Bodega Tropical Kingbirds

After a maddening seawatch for boobies at Bodega Head, Jay Riggio, Jessie Godfray and I went down a little bit looking for migrant passerines at a nearby small pond (with the clever name: hole in the head). After quickly hearing a kingbird, we located it briefly and saw that it was quite a yellow bird. I immediately called it a Tropical and then spent the better part of a half hour while we tried to relocate it convincing myself that it couldn't have been one. Luckily, Jay had more faith and after a bit of looking, we relocated it and saw the key fieldmarks: the extensive yellow, lack of white outer rectrices on a brown - not black - tail with a notch.

Yellow, yellow and more yellow. Also the massive bill. 

notched tail, check. no white rex, check. 

At the same time we were watching one bird and noting these characteristics, another one called. Tropicals sound harsher and quicker to me than Western (or Eastern, for that matter). Eventually we saw both at once.

The last time I saw Tropical Kingbird was May of 2012... been out of Latin America for too long. I can't find a picture of a Tropical Kingbird from any of my travels, though they were common birds in Argentina, Uruguay and Peru. So instead, here is my favorite kingbird:

Snowy-throated Kingbird, Bosque de Pomac, Lambayeque, Peru. April 2, 2011

Shelter-building caterpillars

This post is a bit late in coming, but I wanted to share what I worked on for several summers with Doug Morse for my undergrad thesis. We did most of the work in 2008 and 2009, but finished up some during the summer of 2012 and it was published earlier this year.

Caterpillars, like many other animals, construct shelters for themselves, by some estimates over 60% of lepidoptera (butterfly and moth) species make some sort of shelter. Most often these are made by folding or rolling the leaves which they feed on into shelters. The shelters likely serve a variety of purposes: protection from dessication, protection from predators, reduced probability of dislodgement, etc. Interestingly, several studies had found that caterpillars in shelters suffered less predation but more parasitism and indeed, at least one author had speculated that since parasitism was often so high (90%+ sometimes!), that shelters must not be good protection.

an unidentified caterpillar folding up a Malvaceae leaf, Chiloe Island, Chile

That seemed odd to me; if parasitism was so prevalent, it must be a strong selective force and clearly some survive, so there must be some way to beat it. Working with a cool leaf-rolling moth, Herpetogramma thesausalis, on ferns in Maine, I ran experiments to test two hypotheses:

1) Shelters provide protection from parasitoids
2) Shelters are costly for the caterpillars to produce

an adult male H. thesausalis on sensitive fern, its primary host

To test the first hypothesis, I thinned shelters during the moth's pupal stage by carefully removing the outer layer of fern (the shelters usually involve 2-4 layers, so this did not expose the pupae inside). I used the pupal stage, as caterpillars would quickly rebuild the shelter when I thinned it - pupae are unable to. I found that parasitism almost doubled without that outer layer, though overall size of the shelter was only slightly smaller. Therefore, I found support for the first hypothesis - the first experimental evidence for this function of caterpillar shelters!

A cross-section of a shelter containing a parasitoid (Alabagrus texanus) cocoon.

For the second hypothesis, I divided caterpillars on ferns into three groups: the first I left alone (as controls), the second I dismantled their shelter every few days and the thirds I touched but did not destroy the shelters at the same interval. In essence, I was forcing one group to remake their shelters. Given my hypothesis, I expected that these caterpillars would either pupate smaller or later. Interestingly, the caterpillars delayed their pupation in order to rebuild shelters - an average of ~2 days later than the other groups - and they did not eclose smaller (or build smaller shelters!). Delaying their pupation puts them at increased risk for larval parasitism and delays their reproduction (the population is fairly synchronous, so this could be a big cost for some individuals). Hypothesis 2 supported!

A female ichneumonid (Itoplectis?) oviposits into a caterpillar shelter.

There is more to the story, it is a longer paper. But perhaps the most interesting thing is that there are two broad guilds of pupal parasitoids - those with long ovipositors (as seen in the above picture), which oviposit from outside the shelter, and those with short ovipositors which gnaw their way through the seams between leaves into the shelters. I suspect that larger shelters, with a longer distance between the outside and the pupa, are better protection against the former guild. However, in a larger shelter, there are more seams, which may make it easier for the latter guild to parasitize, an interesting trade-off, which I have only observational data to support.

Phaeogenes hebrus, the most common short-ovipositor species in this system.

The paper can be found here: http://link.springer.com/article/10.1007/s11829-013-9261-4#page-1 . Arthropod-plant interactions publishes lots of great - if limited interest - research, I read a very high number of the papers it publishes.

This would make a cool tattoo, eh?

More on parasitoid nuptial gifts

I did a bit more poking around the literature (there is, fortunately, quite a lot on parasitoids) and found many other examples where some comparison was made between mated and virgin females. Every paper seemed to have different methodology and different measured metrics (related to whatever the paper was about).

