Monthly Archives: August 2012

Friday Favourites

Since the new post on non-vascular plants and ferns has been delayed, I thought I’d put together a brief collection of the most interesting science news that has come across my desk this week.

Predatory beetles eavesdrop on ants’ chemical conversations to find best egg-laying sites

There is a complicated relationship between ants (Azteca instabilis),  scale insects (Coccus viridis), lady beetles (Azya orbigera), and phorid flies (Pseudacteon laciniosus) on the coffee plants in Mexico.  The ants protect the scale insects from predators so that they can ‘farm’ their honeydew (the sugar dense liquid that aphids and some scale insects produce when they feed on plant sap).  Because the ants are protective, large quantities of scale insects can be found in these ant run farms on coffee plants.  Scale eating coccinellids, or lady beetles, would be killed by the ants as adults, but their larvae, who also appreciate a scale meal, are covered in sticky, waxy, filaments that protect them from ants.  Finding oneself born in a scale farm would mean an important, and easy, first meal for a lady beetle larva.

An ant having a sticky encounter with a lady beetle larvae. Photo by Ivette Perfecto from the University of Michigan press release.

Even though the larvae may be protected, the female lady beetle still has to arrive in ant guarded territory to lay her eggs somewhere the ants won’t immediately find them (sometimes she’ll even lay them underneath scale insects).  As seen in the video above,  getting around the ants is a challenge, but worth it, if it means giving her offspring the best start to life (an open buffet).

Enter the phorid flies.  The ants themselves are not immune to predation, and for them, the parasitic phorid flies are the stuff of nightmares.  Phorid flies attack ants and lay their eggs in them, while the ants are still alive.  The larvae develop within the ant until eventually the ant is decapitated when the fly is ready to emerge.  It seems that phorid flies require a moving target though, in order to know that their future ‘baby sitters’ are alive and ready to be hosts.  Because of this, the ants have developed a simple strategy – they freeze when phorid flies are around.

When a fly attack begins, the ants release a very specific pheromone that tells the entire colony to stop moving.  In turns out,  female lady beetles have learned to recognize this fly attack pheromone so when they smell it, they know they have a clear window to come in and lay their eggs.  This is especially interesting because it is one of the first examples of a non-ant picking up on those ant specific pheromones.

Hsun-Yi Hsieh, Heidi Liere, Estelí J. Soto, Ivette Perfecto1, “Cascading trait-mediated interactions induced by ant pheromones”,  Ecology and Evolution, published online: 27 JUL 2012. DOI: 10.1002/ece3.322

Birds that live with varying weather sing more versatile songs

Cardinalis sinuatus, the Desert Cardinal, one of the song birds studied. Their songs change in volume and tempo with changing seasonal precipitation averages. Photo © by Motorrad67 Source: Wikimedia commons, Uploader: Motorrad-67 [link]

Current research seems to suggest that for birds, variation in songs has something to do with variation in habitat.  Looking at 44 species of North American song bird, a study published this week found that variation in precipitation changed the complexity of bird songs.  Why might this be? One idea, put forth by the study’s authors is that precipitation levels affect plant growth (in terms of sheer amount as well as diversity of vegetation types), and plant growth affects acoustics.

Co-author, Clinton D. Francis, said:

Sound transmits differently through different vegetation types. Often when birds arrive at their breeding grounds in the spring, for example, there are hardly any leaves on the trees. Over the course of just a couple of weeks, the sound transmission changes drastically as the leaves come in.

Iliana Medina, the other co-author of the study, added:

Birds that have more flexibility in their songs may be better able to cope with the different acoustic environments they experience throughout the year.

And this would make sense, given that a song that would be ‘successful’ (reproductively speaking) at one time of the year, say in the winter or during drought times in a bare field, might sound quite different being sung during a lush spring.

Iliana Medina and Clinton D. Francis, “Environmental variability and acoustic signals: a multi-level approach in songbirds”, Biology Letters, Published online August 1, 2012, doi: 10.1098/rsbl.2012.0522

Wasps and Hornets Start the Wine Making Process (Seriously)

Vespa crabro, the European Hornet, plays an important role in wine making as an early yeast bringer. Source: Wikimedia Commons, User: PiccoloNamek. Creative Commons Attribution-Share Alike 3.0 Unported. [link]

NPR has an interesting read about a study published online this week in the Proceedings of the National Academy of Sciences.  The process of wine making is an ancient and commercially significant one that is all about fermentation.  Traditionally, we think about wine making as a process westart – after the grapes are picked and crushed, we either add yeast or make due with the ambient yeasts in the air.  It turns out, we’re not as in-control of when the process starts as we thought we were.

Paper wasps and European hornets feed on grapes –  Vespa crabro, common in the Mediterranean and Southern Europe, apparently has a mouth particularly well designed for breaking the skin of grapes.  When they feed, they leave behind Saccharomyces cerevisiae from their gut, otherwise known as brewer’s yeast.  Since wasp and hornet mouth parts are so small, a little bite doesn’t stop the grape from being harvestable, but it does start the fermentation process, ever so slightly, while the grape is still on the vine.  Wine from different regions tastes differently, not just because grape varieties and growing conditions are different, but because the local yeast strains are different.  Now it seems that not only ambient and added yeast affect the flavour, but the gut flora of the local insects play a role too.  Wine made from grapes that have had fermentation begin while still on the wine will taste differently than wine made from grapes where fermentation begins later. Wasps and hornets, as much as we sometimes try to keep them out of our spaces, help give wine their flavour.

Anyone growing their own grapes from home wine making might not want to discourage wasp activity in their yard.

Irene Stefanini, Leonardo Dapporto, Jean-Luc Legras, Antonio Calabretta, Monica Di Paola, Carlotta De Filippo, Roberto Viola, Paolo Capretti, Mario Polsinelli, Stefano Turillazzi, and Duccio Cavalieri. “Role of social wasps in Saccharomyces cerevisiae ecology and evolution”, PNAS, Published online July 30, 2012, doi: 10.1073/pnas.1208362109.