Importance of Reserves, Fragments, and Parks for Butterfly Conservation in a Tropical Urban Landscape Author(S): Lian Pin Koh and Navjot S
Total Page：16
File Type：pdf, Size：1020Kb
Importance of Reserves, Fragments, and Parks for Butterfly Conservation in a Tropical Urban Landscape Author(s): Lian Pin Koh and Navjot S. Sodhi Source: Ecological Applications, Vol. 14, No. 6 (Dec., 2004), pp. 1695-1708 Published by: Ecological Society of America Stable URL: http://www.jstor.org/stable/4493684 Accessed: 29/09/2010 11:16 Your use of the JSTOR archive indicates your acceptance of JSTOR's Terms and Conditions of Use, available at http://links.jstor.org/page/info/about/policies/terms.jsp. JSTOR's Terms and Conditions of Use provides, in part, that unless you have obtained prior permission, you may not download an entire issue of a journal or multiple copies of articles, and you may use content in the JSTOR archive only for your personal, non-commercial use. Please contact the publisher regarding any further use of this work. Publisher contact information may be obtained at http://links.jstor.org/action/showPublisher?publisherCode=esa. Each copy of any part of a JSTOR transmission must contain the same copyright notice that appears on the screen or printed page of such transmission. JSTOR is a not-for-profit service that helps scholars, researchers, and students discover, use, and build upon a wide range of content in a trusted digital archive. We use information technology and tools to increase productivity and facilitate new forms of scholarship. For more information about JSTOR, please contact [email protected]. Ecological Society of America is collaborating with JSTOR to digitize, preserve and extend access to Ecological Applications. http://links.jstor.org Ecological Applications, 14(6), 2004, pp. 1695-1708 C 2004 by the Ecological Society of America IMPORTANCE OF RESERVES, FRAGMENTS, AND PARKS FOR BUTTERFLY CONSERVATION IN A TROPICAL URBAN LANDSCAPE LIAN PIN KOH AND NAVJOTS. SODHI1 Department of Biological Sciences, National University of Singapore, 14 Science Drive 4, Singapore 117543, Republic of Singapore Abstract. We assessed the effectiveness of forest reserves (i.e., protected old secondary and primary forests), fragments (i.e., scattered ruderal vegetation), and urban parks (i.e., artificially revegetated habitats) in conserving butterfly diversity in a highly urbanized tropical landscape (i.e., Singapore), by testing the hypothesis that forest reserves have the highest butterfly species richness among these habitats. We investigated which environ- mental factors (e.g., canopy cover) affect the distribution of butterflies across the habitats; and also tested the hypothesis that butterfly communities of different habitats have distinct ecological traits. Further, we examined the important determinants (e.g., area) of butterfly richness in urban parks, by testing the hypothesis that the number of potential larval host plant species occurring in the park is the best predictor of butterfly species richness. Rar- efaction analyses showed that forest reserves had the highest number of species, number of unique species, density of species, and community evenness among the habitats, implying that, in urban landscapes, the least human-disturbed habitats should be given the highest conservation priority. Forest reserves and urban parks adjoining forests collectively ac- counted for 91% of all butterfly species recorded in this study, suggesting that their pres- ervation will likely achieve maximum complementarity for effective butterfly conservation. Ordination analyses revealed that different butterfly species responded differently to en- vironmental factors (e.g., canopy cover), highlighting the importance of maintaining en- vironmental heterogeneity for the conservation of different butterfly species. Classification tree analysis indicated that butterfly communities of different habitats (e.g., forests, urban parks) have distinct ecological traits (e.g., host plant specificity), whereby urban avoiders were 89% likely to be forest dependent and 63% likely to be monophagous, while urban adapters were 87% likely to be cosmopolitan and 67% likely to be oligo- or polyphagous. Regression analyses showed that the number of potential larval host plant species and isolation from forests were important determinants of butterfly species richness in urban parks, indicating that urban parks should be revegetated with a diversity of potential larval host plants and should be situated as near as possible to a forest, in order to maximize their conservation value. Key words: biodiversity; butterfly conservation; classification tree; conservation value; ordina- tion; rarefaction; reconciliation ecology; Southeast Asia; urbanization. INTRODUCTION Human Settlements 1996), urban ecology has received little Forests are being