Evolutionay demography of the Balearic Wall lizard (Podarcis lilfordi) = La demografia evolutiva de la Sargantana Balear (Podarcis lilfordi)

Abstract

Many topics in ecology and evolution are currently being studied under the framework of eco- evolutionary dynamics that is to say integrating genetic, ecological and demographic data. Here, I have focused my investigations on three neighbouring isolated populations of this species, the Balearic Wall lizards, also known as Lilord’s lizard. The three populations chosen are from the southern coast of Mallorca Island (Balearic Islands, Spain) belong to the same genetic clade and derived from the same recent colonization event. Therefore, I investigate life-history adaptations of this endemic species inhabiting on small islets where immigration and emigration are constraint. Using ‘soft’ comparative methods to assess the relative contribution of ecological, environmental, and evolutionary processes that govern the dynamic of these three populations, I tried to shed light on the selective pressures imposed by the insular environment and the consequences of individual responses on the evolution of life- history traits. Throughout this thesis I used techniques and concepts of ecology, allometric and genetic to develop an integrated population model that provides a new analytical framework to address eco-evolutionary questions and that unifies the ecological and genetic approaches in a demographic context. However, firstly I had to solve problems linked with the monitoring methods and in particular the imperfect sampling of natural populations. Indeed, animals might die, breed or move undetected. To solve this problem it is necessary to use statistical models to infer the biological processes or to obtain unbiased estimate of the demographic parameters from the raw observations. Then, I moved to the study of ecological predictors of body growth using individual-based data, lizards are considered animals of continuous growth and not surprisingly the growth rate is an important life-history parameter with inter-specific and inter-population differences. A problem linked with the estimate of growth parameters in wildlife populations is that individual age is often unknown. I used individual-based data to assess the length-at-age curve from capture–recapture data of uniquely identified and sexed individuals. Once the length-at-age relationship was described, I describe the influence of predictors of body growth. I further investigated the inter- and intra-population genetic structure to describe the genetic architecture of each populations and their relationship. Furthermore, I analysed patterns of divergence among the three populations not only using genetic markers, but also comparing lizards’ life-history traits such as body size, individual growth rate, fecundity, and survival probability. Finally, I merged all these results into an integral projection model (IPM) in which all demographic parameters were describes as a function of lizards’ body size to develop an analytical framework to address eco-evolutionary questions. IPM results were used to make predictions of the demographic consequences of body size and age variations.

Molts de temes en el camp de l'ecologia i la evolució estan íntimament lligats, avui dia molts d'estudis es fan de manera conjunta. Malgrat això, l'estudi de les dinàmiques eco-evolutives de poblacions naturals es molt complexa i requereix de molta informació ja que integra tant dades genètiques, com ecològiques i demogràfiques. Utilitzant un gran nombre de dades individuals, l'objectiu principal d'aquesta tesi ha estat la de posar de manifest les pressions selectives imposades per l'entorn insular de poblacions de sargantana balear (Podarcis lilfordi), tres poblacions aïllades veïnes d'aquesta espècie procedent de la costa sud de l'illa de Mallorca van ser triades per estudiar les conseqüències de les respostes individuals en l'evolució dels trets d'història de vida. Al llarg d'aquesta tesi he fet servir tècniques i conceptes de l'ecologia, genètica i morfologia per desenvolupar un model de població integrat que proporcioni un nou marc analític per abordar qüestions sobre dinàmiques eco-evolutives i que unifica els enfocaments ecològics i genètics en un context demogràfic.