Our example tells us that the map below shows the ranges of the common chimpanzee or Pan troglodytes in orange, and the bonobo or Pan paniscus in purple. Now also shown on the map is the Congo River. Right? So let's just check out this map real quick. We see in orange, right, that's the range of the common chimpanzee there.
Kind of tucked up right next to it there, we see the range of the bonobo there in purple, and the Congo River is running right between the two. Alright. It says that both species live in similar habitats within the tropical rainforest environment. The two species are thought to have split from a common ancestor approximately 1.5 to 2 million years ago. We want to use this information, information from the map, to answer the following questions.
Alright. So a) here says, are these two species sympatric or allopatric species? What do you think? Well, I'm going with allopatric. Remember, allopatric, we broke that word down.
Allo means other or different. Patrick refers to the country or region. So these species just live in different areas. They are separated by that river. They don't have overlapping ranges.
b) says, what specific type of reproductive isolation do you think likely led to and is most responsible for maintaining the two species? Alright. So what type of reproductive isolation do we see with allopatric speciation? Well, we call that habitual isolation.
Remember, they reproduce in different habitats. Right? And well, that makes sense because chimpanzees and bonobos, they can't swim. Right? So they can't get across this river.
There is a barrier that is separating them, so they are reproductively isolated. Alright. Our question c) though says if a vicariance event led to the formation of these two species, make a prediction about the age of the Congo River and how bonobos and common chimpanzees ended up on opposite sides of the river. Alright. Think what does vicariance mean and what would that imply about the age of this river?
Well, vicariance means that the population was sort of living where you find it now, but it was physically split by something. And in this case, I would assume that would be the formation of the river. So this, if this was a vicariance event, well these populations split, it says 1.5 to 2 million years ago, I'd expect the river to be 1.5 to 2 million years old. That's my age of the Congo River.
Alright. Well, how did they end up on opposite sides of the river? Well, I'm just going to say that the river, the formation of the river, split the population. Right? It was one population.
The river formed. It ran sort of right through the middle of it. They can't swim. Now they're reproductively isolated. Now that's classic vicariance right there.
Alright. Well, d) then says, if a dispersal event led to the formation of these two species, make a prediction about the age of the Congo River and how bonobos and common chimpanzees ended up on opposite sides of the river. Alright. So what would your prediction be if this was a dispersal event? Well, if it was dispersal, I'm going to assume that the river is older than 1.5 to 2,000,000 years.
So I'm just going to put greater than 2 million years old. Well, how did they end up on opposite sides of the river? Well, I don't know where they started. I don't know which is sort of the original population, and I don't actually know how they got across, but I'm just going to say that some individuals crossed. Individuals crossed the river.
Alright. Who knows how they got across because they can't swim, but somehow they did. Alright. What's the real answer? Well, we don't know for sure.
Scientists think this was probably a vicariance event and the age of the river is about 1.5 to 2 million years old, though other scientists do disagree with that interpretation. Alright? Alright. So with this, we got more practice to come. I'll see you there.