lost at an alarming rate across the relatively emphasis from conservation biologists world's tropical regions (Achard et al. 2002). Among (McKinney 2002, Ormerod et al. 2002, Lim and Sodhi the anthropogenic causes of deforestation, urbanization 2004). Miller and Hobbs (2002) attribute this to the is expected to be a major determinant of species loss traditional focus of conservation research on "natural" (Kowarik 1995, Marzluff 2001, McKinney 2002, Mill- ecosystems (e.g., primary forests) to preserve and pro- er and Hobbs 2002). Unlike other forms of habitat dis- tect them from human settlements and activities. How- turbance (e.g., logging), where forests may regenerate ever, the economic and political constraints of pre- over time through ecological succession (Sheil and serving large tracts of pristine habitats, as well as the Burslem 2003), urbanization often irreversibly replaces rapidity and ubiquity of urban sprawl have galvanized natural habitats (e.g., primary forests) with persistent some ecologists to rethink the traditional conservation artificial ones (e.g., human cities), resulting in long- strategies of reserving and restoring natural habitats lasting negative impacts (e.g., species extinctions) on (Dale et al. 2000, Miller and Hobbs 2002, Daily 2003, the native biodiversity (Stein et al. 2000). Although Rosenzweig 2003). Instead, they argue that conserva- human settlement has become the globally prevailing tion planning should include reconciliatory measures source of land use Nations Centre for change (United that encompass a wider range of land uses (e.g., urban areas), so that human activities can with min- Manuscriptreceived 29 August 2003; revised 4 February proceed 2004; accepted9 April2004. CorrespondingEditor: J. A. Logan. imum displacement of the native species. For example, 1 Correspondingauthor. E-mail: [email protected] in addition to preserving as many remnant natural hab- 1695 1696 LIAN PIN KOH AND NAVJOT S. SODHI Ecological Applications Vol. 14, No. 6 itats (e.g., forest reserves) as possible, the creation and native and exotic cultivated flora (Teo et al. 2003). They maintenance of artificially revegetated habitats (e.g., function as "green spaces" in densely populated urban urban parks), where certain native species can persist residential and commercial areas. As forest reserves (Kendle and Forbes 1997), may be a viable conser- are the least human-disturbed of these habitats (Turner vation strategy in highly urbanized landscapes. et al. 1994, Corlett 1997), we test the hypothesis that Recent studies investigating the ecological impacts forest reserves are most effective in conserving but- of urbanization in mostly temperate regions have terfly species richness, by comparing the number of shown distinct changes in species richness and com- species, number of unique species, density of species, position along rural-urban gradients; local extinctions density of individuals, and community evenness among of native species; increases in the number of exotic the different habitats. Second, we examine how the species toward centers of urbanization; and the persis- distribution of butterflies may be affected by environ- tence of certain native species in urban areas (e.g., mental factors (e.g., canopy cover) and ecological traits Kowarik 1995, Blair and Launer 1997, Hardy and Den- (e.g., larval host plant specificity). We investigate nis 1999, Marzluff 2001). A current challenge is to which environmental factors (e.g., canopy cover) affect understand the differential response of individual spe- the distribution of butterflies across the habitats; and cies to urbanization, including their underlying mech- also test the hypothesis that butterfly communities of anisms, in order to identify vulnerable species and to different habitats have distinct ecological traits. Third, develop effective measures for their conservation. Fur- we examine the important determinants of butterfly ther, it is critical to evaluate the effectiveness of dif- species richness (e.g., area) in existing urban parks to ferent habitats (e.g., artificially revegetated urban improve future park design and management for ef- parks) in maintaining the diversity of native species in fective butterfly conservation. As previous studies have urban landscapes. shown butterflies to be closely associated with their With Southeast Asia's rapid economic development, larval host plants (e.g., Koh et al. 2004), we test the urban areas will likely be an important, if not dominant, hypothesis that the number of potential larval host plant feature of the regional landscape. Since Southeast Asia species occurring in the park is the best predictor of has one of the highest global concentrations of endemic butterfly species richness. We believe that our study species (Myers et al. 2000) and is predicted to lose up can contribute