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


Abstracts for Spatial Ecology and Conservation
Session Three

Tuesday 16th July, 10.15 - 12.15, Grimond Lecture Theatre 3

Chair: Oliver Berry



Conference Home Page | Session timetable


(BLOCK CAPITALS indicate the presenting author)

10.15 - 10.30
PARK, KIRSTY J., Justin M. J. Travis and John Harwood. Centre for Conservation Science, Department of Biological Sciences, University of Stirling, Stirling FK9 4LA, UK, <k.j.park@stir.ac.uk> (KJP), Centre for Conservation Science, School of Mathematics and Statistics, Mathematical Institute, University of St Andrews, North Haugh, St Andrews, Fife KY16 9SS, UK (JMJT), Centre for Conservation Science, NERC Sea Mammal Research Unit, Gatty Marine Laboratory, University of St Andrews, St Andrews, Fife KY16 8LB, UK (JH).

THE CONTROL OF SOURCE-SINK POPULATIONS

Spatial variability in habitat quality is characteristic of natural ecological systems. Differences in habitat quality may lead to inequality in the demography of populations occupying these different habitats, so that some populations may exhibit a net demographic surplus (sources) and some, a net demographic deficit (sinks). Sinks persist only through the dispersal of individuals from source habitats. There is an increasing amount of effort being devoted to modelling populations organised in this way. Here we use a simple source-sink model to address the following question: if a population of a pest species is source-sink in nature, what is the best way of dividing up a limited amount of resources for its control? Our results indicate that it is not always best to allocate all the resources to control of the source population. The most efficient control measure is determined by the relative strengths of source and sink, and crucially the extent of dispersal that occurs between them. We discuss some likely implications of our results for specific conservation issues.

10.30 - 10.45
KIRCHNER, FLORIAN, Jean-Baptiste Ferdy, Christophe Andalo, Bruno Colas, and Jacques Moret. Laboratoire d’Ecologie, UMR 7625, Case 237, Université de Paris VI, 7 Quai Saint Bernard, F-75252 Paris cedex 05, France, <florian.kirchner@voila.fr> (FK, BC), Laboratoire Génome, Populations, Interactions, UMR 5000, Bât. 13, Université de Montpellier II, F-34095 Montpellier cedex 5, France (JBF), Laboratoire d’Ecologie Terrestre, UMR 5552, Université Paul Sabatier, 118 route de Narbonne, Bât. IVR3, F-31062 Toulouse cedex 4, France (CA), Conservatoire Botanique National du Bassin Parisien, Muséum National d’Histoire Naturelle, 61 rue Buffon, F-75005 Paris, France (JM).

ROLE OF CORRIDORS IN PLANT DISPERSAL: AN EXAMPLE WITH THE ENDANGERED RANUNCULUS NODIFLORUS L.

The proposition that migration of organisms between habitat patches could be enhanced by corridors has been much discussed in conservation biology. But the few experimental studies supporting the usefulness of corridors have all concerned animal species. We investigated the role of corridors on seed dispersal, studying population genetic and demographic structure in metapopulations of the rare, pond-dwelling, autogamous plant species Ranunculus nodiflorus in the Fontainebleau Forest (France). Differentiation on isozyme markers was strong between local populations (ponds) within metapopulations (sites) and moderate between metapopulations. Partial Mantel tests revealed that pond connection through temporarily flooded natural corridors had a strong negative effect on genetic differentiation between local populations, and that a pond was more likely colonized when connected by corridors (facilitating seed migration) to other occupied ponds. Thus, corridors are probably a key factor of landscape structure for metapopulation dynamics in R. nodiflorus. From a conservation perspective, our results suggest that corridors could increase the chance of persistence of plant species living in fragmented habitats in promoting seed dispersal between habitat patches.



10.45 - 11.00
GILLIES, CAMERON SCOTT and Colleen Cassady St. Clair. Department of Biological Sciences, University of Alberta, Edmonton, Alberta T6G 2E9, Canada, <cgillies@ualberta.ca>.

