Dt. Briese et al., STRUCTURE OF THE PHYTOPHAGOUS INSECT FAUNA OF ONOPORDUM THISTLES IN THE NORTHERN MEDITERRANEAN BASIN, Biological Journal of the Linnean Society, 53(3), 1994, pp. 231-253
Thistles of the genus Onopordum (Asteraceae: Cardueae) have become ser
ious weed problems in parts of Australia and North America following i
ntroduction from their native Eurasian ranges, and are the target of a
biological control programme in Australia. This paper analyses the re
sults of three separate surveys of insects Feeding and breeding on thi
stles of the genus Onopordum in the Mediterranean region. Of the 129 s
pecies found feeding, 74 species also bred on these thistles. Endophag
es comprised 54% of the breeding insects, with species that fed in the
capitula and within the rosette crown/root area predominating. The Co
leoptera and Hemiptera were the dominant endophage and ectophage taxa,
respectively. Differences in the Onopordum fauna were noted between h
ost species and between geographic regions, but this was largely due t
o the generalist component of the fauna. Onopordum specialists showed
little variability across regions or between different species within
the host genus. On comparing the fauna of Onopordum with that of other
thistle genera, it was suggested that plant-herbivore interactions be
tween Onopordum and its fauna are less highly evolved, in that there i
s less host specialization and a lesser degree of niche partitioning.
This appears to be related to the low rate of speciation and habitat s
pecialization within the host genus itself. The potential of certain g
enus-specific insects as biological control agents for Onopordum spp.
is discussed. It is argued that the absence of a high degree of niche
specialization could favour successful biological control, as the agen
t would be capable of inflicting damage over a wider range of resource
gradients.