Phenotypic Variation in Rock Pocket Mouse: What Lies Beneath? Biology

This essay delves into the phenotypic variation observed in rock pocket mice, focusing on the underlying genetic mechanisms that drive habitat-specific adaptation. The study emphasizes the role of natural selection in shaping the diverse coat colors of these mice, which allows them to blend in with their environment and avoid predation. The essay challenges the hypothesis that phylogeny is the primary source of phenotypic variation and instead highlights mutation and migration as key factors. It explores how the color polymorphism in rock pocket mice is closely tied to their habitat, demonstrating the correlation between environmental factors and the evolution of genetic variations within a single species. Furthermore, the essay discusses the potential benefits of migration in promoting local adaptation, even when gene flow is high, by introducing advantageous alleles. The essay concludes by addressing the role of mutation as a source of genetic variation in rock pocket mice. It suggests that, although mutations may induce large-scale evolution, such alterations may not always affect the phenotype.

Running head: PHENOTYPIC VARIATION IN ROCK POCKET MOUSE: WHAT LIES
BENEATH?
PHENOTYPIC VARIATION IN ROCK POCKET MOUSE: WHAT LIES BENEATH?
Name of the Student
Name of the University
Author Note

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PHENOTYPIC VARIATION IN ROCK POCKET MOUSE: WHAT LIES BENEATH?
A primary objective of evolutionary biology is to elucidate and explore the variation
in morphology that exists across species. Genetic variation represents the range of genetic
differences in a population. Natural selection influences the genetic variation of a species in a
way which can affect the frequency of gene variations, already present in the population
(Real 2017). Understanding the origins of such intraspecific deviation provides information
about the impact of local environment as a deciding factor for rapid evolution. Purpose of this
think piece is to highlight the underlying mechanism of genetic variation in causing habitat
specific adaptation in rock pocket mouse.
Contrary to the popular hypothesis that advocates phylogeny as a source of
phenotypic variation in a population, recent advances underline mutation and migration as
sources of genetic variation (McRobie, Moncrief and Mundy, 2019). On this context, the
extensive colour polymorphism exhibited by rock paper mice forms the centrepiece of this
discussion that aims to clarify the correlation between the location of habitat and evolution of
genetic variations over time in a single species.
Researchers have mainly been keen on studying the evolution of colour variances in
response to geographic conditions. The natural habitat of rock paper mouse is typically in
rocky regions across deserts, and hence their habitation is uneven. Various subspecies of
this mouse living in small isolated lava flows represent drastic body colour differences
among themselves. Mice populations from non-lava regions also display a difference in coat
colour, that often narrowly resembles the colour of the substrate on which they live
(Hoekstra, Krenz and Nachman 2005). Such disparities in colour cannot be merely
attributable to their phylogenic history, as evidence suggests, populations of a species connect
via recent ancestry, that is, a high gene flow or migration. Irrespective of an intense local
genetic flow, polymorphism in colour is highly associated with habitat colour, corroborating
the link of strong natural selection in this species and morphological diversity (Bernatchez

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PHENOTYPIC VARIATION IN ROCK POCKET MOUSE: WHAT LIES BENEATH?
2016). There is a pattern of substrate matching between several neighbouring populations of
rock paper mice that experience a high level of gene flow indicating the presence of a
substantial selection occurring naturally to sustain habitat-specific phenotypes.
Migration is commonly perceived to be a hindrance in the proliferation of local
adaptation across populations. However, results observed from examining the magnitude of
gene flow taking place between lava inhabitant mice and other nearby populations dwelling
in light-coloured rocks suggest a different possibility (Hoekstra, Krenz and Nachman 2005).
It indicates that migration between lava flows could be beneficial in promoting local
adaptation, by incorporating advantageous alleles into intraspecific nearby populations
undergoing similar patterns of selection. As a result, the possibility of mutation being a
source of genetic variation in case of rock paper mice, seems weak. Although, mutation may
induce large scale evolution, such alterations may not affect the phenotype.

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PHENOTYPIC VARIATION IN ROCK POCKET MOUSE: WHAT LIES BENEATH?
References
Bernatchez, L., 2016. On the maintenance of genetic variation and adaptation to
environmental change: considerations from population genomics in fishes. Journal of Fish
Biology, 89(6), pp.2519-2556.
Hoekstra, H.E., Krenz, J.G. and Nachman, M.W., 2005. Local adaptation in the rock pocket
mouse (Chaetodipus intermedius): natural selection and phylogenetic history of populations.
Heredity, 94(2), pp.217-228.
McRobie, H.R., Moncrief, N.D. and Mundy, N.I., 2019. Multiple origins of melanism in two
species of North American tree squirrel (Sciurus). BMC evolutionary biology, 19(1), p.140.
Real, L. ed., 2017. Ecological genetics. Princeton University Press.