Population dynamics (Conservation Modelling)
New Zealand Room 2 Friday, December 9th 2011
10:30 Species Ability to Forestall Extinction (SAFE) index for IUCN Red Listed species Bradshaw, CJA*, The University of Adelaide
; Clements, GR, James Cook University; Laurance, WF, James Cook University; Brook, BW, The University of Adelaide
The IUCN Red List is the gold standard measurement of relative species threat, but its categories can be ambiguous, subjective, arbitrary, and do not necessarily convey the conservation status of species in relation to a minimum viable population target. While controversial, portraying a species‚Äô population estimate as a function of its taxon- or species-specific minimum viable population size indicates the ‚Äėdistance‚Äô of a species from extinction while implicitly incorporating the element of population viability. We applied the Species Ability to Forestall Extinction (SAFE) index to thousands of Red-Listed mammals, birds, amphibians and reptiles for which abundance estimates were available to determine the congruence between Red List categories and relative extinction risk. We show that many lower-priority species (e.g., Vulnerable) currently have much higher extinction risks than implied by their Red List status based on their inherent extinction risk as implied by their SAFE index.
10:45 Threat diagnostics: inferring causation from vertebrate population declines Martina Di Fonzo*, Imperial College London and Institute of Zoology, Zoological Society of London
; Ben Collen, Institute of Zoology, Zoological Society of London; Georgina Mace, Imperial College London
Accurately diagnosing the causes of population decline is paramount to the successful conservation management of vertebrate species. I explore the possibility of identifying the cause of mammal population declines based solely on changes in times-series convexity, using a dataset of 279 populations. First, I use the life-history and population-trend characteristics of species within this dataset to develop a technique which identifies the onset of pressure based on switches in population growth rate. Secondly, I test a method for diagnosing the cause of population decline according to the convexity of its decline-curve and identify broad decline-curve categories that reflect the dynamics of different simulated exploitation regimes. I demonstrate that the onset of constant, proportional harvesting is easier to identify than fixed-quota harvesting and that constant, proportional harvesting and increasing, fixed-quota harvesting are the only pressure-types that result in consistent decline-curve shapes. These pressures produce declines that best-fit concave, exponential and quadratic, convex functions, respectively. I selected time-series from my dataset upon which to test these methods and show that declines can be classified according to threat-type. This study also identifies the presence of rapid, convex declines as a method for prioritising conservation action. I suggest that ‚Äúdecline concavity‚ÄĚ could be used to classify threatened species under IUCN criteria.
11:00 The use of population viability analysis to inform small-scale monitoring projects Pickett, EJ*, University of Newcastle
; Stockwell, MP, University of Newcastle; Pollard, CJ, University of Newcastle; Garnham, JI, University of Newcastle; Clulow, J, University of Newcastle; Mahony, MJ, University of Newcastle
Small-scale population monitoring programs are restricted in their capacity to conduct rigorous demographic studies, and must usually focus upon certain aspects of a population‚Äôs ecology. We suggest that it is the role of larger-scale projects which can afford the use of population viability analysis to determine the most important aspects for population viability, and then inform project managers for the most efficient and focused methods to evaluate their target population. We have undertaken this process for the green and golden bell frog (Litoria aurea) at Sydney Olympic Park. Population viability analysis was undertaken within the Brickpit population, and female survival to maturity was found to be the most important demographic factor. Using this information, we designed a monitoring regime for small-scale projects which focused upon the ratio of mature females to immature females. This was then validated on three populations of L. aurea, where it was found that a difference in this maturity ratio was linked to an increase in growth rate of individuals between populations. We recommend this extra step of designing small-scale monitoring regimes is used for any species where population viability analysis has been conducted on one of many populations to better enhance the conservation prospects of the species throughout its range.
11:15 Designing sampling strategies for conservation genetics studies: a simulation tool for conservation managers Hoban, Sean*, Laboratoire d' Ecologie Alpine, Universite Joseph Fourier
; Gaggiotti, Oscar, Laboratoire d' Ecologie Alpine, Universite Joseph Fourier; Bertorelle, Giorgio, Department of Biology and Evolution, University of Ferrara
Genetic data for threatened species is commonly incorporated into conservation activities (e.g., choosing source populations for stocking, detecting poaching, assessing admixture, or identifying populations of high conservation value). A major issue in planning a conservation genetic study is the number of genetic markers, samples, and populations to incorporate. Unfortunately, many studies are undertaken without clear knowledge of the type and statistical power of the data they can expect, often leading to post-hoc and ambiguous interpretation of non-significant results. There is currently no tool available for estimating power of sampling under a variety of complex demographic and management scenarios. We present a prototype of a web-based, highly user-friendly software package developed to fill this gap. The simulation-based tool includes several modules (e.g., bottlenecks, connectivity, assignment) that are customizable for species-specific genetic and demographic parameters. For each module, using case studies, we discuss the balance between markers and samples in achieving a desired power threshold. Our tool can be used by conservation managers without specific expertise in genetics. Further, its simple and flexible architecture allows incorporation of future conservation genetic methods. This package is a deliverable of ConGRESS (www.congressgenetics.eu), a FP7 EU project to produce tools to incorporate genetic biodiversity into policy and management activities.
