Insect-Plant Ecology

New affiliation - uncertain future for the blog

2008-02-12T17:12:00.000+01:00

Sorry for not investing into this blog during the last months. I have been busy preparing my dissertation etc. I defended my thesis last Friday and I'm now moving to Uppsala (Sweden) where I will do my post doc in Christer Björkmans group together with Anna Lehrman.

The future of this blog is thus uncertain. If it's going to live on at all it will need a major face lift. The best solution would probably be to start from scratch and involve the other group members in Uppsala.

I'll keep you posted!

In press

2007-09-27T20:09:00.000+02:00

Keep your eyes open for the following papers which will soon be available:

Stenberg JA & Axelsson EP.
Host race formation in the Meadowsweet and Strawberry feeding leaf beetle Galerucella tenella. Basic and Applied Ecology – in press. [JAS7].

Halitschke R, Stenberg JA, Kessler D, Kessler A & Baldwin IT.
Shared signals – “alarm calls” from plants increase apparency to herbivores and their enemies in nature. Ecology Letters – in press. [JAS6].

Stenberg JA, Hambäck PA & Ericson L.
Herbivore-induced ‘rent rise’ in the major host plant may drive a diet breadth enlargement in the oligophagous beetle Galerucella tenella. Ecology – in press [JAS5]

Thanks to Anurag & Jennifer

2007-09-04T11:50:00.000+02:00

Anurag Agrawal and Jennifer Thaler recently visited Umeå University. The visit was very appreciated and we enjoyed not only listening to the talks, but also conoeing and barbecuing together. This was a great way to end this years "spring semester".

Vision and/or olfaction?

2007-08-23T13:38:00.000+02:00

I recently published the following paper:

Stenberg JA & Ericson L (2007) Visual cues override olfactory cues in the host-finding process of the monophagous leaf beetle Altica engstroemi. Entomologia Experimentalis et Applicata DOI: 10.1111/j.1570-7458.2007.00597.x

It is sometimes fun to do research that is outside ones core focus. Take this paper for what it is: a hobby project.

sip13

2007-08-02T19:05:00.000+02:00

sip13 is over. It was a great meeting with lots of interesting talks and possibilities to chat with many great researchers. I especially enjoyed listening to Jennifer Thaler, Reita Gols, Jeffrey Harvey, Samantha Cook, and Tibor Bukovinsky. I had also looked forward to listen to Sören Nylin, but his talk was unfortunately cancelled...

Although lots of great stories were told, I was kind of disappointed that so few tried to link biotic processes with ecosystem functioning. But no complaints should be made - over all, the meeting was intellectually as well as socially stimulating, and I left happy but tired.

A minor observation that I made during the meeting was that people dressed slightly more elegant at sip13 than at sip12. Apparently the dress code is evolving...

Thanks to Juha and Jarmo

2007-07-14T19:21:00.000+02:00

I'm back from Kuopio and my face is more pale than ever. That's how lab work should be, :) but actually we had some great help from two students, so there is nothing to complain about!

Thanks for two great weeks Juha and Jarmo, and see you again at sip13.

Agrawal to visit Umeå

2007-06-29T10:15:00.000+02:00

Anurag Agrawal will visit Umeå during the period 20-23 August. He will give two lectures during the stay.

1. Community ecology of milkweed-herbivore interactions
Time: Monday 20 August, 13:00
Locality: KBC, Lilla hörsalen, KB3A9

2. Evolutionary ecology of milkweed defense against herbivores: A phylogenetic perspective
Time: Tuesday 21 August, 13.00
Locality: KBC, Lilla hörsalen, KB3A9

Visit to the Holopainen lab

2007-06-19T10:50:00.000+02:00

Today I got a grant from the European Science Foundation to do some research with Jarmo Holopainen and Juha Heijari in their lab in Kuopio in eastern Finland. I'll go there within two weeks, and we'll mainly do olfactometer tests with parasitoids and GC-MS analyses.

I did some research with Jarmo and Juha last year as well, and you may read our first article here.

Johan will speak at sip13

2007-05-21T16:12:00.000+02:00

Title: COMPLEX INDIRECT INTERACTIONS BETWEEN TWO PARALLELL HERBIVORE-PLANT FOOD WEBS

Abstract
Galerucella tenella (Coleoptera: Chrysomelidae) is an important selective agent of plant resistance in the perennial herb Meadowsweet (Filipendula ulmaria). The level of herbivory is, however, largely top-down controlled by the parasitoid Asecodes mento (Hymenopthera: Eulophidae) which may parasitize up to 100% of the G. tenella larvae. Here, we report that the strength of this trophic cascade depends on the presence of other prey species of the parasitoid. Apparent competition between coexisting chrysomelids and parasitoid switching may ultimately be of crucial importance for plant fitness and the evolution of plant resistance in this system.

