It’s been a massive couple months for Fonti Kar, who has pulled off an amazing thesis. Congratulations! She remained cool, calm and collective right to the end and wrapped up her thesis with plenty of time to spare!
Fonti did two huge experiments that jived well together. Her first chapter explored the predictors of contest outcome in our favourite lizard, Eulamprus quoyii. This is one area we lack a lot of information on and Fonti has shown that there are some very interesting assessment stages that Eulamprus proceed through before escalating to fights. Actually, escalated fights that result in fighting and biting between two males only occurred in 38% of contest pairings. Interestingly, given the differences between escalated and non-escalated (i.e. contests resolved through signalling) contests, she predicted that the predictors of contest outcome should vary depending on these assessment stages. While most of her predicted traits did not affect contest outcome (which is interesting given she did 116 contests!), she did find a prior winning effect that influenced the probability of initiating a contest, which was a strong predictor of contest outcome (if you initiated you won!). In support of her prediction, she also showed that the importance of initiating a contest depended on whether the contest escalated or not. Males that initiated in non-escalated contests had a much higher probability of winning whereas it didn’t seem to make a difference if they decided to initiate a contest that resulted in physically fighting with another male.
Fonti’s second chapter made use of this huge contest experiment to look at the role of social dominance (whether you win against other males during a contest) on social information use. Making use of the contest data she paired males of known contest history together and randomly assigned one of these males (dominant or subordinate) to be the experimental lizard and the other was designated the demonstrator lizard. Dominant males were winners and subordinate lizards the losers of contests. The demonstrator was trained to flip lids to access a mealworm under a rewarded lid and was then allowed to show the experimental lizard this task. Importantly, we have shown that E. quoyii do use social information to learn such a task (click here to learn more about that work), but only young lizards used social information to learn. However, age and dominance often go hand in hand in lizards and so Fonti attempted to control for age by assigning equal numbers of large and small males across three treatment groups: 1) Where the dominant male was the demonstrator; 2) the subordinate male was the demonstrator and 3) a control group, which was a mix of dominant and subordinate experimental lizards that were just shown the other lizard but not doing the task. She specifically predicted that watching a male that was dominant or subordinate to yourself would affect how you use social information. In other words, subordinate male lizards would pay more close attention to those big macho males, while macho males wouldn’t care what some small little male was up to. Her results were interesting, but to make a long story short, social dominance didn’t seem to affect social information use in anyway and actually her results were similar to those found in previous work comparing old males – they didn’t seem to use social information at all! This is pretty cool because it suggests that age may really be the big driver of social information use for these particular tasks.
All this hard work required a massive celebration (a night out on the city) and a special trophy for Fonti to remind her of her lizard contests thanks to her fellow MSc friends (See below).
Come April I’ll be moving to the University of New South Wales (UNSW), Sydney, to take up an ARC funded DECRA Fellowship working in the new lab of A/Prof Shinichi Nakagawa. While it’s sad to be moving away from the LizardLab Martin will still be a big part of some very cool projects and I’ll still make regular visits. Shinichi, Martin, Scott Keogh (ANU) and I have big plans to conduct meta-analyses, develop individual-based models and start some very exciting empirical work on Garden skinks looking at how metabolism influences personality and learning. We’ll be testing some new and exciting theoretical developments in this area and we are looking for a bright, enthusiastic PhD student to be part of our team. If you’re interested in being part of the lab and working in a very exciting and dynamic place, such as UNSW, please shoot me an email! The details on the PhD advertisement are listed below:
PhD position studying lizard personality, learning and metabolism at the University of New South Wales
Dr. Daniel Noble and A/Professor Shinichi Nakagawa in the Evolution & Research Centre (E&ERC), at the University of New South Wales (UNSW) are seeking a highly motivated and enthusiastic student to study the covariation between metabolism, personality and learning in a model Australian lizard system. The student will join a newly formed lab group at UNSW and be part of an exciting multidisciplinary team building links between environmentally driven effects on phenotypic variation and the consequences of these effects on fitness. The student will combine theory with extensive experimental work manipulating incubation temperatures, taking behavioural and physiological measures, and establishing controlled semi-natural breeding experiments to obtain multigenerational data. They will use cutting edge molecular (e.g. SNP genotyping) and statistical tools (e.g. meta-analysis, Bayesian and individual-based modeling) during their candidature to address important topical questions in evolutionary and behavioural ecology. The student will also work with collaborators from Macquarie University, Sydney University, and The Australian National University in addition to other research groups at UNSW. We expect the student to travel to both international and national conferences to present the results of their work during their candidature.