TESTING CORRIDOR EFFICACY WITH FOREST BIRDS IN THE TROPICAL DRY FORESTS OF COSTA RICA

Tropical forest destruction and fragmentation may be disrupting the movement of forest birds. Corridors have been widely advocated as a way of mitigating these impacts in the tropics and elsewhere. By translocating territorial individuals of two species of forest birds one to two kilometres along riparian corridors, along fencerows, and across open fields, and then closely following their return with radio-telemetry, I was able to test the efficacy of riparian corridors and fencerows in facilitating movement. Birds returned faster and were more likely to return in riparian corridors than fencerows but the suitability of fencerows for facilitating movement appears to differ between species. rufous-naped wrens, Campylorhynchus rufinucha, which are less dependent on forests, used fencerows in their returns and the corresponding times to return were intermediate between their return in riparian corridor and open field relocations. By contrast, the barred antshrikes, Thamnophilus doliatus, avoided using fencerows for their returns in favour of longer routes in forest, which also had fewer gaps in forest cover. These results suggest that to facilitate the movement of the most forest-dependent species, fencerows may not be sufficient and large forested corridors may be required.




11.00 - 11.15
CONREY, REESA YALE and L. Scott Mills. Wildlife Biology Program, School of Forestry, University of Montana, Missoula, Montana 59812, USA, <reesa@wru.umt.edu>.

HIGHWAYS AS AGENTS OF POPULATION FRAGMENTATION IN SMALL MAMMALS

Small mammal populations separated by highways may be partially or completely isolated from one another due to low dispersal capabilities, low probability of surviving highway crossing attempts, and/or avoidance of areas adjacent to highways. Our objective is to determine how movement and gene flow are affected by 2- and 4-lane highways for several small mammals in forested areas of western Montana. We used mark-recapture techniques to compare movement adjacent to highways to movement across highways for southern red-backed voles (Clethrionomys gapperi), deer mice (Peromyscus maniculatus), yellow pine chipmunks (Tamias amoenus), and red-tailed chipmunks (Tamias rufocaudus). More individuals moved adjacent to highways than across highways, and more crossed 2-lane than 4-lane highways. Effects varied for different species, with forest-associated species (red-backed voles and chipmunks) more inhibited by highways than habitat generalists (deer mice). In fact, deer mice were more abundant near highways than in the forest interior, and in some cases crossed highways more than they moved parallel to them. Ongoing analyses using the assignment test and equilibrial genetic measures will provide further insight into movement rates and gene flow for red-backed voles, deer mice, and vagrant shrews (Sorex vagrans)



11.15 - 11.30
BERRY, OLIVER. Institute of Molecular BioSciences, Massey University, Palmerston North, New Zealand, <ofberry@massey.ac.nz>.

GRAND SKINKS SHOW LIMITED DISPERSAL IN AN AGRICULTURAL LANDSCAPE: MICROSATELLITE DNA EVIDENCE

Is the matrix or non-habitat surrounding habitat islands in fragmented landscapes uniformly inhospitable? Small populations of the grand skink, Oligosoma grande, an endangered lizard, inhabit rock ‘islands’ 50-100 metres apart amongst a matrix of indigenous tussock grassland or (increasingly) modified pasture in southern New Zealand. Skinks are less abundant on rock islands in pasture-dominated than grassland-dominated sites, possibly because pasture inhibits dispersal and island recolonisation. This natural experiment enables a test of the relationship between matrix type and dispersal, and specifically, whether pasture limits grand skink dispersal. Data from nine microsatellite loci revealed the skinks to be sedentary. Skinks inhabiting neighbouring rock outcrops were genetically distinct (Fst 0.035–0.141 over 50-350 metres), and significant genetic isolation by distance exists over short distances (<350 metres). These results support existing field data. Genetic subdivision was greatest within the pasture matrix. By implication, dispersal between rock islands separated by pasture is less common. Current work focuses on generating empirical estimates of dispersal using individual-based assignment analyses.



