Composição e tamanho de faunas associadas a capitulos de compostas

AUTOR(ES)
DATA DE PUBLICAÇÃO

1988

RESUMO

Composition and species richness of phytophagous insects associated with flowerheads of Compositae were investigated in samples of 70 plant species, most of them in the Astereae, Eupatorieae, Heliantheae, Senecioneae and Vernonieae. Sampled plants ranged from highly endemic species to widespread ones To investigate the effect of macrohabitat on the associated faunas, collections included a range of localities ln coastal upland and highland sites (up to 2300 m elevation) in Southeast Brazil, in the States of São Paulo, Rio de Janeiro and Minas Gerais. In alI, 266 samples with a total of 5100 plants were collected. Samples of flowerheads were kept in jars to rear adult insects, These were sorted into morphospecies and identified, almost all to genus. (Agromyzidae) are recorded for the first time in flowerheads in the Western Hemisphere. The main phytophagous groups in flowerheads were Tephritidae, Agromyzidae a11d Cecidomyiidae (Diptera) , Cochylidae, Pterophoridae and pyralidae (Lepidoptera) and Lygaeidae, Miridae and Rhopalidae (Hemiptera); a large number of Curculionidae were collected on flowerheads, but most were only adults feeding externally on the flowers; of the Coleoptera, only Apionidae were included in the analyses. Among Diptera, Tephritidae and Agromyzidae had high species numbers. Cecidomyiidae are probably equally species-rich but could not Approximately 8700 individuaIs were sorted into 112 species, for which more than 800 different host records were obtained in alI. These are mostly new records; some represent first records of the insects. Líríomyza spp. be sorted into specieSi the three families were the most abundant ln flowerheads. Among Lepidoptera the Tortricoidea. especialI y the Cochylidae. were richest in species but Pterophoridae and pyralidae (Phycitinae). with only two common species each. were the most abundant. Patterns of species richness were analysed separately for the most important families (Tephritidae. Agromyzidae and Tortricoidea), orders (Diptera and Lepidoptera), total endophages and total phytophages. Several factors were included in analyses of total species richness per host species: (a) plant tribei (b) number of sampling localitiesi (c) host plant geographical range, grouped in three cl asses i (d) flowerhead size (dry weight) i (e) taxonomic isolation - number of Brazilian species in the same genus or tribe. The number of localities was the main factor affecting total richness of alI insect groupings. Geographical range. alone, was also significantly related to species richnes but, combined with number of locali ties, did not contribute significantly to explain variation in total richness. This indicates that beta di versity 1S a major constituent of total species richness in these phytophagous communities. other factors contributed little to explain variation in phytophagous richness of alI host species, but some insects on plants in some tribes were significantly affected by flowerhead size. The number of related species, at the genus or the tribe leveI, also is correlated both with total and local species richness per host species. This relationship is difficult to interpret because it involves severa 1 distinct factors which however are functionally and statistically correlated: larger tribes also have a wider ecological range and usually have also more species per locality. Higher species richness on larger tribes may be an evolutionary response to larger "evolutionary platforms" (Zwoelfer, 1988) but may equalIy well depend on the dynamic host interchange at a more immediate ecological leveI. Mean local richness is correlated with total richness but not with the number of sampling localities. Plant range shows no significant effect on local phytophagous species richness. Polyphagous and oligophagous species do not use hosts indiscriminately. Affinities and preferences for certain plant groups se em to have an evolutionary historical basis, involving associations with common plants in the center of origin of the insects; these preferences seem to be conserved even in highly different ecological and geographical conditions. The community structure of phytophagous insects in asteraceous flowerheads ln southeastern Brazil is very similar to that of Composites of other geographical regions and shows similar relationships with potential determining factors. Differences between communities of tem~perate and tropical regions are mostly historical and apparently not due to diverging ecological processes

ASSUNTO(S)

inseto florestal ecologia compostas

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