Eriogonum spergulinum, the Spurry Buckwheat | Catalogue of Organisms

Wandering around sandy highlands of the southwest United States, you may encounter a sparse, wiry weed growing between five and forty centimetres in height. This is the spurry buckwheat Eriogonum spergulinum.

Spurry buckwheat Eriogonum spergulinum, copyright Dcrjsr.

Members of the buckwheat family Polygonaceae are found worldwide but tend to be easily overlooked as low, scrubby weeds. In North America, one of the most diverse genera is Eriogonum, known from about 250 species though many are difficult to readily distinguish (Hickman 1993). Eriogonum spergulinum is one of the more recognisable species in the genus. As mentioned above, it grows in sandy soils, particularly those dominated by worn-down granite, and is found at altitudes between 1200 and 3500 metres. It is an annual herb with basal leaves of a linear shape, less than two millimetres wide but up to thirty millimetres long. The greater part of the plant's height is made up by the slender, cyme-like inflorescence bearing unribbed, four-toothed involucres on slender stalks. The flowers are up to three millimetres in diameter with a white perianth marked by darker stripes. Overall, E. spergulinum in flower resembles a drifting cloud of small white stars.

Close-up on Eriogonum spergulinum flowers, copyright Tom Hilton.

Three varieties of Eriogonum spergulinum have been recognised though they are not always distinct and tend to intergrade with each other. In most parts of the species' range, plants belong to the variety E. spergulinum var. reddingianum. This variety is characterised by erect inflorescences with glandular axes and flowers about two millimetres in diameter. The other two varieties are both restricted to the Sierra Nevada mountains of California. Eriogonum spergulinum var spergulinum resembles var. reddingianum but produces larger flowers, about three millimetres in diameter. Eriogonum spergulinum var. pratense is more distinctive. Inflorescences are prostrate to ascending, only about two to five millimetres in height, and lack glands on the axes. Flowers are only 1.5 millimetres across. Pratense is also a higher-altitude variety, found at heights above 2500 metres. The Sierra Nevada varieties are both uncommon; if any variety is likely to be found, it is the widespread reddingianum.

REFERENCE

Hickman, J. C. (ed.) 1993. The Jepson Manual: Higher Plants of California. University of California Press: Berkeley (California).

Scaleyness is Next to Diatom-ness | Catalogue of Organisms

The last few decades have seen significant advances in our understanding of microbial diversity. Consistent improvements in available technologies and methods for study, both molecular and ultrastructural, have allowed researchers to look further and deeper than they ever could before. Not only have they identified taxa that were previously unknown, they have been able to develop a much better understanding of how microbial taxa relate to each other. Among the fields that has seen particularly remarkable advances has been the study of the picoplankton, that component of the marine plankton comprising organisms less than two or three microns in size. Much of the picoplankton, of course, is made up of bacteria but another significant component is species of microalgae belonging to the group known as heterokonts or stramenopiles.

Schematic diagram of motile bolidophyte cell, from Guillou et al. (1999).

Heterokonts are a major clade of eukaryotes that are commonly characterised by cells bearing anterior pairs of morphologically distinct cilia. One of the cilia is longer and bears rows of hairs referred to as mastigonemes; the other, shorter cilium is usually smooth. Many heterokont species are photosynthetic and belong to a subclade of the heterokonts known as the ochrophytes. For most people, the best known ochrophytes will be the often-decidedly-not-microbial brown algae such as kelps. However, ochrophytes also include a broad diversity of microbial forms. Most ochrophyte cells share a characteristic golden-brown coloration owing to the presence of yellowish pigments such as fucoxanthin as well as the more standard chlorophyll.

