Name: Ferreira DS

Biodeserts supervisor: Santos X

Co-supervisor: Pinho C

Title: Genetic and morphological impacts of a repeated fire regime on Podarcis guadarramae

Institution: University of Porto

Status: Completed



Wildfires have played a determining role in shaping the evolution and functioning of many ecosystems around the world. Over the past three centuries, human population density and distribution have increased exponentially which intensified the human influence on fire number and impact. In Portugal, the northern part of the country has the highest fire frequency of Europe. Fires have both direct and indirect effects on individual organisms. Direct effects result from the fire itself causing emigration and/or mortality. Indirect effects result from shifts in the habitat structure and resource availability (e.g. food, shelter, etc.), and also modification of the landscape structure by creating a mosaics of fragmented habitats affected in different levels by fire (from unburnt to burnt habitats). Biological processes such as mortality, survival and post-fire recolonization can affect the genetic diversity in contrasting ways: reductions in heterozygosity and allelic richness as a result of population bottleneck; increases in genetic diversity and reduced regional genetic differentiation as a result of a high immigration rate; and the intermediate value of unchanged genetic diversity when mortality is low or is compensated by immigration. Apart from the genetic component of the individual, fires also can have effects on the morphology by imposing an environmental stress during the development of animals. When organisms fail to buffer such disturbances, it may display signs of development instability. Such differences in stability between populations have led to the widespread use of developmental stability analysis as a technique for identifying and characterizing populations subject to systematic stress. The objective of this work is to assess how a repeated fire regime affects the genetic diversity and morphology of Podarcis guadarramae populations in northern Portugal. We did a pairwise sampling scheme in five replicate locations that are composed by two populations of different conditions: unburnt and burnt populations. We sampled burnt populations with different number of fires and time since fire in order to have a gradient of populations with different fire histories. We want to test how fire change genetic diversity, population differentiation and genetic structure. We expect that fire impose bottlnecks in populations, therefore decreasing allelic diversity and heterogeneity and further affected by genetic drift. We expect that fire also influence the genetic differentation and genetic structure due to the changes that fire can produce on populations. We performed several analysis to test our hypothesis, from standard to genetic indices (e.g. mean number of alleles, observed and expected heterozygosity) to correlation of those genetic indices with fire history and geographic distances. To analyse the population structure we performed FST, AMOVA, PCoA and Structure. We aimed also to detteck recent bottlenecks and calculate the effective population size. At the morphological level we tested for developmental stability by measuring fluctuating asymmetry in populations and further correlated it heterozygosity. Our results show that fire increased genetic diversity in burnt populations, contrarily of what expected. Also only populations show low differentiation and weak genetic structure. We suggest that these patterns are due to survival and immigration from outside the fire boundire. We further suggest that these observed patterns point to a metapopulation dynamic in Podarcis guadarramae. As for the morphological impact of fire, we observed the expected pattern of burnt populations having higher asymmetry degree most likely due to the environmental stress imposed by the fires. Furthermore, the heterozygosity was not correlated with the degree of asymmetry. One of the possible consequences of morphology asymmetry is the lower fitness such as lower locomotor performance that in turn can increase exposure to predators. We conclude that although some of our hypothesis were not corroborated, our results give new insights of demographic processes behind post-fire responses of lizards.