View the conference homepage here.

Lamarck is back

2007-04-18T09:50:00.000+02:00

Well, at least his ideas are picked up in this paper where Lindqvist et al. suggest that aquired traits may have been inherited (not to be confused with maternal effects) by offspring in chickens.

Major science fraud in Umeå

2007-04-18T08:50:00.000+02:00

In September 2005 Tao Huang et al. at the Umeå Plant Science Centre published a great paper in Science in which they reported about a breakthrough in our understanding of how plants control their flowering. Science later ranked their finding as the third most important breakthrough of the year.

The corresponding author Ove Nilsson now reports that one of the members of his group (the Chinese first author) manipulated the data. The Chinese researcher left Umeå last year, and he was replaced with another Chinese which was not able to repeat his results. The remaining authors conclude that Huang removed some data points and exaggerated others to get the "wanted" results.

This is, of course, a big shame for all of us working here in Umeå. It is comforting, though, that they discovered and reported about the fraud themselves.

I have a feeling that fraud is becoming more and more common in science. If PhD-students and postdocs don't publish good results they will be wiped off the scientific arena. Of course it can be tempting to "adjust" a data point or two if your career depends on that.
I guess that the scientific career is over for this Chinese fellow. His great results are of no use for him anymore...

Spring is coming to the North Pole

2007-03-28T12:26:00.000+02:00

The fall was extremely warm last year, and the spring is coming extremely early as well. Two days ago we had the warmest March day ever in Umeå.
Today I observed the first butterfly emerging from its long winter custody, and I suddenly realized how much I've missed the summer. Now its at least temporarily back again and I enjoy every minute!

First pollination of the year

2007-03-15T14:50:00.000+01:00

It's been a pleasant stay in Stockholm so far. There's no snow here and air temperature is about 10 centigrades. Outside the Department of Botany I observed the first insect-plant interaction of the year: it was a slow bee that pollinated flowers of the Winter Aconite Eranthis hyemalis.

Out of office

2007-03-11T15:44:00.000+01:00

Sorry for being out of my virtual office for a while. I will be in Stockholm next week and in Gothenburg the week after that, but I expect to be able to connect at least sporadically on the way.

In Stockholm I will do some work on parasitoids in Peter A. Hambäck's lab, and in Gothenburg I'll give some lectures, e.g. at the Natural History Museum. I look forward to both! After a long winter in Northern Sweden it will also be nice to go some 1000 km southwards and enjoy the spring in southern Sweden.

Paper of the week (8 - 2007)

2007-02-25T15:41:00.000+01:00

Kessler D & Baldwin IT (2007) Making sense of nectar scents: the effects of nectar secondary metabolites on floral visitors of Nicotiana attenuata. The Plant Journal 49: 840-854.

This paper contains loads of interesting stuff. It's very long, but rewarding. Here, I will only give you a brief summary of the most interesting results.

The authors identified secondary metabolites in the headspace and nectar of the native tobacco plant, and further tested the attractiveness of individual metabolites to two pollinators (a moth and a hummingbird) and one nectar thief (an ant).

The most interesting finding (in my view) was that the nectar contained many compounds that were repellent to the pollinators, and that the presence of repellents (nicotine) increased the fitness of the plant by making the pollinators remove less nectar and thus visit more flowers per volume consumed nectar.

"Nectar, which was thought to be nature's soft drink, may not be so soft after all".

It is intriguing that the tobacco hawk moth used in this study is not only an important pollinator. The moth also oviposits on the plant leaves, whereafter a single caterpillar may consume the whole plant in a very short time. Hence, the concentration of repellents in the nectar may potentially be a decisive factor for female moths when searching for plants to oviposit on.

This is a must read paper for everyone working with either pollination or herbivory. But make sure that you have plenty of time before reading.

Are trophic cascades more likely in the North?

2007-02-23T17:19:00.000+01:00

Several reviews have concluded that trophic cascades are more common in aquatic than in terrestrial systems (e.g. Persson 1999, Oikos 85: 385-397). However, two recent studies have shown very strong top down effects in terrestrial systems (Dahlgren et al. 2007, Stenberg et al. 2007). The study area of Dahlgren et al. (predator-vole-plant) is located on the Norwegian tundra, while the study area of Stenberg et al. (parasitoid-beetle-plant) is located in a boreal archipelago in the Gulf of Bothnia. Hence both of these trophic cascades represent relatively simple systems at high latitudes.

