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1. Summary of our methodology (in preparation)

2. Red Listing Explained (links to IUCN site)

3. Detailed Methodology IUCN MADCAT (from Callmander et al., 2007)

Geographic data are compiled for all herbarium specimens available. Geographical coordinates for recent collections were recorded with a global positioning system or assigned post facto for older specimens using a gazetteer of botanical collecting localities (Schatz & Lescot, 1996).

Malagasy species are assessed using the current IUCN Red List Criteria (2001). Threatened species are those evaluated as Critically Endangered (CR), Endangered (EN), or Vulnerable (VU) with respect to extinction risk in the wild. We have argued elsewhere (Callmander et al., 2005) that the data deficient (DD) category should be used with parsimony to avoid underestimating the number of threatened species; this approach has been followed here. We used four quantitative Red List criteria and sub-criteria (IUCN, 2001) to determine threat: rapid population decline (Criterion A), limited geographic range and small population size linked with fragmentation, decline or fluctuation (Criteria B and C), very small population size (Criterion D); we did not attempt to analyze extinction risk quantitatively using Criterion E.

For each species, the geographical information system Arcview v. 3.3 (ESRI, Redlands, USA) is used to measure three Red List criterion parameters: extent of occurrence (EOO, minimum convex polygon containing all points of occurrence), area of occupancy (AOO, area estimated by superimposing a grid onto occurrence points and calculating the cumulative area of cells occupied by a species), and predicted future decline (PFD, estimated continuing reduction in a species’ AOO). For species restricted to primary vegetation PFD was estimated using (AOO outside protected areas / total AOO) x 100, which is based on two assumptions: (1) ongoing habitat degradation and destruction will leave few significant areas of primary vegetation outside the protected area network, and (2) loss of primary vegetation within protected areas will be minimal. While some unprotected areas may escape destruction (especially on steep or rugged terrain), it is nevertheless unlikely that many populations of long-lived plants will survive outside protected areas after 3 generations, given Madagascar’s high rate of deforestation (Achard et al., 2002; Green & Sussman, 1990).

The number of subpopulations within the total population of a species was estimated by overlaying a 10 * 10 km grid onto the mapped locality records and counting as distinct subpopulations the number of non-contiguous occupied cells or cell clusters (Schatz et al., 2000; Good et al., 2006). The number of subpopulations located within protected areas was determined by overlaying the distribution of subpopulations onto a map of protected areas.

The grid cell size used to calculate AOO influences Red List assessments (Williset al., 2003). For Red List assessments the appropriate selection of grid cell size is dependent upon the shape, size and homogeneity of a species’ distribution, as manifested in part by its extent of occurrence. By selectively applying complementary methods for choosing grid size (Schatz et al., 2000; Willis et al., 2003; IUCN & SSC, 2004), depending on distribution attributes, Callmander et al. (2007) have shown that there is no single best approach to selecting an appropriate scale for calculating area of occurrence, and have demonstrated that the method chosen can profoundly impact threat assessments.

The Red List guidelines (IUCN & SSC, 2004) indicate that when selecting a grid 'the appropriate scale [for calculating AOO] depends on the taxon in question and the comprehensiveness of the distribution data', with a 2 x 2 km cell size suggested for most situations. Gardenfors (2001) recommended using smaller cells if a species is suspected of being CR but this presupposes an IUCN assessment (Willis et al., 2003). Schatz et al. (2000) used 10 x 10 km cells to analyse species in Madagascar’s endemic plant families, a size considered to correspond to the average extent of an isolated subpopulation (Good et al., 2006). Willis et al. (2003) proposed using grid cells equal to 1/10 of the length between the most distant pair of points of the EOO polygon. Callmander et al. (2007) have shown that a 3 x 3 km grid better reflect the overall poor level of geographic sampling of plants in Madagascar than a 2 x 2 km cell size. The first one corresponds closely to the near maximum for a taxon to be listed as CR under Red List criterion B2 (for which the threshold is 10 km2).


Achard, F, Eva, H.D, Stibig, H.-J., Mayaux, P., Gallego, J., Richards, T. & Malingreau, J.-P. (2002). Determination of deforestation rates in the world’s humid tropical forests. Science, 297, 999–1002.

Callmander, M.W., Schatz, G.E., Lowry, P.P. II., Laivao. M.O., Raharimampionona, J., Andriambololonera, S., Raminosoa, T. & Consiglio T. (2007). Application of IUCN Red List criteria and assessment of Priority Areas for Plant Conservation in Madagascar: rare and threatened Pandanaceae indicate new sites in need of protection. Oryx 41(2): 168-176.

Callmander, M.W., Schatz, G.E. & Lowry II, P.P. (2005) IUCN Red List assessment and the Global Strategy for Plant Conservation: taxonomists must act now. Taxon, 54, 1047–1050.

Gärdenfors, U., Hilton-Taylor, C., Mace, G. & Rodríguez, J.P. (2001) The application of IUCN Red List Criteria at regional levels. Conservation Biology, 15, 1206–1212.

Good, T. C., Zjhra, M.L. & Kremen, C. (2006) Addressing data deficiency in classifying extinction risk: a case study of a radiation of Bignoniaceae from Madagascar. Conservation Biology,20, 1099–1110.

Green, G.M. & Sussman, R.W. (1990) Deforestation history of the eastern rain forest of Madagascar from satellite image. Science, 248, 212–215.

IUCN (2001) 2001 Categories and Criteria (version 3.1). IUCN, Gland, Switzerland [].

IUCN (2006) 2006 IUCN Red List of Threatened Species. IUCN, Gland, Switzerland [].

IUCN & SSC (2004) Guidelines for using the IUCN Red List Categories and Criteria. IUCN, Gland, Switzerland.

Schatz, G.E., Birkinshaw, C., Lowry II, P.P., Randriantafika, F. & Ratovoson, F. (2000) The endemic plant families of Madagascar project: integrating taxonomy and conservation. In Diversité et Endémisme à Madagascar(eds. W.R. Lourenço & S.M. Goodman), pp. 11–24. Mémoires de la Société Biogéographie, Paris, France.

Schatz, G.E & Lescot, M. (1996) Gazetteer to Malagasy Botanical Collecting Localities.

Willis, F., Moat J. & Paton A. (2003) Defining a role for herbarium data in Red List assessments: a case study of Plectranthus from eastern and southern tropical Africa. Biodiversity and Conservation, 12, 1537–1552.


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