LANKESTERIANA 7(1-2): 229-239. 2007. DENSITY INDUCED RATES OF POLLINARIA REMOVAL AND DEPOSITION IN THE PURPLE ENAMEL-ORCHID, ELYTHRANTHERA BRUNONIS (ENDL.) A.S. GEORGE 1,10 2 3 RAYMOND L. TREMBLAY , RICHARD M. BATEMAN , ANDREW P. B ROWN , 4 5 6 7 MARC HACHADOURIAN , MICHAEL J. HUTCHINGS , SHELAGH KELL , HAROLD KOOPOWITZ , 8 9 CARLOS LEHNEBACH & DENNIS WIGHAM 1 Department of Biology, 100 Carr. 908, University of Puerto Rico – Humacao campus, Humacao, Puerto Rico, 00791-4300, USA 2 Natural History Museum, Cromwell Road, London SW7 5BD, UK 3 Department of Environment and Conservation, Species and Communities Branch, Locked Bag 104 Bentley Delivery Centre WA 6893, Australia 4 New York Botanic Garden, 112 Alpine Terrace, Hilldale, NJ 00642, USA 5 School of Life Sciences, University of Sussex, Falmer, Brighton, Sussex, BN1 9QG, UK 6 IUCN/SSC Orchid Specialist Group Secretariat, 36 Broad Street, Lyme Regis, Dorset, DT7 3QF, UK 7 University of California, Ecology and Evolutionary Biology, Irvine, CA 92697, USA 8 Massey University, Allan Wilson Center for Molecular Ecology and Evolution 9 Smithsonian Institution, Smithsonian Environmental Research Center, Box 28, Edgewater, MD 21037, USA 10 Author for correspondence: [email protected] RESUMEN. La distribución y densidad de los individuos dentro de las poblaciones de plantas pueden afectar el éxito reproductivo de sus integrantes. Luego de describir la filogenia de las orquideas del grupo de las Caladeniideas y su biología reproductiva, evaluamos el efecto de la densidad en el éxito reproductivo de la orquídea terrestre Elythranthera brunonis, endémica de Australia del Oeste. El éxito reproductivo de esta orquídea, medido como la deposición y remoción de polinios, fue evaluado. Se consideró como baja densi- dad aquellos individuos en los cuales se observó solamente una planta con flor en un radio de 2.5 m alrede- dor de esta planta focal y como alta densidad aquellas con una planta o más en un radio de 2.5 m alrededor de la planta focal. El éxito reproductivo de las plantas focales no fue afectado por la densidad de individuos en ninguna de las 6 poblaciones estudiadas. Sin embargo, cuando se evaluó la suma de las poblaciones en un conjunto, se observó que las plantas focales en “grupos” de mayor densidad tienen una mayor probabilidad de recibir polen. El número de flores por inflorescencia no afectó el éxito reproductivo de los individuos. Al contrario, el numero de flores total en un area de 2.5 m tenía un mayor éxito reproductivo en el componente de polinios removidos y depositados. Introduction Calopogon tuberosus (Firmage and Cole 1988), greatest at the highest inflorescence densities in Patterns of spatial distribution relative to con- Anacamptis (formerly Orchis) morio (Jersáková et al. specifics can affect the reproductive success of indi- 2002), and no relationship was detected between vidual plants in a population if pollinators respond to inflorescence density and fruit production in floral display. Floral display can be perceived at one Brassavola nodosa (Schemske 1980), Leporella fim- or more spatial scales by pollinators: the individual briata (Peakall 1989), Orchis purpurea (Jacquemyn flowers, the number of open flowers on an inflores- et al. 2002) or Neottia (formerly Listera) cordata cence, the number of inflorescences on a plant, the (Meléndez-Ackerman & Ackerman 2001). number of plants in a definable cluster or in a defin- able population. The relationship between reproduc- Data on the relationship between number of flow- tive success and floral display has been studied in rel- ers in an inflorescence and fruit set in orchids, while atively few orchid species and no consistent pattern scarce, are also inconsistent. In Lepanthes wendlandii has yet emerged. For example, fruit production was (Calvo 1990), Calopogon tuberosus (Firmage & Cole greatest at intermediate inflorescence densities in 1988), Ionopsis utricularioides (Montalvo & RD 230 3 IOCC PROCEEDINGS Ackerman 1987), Orchis purpurea (Jacquemyn et al. clades that together constitute the re-circumscribed 2002) and Aspasia principissa (Zimmerman & Aide tribe Diurideae s.s. Recent morphological taxonomic 1989), inflorescences bearing more flowers had a studies have progressively disaggregated the excep- higher probability of setting fruit. In contrast, there tionally heterogeneous genus Caladenia s.l., so that was no effect of flower number per inflorescence on the “core Caladeniinae” now encompasses ten mono- fruit set in Psychilis krugii (Ackerman 1989), phyletic genera, most of them containing few species Epidendrum exasperatum (Calvo 1990) or Neotinea (cf. Jones 1988, Hoffman & Brown 1998, Hopper & (formerly Orchis) ustulata (Tali 1996). Inflorescence Brown 2001b). Four genera successively branch