Fredrik answers questions from students
Q: How did you get interested in gall wasps?
A: I was a keen field biologists and entomologist in high school but I was also interested in science in general and I loved math and programming computers. After some thought I decided to study for a Biology major at Uppsala University, largely because that was the only university in Sweden teaching Entomology. I knew already from the start that I wanted to try a research career and I was looking for suitable problems to work with. For a while I studied parasitic wasps of the family Ichneumonidae but I became interested in plant galls after hearing a lecture about the Agrobacterium tumefasciens system and the Ti-plasmid, which had recently been discovered. Then an entomologist friend asked me if I wanted to study for him as a graduate student focusing on the phylogeny and evolution of the gall wasps and their parasitic relatives. It was the ideal combination of my interests and I knew that would get along well with my supervisor.
Q: Why are there so many undescribed species?
A: To a large extent, basic science is driven by the choice of individuals and their interests, and there have been more people interested in some groups of organisms (birds, frogs, angiosperms) than in others (nematodes, mites, many insects). As the biodiversity crisis has become more serious and started to threaten human society, however, funding agents, politicians, and others have started to create mechanisms to ensure a systematic inventory of life on the planet. This is done through initiatives like the Global Taxonomy Initiative, the Swedish Taxonomy Initiative, and the All-Taxon Biodiversity Inentories of Costa Rica and the Great Smokey Mountains.
Q: Where does the gall-inducing virus come from?
A: Nobody has been able to identify a gall-inducing virus. However, it is known that the parasitic relatives of gall wasps carry symbiotic virus-like particles in their venom reservoir and associated glands.
Q: Where did the term "gall" come from?
A: It comes from the Latin word "galla", which refers to a gall (the so-called Aleppo gall or nutgall) on oaks induced by Cynips gallae-tinctoriae. This gall was well know to the Romans since it occurs in the Mediterranean region. It was used in the production of ink and for other purposes as well because of its high tannin content.
Q: What percent of gall wasps survive to adulthood?
A: Since many gall wasps can lay hundreds of eggs, you can safely assume that less than one percent of them survive to reproduce. The actual survival rate will vary a lot from year to year and within one year from gall to gall.
Q: Where do you collect your specimens?
All over the world. You can easily rear out the insects from many types of galls but it is difficult to make gall wasps reproduce in the lab.
Q: How did the gall-wasp host plant association evolve?
A: I cannot summarize this briefly. You might be interested in looking at our recent paper in Evolution from 2002 (download a pdf here). Our studies mainly concern the early evolution of gall wasps. Other recent papers discuss the evolution of oak gall wasps, including a recent review in Annual Reviews of Entomology by Stone et al.
Q: How do the gall wasps induce the formation of plant galls?
A: Nobody knows. The gall stops developing if the young larva inside is killed, so some larval secretions are apparently needed. The large size of the venom gland in gall wasps suggests that the female may also inject compounds that are important for gall formation when they lay their eggs.
Q: What are galls made of?
A: Galls consist of plant cells that are modified in various ways. Typically, there is an inner gall with particularly nutritious cells on which the gall wasp larva feeds. Outside this there is a layer of hard sclerenchyma cells protecting the larva inside. The outer gall can be a simple swelling of the surrounding plant tissues or it can have elaborate secondary structure. The entire gall is formed from young plant cells whose development is redirected by the gall wasp.
Q: What types of parasitic wasp signals can inhibit the immune system of their hosts?
A: There are various types of compounds and symbiotic viruses or virus-like particles that suppress the immune system of the host. There has been a lot of research on the polyDNA viruses of ichneumonid and braconid parasitic wasps. Much less is known about the virus-like particles used by the relative of gall wasps (eucoiline figitids) to manipulate their hosts (Drosophila larvae). However, experiments have shown that the figitids are capable of striking out the immune system components of the Drosophila larva responsible for encapsulating large foreign objects (such as parasitc wasp larvae) without affecting the host larva's ability to defend itself (and the parasitic larva inside it) against bacterial infection.
Q: What brought you to Florida State University?
A: The weather. And all of the exciting research going on in the US in systematics and computational phylogenetics. And the good colleagues I had here before I moved.
Q: How difficult would it be to complete the Swedish Taxonomy Initiative?
A: Nobody has completed a big biodiversity inventory like this one, so it is difficult to tell. We think we have a reasonable plan and budget but only time can tell whether it is realistic in all its details. One thing is clear though: the task will be much easier when neighboring countries start their own all-taxon biodiversity inventories. We have good hopes that this will happen in the not too distant future. It is important to show we can complete the Swedish inventory because the task is going to be much more difficult for other countries. Consider South Africa, for instance, with a unique flora and fauna almost ten times the size of the Swedish and much less known.
Q: Is there a US taxonomy initiative?
A: Not like the Swedish one but there are many interesting initiatives in the US in this area, including the PBI and PEET programs of the National Science Foundation. Another exciting project is the All-Taxa Biodiversity Inventory in the Great Smoky Mountains National Park organized by Discover Life in America.
Q: How long did it take for the ancestors of gall wasps to evolve from internal insect parasitoids to gall inducers?
A: We think it's a relatively short time on an evolutionary time scale, perhaps only a few million years, but we still have to do some rigorous analyses to support this conclusion.
Q: Are gall wasps common? Where do they occur?
A: Gall wasps can be extremely common locally where their host plants grow. Sometimes you see oak trees loaded with cynipid galls. Gall wasps occur throughout North America, Europe and Asia. Only a few species are known from South America and Africa and there are no native gall wasps in Australia.
Q: What is the largest gall you have seen?
A: I have seen both bedeguars and oak galls larger than my fist.
