A simple Conclusion

A deeper understanding of evolution

We know that evolution is the change of heritable traits over successive generations as stated last post, however, an individual organism’s phenotype results from both its genotype as well as the influence from the environment it has lived in. You see there are a range of factors that influence an organism’s evolution as will be explored in today’s post.

Variation results from mutations in the genome, the reshuffling of genes from sexual reproduction and gene flow through the migration between populations. The relatively small differences in genotype can lead to dramatic differences in phenotype. Wetterbom et al (2006) state that the genome difference between chimpanzees and humans only differ by 5% in terms of genomes.

Evolution occurs through a range of mechanisms as well as influences explored above. These mechanisms that can lead to changes in allele frequencies include natural selection, genetic drift, genetic hitchhiking, mutation and gene flow. Natural selection was touched on last post, it is the evolution by which traits that enhance survival and reproduction become more common in successive generations by population. Genetic drift is the change in allele frequency from one generation to the next due to sampling error. And lastly Gene flow involves the exchange of genes between populations and between species, as seen above, it can lead to variation.

Variation can allow visual, among others, differences in a species which may give the organism a higher survival chance. An example below shows that variations among finches due to natural selection. This variation occurred due to the resources available in the environment of the species. The change in beak morphology allowed them to access specific resources.

Figure 1: Natural selection resulting in different beak morphology. Image: NHGRI (2014).

To put it simply; evolution is the change in heritable traits of biological populations over successful generations. It is the processes that give rise to diversity at every level of biological organisation. The process by which different kinds of organisms are believed to have developed from earlier forms during the history of earth. The science behind evolution is so vast and deep in understanding. I have done it now justice but hope that I have done enough to get you, the reader, interested in the fascinating world of mimicry, deception and evolution. 

References

National Human Genome Research Institute. (2014). Natural selection resulting in different beak morphology. http://www.genome.gov/glossary/. retrieved: 30/05/2015.

WETTERBOM, A., SEVOV, M., CAVELIER, L., & BERGSTRÖM, T. (2006). Comparative Genomic Analysis of Human and Chimpanzee Indicates a Key Role for Indels in Primate Evolution. Journal of Molecular Evolution. 63, 682-690.

The Basics of Evolution

Today’s post will make an attempt to explain the very basics of evolution, how these animals with remarkable mimicry and deception techniques came to be. Basically, there are three essential parts to evolution. It is possible for the DNA of an organism to occasionally mutate. The change due to mutation is either beneficial, harmful or neutral and lastly the mutations occur and spread over long periods of time resulting in new species.

DNA is the hereditary material of life, it affects how an animal looks, behaves as well as its physiology. Page & Holmes (1998) state that DNA sequences are valuable pieces of information, that they provide the most detailed anatomy possible for any organism. Therefore, it can easily be seen that a change in its DNA can change other aspects of its life. Mutations can either be neutral, beneficial or harmful. These mutations can give it an advantage other others, make it harder for them to survive or have no effect on their lives at all. However, mutations are completely random, whether the mutation is beneficial or not as well as how useful it is to the animal is unrelated and random. If the mutation is beneficial to the animals, then it has a higher chance to reproduce and hence pass on the beneficial genes. This process is repeated over a long period of time until the species all have gained the beneficial mutation as those with it were more successful than those without.

For example, the Common Mormon (Papilio polytes) may not have looked like the Common Rose (Pachliopta aristolochiae) originally. However, a mutation may have given one individual a red spot on its wing. This single red spot confused predators and deterred them from consuming the mutated individual. This gave it an increased chance to breed and pass on the mutation that gave it a red spot. This process was repeated and over time the species developed multiple red spots that mimicked the distasteful poisonous Common Rose. This is an example of visual evolution but can occur in all aspects of an animal such as behaviour and body movement as well in earlier posts.

