Richard C. Winkworth

Plant dispersal N.E.W.S from New Zealand.

Although New Zealand separated from Gondwana during the late Cretaceous (80 million years ago) it shares strong floristic affinities with other Southern Hemisphere landmasses. For 150 years, biogeographers have debated whether these similarities reflect the ancient Gondwanan connection or subsequent dispersal events. Molecular phylogenies are providing new insights into the history of Southern Hemisphere plant groups. These studies show that many plant lineages are recent arrivals in New Zealand, diversifying rapidly and then travelling to other Southern Hemisphere landmasses.

Viburnum phylogeny based on combined molecular data: Implications for taxonomy and biogeography

We investigated Viburnum phylogeny using separate and combined analyses of DNA sequence data from two chloroplast and three nuclear loci. Separate analyses of nuclear and chloroplast data sets resulted in gene trees that were generally congruent with one another and with trees from two previous analyses. Our gene trees do differ in the position of section Pseudotinus, as well as in species relationships within sections Pseudotinus and Lentago. However, tests for incongruence indicate that differences between the nuclear and chloroplast data are not significant. Furthermore, gene trees from combined analyses were highly similar to those found in separate analyses, suggesting that these localized differences do not affect other parts of the tree. Our analyses provide convincing support for numerous relationships, although there is still uncertainty at the base of the tree. To facilitate future study, we propose informal names for 12 well-supported species groups, as well as for several higher-level clades. We also discuss the biogeographic implications of our phylogeny, focusing on repeated, although apparently temporally incongruent, patterns of disjunction between the Old and New Worlds.

THE EVOLUTION OF REPRODUCTIVE CHARACTERS IN DIPSACALES

Improved knowledge of Dipsacales phylogeny provides a solid framework for studies of character evolution. Although the polarity of many characters can now be confidently established, for others it remains unclear. This results largely from uncertainty about the broader relationships of Dipsacales and is especially problematic for characters that differentiate the two basal lineages, Adoxaceae and Caprifoliaceae. Within Caprifoliaceae, changes in stamen number became decoupled from corolla evolution, a reduction from five to four stamens, coinciding with the origin of the Linnina clade. Subsequently, there was a reduction to two stamens within Morinaceae and to three, two, and one within Valerianaceae. In contrast, within Adoxaceae, stamen number covaries with the number of corolla lobes, although the number of stamens was effectively doubled within Adoxina by the division of each stamen. Fleshy fruits may have evolved separately in Adoxaceae and in Caprifolieae. These vary in the number of seeds and in the presence or absence of an endocarp and show repeated patterns in the evolution of color, perhaps underlain by shifts in the timing of developmental events. In Caprifoliaceae, dry fruits include bicarpellate septicidal capsules in Diervilleae and initially tricarpellate, single‐seeded achenes in Linnina. Achene fruits exhibit a variety of independently evolved dispersal mechanisms, especially involving modifications of the calyx lobes or bracts subtending the ovary. Within Linnina, a distinctive epicalyx surrounding the ovary appears to have originated through the fusion of supernumerary bracts. It is possible that the epicalyx evolved twice, once in the ancestor of the Morinaceae and again in the Triplostegia‐Dipsacaceae clade. Within the Dipsacaceae, modifications of the epicalyx parallel those of the ovary and calyx within Valerianaceae, suggesting a transference of function involving homeoheterotopy. Evolutionary adjustments of the epicalyx, calyx, and ovary wall in relation to protection and dispersal may have established an evolutionarily stable configuration.

