Date:September 22, 2015
Summary:Using a species of butterfly as an example, researchers have demonstrated how insects adapt their offspring to changing environmental conditions. The paper shows that females pass on their own experience to their brood, even if this experience was not necessarily ideal. This rapid adaptation has huge implications for our understanding of speciation in insects.
In their study, the researchers working under Prof. Andreas Erhardt firstly confirmed their earlier results, which showed that parent generations of butterflies can condition their offspring to the quality of forage plants that they experienced as larvae. Secondly, they were able to provide evidence for the first time that the mothers of these offspring change their egg-laying behavior and prefer to deposit their eggs on plants on which they themselves once developed.
The Basel-based environmental scientists showed that young females of the small cabbage white (Pieris rapae) were more precise than their parents in laying their eggs on the very same plants that they (and their parents) experienced as larvae. This provided the scientists with proof of the adaptation process. In their study, the scientists used cabbage as a host plant and added either a large or a small quantity of nitrogen to it, bearing in mind that fertilization with nitrogen is favorable for the development of butterfly larvae. Although the plant containing more nitrogen therefore represented the better choice, females that had developed as caterpillars on plants with less nitrogen showed a tendency to lay their eggs on the unfertilized cabbage.
This kind of breeding behavior has implications for our understanding of evolutionary and ecological processes. The conditioning of the offspring to the parents’ own experiences only takes place if the offspring grow up in a similar environment to the parent generation. In species in which this conditioning occurs, the preference for the corresponding experience is therefore reinforced with each generation. This breeds offspring that are increasingly better adapted to the respective host plant, even if this actually doesn’t provide optimal conditions — and, as a result, new species can emerge more quickly and more easily.
Although the conditioning may have succeeded in reducing the disadvantage caused by the less-favorable environment, it has not eradicated it completely. In compensation, females that accept or even prefer the disadvantageous environmental conditions have access to a greater selection of plants on which to lay their eggs, which leads to a reduction in competition within the species.
- Fabian Cahenzli, Barbara A. Wenk, Andreas Erhardt. Female butterflies adapt and allocate their progeny to the host-plant quality of their own larval experience. Ecology, 2015; 96 (7): 1966 DOI: 10.1890/14-1275.1
Males with low quality partners put more effort into parental duties to compensate for the shortcomings of their mate, and pay the price by dying younger
- September 22, 2015
- Non-genetic inheritance plays a huge role in determining the characteristics of offspring. For example, bad parenting creates bad parents-to-be, while well-cared for larvae mature into high quality parents.
When a good insect father pairs with a bad mother, he risks being exploited by her for childcare and could bear the ultimate cost by dying young.
A new study carried out with burying beetles also shows that bad parenting creates bad parents-to-be, while well-cared for larvae mature into high quality parents.
The research will be published in the journal eLife.
“Parents obviously play a huge role in determining the characteristics of their offspring,” says lead researcher Professor Rebecca Kilner from the Department of Zoology at the University of Cambridge.
“The aim of our study was to investigate non-genetic ways that parents achieve this.”
This is important because non-genetic inheritance could speed up the rate at which animal behaviour evolves and adapts in a rapidly changing world.
Whether examining mothers or fathers, the research team found that individuals that received no care as larvae were less effective at raising a large brood as parents, and died younger. In contrast, high quality care not only produces a larger brood, but individual offspring with a higher mass. This is consistent with previous studies.
“We found that parental care provides a mechanism for non-genetic inheritance. Good quality parents produce offspring that become good parents themselves, while offspring that receive poor parenting then become low quality parents. Our experiments show how parental care allows offspring to inherit characteristics of their parents, but non-genetically,” she says.
However, the team also found that offspring pay a cost for receiving high quality care, because it makes them vulnerable to exploitation if they pair up with a lower quality partner. This may explain why animals often choose a mate who is willing to put in a similar amount of effort as they as a parent. In this way, they are less vulnerable to exploitation.
The burying beetle, Nicrophorus vespilloides, uses the carcass of a small vertebrate such as a mouse as an edible nest for its young. As its name suggests, a breeding pair buries the carcass and preserves it with an antibacterial secretion. The mother lays eggs nearby in the soil, and the larvae crawl to the carcass when they hatch. Although the larvae can feed themselves, they also beg both parents for partly-digested food from the carcass.
In the current study, when males were paired with females that had received no post-hatching care as larvae, they had significantly shorter lives than those whose partners had received more care. The most likely explanation is that males with low quality partners put more effort into parental duties to compensate for the shortcomings of their mate, and paid the price by dying younger.
- RM Kilner, G Boncoraglio, JM Henshaw, BJM Jarrett, O De Gasperin, A Attisano, H Kokko. Parental effects alter the adaptive value of an adult behavioural trait. eLife, 2015; 4 DOI: 10.7554/eLife.07340