Ecological and biogeographical effects of forest disturbance on tropical butterflies of Sumba, Indonesia

Abstract

Butterfly assemblages within lowland monsoon forest were compared at four sites on Sumba, Indonesia that differed in terms of protection and exhibited associated differences in levels of human disturbance. A numerical method employing principal components analysis was devised for describing forest structure at each site. The first principal component (PRINI) grouped attributes tending towards dense forest with closely-spaced trees, a closed canopy and a poorly developed field layer, with trees that tended to be large with the point of inversion in the upper half of the trunk. The highest values for PRINI were recorded within protected forest, and PRINl values were considered to be a useful index of forest disturbance at each site. Species diversity of butterflies was highest in unprotected secondary forest. but was not affected by lower levels of disturbance. Those species occurring at highest density in secondary forest generally had wide geographical distributions, whereas those species occurring at highest density in undisturbed primary forest had restricted ranges of distribution, in most cases with a separate subspecies on Sumba. Overall, an index of biogeographical distinctiveness decreased with increasing disturbance, and this supports the hypothesis that the most characteristic species of undisturbed climax forest have the smallest geographical ranges of distribution. Species abundance data for butterflies fitted a log-normal distribution at all but the most disturbed site. These results indicate that the pattern of proportional abundance of tropical butterfly species may be used as an 'instantaneous' indicator of forest disturbance, and that changes in the structure of tropical forests in S.E. Asia resulting from human disturbance, even within partially-protected forest, may result in the presence of butterfly assemblages of higher species diversity but of lower biogeographical distinctiveness, and therefore of lower value in terms of the conservation of global biodiversity.

Aquatic insects indicate terrestrial habitat degradation: changes in taxonomical structure and functional diversity of dragonflies in tropical rainforest of East Kalimantan

“…However, overall species richness may not change at the local scale or can be even higher with growing intensity of disturbance (Hamer et al 1997;Shahabuddin et al 2010). Human-induced disturbances in the rain forest therefore result in pronounced changes in species composition and an overall reduction in species diversity.…”

Rainfall but not selective logging affect changes in abundance of a tropical forest butterfly in Sabah, Borneo

“…What appears more certain is that species with restricted distributions are particularly vulnerable to habitat disturbance (Hamer et al 1997, Hill et al 1995. Ragadia makuta has a relatively restricted geographic distribution (Borneo, Sumatra, Java and Malay Peninsula), and is dependent on forest, suggesting that it might be vulnerable to selective logging.…”

“…Observation stations were marked at 100-m intervals along transects and there were two transects in each habitat (unlogged forest: 41 stations, transects 1 and 2, total length 4.3 km; logged forest: 40 stations, transects 3 and 4, total length 4.2 km). Butterflies were surveyed along transects using a combination of point-count techniques and walk-and-count techniques modified from methods developed in temperate regions by Pollard (1977), and were similar to methods used in previous tropical studies (Hamer et al 1997, Hill 1999, Hill et al 1995. All butterflies observed during a 5-min period were recorded within a 10-m radius of stations, and all butterflies seen within 5 m either side of the path were also recorded while a single observer was walking between stations.…”

Bioindicadores ambientais: insetos como um instrumento desta avaliação

“…O desmatamento tem sido um dos fatores que afetam a riqueza, a abundância e a uniformidade da fauna de lepidópteros em florestas tropicais (Hill et al, 1995;Spitzer et al, 1997). Entretanto, o hábito herbívoro desses insetos leva a comportamentos e respostas diferenciados, muitas vezes dificultando o isolamento dos fatores responsá-veis pelos distúrbios (Wood & Gillman, 1998;Hammer et al, 1997).…”