Now, does this point to a general pattern? Are terrestrial trophic cascades more likely at high latitudes, and, if so, is this due to their relatively low species diversity? I don't know, but it might be something to think about.
Feel free to send me an email if you're interested in measuring predation/parasitoid pressures along latitudinal gradients in America and/or Europe.

How to write consistently boring scientific literature

2007-02-23T02:19:00.000+01:00

Well, that is actually the title of a recent Oikos paper by Kaj Sand-Jensen.
[ I'm a chordata, urochordata! ] posted a jolly good review of the paper in his blog. Below is Sand-Jensen's top 10 points for writing boring papers.

1) Avoid Focus
2) Avoid originality and personality
3) Write l o n g contributions
4) Remove implications and speculations
5) Leave out illustrations
6) Omit necessary steps of reasoning
7) Use many abbreviations and terms
8) Suppress humor and flowery language
9) Degrade biology to statistics
10) Quote numerous papers for trivial statements

Someone should also write a paper on How to write consistently boring blog posts.

Online Journal Club

2007-02-22T15:29:00.000+01:00

I guess most scientists have participated in various journal clubs from time to time. At small departments, however, starting a journal club with focus on i.e. insect-plant ecology would be useless. The number of people interested in this issue may simply be too small at individual institutes.

One potential opportunity would be to start an online journal club with participants from UC Davies in the west, all the way to Helsinki in the east. One interesting (but too broad) example can be found at www.journalreview.org.

Please, feel free to give some feedback to the idea of an online insect-plant journal club if this sounds fruitful to you.

Norway unveils 'doomsday' seed voult

2007-02-19T13:20:00.000+01:00

The journal Nature reports that the Norwegian government has decided to build a 'doomsday' seed bank to protect crop strains from war, climate change, and other disasters.
The vault, which will be buried deep in the interior of an arctic mountain on Svalbard, will offer a safe haven for some 1.5 million crop strains from all over the world. Well done Norway!

Read the full story here.

Paper of the week (7 - 2007)

2007-02-18T17:44:00.000+01:00

Boege K, Dirzo R, Siemens D & Brown P (2007) Ontogenetic switches from plant resistance to tolerance: minimizing costs with age? Ecology Letters 10: 177-187.

This is a really nice paper showing that Raphanus sativus (Brassicaceae) simultaneously expresses ontogenetic trajectories of resistance and tolerance with an apparent trade-off. Young plants were less tolerant to defoliation than old ones, which in turn were less resistant than young plants. The ontogenetic change from resistant to tolerant plants was apparently associated with the onset of reproduction (when resources are allocated to seed production).

Raphanus sativus is an annual plant, and hence, there is no need to allocate energy to resistance of mature leaves, which the plant has no use of after seed set. Whether the pattern reported here is true for perennials (including ever-green species) remains an open question.

In conclusion: This is a great paper which should be of interest to everyone working with herbivory. The paper is, in my opinion, overlong (11 pages), but on the other hand the authors develop their theory in an understandable way. Well done!

Oekologie #2 now up

2007-02-17T08:41:00.000+01:00

The second edition of the blog carnival Oekologie is now up at Perceiving Wholes. See it here.

Fruit flies live longer if they can't smell their food

2007-02-12T16:50:00.000+01:00

And here's a Science paper showing that Drosophila flies live longer if they can't smell their food, i.e. if their olfactory sense is dysfunctional.

I promise to eat my socks if this is not due to some pleiotropic effect.

Paper of the week (6 - 2007)

2007-02-11T01:44:00.000+01:00

Gripenberg S, Salminen J-P & Roslin T (2007) A tree in the eyes of a moth - temporal variation in oak leaf quality and leaf-miner performance. Oikos doi: 10.1111/j.2007.0030-1299.15415.x.

This paper shows that the chemical defense of oak trees, and the corresponding performance of a lepidopteran leaf miner, varies in time and space. Tree quality, in terms of phenolic content and larval survival, showed a temporally stable pattern at the level of individual trees. This, however, was overshadowed by a high variation within trees (branches) throughout the growing seasons; i.e. it will be very hard for a female moth to judge whether a particular branch will remain good or bad for her offspring. These findings have many important implications; the most obvious perhaps that local adaptation to individual trees must be very unlikely to happen. Clearly, the results are not in concordance with Susan Mopper's adaptive deme formation hypothesis.

