Ranking the Azorean Natural Forest Reserves for Conservation Using Their Endemic Arthropods

View metadata, citation and similar papers at core.ac.uk brought to you by CORE provided by Repositório da Universidade dos Açores Journal of Insect Conservation 4: 129–147, 2000. © 2000 Kluwer Academic Publishers. Printed in the Netherlands. Ranking the Azorean Natural Forest Reserves for conservation using their endemic arthropods P.A.V. Borges1,3, A.R. Serrano2,∗ & J.A. Quartau2,∗ 1Departamento de Ciências Agrárias, Universidade dos Açores, Terra-Chã, 9700-851 Angra do Hero´ısmo, Terceira, Açores, Portugal 2Departamento de Zoologia e Antropologia, Faculdade de Cienciasˆ de Lisboa, Centro de Biologia Ambiental, Campo Grande, C2 3◦ Piso, 1700 Lisboa, Portugal 3Author for correspondence (e-mail: [email protected]; tel.: 00 351 295 204592; fax: 00 351 295 332605) Received 1 December 1999; accepted 31 March 2000 Key words: biodiversity, rank, forest reserves, Azores, Atlantic islands Abstract Endemic arthropods were used to evaluate the conservation value of the 16 Natural Forest Reserves (NFRs) of the Azores (Macaronesia). For each of the 280 known Azorean endemic species of arthropods, a rarity index was calculated, using distribution and abundance data obtained from the literature. In addition, several scoring indices were used to rank the 16 NFRs. Frequency distributions of the rarity index indicated that there was a tendency for a greater proportion of the commonest species being represented in the NFRs in contrast with a lower representation of the rarest species. About 60% of the endemic arthropod species that were recorded from the NFRs are ‘single NFR endemics’, that is, are known from only one of the 16 NFRs. Species richness was considered to be a very good surrogate measure of the conservation value of the 16 NFRs under study. The fact that the six highest ranked NFRs (using a composite multi-criteria index) are located in different islands has some important conservation management implications; to preserve a large proportion of the Azorean arthropod biodiversity there is a need to protect sites in all islands. If the five highest ranked NFRs are correctly managed in terms of conservation, then at least 80% of the endemic arthropods known from the NFRs could be protected. Most of the tested taxa (Acari- Oribatei; Lepidoptera; Diptera; Coleoptera) are good surrogates of the overall total set of species present in the 16 NFRs when using a species richness index. Introduction There is a wide variety of techniques which can be used to quantify the relative conservation value of This study focuses on the Natural Forest Reserves natural areas (e.g., Spellerberg 1992; Collinson et al. (NFRs) of the Azores, created under the Portuguese 1995; Turpie 1995; Arita et al. 1997; Fox et al. 1997; law n◦27/88/A. This legislation established 16 pro- Freitag et al. 1997; Kerr 1997; Kirchhofer 1997; Panzer tected natural areas distributed over seven islands (see & Schwartz 1998; Troumbis & Dimitrakopoulos 1998). Methods). There are few large undisturbed areas of The selection of methods depends largely on the goals native forest in the Azorean islands. The 16 NFRs and parameters of any given study (Turpie 1995). In include a great proportion of this important habitat and the present case, we were interested in the biodiversity constitute a good sample of the available fragments of of the Azorean endemic arthropod species and their the original primitive ‘Laurissilva’. conservation status. There are few studies which have attempted to ∗Both of these authors have contributed equally to this paper. assess the conservation status of arthropods in the 130 P.A.V. Borges et al. Macaronesian islands (e.g., Meyer 1995; Geisthardt Table 1. List of the Natural Forest Reserves (NFRs) of the Azores. 1996; Lecoq 1996; Schmidt & Geisthardt 1996). The For each, name, area and minimum and maximum altitude are diversity and complexity of the arthropod fauna of the presented. Azores is still incompletely known, It is clear from Code Name Island Area Altitude the available literature (see the comprehensive list of (ha) (m) Borges & Vieira 1994) that some groups are better stud- 120 Cabeço do Fogo FAI 37 400–529 ied than others. It is, however, unclear if the relative 121 Vulcao˜ dos Capelinhos FAI 196 0–170 proportion of available publications for each arthropod 122 Lagoa do Caiado PIC 125 800–939 order reflects its relative species richness. There can be 123 Misterio´ da Prainha PIC 641 425–841 124 Caveiro PIC 196 850–950 little doubt, for example, that some groups are poorly 125 Caldeira da Graciosa GRA 236 137–402 known because of their small size, taxonomic difficul- 126 Caldeiras Funda e Rasa FLO 442 350–600 ties (e.g., Acari, Collembola, Diptera, Hymenoptera) 127 Morro Alto e Pico da Se´ FLO 1556 300–400 or difficulties in sampling (e.g., cave and soil animals). 