Viburnum Phylogeny Based on Chloroplast trnK Intron and Nuclear Ribosomal ITS DNA Sequences

Abstract Phylogenetic analyses of chloroplast trnK intron and nuclear ribosomal ITS DNA sequences yield significant improvements in our understanding of relationships, character evolution, and biogeography in Viburnum (Adoxaceae). We confirm that most of the ten traditionally recognized sections are monophyletic. The most striking exception is Odontotinus, which is divided into: (i) a purple-fruited New World clade within which the Latin American section Oreinotinus is nested, and (ii) an Old World, mostly red-fruited clade that is closely related to V. cylindricum (section Megalotinus) and the New World, purple-fruited V. acerifolium. We identify three major supra-sectional groupings: (i) a clade consisting of the Odontotinus-Oreinotinus-Megalotinus complex, the circum-boreal section Opulus, and the Eurasian section Tinus, (ii) a clade containing the Old World section Viburnum, the New World section Lentago, and, with less support, section Pseudotinus, and (iii) a clade containing the Asian sections Tomentosa and Solenotinus. Two species are not clearly allied to any of these supra-sectional clades: V. urceolatum, a Taiwanese/Japanese species traditionally placed in section Viburnum, and V. clemensiae, a Bornean species previously assigned to section Solenotinus. The placement of the root also remains uncertain, but probably does not fall within any of the three major supra-sectional clades. Knowledge of relationships within sections is useful in clarifying historical biogeography and the evolution of sterile flowers and fruit color. The one case of conflict between datasets highlights a possible instance of homoploid hybrid speciation.

Biogeographic Interpretation of Splits Graphs: Least Squares Optimization of Branch Lengths

Although most often used to represent phylogenetic uncertainty, network methods are also potentially useful for describing the phylogenetic complexity expected to characterize recent species radiations. One network method with particular advantages in this context is split decomposition. However, in its standard implementation this approach is limited by a conservative criterion for branch length estimation. Here we extend the utility of split decomposition by introducing a least squares optimization technique for correcting branch lengths that may be underestimated by the standard implementation. This optimization of branch lengths is generally expected to improve divergence time estimates calculated from splits graphs. We illustrate the effect of least squares optimization on such estimates using the Australasian Myosotis and the Hawaiian silversword alliance as examples. We also discuss the biogeographic interpretation and limitations of splits graphs.

Markers derived from amplified fragment length polymorphism gels for plant ecology and evolution studies

We describe the types of polymerase chain reaction (PCR) markers that we have isolated using amplified fragment length polymorphisms (AFLP) in closely related taxa from diverse plant genera. With these markers, both inter‐ and intraspecific differences have been identified. The characterization of the nucleotide sequences and fragment length polymorphisms of such AFLP‐derived PCR markers is promising for investigating the ecology and evolution of closely related plant taxa.

Mitochondrial sequence data and Dipsacales phylogeny: mixed models, partitioned Bayesian analyses, and model selection.

Phylogenetic analyses of chloroplast DNA sequences, morphology, and combined data have provided consistent support for many of the major branches within the angiosperm clade Dipsacales. Here we use sequences from three mitochondrial loci to test the existing broad scale phylogeny and in an attempt to resolve several relationships that have remained uncertain. Parsimony, maximum likelihood, and Bayesian analyses of a combined mitochondrial data set recover trees broadly consistent with previous studies, although resolution and support are lower than in the largest chloroplast analyses. Combining chloroplast and mitochondrial data results in a generally well-resolved and very strongly supported topology but the previously recognized problem areas remain. To investigate why these relationships have been difficult to resolve we conducted a series of experiments using different data partitions and heterogeneous substitution models. Usually more complex modeling schemes are favored regardless of the partitions recognized but model choice had little effect on topology or support values. In contrast there are consistent but weakly supported differences in the topologies recovered from coding and non-coding matrices. These conflicts directly correspond to relationships that were poorly resolved in analyses of the full combined chloroplast-mitochondrial data set. We suggest incongruent signal has contributed to our inability to confidently resolve these problem areas.

Phylogeny and colonization history of Pringlea antiscorbutica (Brassicaceae), an emblematic endemic from the South Indian Ocean Province.