Figure 1: Comparative photo of Papilio polytes(top) and Pachlio aristolochiae(bottom). Photographer: Kunte (2014)

Hopefully this snippet gave you some idea of how evolution works, more examples as well as a deeper understanding will be attempted in the next post.

References:

Kunte, K. (2014) Comparative photo of Papilio polytes(top) and Pachlio aristolochiae(bottom). http://www.natureasia.com/en/nindia/article/10.1038/nindia.2014.29. Retrieved: 24/05/2015

PAGE, R. D. M., & HOLMES, E. C. (1998). Molecular evolution a phylogenetic approach. Oxford, Blackwell Science. http://search.ebscohost.com/login.aspx?direct=true&scope=site&db=nlebk&db=nlabk&AN=51693.

Monocirrhus polyacanthus

Monocirrhus polyacanthus

Also known as the South American Leaf Fish, Monocirrhus polyacanthus is another great example of mimicry, deception and evolution. It has evolved to utilise false markings and behavior in an unusual but brilliant form of aggressive mimicry. In terms of its morphological features; it can have a range of colourations; ranging from orange-yellow to brown with various markings that give this species the appearance of a dead leaf. This colouration is dependent of its surroundings. It has transparent pectoral fins that allow this species to stay afloat without breaking the illusion. The pectoral and caudal fins developed early in the species life. Walker (2004) states that this is due to standard maneuvering and “start movements” commonly associated to predation strikes. Its behavior is simply to drift around and slowly approach unsuspecting prey. This false behavior masks its predatory nature as well as strengthening the illusion of a dead leaf. However, once they come into range of the prey, they utilise predation strikes in order to catch their prey. This species possesses an extendable and large mouth that creates a vacuum that sucks the prey in. Because of its hunting nature, prey may be consumed between large periods of time. Its mouth morphology allows it to consume prey that are proportionally large. Catarino & Zuanon (2010) state that the combination of its morphology and visually effective false markings allow this species to consume the large as well as the fast moving prey.

Figure 1: Monocirrhus polyacanthus camouflaged within dead leaves. Photographer: Mühlacker (2015).

As seen in the previous posts; mimicry and deception in animals is a useful technique that can utilized defensively, aggressively or a combination of both. It ranges from looking like another species, sounding like another species and behaving in deceptive manners just to name a few. However, these species have evolved to be like this, they may not have been like this originally and it did not happen overnight. Over the new few posts I will attempt to present a simple explanation of how evolution works and how some of these species have come to such masters of mimicry and deception.

References

CATARINO, M. F., & ZUANON, J. (2010). Feeding ecology of the leaf fish Monocirrhus polyacanthus (Perciformes: Polycentridae) in a terra firme stream in the Brazilian Amazon. Neotropical Ichthyology. 8, 183-186.

Mühlacker, M. (2015). Monocirrhus polyacanthus camouflaged within dead leaves. http://medienwerkstatt-online.de/lws_wissen/vorlagen/showcard.php?id=21359&edit=0. Retrieved: 13/05/2015

WALKER, J. A. (2004). Kinematics and Performance of Maneuvering Control Surfaces in Teleost Fishes. IEEE JOURNAL OF OCEANIC ENGINEERING. 29, 572-584.

Syntomeida epilais

Syntomeida epilais

As seen in the last post, Syntomeida epilais or the Polka-Dot Wasp Moth has the ability to mimic a verbal signal produced by Cycnia tenera (Delicate Cycnia Moth). This signal is produced when in the presence of a bat, or similar predator, and they mimic the verbal signal of the unpalatable Cycnia tenera. This discourages the predators from consuming what appears to be a noxious tiger moth as Barber & Conner (2007) have described. This is a form of verbal Batesian mimicry employed by the Polka-Dot Wasp Moth. However, it is not limited to only this. 

