Time passes better when you ask questions

Robert Silverberg

Many of my research questions are derived from observations made during fieldwork. My research mostly aims at understanding taxonomic and genetic diversity, evolutionary patterns (and the processes that produce them), and diversification through time and space, using amphibians and reptiles as my main models. My current research projects predominantly focus on the Pantepui region in northern South America where I study the biogeography, population genomics, physiologypopulation dynamics and spatial ecology of amphibians and reptiles in highly fragmented landscapes. I am also conducting collections-based research revising the systematics of several Guiana Shield amphibian and reptile taxa.

Like many scientists, my life has been greatly influenced by the reading of adventurers’ stories while I was a child, dreaming of exploration and discovery of unknown fabulous animals in untouched places and impressive landscapes. What would be more exciting than being an explorer describing species previously unknown to science? That dream partly became a reality and I feel fortunate to have been able to explore the “fairy worlds” of my childhood and describe some previously unknown taxa.

I try to spend as much time as possible in the field, first to collect samples for my research projects, but also because I like to understand the natural history of the organisms I am studying (i.e. observing them alive interacting with their environment), not only working with tissue samples, pipettes, sequencing machines and computer programs. Another – I confess major – reason is that I just like to be in the field, camping in my tent or hammock and living a simple life surrounded by the wilderness, far from the tumult and craziness of the human world.

Since 2007 my main research project focus on the tepui ecosystem in northern South America where I am trying to disentangle the processes behind the evolution of organisms in these “islands in the sky”. I am also working on phylogenies and taxonomic revisions of several taxa inhabiting this outstanding area. The tepuis are the impressive abrupt-sided table mountains that arise above the savannah and tropical forest mainly in southern Venezuela, west-central Guyana, and Brazil. The iconic, unreachable and mysterious table mountains can reach 3km elevation and have up to 1000m vertical cliffs. These behemoths, most having been visited less than the moon, are erosional remnants of extremely old (Precambrian) sandstone sediments that were uplifted and subsequently eroded by tectonic forces, wind and weathering during millions of years. 

In 1912, Sir Arthur Conan Doyle, largely inspired by the tepui geomorphology [and by the account of an expedition of the Royal Geographical Society of London on the summit of Mount Roraima (led in 1884 by Sir Everard im Thurn)], published one of his most famous novels “The Lost World”, which stirred numerous fiction movies. In Doyle’s novel a tepui summit harbours dinosaurs and a forgotten civilisation living isolated for millions of years. Because of their age and isolation, scientists have long believed – like Conan Doyle – that the table mountains mostly harbour old endemic lineages, some possibly contemporary to the dinosaurs and predating the separation of Africa and South America. Actually, Doyle book’s topic remains an evolutionary enigma: how and when did the tepuis summit fauna diversify?

My collaborators and I partly solved this enigma, and our results not only contradicted the traditional view of relict tepui lineages living in long isolation, but could also challenged the age of the dissection in individual tepuis, which until now was generally supposed to date back to the Cretaceous (70 to 100 million years ago), when dinosaurs still roamed the earth. Studying the DNA of numerous specimens belonging to six groups of amphibians and reptiles from 17 tepuis/tepui massifs, my collaborators and I found that instead of being old and distantly related, most tepui tops populations are “young” and closely related to each other or to populations from the surrounding uplands. This sharply contrasts with the many recent discoveries of huge cryptic diversity in other regions that have much less dramatic landscapes. Interestingly, even species or populations living in very specific habitats found only on the highest and most isolated tepui summits (thus not in the intervening uplands) are often unexpectedly closely related. Because amphibians and reptiles (especially those ecologically specialized taxa) likely have limited dispersal abilities, this observation questions the exact age of fragmentation of some currently isolated tepuis, which could be more recent than usually supposed. Estimation of divergence time indicates that many summit populations were in contact as recent as during the late Pleistocene-Holocene (less than 1.8 million years ago), thus challenging the “Lost World” romantic preconception that probably biased scientists’ mind for many years. 

We expanded our dataset and now have gathered information from more than 20 tepui summits in the Eastern Pantepui District, which is probably the largest dataset ever compiled in the area (at least for vertebrates).

I am currently working on population genomics that will be merged with our recent systems-level ecological studies into ecological genomics.

Getting closer to completely unlock the secrets of the “Lost World”!

Some new taxa described

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