from size may also affect male and female reproductive the base of the clade Caladeniinae. Adenochilus (2 success. In Epipactis helleborine, Piper and Waite species, Eastern Australian/New Zealand) is succeed- (1988) showed that the percentage of pollinaria ed by Eriochilus (8 species, mostly Western exported and imported increased in a parallel fashion Australian), then Leptoceras (1 species, Western and as inflorescence size increased, but the intercepts of Eastern Australian), then Praecoxanthus (1 species, the relationships were significantly different. Western Australian). A dichotomy then separates Pollinaria export was significantly greater than polli- Caladenia s.s. (an estimated 243 mainly Australian naria import at a given inflorescence size. species and 19 named hybrids in 6 subgenera) from a In this study we investigated two hypotheses relat- five-genus clade consisting of Cyanicula (10 species, ed to reproductive success in the deceit-pollinated both Western and Eastern Australian), Pheladenia (1 Purple Enamel-orchid, Elythranthera brunonis species, both Western and Eastern Australian), (Endl.) A.S. George, a terrestrial species endemic to Ericksonella (1 species, Western Australian), and Western Australia. The first hypothesis was that the then the generic pairing of Glossodia (2 species, reproductive success as measured from pollinaria Eastern Australian) and Elythranthera (2 species, deposition and removal of individual plants is inde- Western Australian) (Hopper and Brown 2004). pendent of the local density of conspecific plants. As Members of the “core Caladeniinae” have a recog- in neighborhood models of competition between nizable morphological “gestalt”. The small under- plants (Pacala & Silander 1985, Jacquemyn et al. ground tuber generates a single, fleshy leaf at or near 2002), if resources – in this case pollinators – are lim- the base of the slender stem, which in most cases is ited, we would expect reproductive success to be strongly hirsute and bears few flowers. The flowers lower in a higher density neighborhood if plants are are large relative to most other terrestrial orchids. In deceit-pollinated and the animal vector(s) have the many species, the three sepals and two lateral petals capacity to learn rapidly from their mistakes. The are large, rhombic in outline, spreading and brightly null hypothesis would be that more flowering plants colored, suggesting that they are primary visual per unit area could attract more pollinators, resulting attractants for pollinating insects. Deviations from in greater reproductive success per individual in this plesiomorphic condition occur in (a) the near- denser populations. The second hypothesis was that basal Eriochilus and Leptoceras, where the dorsal both pollen removal (an index of male function) and sepal and lateral petals are substantially reduced rela- pollen deposition (an index of female function) would tive to the lateral sepals, and (b) the highly derived be positively related to inflorescence size. In addition spider-orchids of Caladenia subgenus Calonema, to presenting quantitative tests of these two hypothe- subgenus Drakonorchis and subgenus Phlebochilus, ses, we review the controversial taxonomic, phyloge- which have strongly elongate sepals and lateral petals netic and distributional contexts of our chosen study (e.g. Hopper & Brown 2001b). In all ten genera, the species, Elythranthera brunonis, which have not pre- spurless labellum is well differentiated from the other viously been collated in the literature. five perianth segments by being more three-dimen- Morphology and pollination biology sional and much smaller, often possessing a fimbriate margin and/or adaxial calli. Together with the unusu- PHYLOGENETIC CONTEXT OF POLLINATION. ally elongate gynostemium, the labellum forms a A molecular phylogenetic analysis combining the visual and tactile focus for pollinators. The large plastid regions matK and trnL–F (Kores et al. 2001, gynostemium bears the relatively small, paired Hopper & Brown 2004) nested Elythranthera well acrotenic pollinaria that are characteristic of the within the “core Caladeniinae”, one of three major diurids (e.g. Dressler 1993, Pridgeon et al. 2001). LANKESTERIANA 7(1-2), marzo 2007. © Universidad de Costa Rica, 2007. TREMBLAY et al. - Density effect on reproductive success 231 Focusing on the Cyanicula–Glossodia–Elythran- morphologies. The labellum bears two prominent thera clade, largely unpublished molecular phylogenet- calli and is smaller than the over-arching gynostemi- ic data for the nrDNA internal transcribed spacer region um, which superficially resembles an additional peri- demonstrate substantial divergence between the three anth segment due to its exceptionally well-developed genera