Andrew P. Brown

Impact of two wildfires on endemic granite outcrop vegetation in Western Australia

Abstract In seasonally dry regions of the world fire is a recurring disturbance but little is known of how fire interacts with granite outcrop vegetation. We hypothesize that the floristic composition in granite vegetation, usually attributed to the edaphic environment, may also reflect the impact of disturbances such as fire. Dramatic differences in floristic composition and cover over 13 years and two fires were observed in vegetation on a Western Australian granite outcrop. This was very marked in the first year following the two fires, with annuals and geophytes showing the greatest turnover of species. Even among the perennial shrubs there was considerable turnover in a number of obligate seeders. After the first fire the number of species declined for woody perennials, herbaceous perennials and annuals, remained unchanged for perennial grasses and sedges, and varied with highest richness 4 yr after fire for geophytes. Demographic studies of two endemic woody obligate seeders and three endemic mallee eucalypt resprouters similarly showed dramatic differences within and between species in seedling recruitment following the two fires. Fire does have a significant impact on the floristic composition of semi-arid granite outcrop vegetation communities. Studies on other granite outcrop systems are needed to test the generality of this conclusion. Nomenclature: follows the database of Western Australian plant names maintained by the Western Australian Herbarium (Paczkowska & Chapman 2000).

Robert Brown's Caladenia revisited, including a revision of its sister genera Cyanicula, Ericksonella and Pheladenia (Caladeniinae: Orchidaceae)

Nomenclatural confusion has been generated regarding the large Australasian terrestrial orchid genus Caladenia following publication from 2001 onwards of three major treatments of Caladeniinae. Here, we review concepts for Caladenia and allied genera in the subtribe, we revise three sister genera of Caladenia (Cyanicula, Ericksonella and Pheladenia), and we present an annotated nomenclatural checklist with many new synonymies and some new combinations. A revised circumscription of ten genera in the Caladeniinae is presented, including both Adenochilus and Eriochilus, which have recently been segregated as monogeneric subtribes by others. We argue for retaining Caladenia in the broad sense, largely reflecting Robert Browns original concept, differing only in the recognition as genera of Cyanicula, Pheladenia, and Leptoceras, as well as two monotypic genera not known to Brown but later described as species of Caladenia (Praecoxanthus and Ericksonella). Thus Caladenia remains a large Australasian genus of terrestrial orchids with 243 species and six subgenera. This approach maximises nomenclatural stability while ensuring that hypothesised monophyly is upheld in the light of molecular phylogenetics analyses. The valid type for Caladenia is C. carnea, while that for Caladenia sect. Calonema is C. longicauda. The genus Jonesiopsis and generic combination Phlebochilus (Benth.) Szlach. were validly published. These conclusions call into question many recently erected taxa and combinations of other authors. Synonyms of Caladenia include Arachnorchis, Calonemorchis, Drakonorchis, Jonesiopsis, Petalochilus, Phlebochilus and Stegostyla. Pentisia is a synonym of Cyanicula. Calonema (Lindl.) Szlach. and Calonema (Lindl.) D.L. Jones and M.A. Clem. are invalid generic combinations as the name Calonema had already been used for a fungal genus. New taxa described herein include Ericksonella, Cyanicula subgenus Trilobatae, C. aperta, C. ixioides subsp. candida, × Cyanthera and × C. glossodioides. New combinations include Caladenia subgenus Stegostyla (D.L. Jones and M.A. Clem.) Hopper and A.P. Br., C. graniticola (Hopper and A.P. Br.) Hopper and A.P. Br., C. saccata (R.S. Rogers) Hopper & A.P. Br., C. orientalis (G.W. Carr) Hopper & A.P. Br., and C. villosissima (G.W. Carr) Hopper & A.P. Br., and Ericksonella saccharata (Reichb.f.) Hopper and A.P.Br.

