A large collaboration led by scientists at UCLA and Michigan State University has found that birds produce fewer young if they start breeding too early or late in the season. With climate change resulting in earlier springlike weather, the researchers report, birds have been unable to keep pace.

And, the authors write, the mismatch between the start of spring and birds’ readiness to reproduce is likely to become worse as the world warms, which could have large-scale consequences that would be catastrophic for many bird populations. Birds’ breeding seasons begin whenever the first green plants and flowers appear, which is happening earlier and earlier as the climate warms.

“By the end of the 21st century, spring is likely to arrive about 25 days earlier, with birds breeding only about 6.75 days earlier,” said the study’s first author, Casey Youngflesh, who led the research as a postdoctoral researcher at UCLA and is now a postdoctoral fellow at Michigan State. “Our results suggest that breeding productivity may decrease about 12% for the average songbird species.”

The authors stress that conservation strategies should address bird species’ responses to climate-driven shifts.

Determining if the earlier springs will pose problems for migratory birds has been a major goal of biologists for decades.

“For nearly 30 years, scientists have hypothesized that animals could become mismatched from plants as springs begin earlier,” said Morgan Tingley, a UCLA associate professor of ecology and evolutionary biology and the study’s senior author. “While there have been a few very good case studies of this phenomenon, it has remained a major mystery whether advancing springs will pose a general problem for the majority of species.”

When it comes to raising their young, timing matters for birds. If they breed too early or too late, harsh weather could harm their eggs or newborns. But timing relative to food sources matters too: If birds are looking for food before or after its natural availability, they might not have the resources to keep their young alive.

“Critically, we found evidence for impacts on bird reproduction of both the absolute and the relative timing of birds,” Tingley said.

Using data from a large-scale collaborative bird banding program run by the Institute for Bird Populations, the researchers calculated the timing of breeding and the number of young produced for 41 migratory and resident bird species at 179 sites near forested areas throughout North America between 2001 and 2018.

Then, the authors used satellite imaging to determine when vegetation emerged around each site. They found that each species had an optimal time to breed, and that the number of young produced decreased when spring arrived very early, or when breeding occurred early or late relative to when plants emerged.

While the majority of birds were adversely affected by variations in the start of spring, several species — the northern cardinal, Bewick’s wren and wrentit among them — countered the trend, demonstrating improved breeding productivity when spring began earlier. Those species are mostly non-migratory species that can respond more quickly to the emergence of spring plants that signal the start of the breeding season.

By breeding earlier and without the time constraints imposed by migration, the study noted, non-migratory species may also be able to reproduce more than once per season.

But those species were the exceptions to the rule. Even most non-migratory species couldn’t keep up with earlier spring arrivals. Overall, for every four days earlier that leaves appeared on trees, species bred only about one day earlier.

For migratory species, that discrepancy means that the time between when they arrive at their breeding sites and breeding itself is likely to get shorter as springlike conditions begin earlier. Birds need time to establish territories and prepare physiologically for egg-laying and rearing their young, so that change could cause even greater disturbances to reproduction.

“North America has lost nearly a third of its bird populations since the 1970s,” Tingley said. “While our study demonstrates that the worst impacts of timing mismatch likely won’t occur for several decades yet, we need to focus now on concrete strategies to boost bird populations before climate change takes its toll.”

The study received primary funding from the National Science Foundation and was supported by researchers from the University of Florida; Pennsylvania State University; University of North Carolina, Chapel Hill; and the Institute for Bird Populations.

This transfer of energy through the light-harvesting complex occurs with extremely high efficiency: Nearly every photon of light absorbed generates an electron, a phenomenon known as near-unity quantum efficiency.

A new study from MIT chemists offers a potential explanation for how proteins of the light-harvesting complex, also called the antenna, achieve that high efficiency. For the first time, the researchers were able to measure the energy transfer between light-harvesting proteins, allowing them to discover that the disorganized arrangement of these proteins boosts the efficiency of the energy transduction.

“In order for that antenna to work, you need long-distance energy transduction. Our key finding is that the disordered organization of the light-harvesting proteins enhances the efficiency of that long-distance energy transduction,” says Gabriela Schlau-Cohen, an associate professor of chemistry at MIT and the senior author of the new study.

MIT postdocs Dihao Wang and Dvir Harris and former MIT graduate student Olivia Fiebig PhD ’22 are the lead authors of the paper, which will appear in the Proceedings of the National Academy of Sciences. Jianshu Cao, an MIT professor of chemistry, is also an author of the paper.

Energy capture

For this study, the MIT team focused on purple bacteria, which are often found in oxygen-poor aquatic environments and are commonly used as a model for studies of photosynthetic light-harvesting.