Recent molecular studies have supported a division of the ochrophytes between two major clades. On one side are the brown algae and their closer microbial relatives. In the other clade are those ochrophytes more closely related to the diatoms. Appropriately enough, this latter clade was dubbed the Diatomista by Derelle et al. (2016). Other than the diatoms themselves, most representatives of the Diatomista belong to the picoplankton. For the most part, diatoms have lost the cilia otherwise associated with heterokonts. The only exceptions are the reproductive sperm cells which have a single anterior cilium bearing mastigonemes (Adl et al. 2019). The remaining Diatomista commonly have cells bearing one or two anterior cilia (if only one cilium is present, it will typically have mastigonemes). Nevertheless, the basal apparatus of the cilia is reduced, lacking microtubular roots or a rhizoplast, suggestive of an intermediate stage towards total loss (Guillou et al. 1999). Many also bear a covering of silica scales; enlargement of individual scales may have lead to the evolution of diatom-style frustules.

Non-motile cell of Triparma laevis f. inornata, from Kuwata et al. (1987).

The closest known relatives of diatoms are currently classified as the class Bolidophyceae. Motile cells of the Bolidophyceae were first described in 1999 (Guillou et al. 1999). They possessed two cilia, with the haired cilium directed anteriorly and the smooth cilium directed posteriorly, and lacked silica scales. Nevertheless, they were identified as the sister group to diatoms by molecular data. This was corroborated by the absence of a transitional helix structure at the base of each cilium, a feature shared with diatom sperm cells. Guillou et al. (1999) commented on the relatively high mobility of the bolidophytes, in contrast to the general expectation that picoplankton should exhibit a reduction in individual cell mobility owing to the difficulty in meeting energy demands.

The concept of bolidophytes shifted somewhat in the 2010s with the isolation in culture of the Parmales, a group of minute eukaryotes that had first been recognised in the 1980s but had long eluded detailed characterisation. These were non-motile cells enclosed within ornate silica scales. Once molecular data become available, researchers realised that 'Parmales' were not just closely related to 'bolidophytes', they were close enough that the two forms could reasonably be included in a single genus (Kuwata et al. 2018). The exact details of their connection, however, remain uncertain. It seems likely that the flagellate and non-flagellate forms represent alternate forms of single species. But whether we are looking at alternate generations of the life cycle, or whether the flagellate cells are generated in response to particular conditions, remains to be determined.

Skeleton of silicoflagellate Dictyocha speculum, copyright Proyecto Agua.

The remaining members of the Diatomista form a clade currently treated as including three classes, the Dictyochophyceae, Pelagophyceae and Pinguiophyceae. Together they are a diverse array of minute organisms, whether ciliated or amoeboid, naked or carrying organic scales, photosynthetic or heterotrophic or some combination of both. Among the representatives of the Dictyochophyceae are the so-called silicoflagellates, ciliated cells reinforced with a skeleton of (duh) silica. Though only a few species of silicoflagellate are recognised in the modern environment, they have an extensive fossil record extending back to the Middle Cretaceous (Kristiansen 1990). In some places, their preserved skeletons may dominate rock formations. Silicoflagellates appear to have reached their peak in the Miocene, followed by a decline to their modern condition. The exact interpretation of the silicoflagellate fossil record is a long-standing challenge (whether differences in morphology are taxonomic or environmental, for instance) but they hold the potential to tell us much about the history of our seas.

REFERENCES

Adl, S. M., D. Bass, C. E. Lane, J. Lukeš, C. L. Schoch, A. Smirnov, S. Agatha, C. Berney, M. W. Brown, F. Burki, P. Cárdenas, I. Čepička, L. Chistyakova, J. del Campo, M. Dunthorn, B. Edvardsen, Y. Eglit, L. Guillou, V. Hampl, A. A. Heiss, M. Hoppenrath, T. Y. James, A. Karnkowska, S. Karpov, E. Kim, M. Kolisko, A. Kudryavtsev, D. J. G. Lahr, E. Lara, L. Le Gall, D. H. Lynn, D. G. Mann, R. Massana, E. A. D. Mitchell, C. Morrow, J. S. Park, J. W. Pawlowski, M. J. Powell, D. J. Richter, S. Rueckert, L. Shadwick, S. Shimano, F. W. Spiegel, G. Torruella, N. Youssef, V. Zlatogursky & Q. Zhang. 2019. Revisions to the classification, nomenclature, and diversity of eukaryotes. Journal of Eukaryotic Microbiology 66: 4–119.

