Invasions of non-native species are one of the world’s greatest environmental and economic threats. Identifying the abiotic and biotic factors responsible for the establishment of invasive species is thus a key challenge. To address this challenge we work on the European wall lizard, a lacertid lizard species that is native to mainland Europe but has been introduced to multiple non-native locations in the UK (as well as elsewhere). Our research is aimed at trying to understand where the wall lizards in the UK came from, how they got there and what the consequences of their introduction history are for the local populations. To achieve this we use a combination of field work and detailed molecular and analytical approaches. We have established that populations in the UK are the result of both direct introductions from Europe (mostly North-Western France, Central Italy, Tuscany) and introductions from already established non-native populations in the UK. Furthermore, we have shown that colonisation history has strong effects on the loss of genetic diversity in non-native populations and that early embryonic mortality is high in non-native populations compared to native ones.
Invasions of non-native species also offer us valuable systems to study contemporary evolution. This is because they often encounter novel environments that impose strong directional selection. We have shown that wall lizards, have adapted to cool climate in the UK within the few decades of their arrival. Specifically, females in England hold on to their eggs for longer before laying, capitalizing on the fact that a basking lizard can maintain a much higher body temperature than the surrounding soil. Embryos in English populations also develop faster than their native counterparts, particularly at the cool temperatures that are common in England but rare in their native range. Together this means that offspring hatch out several weeks earlier than they would have done when wall lizards first arrived in England, potentially facilitating population persistence of these lizards.
Our more recent work has focused on the genetic and epigenetic mechanisms underpinning this divergence. Using analyses of gene expression we have shown that embryos from nonnative populations exhibit gene expression profiles consistent with directional selection following introduction, but that the specific genes that were affected differed between French and Italian populations. However, while the genes themselves differed, the actual function of the genes that changed their expression showed substantial similarity between lineages and were consistent with mechanisms that should promote developmental rate. This suggests that both French and Italian populations have found different ways to solve the same problem of coping with extreme thermal conditions. Ongoing work will focus on the role that maternal effects play in mediating these patterns.
This work is carried out in collaboration with Tobias Uller (Lund) and Nathalie Feiner (Lund).
If you want to know more:
Feiner, N., Rago, A., While, G.M. and Uller, T. (2018) Signatures of selection in embryonic transcriptomes of lizards adapting in parallel to cool climate. Evolution. 72:67-81.
MacGregor, H.E.A., While, G.M. and Uller, T. (2017) Comparison of reproductive investment in native and non-native populations of common wall lizards reveals sex differences in adaptive potential. Oikos. 126:1564-1574.
Michaelides, S., While, G. M., Zajac, N., Aubret, F., Calsbeek, B., Sacchi, R., Zuffi, M. and Uller, T. (2016) Loss of genetic diversity and increased embryonic mortality in non-native lizard populations. Molecular Ecology, 25:4113-4125.
While, G. M., Williamson, J., Prescott, G., Horvathova, T., Fresnillo, B., Beeton, N.J., Halliwell, B., Michaelides, S., and Uller, T. (2015) Adaptive responses to cool climate promotes persistence of a non-native lizard. Proceedings of the Royal Society of London, B. 282, 20142638.
Rago, A., While, G.M. and Uller, T. (2012) Introduction pathway and climate trump ecology and life history as drivers of establishment success in alien amphibians. Ecology and Evolution, 2, 1437-1445