The origins and evolution of sub-Antarctic island floras are not well understood. In particular there is uncertainty about the ages of the contemporary floras and the ultimate origins of the lineages they contain. Pringlea R. Br. (Brassicaceae) is a monotypic genus endemic to four sub-Antarctic island groups in the southern Indian Ocean. Here we used sequences from both the chloroplast and nuclear genomes to examine the phylogenetic position of this enigmatic genus. Our analyses confirm that Pringlea falls within the tribe Thelypodieae and provide a preliminary view of its relationships within the group. Divergence time estimates and ancestral area reconstructions imply Pringlea diverged from a South American ancestor ~5 Myr ago. It remains unclear whether the ancestor of Pringlea dispersed directly to the South Indian Ocean Province (SIOP) or used Antarctica as a stepping-stone; what is clear, however, is that following arrival in the SIOP several additional long-distance dispersal events must be inferred to explain the current distribution of this species. Our analyses also suggest that although Pringlea is likely to have inherited cold tolerance from its closest relatives, the distinctive morphology of this species evolved only after it split from the South American lineage. More generally, our results lend support to the hypothesis that angiosperms persisted on the sub-Antarctic islands throughout the Pliocene and Pleistocene. Taken together with evidence from other sub-Antarctic island plant groups, they suggest the extant flora of sub-Antarctic is likely to have been assembled over a broad time period and from lineages with distinctive biogeographic histories.

New insights into Trimezieae (Iridaceae) phylogeny: what do molecular data tell us?

BACKGROUND AND AIMS The Neotropical tribe Trimezieae are taxonomically difficult. They are generally characterized by the absence of the features used to delimit their sister group Tigridieae. Delimiting the four genera that make up Trimezieae is also problematic. Previous family-level phylogenetic analyses have not examined the monophyly of the tribe or relationships within it. Reconstructing the phylogeny of Trimezieae will allow us to evaluate the status of the tribe and genera and to examine the suitability of characters traditionally used in their taxonomy. METHODS Maximum parsimony and Bayesian phylogenetic analyses are presented for 37 species representing all four genera of Trimezieae. Analyses were based on nrITS sequences and a combined plastid dataset. Ancestral character state reconstructions were used to investigate the evolution of ten morphological characters previously considered taxonomically useful. KEY RESULTS Analyses of nrITS and plastid datasets strongly support the monophyly of Trimezieae and recover four principal clades with varying levels of support; these clades do not correspond to the currently recognized genera. Relationships within the four clades are not consistently resolved, although the conflicting resolutions are not strongly supported in individual analyses. Ancestral character state reconstructions suggest considerable homoplasy, especially in the floral characters used to delimit Pseudotrimezia. CONCLUSIONS The results strongly support recognition of Trimezieae as a tribe but suggest that both generic- and species-level taxonomy need revision. Further molecular analyses, with increased sampling of taxa and markers, are needed to support any revision. Such analyses will help determine the causes of discordance between the plastid and nuclear data and provide a framework for identifying potential morphological synapomorphies for infra-tribal groups. The results also suggest Trimezieae provide a promising model for evolutionary research.

Long-lasting modification of soil fungal diversity associated with the introduction of rabbits to a remote sub-Antarctic archipelago

During the late nineteenth century, Europeans introduced rabbits to many of the sub-Antarctic islands, environments that prior to this had been devoid of mammalian herbivores. The impacts of rabbits on indigenous ecosystems are well studied; notably, they cause dramatic changes in plant communities and promote soil erosion. However, the responses of fungal communities to such biotic disturbances remain unexplored. We used metabarcoding of soil extracellular DNA to assess the diversity of plant and fungal communities at sites on the sub-Antarctic Kerguelen Islands with contrasting histories of disturbance by rabbits. Our results suggest that on these islands, the simplification of plant communities and increased erosion resulting from the introduction of rabbits have driven compositional changes, including diversity reductions, in indigenous soil fungal communities. Moreover, there is no indication of recovery at sites from which rabbits were removed 20 years ago. These results imply that introduced herbivores have long-lasting and multifaceted effects on fungal biodiversity as well as highlight the low resiliency of sub-Antarctic ecosystems.