G.V. Cron

The genetic ghost of an invasion past: colonization and extinction revealed by historical hybridization in Senecio

Hybridization is an important evolutionary factor in the diversification of many plant and animal species. Of particular interest is that historical hybridization resulting in the origin of new species or introgressants has occurred between species now geographically separated by great distances. Here, we report that Senecio massaicus, a tetraploid species native to Morocco and the Canary Islands, contains genetic material of two distinct, geographically separated lineages: a Mediterranean lineage and a mainly southern African lineage. A time‐calibrated internal transcribed spacer phylogeny indicates that the hybridization event took place up to 6.18 Ma. Because the southern African lineage has never been recorded from Morocco or the Canary Islands, we hypothesize that it reached this area in the distant past, but never became permanently established. Interestingly, the southern African lineage includes S. inaequidens, a highly invasive species that has recently become widespread throughout Europe and was introduced at the end of the 19th century as a ‘wool alien’. Our results suggest that this more recent invasion of Europe by S. inaequidens represents the second arrival of this lineage into the region.

A clarification of Gnetum L. (Gnetaceae) in Africa and the description of two new species

Gnetum L. is a genus of economic importance distributed in the humid rainforests of Central Africa. The African species of Gnetum are dioecious climbers and only two species (Gnetumafricanum Welw. and G.buchholzianum Engl.) have been described previously. The names G.africanum and G.buchholzianum have been applied interchangeably to similar morphological forms of Gnetum specimens in Africa or on duplicates of specimens causing taxonomic confusion. The nomenclature of Gnetum species in Africa is thus in need of reappraisal. Morphological descriptions are based on examination of over 300 specimens from various herbaria, mainly B, BR, FHI, J, K, LISC, P, PRE, WAG and YA. The original applications of the names Gnetumafricanum and Gnetumbuchholzianum are clarified and two new African species (Gnetuminterruptum E.H. Biye sp.nov. and Gnetumlatispicum E.H. Biye sp.nov.) are described on the basis of morphological features. A key to the African species is provided and the main characters, such as the shape and size of spike that are essential in the recognition of species in the genus Gnetum in Africa as well as the importance of conservation are discussed. These species are assessed as threatened and at a high risk of global extinction according to the IUCN Red List categories and criteria, and are in need of conservation measures for their protection.

Phylogenetic Relationships and Evolution in the Strelitziaceae (Zingiberales)

Abstract Evolutionary trends and phylogenetic relationships in the Strelitziaceae (Zingiberales) were investigated using sequence data from ten plastid and two nuclear regions and a morphological dataset. The status of species of Strelitzia were evaluated in terms of the phylogenetic species concept. Relationships among the genera remain equivocal with two hypotheses emerging: (i) Strelitzia sister to a clade comprising Ravenala and Phenakospermum when indels are included, or (ii) Ravenala sister to the remainder of the Strelitziaceae when indels are excluded in/from the combined molecular and ‘total evidence’ analyses. Within Strelitzia, S. nicolai is sister to the rest of the genus, with S. alba sister to S. caudata. Strelitzia reginae is shown to be paraphyletic as S. juncea is nested within it, but more sampling at the population level is needed to confirm the taxonomic status of S. juncea. The highly localized and endangered Strelitzia alba is confirmed as a distinct species, as are S. caudata and S. nicolai, despite few morphological differences. Evolutionary trends are linked to changes in habitat and coevolution with pollinators. Climate change in southern Africa is thought to have restricted Strelitzia nicolai (or its ancestor) to the eastern coastal region, with subsequent allopatric speciation of S. alba and S. caudata, and relatively recent parapatric divergence of S. juncea from S. reginae.

Bolandia (Asteraceae, Senecioneae) : A new genus endemic to Southern Africa

ABSTRACT The genus Bolandia (Asteraceae, Senecioneae) comprises two known species, B. pedunculosa and B. argillacea, previously included in Cineraria. Distinguishing features of Bolandia include the fusiform shape of the cypselae and strong median rib on the glabrous inner surface of the ray and outer disc cypselae, solitary ecalyculate capitula on long peduncles, and a truncate style apex with a central tuft of sweeping hairs. Bolandia occurs in the mountains of the Western Cape in southern Africa, with a disjunct population of B. pedunculosa in the Witteberg of the Eastern Cape and the nearby Drakensberg mountains in Lesotho. Bolandia argillacea is endemic to the mountains near Worcester in the Western Cape. Two forms of B. pedunculosa are informally recognized, a tomentose and a glabrescent form, the latter including plants previously known as C. albomontana.