Q: How do the inquilines kill the gall-inducing wasp larva inside the young gall?
A: According to a fascinating study of a Canadian rose gall wasp and its inquiline by Dr Joseph D. Shorthouse, published in the 70's, the inquiline female stabbs the gall-inducing larva to death with her ovipositor.
Q: How can you determine the age of gall wasps?
A: There are many approaches you can take. By studying the distribution patterns, you can sometimes find evidence that particular splits in the phylogeny correlate with geological events such as the rapid separation of tropical Africa and South America about 100 million years ago. For gall wasps and their relatives, there are also fossil specimens that you can place in the phylogenies to help you date different parts of the tree. The molecular clock can also give some indication of the age of a group. The most powerful approaches combine several of these sources of data, for instance a molecular clock with several fossil- or biogeography-based calibration points.
Q: Is the gall harmful or beneficial to the host plant?
A: It has been suggested that the gall is actually beneficial for the host plant but there is no evidence to support this idea. Instead it appears that the plant pays a price for being fooled into making the gall, as you would expect.
Q: Why did the inquilines lose the ability to induce galls?
A: We think that it is costly to initiate galls, and therefore it is advantageous for species or individuals to usurp the galls already initiated by other species or individuals.
Q: How many species of gall wasps are there?
A: There are about 1,300 described species of gall wasps.
Q: When reconstructing phylogeny, are you looking at DNA, morphology or other traits?
A: We use a combination of molecular, morphological, and biological data.
Q: Why are some galls multi-chambered?
A: Multi-chambered galls have evolved many times from single-chambered ancestral galls. They probably arise when ecological factors favor them over single-chambered galls. Many different trade-offs are probably involved in tipping the balance towards single-chambered or multi-chambered galls. For instance, one can imagine that a mother who lays her eggs in many places to make her children difficult to find for natural enemies (single-chambered galls) suffer greater mortality than a mother who puts all her eggs in a single gall that is probably easier to find for natural enemies.
Q: Are galls hard or can they be crushed by hand?
A: This varies from gall to gall. Some are soft and can easily be squished whereas others are very tough.
Q: How can I get rid of galls in my garden?
A: If the gall is young and does not have emergence holes, just pick it and burn it (or just leave it on the ground if it is so young that the gall wasp cannot complete its development).
Q: Why do gall wasps make species-specific galls?
A: It is believed that the natural enemies force the gall wasps to constantly come up with new protective devices. This causes different gall wasp species to diversify in gall structure.
Q: Can wasps survive after you open the gall?
A: Yes, if they are fully grown and have stopped feeding.
Q: How long will it take to develop systems that can identify biological organisms by matching submitted images to images in a database?
A: Such systems already exist, but more research is needed to make them more reliable and generally applicable.
Q: What projects are you currently working on?
A: My main focus is on four projects: (1) Extending Bayesian phylogenetics (the MrBayes software); (2) Developing image database technology for comparative morphology, morphological phylogenetics and biodiversity research (the MorphBank project); (3) Inferring higher-level phylogeny and evolution of hymenopterans (the HymAToL project); and (4) the Swedish Taxonomy Initiative. I'm working together with many good people, otherwise I could not contribute productively to so many different areas.
Q: What is the most rewarding part of your job?
A: There are many rewarding parts of my job. There's nothing like the excitement over a new scientific discovery. Ultimately, I think most scientists are driven by the hope to experience this feeling as often as possible. Another rewarding part of the job is the sharing of knowledge and the exchange of ideas you participate in at scientific meetings, symposia and workshops around the world.
Q: Will we ever be able to describe all species on our planet?
A: No, we will probably never have all species described. One of the problems is that new species are formed all the time, and it becomes almost impossible in some cases to say whether a group of lineages form a single species with semi-isolated populations, on their way to form new species, or if they already form a separate but extremely closely related species retaining some tendency to hybridize. Another problem is extinct (fossil) species, which will never be known completely. However, we can probably come very close to having all living species on our planet described.
Q: How do the gall wasps leave the gall when they are ready to emerge?
A: They chew a hole in the gall, through which they exit.
Q: How do you estimate how many species there are left to describe?
A: There are many ways of estimating the number of species that are left to describe. A simple method is to look at the composition of the flora and fauna of a well-investigated region, like Sweden. Sweden has about 300 species of birds and about 60,000 species in total. We know that there are about 9,000 species of birds in the world. If the faunal and floral composition is the same, we would expect to see (9,000 / 300) * 60,000 = 1.8 million species in the world. Another approach is to study the number of species in a small section of a biodiversity-rich area, and then extrapolate the species number to the entire tropics. A third method is to ask experts in different group to estimate the total number of species in their groups based on the frequency with which they encounter new species in material they collect or see from different parts of the world. Many of these methods have recently converged on a guess of about 10 million species in total. However, it is not until we have the complete inventory that we will know for sure. Until recently, molecular biologists believed that the human genome contained 100,000 genes. Now we know that it is closer to 30,000 genes.
Q: Do gall wasps occur in Florida?
A: Yes, you can probably find them on the live oaks on campus if you are lucky.
Q: What types of information are needed in order to describe a new species?
A: The description of new species is regulated by the codes of zoological and botanical nomenclature. According to the zoological code, for instance, you need to publish a description of the species (in any language) and how it differs from related species. This must appear in a publication that is available to others. The species must also be given a binomial name; it can either be placed in an existing genus, or a new genus must be named for it. For the name to be valid, one or more type specimens of the new species must be deposited in a public museum. In the future, I expect that the requirments for publishing new names in Zoology will become more strict. For instance, registration of the name in a public database will probably become mandatory, as well as deposition of images documenting the new species in an open web image repository.