NEW YORK (GenomeWeb) – Africa's golden jackals appear to belong to a genetically distinct species compared with golden jackals in Europe, an international team has found.
As they reported online today in Current Biology, researchers from the US, Russia, and elsewhere analyzed genomic, mitochondrial, and microsatellite sequence data for golden jackals from Africa and Eurasia. By comparing these sequences to one another and to those of gray wolves, they determined that Africa's golden jackal belongs to a new species — dubbed the African golden wolf owing to its closer relationship to gray wolves and dogs.
"Not only were jackals in Africa and Eurasia different, but … they're not even each others' closest relatives and, therefore, must represent different species," co-first author Klaus-Peter Koepfli, a researcher affiliated with the Smithsonian Conservation Biology Institute and St. Petersburg State University, told GenomeWeb.
Golden jackals in Africa and Europe were originally considered one species based on similarities in their coloring, skull and tooth shape, and other physical features.
Mitochondrial DNA studies published in PLOS One in 2011 and 2012 called that classification into question, hinting that golden jackals in at least some parts of Africa might fall into a gray wolf sub-species.
But it was still unclear whether golden jackal and jackal-like wolf relatives co-occurred in Africa, Koepfli explained, since the mitochondrial DNA studies didn't include golden jackals from East African sites such as Kenya and Tanzania.
"We wanted to see whether those were still golden jackals — which would make them sort of a relic or isolated population from other golden jackal populations in Eurasia," he said.
For their own analyses, Koepfli and colleagues started by putting together phylogenetic trees for the canines based on several different genetic markers.
In a tree stemming from cytochrome b sequences for more than 100 African golden jackals, Eurasian golden jackals, and gray wolves, for example, golden jackals from Africa fell into a lineage that split from gray wolves only after an earlier divergence from the ancestors of Eurasian golden jackals.
The team saw similar canine relationships using other mitochondrial or nuclear DNA marker genes as well, with golden jackals from Africa consistently appearing in a clade that neighbored gray wolves.
While phylogenetic details varied depending on whether nuclear or mitochondrial markers were used, the overall pattern was clear for the golden jackals," Koepfli explained.
"Our mitochondrial DNA and nuclear DNA phylogenies are quite different," he said, "but they're consistent in showing that these two golden jackal lineages are definitely not each others' closest relatives."
Instead, the data pointed to a Eurasian-African golden jackal split stretching back more than a million years, followed by a subsequent split between the African golden jackal and the wolf-dog-coyote lineages.
The researchers garnered additional canine relationships clues using sex chromosome sequences from the gray wolf, coyote, and golden jackals, along with nearly 7.7 million SNPs identified by comparing whole-genome sequences for three Eurasian wolves, an Israeli golden jackal, and a newly-sequenced Kenyan golden jackal.
Within the African golden jackal — "African golden wolf" — species, for example, the team found that Kenyan animals formed a genetic cluster that was somewhat separated from animals sampled in Algeria, Morocco, Mauritania, and Senegal.
On the other hand, microsatellite data for 128 golden jackals, gray wolves, and dogs pointed to potential mixing between Eurasian golden jackals and African golden wolves in the Middle East and North Africa.
Koepfli noted that additional research is needed to assess genetic variability within each species and its relationship to the animals' physical traits and lifestyles. With that in mind, the researchers are now working on more detailed population studies using museum samples going back to the late 1800s as well as modern samples.
Where the current study mainly focused on Eurasian golden jackals from the Middle East and Eastern Europe, for example, follow-up research will include samples from golden jackals in Thailand.
The team is also assessing hundreds of samples from within Israel to look at the extent of hybridization, if any, between golden jackals and African golden wolves, Koepfli noted. "We know that in a lot of places where species from the genus Canis overlap there is hybridization."