The 2010 American Society of Naturalists Presidential Award-winning research reveals how climate change drives evolutionary diversification
Each year, the American Society of Naturalists (ASN) bestows honors upon research that exemplifies its mission: the conceptual unification of the biological sciences 4 . In 2010, the prestigious ASN Presidential Award was given to a paper that did just that, masterfully weaving together threads from evolutionary biology, ecology, and climate science 4 .
The winning paper, "Climate, Niche Evolution, and Diversification of the 'Bird-Cage' Evening Primroses," was authored by Margaret E. K. Evans, Stephen A. Smith, Rachel S. Flynn, and Michael J. Donoghue 4 . This study stands as a powerful example of how asking deep questions about the natural world requires a synthesis of different scientific fields, revealing the interconnectedness of life's history.
The research tackles a fundamental question in biology: what drives the evolution of new species? For the beautiful and enigmatic "bird-cage" evening primroses (sections Anogra and Kleinia), Evans and her team proposed that the answer lies in a dynamic interplay between climate shifts, ecological niches, and evolutionary processes over millions of years. By building a "family tree" of these plants and comparing it to past climate data, they opened a window into how environmental changes have shaped the journey of life on Earth.
Awarded for outstanding research that unifies biological concepts across disciplines
To appreciate the significance of this research, it's helpful to understand a few core concepts.
More than just an organism's address; it's its profession. A niche encompasses all the environmental conditions that a species needs to survive and reproduce. The concept of "niche conservatism" is central to this study.
A representation of the evolutionary history and relationships among a group of organisms, much like a family tree. It shows how species have branched off from common ancestors.
The study of past climates. Scientists use various proxies, such as ice cores or geological data, to reconstruct what the Earth's climate was like millions of years ago.
The brilliant synthesis in the award-winning paper lies in connecting these three fields. The researchers asked: If niche conservatism is a powerful force, then major shifts in the Earth's climate in the past should have forced species to either move to track their preferred climate, face extinction, or adapt. This "push" from climate change could have been a key driver in splitting ancestral species into new, distinct lineages, a process known as allopatric speciation.
The research team embarked on a comprehensive investigation to test the hypothesis that climate change was a primary driver of diversification in the evening primrose group.
The first step was to reconstruct a robust phylogeny of the evening primroses. The team extracted and sequenced DNA from numerous species. Using computational tools, they analyzed the genetic similarities and differences to determine how the species are related and to estimate the times when different lineages split from one another 4 .
For each existing species, the researchers determined its modern ecological niche by mapping its geographical distribution and overlaying data on climate variables like temperature and precipitation.
Using the phylogenetic tree and the modern niche data, the team employed statistical models to infer the most likely climatic conditions in which the ancestral evening primroses lived millions of years ago.
This was the critical test. The researchers compared their reconstructed evolutionary history of niches with independent data on historical global climate changes. They looked for correlations between periods of significant climate shift and periods of rapid diversification in the evening primrose lineage.
| Tool / Material | Function in the Research |
|---|---|
| DNA Sequencer | Determined the precise order of nucleotides in the genetic code of different species |
| Computational Phylogenetic Software | Analyzed genetic sequence data to infer evolutionary relationships |
| Climate Database | Provided high-resolution global data layers for bioclimatic variables |
| Statistical Modeling Programs | Used to perform complex analyses and test correlations |
The analysis yielded compelling results. The phylogeny showed that the evening primroses underwent significant periods of diversification, and these bursts of speciation corresponded strongly with major shifts in the Earth's climate, particularly during the Miocene and Pliocene epochs (approximately 23 to 2.5 million years ago) 4 . As global climates became cooler and drier, the ancestral populations of evening primroses likely became fragmented and isolated in areas that still met their specific climatic needs.
This finding strongly supports the role of niche conservatism. Instead of quickly adapting to the new, widespread conditions, the plants' climatic preferences remained stable. This forced them to migrate or become restricted to "refugia"—pockets of suitable habitat. The geographical isolation that resulted from this process then allowed the separated populations to evolve independently, eventually giving rise to new species. The study concluded that climate change was not just a backdrop but a central character in the evolutionary story of the evening primroses.
| Geological Epoch | Time Period (Approx. Million Years Ago) | Global Climate Trend | Evolutionary Event in Evening Primroses |
|---|---|---|---|
| Miocene | 23 - 5.3 | Global cooling and drying; spread of grasslands | Major initial diversification and lineage splitting |
| Pliocene | 5.3 - 2.6 | Continued cooling; increased seasonality | Further speciation and diversification within the group |
| Pleistocene | 2.6 - 0.01 | Ice Ages with glacial-interglacial cycles | Distribution shifts and potential further isolation |
The 2010 ASN Presidential Award-winning study by Evans et al. is more than just a deep dive into the history of a single group of plants. It is a testament to the power of integrative science. By refusing to let the boundaries of genetics, ecology, and paleontology limit their inquiry, the researchers provided a compelling narrative of how planetary forces shape biodiversity.
Their work on the evening primrose offers a framework that can be applied to other groups of organisms, helping us understand the origins of the planet's rich biological tapestry. In a modern era of rapid, human-induced climate change, this research also carries a poignant message. It illuminates the profound and fundamental relationship between climate and life, reminding us that the climate shifts we cause today will inevitably write the next chapters in the evolutionary story of countless species.