Although not being the focus of the paper, the authors also showed that larval performance correlated negatively with the initial numbers of eggs laid on individual leaves. This contrasts to the findings of Wise et al. (2006) who showed that an intermediate group size is optimal in spittlebugs.

I believe this is Sofia's fourth published paper during her PhD studies. That's impressive! Apparently she and Tomas love Oikos. :)

New paper

2007-02-08T14:08:00.000+01:00

The following paper will be published in the March issue of Oikos:

Stenberg JA, Heijari J, Holopainen JK & Ericson L (2007) Presence of Lythrum salicaria enhances the bodyguard effects of the parasitoid Asecodes mento for Filipendula ulmaria. Oikos 116: 482-490.

If you want the pdf or offprints just send me an email and I will send it to you as soon as it is available.

Call for less explanatory factors in experimental ecology

2007-02-06T22:25:00.000+01:00

Am I the only one who find it hard to interpret multi-way interactions when reading the result sections of ecology papers? Quite a few of the papers I've reviewed the last couple of months contain so many explanatory factors that it makes it really hard to follow and judge whether the authors' interpretations are sound. Just what does a significant block((site)country)*year*host*size interaction tell you?
There should be some informal rule forbidding investigators to include more than three explanatory factors when designing experiments, and nesting should only be permitted in extreme situations.

ESA blog fiasco

2007-02-06T22:10:00.000+01:00

I've previously highlighted some well written and up-to-date ecology blogs, and I will sooner or later create a blog roll with links to all ecology blogs worth reading. Now, however, is the time to give some just critique to bad blogs...
The worst ecology blog in the entire blogosphere will probably be the official ESA blog. First, it is rarely updated, and second, it is more about politics than pure ecology.
I can't say I'm surprised though. ESA has one of the worst ecology homepages, and it doesn't publish its journal articles online early either. They simply suck when it comes to online issues.

Paper of the week (5 - 2007)

2007-02-04T11:53:00.001+01:00

Noret N, Meerts P, Vanhaelen M, Santos AD & Escarré J (2007) Do metal-rich plants deter herbivores? A field test of the defence hypothesis. Oecologia doi: 10.1007/s00442-006-0635-5.

In this paper Noret et al. show that the leaf concentration of heavy metals in Alpine Penny-cress (Brassicaceae) is more or less unimportant in detering herbivores. However, although the herbivores didn't discriminate against heavy-metal rich individuals, the herbivore load was much lower in metalliferous than in normal, uncontaminated sites. I was surprised that the authors did not test for herbivore performance on plants with different concentrations of heavy metals, but I will come back to that critique later. Now back to the story...
Instead of heavy metals, susceptibility to herbivores was shown to correlate with concentrations of secondary plant compounds, especially glucosinolates.

And now to the interesting stuff. In this large-scale experiment the authors show that the concentrations of glucosinolates differ between plant ecotypes that have evolved in metalliferous and normal, uncontaminated sites. Ecotypes at metalliferous sites (with low herbivore loads) contained lower concentrations of glucosinolates than ecotypes which have evolved in normal, uncontaminated sites (with high herbivore loads). Hence, it seems likely that selection for herbivore resistance has been relaxed in metalliferous sites, leading to lower concentrations of glucosinolates.

The findings in this paper are interesting and worth reading. There are however a number of important questions that the authors didn't comment on:
1. Is herbivore performance affected by the leaf concentration of heavy metals? If not, why is the herbivore load lower in metalliferous sites? Personally, I am not satisfied with just getting the info that glucosinolates, and not heavy metal content, determin if the plant is accepted by the herbivores.
2. Does natural herbivory reduce plant fitness? This is of utmost importance for the authors theory that reduced herbivory has led to the evolution of more susceptible plants in metalliferous sites. On average, only 3-6 % of the leaf areas were consumed in the investigated populations, so it may be questioned just how important herbivory is in this case.
3. There is no information on when the metalliferous sites became contaminated. Has the selection for reduced resistance been ongoing for 20 or 500 years?

Finally, an apology from my side. This paper is not so much about insect herbivory, but more about slugs and snails.

An intriguing and provocative squirrel paper

2007-01-30T11:57:00.000+01:00

Just before Christmas Boutin et al. published a mind-provocative paper on "Anticipatory Reproduction and Population Growth in Seed Predators" (squirrels) in the journal Science. The authors present strong evidence that two squirrel species do not follow a resource-tracking strategy but instead adjust their reproductive investment according to future rather than past seed crops. As I said, the evidence presented are quite strong, but I still find this very hard to digest. It will be very interesting to see how other ecologists will react upon these results.
Will this be the start of a new paradigm in the consumer-resource research? Well, I am sceptical about it.

