Abstract
Plants growing in high-mountain environments may share common morphological features through convergent evolution resulting from an adaptative response to similar ecological conditions. The Carex flava species complex (sect. Ceratocystis, Cyperaceae) includes four dwarf morphotypes from Circum-Mediterranean mountains whose taxonomic status has remained obscure due to their apparent morphological resemblance. In this study we investigate whether these dwarf mountain morphotypes result from convergent evolution or common ancestry, and whether there are ecological differences promoting differentiation between the dwarf morphotypes and their taxonomically related large, well-developed counterparts. We used phylogenetic analyses of nrDNA (ITS) and ptDNA (rps16 and 5’trnK) sequences, ancestral state reconstruction, multivariate analyses of macro- and micromorphological data, and species distribution modeling. Dwarf morphotype populations were found to belong to three different genetic lineages, and several morphotype shifts from well-developed to dwarf were suggested by ancestral state reconstructions. Distribution modeling supported differences in climatic niche at regional scale between the large forms, mainly from lowland, and the dwarf mountain morphotypes. Our results suggest that dwarf mountain morphotypes within this sedge group are small forms of different lineages that have recurrently adapted to mountain habitats through convergent evolution.
Highlights
The adaptation of plant species to high-mountain environments frequently entails a series of convergent phenotypic traits that may be displayed by very different taxonomic groups
In the case of C. flava and C. lepidocarpa, we focused on the regions geographically close to the dwarf morphotypes, in order to accurately detect differences in niche requirements at a fine scale
Even though populations belong to three different lineages (Fig 7), they show a wide degree of overlap in the macromorphological variation (MPCA) (Fig 3A), with no macromorphological characters showing an overlap below 25% (Table 4)
Summary
The adaptation of plant species to high-mountain environments frequently entails a series of convergent phenotypic traits that may be displayed by very different taxonomic groups. Geophytic or chasmophytic–frequently cushion-forming–growth forms, fleshy and/or tomentose leaves, CAM metabolism, and dwarfism are some of the characters that allow plants to survive. Reference Convergent character [7]. Dwarf cushion-forming habit and white tomentose indumentum [8]. Multiple appearances in Angiosperms [9].
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