Morphometric delimitation of Gnetum species in Africa

The economically important gymnosperm Gnetum L. is distributed in humid tropical forests of Africa. Its leaves are used as commercialized vegetables and greatly alleviate poverty for local people. Previously, the number of species recognized in Africa was uncertain, and Gnetum africanum Welw. and G. buchholzianum Engl. had been variously, and erroneously, applied to specimens. Based on recent morphological studies, species limits were clarified and two new African species, Gnetum interruptum E.H.Biye and G. latispicum E.H.Biye, were described. The purpose of this study was to determine species limits, to investigate potential infraspecific variation in wild African Gnetum species and to determine which features distinguish them in order to assess the validity of four species recognized by Biye et al. (Pl Syst Evol 300(2):263–272, 2014). Sixty-seven morphological characters were scored for a total of 175 (56 male and 119 female) specimens and analysed using cluster, principal components and principal coordinates analyses. Four distinct clusters of Gnetum specimens were recognized that correspond to the species now described as G. africanum, G. buchholzianum, G. interuptum and G. latispicum. A lack of geographical correlation with subclusters as well as their structure suggests there is no justification for recognizing infraspecific taxa. Characters that describe features of the spikes should be used to differentiate between and identify the species in Africa. In view of the high levels of utilization of two species and rarity of a third, it is urgent to assess the threat status of Gnetum species in Africa and to design appropriate conservation strategies to conserve these economically valuable plants.

Climate and leaf shape relationships in four Helichrysum species from the Eastern Mountain Region of South Africa

Morphological variation in plants can be affected by climate, which influences how species are identified as well as hypotheses of species divergence. We tested whether climatic niches were correlated with the observed morphological (leaf) variation of four geographically overlapping and reproductively similar Helichrysum species (Hilliard’s Group 4 in the southern African flora). We found that two species, H. gymnocomum and H. odoratissimum, showed clear evidence for climatic niche conservatism and that across all species leaf shape was not significantly correlated with climatic niche. Interestingly, there did appear to be a pattern, albeit statistically non-significant, that linked cold, dry climates to leaf shape, particularly for the variable and widespread H. odoratissimum. For example, smaller, narrower leaf shapes were generally found in cooler, drier regions, while large, broad leaves (particularly those of H. odoratissimum) are found in warmer, more humid regions. In addition, the data also showed that two species, H. odoratissimum and H. gymnocomum, comprised a single variable group. The climate-leaf shape patterns could potentially reflect the morphological variation between these two species. Collectively, these findings suggest further work is necessary to determine the role of climate and leaf shape variation in species divergence in the Eastern Mountain Region.

Two new species of Cineraria L. (Senecioneae, Asteraceae)

Two new species of Cineraria L., C. austrotransvaalensis Cron and C. hederifolia Cron, are described from the Transvaal. Their affinities, geographical distribution and conservation status are discussed.

A phenetic study of the Emilia coccinea complex (Asteraceae, Senecioneae) in Africa

Emilia coccinea complex is a widespread and morphologically variable species in tropical and subtropical Africa. Jeffrey’s (Kew Bull 52:205–212, 1997) revision of the African Emilia species with large capitula resulted in a complex of eight species with E. coccinea sensu stricto restricted to eastern and southern tropical Africa and characterised by long-appendaged style branches and bright orange flowers. To evaluate the delimitations within this complex, a morphological phenetic study based on 134 herbarium specimens spanning the geographical range of the E. coccinea complex was undertaken using cluster analysis and ordination (principal coordinates analysis and non-metric multidimensional scaling). Five of the eight species (E. emilioides, E. jeffreyana, E. praetermissa, E. subscaposa, and E. vanmeelii) formed distinct phenetic groups, whereas two species (E. caespitosa and E. coccinea) were indistinguishable because of variability in some key characters (viz., cypsela indumentum and shape of cauline leaves) suggesting that they are possibly one heterogeneous species. Emilia lisowskiana is not supported as a distinct species as three E. coccinea specimens group with it in the cluster analysis. Emilia emilioides with mostly long, narrow cauline leaves, narrow capitula, and unappendaged style branches apices is the most distinct taxon in all analyses. Univariate analyses of ten selected characters revealed that the reproductive features are able to distinguish some species, as well as a few vegetative ones. The application of various species concepts to this species complex is discussed. A key to the species in this complex is provided.

Microsatellite primers for a species of South African everlasting daisy (Helichrysum odoratissimum; Gnaphalieae, Asteraceae)

Premise of the study: Microsatellites were developed for the widespread Helichrysum odoratissimum (Asteraceae) to estimate gene flow across diploid populations and to test if gene flow occurs among other closely related lineages within this genus. Methods and Results: Ten primer pairs were developed and tested using populations across South Africa; however, only seven primer pairs were polymorphic for the target species. The seven polymorphic primers amplified di- and trinucleotide repeats with up to 16 alleles per locus among 125 diploid individuals used for analyses. Conclusions: These markers can be used to estimate gene flow among populations of known ploidy level of H. odoratissimum to test evolutionary hypotheses. Furthermore, these markers amplify successfully in other Helichrysum species, including the other three taxonomic Group 4 species, and therefore can be used to inform taxonomic work on these species.

Oresbia, a New South African Genus of the Asteraceae, Senecioneae

ABSTRACT Oresbia heterocarpa Cron & B. Nordenstam (Asteraceae, Senecioneae) is described as a new genus and species from South Africa. Until now the species has been known as Cineraria tomentosa Lessing, although first described as Senecio lanatus L. f. Both of these names are illegitimate. Characteristic features of Oresbia are the perennial habit with sessile, non-pinnatifid leaves, which are densely tomentose below, and the heteromorphic cypselae with four-winged ray-floret cypselae. The closest affinities of Oresbia may be with Phaneroglossa B. Nordenstam and possibly also Lamprocephalus B. Nordenstam, which have similar distribution ranges in the Western Cape mountains.