A new study, entitled “Predator-induced phenotypic plasticity within- and across-generations: A challenge for theory?” and published in the Proceedings of the Royal Society B: Biological Sciences by Dr. Matthew R. Walsh, assistant professor of biology at the Department of Biology at the University of Texas at Arlington, investigated the relationship between within- versus across-generation plasticity by assessing the effect of predator cues on the life-history traits of Daphnia ambigua.
The process of “phenotypic plasticity” is when an organism changes its trait expressions or physical characteristics or those of its offspring, due to external factors. Daphnia abigua, also known as the water flea, can perform this by speeding up its own physical maturation in response to a predator threat or speeding the maturation of its offspring. The established theory claims that expected environmental variation selects for both increased within- and across-generation responses. Nevertheless, there are no experimental studies supporting this prediction.
Dr. Walsh and his team exposed clones of Daphnia collected from six lakes in Connecticut to a series of danger signals, such as kairomones, a chemical signal produced by Daphnia predator fish, and Daphnia alarm cues, chemicals that other Daphnia emit to signal danger, at different intervals to evaluate patterns of plasticity within and across generations of Daphnia. The authors found that these danger signals could lead to alterations in development rates of the Daphnia that continue for two generations. Moreover, the data showed the existence of a negative relationship between changes of development within generations and trans-generation, meaning more changes within a generation were associated with fewer changes from the average in the next generation.
“The surprising aspect of our research is, they couldn’t do both,” said Dr. Walsh, the lead author of the study, in a press release. “They could either do something that strengthens their own fitness and their own survival or they could do something to strengthen the fitness and survival of future generations. What we’re trying to find now is what makes these responses happen.”
The type of research led by researchers like Walsh interested in understanding the potential of organisms to change the expression of traits across various generations will have a major impact in many challenges that environmental researchers are currently facing that involve biodiversity.
“Plasticity is widespread across the tree of life,” said Dr. Walsh. “These non-genetic responses to environmental signals may represent a key mechanism that allows organisms to persist in the face of ongoing climate change.” concluded Dr. Walsh.
“Dr. Walsh’s research suggests that environmental cues experienced by one generation can affect growth and maturation of future generations in ways that are not explained by current theory,” said Laura Gough, interim chair of the UT Arlington Department of Biology and a professor who has studied effects of climate change on plant communities.
“This elegant study highlights the need for the use of similar experiments to test important biological theories with direct implications for how organisms are affected by changes in their environment.”