Amphibolips confluenta and quercusinanis hosts

Amphibolips confluenta/quercusspongifica (afterward just confluenta for convenience) and quercusinanis are two of the most commonly observed oak wasp galls in the eastern US. They're visually apparent and short-lived sexual generation galls with a relatively high success rate in rearing. Douglas Castillejos, an entomologist in Mexico, is sequencing wasp specimens from any Amphibolips species we can get him.

One mystery I'd like to solve is the host relationships of each putative species.

According to the literature, quercusinanis is found on Quercus rubra and coccinea. All of the nearly 4000 observations we have fall within the range of Q rubra, from Minnesota to Nova Scotia. We have no putative records of it on coccinea and it seems possible that the lit reports are all just repeating an ambiguous host ID from Osten Sacken. IMO this is likely exclusive to Q rubra (as Weld lists it).

A confluenta is listed on many hosts. Of those, Quercus rubra is the apparent type host, and is among the host relationships reported by Weld and many others. However, I am becoming skeptical this is valid. Walsh collected extensively and concluded inanis was found on rubra and confluenta on velutina, exclusively, and I think he may be right.

That said, iNat reports provide a couple strong reasons to think Q rubra is a host. We have several matching observations reportedly on Q rubra made by competent oak identifiers. Galls ID'd as A confluenta have also been reported frequently in Nova Scotia, where Q rubra is the only candidate host. But I've mistaken Q velutina for rubra many times myself, and looking more closely at the NS observations, while some look like confluenta on the outside, not a single one has an unambiguously spongy interior. Conversely, spongy A confluenta galls are abundant throughout Minnesota, where Q velutina is essentially absent.

My hypothesis is that none of these are actually A confluenta on Q rubra. I'm speculating that the NS galls are variant quercusinanis and that the MN spongy galls are actually on Q ellipsoidalis, a close cousin of velutina. Q ellipsoidalis is understudied and not a recorded host of confluenta.

To test this hypothesis, I would love to get:

From Nova Scotia (@benarmstrong @benkendrick @ianmanning)

  • more cross-sections of galls to confirm the absence of spongy interiors
  • adults reared from bumpy galls with minimal to no exterior spotting.

From Minnesota (@guidingguida @kimcwren @csledge)

  • adults reared from a gall confirmed to be collected from Q ellipsoidalis
  • definitive documentation of a spongy gall on Q rubra

In these areas, I'd collect mid June and expect adults late June-early July, but your observations will help confirm those timelines.

Additionally, confluenta is also reported from:

Q buckleyi and shumardii - These are the common hosts in Texas. Not closely related to velutina so I'd like to rear one of these myself this year to confirm that this is in fact the same species. In Austin they're predicted to emerge in April.

Q coccinea - Maybe. This host is also closely related to velutina and ellipsoidalis. There are some putative iNat observations that seem plausible. But Q velutina is extremely variable and it is not easy to reliably distinguish the two.

Q ilicifolia - Checked into this and found a couple observations that seem reliable on this host.

Q marilandica, palustris, falcata - Dubious pending reconfirmation. We have a few putative iNat observations each without clear host documentation. It seems more likely to me that these hosts have distinct Amphibolips species.

Any Amphibolips adults reared from any host would be valuable additions to our understanding and to Douglas' genetic phylogeny of the genus.

@jeffdc @kimberlietx @calconey for your interest

Posted on Ιανουάριος 23, 2023 0705 ΠΜ by megachile megachile


This comports with my local observations. Have only found inanis on Q rubra (which is very common around here). and confluenta on velutina, especially at native sites (non-cultivated).

Αναρτήθηκε από calconey πάνω από 1 χρόνo πριν

Cool! I'll keep an eye-out. Can you send a reminder in the summer for gall-rearing. Haven't tried that before, but it sounds interesting @paulypod @ipat

Αναρτήθηκε από ianmanning πάνω από 1 χρόνo πριν

I didn't want to get into the agamic galls, which are a whole mystery of their own, but I did want to point out while I'm on the topic that it's very striking to me that the only keeled "tinctoriae" type galls we've seen on rubra-coccinea-velutina-ellipsoidalis are in Minnesota. A tinctoriae is listed from several east coast states in the lit but we have no corresponding observations. Maybe it's just a coincidence and they'll come in eventually but they're about the same size as A cookii and we have nearly 1500 observations of those that aren't keeled. All of the Minnesota records are on Q rubra too which definitely puts a hole in my hypothesis one way or the other (either it isn't the match of A confluenta or A confluenta is on Q rubra after all).

Αναρτήθηκε από megachile πάνω από 1 χρόνo πριν

I can definitely help with the NS piece. The few I collected and dissected last year from confirmed Quercus rubra were quercusinanis. I had planned rearings for 2023 anyway, for this and other gall species, for gall makers but also for guests / parasitoids.

Αναρτήθηκε από sdigweed πάνω από 1 χρόνo πριν

I just took a look at the distribution my observations of A. confluenta and A. quercusinanis. A few counties in North Eastern Minnesota along Lake Superior don't have Q ellipsoidalis, only Q rubra and I personally haven't come across any Q. confluenta galls in that area, only A. quercusinanis. There are a few iNat observations of possible A. quercusinanis galls in those counties but they aren't solid observations (the few that exist are all very ambiguous.)

I'll spend some time this summer collecting Amphibolips galls in general with special attention to the hosts and the keeled "tinctoriae" type galls (though those are a late summer, August find.)

Αναρτήθηκε από guidingguida πάνω από 1 χρόνo πριν

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