They utilise bright colouration as well as morphological traits that are shared further by unpalatable species. Weller et al (2000) states that members of arctiine moth tribes Ctenuchini and Euchromiini exhibit morphological traits that are convincing wasp mimicry. This species of moth is such a member. The elongated and bright red tipped abdomen creates the illusion that the moth is a dangerous wasp. The bright colouration is also utilised to mimic its dangerous nature and increased when aggregated together, however, Conner (2009) states that their colouration may challenge predators to try. Syntomeida epilais has evolved and developed specialized traits that increase its chances of surviving. It has the ability to utilise not only visual mimicry but verbal mimicry and deception as well.

Figure 1: Syntomeida epilais feeding along a roadside. Photographer: Anonymous (2007)

References

Anonymous. (2007). Syntomeida epilais feeding along a roadside. http://www.jaxshells.org/11037.htm ; retrieved 06/05/2015

Barber, J. R., & Conner, W. E. (2007). Acoustic mimicry in a predator–prey interaction. National Academy of Sciences. http://www.pubmedcentral.nih.gov/articlerender.fcgi?artid=1890494.

Conner, W. E. (2009). Tiger moths and woolly bears: behavior, ecology, and evolution of the Arctiidae. Oxford, Oxford University Press.

Weller, S. J., Simmons, R. B., Boada, R., & Conner, W. E. (2000). Abdominal Modifications Occurring in Wasp Mimics of the Ctenuchine-Euchromiine Clade (Lepidoptera: Arctiidae). Annals of the Entomological Society of America. 93, 920-928.

Verbal Deception

Verbal deception

Much like the previous forms of deceptions and mimicry in animals; the use of sound and verbal signals can be exploited in order to deceive possible predators, prey or even members of the same (or different) species. Remember in my second blog? Batesian mimicry; where a harmless animals mimics the appearance of harmful one? Well, certain animals have evolved to utilise sound and verbal signals in the same way, to mimic the sounds of a harmful animal in order to avoid predation. Syntomrida epilais(Polka-Dot Wasp Moth) is an animal that utilises this method. It copies a clicking sound that the distasteful Cycnia tenera (Delicate Cycnia Moth), that predators have some learn, has signalled to predators. However, The Polka-Dot Wasp Moth is an incredible evolutionary example that utilises multiple deceptions and will be explored in great detail later in the future.

Dicrurus adsimilis (Fork-tailed Drongo) is a small passerine bird that has the ability to mimic false alarm calls of not only their on species but other species as well. The Drongo would make these alarm calls when watching a target handling there food, in response to which the target would abandon their food for the safety of cover. They then utilise this opportunity to steal the abandoned food. Flower (2011) has described that the Fork-tailed Drongo has even shown the ability to mimic the alarm calls of Suricata suricatta (Meercats). Further examples of verbal deception and mimicry will be explored next week.

Figure 1: Dicrurus adsimilis watching over a hunting ground. Photographer: Rust de winter (2004)

References

Flower, T. (2011). Fork-tailed drongos use deceptive mimicked alarm calls to steal food. Proceedings. Biological Sciences / The Royal Society. 278, 1548-55.

Rust de winter, L. (2004). Dicrurus adsimilis watching over a hunting ground. http://www.birdforum.net/opus/Fork-tailed_Drongo. Retrieved: 24/04/2015

Feigned Injury and Automimicry

This week we will examine another example of feigned injury deception as well as further explain what automimicry is as requested. The following week we will continue to define the different levels of deception and mimicry and in the future really explore the biology behind how species have developed these fascinating traits.

Feigning death is the level of feigned injury; to be able to deceive possible predators (or prey) into believing that they no longer are alive is incredible. The classic case of feigned death can be seen portrayed by Didelphimorphia (the opossums). Ever heard the expression playing dead or playing possum? When Didelphimorphia are threatened or harmed, they will display the appearance and smell as if they are dead. When they are feigning death, the animals lips are drawn back, revealing bared teeth, saliva foams around the mouth and they secrete foul-smelling fluid from their anal glands. This deters possible predators that prefer to take live prey. Thompson et al (1981) describes that the lack of movement in the prey species confers selection benefits by depriving predators of the necessary movement stimulus to launch a final attack. In this case the Opossum utilises feigned death as a defensive mimicry. Next week we will explore the use of feigned death as an aggressive mimicry.