Within these cells, captured photons travel through light-harvesting complexes consisting of proteins and light-absorbing pigments such as chlorophyll. Using ultrafast spectroscopy, a technique that uses extremely short laser pulses to study events that happen on timescales of femtoseconds to nanoseconds, scientists have been able to study how energy moves within a single one of these proteins. However, studying how energy travels between these proteins has proven much more challenging because it requires positioning multiple proteins in a controlled way.

To create an experimental setup where they could measure how energy travels between two proteins, the MIT team designed synthetic nanoscale membranes with a composition similar to those of naturally occurring cell membranes. By controlling the size of these membranes, known as nanodiscs, they were able to control the distance between two proteins embedded within the discs.

For this study, the researchers embedded two versions of the primary light-harvesting protein found in purple bacteria, known as LH2 and LH3, into their nanodiscs. LH2 is the protein that is present during normal light conditions, and LH3 is a variant that is usually expressed only during low light conditions.

Using the cryo-electron microscope at the MIT.nano facility, the researchers could image their membrane-embedded proteins and show that they were positioned at distances similar to those seen in the native membrane. They were also able to measure the distances between the light-harvesting proteins, which were on the scale of 2.5 to 3 nanometers.

Disordered is better

Because LH2 and LH3 absorb slightly different wavelengths of light, it is possible to use ultrafast spectroscopy to observe the energy transfer between them. For proteins spaced closely together, the researchers found that it takes about 6 picoseconds for a photon of energy to travel between them. For proteins farther apart, the transfer takes up to 15 picoseconds.

Faster travel translates to more efficient energy transfer, because the longer the journey takes, the more energy is lost during the transfer.

“When a photon gets absorbed, you only have so long before that energy gets lost through unwanted processes such as nonradiative decay, so the faster it can get converted, the more efficient it will be,” Schlau-Cohen says.

The researchers also found that proteins arranged in a lattice structure showed less efficient energy transfer than proteins that were arranged in randomly organized structures, as they usually are in living cells.

“Ordered organization is actually less efficient than the disordered organization of biology, which we think is really interesting because biology tends to be disordered. This finding tells us that that may not just be an inevitable downside of biology, but organisms may have evolved to take advantage of it,” Schlau-Cohen says.

Now that they have established the ability to measure inter-protein energy transfer, the researchers plan to explore energy transfer between other proteins, such as the transfer between proteins of the antenna to proteins of the reaction center. They also plan to study energy transfer between antenna proteins found in organisms other than purple bacteria, such as green plants.

The research was funded primarily by the U.S. Department of Energy.

Until now, researchers have been unable to model how these deceptively simple tubular structures — called chemical gardens — work and the patterns and rules that govern their formation.

In a paper published this week in the Proceedings of the National Academy of Sciences, Florida State University researchers lay out a model that explains how these structures grow upward, form different shapes and how they go from a flexible, self-healing material to a more brittle one.

“In a materials context, it’s very interesting,” said FSU Professor of Chemistry and Biochemistry Oliver Steinbock. “They don’t grow like crystals. A crystal has nice sharp corners and grows atom layer by atom layer. And when a hole occurs in a chemical garden, it’s self-healing. These are really early steps in learning how to make materials that can reconfigure and repair themselves.”

Typically, chemical gardens form when metal salt particles are put in a silicate solution. The dissolving salt reacts with the solution to create a semipermeable membrane that ejects upward in the solution, creating a biological-looking structure, similar to coral.

Scientists observed chemical gardens for the first time in 1646 and for years have been fascinated with their interesting formations. The chemistry is related to the formation of hydrothermal vents and the corrosion of steel surfaces where insoluble tubes can form.

“People realized these were peculiar things,” Steinbock said. “They have a very long history in chemistry. It became more like a demonstration experiment, but in the past 10-20 years, scientists became interested in them again.”

Inspiration for the mathematical model developed by Steinbock, along with postdoctoral researcher Bruno Batista and graduate student Amari Morris, came from experiments that steadily injected a salt solution into a larger volume of silicate solution between two horizontal plates. These showed distinct growth modes and that the material starts off as stretchy, but as it ages, the material becomes more rigid and tends to break.

The confinement between two layers allowed the researchers to simulate a number of different shape patterns, some looking like flowers, hair, spirals and worms.

In their model, the researchers described how these patterns emerge over the course of the chemical garden’s development. Salt solutions can vary a lot in chemical makeup, but their model explains the universality in formation.

For example, the patterns can consist of loose particles, folded membranes, or self-extending filaments. The model also validated observations that fresh membranes expand in response to microbreaches, demonstrating the material’s self-healing capabilities.

“The good thing we got is we got into the essence of what is needed to describe the shape and growth of chemical gardens,” Batista said.