Paper 9: "Widespread occurrence of a domestic dog mitochondrial DNA haplotype in southeastern US coyotes"

Molecular Surveys

molecular surveys of animal populations have demonstrated that hybridization between species is more common than once believed

Hybridization in Wild Canines

hybridization has been documented in wild canines - examples of endagered species threatened by hybridization and introgression includes, next to other species, the red wolf

Prezygotic Barriers and Hybridization

a prezygotic barrier leads to animals not being able to form a zygote when they mate - suffiencient to prevent hybridization, where sympatric and potentially hybridizing species have populations that are healthy and stable

Behavioral Prezygotic Barrier

different species cannot/won’t mate due to different behaviors such as different mating seasons

Occurrence of Hybridization in Wild Canines

few examples of hybridization of wild canines have occurred when one species is vastly more abundant than the other

Hybridization Between Coyotes and Wolves

coyote is widespread nowadays, but wasn’t always this abundant - offspring of female grey wolf/male coyotes crosses are not integrated into the coyote population, or they do not occur (found no grey wolf mitochondrial DNA)

Mitochondrial DNA

small circular DNA (17,000bp) found in mitochondria and can only be inherited form the mother

Domestication Event and Hybridization

domestic dogs are the oldest domesticated species and were domesticated at least 15,000 years ago - despite the long coexistence of wolves and dogs, there is no evidence for significant introgression of dog DNA into the natural wolf population

Later Studies and Hybridization

later study (2009) found that CBD103(deltaG23) mutation found in dogs, is also found in wolves, reintroduced by hybridization and leads to a melanistic (black) phenotype

Phylogenetic Analysis

sequence analysis of 112 southeastern US coyotes revealed 24 unique haplotypes

la24

one haplotype was highly divergent from all other coyote haplotypes (la24) with 24-30bp differences in 394-400bp, and an average divergence of 8.7% - sequence did not match any canid sequence, more closely related to haplotypes in grey wolves

Phylogenetic Tree

constructed using PAUP and assignment of la24 to wolf/dog clade is supported by a bootstrap value (confidence level) of 98% as well as by three fixed indels, two insertions in the wolf/dog lineage and deletion in the coyote lineage

Hybridization in Captivity

dogs and coyotes are able to hybridize in captivity

Hybridization in Wild (Dog/Coyotes)

previous genetic analyses have found no evidence of dog-introgression in the dog population - contributed to physiological and beahvioral difference

Hybridization in Wild (Wolves/Coyotes)

eastern Canadian wolves and coyotes are able to produce viable offspring, that is incorporated into the wild paternal population

Sample Population

unique because of its recent migration ot the southeastern US - natural migration and artificial transplatns for hunting/sporting purposes

Effects of Hybridization (Females)

F1 and F2 coyote-dog (“coydogs”) hybrid females have shifted estrous cycles, so they are fertile in December rather than in February, meaning that the hybrid litters are born during late winter when it is still very cold

Effects of Hybridization (Males)

male dogs as well as F1 and F2 hybrid mailes raised in captivity showed no parental instincts

Effects of Hybridization (Hybrid Litters)

hybrid litters woul dhave little chance of surviving long enough to be incorporated into the wild population

Hybridization and Fertility

hybrid individals may experience lower levels of fertility because in many cases they have two different sets of chromosomes which leads to difficulties during meiosis and therefore interferes with gamete production

Hybridization and Mitochondrial DNA

backcross of a female hybrid to a male coyote would improve the survivorship of offspring through parental care by father - introduces the maternally inherited dog mitochondrial DNA haplotype into the wild coyote population

Initial Hybridization

intial hybridization event may have been facilitated by mild winters

Wide Distribution of Haplotype

wide distribution of the dog-like haplotype in the southeastern US suggests that the hybridization event happened a long time ago - observed haplotype in relatively new populations of coyotes in the southeasterns US, which were established between 1960 and 1980

Evolutionary History

hybridization event may have occurred in the population of coyotes that is ancestral to southeaster coyotes

Time Line of Evolutionary History

hybridization event occurred as the ancestral coyote population began to colonize the southeastern US - coyotes dispersing along the edge of theri ragne would encounter areas with few potential mates

Allee Effect

hybridization with another species is favored because of density effects - low density of suitable mates

Human Influence on Hybridization

humans released mostly juvenile males, easier to capture, for sport hunting in the area and often making them the first coyotes in many areas, threfore matin with female dogs was preferred because they were lacking their actualy female counterparts

Natural Expansion of Coyotes

once coyotes naturally expanded, the hybrid phenotype was diluted but the mitochondrial DNA lineage remained

Ongoing Hybridization

since, only a single dog haplotype was found, the hybridization even probably involved one or few females and is not evidence for ongoing hybridization

Effects of Dog Mitochondrial DNA

coyotes with dog mitochondrial DNA showed no differences in morpholgy and behavior