Paper of the week (4 - 2007)

2007-01-25T16:18:00.000+01:00

Leavitt H & Robertson IC (2006) Petal herbivory by chrysomelid beetles (Phyllotreta sp.) is detrimental to pollination and seed production in Lepidium papilliferum (Brassicaceae). Ecological Entomology 31: 657-660.

A couple of months ago I reviewed McCall & Irwin's florivory review (ELE 9: 1351-1365). In that paper they cited a handful of studies showing that florivory may affect the pollinator visitation rate to damaged flowers. The present paper by Leavitt & Robertson provides further evidence on the importance of florivory on pollination and seed set.

Leavitt and Robertson exmined whether feeding damage to mature flowers by chrysomelid beetles reduces the likelyhood of pollination and fruit set in a rare mustard endemic to sagebrush steppe habitat in south-western Idaho. The plant is dependent on insects for pollination.
Prior to blooming, the authors covered naturally growing plants with cages. At the time of blooming they released five beetles into each cage to damage the plants during 24 hours. For each plant, one damaged (see picture) and one undamaged flower was marked for later recognition. Half of the plants was then being hand pollinated and the other half was exposed to natural pollination.

Flowers with a hole chewed in a petal produced fruit and seed at a significantly lower rate than undamaged flowers, but this difference was wiped out when the plants were hand pollinated. These results show that florivory in itself did not reduce plant fitness, but reduced the effectiveness of the insect-mediated pollination.
The authors suggest a number of factors which may have contributed to the reduced effectiveness of natural pollination. In my view, the most plausible explanation is that the damaged flowers were less attractive to the pollinators, which in turn may have to do with e.g. reduced amount of nectar.

I liked this paper because it didn't just test for the effect of florivory on pollination, but, more important, the authors also showed that the altered pollination affected the fecundity of the plant. I would, however, have appreciated if the authors had estimated the prevalence of natural petal herbivory - are the beetles perforating almost all petals in nature, or only a few?

New journal: Arthropod-Plant Interactions

2007-01-24T10:03:00.000+01:00

I was asked to post a note about a new quarterly journal which has been launched by Springer: Arthropod-Plant Interactions.

Description (copied from the journal homepage)
"Arthropod-Plant Interactions is a quarterly journal committed to the publication of high quality original papers and reviews with a broad fundamental or applied focus on the ecological, biological, and evolutionary aspects of the interactions between insects and other arthropods with plants. Papers focusing on all aspects of such interactions including chemical, biochemical, genetic, and molecular analysis, as well as papers reporting on multitrophic studies, ecophysiology, and mutualism, are welcomed. Studies that present field-based long-term data are strongly supported".

Let's hope that the new journal becomes a great success! I look forward to the first issue.

Paper of the week (3 - 2007)

2007-01-19T09:32:00.001+01:00

Løe G, Toräng P, Gaudeul M & Ågren J (2007) Trichome production and spatiotemporal variation in herbivory in the perennial herb Arabidopsis lyrata. Oikos 116: 134-142.

This is a very nice paper dealing with Arabidopsis-herbivore evolution in natural populations along the Norwegian and Swedish coast lines.
A short background: the host plant is polymorphic for trichome production and glabrousness is caused by a recessive mutation at a single locus. The proportion of glabrous plants differs between populations, with some populations being monomorphic glabrous, and other being dominated by trichome producing plants.
In this paper the authors show that (1) glabrous plants are more damaged than trichome-producing plants in polymorphic populations, and (2) that trichome-producing plants were more prevalent in populations characterized by high levels of herbivory. The main herbivore in the investigated populations was the diamondback moth (Plutella xylostella).
The results suggest that trichomes function as a defense trait in A. lyrata. The results are also in concordance with theory suggesting that the allocation to resistance traits should be positively related to the risk of herbivore damage. Hence, it seems likely that the herbivores are important selective agents for the maintenance of polymorhism in trichome production.

There are, in my opinion, some additional questions that the authors should have addressed:
1. Is there any cost associated with trichome production? The answer is probably yes, and the authors might have taken this for granted, but as a reader I would have found it helpful if this had been stated somewhere in the paper.
2. Is herbivory associated with reduced plant fitness? This might have been the scope of some previos paper which I've missed, but I didn't find any reference to any such study.
3. Finally, is the interaction reciprocal? I would assume that the herbivores face different challenges in glabrous and trichome producing populations, which may create different selection pressures. On the other hand, the diamondback moth is probably a great flyer, implying that any local differences between moth populations would be evened out by migration.

