Hunt for fly infested dogwood fruits
Hello fellow nature lovers!
I am a first year PhD student at the University of Notre Dame working in Dr. Feder's lab; for my research I am traveling around the US collecting dogwood fruits to rear out the flies that infest their fruits.
I am an Evolutionary Biologist interested in plant-insect interactions. My PhD research will focus on the population genetic structure of the fly species belonging to the Rhagoletis tabellaria species complex. Two of the four fly species infest dogwoods that are widely distributed across North America. To better understand how species form and become specialized to specific host plants, I will be collecting flies from all of the dogwood species they infest throughout their geographic ranges.
This brings me to the purpose of this journal post - I am requesting the help of the iNaturalist community to help me identify potential sites I can collect ripe dogwood fruits from.
Below are the fly species I am trying to collect and their associated host plants
(1) Rhagoletis tabellaria infests Cornus sericea/red osier dogwood
(2) Rhagoletis electromorpha infests Cornus racemosa/gray dogwood, Cornus foemina (stricta)/swamp dogwood and Cornus drummondii/roughleaf dogwood
Because we do not know much about fly infestation rates, I am ideally trying to collect 2,000-4,000 fruits from each plant species at each site. Flies are most likely to infest ripe fruit that are a bit soft (easier for their ovipositor to deposit eggs). I have not seen an infested fruit yet first hand because this is my first field season - I will post example pictures once I have some, but I've been told that infested fruits can usually be identified by:
(1) Their appearance (two-toned, looks a little off/sickly colored)
(2) Lightly squeezing the fruit (the maggot will eat the inside of the fruit, so it will have a hollowed out feel, sort of like a balloon)
(3) Opening up some fruits to look for larvae
If anyone is interested in collecting samples for me and mailing them to me I can arrange for FedEx overnight shipments, especially if you have a site with confirmed infestation.
If you are curious about trying to rear the maggots yourself we basically just put the fruits in a tray and monitor them daily for emerging larvae. Larvae are then collected, stored in moist vermiculite at room temperature for 10 days, then placed in a refrigerator to simulate over wintering conditions. After several month, the pupae are removed from the refrigerator to room temperature and monitored for adult eclosion.
I greatly appreciate everyone who has taken the time to read this! I look forward to hearing from the iNaturalist community :D
In hopes of finding potential sites and starting a dialogue with the iNaturalist community I am tagging the leading iNaturalist dogwood observers, and thanks @sambiology for telling me about this Journal feature!
C. sericea: @wdvanhem , @tsn ,@ajwright ,@charlie ,@graysquirrel ,@gwynethgovers ,@rick_williams ,@seanblaney ,@tanybo ,@csledge
C. drummondii: @sambiology ,@txlorax ,@connlindajo ,@lanechaffin ,@suz ,@foresterbabberney ,@ckneuppe ,@aguilita ,@itmndeborah ,@lisa281
C. racemosa: @wdvanhem ,@gwynethgovers ,@owenclarkin ,@seanblaney ,@rcurtis ,@sanguinaria33 ,@aaroncarlson ,@charlie ,@elfaulkner ,@reuvenm
C. foemina (stricta): @marykeim ,@mfeaver ,@edwinbridges ,@ericpo1 ,@jayhorn ,@alexdelapaz ,@vita-sativum ,@anewman ,@j_albright ,@janetwright
Thanks everyone!
Amanda Driscoe
Comments
C. drummondii is extremely common in Brazoria Co. Texas. My recollection is that it blooms about April and has white fruit in May. Occasionally, it blooms and fruits again in fall but sporadically, often after a hot dry summer followed by August rains. Indeed, I saw one such plant about 2 weeks ago. I’ll keep you in mind, but don’t know if I can harvest thousands of fruit. If you visit yourself. I can suggest some public trails with good chances of the species.
Definitely will keep an eye out for these. Though as a rule I don't send samples across state lines, especially with insects. Maybe I can at least help you figure out if it's present here in Vermont.
It will probably be impossible to mail fruit samples to the US from here but if you can arrange it I'd be happy to show you some good sites for C. sericea, C. drummondii and C. racemosa in southwestern Ontario. All three species can be easily found here.
If you can make it to Texas I can put you on large populations of C. drummondii. C. foemia is much more of a sporadic species and I normally see it growing very low densities across various wetland types (flatwoods/riverine). @eric_keith might know of some larger populations I am unaware of.
If you do make it down here, I am about to start a restoration/evolution podcast. Would love to sit down and chat about your research. That statement goes out to anyone else tagged in this group, especially grand master of the highest excellency of iNat @sambiology :) We are mere mortals that live in fear of his Olympus! My observations are merely sacrifices to abate his rage evoked lightening bolts (which would actually be appreciated by many Texas natural communities).
Sounds cool. I'm in the same boat for being in Canada though. I looked at a bunch of fruits of sericea, racemosa and (out of curiosity) amomum and alternifolia on my short walk this morning, and found no evidence of any infestations. But most of the fruits are only just starting to ripen.
Thanks everyone for your responses!
This is year 1 of a 5-7 year PhD, so this is kind of a pilot test year - my main goal this season is to collect what I can, identify areas that are known to be infested, then figure out where I need to apply for collection permits for next season. So any help along those lines would be greatly appreciated!
I am ultimately trying to collect 30 maggots from each plant species at each site for my population genetic analysis. So the number of fruits I need to collect is really just dependent on the fly's infestation rate at a given area. Our current understanding has infestation estimates ranging from 0-30%.
As far as Canada goes, I'm hoping to find some nature lovers and academics out there that are willing to collaborate with me by rearing the flies and extracting their DNA in Canada. That way I can bring back the DNA while avoiding legal issues/permits of insects crossing country lines. I haven't reached out to anyone yet on that front, but it something I intend to do given that most of C. sericea's range is in Canada.
For the Texas folks, I was actually in the Dallas area the past week collecting/scouting. Seems like your fruits are mostly at the perfect stage right now (at least where I visited), but I was not able to confirm any infestation. I also have some friends in the San Marcos area that are academics and work in wildlife management. They recently collected samples for me near Canyon Lake, Lampasas and Bay City. So if you could confirm any places with infestation that'd be amazing! Or if you know of any places worth checking out I could always ask them to scope it out for me too.
@reuvenm most dogwood species are infested by species of Rhagoletis. But for the purposes of my research I'm only interested in the Rhagoletis tabellaria complex that infest sericea, racemosa, drummondii and foemina. But I encourage you to keep exploring! It's crazy when you think about the evolution of insects adapting to specific plant species and in return the plant's adaptive response to fight off the insects.
Thanks again iNaturalist community!
Cheers,
Amanda Driscoe
Hey @amanda943, if you're looking to find academic partners in Canada I'd reach out to Dr. Heather Cray (@hcray) (Dalhousie University) and Dr. Brent Sinclair (@brentjsinclair) (https://www.uwo.ca/biology/directory/faculty/sinclair.html). They might be interested in helping out.
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