The same but different!
An aggregate or complex species is generally classified as a grouping of closely-related species that are treated like a single species for practical purposes. One example is a very common plant that is familiar to everyone; the Dandelion Taraxacum officinale
As the above pictures demonstrate, the common Dandelion is tremendously variable and the reason for this is that of instead of being a single species it is in fact an aggregate made up of over 200 micro-species in the UK alone. The leaf shape particularly varies tremendously. This can be simple differences in size or colour but can also be in the overall structure of the leaf. The large backward curving lobes which give the plant its name “Dente de Lion”, Lion’s Tooth can be really pronounced as in the top images or almost absent (see picture below).
The plants depicted above were all growing within 3 metres of each other along a kerb. Below is some of their individual leaves side by side for comparison.
Despite their great variability what is remarkable is that all of them are clearly identifiable as Dandelions! Most of us are so familiar with the plant that we can recognise it straight away despite it’s range of disguises, and regardless of their differences all can be used in the same way for edible and medicinal purposes.