New butterfly species discovered in Ireland

20/07/2011 22:37:27

Discovery of New Wood White Species - By kind permission of Butterfly Conservation Ireland & Jesmond Harding

July 2011.  Butterfly Conservation Ireland are reporting that, following a new study of wood white butterflies in Ireland and other parts of Europe, a new ‘cryptic' species of Wood white has been identified by DNA tests.

In the late 1980s a new European species of Wood white butterfly was discovered when Leptidea sinapis (Wood white) was found to "hide" a cryptic species, Leptidea reali, or Réal's Wood White. The 2 species are separable based on their genitalia. Both species live in the same geographical area, the Palaearctic: region comprising Eurasia north of the Himalayas, North Africa and the temperate part of the Arabian Peninsula, and the distribution of reali is almost as wide as that of sinapis. Previous studies of the behavioural and ecological aspects of L.sinapis and L.reali show that:

• Females only accept as mates males of their own species,
• Only small ecological differences exist (larval foodplant preferences),
• Differing niche preferences of the 2 species is not caused by their being separate species
• Differences in phenology (e.g. when a larva pupates, when the adult flies etc) and voltinism (number of generations in a year) are mostly caused by the effect on the butterfly of its environment
• The female tendency to mate is influenced by its response to environmental conditions.

In the study by Dinca et al molecular data, chromosome data and male genitalia shape was used to study the species pair Wood White and Réal's Wood White. When doing this work it was discovered that L. reali consists of 2 species identical in appearance yet genetically and karyologically distinct (i.e. containing differing numbers of chromosomes/chromosomes differing in appearance).

Analysis of Mitochondrial & Nuclear DNA Markers
Results of recent tests showed that specimens identified on the basis of genitalia as L. reali, consist of 2 separate species (each with its own ancestor) and that both were descended from the same common evolutionary ancestor as L. sinapis.

L. reali was found to occur in Spain, Italy and Southern France. Leptidea juvernicanov stat which is the name given to the new species was found in samples from several countries ranging from Ireland and France in the west to Kazakhstan in the east.

Samples revealed that L. reali and L. juvernica nov stat do not occur in the same areas but they do occur in adjacent areas in South-eastern France, separated by 87 kms. No evidence of hybridisation was found in this area of France, or elsewhere.

Morphological Analysis

Measurements of genitalia for the three species were compared but only L. sinapiswas clearly distinguished based on these measurements. L .juvernica and L .reali could not be separated based on genitalia. This explains why juvernica remained unnoticed for so long.

The report proposes the common name "Cryptic Wood White" for Leptidea juvernica.

Ancestry of Wood white species
The relationships between the 3 species suggest that the common ancestor of the 3 may have come from Central or Western Asia. This ancestor spread over Western Europe.
About 270,000 years ago, probably in south-western Europe, ancestor A speciated (evolved into a new species) producing ancestor B and L.juvernica. Then about 120,000 years ago, Ancestor B diverged into sinapis and reali.

About 27,000 years ago, L. sinapis expanded north and east into the territory of L. juvernica. Therefore L. reali and L. juvernica do not overlap in distribution. Why L. reali and L. juvernica do not coexist (if this is true) is unknown. Both use the same larval food plant, Meadow Vetchling (Lathyrus pratensis), so ecological differences between the two are minimal. More research is needed to identify distribution, conservation status and ecology.

What the study means for Irish wood whites
A number of Irish specimens were analysed. All the specimens from the Burren or from limestone habitats (e.g. Dromore Wood) were identified as the Wood White (Leptidea sinapis).

All the specimens from outside The Burren and limestone habitats (e.g. Kilternan, County Dublin, Pilgrim Road, County Offaly) were identified as Leptidea juvernica. The population of wood whites identified as L. juvernica that is closest to Ireland is found in South-eastern France. Wood whites found in the north of France might turn out to be L. juvernica. L.reali occurs in Northern Spain but none of the Irish specimens were identified as reali and taken together with the report's analysis of ancestry the existence of reali here appears unlikely. It is likely that reali will be replaced on the Irish list by juvernica.

The continental population of wood whites identified in the report as L. sinapis that is closest to Ireland also occurs in South-eastern France as well as in Southern and South-eastern Europe. It will be interesting to see if wood whites in Northern France turn out to be L. sinapis. According to Jeremy Thomas the wood white found in England and Wales is L. sinapis.

By Jesmond Harding. Click here to se ethe full article on the Butterfly Conservation Ireland website