ILI PIKA - EVOLUTION

ILI PIKA

EVOLUTION

TAXONOMY OF THE ILI PIKA

Kingdom: Animalia

Phylum: Chordata

Class: Mammalia

Order: Lagomorpha

Family: Ochotonidae

Genus: Ochotona

Species: iliensis

(Li & Smith, 2019)

KEY EVOLUTIONARY CHANGES

Adaptation, defined as a heritable trait or behavior in an organism that aids in its survival in its present environment, takes place when a change in the range of genetic variation, or the variety of alleles in a population, occurs over time, thus increasing or maintaining the match of the population with its environment (Fowler et al., 2013). From generation to generation, the Ili pika has evolved physiologically to match its cold, high-altitude environment (Li & Ma, 1986; National Geographic Society, 2022a). A study by Feijó et al. (2020) concluded that pika species inhabiting high elevations exhibit the greatest phenotypic, or observable, variation within the genus Ochotona.

Biological adaptations to the alpine habitat of the Ili pika include cellular mechanisms—such as the secretion of enzymes—to cope with low oxygen levels at high altitudes as well as an unusually high metabolic rate to help the pika produce heat (Rankin et al., 2017). Monk and Ray (2022) suggest that the pika’s evolution regarding heat retention, which keeps them active in winter without the need to hibernate, is so complete that they lack common adaptations for shedding excess heat, such as sweating or other forms of evaporative cooling. Thus, with a limited capacity to physiologically regulate its body temperature, the Ili pika can overheat and die when exposed to temperatures as mild as 78ºF; as a result, the species has also behaviorally adapted to a lack of thermoregulation by retreating to cool, shady cracks in the talus rock (Varner & Dearing, 2014). These adaptations are critical for reproduction and survival (Rankin et al., 2017).

COMPARING LAGOMORPHS

Pikas in the family Ochotonidae and hares and rabbits in the family Leporidae comprise the taxonomic order Lagomorpha. Though the Ili pika is closely related to rabbits and hares, there are evident characteristics differentiating the two families (Li & Ma, 1986). Ge et al. (2013) suggest that differences between the evolutionary trajectories of both taxa were potentially driven by a change in global vegetation available throughout the various geological epochs. The table below compares characteristics of the families in the order Lagomorpha.

(Act For Libraries, n.d.; Animalia, 2023a; Animalia, 2023b; Diersing, 1984; Lagomorph Specialist Group, n.d.; Li & Ma, 1986; Nowak & Wilson, 1991)

COMPARING PIKA SPECIES

At 8 inches tall and 6 ounces at maturity, the Ili pika is considerably large in comparison to the other species in the genus Ochotona (Animalia, 2023b; Li & Smith, 2005). Its ears and hind feet are also among the largest of the pika species, measuring 36–37mm and 42–43mm, respectively (Li & Smith, 2005). Similar to other pikas, however, the Ili pika has a low rate of reproduction with a typical litter of two pups (Jordan, 2005; Li & Smith, 2005).

The Ili pika rarely vocalizes unlike other pika species; specifically, vocalizations have only been observed under direct threat of predation (Li & Smith, 2005; Smith, 2015; Smith et al., 2018). The markings on its coat are another observable difference as the Ili pika has three distinct rusty red stripes on its forehead and around its neck (BBC, 2015).

When species evolve in different directions from a common point, it is known as divergent evolution (Fowler et al., 2013). Though the 28 species in the genus Ochotona share a common ancestor, divergent evolution has caused the development of dissimilar characteristics, resulting in a variation in form and function and leading to speciation, the formation of a new species (Feijó et al., 2020; Fowler et al., 2013). Speciation occurs when two new populations formed from an initial population evolve in a way that it becomes impossible for the new populations to interbreed (Fowler et al., 2013). According to Niu et al. (2004), phylogenetic trees, or diagrams used to reflect the evolutionary relationships between organisms, suggest that divergences of pika species began during the early Pleistocene Epoch 2.8 million years ago (Fowler et al., 2013).

