J.C. Manning

Phylogenetically independent associations between autonomous self-fertilization and plant invasiveness

Many plant species have been introduced from their native ranges to new continents, but few have become naturalized or, ultimately, invasive. It has been predicted that species that do not require the presence of compatible mates and the services of pollinators for reproduction will be favored in establishment after long‐distance dispersal. We tested whether this hypothesis, generally referred to as Baker’s law, holds for South African species of Iridaceae (iris family) that have been introduced in other regions for horticultural purposes. Fruit and seed production of flowers from which pollinators had been experimentally excluded was assessed for 10 pairs of species from nine different genera or subgenera. Each species pair comprised one naturalized and one nonnaturalized species, all of which are used in international horticulture. On average, species of Iridaceae that have become naturalized outside their native ranges showed a higher capacity for autonomous fruit and seed production than congeneric species that have not become naturalized. This was especially true for the naturalized species that are considered to be invasive weeds. These results provide strong evidence for the role of autonomous seed production in increasing potential invasiveness in plants.

Did Pollination Shifts Drive Diversification in Southern African Gladiolus? Evaluating the Model of Pollinator-Driven Speciation

The pollinator-driven ecological speciation model has frequently been invoked to explain plant richness in biodiversity hotspots. Here, by focusing on Gladiolus (260 species), a flagship example of a clade with diverse pollination biology, we test the hypothesis that high species diversity in southern Africa, one of the world’s most floristically rich regions, has primarily been driven by ecological shifts in pollination systems. We use phylogenetic methods to estimate rates of transition between the seven highly specialized pollination strategies in Gladiolus. We find that pollination systems have evolved multiple times and that some pollination strategies arose by a variety of evolutionary pathways. Pollination shifts account for up to one-third of all lineage splitting events in the genus, providing partial support for the pollinator-driven speciation model. Transitions from the ancestral pollination mode to derived systems have also resulted in increased rates of diversification, suggesting that certain pollination systems may speed up speciation processes, independently of pollination shifts per se. This study suggests that frequent pollination shifts have played a role in driving high phenotypic and species diversity but indicates that additional factors need to be invoked to account for the spectacular diversification in southern African Gladiolus.

Pollinator shifts as triggers of speciation in painted petal irises (Lapeirousia: Iridaceae)

BACKGROUND AND AIMS Adaptation to different pollinators has been hypothesized as one of the main factors promoting the formation of new species in the Cape region of South Africa. Other researchers favour alternative causes such as shifts in edaphic preferences. Using a phylogenetic framework and taking into consideration the biogeographical scenario explaining the distribution of the group as well as the distribution of pollinators, this study compares pollination strategies with substrate adaptations to develop hypotheses of the primary factors leading to speciation in Lapeirousia (Iridaceae), a genus of corm-bearing geophytes well represented in the Cape and presenting an important diversity of pollination syndromes and edaphic preferences. METHODS Phylogenetic relationships are reconstructed within Lapeirousia using nuclear and plastid DNA sequence data. State-of-the-art methods in biogeography, divergence time estimation, character optimization and diversification rate assessments are used to examine the evolution of pollination syndromes and substrate shifts in the history of the group. Based on the phylogenetic results, ecological factors are compared for nine sister species pairs in Lapeirousia. KEY RESULTS Seventeen pollinator shifts and ten changes in substrate types were inferred during the evolution of the genus Lapeirousia. Of the nine species pairs examined, all show divergence in pollination syndromes, while only four pairs present different substrate types. CONCLUSIONS The available evidence points to a predominant influence of pollinator shifts over substrate types on the speciation process within Lapeirousia, contrary to previous studies that favoured a more important role for edaphic factors in these processes. This work also highlights the importance of biogeographical patterns in the study of pollination syndromes.

The Functional Differentiation of the Testa in Seed of Indigofera parviflora (Leguminosae: Papilionoideae)

The mature ovule of Indigofera parviflora has two three-seriate integuments. The outer integument participates in testa formation; the inner is crushed during seed development. The strophiole is distinguishable at an early stage and differentiates rapidly. Cells of the outer epidermis (O1) divide anticlinally and elongate radially to form a palisade layer. The outer tangential walls are thickened at an early stage, and deposition of fluted thickenings on the radial walls occurs at maturity. Palisade cells at the hilum differentiate from subfunicular tissue and are indistinguishable from the epidermal palisade at maturity but differentiate more rapidly. Differentiation of the tracheid bar coincides with final secondary wall deposition without lignification in the palisade. Differentiation of a layer of osteosclereids from the hypodermal layer (O2) accompanies palisade differentiation. The inner epidermis (O3) is crushed during seed development. The raphe cells at the strophiole are shorter and differentiate sooner than the accompanying cells and are bowed under tension. They maintain distal continuity by early development of a very thick outer tangential wall. The strophiolar hypodermis cells elongate greatly, raising the strophiole. The walls of the strophiolar hypodermis are electron translucent and consist of a loose fibrillar network embedded in an amorphous matrix. The functional significance of this unusual wall structure is discussed: water enters the seed at the strophiole, and controlled imbibition appears to be achieved passively through the structure of the hypodermis.

Spatio-temporal history of the disjunct family Tecophilaeaceae: a tale involving the colonization of three Mediterranean-type ecosystems.

