Hello again! In the last post we discussed some of the research regarding aphid origins and paleontology, as well as some of the questions that Heie (2009) wanted answering. We briefly covered one of the main influences on aphid evolution – the host plants. In this post I’ll be discussing some of the key points about host plants in regards to aphid evolution and also some interesting things about their unique morphology.
Sit back, close your eyes and imagine you have traveled back to a time where magnificent dinosaurs rule the earth. However, despite what most children’s shows and textbooks will tell you, dinosaurs aren’t the only animals roaming here. Also, don’t close your eyes for too long, the impact of a written article is diminished if it isn’t actually read.
*Photo Credit: Julian Beniers “Clever Girl” (Not the right scene but hey-ho!)
Interactions between insects and their plant hosts can be considered to be very sensitive. This relationship has been used to investigate the evolutionary histories of many insect species, including the aphids. There are two main theories as to how this relationship may have affected the evolution of both parties;
- Speciation via the changing of hosts
The first theory eludes to the evolution of both insect and host at the same time, resulting in similar phylogenetic trees. The second refers to the ‘host parasite’ changing its host a number of times, resulting in a literal change in the characteristics of the host parasite.
Although some aphids aren’t necessarily picky with their choice of host plant, many are still considered to have very specific relationships with them. This can be seen when comparing the diversity of some plant species with the aphids that colonise them. The Compositae (around 19,000 sp.) host over 600 species of aphids, which is similar in number to many other plant groups. This can be compared to other groups such as the Coniferae (around 400 sp.) which hosts around 363 species of aphid. Aphids during the later geographical periods would have originally fed upon ancient gymnosperms as angiosperms had not occurred prior to the Cretaceous. However, the evolution and diversification of flowering plants is often regarded as the defining factor that drove aphid evolution which resulted in the aphids that we see today.
* Geographical Time Scale and Plant Evolution
Another factor that will have affected evolution is that of the aphid life cycles. Aphids are divided into non-host alternating (Autoecious), or host alternating (Heteroecious).
Host alternation is a strategy only adapted in around 10% of aphid species but is thought to have significantly contributed towards the colonisation of a wider range of plants and thus has partially driven the evolution of the aphids. A large number of aphids specialise and only feed on one or a few species of plants, whereas host alternation usually occurs seasonally between a woody winter host plant and a secondary summer host that is usually an herbaceous plant species. This constant shift between hosts may have been a deciding factor for the speciation of some aphids prior to present day taxonomy.
*A) Life cycle of the sycamore aphid, Drepanosiphum platanoidis (Autoecious). B) Life cycle of the bird cherry-oat aphid, Rhopalosiphum padi (Heteroecious).
The Aphididae is made up of around 5000 species. The super family Aphidoidea can be considered as aphids which possess siphunculi or siphuncular pores, which would not have been present in most aphid families that existed prior to or during the Cretaceous. One of the questions Heie asks is “where does the family Lachnidae belong on the phylogenetic tree?” I won’t go too much into aphid Phylogenetics because it would need several posts of its own to even begin to cover it in enough detail. So this will be a very brief overview, which I will return to in more detail in future posts.
Aphids of the family Lachnidae are generally brownish in colour, covered in a dense layer of hairs or setae and are (in most species) ‘farmed’ by ants. The oldest known fossils of this family date to the middle Tertiary and are thought to have originated from temperate regions in the Northern hemisphere. The Lachnidae have been through many changes in their taxonomy through the years (see the table below for a brief history!) but in 2015 a paper was published with some updated information on this group of aphids.
|Taxonomist||Date of Literature||Taxonomy|
|BURMEISTER, 1835||Koch, 1854||Genus – Lachnus|
|HERRICH-SCHAEFFER||Koch, 1857||Family – Lachnidae|
|Baker, 1920||Lachnidae = Tribe within Aphidinae|
|Börner, 1952. Heie, 1980||Family – Lachnidae|
So are the Lachnidae a primitive group of aphids or a relatively young group in the world of aphid phylogeny? Older (pre-1960’s) literature regarded the Lachnidae as one of the more primitive groups of aphids, but Heie (along with others) disputed this, saying that they are in fact one of the more recent divergences. This may be due to a lack of diversity within the Lachnidae up to the later Tertiary compared to its diversity today. Based on morphology, the Lachnidae have also been considered as the sister group of the Aphididae due to similarities in the presence of wax glands, the oval secondary rhinaria and because some species appear to be morphologically similar.
