PATTERNS OF DIVERSIFICATION IN PHYTOPHAGOUS INSECTS

documented, since larvae in leaf mines are often easily located and reared. Over 140
plant families are attacked, including most major plant groups (Spencer 1990, Benavent-
Corai et al. 2005), but hosts are primarily those with herbaceous growth form. Some
agromyzids are important pests of agricultural and ornamental plants (Spencer 1973).
Unlike many insects, Agromyzids are more diverse in temperate than tropical regions;
this is especially true of the largest genus, Phytomyza, which includes over 630 described
species, almost entirely in the temperate northern hemisphere. Spencer (1990) noted that
Phytomyza species exhibit a strong association with the “primitive” plant family
Ranunculaceae (buttercup and columbine family), and hypothesized that the ancestral
Phytomyza species was associated with this plant family. Later shifts to more derived,
diverse herbaceous plant families such as Asteraceae (daisy family) may have further
accelerated species diversification.
This dissertation begins with a general overview of phylogenetic patterns found in
recent literature on phytophagous insects (Chapter 2). Next, this study aims to use DNA
sequence data to estimate phylogenetic relationships within Phytomyza, and then use the
results to update the classification of the genus and comment on the evolution of certain
life history traits (Chapter 3). The phylogeny will then be used to study patterns of host
shift between plant families in Phytomyza and to test Spencer’s hypothesis of an ancestral
association with the Ranunculaceae (Chapter 4). Using fossils to calibrate divergence
times on the molecular phylogeny, events in the evolution of Phytomyza will finally be
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