園芸学部構内と千葉県北西部におけるチョウ類群集と種構成に基づく自然環境評価の試み

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1.園芸学部構内を含む千葉県北西部各所においてチョウ類群集の定性調査ならびに既存の記録との比較を行った.その結果, 園芸学部構内からは森林性種, 年間発生回数が少ない種, 狭食性の種の多くが消失していることが明らかとなり, その要因は園芸学部における人為的撹乱によるものと推察された.2.チョウ類の共通度は各調査地間の距離が近いほど, 過去の記録を含めたときほど高くなった.これは都市域から過去に衰退した種類も都市からの距離が離れるにつれて出現するために生じた結果であり, 近年多くのチョウ類が都市部から序々に消失したことが示された.3.都市部から消失するチョウ類の多くは森林性で年間発生回数が少なく狭食性であった.4.千葉県レッドデータ種の多くは年間発生回数が少なく, 狭食性であり, 園芸学部からは確認されなかった.これらのレッドデータ種の多くは局所的・希薄的, もしくは都市からの減少傾向が認められ, 都市から離れるにつれて多く出現する傾向が認められた.5.レッドデータ種以外にも都市下では減少傾向を示す種がみられ, これらの中には多化性や広食性を示す種も多く認められた.

Butterfly fauna were surveyed from 2000 to 2002 in northwestern area of Chiba prefecture in southern Kanto plain. To evaluate the effect of human disturbance or landscape utilization on the butterfly communities, observations were conducted through years at the campus of Faculty of Horticulture, Chiba University in Matsudo, Chiba prefecture (site Engei), urban park in the city (site Sendabori) and residential deciduous forest in Tsuchiura city, Ibaraki prefecture (site Otto). Mowing or landscape manipulation was operated in forest and grassland area and in forest edge in Engei and Sendabori, respectively. In Otto, though neibouring forests were exploited by house building, no direct manipulation was operated inside the observation forest The degrees of human impacts of landuse on sites were Engei>Sendabori>Otto. Degrading patterns of butterfly communities and ecological characteristics of species disappearance in the region were clarified by comparing our census data and survey records since 1990 from the neighboring sites. Total 33, 46 and 46 butterfly species were observed at site Engei, Sendabori and Otto during surveys, respectively. Many forest species, including univoltine and oligophagous (seasonal and habitat specialist), inhabited in Sendabori and Otto but few in Engei. Meanwhile, grassland species, including many multivoltine and polyphagous species (seasonal and habitat generalist), were abundant in Engei and Sendabori but few in Otto. Frequencies of the observed of the species varied among sites. In Sendabori, the numbers of forest edge species, e.g. Daimio tethys, were fluctuated during observation, whereas in Engei both forest and grassland species, e.g. Papilio bianor and Papilio machaon, fluctuated. In Otto, though grassland species were less abundant many forest seasonal and habitat specialists were observed. These results suggested that human impact, e.g. mowing, might be affect the stabilities of annual occurrence of butterfly species, and therefore many seasonal and habitat specialists were el

source:The technical bulletin of Faculty of Horticulture, Chiba University