Relationship between maximum leaf photosynthesis, nitrogen content and specific leaf area in Balearic endemic and non-endemic Mediterranean species

Gas exchange parameters, leaf nitrogen content and specific leaf area (SLA) were measured in situ on 73 C-3 and five C-4 plant species in Mallorca, west Mediterranean, to test whether species endemic to the Balearic Islands differed from widespread, non-endemic Mediterranean species and crops in their leaf traits and trait inter-relationships. Endemic species differed significantly from widespread species and crops in several parameters; in particular, photosynthetic capacity, on an area basis (A), was 20 % less in endemics than in non-endemics. Similar differences between endemics and non-endemics were found in parameters such as SLA and leaf nitrogen content per area (N-a). Nevertheless, most of the observed differences were found only within the herbaceous deciduous species. These could be due to the fact that most of the non-endemic species within this group have adapted to ruderal areas, while none of the endemics occupies this kind of habitat. All the species-including the crops-showed a positive, highly significant correlation between photosynthetic capacity on a mass basis (A(m)), leaf nitrogen content on a mass basis (N-m) and SLA. However, endemic species had a lower A(m) for any given SLA and N-m Hypotheses are presented to explain these differences, and their possible role in reducing the distribution of many endemic Balearic species is discussed. (C) 2003 Annals of Botany Company.