Robert R. Mill

High variation and strong phylogeographic pattern among cpDNA haplotypes in Taxus wallichiana (Taxaceae) in China and North Vietnam

We studied the phylogeography of Chinese yew (Taxus wallichiana), a tree species distributed over most of southern China and adjacent regions. A total of 1235 individuals from 50 populations from China and North Vietnam were analysed for chloroplast DNA variation using polymerase chain reaction–restriction fragment length polymorphism of the trnL‐F intron‐spacer region. A total of 19 different haplotypes were distinguished. We found a very high level of population differentiation and a strong phylogeographic pattern, suggesting low levels of recurrent gene flow among populations. Haplotype differentiation was most marked along the boundary between the Sino‐Himalayan and Sino‐Japanese Forest floristic subkingdoms, with only one haplotype being shared among these two subkingdoms. The Malesian and Sino‐Himalayan Forest subkingdoms had five and 10 haplotypes, respectively, while the relatively large Sino‐Japanese Forest subkingdom had only eight. The strong geography–haplotype correlation persisted at the regional floristic level, with most regions possessing a unique set of haplotypes, except for the central China region. Strong landscape effects were observed in the Hengduan and Dabashan mountains, where steep mountains and valleys might have been natural dispersal barriers. The molecular phylogenetic data, together with the geographic distribution of the haplotypes, suggest the existence of several localized refugia during the last glaciation from which the present‐day distribution may be derived. The pattern of haplotype distribution across China and North Vietnam corresponded well with the current taxonomic delineation of the three intraspecific varieties of T. wallichiana.

Distribution of living Cupressaceae reflects the breakup of Pangea

Most extant genus-level radiations in gymnosperms are of Oligocene age or younger, reflecting widespread extinction during climate cooling at the Oligocene/Miocene boundary [∼23 million years ago (Ma)]. Recent biogeographic studies have revealed many instances of long-distance dispersal in gymnosperms as well as in angiosperms. Acting together, extinction and long-distance dispersal are likely to erase historical biogeographic signals. Notwithstanding this problem, we show that phylogenetic relationships in the gymnosperm family Cupressaceae (162 species, 32 genera) exhibit patterns expected from the Jurassic/Cretaceous breakup of Pangea. A phylogeny was generated for 122 representatives covering all genera, using up to 10,000 nucleotides of plastid, mitochondrial, and nuclear sequence per species. Relying on 16 fossil calibration points and three molecular dating methods, we show that Cupressaceae originated during the Triassic, when Pangea was intact. Vicariance between the two subfamilies, the Laurasian Cupressoideae and the Gondwanan Callitroideae, occurred around 153 Ma (124–183 Ma), when Gondwana and Laurasia were separating. Three further intercontinental disjunctions involving the Northern and Southern Hemisphere are coincidental with or immediately followed the breakup of Pangea.

Evolutionary relationships of the New Caledonian heterotrophic conifer, Parasitaxus usta (Podocarpaceae), inferred from chloroplast trnL-F intron/spacer and nuclear rDNA ITS2 sequences

Abstract. The phylogenetic position of Parasitaxus (Podocarpaceae) has been inferred from a cladistic analysis of molecular characters from chloroplast and nuclear genomes including all genera of Podocarpaceae. In all 24 most parsimonious trees, based on combined datasets, Phyllocladus resided outside Podocarpaceae s. str. while Lepidothamnus was basal to the latter. Most other genera were arranged in two major clades. The evidence confirms previous studies, which have suggested a relationship between Lagarostrobos, Manoao and Parasitaxus. Parasitaxus is not directly related to its host Falcatifolium taxoides. Instead it appears to be most closely related to Manoao and Lagarostrobos. No other members of this group now occur on New Caledonia. However, if the evolution of Parasitaxus were autochthonous, a free-living member of this group must once have occurred there. An accelerated evolutionary rate of the chloroplast sequence analysed was suggested, indicating that the plant behaves like a holoparasite.