To conclude, I think that this paper is both important and nice to read. Geir Løe defended his thesis last year, and this may be a good opportunity to read his other papers delaing with this study system at the same time.

Crafoord prize to Robert L. Trivers

2007-01-18T17:19:00.000+01:00

The Crafoord Prize in Biosciences for 2007 was awarded to Robert L. Trivers "for his fundamental analysis of social evolution, conflict and cooperation". Click here for the press release.
Lets hope that an insect-plant ecologist will be awarded when the prize is announced next time (2011).

Crafoord prize winner to be announced

2007-01-14T18:55:00.000+01:00

On Thursday 18 January the Crafoord Prize in Biosciences (i.e. Ecology and Evolution) 2007 will be announced. The prize has previously been awarded to e.g. Daniel Janzen, Paul R. Ehrlich, and Robert M. May.
The prize sum of USD 500,000 makes the Crafoord one of the world's largest scientific prizes.

Paper of the week (2 - 2007)

2007-01-14T17:54:00.000+01:00

Tylianakis JM, Tscharntke T & Lewis OT (2007) Habitat modification alters the structure of tropical host-parasitoid food webs Nature 445: 202-205.

I recently reviewed Tylianakis et al.'s article in the December issue of Ecology where they found that parasitoid and host diversity affected parasitism rates and the stability of this parasitism in a diverse community of hosts (cavity-nesting bees and wasps) and parasitoids (e.g. solitary, gregarious, and kleptoparasites). The investigation was made in five different habitat types (representing a gradient of increasing anthropogenic modification), but in that article they didn't find any effect of habitat modification.

In the present Nature paper they reanalyze the same data set showing striking changes in quantitative food web structure across the modification gradient. "The evenness of interaction frequencies declined with habitat modification, with most energy flowing along one or a few pathways in intensively managed agricultural habitats".
Another interesting finding was that the most abundant parasitoid was more specialized in modified habitats, with reduced attack rated on alternative hosts.

PLoS one

2007-01-05T19:34:00.000+01:00

The open access journal PLoS Biology has become a great success reaching impact factors that should scare both Nature and Science. The much more revolutionary PLoS one has apparently faced much more resistance from the scientific community. This far only a few articles have been published, and no article has more than 5 annotations - actually most articles have zero annotations.
This is a big shame! I think that this kind of open access online publication has to become the future of scientific publishing. What are we (the authors and reviewers) afraid of?

Science blogs

2007-01-05T11:21:00.000+01:00

There are quite a few so called 'science blogs' in the blogosphere. However, many of these are not by, or for scientists, or even about science.
The journal Nature recently ranked the top 50 most popular 'real science blogs'. They defined a 'science blog' as a blog written by a scientist about science (and not about his cat).
Some of these are indeed worth visiting, but I've found that a very high proportion of them deals a lot with pseudo-issues, like evolution vs. creationism, and not with real science. This was disappointing...
However, there are two blogs that I would like to recommend, namely Matt MacManes Behavioral Ecology Blog and Jennifer Forman's Invasive Species Weblog. Check them out!

Paper of the week (1 - 2007)

2007-01-02T11:13:00.000+01:00

Berenbaum MR & Zangerl AR (2006) Parsnip webworms and host plants at home and abroad: trophic complexity in a geographic mosaic Ecology 87: 3070-3081.

I always enjoy reading papers by these authors and this article is no exception. This time they've compared outcomes of the interaction between 'their' wild parsnips and parsnip webworms in their area of introduction (US, where the interaction is ubiquitously two-species) to the indigenous area in Europe, where the webworms preferentially feed on an alternative host plant.
On both continents they found lower concentrations of resistence compounds where webworms were rare, and higher concentrations where webworms were abundant. They also found that the webworms prefered an alternative host plant in Europe, while in America parsnip is the only available host plant. Further, the concentrations of resistance compounds were higher in parsnips than in the alternative host plant, and the capacity to detoxify was higher in American webworms which are 100% dependent on the parsips, than in the European webworms which may utilize the less resistant alternative host plants.
The results are in concordance with John N. Thompson's geographic mosaic of coevolution theory, and imply that the intensity and direction of the interaction differs both within and between Europe and America. These results are great and should in my opinion have been the focus of the paper. Instead, the authors spend more than half of the discussion on the possible importance of parasitism in shaping the pattern of interaction. This discussion was kind of interesting, but given that parasitism was only scored for a total of 5 plant individuals in two different populations, I feel that this part of the discussion should have been saved for another, more extensive study on the tritrophic interaction.