If you are interested in joining our exciting project at E&ERC, UNSW please send an email with an expression of interest, why you are interested in joining the lab and your CV to Dan (email@example.com) and Shinichi (firstname.lastname@example.org). High quality applicants will apply for an APA scholarship through UNSW, which covers tuition and provides a stipend ($25,392/year; more details at: https://research.unsw.edu.au/domestic-research-candidate-scholarships). Opportunities exist to make additional income through teaching positions advertised in the department.
Note that to apply for an APA scholarship, the candidate needs to be Australian or New Zealand citizen or permanent resident. However, we welcome students who would like to bring their own scholarship to join our project.
I’ve been reading some interesting books lately! This one was a hard one to put down as the authors provided a number of really engaging case-studies to support an “extended evolutionary synthesis”. I thought I would give a brief synopsis and discuss some of the arguments Jablonka and Lamb made in their excellent book entitled: “Evolution in Four Dimensions: Genetic, Epigenetic, Behavioral and Symbolic Variation in the History of Life”
In their updated book, Jablonka and Lamb argue that the Modern evolutionary synthesis, developed in the 1960s, is lacking and is not sufficient in explaining evolutionary change on its own. In particular, they suggest that our understanding of heredity and the generation of phenotypic variants that is based mainly on genes is incomplete and can be misleading. They argue that we need to be thinking about alternative modes of inheritance, different ways phenotypic variants are created and the interactions between different inheritance systems and the environment to fully understand evolutionary change. They suggest that there exist four inheritance systems: genetic, epigenetic, behavioural and symbolic/cultural, although they recognise that they are not necessarily mutually exclusive. In the chapter on the genetic inheritance system, which is the major foundation of the modern evolutionary synthesis, they argue that genes alone are not sufficient to explain all evolutionary change because genes often do not map neatly to phenotypes and mutations are too slow for rapid evolutionary changes to proceed. Particularly problematic are the ideas that mutations are often random and deleterious and given these points it is difficult to explain how organisms can adapt quickly to their environment. Alternative inheritance systems and phenotypic plasticity are therefore extremely important in evolution. In this chapter they challenge a few of these ideas about mutations. For example, it may not generally be the case that mutations are random and they provide evidence that, in light of environmental stresses, mutations can occur non-randomly in the genome and that certain genes appear to be bigger targets than others. Although they do not deny that selection on genetic variants is extremely important in evolution and they do indeed discuss the role of environmental stressors in exposing hidden genetic variation, which is a very important point, they do make it fairly clear that our current view and disproportionate emphasis on genes is not justified for reasons outlined below.
Discussion of the epigenetic inheritance system was a major component of the book and was threaded through different inheritance systems (particularly behaviour). Epigenetic inheritance is when phenotypic variants, not stemming from changes to DNA sequences, are transmitted to subsequent generations. This could be through changes in germ line cell methlyation or siRNA transfer, but also through the perpetuation of environments across generations that lead to similar developmental changes in the next generation. This could be important in light of developmental canalisation and genetic assimilation if selection is strong and consistent. Jablonka and Lamb discuss a huge number of interesting mechanisms that lead to epigenetic changes including DNA methlyation (silencing of gene expression), chromatin remodelling, prions (proteins that change the conformation of other proteins to “look” more like them) and more interestingly small RNA’s (e.g siRNA and miRNA). In their new chapter they discuss some amazing examples of the role epigenetic effects can play in evolution. Two that I was particularly fascinated by were the role of maternal care in rat pups and odour imprinting in C. elegans because these were also directly relevant to the behavioural inheritance system. In the first example, Jablonka and Lamb reference a study on rats which showed how maternal care (licking and grooming) of offspring influences their behaviour as they age. Offspring become more resistant to stress and are more exploratory. Interestingly, offspring raised by these caring mothers are also more likely to lick and groom their offspring and thus the behaviour is perpetuated. These behaviours seemed to be linked with differences in DNA methylation and DNA associated proteins which likely change gene expression. In the second example, C. elegans that were raised on a particular odour during a larval stage where more likely be attracted to this odour as adults and increased their egg production in response to it. This behaviour does appear to be transferred to their offspring, but if exposure to the odour does not persist it lasts for only a few generations. However, surprisingly, if the odour exposure is consistent (i.e. exposure occurs across 4 generations) then it can be sustained and inherited for up to 40 generations! Although the epigenetic mechanism involved here are not known, given that they lack DNA metlyation, they suggest it may be linked to sRNA.