128 Pico do Arieiro SJG 37 800–958 It seemed clear to the authors that significant 129 Pico das Caldeirinhas SJG 50 700–815 130 Picos do Carvao˜ e da SJG 167 800–1083 progress in the study of the Azorean arthropod fauna Esperança had to start with a comprehensive revision of data on 131 Atalhada SMG 15 425–530 the distribution and abundance of the known species. 132 Graminhais SMG 19 850–925 In the present study, we have concentrated only on 133 Pico da Vara SMG 752 400–1103 the Azorean endemic species, because endemic species 134 Biscoito da Ferraria TER 355 475–808 135 Serra de Sta Barbara´ e TER 1083 550–1025 have been widely used as indicators of the conservation M. Negro value of natural habitats. Importantly, the rarity status of each endemic FAI – Faial; PIC – Pico; GRA – Graciosa; FLO – Flores; SJG – S. Jorge; SMG – S. Miguel; TER – Terceira. Azorean arthropod species is in general unknown. There are several ways of giving a score of rarity to a species, either using algorithms (e.g., Freitag et al. islands concerned are shown in Figure 1. In S. Maria 1997; Kirchhofer 1997) or applying a Rabinowitz-type island there is no NFR yet, but there is a proposal to rarity classification (e.g., Daniels et al. 1991; Kattan include a small fragment of native forest at the top of 1992; McIntyre 1992; Goerck 1997). Alternatively, the Pico Alto. assignment of rare species could be made on the basis of The NFRs differ greatly in their areas (see Table 1) abundance and/or range size as summarized in Gaston and habitats within them. On the island of Faial, (1994). ‘Vulcao˜ dos Capelinhos’ (NFR 121) is a recent volcano Therefore, the aims of the present study are: (1) (a historical eruption from 1957–58) made up of mainly to compile an inventory of known Azorean endemic lavicolous habitat. Caldeira da Graciosa (NFR 125) at arthropod species; (2) to assign a rarity score to each the island Graciosa, is a volcanic caldera without any endemic arthropod species; (3) and to rank each NFR native vegetation, and covered with exotic forests and in terms of its conservation value (using a range of pasture. The three NFRs from S. Jorge (NFR 128, 129 techniques). and 130) are natural grassland fenced against grazing. The authors are aware that precise data on the abun- All the other NFRs are dominated by the indigenous dance and distribution estimates are not currently avail- forest known as ‘Laurissilva’. Semi-natural grassland able for all the endemic arthropods from the Azores. (NFRs 122, 124, 126, 127, 132, 133, 134 and 135) and Therefore, the results and conclusions here presented exotic forests (NFRs 133, 134 and 135) also occur in could be severely biased by variation in recording effort some of the NFRs. and, as such, should be considered as preliminary. Arthropod data Methods Data on the occurrence and abundance of each endemic species were obtained from a literature survey of all the The sites known published entomological works dealing with Azorean arthropods. The recent entomological bibli- The 16 NFRs are listed with their associated code num- ography for the Azores of Borges and Vieira (1994) bers in Table 1 and their locations within the seven was especially useful. In addition, more recent works Conservation – forest reserves – Azores 131 were obtained from bibliographical databases. For the The database Coleoptera and Araneae, unpublished data from one of the authors (P. Borges) was also used. Available infor- For each potential taxon, information was obtained mation was collated in a database specially created in about distribution in the nine Azorean islands, and FILE MAKER 4.0. number of records in each case. A record includes the Figure 1. (Continued) 132 P.A.V. Borges et al. Figure 1. Location of the 16 Natural Forest Reserves (NFRs) in the Azorean islands. locality, date, number of specimens collected and the Species scores host and/or habitat. In some cases, this information was incomplete. Where no information was available on To obtain a score of rarity for each arthropod species the number of specimens sampled, it was assumed that an index based on the rarity index (RI) of Kirchhofer only one specimen was collected. In cases where an (1997) was used. As the data available for the Azorean author refers to ‘lots of specimens’, that information arthropods are different in type and quality to the data was included as such. used by Kirchhofer (1997), his index was adapted, to A total of 280 species, subspecies and varieties (vari- generate the following function: eties only in Diptera) were included in the database. RI = (L/TL ) + A + (I/9) + (GI/3) + (NFR/16) For simplification, all 280 taxa will hereafter be o referred to as species. This list was confined to those species endemic to the Azores.

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