Evolutionary lag times and recent origin of the biota of an ancient desert (Atacama–Sechura)

Abstract

The assembly of regional biotas and organismal responses to anthropogenic climate change both depend on the capacity of organisms to adapt to novel ecological conditions. Here we demonstrate the concept of evolutionary lag time, the time between when a climatic regime or habitat develops in a region and when it is colonized by a given clade. We analyzed the time of colonization of four clades (three plant genera and one lizard genus) into the Atacama-Sechura Desert of South America, one of Earth's driest and oldest deserts. We reconstructed time-calibrated phylogenies for each clade and analyzed the timing of shifts in climatic distributions and biogeography and compared these estimates to independent geological estimates of the time of origin of these deserts. Chaetanthera and Malesherbia (plants) and Liolaemus (animal) invaded arid regions of the Atacama-Sechura Desert in the last 10 million years, some 20 million years after the initial onset of aridity in the region. There are also major lag times between when these clades colonized the region and when they invaded arid habitats within the region (typically 4-14 million years). Similarly, hyperarid climates developed ∼8 million years ago, but the most diverse plant clade in these habitats (Nolana) only colonized them ∼2 million years ago. Similar evolutionary lag times may occur in other organisms and habitats, but these results are important in suggesting that many lineages may require very long time scales to adapt to modern desertification and climatic change.niche conservatism | niche evolution | biodiversity | evolutionary biogeography N atural selection can be a rapid and powerful force and is essential for allowing organisms to invade new habitats and to persist during environmental change (1, 2). However, natural selection is not without limits (e.g., ref.3), and these limits may have important implications. Many ecological and evolutionary patterns are related to the inability of species to adapt to novel climatic conditions (climatic niche conservatism), including patterns of biogeography, species richness, allopatric speciation, and introduced species invasion (4-7). Despite initial niche conservatism, many clades eventually are able to colonize novel environments. Thus, niche conservatism may also be quantified based on the length of time it takes to adapt to and invade novel ecological conditions. However, little is known about the time scales required for successful colonization in these cases.Here, we focus on this "evolutionary lag time," the time lag between the emergence of novel environmental conditions in a region and when that habitat is colonized by a given clade. We illustrate this concept in the contiguous Atacama and Sechura deserts of South America (Atacama-Sechura Desert hereafter). This desert represents one of the harshest and driest environments on Earth (8-10), but nevertheless contains many endemic plant and animal species (11)(12)(13)(14). We compare the time of origin of different precipitation regimes within the region (bas...

Microbial Activity Response to Solar Radiation across Contrasting Environmental Conditions in Salar de Huasco, Northern Chilean Altiplano

“…BSP responses (inhibition or enhancement) under short-term solar exposure cannot be only related to light exposure history, but also to some other extreme conditions (Rothschild and Mancinelli, 2001; Triadó-Margarit and Casamayor, 2012; Guerrero et al, 2013; Li et al, 2014). The irradiance conditions experienced by isolated pond communities in our experiments were in combination with other potentially limiting conditions.…”

“…In addition, high altitude saline wetlands from the Andean Altiplano present contrasting mineral composition at small spatial scales (Acosta and Custodio, 2008; Risacher and Fritz, 2009; Uribe et al, 2015) that range from freshwater to hypersaline conditions, as well as from limiting to high nutrient concentrations (Dorador et al, 2008b, 2010). While biodiversity of higher trophic levels is low in extreme environments (Guerrero et al, 2013), there is evidence that lakes located above 2000 m (e.g., Tibet, Pyrenean, or Andean lakes) hold a large microbial diversity (Wang et al, 2011; Triadó-Margarit and Casamayor, 2012; Albarracín et al, 2015a,b) in association with environmental heterogeneity.…”

Efectos sobre la flora y vegetación del evento de precipitación extremo de agosto 2015 en Alto Patache, Desierto de Atacama, Chile

“…En este ambiente se desarrolla una gran diversidad vegetacional, con presencia de distintas formaciones vegetacionales, como Herbazales, Matorrales y Bosques (Luebert & Pliscoff , 2017) y un alto número de especies de flora endémica, la cual ha sido, en general, muy poco reconocida (Luebert, 2011;Guerrero et al, 2013;Manrique et al, 2014;Larridon et al, 2015). Estas características de los ecosistemas del Desierto de Atacama se pueden explicar por una gran heterogeneidad ambiental, producto de una activa historia paleo ambiental y de evolución del paisaje (Latorre et al, 2015;Latorre et al, 2013).…”

Conservation network design for endemic cacti under taxonomic uncertainty

“…These areas are distinguished by not only high levels of endemism in their flora and fauna but also a high rate of landscape modification and are considered a global biodiversity hotspot priority for conservation (Myers et al, 2000). Atacama Desert and Mediterranean central Chile configure an arid gradient where arid adapted lineages have diversified (Guerrero et al, 2013;Jara-Arancio et al, 2014), and harbors all of the diversity of Chilean endemic cacti, including notable examples of species with extremely restricted geographic ranges (Ortega-Baes and Godinez-Alvarez, 2006). We decided to work with endemic cacti because other non-endemic species are distributed in border areas but occur only sparsely in Chile, in contrast to their geographic representation in neighboring countries.…”