You are here: Home > Activities > Meetings > 2002 > abstracts > Tuesday >
Society for Conservation Biology: 2002 Annual Meeting

Abstracts

< Go Back

Society for Conservation Biology: 2002 Annual Meeting

Society for Conservation Biology 16th Annual Meeting July 14-July 19 2002
co-hosted by DICE and the British Ecological Society


Abstracts for Population Viability Analysis
Session One

Tuesday 16th July, 13.30 - 15.00, Grimond Lecture Theatre 2

Chair: Yosihiro Natuhara




(BLOCK CAPITALS indicate the presenting author)


13.30 - 13.45
OSUNKOYA, OLUSEGUN. Biology Department, Universiti Brunei Darussalam,
Bandar Seri Begawan, Brunei, SE Asia, <osunkoya@fos.ubd.edu.bn>.

TWO-SEX POPULATION PROJECTION OF THE ENDEMIC RAINFOREST SHRUB, GARDENIA ACTINOCARPA (RUBIACEAE)

Gardenia actinocarpa (Rubiaceae), an endemic and dioecious shrub-small tree of the lowland rainforest of Cape Tribulation, Australia, is evaluated for long term population persistence using five-year demographic data from three permanent plots of the species. Two-sex, size-specific Lefkovitch matrices were constructed to evaluate the species’ vital rates and extinction thresholds. One site shows signs of significant population growth (annual l= 1.056), while the remaining two exhibit ls close to one (l= 1.0102 and 1.007). Overall, l seems appreciably > 1 (l = 1.0281) indicating that G. actinocarpa will increase in population size with time, though male plants were projected to grow faster in number than female plants. Elasticity analyses indicate that the largest size class (> 22 cm diameter) made the greatest contribution to population growth (28%), especially the male plants (23%). Also l was equally sensitive to survival/statis (44%) and growth (43%) and least sensitive to fecundity (12%). A 300-year stochastic simulation of population growth gave 0.505 probability of quasi-extinction to 10% of its initial size. Sensitivity analyses show that for population persistence of G. actinocarpa, efforts should concentrate on increasing seed production coupled with enhancing establishment of individuals in the seedling and juvenile phases.


13.45 - 14.00
COLAS, BRUNO, Hélène Fréville, Miquel Riba, Agnès Mignot, Eric Imbert, Isabelle Olivieri, and Jean Clobert. Laboratoire d'Ecologie, CC 237, Université de Paris 6, 7 quai Saint-Bernard, F-75252 Paris cedex 05, France bcolas@snv.jussieu.fr (BC and JC), Institut des Sciences de l'Evolution, CC 065, Université de Montpellier 2, Place Eugène Bataillon, F-34095 Montpellier cedex 05, France (HF, AM, EI, and IO), CREAF-UAB, Facultat de Ciències, Universitat Autònoma de Barcelona, Bellaterra 08193, Barcelona, Spain (MR)

SPECIES VIABILITY ANALYSIS OF A CLIFF-DWELLING, NARROW-ENDEMIC PLANT

The cliff-dwelling, monocarpic perennial, allogamous Centaurea corymbosa consist of only 500 flowering individuals per year on average in 6 populations in a 3-km_ area. Previous studies have shown that gene flow is very restricted among populations, but quite extensive within populations due to pollen dispersal. Many suitable sites (cliffs) available near the extant populations remain empty because of the low colonisation ability of the species. We studied the viability of the six extant populations using matrix analyses. Demographic and ecological data collected during seven years allowed to model population dynamics including environmental and demographic stochasticities, negative density-dependance on survival rates, positive density dependance on fecundities (Allee effect), and dispersal among patches within populations. It appeared that, although demographic data are based on almost 10% of the individuals of the species, precise predictions on the population extinction can not be made, especially because of high environmental stochasticity. This study revealed the importance of density and migration between patches on population dynamics. It underlined the influence on the results of how individuals were sampled for demographic survey and the need to sample empty quadrats for the inclusion of patch colonization within populations into the demogaphic models.



14.00 - 14.15
NATUHARA, YOSIHIRO, Fumi Miyoshi and Yukihiro Morimoto 1)
Graduate School of Agriculture and Biological Sciences, Osaka Prefecture Uiversity
1-1 Gakuen-cho, Sakai 599-8531, Japan (natuhara@envi.osakafu-u.ac.jp)
1) Present address: Kyoto University, Graduate School of Agriculture

CONSERVATION SCENARIO FOR A META-POPULATION OF THE CLOUDED SALAMANDER, HYNOBIUS NEBULOSUS USING MPVA.