Figure 1: Didelphimorphia playing dead. Photographer: T.Alter (2011).

 Now to take a step back and further explore Automimicry. As stated in my last post, automimicry is where one part of an organism’s body resembles another part. This only occurs within a single species. Chaetodon capistratus (the four-eyed butterfly fish) is such a species that utilises automimicry. It gets its common name from the large dark spots found on the rear portion of both sides of its body. These spots are lined with a bright white colouration creating the illusion that these are its eyes. A vertical bar on its true head runs through its eyes, making it harder to distinguish. Neudecker (1989) states that false eyespots are located in these areas of the body to allow escape and survival following an attack. When threatened they will flee by putting the false eyes in the direction of the predator. Most predators aim for the eyes of their prey, and by placing the false eyes towards the predator, the predator is clueless to the apparent escape attempt that follows.

Figure 2: Chaetodon capistratus displaying its false eyes. Photographer: J.Lyle (2012).

References

Lyle, J. (2012). Chaetodon capistratus displaying its false eyes. http://diver.net/bbs/posts003/87969.shtml; retrieved 19/04/2015

Neudecker, S. (1989). Eye camouflage and false eyespots: chaetodontid responses to predators. Environmental Biology of Fishes. 25, 143-157.

Thompson, R. K. R., Foltin, R. W., Boylan, R. J., Sweet, A., Graves, C. A., & Lowitz, C. E. (1981). Tonic immobility in Japanese quail can reduce the probability of sustained attack by cats. Animal Learning & Behavior. 9, 145-149.

Tony, A. (2011). Didelphimorphia playing dead. http://www.flickr.com/photos/ 78428166@Noo/6289417559/; retrieved 19/04/2015.

False Behaviour and Feigned Injury

False behavior and feigned injury

As a continuation of false behavior and an introduction to feigned injury, we will be exploring how birds in particular exploit these forms of deception. The techniques explored below are often called distraction displays as they function as anti-predator behaviours, utilised in order to attract the attention of the predator away from an object such as the nest.

Charadrius volciferus (killdeer) is a medium-sized plover that displays false behavior as a distraction display. When a predator begins to approach, the killdeer will move to several places, squatting as if incubating eggs. This is called false brooding and confuses the predator to the actual location of its nest. This was the most frequent female response of killdeer during early incubation when a predator approaches (Brunton, 1990). This is the response of a female, however, the male will display behavior very different to their partners. This is known as the broken-wing act and is a form of feigning injury.

Figure 1. Charadrius volciferus performing a broken-wing act. Photographer: Anonymous (2010)

This distraction display involves the bird walking away from the nesting area, with its wings held in a position that simulates injury. It then flaps helplessly emitting a distress signal. Thinking that they are easy prey, the predators will follow the killdeer away from the nest. This is done until the predator is well away from the nest and then the killdeer will simply fly away. Should the predator show no interest initially to the “injured” killdeer, they will move closer to the predator themselves and call out louder to grab their attention. Note that both techniques can be employed by both sexes. Brunton (1990) continues to state that males took greater risks when performing distraction displays and this may lead to unintentionally getting caught by the predator; a disadvantage to the evolved trait.

We will continue to explore feigned injuries next week.

References

1.  Anonymous. (2010). Charadrius volciferus performing a broken-wing act. http://www.anthive.com/killdeer/killdeer.html; retrieved 07/04/2015.

1.     2. Brunton, D. H. (1990). The effects of nesting stage, sex, and type of predator on parental defense by killdeer (<i>Charadrius vociferous</i>): testing models of avian parental defense. Behavioral Ecology and Sociobiology. 26, 181-190.