Determinantes ecológicos de processos macro e microevolutivos em regiões complexas

Abstract

Mountain areas around the world cover less than 15% of global land surface; nevertheless, they concentrate around 90% of the hotspots of species diversity and 40% of the hotspots of endemism. Available evidence suggest that ecological factors such as landscape features (i.e topographic complexity, climatic heterogeneity and their historical dynamics) of mountains may play an important role in the evolution and maintenance of rich biotas at such regions. In my dissertation I aim to evaluate the role of such factors in both macro (i.e global speciation patterns) and microevolutionary (i.e intra-specific genetic and trait divergence) processes using amphibians as study system. In the first chapter, we tested in a global scale the Montane Pumps hypothesis, which proposes that speciation rates are faster in mountains explaining higher diversities in those regions. To this end we used a near complete Amphibian phylogeny containing 7238 species (>90% of the group’s extant diversity) and conducted a Bayesian Analysis in Macroevolutionary Admixtures (BAMM) to estimate speciation rates. Then we combined this information with available range maps to explore Amphibian geographic patterns of speciation and evaluated its association with complex terrains (mountains) by estimating a global index of topographic complexity. We found that globally, speciation rates are faster in regions of high topographic complexity independently of latitude. We repeated our analyses using the Wallace’s Zoogeographic regions, taking into account regional independent evolutionary histories, and found the same pattern in eight out of the total 11 zoogeographical realms. In a second chapter, we assess the relative role of different components of the landscape in promoting lineage diversification across the roughed topography of Isthmian Central America (Costa Rica & Panama), a geologically young but highly biodiverse region. Here we use available mitochondrial DNA to estimate genetic divergence within 10 amphibian species (8 anurans and 2 salamanders) with different biologies that co-occur in the region. Then, we use a Multiple Matrix of Regression with Randomization to assess the relative role of isolation by distance, by environment and by resistance (topography, current climate, and LGM paleoclimate) in shaping the geographic patterns of genetic structuration within each species. So far, we have not found a general force that explains genetic divergence in all studied species. Instead, we have found idiosyncratic responses that may reflect specific aspects of their life histories, such as dispersal capabilities, range size or reproductive potential. In the third chapter, we test how climatic and topographic barriers may influence variation in an important behavioral trait such as are advertisement calls. In anurans, such calls has species-specific features that play an important role in recognition. Then, variation in spectro-temporal features between populations has been proposed as a mechanism of reproductive isolation that may promote speciation in the long term. For this chapter I recorded advertisement calls of 170 males from 2 species of Diasporus frogs distributed in Costa Rica. I made recordings at 21 sites in all the country ranging from sea level to 2800 meters elevation. We use such information we conduct bioacoustics analyses to first document geographic variation and then test if the geographic distance, physical or ecological barriers between populations, or adaptation to local conditions could shape such patterns. To this end, we incorporate spatial analyses (niche models, terrain roughness estimations and circuit theory) to generate levels of population isolation and apply Generalized Dissimilarity Matrix test to address this question. In both species, I found high levels of acoustic variation and among population isolation derived by the tested factors. However, only topography significantly explained acoustic divergence in D. diastema while climatic dissimilarity and geographic distance are only marginally associated with the patters of acoustic variation in D. hylaeformis. In conclusion, other forces operating independently in the local scale -such as sexual selection, character displacement or genetic drift- may be more determinant in the evolution of acoustic signals in these species