Lyn A. Craven

Evolution of exceptional species richness among lineages of fleshy-fruited Myrtaceae

BACKGROUND AND AIMS The angiosperm family Myrtaceae comprises 17 tribes with more than half of the estimated 5500 species being referred to the fleshy-fruited and predominantly rainforest associated Syzygieae and Myrteae. Previous studies suggest that fleshy fruits have evolved separately in these lineages, whereas generally shifts in fruit morphology have been variously implicated in diversification rate shifts among angiosperms. A phylogenetic hypothesis and estimate divergence times for Myrtaceae is developed as a basis to explore the evidence for, and drivers of, elevated diversification rates among the fleshy-fruited tribes of Myrtaceae. METHODS Bayesian phylogenetic analyses of plastid and nuclear DNA sequences were used to estimate intertribal relationships and lineage divergence times in Myrtaceae. Focusing on the fleshy-fruited tribes, a variety of statistical approaches were used to assess diversification rates and diversification rate shifts across the family. KEY RESULTS Analyses of the sequence data provide a strongly supported phylogenetic hypothesis for Myrtaceae. Relative to previous studies, substantially younger ages for many of the clades are reported, and it is argued that the use of flexible calibrations to incorporate fossil data provides more realistic divergence estimates than the use of errorless point calibrations. It is found that Syzygieae and Myrteae have experienced elevated diversification rates relative to other lineages of Myrtaceae. Positive shifts in diversification rate have occurred separately in each lineage, associated with a shift from dry to fleshy fruit. CONCLUSIONS Fleshy fruits have evolved independently in Syzygieae and Myrteae, and this is accompanied by exceptional diversification rate shifts in both instances, suggesting that the evolution of fleshy fruits is a key innovation for rainforest Myrtaceae. Noting the scale dependency of this hypothesis, more complex explanations may be required to explain diversification rate shifts occurring within the fleshy-fruited tribes, and the suggested phylogenetic hypothesis provides an appropriate framework for this undertaking.

Phylogeny of Hibiscus and the Tribe Hibisceae (Malvaceae) Using Chloroplast DNA Sequences of ndhF and the rpl16 Intron

Abstract Circumscriptions of the genus Hibiscus and the tribe Hibisceae (Malvaceae) are based on morphological features that are not unique in the family. An examination of the literature regarding putatively ancestral morphological features revealed that Hibiscus and Hibisceae may be defined by shared ancestral features, and thus are unlikely to be monophyletic groups. These phylogenetic hypotheses were tested using two chloroplast DNA sequences (a coding region—ndhF, and a non-coding region—the rpl16 intron). Several genera usually placed in Hibisceae were found to occupy positions sister to the rest of the family, as was predicted from our reevaluation of their morphological features. Although the earliest divergences in the family were not resolved by chloroplast DNA topologies alone, several morphological features, when analysed in combination with ndhF, suggested a possible resolution of the basal polytomy. These early divergences are represented by extant genera with relatively restricted distributions, which all possess Australasian species that are sister to more widespread and diverse lineages. This suggests the novel hypothesis that eastern Gondwana may be the centre of origin of the family. The pollen fossil record is consistent with this possibility, but does not support it unambiguously. Unexpectedly the tribes Decaschistieae and Malvavisceae as well as other genera of Hibisceae nest within Hibiscus. Nomenclatural upheavals concerning Hibiscus, one of the worlds most popular horticultural plant genera, will be difficult to avoid. Communicating Editor: James F. Smith

Molecular Systematics of Australian Gossypium section Grandicalyx (Malvaceae)

Australian Gossypium consists of 17 species classified into three sections. The largest and most poorly understood is the group of 12 species in sect. Grandicalyx that occur in the Kimberley and Cobourg regions of NW Australia. These areas are characterized by annual monsoon rains and dry-season fires. Species in sect. Grandicalyx exhibit a suite of morphological and ecological features that are otherwise unknown in the genus and that apparently evolved in response to seasonal fires and ant mutualism. These features include an herbaceous perennial habit, the ability to regenerate from thickened rootstocks following fires and ex-

Acacia: The case against moving the type to Australia

Recent studies have shown that Acacia is polyphyletic and must be split into five genera. Proposal 1584 would retypify Acacia : the type of the Australian taxon A. penninervis would be conserved over the current lectotype ( A. scorpioides ) of an African taxon. We disagree with the recommendation of the Spermatophyte Committee to endorse this proposal. Contrary to Article 14.12 of the ICBN, no detailed case against conservation was presented in Proposal 1584. We maintain that there are strong arguments against conservation, such as the large number of countries that would be affected, the economic importance of the extra-Australian species, and the economic burden placed on developing countries. Acceptance of this proposal would also violate the guidelines for conservation which clearly state that the principle of priority should prevail when conservation for one part of the world would create disadvantageous change in another part of the world.

