Chillier Winters, Smaller Beaks

This honeyeater (Melidectes belfordi) lives in the montane forests of New Guinea. Photo credit: Charles Davies; Flickr. This photo was cropped from the original version.

(Article provided by the OIST media section)

Although Charles Darwin lived and worked in the 19th century, modern evolutionary biologists are far from exhausting all avenues of inquiry regarding birds and evolution. For example, in the 1990s, researchers such as Russ Greenberg, ornithologist from the Smithsonian Institution in the United States, began to explore a new question concerning the relationship between climate and the evolution of beak size. This question was inspired by Allen’s Rule, which states that warm-blooded animals living in cold climates will have shorter limbs and appendages than those that live in warmer climates. The biological mechanism behind this rule is thermoregulation—more body surface area helps animals to shed heat better whereas less surface area helps them to conserve it. Since a bird’s beak plays a large role in thermoregulation—it has lots of blood vessels and is not covered in feathers—researchers wondered whether hotter climates beget larger beaks and colder climates beget smaller ones. Indeed, studies revealed that climate has influenced beak size, but not which type of climate had more of an overall impact.

Past research left a question open at the end: “Which of these functions is under selection?” Dr. Nicholas Ryan Friedman, a researcher from the Biodiversity and Biocomplexity Unit at the Okinawa Institute of Science and Technology Graduate University (OIST), comments. “Are birds with small beaks dying in the summer because they get too hot? Or are birds with large beaks dying in the winter because they get too cold?” In collaboration with scientists in the Czech Republic, Dr. Friedman designed a study to explore this question and ultimately found that winter, not summer, had more of an impact. The study is published the journal Evolution.

Dr. Friedman and colleagues chose to tackle the question by recording variations in beak size in Australasian honeyeaters and allies. What makes this group of birds a great subject for this study is that the region they inhabit, Australia, New Guinea, and the South Pacific, exhibits huge variation in climate and temperature—from the tropical forests of New Guinea, to central Australia’s arid deserts, to the temperate forests of Tasmania. This means that it is possible to compare differences between individuals of the same species that are living in wildly different conditions.

After measuring the beaks from 158 different species using specimens from the Australian National Wildlife Collection and comparing beak sizes to climate, the researchers found no correlation with summer temperatures but a clear one for winter—the coldest winters were associated with the smallest beaks, whereas warmer winters were associated with larger beaks.

The top graph shows a correlation between beak size and winter minimum temperatures, with the smallest beaks relating to the coldest winters. The bottom graph shows no clear correlation for summer maximum temperatures.

Before Dr. Friedman and colleagues reported this new environmental pressure on beak size, winter temperatures, feeding habits were believed to be the greatest driving force in beak evolution. For example, since the 1970s, Peter and Rosemary Grant, the famous duo who measured the process of evolution in real-time in the Galapagos, have been studying how beak size can change due to food availability over a short period.

“Which is exciting!” Dr. Friedman comments. “But it’s not yet clear from that whether adaptation to improve feeding efficiency is the only, or even the most important, factor in driving beak evolution across millions of years.”

What is unique about Dr. Friedman and colleagues’ study is that it allowed for a peek into an unusually broad evolutionary timeframe. By comparing many different species of birds, the researchers were able to delve into a very distant past and discover the morphological importance of winter temperatures. The next step would be to better understand the relationship between these two factors—feeding efficiency and winter temperatures—in the overall narrative of beak evolution.

The Helmeted Friarbird (Philemon buceroides), a member of the honeyeaters, lives in Northern Australia and New Guinea. Photo credit: Jim Bendon; Flickr.

By Anne McGovern (

The dragon ant makes it into the Top10 New Species of 2017

Pheidole drogon major worker

Since 2008, the International Institute for Species Exploration in New York, USA publishes an annual Top 10 list of the new species discovered the past year. The annual list is released around May 23 to honor of the birthday of Carl Linnaeus, also known as the Father of Taxonomy.

