Duke
of Burgundy (Hamearis lucina)
West
Sussex, May 2016
When
it comes to natural selection, we should consider two classes of aberration [a
characteristic that deviates from the ‘normal’ type] - those that are passed
from generation to generation in the species’ genetic make-up, and those, which
are not e.g. those that are determined by the environment. Such
variation may be caused by changes or mutations in the genetic composition as
the individual develops, or to changes in the physical makeup of the individual
as a result of environmental conditions. Aberrations caused by environmental
factors e.g. extremes of temperature, are probably not influenced by natural
selection since they are not part of the gene pool and are therefore not likely to be inherited; this includes certain examples of colouring and markings. Aberrations
may also be the result of a reproduction ‘error’ that is neither genetic, nor
associated with the environment, such as gynandromorphs and hybrids.
Those
aberrations that are carried in the gene pool [and from generation to
generation], and that are visible in terms of colour and markings, clearly do
not provide the population with any advantage otherwise they would be
widespread. This is where the term ‘aberration’ really doesn't stand up to
scrutiny. An individual is considered an aberration if it deviates from the
norm. But if it becomes widespread, it is the norm and therefore no longer an
aberration. A case in point is ab. caeruleopunctata
(Rühl, 1893) in the Small Copper (Lycaena
phlaeas) that has a row of blue spots above the copper marginal band on the
hindwing. It could be argued that individuals without the blue spots are
actually the ‘aberration’ in some populations where this feature occurs frequently.
However, answering the question of why this occurs, these aberrations should
simply be seen, in my opinion, as a reflection of the rich gene pool available
that potentially allows populations to respond to changes in their environment.
2016
has been a good season for aberrant Duke of Burgundy in Sussex. In descending order the above images show a
‘normal’ female, a female referable to ab. albomaculata
(Blachier, 1909), and a rather exciting find of a female currently referable to
ab. gracilens (Derenne, 1927) + ab. albomaculata (Blachier, 1909). However, with
regards to the third individual, albomaculata
is only a hindwing aberration whereas this specimen has the same condition on
the forewings as well. In addition, the spots in the lunules to the forewings
are streaks instead of spots. The underside was also of a paler appearance than
‘normal’. It is therefore quite possible, as none of the existing combinations
of names really cover it, that a new name may be required for this form.
My thanks to Peter Eeles, Alec Harmer and Rupert Barrington for their
assistance.
More
at:
Ford,
E.B. (1945). Butterflies. London: Collins (New Naturalist), pp.
219-247.
Harmer, A.S. (2000). Variation in British Butterflies. Lymington,
Hampshire: Paphia Publishing Ltd., pp. 53-96.
