Tag Archives: apples

A rose by any other name – In praise of the Rosaceae

I’ll start with a question. What do Lady’s Mantle, Great Burnet, Agrimony, Mountain Avens, Cotoneaster, cinquefolil (Potentilla), strawberries, raspberries, cherries, sloes, apples, rowans and almonds all have in common? The answer may come as a surprise to many; they are all members of the Rose family. This may shcok some of you, but I don’t have a great deal of time for the domesticate hybrid tea roses so common in many gardens.

Hybrid tea rose – looking nothing like the real roses

I think they’re vastly overrated and as many varieties do not produce pollen or nectar as far as insects are concerned they are a waste of space. My experience of working on members of the Rosaceae arose as a by-product of working on the bird cherry-oat aphid, the primary host of which is the bird cherry, Prunus padus (Leather & Dixon, 1981), and the bird cherry ermine moth, Ypomeuta evonymellus which specialises on the bird cherry (Leather & Lehti, 1982). Strangely, it was my interest in island biogeography, in particular the species-area relationship, that got me hooked on the Rosaceae.  I had noticed while sampling bird cherry trees that relatively few insects attacked them, and so wondered if they were special in some way compared with other species of Prunus, and sure enough using host plant records, they did seem to be less insect friendly than their congeners (Leather, 1985). Having got hooked on counting dots on plant distribution maps and realising that the Rosaceae would be a great plant family to test the idea that the species-area relationship would be improved by confining it to a single family (Kennedy & Southwood, 1984), I embarked on a marathon dot counting and host plant record seeking quest (Leather, 1986).

For the paper, I restricted my analysis to the 59 species that Perrings & Walter (1962) listed as native or naturalised to the British Isles, but there are of course many more members of the Rosaceae than that to be found in Britain. They are an extremely important plant family both economically and horticulturally speaking, with over 2500 species in 90 genera to choose from (Sytsma, 2016). The Rose family is divided into four subfamilies based primarily on their fruit. The Amygdaloideae, those species characterised by the possession of fleshy stone fruits, almonds, cherries, peaches, plums etc. The Maloideae, trees with pomes, fruits in which the floral hypanthium becomes fleshy, e.g apples and pears. The Rosoideae, which includes species such as roses, and burnets, with dry fruits that do not open (achenes), and the brambles, raspberries and strawberries, which have drupelets, small, aggregated drupes, and finally the Spiraeoideae, species with dry fruits that open on one side (follicles) e.g Spirea, Physocarpus).

Rosaceous fruit

To me, however, the thing that makes a rose a rose, is the flower. Typically, rose flowers have five sepals which are easier to see before the flowers open and five petals, although there are always some exceptions; for example, Mountain

Sepals for the uninitiated; luckily I have a rose bush that seems to be able to flower all the year round (this picture taken October 28th)

Avens, Dryas octopetala, which as the name tells us, has eight petals but still manages to have that rose ‘look’.

Dryas octopetala an exception that proves the rule J By Jörg Hempel, CC BY-SA 3.0 de, https://commons.wikimedia.org/w/index.php?curid=28317727

As you might expect from a family that has produced the much loved (but not by me) hybrid tea roses, not all the flowers are white, even within the same species, brambles for example, range from the ‘normal’ white to rich

Pink hedgerow brambles, Sutton, Shropshire September 2020.

pinks, and many of the herbaceous members have bright yellow (e.g. Agrimony and Wood Avens) or orange (e.g Water Avens) flowers.

Delicate herbaceous plants with white and yellow flowers.

White flowers do, however, seem to be the rule in the woodier members of

Shrubby bushes with white flowers.

the family, although pink shading is not uncommon.


Tall fruity trees with white flowers some with pink hints.

The ways in which the flowers are presented can also vary between species, single flowers being the exception rather than the rule.

Cloudbursts (corymbiform panicle),  racemes and compound cymes, but still roses. Fun fact, Meadowseet, Filipendulal ulmaria, is rich in salicylic acid and can be used to cure headaches.

I hope you’ve enjoyed this ramble through the roses as much as me, but finally, as an entomologist, it would be remiss of me not to point you at one or two spectacular examples of insect-rose interactions.

References

Kennedy, C.E.J. & Southwood, T.R.E. (1984) The number of species of insects associated with British trees: a re-analysis. Journal of Animal Ecology, 53, 455-478.

Leather, S.R. (1985) Does the bird cherry have its ‘fair share’ of insect pests ? An appraisal of the species-area relationships of the phytophagous insects associated with British Prunus species. Ecological Entomology, 10, 43-56.

Leather, S.R. (1986) Insect species richness of the British Rosaceae: the importance of host range, plant architecture, age of establishment, taxonomic isolation and species-area relationships. Journal of Animal Ecology, 55, 841-860.

Leather, S.R. (1991) Feeding specialisation and host distribution of British and Finnish Prunus feeding macrolepidoptera. Oikos, 60, 40-48.

Leather, S.R. & Dixon, A.F.G. (1981) Growth, survival and reproduction of the bird-cherry aphid, Rhopalosiphum padi, on it’s primary host. Annals of Applied Biology, 99, 115-118.