Molecular studies on this family have also found some contradiction in the evolutionary history of the Lachnidae. One study (see Ortiz-Rivas & Martinez-Torres, 2010) looking at a range of aphid species discovered that the Lachnidae are only distantly related to the Aphididae and that they represent one of the earlier branches in aphid phylogenetic history. The other study (see Novàkovà et al. 2013) utilises the aphid symbiont Buchnera and found that the Lachnidae may be the sister group of the Drepanosiphidae, so may originate from a branch in aphid phylogenetics that is very distant from the branch of the Aphididae. The latter results may be due to mutations in Buchnera or cross contamination between individuals over time.
So it seems as if this topic is still up to some debate between the researchers! See Heie, 2015 in the references below for a more thorough examination of this topic 🙂
Aphids: The Evolution Part 2 – Morphology will be released at the beginning of April (once my coursework exams are all finished!). I hope you enjoyed reading, leave me a comment if you have any questions or suggestions!
I hope to see you again soon 🙂
Geographic Time Scale (plant): from https://www.britannica.com/science/Mesozoic-Era
Dixon, A.F. and Kundu, R.A.N.A.J.I.T., 1994. Ecology of host alternation in aphids. European Journal of Entomology. 91(1), pp.63-70.
Heie, O.E. 2015. A theory about the evolutionary history of Lachnidae and comments on the results of some molecular phylogenetic studies of aphids (Hemiptera: Aphidoidea). Polish Journal of Entomology. 84, pp.275-287.
Huang, X.L., Xiang‐Yu, J.G., Ren, S.S., Zhang, R.L., Zhang, Y.P. and Qiao, G.X. 2012. Molecular phylogeny and divergence times of Hormaphidinae (Hemiptera: Aphididae) indicate Late Cretaceous tribal diversification. Zoological journal of the Linnean Society. 165(1), pp.73-87.
Kim, H., Lee, S. and Jang, Y. 2011. Macroevolutionary patterns in the Aphidini aphids (Hemiptera: Aphididae): diversification, host association, and biogeographic origins. Plos One. 6(9), p.e24749.
Labandeira, C.C. and Phillips, T.L. 1996. Insect fluid-feeding on Upper Pennsylvanian tree ferns (Palaeodictyoptera, Marattiales) and the early history of the piercing-and-sucking functional feeding group. Annals of the Entomological Society of America, 89(2), pp.157-183.
Moran, N.A., Kaplan, M.E., Gelsey, M.J., Murphy, T.G. & Scholes, E.A. (1999). Phylogenetics and evolution of the aphid genus Uroleucon based on mitochondrial and nuclear DNA sequences. Systematic Entomology. 24, pp.85-93.
Novàkovà E., Hypša V., Klein J., Foottit R.G., Von Dohlen C.D. and Moran N.A. 2013. Reconstructing the phylogeny of aphids (Hemiptera: Aphididae) using DNA of the obligate symbiont Buchnera aphidicola. Molecular Phylogenetics and Evolution. 68(1), pp.42–54.
Ortiz-Rivas B. and Martinez-Torres D. 2010. Combination of molecular data support the existence of three main lineages in the phylogeny of aphids (Hemiptera: Aphididae) and the basal position of the subfamily Lachninae. Molecular Phylogenetics and Evolution. 55(1), pp.305–317.
Peccoud, J. Simon, J.C. von Dohlen, C. Coeur d’acier, A., Plantegenest, M., Vanlerberghe-Masutti, F. & Jousselin, E. (2010). Evolutionary history of aphid-plant associations and their role in aphid diversification. Comptes rendus biologies. 333(6), pp.474-487.
Recommended: Aphid Ecology, 2nd Edition. A.F.G. Dixon.