I have come across two papers this week that are really interesting. The first has only just come out in Proceedings of the Royal Society, by Dieter Lukas, and is a cross species investigation into male breeding tenure reproductive skew. The second is a paper that was published online last year and is an amazing study that shows that an induced fear of an olfactory cue can be passed on to offspring and grand-offspring in mice, by Brian Dias.
Lukas & Clutton-Brock (2014) Costs of mating competition limit male lifetime breeding success in polygynous mammals. Proc R Soc, 281:20140418
Although differences in breeding lifespan are an important source of variation in male fitness, the factors affecting the breeding tenure of males have seldom been explored. Here, we use cross-species comparisons to investigate the correlates of breeding lifespan in male mammals. Our results show that male breeding lifespan depends on the extent of polygyny, which reflects the relative intensity of competition for access to females. Males have relatively short breeding tenure in species where individuals have the potential to monopolize mating with multiple females, and longer ones where individuals defend one female at a time. Male breeding tenure is also shorter in species in which females breed frequently than in those where females breed less frequently, suggesting that the costs of guarding females may contribute to limiting tenure length. As a consequence of these relationships, estimates of skew in male breeding success within seasons overestimate skew calculated across the lifetime and, in several polygynous species, variance in lifetime breeding success is not substantially higher in males than in females.
http://rspb.royalsocietypublishing.org/content/281/1786/20140418.long
This paper is really cool because most of what you get taught as an undergrad about intrasexual conflict states that reproductive skew is really high among males because only a few are able to control harems and breed. However, this paper takes a longer-term view and shows that at one point in time skew is high, but because of short tenure length this effect is massively reduced. The authors show that variance in lifetime reproductive success in males and females may not actually be that different. All of this is likely driven by the high costs of guarding females from competing males.
Dias & Ressler (2014) Parental olfactory experience influences behavior and neural structure in subsequent generation. Nature Neuroscience, 17:89-96
Using olfactory molecular specificity, we examined the inheritance of parental traumatic exposure, a phenomenon that has been frequently observed, but not understood. We subjected F0 mice to odor fear conditioning before conception and found that subsequently conceived F1 and F2 generations had an increased behavioral sensitivity to the F0-conditioned odor, but not to other odors. When an odor (acetophenone) that activates a known odorant receptor (Olfr151) was used to condition F0 mice, the behavioral sensitivity of the F1 and F2 generations to acetophenone was complemented by an enhanced neuroanatomical representation of the Olfr151 pathway. Bisulfite sequencing of sperm DNA from conditioned F0 males and F1 naive offspring revealed CpG hypomethylation in the Olfr151 gene. In addition, in vitro fertilization, F2 inheritance and cross-fostering revealed that these transgenerational effects are inherited via parental gametes. Our findings provide a framework for addressing how environmental information may be inherited transgenerationally at behavioral, neuroanatomical and epigenetic levels.
http://www.nature.com/neuro/journal/v17/n1/abs/nn.3594.html
This particular paper blows my mind. The concept that changes to an animals behaviour, mediated through experience and presumably some sort of neural rewiring can be passed on to their offspring is amazing. The authors go through how the methylation mediates this but how gametic DNA is changed due to changes to the DNA in the soma is still amazing. It all sounds a bit Lamarckian. But we had a chat in our office and were thinking about adaptive fear responses and inate fears that many animals have, potentially this has tapped into some evolutionary mechanism to assimilate threats. Still an awesome paper.
Lukas & Clutton-Brock (2014) Costs of mating competition limit male lifetime breeding success in polygynous mammals. Proc R Soc, 281:20140418
Although differences in breeding lifespan are an important source of variation in male fitness, the factors affecting the breeding tenure of males have seldom been explored. Here, we use cross-species comparisons to investigate the correlates of breeding lifespan in male mammals. Our results show that male breeding lifespan depends on the extent of polygyny, which reflects the relative intensity of competition for access to females. Males have relatively short breeding tenure in species where individuals have the potential to monopolize mating with multiple females, and longer ones where individuals defend one female at a time. Male breeding tenure is also shorter in species in which females breed frequently than in those where females breed less frequently, suggesting that the costs of guarding females may contribute to limiting tenure length. As a consequence of these relationships, estimates of skew in male breeding success within seasons overestimate skew calculated across the lifetime and, in several polygynous species, variance in lifetime breeding success is not substantially higher in males than in females.
http://rspb.royalsocietypublishing.org/content/281/1786/20140418.long
This paper is really cool because most of what you get taught as an undergrad about intrasexual conflict states that reproductive skew is really high among males because only a few are able to control harems and breed. However, this paper takes a longer-term view and shows that at one point in time skew is high, but because of short tenure length this effect is massively reduced. The authors show that variance in lifetime reproductive success in males and females may not actually be that different. All of this is likely driven by the high costs of guarding females from competing males.
Dias & Ressler (2014) Parental olfactory experience influences behavior and neural structure in subsequent generation. Nature Neuroscience, 17:89-96
Using olfactory molecular specificity, we examined the inheritance of parental traumatic exposure, a phenomenon that has been frequently observed, but not understood. We subjected F0 mice to odor fear conditioning before conception and found that subsequently conceived F1 and F2 generations had an increased behavioral sensitivity to the F0-conditioned odor, but not to other odors. When an odor (acetophenone) that activates a known odorant receptor (Olfr151) was used to condition F0 mice, the behavioral sensitivity of the F1 and F2 generations to acetophenone was complemented by an enhanced neuroanatomical representation of the Olfr151 pathway. Bisulfite sequencing of sperm DNA from conditioned F0 males and F1 naive offspring revealed CpG hypomethylation in the Olfr151 gene. In addition, in vitro fertilization, F2 inheritance and cross-fostering revealed that these transgenerational effects are inherited via parental gametes. Our findings provide a framework for addressing how environmental information may be inherited transgenerationally at behavioral, neuroanatomical and epigenetic levels.
http://www.nature.com/neuro/journal/v17/n1/abs/nn.3594.html
This particular paper blows my mind. The concept that changes to an animals behaviour, mediated through experience and presumably some sort of neural rewiring can be passed on to their offspring is amazing. The authors go through how the methylation mediates this but how gametic DNA is changed due to changes to the DNA in the soma is still amazing. It all sounds a bit Lamarckian. But we had a chat in our office and were thinking about adaptive fear responses and inate fears that many animals have, potentially this has tapped into some evolutionary mechanism to assimilate threats. Still an awesome paper.
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