A bad picture of a beautiful wasp, Mesostenus thoracicus, female, Walpole, Maine, 2009

The results of all these studies were not at all in agreemend. Some agreed with the findings in Bracon hancocki and found that virgins lived significantly shorter lives than mated females. Others found the exact opposite. Many showed that virgins lay fewer eggs or parasitize fewer hosts (independent of eggs, as in many cases more males can develop in a host than females), but others found the opposite result. Some showed that virgin females spent less time moving and ovipositing than mated females, which suggests they wait for mates. Others found no difference in similar metrics.

An unidentified Ichneumonid (Pimplinae?) ovipositing into a Herpetogramma thesausalis pupa, Maine, 2009

Perhaps the most interesting result was that of Sagarra et al (2002) who found that female Anagyrus kamali did not differ in longevity based on mating status, but males did. Unmated males lived 40% longer than mated males and females required more than one mating to get sufficient sperm to fertilize all their eggs (some scientists believe this is rare in parasitoids, others don't - I don't have an opinion). This does suggest that males put some serious investment into their sperm, as all other conditions were equal for these males.

Bob Carlson, one of the most knowledgeable Ichneumonid specialists around, said: "There are so many kinds of parasitoid Hymenoptera, that I expect it certain that some of them have evolved such that females get sustenance from male seminal fluid. "

That seems pretty reasonable to me, though it might be a needle in a haystack search for it. Anyone interested in the references I have compiled on this or a longer summary of each paper's finding, let me know. 

This Ichneumon (Ichneumoninae, I believe) is a rare parasitoid of  Herpetogramma thesausalis. This male was
buzzing around a patch of sensitive fern with lots of host shelters, likely mate-searching.

Parasitoid nuptial gifts?

A Braconid, Alabagrus texanus, a male. I doubt any nuptial gifts are given in this species scramble-mating system. 

I found something yesterday that I think is really-cool. While browsing old copies of the journal Bulletin of Entomological Research, I stumbled across this quote, in reference to Bracon sp. (probably hancocki).

"Average life-span for mated females was 13.6 days, whereas virgin females lived for an average of 5.6 days."

Here's the catch: parasitoids are unreported (at least that I could find) to give "nuptial gifts" i.e. a resource given by male to female during courtship or copulation. Charles Godfray, in his book (bible), Parasitoids: Behavioral and Evolutionary Ecology, says "I know of no evidence of nutrient transfer during mating in parasitoids". Many other insects are known to (katydids, certain flies, etc.). This quote makes it seem like there could be some transfer of nutrients in the sperm (as the authors made no mention of courtship behavior).

Making the story more interesting, and believable, the authors state that the females copulated many times with the same male upon emergence, then began egg-laying a few days later. Multiple matings are rare in parasitoids, another indication that the female is likely gaining something else besides just sperm from the male.

An interesting observation, and one that probably could be examined, as Bracon is a fairly common genus.

Reference: Olaifa, J. I., & Akingbohungbe, A. E. (1982). Bionomics of Bracon ?hancocki (Wilkinson)(Hymenoptera: Braconidae), a Larval Parasite of Cydia Ptychora (Meyrick)(Lepidoptera: Tortricidae) in Nigeria. Bulletin of Entomological Research, 72(04), 567-572.

Godfray, HC. (1994) Parasitoids: Behavioral and evolutionary ecology. Princeton University Press. 

This is the same species in the photo above emerging from a Herpetogramma caterpillar, prior
to spinning its cocoon. 

A troubling news story

This is the first, and possibly last, political item I will post on this blog - but I feel as if I have good reason to. Read this story. As a concerned citizen, biologist and supporter of science in general, I cannot believe that this would occur - and as a proud Brown biology department alumni, I am saddened that a fellow Brown biology major (Bobby Jindal) would facilitate this nonsense.

Blow this picture up and look at the bill on this juvenile Snail Kite - perfectly evolved to eat large snails. 

I see two problems with this:

1) Obviously evolution is being horribly misconstrued, though perhaps it is heartening to hear that the books claim the Loch Ness monster is real, if that is the best anti-evolution defense they can come up with, they cannot expect to be believed wholeheartedly (perhaps). If we wish to continue to advance as a society, we need scientists working on biological questions (among all the sciences, clearly). As evolution is the backbone of biology and has informed our profitable (not monetarily, perhaps) research into human health issues as well as conservation/environmental science issues, we need to acknowledge its existence.

2) Science in general is being cast doubt upon. The credibility of evolutionary biologists/climate geologists/etc have been questioned publically by (imbecile) politicians without a firm grasp of the science, simply with a political agenda. While this is ridiculed and many of the arguments downright laughable, it is giving the public a perception that scientists perhaps are not to be trusted and their findings not true. To continue to advance and learn (I would argue a necessary part of any society) we need incorporate science better: fund it better, apply the findings in all fields, and simply understand it better (teach it better). The Louisiana system here is a regression to the middle ages. 

I wrote this in haste, perhaps it is a bit digressive and certainly a bit of a rant, but it should be brought to attention of more (as I know this blog has at least 4 people that read it!).