Epigenetics are Not Always Adaptive
Epigenetics is the branch of biology that studies how the
environmental conditions experienced by one generation can have a non-genetic
influence on their offspring. The vast majority of epigenetic research demonstrates
how this phenomenon can increase the survivorship and fitness of offspring,
however Leung et al. (2013) clearly exposed
the possibility for epigenetics to be non-adaptive. In their study, parent
organisms of marine tubeworms Hydroides
elegans and Hydroides diramphus
were exposed to hypoxic (low oxygen level) or normoxic (normal oxygen level)
conditions. After 2 weeks of hypoxia, both species produced significantly fewer
eggs than those in normoxic conditions. Such decreases in fecundity can directly
reduce the future success of a species. Furthermore, after the hypoxia
treatment, H. elegans produced eggs
with slower growth, and embryonic abnormalities that would prevent their future
development; however these disadvantages were not observed for H. diramphus. These differences in
tolerance to hypoxia led the authors to suggest that H. diramphus could completely displace H. elegans if ocean oxygen concentrations continue to decrease as a
result of climate change. This study illustrates how environmental changes
experienced at one time can negatively affect the number and quality of
offspring in the future, thus prolonging the effect. This influences the
success of the affected species, its competitors, and those within the
associated food webs, and therefore has evolutionary importance. This research
has established the potential for climate change to trigger epigenetic effects
capable of dictating the patterns of success, decline, and extinction that ultimately
drive evolution.
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REFERENCES
Leung, J. Y. S.,
Cheung, S. G., Qiu, J. W., Ang, P. O., Chiu, J. M. Y., Thiyagarajan, V. and
Shin, P. K. S. (2013). Effect of parental
hypoxic exposure on embryonic development of the offspring of two serpulid
polychaetes: Implication for transgenerational epigenetic effect. Marine Pollution Bulletin, 74. 149-155.