A revision of Australia’s hammer orchids (Drakaea: Orchidaceae), with some field data on species-specific sexually deceived wasp pollinators

Drakaea Lindley, 1840 is a genus of 10 species of geophytic orchids endemic to the South-west Australian Floristic Region. The genus is renowned for its morphological and chemical adaptations, achieving pollination by sexual deception of male thynnid wasps. The history of taxa in Drakaea has been one of dispute and confusion right to the present day. Here we provide a revision of the genus, the first made by using modern collections and field data, formalising names for undescribed taxa featured by Hoffman and Brown (1992, 1998), several of which are threatened with extinction. We describe six new species: D. andrewsiae, D. concolor, D. confluens, D. gracilis, D. isolata and D. micrantha. Experimental baiting of male wasps has helped show the specific status of some of these new taxa. Molecular phylogenetic research is needed to clarify relationships and patterns of speciation in the genus. Five of the 10 Drakaea species are legally protected under the Western Australian Wildlife Conservation Act and the Commonwealth Environment Protection and Biodiversity Conservation Act, signalling the ongoing need for research and management to ensure the conservation of this unique part of Australia’s orchid heritage. D. andrewsiae has been recorded only three times from the Gnowangerup–Tunney district. Urgent surveys are needed to establish its conservation status.

Biogeography of Caladenia (Orchidaceae), with special reference to the South-west Australian Floristic Region

Caladenia contains 376 species and subspecies, of which almost all are endemic to temperate and southern semiarid Australia. Eleven species occur in New Zealand, 10 of which are endemic, and one species is widely distributed in eastern Australia and the western Pacific. Only three species occur in both south-western and south-eastern Australia. At subgeneric level, Drakonorchis is endemic to the South-west Australian Floristic Region (SWAFR), Stegostyla to eastern Australia and New Zealand, whereas three subgenera, Calonema, Phlebochilus and Elevatae occur on both sides of the Nullarbor Plain. Subgenus Caladenia is primarily eastern Australian but also extends to the western Pacific. The largest subgenera (Calonema and Phlebochilus) have radiated extensively, with Calonema exhibiting a greater concentration of species in more mesic parts of the SWAFR than Phlebochilus. Within the SWAFR, the major biogeographic division within Caladenia follows the 600-mm isohyet. Within rainfall zones, biogeographic districts for Caladenia correlate with a combination of underlying geology and surface soils. Areas of high endemism contain diverse edaphic environments. Climatic and edaphic requirements are likely to be key drivers of rarity in Caladenia, although these parameters may be acting in concert with mycorrhizal and pollinator specificity.

Australia’s wasp-pollinated flying duck orchids revised (Paracaleana: Orchidaceae)

We uphold the generic rank of Paracaleana on the basis of its divergent pollination syndrome (sexual deception of male thynnid wasps compared with pollination of Caleana by male sawflies), recent DNA sequence data demonstrating monophyly, and nomenclatural stability. Ten of the 13 species recognised herein are new, all endemic to the South-west Australian Floristic Region: Paracaleana alcockii, P. brockmanii, P. dixonii, P. gracilicordata, P. granitica, P. hortiorum, P. lyonsii, P. parvula, P. terminalis and P. triens. Although some of these taxa have subtle morphological differences, primarily of labellum morphology, evidence from other Australian orchid genera whose flowers sexually deceive wasp pollinators indicates that reproductive isolation is probable among close sister taxa in Paracaleana. Moreover, phenological, ecological and geographical differences help separate morphologically close sister taxa. P. disjuncta D.L. Jones is considered to extend from Victoria and South Australia west into the South-west Australian Floristic Region, where James Drummond first collected the species, probably in 1838. Additional research is needed on pollinators, molecular phylogeny, possibly undescribed taxa within P. nigrita and on the few putative hybrids identified in the genus.

