Ancestry informative markers in wolves and dogs demonstrate hybridization events

Figure 1 from Godinho et al. (2014) (a) Wolf–dog hybrid from 

Barbanza. Photo courtesy of A. Perez. (b) Location of wolf 

reference samples. Approximate wolf distribution area is 

showen in dark grey (Alvares et al. 2005). The red arrow 
shows the location of Barbanza. (c) Distribution of wolf packs 

(100-km2 circles) in Barbanza (red circle) and the surrounding 

area (black circles) between 1999 and 2003. Dots denote the

location of NIS.

Across the globe, millions of free-ranging dogs coexist with a few tens of thousands of wolves. Wolf-dog hybridization provide a classic example of the ecological and conservation implications of hybridization events between wild and domesticated forms. However the ability to understanding the implications of hybridization has been hampered by high genetic similarity and the difficulties in obtaining tissue samples. Consequently, there are many opportunities for wolves and dogs to hybridize, and cumulative data suggest that hybridization may be more frequent than previously suspected. Previous hybridization studies have required the slow and expensive use of tissue samples collected from dead or trapped animals, thus limiting population-level assessments. Furthermore, difficulties have been reported in correctly identifying wolf–dog backcrosses using simulated individuals and sets of 16–18 microsatellites, typically resulting in a large threshold implemented in clustering analyses.

In a forthcoming article Godinho et al. (2014) assess the occurrence and extension of hybridization in a pack of wolf–dog hybrids in northwestern Iberia, Godinho et al. compare the power of 52 nuclear markers implemented on tissue samples with a subset of 13 ancestry informative markers (AIMs) typed in noninvasive samples (NIS).

Godinho et al. (2014) find the 13 AIMs are as accurate as the 52 markers that were chosen without regard to the power to differentiate between wolves and dogs. The AIMs also having the advantage of being rapidly screened on noninvasive samples. The efficiency of AIMs significantly outperformed ten random sets of similar size and an additional commercial set of 18 markers.

Bayesian clustering analysis implemented on AIMs and NIS identified nine hybrids, two wolves and two dogs. Four hybrids were unambiguously assigned to F¹ x Wolf backcrosses. The new approach (AIMs + NIS) overcomes previous difficulties related to sample availability and informative power of markers, allowing a quick identification of wolf–dog hybrids in the first phases of hybridization episodes. This provides managers with a reliable tool to evaluate hybridization and estimate the success of their actions. This approach may be easily adapted for other pairs of wild/domesticated species, thus improving our understanding of the introgression of domestication genes into natural populations.

The hybridization event at Barbanza started with a cross between a female wolf and a male dog, as inferred by the presence of an Iberian wolf mtDNA haplotype in all hybrids, corresponding to the typical direction of wolf–dog hybridization. Despite the uncertainty of the impact of these crosses in the genetic composition of wolf populations (for example, due to difficulties of hybrid integration in packs), the results do suggest that the Barbanza pack has quickly evolved towards a hybrid swarm, with a minimum of two generations of backcrossing to wolves. These findings are alarming because wolf packs in nonexpanding populations generally consist of related individuals, and thus, other unobserved individuals in the area may also exhibit admixed ancestries.

Identifying wolf–dog hybrids is crucial for conservation and management strategies, particularly in the first phases of an episode of hybridization, as well as to evaluate the success of the strategies that have been implemented. Assuming a minimum territory size of 100 km² centered in the rendezvous site of the Barbanza pack, the area sampled covered a substantial portion of that territory (40%).

Moreover, the authors identified 11 wolf-like canids, 80% of the estimated population, which is fully compatible with the values reported in Iberia for pack size after reproduction, plus some floater animals, suggesting that the AIM’s method allows a comprehensive evaluation of hybridization in a given area. The goal to obtain a quick method to identify hybridization events was successful. Once there is the suspicion of a hybridization event, an estimate of about two months would be required to know the extent of the problem in an area equivalent to a pack territory.

Finally, the authors note that the logistic and economic investment to evaluate hybridization in this area was feasible (ca. 1500€ for the fieldwork – one person working 8 days – plus ca. 5000€ for laboratory work – one person working 3 weeks). Current management guidelines state that every practical measure should be implemented to remove obvious hybrids from the wild once an event of hybridization has been detected. This implies mainly lethal control, although keeping hybrids in captivity and sterilization have also been suggested. Nevertheless, the efficiency of removing hybrids from the wild remains very uncertain. Therefore, the methods shown here constitute a step forward towards the effective management of wolf–dog hybridization. The combination of NIS and AIMs may offer an opportunity to better understand the extension and persistence of hybridization between wolves and dogs at a global scale and its ecological, evolutionary and conservation consequences.

Citation

Godinho, R., López‐Bao, J. V., Castro, D., Llaneza, L., Lopes, S., Silva, P., & Ferrand, N. (2014). Real‐time assessment of hybridization between wolves and dogs: combining noninvasive samples with ancestry informative markers. Molecular Ecology Resources. Early On-line.

Dogs are the dominat prey of Indian Leopards

Photo credit: WCS India

A new study led by the Wildlife Conservation Society reveals that in India's human dominated agricultural landscapes, where leopards prowl at night, it's not livestock that's primarily on the menu -- it is man's best friend.

The study, which looked at scat samples for leopards in India's Ahmednagar's district in Maharashtra, found that 87 percent of their diet was made up of domestic animals. Domestic dog dominated as the most common prey item at 39 percent and domestic cats were second at 15 percent.

Seventeen percent of the leopard's diet consisted of assorted wild animals including rodents, monkeys, and mongoose, and birds.

Livestock, despite being more abundant, made up a relatively small portion of the leopard's diet. Domestic goats, for example, are seven times more common than dogs in this landscape, yet only make up 11 percent of leopard's prey. The author's say this is because goats are less accessible and often brought into pens at night, while dogs are largely allowed to wander freely. Cows, sheep, and pigs were also eaten, but collectively made up less than 20 percent of leopard's food. Most domestic cattle in this region are too large to be preyed on by leopards.

The authors of the study say that the selection of domestic dogs as prey means that the economic impact of predation by leopards on valuable livestock is lower than expected. Thus, human-leopard "conflict" is more likely to be related to people's fears of leopards foraging in the proximity of their houses and the sentimental value of dogs as pets.

Study co-author Ullas Karanth, WCS Director for Science-Asia, said: "During the past two-to-three decades, legal regulation of leopard hunting, increased conservation awareness, and the rising numbers of feral dogs as prey have all led to an increase in leopard numbers outside of nature reserves in agricultural landscapes. While this is good news for conservation and a tribute to the social tolerance of Indian people, it also poses major challenges of managing conflict that occasionally breaks out. Only sound science can help us face this challenge."

Citation

Vidya Athreya, Morten Odden, John D. C. Linnell, Jagdish Krishnaswamy, K. Ullas Karanth. A cat among the dogs: leopard Panthera pardus diet in a human-dominated landscape in western Maharashtra, India. Oryx, 2014; 1 DOI: 10.1017/S0030605314000106