Derelle, R., P. López-García, H. Timpano & D. Moreira. 2016. A phylogenomic framework to study the diversity and evolution of stramenopiles (=heterokonts). Molecular Biology and Evolution 33 (11): 2890–2898.

Guillou, L., M.-J. Chrétiennot-Dinet, L. K. Medlin, H. Claustre, S. Loiseaux-de Goër & D. Vaulot. 1999. Bolidomonas: a new genus with two species belonging to a new algal class, the Bolidophyceae (Heterokonta). Journal of Phycology 35: 368–381.

Kristiansen, J. 1990. Phylum Chrysophyta. In: Margulis, L., J. O. Corliss, M. Melkonian & D. J. Chapman (eds) Handbook of Protoctista. The structure, cultivation, habitats and life histories of the eukaryotic microorganisms and their descendants exclusive of animals, plants and fungi. A guide to the algae, ciliates, foraminifera, sporozoa, water molds, slime molds and the other protoctists pp. 438–453. Jones & Bartlett Publishers: Boston. Kuwata, A., K. Yamada, M. Ichinomiya, S. Yoshikawa, M. Tragin, D. Vaulot & A. Lopes de Santos. 2018. Bolidophyceae, a sister picoplanktonic group of diatoms—a review. Frontiers in Marine Science 5: 370.

Cup plant feeds brown ambrosia aphid, Uroleucon ambrosiae, which in turn provides dinner for lynx spiders, lady beetles, long-legged flies, flower flies, and green lacewings

 

Colonies of brown ambrosia aphids are manufacturing legions of hungry predators ready to sally forth and feast on other pests in my garden. Although an adult flower fly was not sighted, her telltale egg (inside the circle) in the aphid colony confirms her visit and spells trouble for aphids in just a few days when her predatory larva hatches.

 

One of the best performers in my flower bed is a raucous native plant known as cup plant, Silphium perfoliatum, a premier attractor of insects to the garden. Extravagant floral displays provide nectar and pollen to a wide variety of bees, butterflies, and wasps. Nutrients coursing through vascular vessels support several species of sucking insects including leafhoppers, treehoppers, and aphids. And where there are abundant juicy prey items, there are predators, lots of them.

This little Cycloneda lady beetle has her jaws wrapped around a juicy brown ambrosia aphid.

Early one morning this pretty green lacewing adult stopped by an aphid-infested cup plant. How soon will her meat-eating youngsters appear in the aphid colony?

The featured insect this week is the brown ambrosia aphid, whose populations have exploded on my cup plants. As the name implies, this aphid is found on a wide variety of plants in the Asteraceae family including black-eyed Susan, coneflower, and sunflower in addition to cup plant. Like many of their kin, in summertime these gals are parthenogenic, like the Amazons in Greek mythology, an all-female society reproducing without the assistance of males. One of the most fascinating behaviors found in aphids on my cup plant and other Uroleucon aphids is a synchronized twitching response when the colony of aphids is disturbed. On several mornings last week when visiting the cup plant with a cup of coffee in hand, I was greeted by mass displays of dancing aphids as I approached the plant. Clever studies of a related species of Uroleucon revealed a synchronous “collective twitching and kicking response”, a.k.a. “CTKR”, when an object like a pencil or a predator like a lady beetle was in visual range of the colony. Gentle vibrations of the substrate upon which the colony rested also evoked the CTKR. These coordinated defenses reduced successful attacks by tiny parasitic wasps that use aphids as hosts for their young.

Gentle taps on the cup plant leaf sends the colony of brown ambrosia aphids into paroxysms of synchronized twitching. This behavior may ward-off attacks by tiny parasitic wasps or small predators.

While collective twitching proved effective against some enemies of aphids, colonies of aphids on my cup plant are now besieged by legions of hungry lynx spiders, lady beetles, flower flies, long-legged flies, and lacewings. The synchronized defense of hapless aphids can’t stop these fierce tiny predators from taking their toll. While this is bad news for the aphids, this is good news for my garden. The aphids have become a feeding factory for many species of predators that will move on to other plants in my landscape once the brown ambrosia aphids are kaput, all part of Mother Nature’s plan for a more sustainable landscape. 

