{"id":253,"date":"2015-04-10T00:54:48","date_gmt":"2015-04-10T00:54:48","guid":{"rendered":"https:\/\/aphidtrek.org\/?page_id=253"},"modified":"2024-12-18T16:49:04","modified_gmt":"2024-12-18T16:49:04","slug":"uroleucon","status":"publish","type":"page","link":"https:\/\/aphidtrek.org\/?page_id=253","title":{"rendered":"Uroleucon"},"content":{"rendered":"\n

Uroleucon<\/em> Mordvilko<\/strong><\/p>\n\n\n\n

This page updated:\u00a0December 2024.<\/p>\n\n\n\n

Here is another huge, messy genus with species-level taxonomy in a shambles, at least in some parts of North America.  Almost all the species feed on Asteraceae and are monoecious.  I actually published a short paper with some co-authors on one common species with a very wide host range, Uroleucon (Lambersius) erigeronense<\/em> (Thomas).<\/p>\n\n\n

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\"Uroleucon<\/a>
Uroleucon (Lambersius) erigeronensis alate from the east slope of the Cascade Range in Washington.<\/figcaption><\/figure>\n<\/div>\n\n\n

Jensen A.S.<\/strong>, G.L. Miller, A. Carmichael. 2010. Host range and biology of Uroleucon (Lambersius) erigeronense<\/em> (Thomas 1878), and its synonymy with Uroleucon (Lambersius) escalantii<\/em> (Knowlton 1928) (Hemiptera: Aphididae). Proceedings of the Entomological Society of Washington<\/em> 112: 239\u2011245.<\/p>\n\n\n\n

Since then I continue to collect Uroleucon<\/em> in the west, especially focusing on the subgenus Lambersius<\/em>. A few years ago I found an impossibly small\u00a0U. (Lambersius)<\/em> in the mountains of southern Oregon, but the season was so late that I could not identify the plant at all.\u00a0 Finally in 2018 I was able to collect this aphid again on its host plant while in bloom.\u00a0 Turns out the host is Aster integrifolius<\/em> in sagebrush steppe at high elevations. This aphid is very small, a strange mottled pale green, and has\u00a0Macrosiphum<\/em>-like siphunculi, but is probably most related to some other species placed in\u00a0U. (Lambersius)<\/em>. Another interesting 2018 find was a bright yellow species feeding among the flowers of goldenrod along a forest roadside in southern Oregon.\u00a0 The interesting thing about this was that it was tended by ants!\u00a0 Aphids shaped like\u00a0Uroleucon<\/em> are very rarely ant-tended (ant tending is correlated with short appendages and cauda).<\/p>\n\n\n\n

During December of 2021 I sat down and sorted numerous undetermined slides of U. (Lambersius)<\/em>; I also sorted some rows of slides with species names on them. I was able to place some undetermined material in named species, while simultaneously removing some slides from named species and placing them into the various groups of like specimens in my undetermined boxes. These species name changes have appeared in the slide collection database<\/a>.<\/p>\n\n\n\n

Based on all this study of U. (Lambersius)<\/em> in western North America, two things seemed possible: 1) this subgenus of aphids are mostly not particularly host-specific, or 2) there are a LOT more species out there than we currently believe, and separating those species based on morphology will be nearly impossible. In addition, species of this subgenus, even when confidently identified (as confident as can be hoped for in this genus), are frustratingly variable morphologically.<\/p>\n\n\n\n

