It’s been along time since I did a research update- so for the one or two of you that care- here are the highlights (and lowlights)….
Field Work
Field Work is largely on hold until the fall rains (that is- assuming it rains). Right now, it is 110F and dry as hell.. The populations sizes are very small- and nobody is breeding. This state will continue until it rains again…. About the population numbers- it seems that low numbers is the rule- at least in California. The MVZ people working in Lassen, and in Marin County have encountered similar situations.. The one exception seems to be Peromyscus at high elevation, where numbers seem to be good. I’ll need to make it down to the desert when (if) it rains…
The question “Why are populations so small?” is an interesting one- and likely to be more complicated than just drought.. Many of the desert animals (thinking Heteromyids) do not need extrinsic water, so therefore last years drought should have little effect on population numbers.. They are herbivores, so any reduction in seed set etc. could have an effect- but not yet. The seed bank should act as a buffer against short term drought… One interesting idea though is that the current drought coupled with prior super-abundance could do it. Last year- mice were super-abundant, and could have depleted the seed bank, giving this years mice no reserve… Any ideas?
I’m especially interested in hearing if other people are having similar problems this summer with rodents…
MHC-Peromyscus
I’m expanding the MHC work on several fronts… 1st of all, I’m doing an inter specific comparison- basically looking within Peromyscus, asking if MHC variation is related to mating system. There are a lot of confounding variables (like effective population size) that I am am particularly worried about. In addition, I am designing new primers to target a few more class 2 genes, and hopefully a class 1 gene, too.
MHC-Ctenomys
Not at liberty to speak too much here, but I’m doing a substantial amount of Ctenomys MHC work…
CytB-Peromyscus
There were a few animals whose ID’s I was not completely sure of in the field- so I’m sequencing a short chunk of cytochrome B to get the species ID.
Microsatellites- Peromyscus
Argh- this is pretty low priority work at this point- since I only captured a couple of pregnant females, and in each of those cases, sampling was pretty poor so I’m unlikely to have caught the father… In addition to the paternity stuff- msats will be used to estimate effective population size.
Microsatellites-Howler Monkeys
Truly the bane of my existence.. I’m working with poorly collected fecal DNA and consequently- nothing works well…
Ancient DNA- Ctenomys
OK- so not exactly ancient, but DNA extraction, PCR, and sequencing (cyt B) is much more difficult using 80 year old museum study skins…
Vaginal Bacteria
I’m currently doing to validation work on the vaginal bacterial analysis. Basically- I collect swabs of mouse vagina’s, and store them. Extract DNA, PCR amplification using universal bacterial primers (16S rDNA). Build clone library, then screen individuals using T-RFLP. Lots of work!!!
Mating Systems Paper
I’m working on a top secret mating systems paper… Details to follow…
Other Stuff
Kate and The Kids continue to be great
An article was published about me in Transect
I got the NSF graduate research fellowship(!!)
Although I’ve got my eyes on a multivariate stats class for fall- I think I’ve got enough to do already…
No teaching, no giving talks (hopefully), and no (more) side-projects…
Oh man- I’m going to be busy!!
7 responses so far ↓
1 Anne-Marie // Jul 17, 2007 at 8:54 pm
I don’t know if this is relevant, since I have been studying shrews (Blarina brevicauda and B. carolinensis) in Alabama and not rodents in California, but my spring collecting efforts were a total wash. We KNOW there are populations of two shrew species in our area, they’ve been collected before, and we found some old skulls in beer bottles, but only managed to trap one specimen the entire spring semester. Very disheartening. Anyway, I know it’s not really related to what you’re studying, but thought I’d at least commiserate with you on the issue of sparse critters.
2 Matt // Jul 17, 2007 at 8:58 pm
NO! I’m really interested in hearing about your problems- It’s my idea that a bunch of anecdotal evidence might lead us to some sort of explanation..
What do you think is the reason for your lack of animals?
3 Anne-Marie // Jul 17, 2007 at 11:03 pm
At first we thought that the lack of success was because raccoons were raiding our pitfall traps, but we found a LOT of crawdads and toads in the traps every day, which seemed to be evidence against that. I truly don’t know where all the shrews were, my best guess was that they were just in a low in their natural population cycle. We’re trying to find a contact zone between the northern and southern species, we have found a county where they both occur, but our collecting was worthless for both species (except for that one individual, but you can’t do much with a sample size of one).
In one section of the forest they had recently done some burns, but shrews are fossorial and usually aren’t as affected by that as other small mammals, plus that was only near a one of our transects.
I’ve joked with my friends about defaulting to “blame global warming”, but I do wonder if there is some kind of climate factor or if it is something else, maybe some environmental factor is affecting another species (one of their predators/prey) that is having secondary effects on the shrews, I really don’t know…
It’s interesting that your Peromyscus seem to be doing well at high elevations, what elevation do you consider to be “high”?
4 Sven DiMilo // Jul 19, 2007 at 8:44 am
“Many of the desert animals (thinking Heteromyids) do not need extrinsic water“
This just isn’t true. Sure, k-rats can survive on dry seeds alone, but they cannot reproduce without extrinsic water (at least in fresh green vegetation). See if you can find a paper by Nagy and Gruchacz; I’d guess around 1995 or so.
Hey, congratulations on the NSF fellowship!
5 Matt // Jul 19, 2007 at 9:00 am
Hi Sven, Yes, I should have been more specific- you’re right they DO need extrinsic water for reproduction, but not for survival alone..
6 Sven DiMilo // Jul 19, 2007 at 9:06 am
…so since the smaller species, at least, are essentially annual, drought means less recruitment and smaller populations. Maybe. Was my real point.
7 Anonymous // Aug 5, 2007 at 11:24 pm
Hi Honey,
We still miss you tons!
your wife and 5 kiddos
Leave a Comment