We study the processes that generate biodiversity and in particular how speciation, extinction, dispersal, phenotypic evolution, and ecology interplay over time and space during the diversification process. Our research focuses on birds as models. We analyze molecular, phenotypic, and environmental data using phylogenetic and comparative methods to study the tempo and mode of bird evolution. Our work is highly integrative and aims for the unification of evolution and ecology.
The following are the main topics of our research:
Phylogenetics and Systematics of Birds
Accurate time-scaled phylogenies that include all species are fundamental for studying evolutionary diversification. We focus on phylogenetics, divergence-time estimation, and species delimitation. One of our projects is a time-calibrated phylogeny of all species of the passerine family Furnariidae (Neotropical ovenbirds and woodcreepers). The Furnariidae is one of the most spectacular of avian radiations, not only very diverse in species (nearly 300, the fourth-largest avian family in the Americas) but also highly diverse in ecomorphological adaptations and specializations. The furnariid tree is currently one of the most complete phylogenies for any vertebrate group of similar diversity and offers a unique opportunity for comparative studies of macroevolution and diversification. We are now working on a new tree that will be more accurate and complete.
We are also working on establishing a more accurate time framework for the evolution of modern birds (Neornithes). Determining the timing of avian evolution has been elusive due to the discrepancy between the fossil record and molecular divergence estimates (the old ‘rocks’ versus ‘clocks’ controversy). We are exploring new strategies for calibrating molecular clocks and obtain more accurate estimates for the age of birds. Santiago is also a member of the South American Classification Committee of the American Ornithological Society.
Processes that Drive Diversification
We are interested in elucidating both extrinsic (i.e. Earth’s history) and intrinsic (species traits) factors that can influence the diversification process.
Ecological opportunity – It has been hypothesized that evolutionary innovations that create ecological opportunity can stimulate diversification. We are exploring the existence of ‘key innovations’ in the Furnariidae, like the evolution of climbing adaptations that put some furnariid lineages into a new adaptive zone (trunk foraging, Claramunt et al. 2012). Other traits that we are investigating include adaptations for locomotion in entangled vegetation, nest architecture, and vocal evolution (Derryberry et al. 2012, 2018).
Dispersal – Dispersal is a fundamental process in ecology and evolution; yet, it has resisted investigation at macroecological and macroevolutionary scales because it is extremely difficult to quantify. We are investigating ways of estimating the dispersal capabilities of birds based on their flight morphology and then use that information to investigate how dispersal influences the diversification process at macroevolutionary scales.
Earth’s history – Biogeographic reconstructions are important for establishing the geographic setting of past diversification events. We use a combination of time-scaled phylogenies and ancestral biogeographic reconstructions to correlate diversification events with events in Earth’s history. For example, we recently found that modern birds originated in the southern hemisphere and their dispersal around the world is consistent with what we know about continental connections during the Cenozoic (Claramunt & Cracraft 2015). In the same article, we revealed a striking pattern in which net diversification rates of modern birds are negatively correlated with global temperatures: Periods of rapid diversification coincide with long-term trends of planetary cooling. We interpreted this as the effect of tropical biome retraction and fragmentation (Claramunt & Cracraft 2015), and are now documenting this pattern in more detail and investigating its causes.
Birds of Uruguay
Uruguay is Santiago’s homeland and where he developed his early career as an ornithologist. He is involved in studies of diversity, distribution, and conservation of Uruguayan birds. He is the Uruguay country list coordinator of the AOU South American Classification Committee and author and illustrator of the guide of the birds of Montevideo city (see online edition).