Pollen morphology and infra-generic evolutionary relationships in some Chinese species of Pedicularis (Scrophulariaceae)

Abstract. The pollen grains of 32 Chinese species of Pedicularis representing 13 groups within the genus were investigated using light microscopy and scanning electron microscopy. The genus is eurypalynous, the apertures may be tricolpate, trisyncolpate, or bisyncolpate and five types of surface ornamentation (microscabrate, microrugulate, retipilate, microreticulate and microfoveolate) were observed. Comparison of the different aperture types using light microscopy allows three pollen types to be distinguished. Examination of exine ornamentation with scanning electron microscopy enabled each pollen type to be divided into two or three sub-types (giving a total of seven sub-types). Pollen morphology within the genus is discussed in relation to infrageneric relationships, evolutionary and pollination biology. There is little correlation with the existing infrageneric taxonomy (some taxonomic groups have more than one pollen type, while the same pollen type may be found in several different species-groups), but greater correlation with the corolla morphology.

Evolutionary Diversification of New Caledonian Araucaria

New Caledonia is a global biodiversity hotspot. Hypotheses for its biotic richness suggest either that the island is a ‘museum’ for an old Gondwana biota or alternatively it has developed following relatively recent long distance dispersal and in situ radiation. The conifer genus Araucaria (Araucariaceae) comprises 19 species globally with 13 endemic to this island. With a typically Gondwanan distribution, Araucaria is particularly well suited to testing alternative biogeographic hypotheses concerning the origins of New Caledonian biota. We derived phylogenetic estimates using 11 plastid and rDNA ITS2 sequence data for a complete sampling of Araucaria (including multiple accessions of each of the 13 New Caledonian Araucaria species). In addition, we developed a dataset comprising 4 plastid regions for a wider taxon sample to facilitate fossil based molecular dating. Following statistical analyses to identify a credible and internally consistent set of fossil constraints, divergence times estimated using a Bayesian relaxed clock approach were contrasted with geological scenarios to explore the biogeographic history of Araucaria. The phylogenetic data resolve relationships within Araucariaceae and among the main lineages in Araucaria, but provide limited resolution within the monophyletic New Caledonian species group. Divergence time estimates suggest a Late Cretaceous-Cenozoic radiation of extant Araucaria and a Neogene radiation of the New Caledonian lineage. A molecular timescale for the evolution of Araucariaceae supports a relatively recent radiation, and suggests that earlier (pre-Cenozoic) fossil types assigned to Araucaria may have affinities elsewhere in Araucariaceae. While additional data will be required to adequately resolve relationships among the New Caledonian species, their recent origin is consistent with overwater dispersal following Eocene emersion of New Caledonia but is too old to support a single dispersal from Australia to Norfolk Island for the radiation of the Pacific Araucaria sect. Eutacta clade.

Karyotypes of thirteen species of Pedicularis (Orobanchaceae) from the Hengduan Mountains Region, NW Yunnan, China

Abstract Karyotypes of thirteen species (including 3 subspecies, 2 varieties) of Pedicularis L. (Orobanchaceae) from the Hengduan Mountains Region, NW Yunnan, China were investigated. Twelve species of them were reported for the first time. The species examined all had one or other of two basic chromosome numbers: 2n=14 and 2n=16. All species investigated are diploid and share the same type of choromocenters in prophase nuclei, but differed in their interphase nuclei. The species with 2n=14 have the simple chromocenter type of interphase nuclei, while those with 2n=16 have the complex chromocenter type of interphase nuclei. These results confirm former reports, which have shown that 2n=16 is by far the most common number in this genus. Based on the karyomorphological evidence as well as morphological characters, relationships between the species studied are discussed.

Conservation genetics and phylogenetics of New Caledonian Retrophyllum (Podocarpaceae) species

Abstract Retrophyllum is a genus in the Podocarpaceae consisting of five species with a disjunct distribution in the Southern Hemisphere. Support for the monophyly of the genus, and its sister group relationship to an Afrocarpus‐Nageia clade, was obtained from trnL‐F sequences. Within Retrophyllum, the Melanesian species (R. minus, R. comptonii, R. vitiense) formed a monophyletic group, sister to the South American species R. rospigliosii. This topology is consistent with Gondwanan fragmentation, although the amount of nucleotide substitutions between taxa is surprisingly small for such an ancient disjunction. We were unable to distinguish between historical long distance dispersal or slow substitution rates as the source of this discrepancy. Two of the Retrophyllum species are endemic to New Caledonia; one of these (R. minus) is endangered with less than 2500 individuals remaining in the wild. The other endemic species (R. comptonii) is more widespread. We have used a combination of chloroplast RFLPs and RAPDs to assess the distinctness of these two taxa that can be difficult to distinguish using morphological characters. Both techniques provided taxon‐specific markers that allowed the discrimination of the two species and the clarification of uncertain identifications. Within R. comptonii we detected evidence for intra‐specific genetic differentiation corresponding to geographical isolation of populations.