BACKGROUND AND AIMS Tecophilaeaceae (27 species distributed in eight genera) have a disjunct distribution in California, Chile and southern and tropical mainland Africa. Moreover, although the family mainly occurs in arid ecosystems, it has colonized three Mediterranean-type ecosystems. In this study, the spatio-temporal history of the family is examined using DNA sequence data from six plastid regions. METHODS Modern methods in divergence time estimation (BEAST), diversification (LTT and GeoSSE) and biogeography (LAGRANGE) are applied to infer the evolutionary history of Tecophilaeaceae. To take into account dating and phylogenetic uncertainty, the biogeographical inferences were run over a set of dated Bayesian trees and the analyses were constrained according to palaeogeographical evidence. KEY RESULTS The analyses showed that the current distribution and diversification of the family were influenced primarily by the break up of Gondwana, separating the family into two main clades, and the establishment of a Mediterranean climate in Chile, coinciding with the radiation of Conanthera. Finally, unlike many other groups, no shifts in diversification rates were observed associated with the dispersals in the Cape region of South Africa. CONCLUSIONS Although modest in size, Tecophilaeaceae have a complex spatio-temporal history. The family is now most diverse in arid ecosystems in southern Africa, but is expected to have originated in sub-tropical Africa. It has subsequently colonized Mediterranean-type ecosystems in both the Northern and Southern Hemispheres, but well before the onset of the Mediterranean climate in these regions. Only one lineage, genus Conanthera, has apparently diversified to any extent under the impetus of a Mediterranean climate.

Counting complete? Finalising the plant inventory of a global biodiversity hotspot

The Cape Floristic Region—the world’s smallest and third richest botanical hotspot—has benefited from sustained levels of taxonomic effort and exploration for almost three centuries, but how close is this to resulting in a near-complete plant species inventory? We analyse a core component of this flora over a 250-year period for trends in taxonomic effort and species discovery linked to ecological and conservation attributes. We show that >40% of the current total of species was described within the first 100 years of exploration, followed by a continued steady rate of description. We propose that <1% of the flora is still to be described. We document a relatively constant cohort of taxonomists, working over 250 years at what we interpret to be their ‘taxonomic maximum.’ Rates of description of new species were independent of plant growth-form but narrow-range taxa have constituted a significantly greater proportion of species discoveries since 1950. This suggests that the fraction of undiscovered species predominantly comprises localised endemics that are thus of high conservation concern. Our analysis provides important real-world insights for other hotspots in the context of global strategic plans for biodiversity in informing considerations of the likely effort required in attaining set targets of comprehensive plant inventories. In a time of unprecedented biodiversity loss, we argue for a focused research agenda across disciplines to increase the rate of species descriptions in global biodiversity hotspots.

Lasiosiphon esterhuyseniae (Thymelaeaceae: Thymelaeoideae), a new species from Northern Cape (South Africa), and the transfer of two additional southern African species to the genus

SummaryWe describe a new species, Lasiosiphon esterhuyseniae Magee & J. C. Manning, for a rigid, densely branched shrublet from the Kalahari Region, Northern Cape, South Africa. Due to the relatively restricted range, the lack of recent records (the most recent from 1940) and the lack of information regarding its palatability we recommend an IUCN status of Data Deficient. Two additional southern African taxa with the inflorescence and floral morphology diagnostic for Lasiosiphon, but currently still included in Gnidia, were encountered and new combinations for these species are provided, viz. Lasiosiphon microcephalus (Meisn.) J. C. Manning & Magee and L. rubescens (B. Peterson) J. C. Manning & Magee. As a result 29 species of Lasiosiphon are now recognised in southern Africa and a complete listing of these species is provided.

Two new subspecies of Dietes (Iridaceae: Iridoideae), Dietes iridioides subsp. angolensis from Angola and Dietes bicolor subsp. armeniaca from eastern South Africa, with notes and range extensions for Dietes butcheriana and Dietes iridioides

Background: Recent collections of Dietes have extended the known geographical range and morphological variation in several species. Objectives: To describe additional taxa in Dietes to reflect the morphological and geographical variation in the species more accurately and to record significant range extensions. Method: Recent collections were compared with existing herbarium material and published literature. Results: Two new subspecies in Dietes are described, viz. Dietes iridioides subsp. angolensis from Angola, constituting the first record of the species from that country, and Dietes bicolor subsp. armeniaca from eastern South Africa, which represents a range extension into southern KwaZulu-Natal. We also document a range extension for the local endemic Dietes butcheriana from KwaZulu-Natal into the Eastern Cape and discuss an anomalous population of D. iridioides , with long-lived flowers, from near Hankey in the Eastern Cape. Conclusions: The range extensions and new infraspecific taxa increase our understanding of the diversity of Dietes in southern and south tropical Africa.

New species of Gladiolus L. and Moraea Mill. (Iridaceae) from Tanzania and Mozambique

Summary.Gladiolus clivorum and G. exalatus are new species of this large African and Eurasian genus of Iridaceae subfamily Crocoideae, both from Tanzania. These additions bring the total in the genus in tropical Africa to 84 species and the entire genus to 270 species. Moraea niassensis (subg. Grandiflorae Goldblatt) is a new, montane species of northern Niassa Province, Mozambique. The Africa and western Eurasian Moraea now includes some 225 species, 25 of which occur in tropical Africa. An identification key to the large-flowered species of subg. Grandiflorae in East Africa and Mozambique is provided. The new species are documented with a map, photographs and a conservation assessment.

Allozyme variation in Barleria saxatilis (Acanthaceae) is lower than in two congeneric endemics

Genetic variability in Barleria argillicola and B. greenii, two sympatric and endemic species restricted to Estcourt in KwaZulu-Natal, was compared with B. saxatilis, a closely related widespread species inhabiting dry hot areas in KwaZulu-Natal, Mpumalanga, Limpopo and Swaziland bushveld. Three populations from each species were sampled for electrophoretically detectable diversity. In contrast to expectations based on similar surveys in other plants, the widespread species showed reduced within-population gene diversity with respect to its endemic congeners. The relationship between the observed levels of allozyme diversity and the mating system in each of the three Barleria species is discussed.