One particularly relevant and interesting part of the book was on the role of learning and innovation in evolutionary change. They discuss a few interesting examples of how social learning may facilitate phenotypic evolution. Innovative behaviour or trial and error learning may lead to an individual learning to solve a new problem, social learning can then lead to transgenerational inheritance of this “acquired trait”. They provide some well known examples here including how Israeli black rats learn from adults about how to eat pine cones and thus the behaviour can be transmitted across generations and the rapid and extensive spread of bottle top removing by tits in the UK. These behavioural innovations are acquired traits that are passed between generations and interestingly transmission can not only occur vertically (i.e. parents to offspring) but also horizontally (between totally unrelated individuals).
In the chapters on symbolic or cultural inheritance they discuss a lot about how cultural traditions can be transmitted and how small additions/changes can leading to new variants that are slowly accumulated and incorporated into existing traditions. They also talk quite a lot about the evolution of language. Probably one of the most interesting things about the book was that these different inheritance systems are incredibly interconnected and Jablonka and Lamb really highlighted the constant feedback loop between selection and the environment. They argue that often “genes are follows” so changes in environmental niches change the environment and the selection pressures individuals experience and selection can subsequently lead to genetic evolution to fine tune adaptation to the new environment. They highlight a few cool examples, but the most interesting one was the apparent spread of alleles that allowed humans to digest lactaose that were followed by changes in agricultural practices.
Throughout the book they discuss how each of these inheritance systems can lead to evolutionary change while “holding” all the other inheritance systems constant and how each of the different inheritance systems influence each other. They provided metaphorical examples about how each system can lead to phenotypic evolution. For example, when there is no genetic variation in the system how can phenotypic evolution occur? While obviously unrealistic, these examples do highlight how the fundamentals of evolution (variation, heredity and selection) can lead to changes in the frequency of phenotypes over time. They also discuss several criticism of the importance of the three additional inheritance systems in evolution, and a point that was brought up often was about the stability of these phenotypic changes in the epigenetic, behavioural and cultural realms. While I think this is certainly a valid point, and it is clear that some cases of epigenetic effects are not necessarily long term, there is indeed evidence that these effects can be extremely long-term and theoretical works has shown that they can influence evolutionary dynamics (e.g. rate sod genetic evolution). In addition, I do think that a similar argument could be made about genetic variants. If we think of evolution as simply changes in allele frequencies over time then there is nothing wrong about allelic variants fluctuating back and forth over time (e.g. frequency-dependent selection at a locus). Would we not call this evolution? I think an important distinction that needs to be made is the difference between genetic evolution and phenotypic evolution. Of course, if you view evolution as changes in allele frequencies over time then you probably won’t accept that epigenetic, behavioural and cultural inheritance systems are all that important except in changing the environment in which selection acts. However, if you distinguish between genetic and phenotypic evolution, which Jablonka and Lamb show sort of hint at, both can occur independent of one another and I think this helps to clarify things.
Overall, I found this book to be extremely interesting, filled with new ideas, new ways of thinking about evolutionary change and stuffed with fascinating examples. Their new updated chapter was refreshing and involved a foray into the new developments in the field. Given the evidence presented in the book, even though we are still just at the tip of the iceberg, they do indeed provide a compelling argument for an “Extended Evolutionary Synthesis” in evolutionary biology.