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Island Selection and Lizard Ecology

Final Report Summary - ISLE (Island Selection and Lizard Ecology)

Island selection and lizard ecology
Exploring the interaction between natural selection and evolution is vital for understanding the diversity of life and vice versa, as knowing how selection acts on species diversification is basic for unravelling evolutionary mechanisms. Ecologists and evolutionary biologists have as a very challenging aim to discover the ways evolution operates in an ecological context. Since Darwin coined the natural selection concept a long time ago, a number of laboratory studies have documented evolution by natural selection. Nevertheless, few are genuine selection experiments designed and executed in nature. However, these studies are highly needed as they contribute toward understanding evolution as it happens in nature, strongly affected by context-specific trade-offs and pleiotropic effects only present in the heterogeneity of the natural environment. Previous research projects lead by renowned scientist as Prof. Thomas W. Schoener or Prof. Jonathan B. Losos and collaborators provided exciting results about the genesis of biological diversity and set the framework of the present project. For the first time, they explored evolutionary patterns caused by a deliberately introduced species in the Bahamas archipelago. Their research has been focused on the study of the effects of large predators on island food webs, using as an ecological model the system composed of the large lizard Leiocephalus carinatus and the small Anolis sagrei in the Bahamas Archipelago. They have shown that deliberate introductions of the large lizard to small islands caused A. sagrei on experimental islands to shift habitat use, change that comes together with a response on morphological traits to adapt to new microenvironments. Having this exciting background as a point of start, this proposal explored other intriguing questions such as 1) How would natural selection work after a long period of co-occurrence of the large and small species of lizards? Great Abaco contained the answer as it constitutes a present picture of the future of the experimental islands. 2) What would be the direction of evolution and natural selection when both target species are new colonizers? In Florida we searched for the answer, as A. sagrei and L. carinatus, native to the Bahamas (and Cuba), were introduced there in 1940s and 1930s19, respectively. 3) Could previous findings be extrapolated to the evolution and coexistence of other island lizards? The Canary Islands provided a nearly perfect parallel system to investigate this question. There are large-endemic-introduced/small-endemic, as well as giant-endemic/large endemic, lizard interactions that were explored. On the one hand, where giant lizards co-occur with large ones (G. intermedia and G. galloti, respectively; e.g. in Tenerife), it seems that giant lizards exclude large ones and change their morphological traits (large species become smaller). On the other hand, in Fuerteventura, a small endemic lizard (G. atlantica) is being predated upon25 by the large G. stehlini endemic to Gran Canaria, which was introduced into Fuerteventura around 20 years ago, perhaps also altering its morphological/behavioural traits. Another natural replicate exists in Gran Canaria, where a small population of Fuerteventura’s lizard (G. atlantica) was introduced. Despite some field observations, evolutionary effects of these interactions had not yet begun to be explored. As hypothesised, we demonstrated that the evolution evolutionary effects in Great Abaco were intermediate in comparison to those obtained in islands of previous work. Up to date it seems that a general pattern of lizard evolution promoted by predation exists, as it was true in the Bahamas, and it seems that G. stehlini favours on both islands in the Canaries smaller morphotypes of G. atlantica than those in populations excluded from the effects of the large lizard. Our results stressed how interesting environmental issues are to society; thus, it is directed toward improving general understanding of ecological principles that strongly relate to applied research. Our results will contribution to understand mechanisms underlying core principles in the natural sciences and ecology, such as natural selection or evolution. They contribute to the development and evolution of the science of Ecology and will be surely incorporated in the textbooks of the next generations of ecologist of our planet.