Why are Guppies so Diverse?

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Let's Talk Science
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Different members of a species can have different traits. You can see this in a species found at your local pet store - guppies!

Guppies (Poecilia reticulata) are a type of fish that you can see in just about every pet store. If you went swimming in a freshwater stream near the Equator, you may see guppies there too. You can even see guppies living in the sewers of Rio de Janeiro, Brazil! Guppies are popular as pets because they come in many different colours and patterns. 

Did you know? 

Guppies are also known as millionfish and rainbow fish.

But even though all of these guppies are the same species of fish, they may look and behave very differently. This diversity makes them very interesting for scientists to study. Ecologists call the way an organism looks and behaves its traits

For example, look at all of the different shapes of guppy fins and tails.

Guppy tails and fins come in different shapes and sizes
Guppy tails and fins come in different shapes and sizes. (Source: Stacky7 [CC BY-SA 4.0] via Wikimedia Commons).

 Some guppies have round tails. Some guppies have tails shaped like fans or flags. Some guppies even have tails shaped like swords!

Guppies also come in many colours. For example, their bodies might be silver or blue. Their tails might be yellow, pink, orange or several different colours!

Let’s look at why guppies can have very different traits.

Do male and female guppies look the same? 

In many types of animals, males and females of a species do not look the same. Males can often be more showy than females. This is so that they can attract mates. Females tend to be drab. This is so that they can hide better. They hide to keep themselves and their young safe. 

Male and female guppies do not look the same. Male guppies are more colourful than female guppies. Can you tell the difference between male guppies and female guppies in the pictures below? 

Guppies come in many different colours
Guppies come in many different colours (Source: sommail via iStockphoto).

(Answer: On the left, the male is above and the two females are below. On the right, there are three males on the left and one female on the right).

Female guppies prefer to mate with the showiest male guppies they can find. But many guppies get eaten by predators.  If a showy male can survive, then it is probably a good choice for a mate.

Wild and domestic guppies
Wild guppies on the left and pet store guppies on the right (Sources: Per Harald Olsen [CC BY 3.0] via Wikimedia Commons [Left] and isoft via iStockphotos [Right]).

How do guppy traits help them adapt to their environment?

Guppies live in a lot of different environments. In each environment, they need specific traits to survive. Scientists call the development of these specific traits a local adaptation. A species will adapt to its environment in a way that will let it survive there.

For example, some guppies live in the same streams as the animals that eat them. These animals are called their predators. Other guppies do not live in the same streams as their predators. Ecologists have found that these two types of guppies have different traits.

One type of guppy predator is a fish called the cichlid.

Pike Cichlid (Cichlidae Crenicichla)
Pike Cichlid (Cichlidae Crenicichla) (Source: Clinton & Charles Robertson from RAF Lakenheath, UK & San Marcos, USA [CC BY 2.0] via Wikimedia Commons).

Did you know? 

Some cichlids are very good predators. They have long, thin bodies that let them swim quickly. They also have strong jaws that let them catch a lot of prey. 

The guppies that live in the same streams as cichlids tend to have drab colours. This helps them camouflage. These fish have a better chance of not being eaten by cichlids. 

Let’s look at those guppy photos one more time.

The pictures on the left are wild guppies. The pictures on the right are pet store guppies. Do you notice how wild guppies are not very colourful?

Do guppies in different places have different reproductive strategies?

Guppy young are called fry. The guppies that live in the same streams as cichlids start to reproduce at a very young age. They have lots of fry. This way, there is a greater chance that at least some of those fry will survive to adulthood.  
The guppies that live in streams without cichlids tend to be much brighter. Since they do not have to worry about being seen by cichlids, they can be very bright and flashy. (Remember, females prefer flashy males!) The females do not have to rush to mate. They also have fewer, larger fry. These fry have a good chance of surviving. 

Do the same things happen with pet guppies?

Yes! Guppies raised to be pets live in tanks without predators. Females are free to choose the males they like best. As you now know, these are the most colourful ones. People who want to breed guppies will often look for males and females of interesting colours and shapes. When they mate, guppies of new and interesting colours and shapes are born!

So the next time you are in a pet store, check out the guppies. Think about why they look the way they do. Try to spot the males and the females. And maybe you’ll even bring one home!
 

Starting Points

Connecting and Relating

  • Have you ever had guppies or other fish as pets? Why or why not?
  • Have you looked at fish in pet store aquariums? What features of fish do you tend to notice? 

Connecting and Relating

  • Have you ever had guppies or other fish as pets? Why or why not?
  • Have you looked at fish in pet store aquariums? What features of fish do you tend to notice? 

Relating Science and Technology to Society and the Environment

  • Do you think that pet store guppies could survive in the wild? Explain.
  • Should people catch wild fish and keep them as pets? Explain.

