, pp. 500–509, 1996.
[28]
M. L. Lancaster, C. J. A. Bradshaw, S. D. Goldsworthy, and P. Sunnucks, “Lower reproductive success in hybrid fur seal males indicates fitness costs to hybridization,” Molecular Ecology, vol. 16, no. 15, pp. 3187–3197, 2007.
[29]
R. M. Nowak, “The original status of wolves in eastern North America,” Southeastern Naturalist, vol. 1, no. 2, pp. 95–130, 2002.
[30]
P. W. Hedrick, R. N. Lee, and D. Garrigan, “Major histocompatibility complex variation in red wolves: evidence for common ancestry with coyotes and balancing selection,” Molecular Ecology, vol. 11, no. 10, pp. 1905–1913, 2002.
[31]
C. J. Edwards, M. A. Suchard, P. Lemey et al., “Ancient hybridization and an irish origin for the modern polar bear matriline,” Current Biology, vol. 21, no. 15, pp. 1251–1258, 2011.
[32]
B. P. Kelly, A. Whiteley, and D. Tallmon, “The Arctic melting pot,” Nature, vol. 468, no. 7326, p. 891, 2010.
[33]
S. Sankararaman, N. Patterson, H. Li, S. P？？bo, and D. Reich, “The date of interbreeding between Neandertals and modern humans,” PLOS Genetics, vol. 8, no. 10, Article ID e1002947, 2012.
[34]
B. Bower, “Fossil may expose humanity's hybrid roots,” Science News, vol. 155, no. 19, p. 295, 1999.
[35]
E. Pennisi, “More genomes from Denisova Cave show mixing of early human groups,” Science, vol. 340, p. 799, 2013.
[36]
N. Saino, R. Lorenzini, G. Fusco, and E. Randi, “Genetic variability in a hybrid zone between carrion and hooded crows (Corvus corone corone and C. c. cornix, Passeriformes, Aves) in North-Western Italy,” Biochemical Systematics and Ecology, vol. 20, no. 7, pp. 605–613, 1992.
[37]
L. E. Harding, O. F. Abu-Eid, N. Hamidan, and A. Al Sha'lan, “Reintroduction of the Arabian oryx Oryx leucoryx in Jordan: war and redemption,” ORYX, vol. 41, no. 4, pp. 478–487, 2007.
[38]
M. E. N. Majerus, Melanism: Evolution in Action, Oxford University Press, New York, NY, USA, 1998.
[39]
D. W. Rudge, “Myths about moths: a study in contrasts,” Endeavour, vol. 30, no. 1, pp. 19–23, 2006.
[40]
H. Jachmann, “Population dynamics of the elephants in the Kasungu National Park, Malawi,” Netherlands Journal of Zoology, vol. 30, pp. 622–634, 1980.
[41]
P. E. Hengeveld and M. Festa-Bianchet, “Harvest regulations and artificial selection on horn size in male bighorn sheep,” Journal of Wildlife Management, vol. 75, no. 1, pp. 189–197, 2011.
[42]
B. M. Fitzpatrick and H. Bradley Shaffer, “Hybrid vigor between native and introduced salamanders raises new challenges for conservation,” Proceedings of the National Academy of Sciences of the United States of America, vol. 104, no. 40, pp. 15793–15798, 2007.
