Two Species or Not Two Species? What do you think?

Definition of Species A group of living organisms consisting of similar individuals capable of exchanging genes or interbreeding. The species is the principal natural taxonomic unit, ranking below a genus and denoted by a Latin binomial, e.g., Homo sapiens .

Horses and Donkeys

Lions and Tigers

Wolves and Dogs

Dogs Chihuahua Great Dane

Forest frog and Leopard frog

Horses and Donkeys Mule - infertile

Lions and Tigers Liger - infertile

Wolves and Dogs Wolf-dog: Fertile (most cases). Domesticated dog is a subspecies of Grey Wolf. There are distinct DNA differences. Can be issues with hybrid. So they can reproduce successfully (fertile offspring), but are some issues, so called a subspecies of Grey Wolf, not other wolves species.

Dogs Chihuahua Offspring - Fertile Great Dane

Forest frog and Leopard frog Offspring – Fertile, but….. New species of Leopard Frog discovered in NYC that can’t mate with either…new species, no name yet

Can’t reproduce for many reasons….. Genetically, some animals could reproduce, but they can’t for some specific reasons…..due to “isolation” Why can’t they?

Can’t reproduce for many reasons….. Genetically, some animals could reproduce, but they can’t for some specific reasons…..due to “isolation” Or, they could at one time, became “isolated” and not can no longer reproduce (too many differences and such) Why can’t they?

Can’t reproduce for many reasons….. Populations separated physically by geographic barriers that prevent breeding Populations separated by different times in breeding season that prevent breeding Populations separated by courtship or other differences that prevent breeding Geographic Isolation Temporal Isolation Behavioral Isolation