BIOLOGICAL CONSERVATION Biological Conservation 120 (2004) 471–480 www.elsevier.com/locate/biocon Hotspots, complementarity or representativeness? designing optimal small-scale reserves for biodiversity conservation Vassiliki Kati a,*, Pierre Devillers b, Marc Dufr^ene c, Anastasios Legakis d, Despina Vokou e, Philippe Lebrun f a Department of Environmental and Natural Resources Management, University of Ioannina, Seferi 2, 30100 Agrinio, Greece b Institut Royal des Sciences Naturelles de Belgique, Section de Biologie de la Conservation, rue Vautier 29, B-1000 Bruxelles, Belgium c Ministere de la Region Wallonne, Centre de Recherche de la Nature, des For^ets et du Bois, Avenue Marechal Juin, 23, 5030 Gembloux, Belgium d Department of Biology, University of Athens, Zoological Museum, Panepistimioupolis, 15784 Athens, Greece e Department of Ecology, Aristotle University of Thessaloniki, School of Biology, UPB 119 54124 Thessaloniki, Greece f Universite catholique de Louvain, Unite d’Ecologie et de Biogeographie, Centre de Recherche sur la Biodiversite, Place Croix du Sud, 5, 1348 Louvain-la-Neuve, Belgium Received 23 July 2003; received in revised form 4 February 2004; accepted 26 March 2004 Abstract Reserve networks are a major tool of ecological management aiming at biodiversity conservation. Maximizing the number of species conserved with the minimum land sacrifice is a primary requirement in reserve design. In this study, we examine the efficiency of five different scenarios to conserve: (i) the biodiversity of one target group and (ii) the overall biodiversity of an area. The study was conducted in Dadia Reserve, in northern Greece. Six groups of species were selected to represent its biodiversity: woody plants, orchids, Orthoptera, aquatic and terrestrial herpetofauna, and small terrestrial birds. The scenarios examined represent different conservation approaches to select network sites. For each approach, the starting point was one of the above six groups of species, considered as the target group. In scenario A, which reflects the hotspot approach, the sites richest in species are selected. Scenario B selects the sites most complementary in terms of species richness. The next two scenarios use the principle of environmental rep- resentativeness, expressed in terms of habitat (scenario C) or vegetation (scenario D). Under scenario E, sites forming the network are selected at random. The rank of scenarios in terms of preserving the species of the target group was always B > A > C > D > E, irrespective of the group considered as target group. Their rank, when preservation of the total biodiversity was the issue, was B, A > C, D > E. Ó 2004 Elsevier Ltd. All rights reserved. Keywords: Reserve design; Ecological networking; Biodiversity; Conservation; Complementarity 1. Introduction rather than scientific criteria. Nevertheless, a multitude of methods and scientific approaches have been devel- Reserves have a major role as a tool for preserving oped to facilitate optimal reserve design; they are pri- biodiversity (Margules and Pressey, 2000). In designing marily based on hotspot identification and on reserve, one of the objectives is to maximize the number complementary and representative networking. of species conserved with the minimum land sacrifice, or Biodiversity hotspots are areas with a large number else satisfy the ‘‘minimal reserve set’’ requirement (re- of species or with large numbers of rare, threatened or view by Cabeza and Moilanen, 2001). Reserves are still endemic species. Because of these features, they are set up in response to political and economic interests considered of high conservation priority (Margules and Usher, 1981; Prendergast et al., 1993; Muyers et al., * Corresponding author. Tel.: +30-26510-60949; fax: +30-26510- 2000; Rodriguez and Young, 2000). Designing reserve 29477. networks on the basis of the richest-in-species areas re- E-mail address: [email protected] (V. Kati). flects the traditional practice. 0006-3207/$ - see front matter Ó 2004 Elsevier Ltd. All rights reserved. doi:10.1016/j.biocon.2004.03.020 472 V. Kati et al. / Biological Conservation 120 (2004) 471–480 Complementarity, a term invented by Vane-Wright 2. Methods et al. (1991), is considered a key-principle in reserve designing (Pressey et al., 1993; Margules and Pressey, 2.1. Study area 2000). Its application in site selection ensures that as much as possible new attributes will be added to an The study area is situated in northeastern Greece existing reserve system. These attributes can be species, (longitude 26°000 to 26°190, latitude 40°590 to 41°150). It endemic species (Kirkpatrick, 1983) or landscape units covers 430 km2, of which 424.6 km2 belong to the Re- (Pressey and Nicholls, 1989). A great number of itera- serve of ‘‘Dadia-Lefkimmi-Soufli Forest’’, abbreviated tive algorithms have been proposed to provide minimum as Dadia Reserve. After the CORINE typology (Devillers sets of complementary sites that can maintain biodi- and Devillers-Terschuren, 1996), nine main vegetation versity at its maximum (see review by Csuti et al., 1997; types occur in the sampled area, further divided to Pressey et al., 1997). nineteen sub-types (Table 1). A map of the main vege- Representativeness is an old and widely used princi- tation types of Dadia Reserve is presented in Kati et al. ple for reserve selection (Margules and Usher, 1981; (2004a). Franklin, 1993). The aim in applying it is to ensure that all environmental variation is well represented in the 2.2. Dataset selected reserve network (Faith and Walker, 1996). Standard typologies of habitats or vegetation types (see We used a dataset of 194 species (Kati et al., 2004b): Devillers and Devillers-Terschuren, 1996; Pienkowski 46 woody plant species, 19 orchid species, 39 Orthoptera et al., 1996; Stoms et al., 1998) can be used to represent species, 10 species of aquatic herpetofauna, 10 species of the diversity of the environment. terrestrial herpetofauna, and 70 species of small terres- The aim of this study is to examine the efficiency of trial birds. Species were sampled within 33 sites in the five different conservation approaches to preserve the study area, ranging in size from 0.02 km2 up to 0.2 km2, biodiversity (in terms of six groups of species) of a during the years 1998–1999. Sampling methodologies Mediterranean-type area. To this end, we conducted a are described in Kati et al. (2004b). None of the species study in Dadia Reserve, in northern Greece, an area sampled was endemic. For Orthoptera, terrestrial her- protected because of its high ornithological value. The petofauna species and birds, data were semi-quantita- groups selected to represent its biodiversity were the tive, whereas for woody plant species, orchids and woody plants (tree and shrub species), the orchids, aquatic herpetofauna species, data were of the type the Orthoptera, the aquatic herpetofauna (amphibians presence-absence. and freshwater turtles), the terrestrial herpetofauna (lizards and terrestrial tortoises), and the small terres- 2.3. Data analysis trial birds (Passeriformes, Columbiformes, Coracifor- mes and Piciformes). For each of the five conservation The diversity of sites was estimated in terms of species approaches examined, the starting point is one of the richness (S), weighted species richness (WS), and Shan- above six groups of species. This is considered as the nonindex (H 0). The weighted species richness (WS) is the target group, for the sake of which the reserve network sum of the vulnerability indices of all the species of the is primarily designed. The question we ask is how site. The vulnerability index of a species, taking values much biodiversity of each one of the other groups and 0–35, estimates its status in the European Union (EU). of the total biodiversity of the area is preserved in the It is calculated on the basis of its distribution, on both a networks, constructed following the different conser- coarse (in grids of 500 km  500 km) and a fine scale (in vation approaches. In scenario A, which reflects the grids of 10 km  10 km), of its population size (or its hotspot approach, the sites richest in species are se- habitat rarity), and of its population trend (for full de- lected. Scenario B selects the sites most complementary scription, see Bezzel, 1980). Vulnerability indices for in terms of species richness. The next two scenarios use orchids are published in Devillers et al. (1991), for Or- the principle of environmental representativeness, ex- thoptera in Kati et al. (2004a), and for herpetofauna and pressed in terms of habitat (scenario C) or vegetation birds in Kati (2001). (scenario D). Under scenario E, sites forming the re- We define target group the group of species for which serve network are selected at random. The five ap- we are designing the reserve network and as non-target proaches are evaluated according to their efficiency to groups all other groups. For every target group, we preserve non-target group and the total biodiversity of constructed a similarity matrix of the samples, where its the area. Our ultimate goal is to provide guidelines as members were found, using two coefficients widely used to the best practice for designing local, small-scale re- in ecological studies – Sørensen and the Steinhaus serve networks, under different regimes of data, budget, assymetrical coefficients of similarity. Sorensen coeffi- and time availability, particularly for the Mediterra- cient behaves very well for binary data and Steinhaus is nean region. its equivalent for semi-quantitative