11:30 THE AFRICAN LION (Panthera leo leo): A CONTINENT-WIDE SPECIES DISTRIBUTION STUDY AND POPULATION ANALYSIS Riggio, Jason S.*, Big Cats Initiative, National Geographic Society; Duke University
; Jacobson, Andrew, Big Cats Initiative, National Geographic Society; Duke University; Pimm, Stuart, Duke University; Dollar, Luke, Big Cats Initiative, National Geographic Society; Duke University; Pfeiffer University
Human population growth and land conversion across Africa makes the future of wide-ranging carnivores uncer-tain. For example, the African lion (Panthera leo leo) once ranged across the entire continent ‚Äď with the exception of the Sahara Desert and rainforests. It now lives in less than a quarter of its historic range. Recent research estimates a loss of nearly half of the lions in the past two decades. Some sources put their numbers as low as 20,000 individuals. Given these declines, conservation organizations propose to list the African lion as ‚Äúendangered‚ÄĚ under the U.S. Endangered Species Act and to upgrade the species‚Äô CITES protections from Appendix II to Appendix I. To establish the lion‚Äôs current conservation status, I analyzed the size, distribution, and potential connections of populations across its range in Africa. I compile the most current scientific literature, comparing sources to identify a current population estimate. I also use these sources to map known lion populations, potential habitat patches, and the connections between them. Finally, I assess the long-term viability of each lion population and determine which qualify as ‚Äúlion strongholds.‚ÄĚ The lion popu-lation assessment in this study has shown that over 30,000 lions remain in approximately 3,000,000 km2 of Africa. Lions are distributed across a total of 78 habitat patches in 27 countries. More than half of the remaining lions in Africa reside in 11 viable populations contained within protected areas that have stable or increasing lion population trends (lion strongholds). Therefore lions are not currently threatened with extinction and it is unlikely that the total population of free-ranging lions in Africa will drop below 20,000 individuals.
11:45 Analysis of transient population dynamics of the endangered Penstemon haydenii Brigitte Tenhumberg*, University of Nebraska Lincoln
; Richard Rebarber, University of Nebraska Lincoln; Kay Kottas, University of Nebraska Lincoln
In many organisms dispersal is restricted to specific life history stages, thus the stage distributions of founder populations are not stable and we expect significant transient deviations from long-term dynamics. The transient population growth rate following a dispersal event is a critical component for the establishment success because propagules typically arrive in new patches in small numbers and small populations inherently have a high extinction risk as a result of Allee effects or demographic stochasticity. The population growth rate after arrival determines how long populations remain in the state of ‚Äúdangerously low numbers‚ÄĚ. A high colonization success is especially important for organisms exploiting ephemeral resources, such as pioneer plant species. In this paper we use density dependent integral projection models on the endangered pioneer species, Penstemon haydenii to explore the role of transient dynamics in population establishment. We used Monte Carlo analysis and Partial Rank Correlation Coefficients to evaluate the relative importance of model parameters for transient and asymptotic dynamics. Our models predict large spatial variation in long and short term population dynamics. Furthermore, our models suggest that transient dynamics play a key role in colonization success. Transient dynamics can cause colonizing (seedling) populations to crash to very low numbers and it may take > 40 years to reach numbers that are close to the predicted asymptotic population size.
12:00 Growth rates of juvenile Broad-snouted caiman at Pirapitinga Ecological Station, Southeast Brazil. Passos, L. F*, Puc Minas
; Coutinho, M.E., RAN/ICMBio
The broad-snouted caiman (Caiman latirostris) is widely distributed in the Atlantic Forest and Cerrado biomes in Brazil. Few studies have dealt with the status and or dynamics of populations in the wild, and the lack of information imposes serious constraints to the development of broader conservation and management plans for the species. Since 2006, we are investigating the dynamics of a natural population of broad-snouted caimans in an artificial reservoir located in the upper S√£o Francisco river basin, southeast Brazil. The knowledge obtained by this study shall be applied to establish new conservation units in trough the S√£o Francisco River Basin. We conducted night surveys and all animals spoted were captured ,their cloacal, air and water temperature, SVL and body mass were also measured. All animals were marked and released at the site of capture. We also monitor the water level, temperature and precipitation trough the year. The data collect on field were analyzed trough multiple regressions .Through the data analysis we concluded that the growth rates are affects not only by the animal size, but also by different environmental variables in special with the reservoir water level. The environmental variables directly affect caimans¬ī growth making it relevant to monitor those conditions in order to complete understand the growth dynamics of this species.
12:15 Simple decision analyses for metapopulation viability of an endangered Australian amphibian Heard, GW*, School of Botany, University of Melbourne
; McCarthy, MA, School of Botany, University of Melbourne; Parris, KM, School of Botany, University of Melbourne; Scroggie, MP, Arthur Rylah Institute for Environmental Research, Victorian Department of Sustainability and Environment
Metapopulation models can provide clear direction to threatened species management, yet these tools have rarely been applied to real-world problems. Obstacles have included the abstract nature of some metapopulation models, the limited capacity of these models to incorporate parameter uncertainty, and the need for custom computer programs to apply them. In this study, we used freely-available software to develop a Bayesian metapopulation model for the endangered Growling Grass Frog, and coupled the model with multicriteria decision analyses to critique management options for this species. The model includes estimates of the effect of environmental variables on extinction and colonisation rates, and propagates uncertainty in these estimates through to predictions of metapopulation persistence under differing management scenarios. Multicriteria decision analyses integrate this uncertainty, using a simple outranking method to identify which scenario gives the highest chance of metapopulation persistence across the range of parameter estimates. We used the approach to identify optimal wetland creation schemes for Growling Grass Frogs around Melbourne, Victoria, Australia. Encouragingly, we were able to clearly discriminate between proposed options in several cases, providing important direction to managers. Given appropriate data, our approach represents a robust, intuitive and straightforward means of critiquing management options for metapopulations.