היומן של megachile

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. https://www.inaturalist.org/observations/118725687

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

Amphibolips galls are typically visually apparent in both generations and relatively easy to rear especially in their sexual generation. 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. This mystery is most severe in Florida, where several similar gall types are reported from many similar and often-confused host species. For this post I'm focusing on globular or spindle-shaped leaf and bud galls.

My hypothesis is simply that each host has a single species of gall wasp, which induces a spindle-shaped sexgen leaf/bud gall in the spring and a globular bud gall in the late summer-fall, persisting over the winter. This hypothesis is contradicted extensively by current literature and iNat observations, but I'm speculating that much of this is due to a combination of gall variability and mistaken host IDs.

I don't know if it's even worth listing specifically what we already do and don't think we know. At this point, I'd look for agamic galls on overwintered twigs from now into April (adults can likely be cut out already) and then collect sexgen galls on new growth in May. Priority here is to document the gall inside and out (at collection and then at emergence) and to document the host so its ID can be confirmed by experts.

I'm especially keen to get adults from galls on these hosts:

Quercus laurifolia
Quercus phellos
Quercus pumila
Quercus myrtifolia
Quercus inopina
Quercus hemisphaerica
Quercus incana

What would be ideal ultimately is to get an adult from any pair of these gall types on a single host: cinerea, spinosa, and murata (all apparently agamic, overwintering now). cinerea galls are round and smooth, dark green-purple with white spots, spinosa galls are green and pointed and have raised protrusions, and murata galls are pointed and smooth and tan.

@laurasea @ryancooke @knotwood @eickwort @noaboa @cocokitty

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