Some selected publications
Correlations between morphological-anatomical leaf characteristics and environmental traits in Southwest African species of Androcymbium (Colchicaceae)
Membrives N, Pedrola-Monfort J, Caujapé-Castells J
Botánica Macaronésica 24: 73–85 (2003)
We studied 32 populations belonging to 17 Southwestern African taxa of the genus Androcymbium in order to explore the relationships between leaf morphological and anatomical variation and environ-mental characteristics as measured by distribution in two different type velds (Fynbos and Karoo-Karoid types) and the values of 16 edaphic parameters from 22 soil samples. Our results show that only hydric disponibility (measured as the amount and distribution of annual rainfall, and the water retention capa-city) correlates significantly with morphological leaf characteristics in Androcymbium. We detected no significant correlations between pairwise combinations of anatomical traits and climatic or edaphic parameters. These results conform to the hypothesis that the diversification of Southwestern African species of Androcymbium, has been mainly influenced by the arid gradient that already existed when these species began to diversify in the Late Miocene. Thus, they seem to agree with the hypothesis of Stebbins that predicts relatively rapid plant evolution in arid to semiarid regions. Because solely some combinations between characteristics related to aridity and morphological traits are significantly corre-lated, our results reflect only partially Axelrod and Raven's suggestion that the specific diversity in South Africa is a consequence of climatic and edaphic fragmentation
Morphological seed studies of Southwest African Androcymbium (Colchicaceae)
Membrives N, Pedrola-Monfort J, Caujapé-Castells J
Botánica Macaronésica 24: 87–106 (2003)
Macromorphological and micromorphological seed characteristics are described in 32 populations belonging to 19 taxa of the genus Androcymbium distributed in Southwest Africa. The heterogeneity shown in the seed characteristics in Southwest African species is compared with the uniformity described previously in the Northern African congeners. The principal seed characteristics are evaluated in the taxonomic classification of the genus, and their evolution is considered under a recent cladistic analysis from morphological data. According to this phylogeny, all seed characters studied show complex patterns of parallelisms and reversals in the evolution of the genus
Reproductive biology of the genus Androcymbium (Colchicaceae) in Western Southern Africa
Membrives N, Pedrola-Monfort J, Caujapé-Castells J
Orsis 17: 37–59 (2002)
We characterized reproductive biology traits in 32 populations belonging to 17 western southern African taxa of the genus Androcymbium (Colchicaceae) using artificial pollination experiments conducted under homogeneous environmental conditions in a greenhouse. The species surveyed displayed differences in phenological periods between emergence, flowering and senescence. We observed three types of vegetative reproduction that give rise to (1) globose corms, (2) compressed corms, and (3) a dichotomous underground networking of corms that, unlike (1) and (2), entails the elongation of the stem. Seed germination was low in most of the populations. The artificial pollination experiments allowed us to recognize three reproductive systems: self-incompatible, preferentially self-incompatible and self-compatible. In most cases, the reproductive system inferred fromthe artificial pollination experiments disagreed with the classification according to the P/O ratio. The variability observed in nectar characteristics (odour, amount and moment of the day of nectar production) suggests different pollinators for the taxa surveyed. Based on these data, we inferred three reproductive strategies in Androcymbium that assure both species’ survival and the maintenance of levels of genetic variability: (1) preferential self-incompatibility associated with morphological traits that favour the attraction of pollinators; (2) preferential self-incompatibility with high levels of vegetative reproduction; and (3) self-compatibility with high levels of seed production
Relative influence of biological versus historical factors on isozyme variation of the genus Androcymbium (Colchicaceae) in Africa
Membrives N, Pedrola-Monfort J, Caujapé-Castells J
Plant Systematics and Evolution 229: 237–260 (2001)
We carried out isozyme electrophoresis in the South African taxa of Androcymbium to compare their levels of genetic variation with those reported for their North African congeners and to evaluate the influence of reproductive traits, phylogenetic relationships and environmental histories on the evolutionary dynamics of this disjunction between arid zones of North and South Africa. One possible factor to explain the higher number of alleles detected in South Africa is that diversification in this area started within the early Oligocene, whereas the ancestor of the North African species is more recent and corresponds to the late Miocene. Strong environmental selection and habitat specialization in South Africa probably fostered genetic differentiation between species further in this area. In South African taxa, isozymic variation levels were significantly correlated to breeding systems but not to lineage circumscription (i.e., phylogenetic closeness). The assessment of the relative influence of diverse biotic and abiotic factors on isozyme variation shows that, on a short geological time scale, breeding system is the most reliable predictor of levels of genetic variation. On a longer time frame, represented by the splitting that gave rise to the South-North disjunction of the genus in the late Miocene, the influence of environmental histories of North and South Africa on genetic variation overrides that of breeding systems.