Further work on U. (Lambersius)<\/em> based on 2022 and 2023 collecting made me continue to feel that either the species are insanely variable morphologically, or that there are numerous undescribed and unrecognizable described species. I now have about 20 sets of samples that are not identified to species but can be separated from each other and don’t key out to known species. In 2023 I was 99% convinced that our local Uroleucon (Lambersius)<\/em> species are mostly not host-specific but may instead have preferred hosts with many other plants that are acceptable. This creates a huge challenge for aphid taxonomy since we rely so heavily on host specificity in our identification keys. An interesting example from 2023 was collecting on an unidentified Erigeron<\/em> in the local pi\u00f1on pine\/juniper desert. It was fall, the season for sexuales. I noted that a few specimens could be found on each healthy-looking Erigeron<\/em> plant, and that the specimens looked smaller than, and distinct from, the usual U. (L.) erigeronense<\/em>-like specimens I find in these deserts. So, I gathered several specimens. Upon mounting and examination, these seem to mostly fit the species Uroleucon (Lambersius) zerogutierrezis<\/em> (Smith & Knowlton). This species’ normal host, Gutierrezia<\/em>, is common in the area, but no aphids were found on it. So, my hypothesis was that what we call U. (L.) zerogutierrezis<\/em> prefers, in the specific context of our desert habitat and given the weather of 2023, this Erigeron<\/em> species for production of sexuales. I saw a similar phenomenon in the deserts of central Washington when I was studying U. (L.) erigeronense<\/em>: sexuale production on the annual plant Conyza<\/em> followed by fundatrix development in early spring, long before Conyza<\/em> starts growing, on perennial Erigeron<\/em> species. A new explanatory idea emerged in 2024, however, during my sorting of about 60 new undetermined slides of U. (Lambersius)<\/em>. As I looked through dozens of slides of material all collected close to home in similar habitats and on a handful of common plants, I realized that some of the groupings I was using were essentially displaying morphological features that were intermediate between various distinctive species in the region. For example, the case just mentioned of aphids living on an Erigeron<\/em> that looked like U. (L.) zerogutierrezis<\/em> — yes, they looked like this species, but with one major exception: the rhinaria on a.s. III were clumped in the basal 2\/3 of the segment rather than on the apical 3\/4 of the segment as in U. (L.) zerogutierrezis<\/em>. Rhinaria concentrated toward the base is the more common feature in Uroleucon<\/em> of the region, including aphids found just meters away. Other examples included specimens that look mostly like U. (L.) erigeronense<\/em> except with a short broad ultimate rostral segment as in U. (L.) zerogutierrezis<\/em>. Or, specimens like U. (L.) erigeronense<\/em> except with tarsi a bit too short and with long spinelike setae ventrally, features in some distinctive species such as the unusual U. (L.) nevadense<\/em> Robinson, which feeds on Brickellia microphylla<\/em>. So, the idea that came to mind was that perhaps what I am seeing is the result of hybridization among what we know of as species of Uroleucon (Lambersius)<\/em> in this region, resulting in a smear of variation and no clear host plant affiliations. Of course I cannot be sure which hypothesis, or perhaps neither, is correct.<\/p>\n\n\n\n

Another indicative point here is the text about U. (L.) zerogutierrezis<\/em> on Blackman and Eastop’s website: “On\u00a0Gutierrezia\u00a0<\/em>sp. in western USA and on\u00a0G. sarothrae\u00a0<\/em>in Mexico (Nieto Nafr\u00eda\u00a0et al<\/em>. 2011). There are also records from\u00a0Bidens<\/em>,\u00a0Senecio<\/em>\u00a0and\u00a0Chrysothamnus<\/em>, but there is possible confusion with\u00a0U. erigeronense<\/em>, to which it is very similar in every respect except the antennal rhinariation.” Personally, I find this species to be very different from U. (L.) erigeronense<\/em>; it is much smaller overall, with short siphuncli that bear unusually large reticulations, and the ultimate rostral segment is unusually short and broad for this genus. So, am I looking at the same species that they looked at? Or, is this species so variable that some samples are wonderfully distinct from U. (L.) erigeronense<\/em> while others are almost indistinguishable? Or, were they looking at some kind of hybrid population? Any of these cases is an indictment of our current understanding of Uroleucon (Lambersius)<\/em> species.<\/p>\n\n\n\n

As noted by A.G. Robinson back in the 1980s, the only way to figure out this subgenus in North America will be to get accurate host plant identifications, to species, on every collection, and to make detailed color notes and conduct host plant transfers among hosts.<\/p>\n\n\n\n

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Species covered below (click on the name to jump to that species):<\/h2>\n\n\n\n