REFERENCES

Act For Libraries. (n.d.). The difference between hares, rabbits and pikas. http://actforlibraries.org/the-difference-between-hares-rabbits-and-pikas

Animalia. (2023a). Collared pika. https://animalia.bio/collared-pika

Animalia. (2023b). Ili pika. https://animalia.bio/ili-pika

Arnold, C. (2015, March 19). Unbelievably cute mammal with teddy bear face rediscovered [Photograph]. National Geographic Society. https://nationalgeographic.com/animals/article/150319-china-ili-pika-animals-conservation-science-rare-species

BBC. (2015, March 26). China’s Ili pika: The ‘magic bunny’ goes viral. https://bbc.com/news/blogs-china-blog-32079630

Diersing, V. (1984). Lagomorphs. In Anderson, S., & Jones, J., Jr. (Eds.), Orders and families of recent mammals of the world (pp. 241–248). John Wiley & Sons.

Feijó, A., Ge, D., Wen, Z., Xia, L., & Yang, Q. (2020). Divergent adaptations in resource-use traits explain how pikas thrive on the roof of the world. Functional Ecology, 34, 1826–1838. https://doi.org/10.1111/1365-2435.13609

Fowler, S., Roush, R., & Wise, J. (2013, April 25). Concepts of biology (Chapters 11 & 12). OpenStax. https://openstax.org/books/concepts-biology/pages/11-introduction

Ge, D., Wen, Z., Xia, L., Zhang, Z., Erbajeva, M., Huang, C., & Yang, Q. (2013). Evolutionary history of lagomorphs in response to global environmental change. PLOS One, 8(4), e59668. https://doi.org/10.1371/journal.pone.0059668

Jordan, D. (2005). Ochotona. Animal Diversity Web. https://animaldiversity.org/accounts/Ochotona_macrotis

Lagomorph Specialist Group. (n.d.) Lagomorphs. IUCN Species Survival Commission. https://lagomorphspecialistgroup.org

Li, W. D., & Ma, Y. (1986). A new species of Ochotonidae, Lagomorpha. Acta Zoologica Sinica, 32, 375–379.

Li, W. D., & Smith, A. T. (2005). Dramatic decline of the threatened Ili pika Ochotona iliensis (Lagomorpha: Ochotonidae) in Xinjiang, China. Oryx 39(1) 30–34. https://doi.org/10.1017/S0030605305000062

Li, W. D., & Smith, A. T. (2019). Ochotona iliensis. The IUCN Red List of Threatened Species 2019, e.T15050A45179204. https://doi.org/10.2305/IUCN.UK.2019-1.RLTS.T15050A45179204.en

Lu, S., & Hunt, K. (2015, March 24). Meet the animal that's rarer - and cuter - than a panda [Photograph]. CNN. https://cnn.com/2015/03/23/asia/china-endangered-pika

Monk, E. M., & Ray, C. (2022). Revisiting talus and free-air temperatures after 50 years of change at an American pika (Ochotona princeps) study site in the Southern Rockies. PLOS Climate, 1(7), e0000049. https://doi.org/10.1371/journal.pclm.0000049

National Geographic Society. (2022). Adaptation. https://education.nationalgeographic.org/resource/adaptation

Niu, Y., Wei, F., Li, M., Liu, X., & Feng, Z. (2004). Phylogeny of pikas (Lagomorpha, Ochotona) inferred from mitochondrial cytochrome b sequences. Folia Zoologica, 53(2), 141–155. https://researchgate.net/publication/240638409

Nowak, R., & Wilson, D. (1991). Walker’s mammals of the world. Johns Hopkins University Press.

Rankin, A. M., Galbreath, K. E., & Teeter, K. C. (2017). Signatures of adaptive molecular evolution in American pikas (Ochotona princeps). Journal of Mammalogy, 98(4), 1156–1167. https://doi.org/10.1093/jmammal/gyx059

Smith, A. T., Johnston, C. H., Alves, P. C., & Hackländer, K. (2018). Lagomorphs: Pikas, rabbits, and hares of the world. Johns Hopkins University Press.

Smith, D. (2015). Cute ‘magic rabbit’ Ili pika more endangered than pandas spotted for first time in 20 years. Mirror. https://mirror.co.uk/news/world-news/cute-magic-rabbit-ili-pika-5395979

Varner, J., & Dearing, M. D. (2014). Dietary plasticity in pikas as a strategy for atypical resource landscapes. Journal of Mammalogy, 95(1), 72–81. https://doi.org/10.1644/13-MAMM-A-099.1

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