Amidst a rat, a worm, a stingray, two plants and other arthropods, the dragon ant Pheidole drogon that was described last year by researchers in our lab made the cut to the 2017 Top 10.

Along with Pheidole viserion, Pheidole drogon – found in Papua New Guinea – owes its name to the dragon in the famed Game of Thrones book and TV series. The idea was inspired from the large spines on the back of the ant, which is revealed to be a location for muscle attachment to allow great strength in the head and mandibles.

The 2017 list of nominees also includes the bleeding ‘Bloodybone’ bush tomato, the spider Eriovixia gryffindori resembling the ‘Sorting Hat’ in the Harry Potter series, an amphibious centipede, a marine worm that look like a churro fried pastry, a South American plant which flower looks like a “Devil head”, a large spotted freshwater stingray, a millipede that continuously adds extra limbs throughout its lifetime, a vegetable-eating rat and finally a leaf-like katydid.

The institute’s international committee of taxonomists selects the Top 10 from among the approximately 18,000 new species named the previous year.

Pheidole drogon minor worker

Written by the OIST Media Section, edited by Julia Janicki.

New paper published: Patterns and processes in mountain ant metacommunities

Understanding the drivers of biodiversity patterns is always difficult due to the fact that multiple factors such as environmental gradient and spatial connectivity might contribute to the species distribution and community composition patterns simultaneously.

In a new paper just published in Ecography, we (Liu, Dudley, Xu and Economo) evaluate the effects of environmental gradients and spatial connectivity on ant taxonomic and phylogenetic diversity patterns along a 5000m elevational gradient within a complex mountainous landscape in Hengduan Mountains, a biodiversity hotspot in Southwest China.

We found that environmental gradients dominate variation in both alpha and beta diversity in this landscape, with alpha diversity strongly declining with elevation and beta diversity driven by elevational differences. We compared our system to predictions of a recent theoretical framework (Bertuzzo et al. 2016; PNAS) which synthesizes how aspects of landscape geomorphology may drive biodiversity patterns in idealized mountain landscapes. Our findings did not match the theory, we found alpha diversity is monotonically declining and within-band beta diversity is invariant with increasing elevation, but point toward ways to improve the theory. Taken together, our results show how elevation-driven environmental gradients, spatial factors, as well as landscape geomorphology together affect ant metacommunity structure in a complex mountainous landscape.

Original paper can be found here

New paper published: Potentials of micro CT for ant taxonomy

In the paper we explore the potential of x-ray micro computed tomography (μCT) for the field of ant taxonomy and use it intensively for the descriptions of two remarkable new species of the genus Terataner from Madagascar. In addition to the traditional way of presenting new species with stacked montage light photography, we also provide 3D models based on μCT data and make the whole 3D datasets available online through Dryad.

One important aspect of the study is to assess how μCT can improve collections-based research of ants and other insects. Our μCT-based 3D models can be virtually rotated, sectioned, measured, and dissected, thus allowing a wide range of analyses of the anatomy and morphology of the studied organisms. By generating and presenting virtual 3D models of ants (or other animals) we support the establishment of virtual natural history collections that permit rapid and free access to anatomically correct and permanent digital reconstructions or avatars of physical specimens. Another great advantage is of the technology is the ability to print physical models of the scanned specimens, which can be used for a variety of research, museum, educational, and outreach purposes.

OIST Science Challenge 2017: Measuring Biodiversity

OIST Science Challenge 2017 was put together by the Graduate School over five days (3/6-3/10) to allow Japanese undergraduate students to explore their careers as scientists and researchers. The students were involved in hands-on activities set up by different labs in order to learn about the research conducted at OIST as well as learn experimental and research methods.

Arilab hosted a an activity based around measuring biodiversity. Our “measuring biodiversity” activity is the most popular one this year, with 12 students signing up. The goal of the activity is for students to apply concepts of biodiversity to a tangible challenge: designing a one-hour project to quantify the diversity of insects in a petri dish. After this activity, students should critique their success and use this experience to design future project ideas. The material used in this activity is provided by the OKEON Churamori Project.