Lynx spiders like this male Oxyopes find aphids irresistibly tasty any time of day.

Long-legged flies prowl leaves of cup plant in search of prey.

Acknowledgements

We thank Drs. Gary Miller and Jeff Shultz for identifying prolific brown ambrosia aphids and the cool male lynx spider, respectively. Dr. Paula Shrewsbury created this story by planting silphium and identified the pretty polished lady beetle. The fascinating account of defensive behaviors in aphids entitled “Collective Defense of Aphis nerii and Uroleucon hypochoeridis (Homoptera, Aphididae) against Natural Enemies” by Manfred Hartbauer was consulted to prepare this episode.

Nectar rewards for peony protecting body guards: Carpenter ants, Camponotus spp.

 

Are ants really necessary for peonies to bloom?

 

Given a choice between tending a herd of sap-sucking aphids for their honeydew reward or protecting the peony bud from aphids, the ants are going with the aphids.

One gardening legend has it that peonies don’t flower without the assistance of ants. Well, the editors of the Old Farmer’s Almanac recently busted the myth that ants “tickle the buds” to get peonies to blossom. As they point out, peonies definitely will bloom just fine in the absence of ants. Well, if ants are not helping the buds open, what are they doing? A closer look reveals that plants are clever. They have evolved astounding arsenals of sophisticated defenses to thwart hungry jaws of caterpillars and beetles and the sap-sucking beaks of aphids, scale insects and their kin. Tough leaves, rugged bark, spines, thorns, hooked hairs that snare trespassers, and a veritable warehouse of noxious chemicals designed to poison herbivores protect leaves, stems, and roots of plants. But one of the most elegant defenses in the plant-world involves bodyguards. Yes, plants “hire” insects to protect their tender tissues from ravages of hungry herbivores.

A close look at the peony reveals a drop of nectar secreted by the peony as a reward for guarding the bud.

In previous episodes we met Pseudomyrmex ants, protectors of the bull-horn acacias in which they live. You may recall that at the base of acacia leaves specialized glands called extrafloral nectaries produce sugar-rich nectar, the source of carbohydrates for the ant colony living in the tree. In return for nectar and other nutrients provided by acacia, ants protect their host trees in a deal crafted eons ago by Mother Nature. While fooling around with acacia ants, I learned how potent their defense can be when one delivered a memorable sting. Many trees and shrubs commonly found in our landscapes, including cherry and peach trees, have similar extrafloral nectaries that attract ants and so do the peonies that grow in our gardens. In addition to defense, scientists hypothesize that nectar produced by these glands may simply be a waste product excreted by the plant. Another possibility is that nectar produced by glands on the plant but away from flowers, may lure ants away from blossoms where they might rob floral nectar used to attract pollinators vital for the plant’s reproduction.

To explore the defense hypothesis, I placed a rather large eastern tent caterpillar on a leaf close to several carpenter ants dancing about on a flower bud. As you will see by watching the video, the ants wasted no time attacking the intruder and chasing it from the peony. Just what you would expect any good bodyguard to do. Although ants might not be needed to tickle open the buds of peonies to help them bloom, perhaps by keeping bud and flower-munching insects off the plant, they still play an important role in helping peonies thrive and bring their elegant displays to our gardens.

Do ants really protect peonies from herbivores? Watch as carpenter ants on the flower bud and leaves show an intruding caterpillar the way off the peony plant, taking the valiant defender with it. With the intruder gone, looks like mission accomplished by peony protecting ants.

Acknowledgements

Bug of the Week thanks Dr. Shrewsbury and the editors of the Almanac for providing the inspiration for this episode. The encyclopedic “Insect Ecology” by Peter Price, Robert Denno, Micky Eubanks, Debby Finke, and Ian Kaplan and was used as a reference for this episode.