Population dynamics of Caladenia: Bayesian estimates of transition and extinction probabilities
Raymond L. Tremblay A I , Maria-Eglée Perez B , Matthew Larcombe C , Andrew Brown D , Joe Quarmby E , Doug Bickerton F , Garry French G and Andrew Bould HA Department of Biology, 100 Carretera 908, University of Puerto Rico, Humacao Campus, Humacao, Puerto Rico 00792, USA and Crest-Catec, Center for Applied Tropical Ecology and Conservation, PO Box 23341, University of Puerto Rico, San Juan, Puerto Rico 00931-3341, USA.
B Department of Mathematics, University of Puerto Rico, Rio Piedras campus, San Juan, Puerto Rico 00931-3355, USA and Crest-Catec, Center for Applied Tropical Ecology and Conservation, PO Box 23341, University of Puerto Rico, San Juan, Puerto Rico 00931-3341, USA.
C Threatened Species Section, Department of Primary Industries and Water, GPO Box 44, Hobart, Tas. 7001, Australia.
D Species and Communities Branch, Department of Environment and Conservation, Locked Bag 104, Bentley Delivery Centre, WA 6983, Australia.
E Conservation Programs Unit, Adelaide Region, Department for Environment and Heritage, GPO Box 1047, Adelaide, SA 5001, Australia.
F Threatened Species Unit, Conservation Policy and Programs, Department for Environment and Heritage, GPO Box 1047, Adelaide, SA 5001, Australia.
G Parks Victoria, Northern Melbourne District, PO Box 568, Templestowe, Vic. 3106, Australia.
H 109 Western Boulevard, Raymond Island, Vic. 6880, Australia.
I Corresponding author. Email: raymond@hpcf.upr.edu
Australian Journal of Botany 57(4) 351-360 https://doi.org/10.1071/BT08167
Submitted: 10 September 2008 Accepted: 15 June 2009 Published: 29 July 2009
Abstract
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.
Acknowledgements
M. L. is funded by the Tasmanian Cross Regional NRM project to Implement Threatened Species Recovery Plans. J. Q. and D. B. acknowledge their appreciation to Deb Way, Kate Greenhill, Irene Thomas, Heather Bryant, David Kilpin, Cathy & Malcolm Houston, Peter McCauley, Rick Davies, Pam O’Malley, Rod Hawke, Ken & Barb Bayley, and Thelma & Phil Bridle for their help, and to the Adelaide & Mount Lofty Ranges NRM Board, Northern & Yorke NRM Board and Natural Heritage Trust for funding.
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