The taxa of Scottish bracken in a European perspective

Summary In contrast to the traditional view that Scottish Bracken (Pteridium Scop., Hypolepidaceae sensu Page, 1976) is a single, uniform taxon, evidence is presented that two species, each represented by multiple subspecies, are present in Scotland. These belong to two different species complexes within Pteridium, the P. aquilinum complex and the P. latiusculum complex. The P. aquilinum complex is represented by P. aquilinum (L.) Kuhn, with at least three subspecies: subsp. aquilinum, subsp. atlanticum C.N. Page and subsp. fulvum C.N. Page. The P. latiusculum complex is represented by P. pinetorum C.N. Page & R.R. Mill with at least two subspecies, subsp. pinetorum and subsp. osmundaceum (Christ) C.N. Page. Only P. aquilinum subsp. aquilinum is an aggressive weed which is a widespread problem to man; the others are rare. The paper establishes the nomenclatural priorities, typification, taxonomy, morphology, known distribution and ecology of all bracken taxa so far known from Scotland. The typification of...

Scottish bracken (Pteridium): New taxa and a new combination

Summary In advance of two forthcoming works in which the names will be used, one new species of Pteridium (P. pinetorum C.N. Page & R.R. Mill) and one new subspecies (P. aquilinum (L.) Kuhn subsp. fulvum C.N. Page) are formally described, and one new combination made (P. pinetorum C.N. Page & R .R. Mill subsp. osmundaceum (Christ) C. N. Page, comb, et stat. nov.).

Cuticle Micromorphology of Caribbean and Central American Species of Podocarpus (Podocarpaceae)

The cuticle micromorphology of leaves of 13 species of Podocarpus (Podocarpaceae), nine from the Caribbean Islands and four from Central America, was studied with scanning electron microscopy. They include five of the seven species of section Pumilis (Podocarpus aristulatus, P. buchii, P. ekmanii, P. urbanii, and P. victorinianus), four of the seven species of section Nemoralis (P. guatemalensis, P. hispaniolensis, P. purdieanus, and P. trinitensis), three of the six species of section Lanceolatus (P. coriaceus, P. costaricensis, and P. matudae), and one of the three species of section Pratensis (P. oleifolius). The external and internal features of the adaxial and abaxial cuticles are described for all species and are compared with other known Podocarpus species (especially section Scytopodium). Leaves are hypostomatic, with stomata arranged in discontinuous rows parallel to the leaf axis. The external cuticles of all studied species possessed Florin rings. Stomatal plugs were observed in all species except P. buchii and P. costaricensis. The number of subsidiary cells varies from two to six, with two or three being most common. Polar subsidiary cells are constantly absent in seven species and present in six species, although in three of these, they are sometimes absent. The internal cuticle on subsidiary cell surfaces is smooth to slightly rugose and is sometimes pitted. The cuticle on guard cell surfaces is usually granular to rugose, sometimes with pits. Polar extensions occur in all species; they are thin in the studied species of section Pumilis but thick in those belonging to the other three sections. Epidermal cell outlines are straight to undulating. The cuticle on epidermal cell surfaces is rugose and pitted in all the Caribbean species except for P. trinitensis but much smoother to granular in P. trinitensis and the Central American species. The most useful characters to distinguish species are the micromorphology of the cuticle on guard cell surfaces, the presence or absence of polar subsidiary cells, the periclinal epidermal cell texture, and the epidermal cell shape and size. No synapomorphic characters of the leaf cuticle were found that supported any of the sections proposed in the 1985 revision of Podocarpus by de Laubenfels, but some qualitative characters were correlated with geographical distribution. Quantitative characters showed considerable variation between species, often providing distinguishing characters, but none of this variation was correlated either with the current taxonomic classification or with geography.