Can interspecies mating

Working with colleagues at Radboud University in the Netherlands, Heald and her UC Berkeley colleagues looked at the reasons for different viabilities, and discovered that the maternal molecular machinery of the Western clawed frog cannot fully recognize the paternal chromosomes of the African clawed frog. The resultant cells lack a large number of important genes, such as genes for metabolism, and quickly die. When species further separate, crossbreeding no longer leads to viable offspring.

Radboud University press release. Some interspecies sex can be beneficial to the surviving offspring, if they are genetically close enough this depends a bit on how you define "species". These groups of animals can come together and make brand-new creatures. Coyotes and wolves make coywolves, and grizzly bears and polar bears make "grolar bears. Sometimes, the new species have different beneficial genes from both of their parents, and are able to survive better.

Once, a single finch from one Galapagos island flew to another island and started a hybrid population between two finch species. The internet is full of examples of interspecies sex. Sometimes, that behavior is misidentified as cute "riding" behavior. Ever see a frog "riding" a fish? They're actually engaging in " amplexus ," in which the male frog holds onto his partner until she releases eggs, a behavior usually reserved for female frogs.

One difference between the two subspecies is their migration behavior. Both groups of birds breed in North America, then fly south in winter. But russet-backed thrushes migrate down the west coast to land in Mexico and Central America.

Olive-backed thrushes fly over the central and eastern United States to settle in South America. Which directions do hybrids get? To investigate, Delmore trapped hybrid birds in western Canada. She placed tiny backpacks on them. A light sensor in each backpack helped record where the birds went. The birds flew south to their wintering grounds, carrying the backpacks on their journey. The next summer, Delmore re-captured some of those birds back in Canada. The length of the day and timing of midday differs depending on location.

They flew somewhere down the middle. These treks, though, took the birds over rougher terrain, such as deserts and mountains. That could be a problem because those environments might offer less food to survive the long journey. But that strategy might also cause problems. Normally, birds learn cues on their way south to help them navigate back home.

They might notice landmarks such as mountains. But if they return by a different path, those landmarks will be absent. One result: The birds migration might take longer to complete. These new data might explain why the subspecies have remained separate, Delmore says. Following a different path may mean that hybrid birds tend to be weaker when they reach the mating grounds — or have a lower chance of surviving their yearly journeys. If hybrids survived as well as their parents, DNA from the two subspecies would mix more often.

Eventually these subspecies would fuse into one group. Sometimes, hybrids are shaped differently than their parents. And that can affect how well they avoid predators. Anders Nilsson recently stumbled onto this finding. He is a biologist at Lund University in Sweden. In , his team was studying two fish species named common bream and roach not to be confused with the insect.

Both fish live in a lake in Denmark and migrate into streams during winter. To study their behavior, Nilsson and his colleagues implanted tiny electronic tags in the fish. The team used a device that broadcast a radio signal. Tags that received the signal sent back one of their own that the team could detect. But the researchers noticed other fish that looked like something in between.

The main difference was their body shape. Viewed from the side, the bream appears diamond-shaped with a taller middle than its ends. The roach is more streamlined. Roach and bream must have mated to produce those in-between fish, the scientists thought. That would make those fish hybrids. And so the team began tagging those fish, too. Fish-eating birds called great cormorants live in the same area as the fish. Cormorants gobble fish whole. Afterward, they spit out unwanted parts — including electronic tags.

And the hybrids appeared to fare the worst. For their efforts, the team found 9 percent of the bream tags and 14 percent of the roach tags. But perhaps their shape makes them easier targets. Its diamond-like shape makes bream hard to swallow.