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Predictable phenotypic, but not karyotypic, evolution of populations with contrasting initial history

Publication . Simões, Pedro; De mendonça fragata almeida, Inês; Seabra, Sofia G.; Faria, Gonçalo S.; Santos, Marta A.; Rose, Michael R.; Santos, Mauro; Matos, Margarida

The relative impact of selection, chance and history will determine the predictability of evolution. There is a lack of empirical research on this subject, particularly in sexual organisms. Here we use experimental evolution to test the predictability of evolution. We analyse the real-time evolution of Drosophila subobscura populations derived from contrasting European latitudes placed in a novel laboratory environment. Each natural population was sampled twice within a three-year interval. We study evolutionary responses at both phenotypic (life-history, morphological and physiological traits) and karyotypic levels for around 30 generations of laboratory culture. Our results show (1) repeatable historical effects between years in the initial state, at both phenotypic and karyotypic levels; (2) predictable phenotypic evolution with general convergence except for body size; and (3) unpredictable karyotypic evolution. We conclude that the predictability of evolution is contingent on the trait and level of organization, highlighting the importance of studying multiple biological levels with respect to evolutionary patterns.

2017-04Journal article

Open access

Different Genomic Changes Underlie Adaptive Evolution in Populations of Contrasting History

Publication . Seabra, Sofia G; De mendonça fragata almeida, Inês; Antunes, Marta; Faria, Gonçalo S; Santos, MA; Sousa, Vitor C; Simões, Pedro; Matos, Margarida

Experimental evolution is a powerful tool to understand the adaptive potential of populations under environmental change. Here, we study the importance of the historical genetic background in the outcome of evolution at the genome-wide level. Using the natural clinal variation of Drosophila subobscura, we sampled populations from two contrasting latitudes (Adraga, Portugal and Groningen, Netherlands) and introduced them in a new common environment in the laboratory. We characterized the genome-wide temporal changes underlying the evolutionary dynamics of these populations, which had previously shown fast convergence at the phenotypic level, but not at chromosomal inversion frequencies. We found that initially differentiated populations did not converge either at genome-wide level or at candidate SNPs with signs of selection. In contrast, populations from Portugal showed convergence to the control population that derived from the same geographical origin and had been long-established in the laboratory. Candidate SNPs showed a variety of different allele frequency change patterns across generations, indicative of an underlying polygenic basis. We did not detect strong linkage around candidate SNPs, but rather a small but long-ranging effect. In conclusion, we found that history played a major role in genomic variation and evolution, with initially differentiated populations reaching the same adaptive outcome through different genetic routes.

2018-03Journal article

Open access

Beneficial developmental acclimation in reproductive performance under cold but not heat stress

Publication . Simões, Pedro; Santos, Marta A.; Carromeu-Santos, Ana; Quina, Ana S.; Santos, Mauro; Matos, Margarida

Thermal plasticity can help organisms coping with climate change. In this study, we analyse how laboratory populations of the ectotherm species Drosophila subobscura, originally from two distinct latitudes and evolving for several generations in a stable thermal environment (18 °C), respond plastically to new thermal challenges. We measured adult performance (fecundity traits as a fitness proxy) of the experimental populations when exposed to five thermal regimes, three with the same temperature during development and adulthood (15-15 °C, 18-18 °C, 25-25 °C), and two where flies developed at 18 °C and were exposed, during adulthood, to either 15 °C or 25 °C. Here, we test whether (1) flies undergo stress at the two more extreme temperatures; (2) development at a given temperature enhances adult performance at such temperature (i.e. acclimation), and (3) populations with different biogeographical history show plasticity differences. Our findings show (1) an optimal performance at 18 °C only if flies were subjected to the same temperature as juveniles and adults; (2) the occurrence of developmental acclimation at lower temperatures; (3) detrimental effects of higher developmental temperature on adult performance; and (4) a minor impact of historical background on thermal response. Our study indicates that thermal plasticity during development may have a limited role in helping adults cope with warmer - though not colder - temperatures, with a potential negative impact on population persistence under climate change. It also emphasizes the importance of analysing the impact of temperature on all stages of the life cycle to better characterize the thermal limits.

2020-05Journal article

Open access

The role of history, chance and selection during adaptation : an integrated perspective

Publication . Almeida, Inês; Matos, Margarida Maria Demony de Carneiro Pacheco de, 1958-; Santos, Mauro

Understanding the mechanisms and processes that underlie adaptation and which factors affect the evolutionary potential of populations are central themes in Evolutionary Biology. In this thesis I address the issue of how history, chance and selection can affect the adaptation to new environments, integrating several biological levels. For that I characterized the initial differentiation in the new laboratorial environment of three Drosophila subobscura populations, derived from different locations along the European cline for several phenotypic traits, thermal plasticity, chromosomal inversion frequencies, and the association between chromosomal polymorphism and wing traits – the latter expanded to South American populations. Additionally, for the European populations, I followed their real-time evolutionary trajectories during adaptation to a novel, common environment. The main conclusions are that, though history played a prominent role on the initial performance of several phenotypic traits, fast convergence was observed for both adult phenotypic traits and plastic response to non-optimal temperatures. However, convergence did not occur for chromosomal inversion frequencies, as populations remained differentiated even after forty generations of evolution in the common environment. Nevertheless, some inversions presented similar patterns between foundations indicating that selection acted within the boundaries created by history. On the other hand, chance events shaped the association between inversion polymorphisms and wing traits during the colonizing event of South America. These contrasting patterns between European and South American populations are consistent at the continent level. On the other hand, laboratory evolution changed the association between wing size and inversions for the European populations. Summing-up, this thesis shows that history does not constrain phenotypic adaptive evolution, or the plastic thermal response. It also shows that adaptation to a new environment can be attained through different genetic mechanisms. Finally, it suggests that adaptation to a stable environment does not hamper later response to novel environmental challenges.

2015Doctoral thesis

Open access