Molecular systematics of Syzygium and allied genera (Myrtaceae) : evidence from the chloroplast genome

With as many as 1000 included species, Syzygium s.l. (including Syzygium and segregate genera such as Acmena, Acmenosperma, Cleistocalyx, Piliocalyx, and Waterhousea) comprises one of the major lineages within Myrtaceae, and is an important component of the Old-World tropical rainforest flora. As with other large genera, high species richness, an extensive distribution and relative homogeneity in morphology have hindered attempts to divide Syzygium s.l. Here, we investigate higher level relationships within the group, using parsimony and Bayesian analyses of cpDNA sequences from the matK and ndhF genes and the rpl 16 intron, generated for a total of 87 species from the Syzygium group and eight outgroup taxa. Within the ingroup, four major well supported clades are found, which form a basal polytomy along with S. wesa and monotypic Anetholea. Generally, the molecular data provide little support for traditional divisions of Syzygium s.l., and the recognition of segregate groups such as Acmena, Acmenosperma, Cleistocalyx, Piliocalyx and Waterhousea. While homoplasy amongst morphological characters has misled attempts to divide the group, detailed and critical assessments of placental, ovular and seed morphology may provide novel insights into evolutionary relationships, and are an important future step in the development of a sound higher level taxonomy for Syzygium s.l.

An infrageneric classification of Syzygium (Myrtaceae)

An infrageneric classification of Syzygium based upon evolutionary relationships as inferred from analyses of nuclear and plastid DNA sequence data, and supported by morphological evidence, is presented. Six subgenera and seven sections are recognised. An identification key is provided and names proposed for two species newly transferred to Syzygium.

Genetic congruence with new species boundaries in the Melaleuca uncinata complex (Myrtaceae)

Uninformed management decisions have the potential to create significant problems for conservation programs. In the south-western corner of Australia where conservation initiatives are directed towards restoring large tracts of land degraded by broadscale clearing and increasing levels of dryland salinity, Melaleuca uncinata R.Br. (Myrtaceae) is a species complex of considerable interest for restoration. Although M. uncinata is morphologically uniform across most of southern mainland Australia, there is considerable variation in south-western Australia and a recent morphological evaluation has recognised 11 species. Phylogenetic patterns among populations of seven of these species were examined with nuclear RFLP loci to determine whether morphological and phylogenetic boundaries were congruent before the implementation of any broadscale revegetation programs. The phylogenetic analysis was congruent with the morphological assessment, and populations of different species, including those co-occurring at the same site, clustered according to their correct morphological assignment. Some genetic structuring associated with habitat preference was also evident within two of the species. The taxonomic resolution and knowledge of the phylogenetic relationships among the seven species will facilitate their further assessment for issues relevant to revegetation, such as provenance and local adaptation. It will also enable selection of appropriate germplasm in revegetation programs to maximise the genetic adaptation in restoration and minimise negative impact of plantings on remnant vegetation.

The Leaf Essential Oils of the Australian Members of the Genus Callistemon (Myrtaceae)

Abstract The majority of Australian species (30) of the genus Callistemon gave leaf essential oils with 1,8-cineole as the major component (45–80%). Other compounds present in these species included α-pinene (2–40%, the majority being 2–8%), limonene (2–9%, the majority being 5–8%) and α-terpineol (1–13%, the majority being 5–10%). The species that produced these oils did so in oil yields of 0.1–1.0%. The species giving very low oil yields (<0.1%), viz. C. brachyandrus, C. montanus, C. polandii, C. teretifolius, C. sp. (Walshs Pyramid P.I. Forster 13767), C. sp. nov. “Oakey,” C. pachyphyllus, as a general rule, produced oils in which the amount of 1,8-cineole was low (<20%) and generally there was a preponderance of sesquiterpenes.

Pollen morphology of the Myrtaceae. Part 1: tribes Eucalypteae, Lophostemoneae, Syncarpieae, Xanthostemoneae and subfamily Psiloxyloideae

A family-wide palynological study of Myrtaceae was conducted using scanning electron microscopy (SEM) and light microscopy (LM). In this part of the study, the pollen morphology of 18 genera and 150 species from the Myrtaceae tribes of subfamily Myrtoideae, Eucalypteae, Lophostemoneae, Syncarpieae, Xanthostemoneae and subfamily Psiloxyloideae are presented. It was found that the most commonly observed pollen in these groups was parasyncolpate with a rugulate exine, whereas some species possessed an apocolpial island. The large, and sometimes syndemicolpate, pollen of Eucalypteae genera Angophora and Corymbia differed from all other genera. Most Eucalyptus pollen had endopores with a thickened exine.

Pollen morphology of the Myrtaceae. Part 4: tribes Kanieae, Myrteae and Tristanieae

Pollen morphology of 44 genera and 101 species from the Myrtaceae tribes Kanieae, Myrteae and Tristanieae was surveyed using scanning electron microscopy (SEM) and light microscopy (LM). Most Myrteae pollen were brevicolpate and granulate, which is unique within Myrtaceae, and these are most likely ancestral characters for this tribe. Two main pollen types were observed in tribe Kanieae, one form being with syncolpate colpi and a distinctive granulate exine, and the other with parasyncolpate colpi and a less ornamented exine. Genera Tristania and Thaleropia of tribe Tristanieae produce the smallest pollen in Myrtaceae, whereas Octamyrtus of tribe Myrteae produces the largest pollen observed in Myrtaceae.