Habitat characteristics of the rare underground orchid Rhizanthella gardneri

Rhizanthella gardneri R.S.Rogers is an entirely subterranean mycoheterotrophic orchid known only from two isolated populations within south-western Western Australia (WA). This rare species appears restricted to habitats dominated by species of the Melaleuca uncinata complex. R. gardneri purportedly forms a tripartite relationship with Melaleuca1, via a connecting mycorrhizal fungus, for the purpose of carbohydrate and nutrient acquisition. Here, we quantify key climate, soil and vegetation characteristics of known R. gardneri habitats to provide baseline data for monitoring of known R. gardneri populations, to better understand how R. gardneri interacts with its habitat and to identify possible new sites for R. gardneri introduction. We found that the habitats of the two known R. gardneri populations show considerable differences in soil chemistry, Melaleuca structure and Melaleuca productivity. Multivariate analyses showed that both multidimensional scaling (MDS) and principal components analysis (PCA) ordinations of soil chemical characteristics were very similar. Individual sites within populations were relatively similar in all attributes measured, whereas overall northern and southern habitats were distinct from each other. These results suggest that R. gardneri can tolerate a range of conditions and may be more widespread than previously thought, given that there are extensive areas of Melaleuca thickets with similar habitat characteristics across south-western WA. Variability within the habitats of known R. gardneri populations suggests translocation of this species into sites with similar vegetation may be a viable option for the survival of this species.

Dormancy in Caladenia: a Bayesian approach to evaluating latency

Dormancy is common in many terrestrial orchids in southern Australia and other temperate environments. The difficulty for conservation and management when considering dormancy is ascertaining whether non-emergent plants aredormantordead.Hereweuseamulti-statecapture-recapturemethod,undertakenoverseveralseasons,todeterminethe likelihood of a plant becoming dormant or dying following its annual emergent period and evaluate the frequency of the lengthofdormancy.Weassessthetransitionprobabilitiesfromtimeseriesofvaryinglengthsforthefollowingnineterrestrial orchids in the genus Caladenia: C. amoena, C. argocalla, C. clavigera, C. elegans, C. graniticola, C. macroclavia, C. oenochila,C. rosella and C. valida from Victoria, South Australia and Western Australia. We used a Bayesian approach for estimating survivorship, dormancy and the likelihood of death from capture-recapture data. Considering all species together, the probability of surviving from one year to the next was ~86%, whereas the likelihood of observing an individual above ground in two consecutive years was ~74%. All species showed dormancy of predominantly 1 year, whereasdormancyofthreeormoreyearswasextremelyrare(<2%).Theresultshavepracticalimplicationsforconservation, in that (1) population sizes of Caladenia species are more easily estimated by being able to distinguish the likelihood of an unseen individual being dormant or dead, (2) population dynamics of individuals can be evaluated by using a 1-3-year dormancy period and (3) survey effort is not wasted on monitoring individuals that have not emerged for many years.

Population dynamics of Caladenia: Bayesian estimates of transition and extinction probabilities

A disproportionate number of threatened plant species in Australia are found in the genus Caladenia, although little has been published on their life history. Here we examine data from nine species to evaluate some of the basic life-history strategies in Caladenia, specifically the transitions between life-history stages. We constructed life-history transition models of the orchids by using a Bayesian approach, we evaluated the growth rate of populations, compared transition values among species and determined which stage influenced the population growth most. We assessed extinction likelihood and considered the effect of variation in transitions among states on the probability of extinction. Bayesian model selection showed differences between species regarding their life cycle. The probability of individuals flowering in two consecutive years is extremely rare and was found to be common in only one species, C. amoena. All other species had a high likelihood of returning to a vegetative state, and some were likely to enter dormancy after flowering. High elasticities in the transition from the dormant to dormant stage suggest that dormancy has a large impact on population persistence. The quasi-extinction rate suggests that C. rosella, C. clavigera, C. graniticola and C. macroclavia are most at risk when all species have an equal initial population size. Conservation management should focus on studies to identify cues that influence flowering in consecutive years, emergence from dormancy and increasing recruitment.