Title:
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The analysis of sub-fossil insect assemblages : a numerical approach
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The application of numerical techniques within palaeoentomology has been
sporadic and of a largely simplistic nature. In particular, the assessment of
faunal similarity has relied mainly upon subjective value judgements;
similarly, the reconstruction of past climates using fossil Coleoptera has
been undertaken with only a limited application of numerical methods. This
thesis presents a computational approach to these problems.
Although the intrinsic properties of palaeoentomological sample units impose
limitations on the validity of a statistical analysis of faunal similarity,
the use of such techniques is fully justifiable. Several methods have been
tested with a wide range of data, using intuitive interpretations as reference
standards. Binary data, in conjunction with a limited combination of
clustering techniques and resemblance coefficients, produce results which
compare favourably with the traditional assessments; numeric data and
Principal Components Analysis are useful in difficult analytical situations
and / or when particularly complex questions are being asked.
To enable palaeoclimatic reconstructions to be produced quickly and accurately
a computer package of Fortran programs has been written and implemented. By
representing the geographical range of a beetle on climatic axes it is
possible to derive estimates of the past thermal climate from an assemblage
of fossil beetles. Using the Mutual Climatic Range Reconstruction Package the
thermal climate of Britain during the Late Quaternary has been examined in
detail. The pattern correlates with that derived from ocean care data, being
characterised by abrupt changes between contrasting climatic states.
The climatic reconstruction methodology has been inverted to provide a means
whereby potential coleopteran faunas can be derived for particular thermal
climates. In the context of the origin of the invertebrate faunas of the
N. Atlantic Islands, the results of the Pest program provide support for a
glacial tabula rasa followed by immigration via ice rafting at c. 10,000 B. P.,
as opposed to the alternative hypothesis of glacial survival in refugia.
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