Breakthrough of the year: Butterfly speciation

2007-01-02T11:08:00.000+01:00

Speciation is still a hot topic. When the journal Science recently honored the top 10 research advances of 2006 the work of Mavárez et al. (2006) was to be found on 7th place. The study by Mavárez and colleagues "detailed the most convincing case yet of a species that arose through hybridization. They bred two species of passion vine butterflies and got the red and yellow stripe pattern of a third species. The pattern proved unattractive to the parent species, helping to reproductively isolate the hybrid".

Merry Christmas

2006-12-22T12:57:00.000+01:00

I'm going to Finland for Christmas, so there will be no paper of the week next week.
Merry Christmas and see you again next year!

Paper of the week (51)

2006-12-20T13:57:00.000+01:00

Tylianakis JM, Tscharntke T & Klein A-M (2006) Diversity, ecosystem function, and stability of parasitoid-host interactions across a tropical habitat gradient Ecology 87: 3047-3057.

The selected paper is hard to read, hard to digest, and time consuming. As always, this means that the significance of the paper is high...
The aim of this study was to elucidate whether parasitoid and host diversity affect parasitism rates (an ecosystem function) and the stability of this parasitism. In short, the authors compared parasitism rates of a diverse community of hosts (cavity-nesting bees and wasps) and parasitoids (e.g. solitary, gregarious, and kleptoparasites). The investigation was made in five different habitat types (representing a gradient of increasing anthropogenic modification) during 17 consecutive months. In total, they investigated 24 017 hosts, of which 5 328 were parasitized. (It must have been a quite expensive study...).

Parasitism rates decreased with increasing host diversity, and the authors didn't really have any good explanation for this... In contrast, parasitism increased in parallell with increasing diversity of parasitoids, most likely due to complementary host use. Interestingly, the temporal stability in rates of parasitism also increased with increasing parasitoid diversity, and this relationship was logarithmic, such that increasing parasitoid diversity gave diminishing returns in terms of stability in parasitism. I also found it interesting that there were no clear effect of antropogenic modification - the results were more or less identical in the five different habitats.

This paper is likely to be of interest for ecologists working with basic as well as applied issues. However, some time and patience is needed in order to really understand all the spatial and temporal scales, and the associated statistics.

Faculty of 1000

2006-12-19T15:21:00.000+01:00

If you want more reviews of the most interesting papers published in the biological sciences you may check out Faculty of 1000 Biology. Many of the outstanding researchers which I've linked to in this blog (right column) are engaged as so called experts to select and review the best papers in the biological sciences.
However, I find it a little sad that only (almost) papers in high-impact journals are reviewed. If you have a nice paper in for example Ecological Entomology you cannot expect to find it reviewed at the Faculty of 1000. However, you may instead have some hope that it will be reviewed in this blog. =)

Nature starts two new blogs

2006-12-18T21:25:00.000+01:00

The journal Nature has started two new blogs; one for authors which can be found here, and one for referees which can be found here.
Much more interesting, however, is Nature's reader oriented newsblog where you can comment on stories published on news@nature.com.

Paper of the week (50)

2006-12-11T15:15:00.000+01:00

Wise MJ, Kieffer DL & Abrahamson WG (2006) Costs and benefits of gregarious feeding in the meadow spittlebug, Philaenus spumarius Ecological Entomology 31: 548-555.

Ecological Entomology is definately my favourite entomological journal, and almost all issues contain some papers worth reading.
The selected paper is about optimal group size in a spittlebug which feed gregariously in shared spittle masses. The authors performed glass house experiments in which group size was manipulated. They found a negative correlation between group size and survival, suggesting that the insects were competing for limited plant resources. However, adult mass, which also is an important fitness parameter, showed a much more interesting pattern, being highest in intermediate group sizes and much lower at both low and high spittlebug densities. One explanation for the lower fitness of solitary individuals may be the difficulty to draw xylem against the negative pressure at which xylem is transported in the plant. Other possible explanations for the reduced fitness of solitary individuals were also presented, and they were all dealing with the difficulty for singles to overcome the physical and chemical defences of the plant.
The results suggest that the insects should display at least a slightly clumped dispersion, but that the benefits of group feeding saturate relatively fast, so that overcrowding should be avoided.

In conclusion: This is a nice and interesting paper which doesn't demand a lot of brain power to read. Have a cup of tea and read it when you need a break.

