Taxonomy, morphometric circumscription and karyology of the Mediterranean African representatives of Ophrys sect. Pseudophrys (Orchidaceae)

Abstract

Ophrys sect. Pseudophrys shows a pronounced morphological variation, especially in Mediterranean Africa, a centre of radiation of this section. In Tunisia, different authors recognize between 9 and 13 species (and 5 subspecies). A multivariate analysis was performed in order to study the polymorphisms of eight critical species of Ophrys sect. Pseudophrys represented in Tunisia (O. africana, O. aspea, O. battandieri, O. eleonorae, O. gazella, O. numida, O. subfusca and O. vallesiana). The variation in 20 floral characters (including 5 ratios) were evaluated in 332 live plants belonging to 20 populations of the mentioned Tunisian representatives of sect. Pseudophrys. Two additional labellum characters were measured for the populations belonging to O. subfusca group (namely O. aspea, O. battandieri, O. numida and O. subfusca). In order to distinguish the different species, and identify characters defining their circumscription, we carried out detailed morphological analyses on two different data sets of sect. Pseudophrys, one consisting of all the currently recognized species, and another consisting of all the populations belonging to the controversial O. subfusca group. In order to summarize the overall morphological variation among Pseudophrys, a principal components analysis (PCA) and a cluster analysis of populations were conducted. To test the separation of population groups resulting from the PCA and cluster analyses, a canonical discriminant analysis (CDA) was conducted. The most discriminating characters are presented in the form of boxplots. Due to extensive overlapping in even the most distinguishing characters, it is not possible to accept O. africana as a distinct species from O. gazella, or O. numida as distinct from O. subfusca. Cytological data and chromosome counts are reported for the first time for eight Tunisian members of sect. Pseudophrys. All of the analysed species are diploids with 2n = 36 chromosomes. Neither polyploids nor aneuploids were detected. A key to the accepted species is provided.