Botanical Journal of the Linnean Society (2001), 136: 247–254. With 2 figures doi:10.1006/bojl.2000.0451, available online at http://www.idealibrary.com on The west Mediterranean orophilous taxa of Sideritis L. (Lamiaceae): a new species of subsection Hyssopifolia from south-eastern Spain SEGUNDO RIOS* and MANUEL B. CRESPO Centro Iberoamericano de la Biodiversidad (CIBIO), Universidad de Alicante, Apdo. 99, E-03080 Alicante, Spain DIEGO RIVERA Departamento de Biologı´a Vegetal, Facultad de Biologı´a, Universidad de Murcia, E-30100 Murcia, Spain Received August 2000; accepted for publication February 2001 Orophilous taxa of Sideritis sect. Sideritis (Lamiaceae) are rare, although highly diversified in south-eastern Spain. Most of them belong to subsections Hyssopifolia and Fruticulosa and show very reduced distribution areas in the summits of the highest Betic mountains. The inaccessibility of their habitats has meant that many of them have been described only within the last twenty years. In this context, a new species Sideritis tugiensis is described in subsection Hyssopifolia, from the Oromediterranean summits of Sierra de Segura (south-eastern Spain). It is a woody, cushion-shaped plant, resembling both S. carbonellis Socorro (subsect. Hyssopifolia) and S. glacialis Boiss., s.l. (subsect. Fruticulosa), though important morphological divergences warrant recognition at species rank. Data on morphology, ecology and chorology of the new species are reported, and affinities and differences with regard to close taxa from other subsections are presented. Evolutionary trends in the whole aggregate are briefly discussed.  2001 The Linnean Society of London ADDITIONAL KEY WORDS: Betic mountains – biogeography – conservation – ecology – evolutionary trends – morphology – taxonomy. south-eastern Spain and North Africa. They include INTRODUCTION six taxa, which grow in the summits of the Moroccan Sideritis L. sect. Sideritis (Lamiaceae) is endemic to Atlas (S. jahandiezii Font Quer), Betic mountains of the western Mediterranean and is highly diversified south-eastern Spain (S. carbonellis Socorro and S. in the south-eastern part of the Iberian Peninsula. glacialis subsp. glacialis, subsp. vestita Obo ´n & D. Most taxa of the section grow at low altitudes on rather Rivera, and subsp. virens (Boiss.) Obo ´n & D. Rivera) disturbed soils, high mountain taxa being com- and the southern Sistema Ibe ´rico, eastern Spain (S. paratively very scarce (Obo ´n & Rivera, 1994; Rivera glacialis subsp. fontqueriana Obo ´n & D. Rivera [= et al., 1999). The majority of taxa of sect. Sideritis S. fernandez-casasii Rosello ´ et al.]). On the basis of occur in the surroundings of the main Iberian and differences in micromorphological features of the in- North African mountains. dumentum, those taxa are currently included in two Orophilous taxa of Sideritis belong to six subsections different groups, subsect. Fruticulosa Obo ´n & D. Riv- and show a clear polyphyletic origin (Rivera et al., era (S. fruticulosa and S. glacialis, s.l.) and subsect. 1990; Obo ´n & Rivera, 1994). Recently, Rivera et al. Hyssopifolia Obo ´n & D. Rivera (S. carbonellis). (1999) have presented an interesting approach to the However, they share a similar habit and similar aggregate of S. glacialis Boiss. and related taxa from macromorphological characters, perhaps due to con- vergence to the stressful climatic conditions of high mountain habitats. In the course of field work in the Betic mountains * Corresponding author. E-mail: rios@carn.ua.es 247 0024–4074/01/060247+08 $35.00/0  2001 The Linnean Society of London