If you look hard enough in the field, you are guaranteed to uncover cool stuff. Such is the case in Madagascar, where Brian Fisher and colleagues have been surveying the island intensively for 20+ years, uncovering a huge and mostly endemic ant fauna. Georg Fischer has been working for some years on the collections of Malagasy Pheidole, and, in the process found something very strange. There is an extremely rare, and unusual group of social parasites with workers that seem to look like their hosts. Working with Sasha Mikheyev’s lab and other colleagues, we found they belong to a single clade, a mini-radiation of parasites within the broader endemic Malagasy radiation, rather than (as is typical) each parasite being closely related to their host. Using micro-CT and a comparative analysis (led by Nick Friedman), we found they have evolved size and shape to match their hosts. Parasites more generally evolve to resemble their hosts because they aim to fool predators (Batesian mimicry) or they aim to fool the hosts themselves (Wasmannian mimicry). It is hard to invoke Batesian mimicry here, which leaves Wasmannian as the putative mechanism, and this is not known for ants that parasitize other ants (although is known for other insects like beetles to parasitize ants). If true, it implies ants may sense morphology to some degree to distinguish friend from foe, and these abilities are very sensitive. There are other potential explanations too, as we discuss in the paper, just out in Current Biology. This is definitely a study that raises as many questions as answers, hopefully it will inspire some follow up experiments.
Birds use their beaks for foraging, but also for regulating their temperature, singing and a variety of other functions. Do beaks and other multifunctional traits have characteristics that are specialized for each function, or are they an evolutionary compromise? To test this, we examined beak shape and size in a family of Australian songbirds, and compared the influence of each function on the evolution of species differences. We found that foraging behaviour and climate both have an effect on the evolution of bird beaks and their characteristics, and that this also affects features of the songs these birds perform.
Read the paper led by Nick here.
Read the article OIST published on this paper: English / Japanese.
Listen to the call of Philemon corniculatus (commonly known as the Noisy Friarbird) below!
This year, our lab co-organised and hosted SWARM 2019: The 3rd International Symposium on Swarm Behavior and Bio-Inspired Robotics, bringing together 160 biologists and engineers from around Japan and the world. The theme of this conference, which has been held in Kyoto twice before, is to promote interdisciplinary interaction between biology and engineers within the realms of collective behavior and bioinspired design.
We co-organized (with Christian Peeters) a symposium within the conference, “Engineering Insect Morphology by Natural Selection” to highlight recent research from understanding how insects work to inspire robotics. From our lab, Evropi Toulkeridou presented her research on the automated segmentation of micro-CT images by deep learning. In the same session, Adam Khalife, a former intern (now a PhD student at IEES-Paris), talked about his work on the muscular and skeletal structure of worker ants.
Other talks included Christian Peeters (ant thorax), from Yuko Ulrich (collective behavior) and Adria Labeouf (social circulation), and Hitoshi Aonuma (trap jaw ant mechanics). Evan wrapped up the session by asking how the endless engineering solutions of nature, currently locked up in museum collections, can be utilised to its maximum potential to inspire human innovation.
We hope that the symposium provided a fertile ground for biologists and engineers to exchange ideas and develop collaborations.
Thank you and otsukaresama to all the volunteers and especially to Chisa for her hard work organising the logistics!
Ever wanted your taxonomic revision with its own custom-made iphone app?
Here in the lab we are always looking for ways to make taxonomic work more exciting and engaging, and we believe that technology can help us connect people with biodiversity in new ways. We have previously been exploring the use of 3D x-ray imaging for enhancing taxonomic revisions (remember the dragon ants?). But one nice thing about 3D imaging is these data can travel to many endpoints, everything from an image on your computer monitor to a physical 3D print or to virtual or augmented reality.
We were wondering how augmented reality might help enhance taxonomic revisions, and scientific papers in general. Imagine as you flip through a paper 3D figures and images pop out of the page and float on your desk. How much more exciting would that be as a way to experience new species?
Some time ago, Eli Sarnat and many of our lab members decided to revise the Fijian Strumigenys, just a little project to organize one of the coolest endemic radiations in Fiji and describe some new species. But to push it further, we thought we would see if we could do it with augmented reality enhancement. After lots of testing and looking around, we hired an app dev team based in Ukraine to code us up a custom app to display species models, 3D rangemaps, and automatically project 3D figures. The result, Insects3D, can be downloaded at the app store for iphone. Check it out, especially while reading the open source paper from Insect Systematics & Diversity. While primitive and not at all simple or fast enough to achieve for all taxonomic works, we hope it shows an inkling of what’s possible in the future. Let us know what you think!
Light-vented bulbul (Pycnonotus sinensis), one of the species of interest in the Ryūkyū archipelago.
