Ecological correlates : endophagous insects and plants in fynbos.
Loading...
Date
1995
Authors
Journal Title
Journal ISSN
Volume Title
Publisher
Abstract
The objective of this study was to investigate endophagous insect species richness in
Fynbos. The influences of plants as determinants of insect occurrence were given special
attention.
The endophagous insects associated with Proteaceae in Fynbos were compared to
endophage assemblages from northern, non-Capensis Proteaceae. The Cape Fynbos
genus Protea is utilized by many more insect taxa than the non-Fynbos species. The high
diversity of host plants in Fynbos appears to have contributed to generating high, local
endophagous insect diversity.
Influences of regional climate, biotope and host-plant characteristics on the frequency
of occurrence of insect borers exploiting Protea species was investigated in Fynbos.
Distinct differences in frequency of encounter of the various insect taxa were recorded
for the various host-plants studied. This variability was primarily accounted for by
physical host-plant characteristics (infructescence and seed-set variables). These findings
have important implications for evolution of insects associated with these plants, as well
as for the conservation of insects and in pest control programmes on indigenous cut
flowers.
The relative species richness of endophagous and ectophagous insects in Fynbos was
compared. Gall-forming insects (Diptera: Cecidomyiidae), were found to be
considerably more speciose than other feeding guilds, showing that the ratio of
endophages to ectophages in sclerophyllous vegetation types is high. The intimate
relationship that endophagous insects have with their host plants tends to habitat
specialization. These insects are therefore likely to undergo radiation together with their
host-plants.
Species richness of gall-insects in Fynbos was investigated to establish whether insect
richness was proportional to plant species richness. The relationship between gall-insect
species richness and plant-species richness was investigated. Fynbos harboured more gall-insect species than other Cape Floristic Region vegetation types. Gall-insect species
richness was positively correlated with plant-species richness. Plant species richness
appears to have contributed to the evolution of a rich gall-insect fauna in the region.
Fynbos gall-insect species richness is comparable to other sclerophyllous vegetation types
globally, underscoring the importance of this vegetation type as a centre of galler
diversification.
Finally, the importance of plant species richness as a determinant of gall-insect species
richness was investigated by comparing different sclerophyllous vegetation types under
the same climatic conditions. Gall were sampled from Fynbos and Karoo vegetation.
Fynbos had higher gall-insect species richness, correlated with plant-species richness.
Plant-species richness, or the distal factors that generated it, appear to have contributed
significantly to the radiation of gall-insects in this region.
Description
Thesis (Ph.D.)-University of Natal, Pietermaritzburg, 1995.
Keywords
Insects--Ecology., Insect-Plant relationships., Galls (Botany), Fynbos ecology., Insects--Host plants., Theses--Entomology.