The clouded salamander Hynobius nebulousus is listed as endangered in Japan. Main habitat of this species is in a small valleys in hill country, that is vulnerable to urban development. Some scenarios were compared to evaluate the effects of land management on the extinction risk of the clouded salamander using meta-population vulnerability analysis, MPVA. The study site was 200 ha hill in which strips of paddy field had been cultivated on small valleys, and most of those were abandoned 25 year ago. The results of computer simulation suggested that a small reserve could not compensate land development of whole area, the extinction risk increased even if the development was limited to one third of the whole area, isolated habitat patches would not be recolonized even if the land was not developed, and abandonment of cultivated paddy field raised the extinction risk more than partial development was done. By the simulation, we recommend connecting habitas by digging small pools to decrease the extinction risk.



14.15 - 14.30
O’BRIEN, SUSAN.H., Tim.N. Coulson. Department of Zoology, Cambridge University, Downing Street, Cambridge, CB2 3EJ, UK & Institute of Zoology, Zoological Society of London, Regents Park, London NW1 4RY (sho21@cam.ac.uk). Department of Zoology, Cambridge University, Downing Street, Cambridge, CB2 3EJ, UK (TNC).

EXPLOITATION OF THE MALAGASY RADIATED TORTOISE: IS EXTINCTION INEVITABLE?

The radiated tortoise (Geochelone radiata), endemic to southern Madagascar, is vulnerable to extinction primarily due to overexploitation. Many tortoises are illegally harvested for meat and pets, for consumption within Madagascar and overseas. Yet the impact of current offtake rates has not been assessed and the potential for a sustainable harvest has never been investigated. We used population and harvest models to evaluate the influence of density-dependent and -independent processes, on probability of extinction for this species, under current offtake rates. The size and section of the tortoise population that constituted a theoretically sustainable offtake under a range of conditions, was identified. Models were parameterised with field data from Madagascar and stud book data. All models predicted a harvest of small juveniles to be more sustainable than harvesting adults. The density-independent model predicted harvesting of juveniles to have little impact over many years but to be catastrophic in certain years. Some radiated tortoise populations may already be unviable, even without further harvesting. Finally, the potential to instigate a quota harvest system in the socio-economic and political context of southern Madagascar was considered, and found to be unviable. Under current conditions extinction for the radiated tortoise would seem to be inevitable.



14.30 - 14.45
TRINDER, MARK, Matthew R. Evans and Tim G. Benton. Institute of Biological Sciences, University of Stirling, Stirling, FK8 1HN, UK, <m.n.trinder@stir.ac.uk> (MNT, MRE, TGB).

THE IMPORTANCE OF DENSITY-DEPENDENCE AND STOCHASTICITY IN PVA: USING WRENS AS A MODEL SYSTEM

Population modelling is a valuable tool for rare species conservation. Analysis of model outputs can greatly assist in the identification of the most vulnerable parts of a species' life cycle, and improve targeting of resources. However models which lack important biological details, particularly density dependence and stochasticity, may be overly simplistic. Demographic data for a small population of wrens, Troglodytes troglodytes, has been used to develop a range of matrix models which incorporate co-varying stochastic vital rates and density dependent breeding and survival. The models will be presented, illustrating the consequences of including density dependence and stochasticity for the population. The implications of these results for the conservation of rare and endangered species will be discussed and practical solutions for managers and modellers will be suggested.



14.45 - 15.00
CARROLL, CARLOS, Michael K. Phillips, Nathan H. Schumaker, and Douglas W. Smith. Klamath Center for Conservation Research, Orleans, CA 95556, USA, <carlos@sisqtel.net> (CC), Turner Endangered Species Fund, Bozeman, MT 59718, USA (MKP), US Environmental Protection Agency, Corvallis, OR 97333, USA (NHS), Yellowstone Center For Resources, Mammoth, WY 82190, USA (DWS).

IMPACTS OF LANDSCAPE CHANGE ON WOLF RESTORATION SUCCESS: PLANNING A REINTRODUCTION PROGRAM USING DYNAMIC SPATIAL MODELS

Mammalian carnivores are increasingly the focus of reintroduction attempts in areas from which they have been extirpated by historic persecution. We evaluated the potential success of a proposed wolf reintroduction to the southern Rocky Mountain region (USA) using a spatially-explicit population model that predicted wolf distribution and viability under current conditions and under two contrasting predictions of future landscape change. Our results suggest that the southern Rocky Mountains could support reintroduced wolves under current conditions but that development trends over 25 years may result in the loss of one of four potential regional subpopulations and increased isolation of the remaining areas. While much of the wolf population is likely to occur outside core protected areas, these areas remain the key to persistence of subpopulations. Our results suggest that social carnivores such the wolf may be more vulnerable to environmental stochasticity and landscape fragmentation than their vagility and fecundity would suggest. Techniques that integrate population viability analysis with regional-scale conservation planning and reserve design may help increase the success rates of reintroduction programs for area and connectivity-dependent species.