Relating Science and Technology to Society and the Environment

  • Do you think that pet store guppies could survive in the wild? Explain.
  • Should people catch wild fish and keep them as pets? Explain.

Exploring Concepts

  • What adaptations did the guppies living with the cichlids have that helped them and their young to survive?
  • What is a local adaptation? What other local adaptations do you know of?
  • How can local adaptations lead to more biodiversity?
  • Why do pet store guppies look so different from the wild guppies?
  • Watch the video, Tips for Keeping Guppies. What are the good things about having guppies as a pet? 

Exploring Concepts

  • What adaptations did the guppies living with the cichlids have that helped them and their young to survive?
  • What is a local adaptation? What other local adaptations do you know of?
  • How can local adaptations lead to more biodiversity?
  • Why do pet store guppies look so different from the wild guppies?
  • Watch the video, Tips for Keeping Guppies. What are the good things about having guppies as a pet? 

Nature of Science/Nature of Technology

  • How important is it for scientists to spend time investigating predator-prey relationships like the one in this article? Explain.

Nature of Science/Nature of Technology

  • How important is it for scientists to spend time investigating predator-prey relationships like the one in this article? Explain.

Teaching Suggestions

  • This article, and the connecting resources, can be used to introduce the concept of adaptations in animals, specifically fish. This article can also be useful to help students deepen their understanding of the connections between adaptations and predator-prey relationships within ecosystems. Concepts introduced include species, traits, ecologist, diversity, camouflage, local adaptation and predator. 
  • After reading the article teachers could have students complete a Concept Definition Web learning strategy (individually or as partners) to help them develop a deeper understanding of the concept of adaptation. Download ready-to-use reproducibles using the Concept Definition Web learning strategy for this article in [Google doc] and  [PDF] formats.
  • To explore the concept of camouflage and local adaptation, teachers could have students design a guppy of their choice based on the guppy shapes image in the article and colours of their choice. Students should decide which type of environment their guppy will live in and justify their choice of shape and colour based on the environment.
  • Students could raise and breed guppies as a class project. There are many good resources online which explain how.

Teaching Suggestions

  • This article, and the connecting resources, can be used to introduce the concept of adaptations in animals, specifically fish. This article can also be useful to help students deepen their understanding of the connections between adaptations and predator-prey relationships within ecosystems. Concepts introduced include species, traits, ecologist, diversity, camouflage, local adaptation and predator. 
  • After reading the article teachers could have students complete a Concept Definition Web learning strategy (individually or as partners) to help them develop a deeper understanding of the concept of adaptation. Download ready-to-use reproducibles using the Concept Definition Web learning strategy for this article in [Google doc] and  [PDF] formats.
  • To explore the concept of camouflage and local adaptation, teachers could have students design a guppy of their choice based on the guppy shapes image in the article and colours of their choice. Students should decide which type of environment their guppy will live in and justify their choice of shape and colour based on the environment.
  • Students could raise and breed guppies as a class project. There are many good resources online which explain how.

Learn more

Community Ecology: Feel the Love (2012)

Video (11:29 min.) from Crash Course  about how the interaction between species can define ecological communities.

Variation in a species (2009)

Video (19:51 min.) from Khan Academy on how variation can be introduced into a species.

Ecology - Rules for living on Earth (2012)

Video (10:25 min.) from Crash Course discusses ecology, and how it seeks to explain why the world looks and acts the way it does.

References

Arbour, J. H., & López-Fernández, H. (2013). Ecological variation in South American geophagine cichlids arose during an early burst of adaptive morphological and functional evolution. Proceedings of the Royal Society B: Biological Sciences, 280(1763). DOI: 10.1098/rspb.2013.0849

Bassar, R. D., Marshall, M. C., López-Sepulcre, A., Zandonà, E., Auer, S. K., Travis, J., … Reznick, D. N. (2010). Local adaptation in Trinidadian guppies alters ecosystem processes. Proceedings of the National Academy of Sciences, 107(8), 3616–3621. DOI: 10.1073/pnas.0908023107

Des Roches, S., Post, D. M., Turley, N. E., Bailey, J. K., Hendry, A. P., Kinnison, M. T., … Palkovacs, E. P. (2017). The ecological importance of intraspecific variation. Nature Ecology & Evolution, 2(1), 57–64. DOI: 10.1038/s41559-017-0402-5

Reznick, D., Bryga, H., & Endler, J. (1990). Experimentally induced life-history evolution in a natural population. Nature, 346(6282), 357-359. DOI: 10.1038/346357a0

Travis, J., Reznick, D., Bassar, R. D., López-Sepulcre, A., Ferriere, R., & Coulson, T. (2014). Do eco-evo feedbacks help us understand nature? Answers from studies of the Trinidadian guppy. Advances in Ecological Research, 50, 1–40. DOI: 10.1016/b978-0-12-801374-8.00001-3