International Journal of
Biodiversity and Conservation

  • Abbreviation: Int. J. Biodivers. Conserv.
  • Language: English
  • ISSN: 2141-243X
  • DOI: 10.5897/IJBC
  • Start Year: 2009
  • Published Articles: 646

Full Length Research Paper

Ecology and conservation needs of nymphalid butterflies in disturbed tropical forest of eastern Himalayan biodiversity hotspot, Assam, India

Malabika Kakati Saikia*, J. Kalita and P. K. Saikia
Department of Zoology, Gauhati University, Gopinath Bardoloi Nagar, Jalukbari, Guwahati-781 014, Assam, India.
Email: [email protected] rediffmail.com

  •  Accepted: 21 October 2009
  •  Published: 31 December 2009

Abstract

 

We examine the hypothesis, whether the diversity of Nymphalid butterflies in primary forest is related to vegetation structure and canopy openness and that this relationship differs between butterfly taxa in relation to phylogenetic differences in light and shade preferences. The study also examines whether the increasing diversity of butterflies in degraded tropical forest is associated with the loss of species with restricted geographical distribution. Present study has considered eight habitat parameters for habitat data collections and the t-test using equal variance, spearman rank correlation and multiple regressions were used for statistical analyses. Species diversity was analyzed using Margalef’s D indices that indicate both the species richness and abundance. Bootstrap method was used to compare the diversity among samples. PCA was carried out to examine the relationship between vegetation structure and species diversity in primary and degraded forest. The relationship between vegetation factor scores and species diversity at each sampling station in primary and degraded forest was analyzed using stepwise multiple regression. Results indicates that the butterflies species sampled in closed canopy forest had more restricted geographical distribution than those being sampled in disturbed forest. The species with greater light preference had significantly wider geographical distribution, whereas, the species with greater shade preferences had significantly narrower geographical distributions. The stepwise analysis of multiple regressions between the diversity indices of shade groups of butterflies and vegetation density (PRIN1) of closed forest shows a significant positive relationship, but the relationship was negative when similar analysis was performed between species diversity indices of light preferred Nymphalid groups and vegetation density. Results indicate that the greater numbers of closed canopy forest butterflies are sensitive to changes in moisture availability and humidity. Thus, changes in canopy cover and light penetration, through microclimatic effects on adult and larval survival, does have an impact on butterfly distributions. While, the species richness and diversity are higher in forest gaps, the conservation value of close canopy forest lies more in the presence of species with restricted ranges.  Owing to loss of heterogeneous vegetation in degraded forest, the dense canopy cover and transparent ground cover has been reduced and thus declination of forest butterflies species. Study has clearly indicated the strong and significant relationship between the species of narrow range of geographical distribution and species shade preference. The restricted ranges species are affected due to forest degradation. Thus, clearly bringing into light, that increasing diversity in degraded forest is associated with the loss of species with restricted geographical distribution. Out of seven gap preferred shade group of butterflies, two have wide geographical distribution and the other five have medium range distribution. Thus, there is a strong phylogenetic relationship between the genera of light preferred shade loving group of butterflies and the butterflies of light loving group and the genera of shade preferred light loving group of butterflies and the butterflies of shade loving group.

 

Key words: Ecology, closed canopy forests, conservation, degraded forests, endemic species, geographic distribution range, light and shade groups, nymphalid butterflies, phylogeny, tropical forests.