Leather, S.R. & Lehti, J.P. (1982) Abundance and distribution of Yponomeuta evonymellus (Lepidoptera,Yponomeutidae) in Finland. Notulae Entomologicae, 62, 93-96.

Perring, F.J. & Walters, S.M. (1962) Atlas of the British Flora. BSBI Nelson, London & Edinburgh.

Sytsma, K.J. (2016) Rosaceae, Encyclopaedia Britannica.

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Not all aphids live on leaves

I haven’t written about aphids for a while, so I thought I would indulge myself and tell you about a few of my favourite aphids.  Most people’s perceptions of aphids (assuming that they know what  aphids are of course) is that they live on leaves.  They will I think, also possibly know that they are usually found on the undersides of leaves, although I may be assuming too much here.  In fact, many species of aphid do not live on leaves; a number of species feed on shoots, twigs and branches and some actually feed on the main trunks of trees.  Yet other species live on the roots of trees and herbaceous plants, such as the apple-grass aphid, Rhopalosiphum insertum which can be a pest of apples and cereals, feeding on the leaves and buds of apples and the roots of grasses and cereals.   Another root-feeding aphid that is a double pest, is Pachypappa tremulae, the spruce root aphid, which host alternates between the aerial parts of aspen trees and the roots of Norway spruce; easily visible when infesting the roots of young potted plants due to the presence of white waxy tufts on its rear end.

Some aphids not only live underground feeding on roots, but are entirely dependent on being farmed by ants e.g.  Tetraneura ulmi, which host-alternates between elm and grass roots, and  Forda formicaria, which host-alternates between Pistachio trees and grass roots.

Forda_formicaria_hirsuta_root_aphid_03-03-13_3

http://www.aphotofauna.com/images/bugs_homoptera/bug_forda_formicaria_hirsuta_root_aphid_03-03-13_3.jpg

Both these aphids are looked after or ‘farmed’ by the yellow meadow ant Lasius flavus in exchange for donations of honeydew.

Lasius%20flavus%202

These two aphid species, along with a number of others, have an enlarged anal plate surrounded by special hairs that form the so-called trophobiotic organ.  This acts as a storage device that allows the aphid to accumulate honeydew ready for the ants to remove.  Those aphids that have a more casual (facultative) relationship with ants, do not have this organ which is the basis of this remarkable mutualism.

Another aphid that is farmed by ants, but in a somewhat different way, is the rather larger rose root aphid, Maculolachnus submacaula, which as its name suggests, feeds on rose roots.  In this case, the ants allow the aphids above ground but only in an ant tunnel, similar to those produced by termites when they are infesting a building.  I have only ever been lucky enough to see this aphid once, some 35 years ago in Norwich when I was doing my PhD and noticed things that looked like termite trails running up the main stem of one of my rose bushes.  On breaking them open, well I am a curious entomologist, I found to my surprise not only ants but large brown aphids.

Maculolachnus submacula nest

http://jardiweb-floralbum.forumsactifs.com/t1797-colonie-de-pucerons

for a better view of the aphid see http://www.afripics.co.za/home/products/product.php?ProductID=1301564582

But of course the really spectacular ones are those that feed on branches of trees such as the giant willow aphid Tuberolachnus salignus (famous for its sharks fin) and those from the genus Stomaphis which feed through the bark of trees such as oak and

Tuberolachnus

sycamore and are possessed of truly enormous mouthparts such as those of Stomaphis aceris which feeds on sycamore

Stomaphis query aceris

This one, despite its enormous mouthparts, is quite difficult to find as it hides underneath the bark, but luckily it is ant attended so if you see ants scurrying around on the bark of sycamore and disappearing underneath loose flaking bits, it is a good bet that if you gently lever off the loose bark you will find yourself in the presence of this weird-looking creature.

The more I learn about aphids the more I find to marvel at.  Aphids really are remarkable and we know so little about so many of them and their weird and wonderful life styles.

Useful References

Blackman, R.L. & Eastop, V.F. (19 94) Aphids on the World’s TreesAn  Identification and Information Guide.  CABI Publishing. http://www.aphidsonworldsplants.info/index.htm

Evenhuis, H.H. (1968)  The natural control of the apple grass aphid,  Rhopalosiphum insertum, with remarks on the control of apple aphids in general in The Netherlands. Netherlands Journal of Plant Pathology, 74, 106-117  http://link.springer.com/article/10.1007/BF02309501#page-1

Farrell, J.A. & Stufkens, M.W. (1989) Flight activity and cereal host relationships of Rhopalosiphum spp. (Homoptera: Aphididae) in Canterbury New Zealand Journal of Journal of Crop and Horticultural Science, 17, 1-7  http://www.tandfonline.com/doi/abs/10.1080/01140671.1989.10428003

Ivens, A.B.F., Kronauer, D.J.C., Pen, I., Weissing, F.J. & Boomsma, J.J. (2012)  Ants farm subterranean aphids mostly in single clone groups – an example of prudent husbandry for carbohydrates and proteins?  BMC Evolutionary Biology, 12:106 http://link.springer.com/article/10.1186%2F1471-2148-12-106

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