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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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.