Biogeography is often more complicated than the species-area relationship as discussed in a recent Journal of Animal Ecology paper testing multiple extensions of island biogeography theory. Sam Ross, lead author of the study, describes how this work fits into the long history of biogeography research.
The species-area relationship is considered one of the only ‘rules’ in ecology. We have observed more species on larger ‘islands’ (whether true islands or simply some habitat patch of interest) in studies of different plants and animals all around the world. When MacArthur and Wilson (1967) proposed this pattern and the pioneering biogeographical principles which underpin it, they acknowledged that a piece of the puzzle was missing: species identity.
Biogeographers have since recognised that species aren’t randomly distributed across the globe. We now believe there to be ecological factors which predict where species occur. For example, predators can only live in habitats where their prey are sufficiently abundant, otherwise they’ll starve. This led Dominique Gravel and colleagues to predict that larger islands should have more complex food webs, since smaller islands support fewer prey species and so can in turn support fewer, if any, predators (Gravel et al. 2011). They then proposed that predators should be more influenced by island size than their prey, producing steeper species-area relationships for higher trophic levels. They called this idea the ‘trophic theory of island biogeography.’
We tested this empirically using checklists of bird sightings across the Ryūkyū archipelago running from southern mainland Japan to Taiwan. We separated birds by their trophic groups and found that contrary to the trophic theory of island biogeography, our predatory birds didn’t really differ in the slope of their species-area relationship from our herbivorous birds. This wasn’t really what we expected to find but the trophic theory hasn’t yet been tested across a range of different study systems, so our test helps us to understand whether communities may be structured by trophic level or not.
Expectation versus reality of our test of the trophic theory of island biogeography with the birds of the Ryūkyūs.
Another way species’ identities might structure communities is based on the idea of environmental filtering. These filters are thought to be strongest on small islands, where there is little opportunity to just scrape by. Small islands are harsh; there are many ways populations can go extinct on small islands, but particularly life on these islands is strongly affected by environmental conditions. This means that only species particularly suited to the environment are likely to survive and thrive on small islands. By expanding on the work of Claire Jacquet and colleagues (Jacquet et al. 2017), we could then predict that small islands would have species which are similar to each other and are all adapted to the local environment, whereas larger islands are more likely to contain random species from the regional pool of all species which could possibly live there.
Another longstanding idea predicts the opposite pattern. Because smaller islands have fewer resources, species must compete for those finite resources to survive. This means that on small islands, we might expect species to be widely different from each other to minimise competition for food and space. If there’s only one small grasshopper population on the island for example, it seems more likely that we’ll find five species of birds that all eat different things than five that are competing for the chance to eat this one grasshopper. So, we might expect that competition results in distinctive species on smaller islands and that as competitive pressure relaxes on larger islands, these islands again are more likely to contain a random assortment of species.
Blue Rock Thrush (Monticola solitarius) pictured at Cape Zanpa, Okinawa—the edge of the island.
We tested whether either of these two processes structured the bird communities of the Ryūkyūs by calculating the functional and phylogenetic diversity of birds on each island using two global databases. We used the global phylogeny of birds and a database of functional traits to measure the observed functional and phylogenetic diversity of birds on each of our study islands. We also tested whether this observed diversity was higher or lower than expected by random chance by shuffling the names of species on the phylogeny and functional trait matrix. Together, this meant we could test whether diversity was lower than expected by random on small islands and increasing to a random sample of the regional pool (trait-based assembly), or whether competitive assembly occurred, where diversity was higher than expected on small islands and closer to random on larger islands.
We found no clear overall pattern of either trait-based or competitive assembly of bird communities in the Ryūkyūs, but we did find some differences among our trophic groups in whether communities were structured randomly or not. The insectivorous intermediate predators showed patterns of trait-based community assembly since their phylogenetic and functional diversity was lower than expected on small islands and increased to random on larger islands.
Community assembly processes across our trophic groups of birds. We found no clear patterns for apex predators or herbivores, but intermediate predators followed the predictions of trait scaling by Jacquet et al. (2017).
Overall, we tested multiple extensions to the theory of island biogeography which have been rarely tested, and certainly not extensively across a range of study locations and focal species. In the subtropical Ryūkyū archipelago, we found that bird communities did not clearly conform to the theories laid out by recent extensions to island biogeography theory, but that some held true. For now, we encourage others to continue testing these hypotheses in a variety of study systems to see whether our subtropical bird communities show the same biogeographic patterns as animal communities around the world.
This post is written by: Sam Ross, a PhD student at Trinity College Dublin studying ecological responses to global change and a visiting research student at the Arilab.
Ross, S. R. P-J., Friedman, N. R., Janicki, J., & Economo, E. P. (2019). A test of trophic and functional island biogeography theory with the avifauna of a continental archipelago. Journal of Animal Ecology. DOI: 10.1111/1365-2656.13029
You can read the full paper here.