Paper of the week (49)

2006-12-09T17:44:00.000+01:00

Heard SB, Stireman JO, Nason JD, Cox GH, Kolacz CR, Brown JM (2006) On the elusiveness of enemy-free space: spatial, temporal, and host-plant-related variation in parasitoid attack rates on three gallmakers of goldenrods. Oecologia 150: 421-434.

First, congratulations to Oecologia for getting this nice paper. It's really one of the most well written and interesting articles that I've read this autumn.
The authors have compared parasitization rates of three herbivores on their original and a novel host plant. The background to the study is that it has been hypothesised that enemy-free space (ESF) may explain the many host-shifts in phytophagous insects. Here they wanted to test whether three herbivores, which have recently host shifted, enjoy EFS on their novel, relative to their original plant. The nice thing is that the investigation was carried out at several different sites and in several consecutive years.
The paper also contains a reveiw of previous studies on EFS, but I will not go in to that review here.

They found parasitoid EFS on the novel host plant at som sites/years, but the reverse at others. The results imply that making a host shift does not automatically lead to consistent EFS. Insted, the EFS is patterned as a geographic and temporal mosaic, which may be imagned as windows of opportunities that opens and closes in space and time. "Successful host shifting, then, might depend on a time and place where the EFS window opens far enough and long enough — for instance, where and when the novel host happens to provide EFS for many consecutive years. Such window-opening events might be uncommon on ecological time scales, and therefore rarely observed, and yet happen often enough on evolutionary time scales to permit the kind of frequent host shifting that we infer from phylogenetic and other evidence".

Field season in December

2006-12-08T14:26:00.000+01:00

Something weird is indeed happening with the climat! I just realised that the grass has been growing considerably the last couple of weeks! It would feel really strange to fetch the lawnmower now... here... This is Umeå, the icy top of the planet!
And in the newspaper they've showed pictures of flowering plants! Apparently we can look forward to high levels of pollen just in time for Christmas!
Santa Claus will have no use of his sleigh this year.

Paper of the week (48)

2006-11-30T17:09:00.000+01:00

McCall AC & Irwin RE (2006) Florivory: the intersection of pollination and herbivory. Ecology Letters 9: 1351-1365.

This paper starts with stating that as much as 18% of the terrestrial plant biomass is consumed by herbivores (Cyr & Pace (1993) was cited). I found this a little exaggerated as later studies have shown that only about 7% of the terrestrial plant biomass is consumed in temperate areas (Coley & Barone 1996) and somewhat more in the tropics (Coupe & Cahill 2003).

Nevertheless, I found this paper to be both interesting and informative. I got new insights into the different (direct and indirect) ways that florivores may influence the fitness and evolution of their host plants. The effects of florivory is apparently much more complex than the effects of folivory. I was fascinated by the dilemma on whether to chemically defend flowers against florivores (which may deter pollinators) or not. This is especially interesting as many insects (e.g. the Tobacco Hawkmoth) are important pollinators as adults, but they also oviposit on the plant, whereafter the larvae may be important herbivores/florivors of the same plant.

I would have found it helpful if the authors had formulated clearer definitions of the different kinds of "vores" that they mention in the paper; e.g. herbivore, florivore, folivore, pollenivore. In some passages the reader gets the impression that florivory and herbivory are fundamentally different things, while in other places that florivory is just one out of many different kinds of herbivory.

In conclusion: go ahead and read the paper. It's not really packed with lots of new theory, but it is a very nice compilation of the subject and it will probably be cited a lot.

SIP 13

2006-11-30T02:30:00.000+01:00

One of the most interesting meetings next year will be the 13th Symposium on Insect-Plant Relationships. It will be held in Uppsala during 29 July - 2 August.
The orginisers have put together a nice program and as usual we can look forward to some great talks.
Some of the more interesting plenary speakers are Jeff Bale, Jennifer S. Thaler, Ted Turlings, Robert A. Raguso, John L. Maron, and Marcel Dicke.

Register at the SIP13 homepage

Oikos meeting 2007

2006-11-30T02:23:00.000+01:00

The Oikos meeting next year will be held in Stockholm, 5-7 February.
I note that Frank Johansson from my department is one of the plenary speakers. Don't miss it!
For more information, see
www.zoologi.su.se/oikos/index.html

Welcome

2006-11-30T02:16:00.000+01:00

Welcome to the world's first blog focusing on Insect-Plant Interactions!
My intention is to update this blog at least once every week, so please bookmark this page and come as often as you wish.