11.30 - 11.45
NOON, BARRY, Roland Lamberson, and Matthew Farnsworth. Department of Fishery and Wildlife Biology, Colorado State University, Fort Collins, CO 80523, USA, <brnoon@cnr.colostate.edu> (BN), Department of Mathematics, Humboldt State University, Arcata, CA 95521, USA <rhl1@axe.humboldt.edu> (RL), and Natural Resource Ecology Laboratory, Colorado State University, Fort Collins, CO, USA, <mattf@cnr.colostate.edu> (MF).

AN INCIDENCE FUNCTION MODEL OF IMPERILED WILLOW FLYCATCHER METAPOPULATIONS IN THE SOUTHWESTERN U.S.

We developed a population viability analysis for the southwestern willow flycatcher, a desert riparian bird species listed as threatened under the U. S. Endangered Species Act. Our analysis was based on Hanski’s incidence function (IF) model (1994. J. Animal Ecology 63:151-162). The IF model tracks extinction and recolonisation of patches within a metapopulation as a function of patch number, size, distribution and connectivity. Patches were viewed as nodes of a graph with multiple patterns of connectivity reflecting different movement pathways. The relationship between the distribution of flycatchers and riparian habitat indicated that movement was constrained to a given watershed with between-watershed movements rare. Status of the six distinct metapopulations varied geographically. The species is in jeopardy where occupied sites are small and widely dispersed, but stable in areas where there are a few large patches that are highly connected. Based on their colonisation potential, the contribution of individual patches to overall population dynamics for each metapopulation was assessed. These analyses allowed us to rank the importance of individual patches and to propose a strategy of acquisition or restoration of specific patches to enhance flycatcher persistence. Protection of these sites forms the basis of a comprehensive conservation strategy for the species.



11.45 - 12.00
GRIFFIN, PAUL C., and L. Scott Mills. Wildlife Biology Program, University
of Montana, Missoula, Montana 59812, USA.

FOREST VEGETATION STRUCTURE INFLUENCES SNOWSHOE HARE DEMOGRAPHY

We report on demographic studies of snowshoe hares, Lepus americanus, in managed forests of western Montana, USA. Snowshoe hares are central in the diet of the Canada lynx, Lynx canadensis, a U.S. Federally threatened species in states outside Alaska. Snowshoe hares may or may not cycle at this latitude, and forest fragmentation has been proposed to dampen any cycles that may exist. Our methods include mark-recapture trapping for estimation of density, ultrasonography for estimation of birth rates, and extensive radio tracking for estimation of survival rates and movement. Snowshoe hare densities vary across forest stand types and years, and are reduced by pre-commercial thinning, a widespread practice in industrial forestry. Highest densities are found in summer in stands with high sapling density. Survival rates are high in the summer and winter across all stand types, but low in the fall and spring in habitats with open canopies. We find little difference in birth rates according to stand type within small areas of ~5 km2, but do find regional differences in birth rates. Differences in survival rate alone are enough to cause decline in habitats with open canopies. Movement between habitats likely is sustaining populations in such habitats.



12.00 - 12.15
BAR-DAVID, SHIRLI, David Saltz and Tamar Dayan. Department of Zoology, Tel Aviv University, Israel 69978, <shirlib@post.tau.ac.il> (SB; TD), Mitrani Department of Desert Ecology, Ben Gurion University, Sde-Boqer, Israel 84990 (DS).

MODELING POPULATION GROWTH IN TIME AND SPACE OF REINTRODUCED PERSIAN FALLOW DEER IN ISRAEL

Securing natural habitats is essential for the long-term establishment and viability of reintroduced populations. Consequently, the ability to project future range expansion is critical in reintroduction programs. We evaluated, using a spatially realistic model, whether population expansion of reintroduced Persian fallow deer, Dama mesopotamica, can be projected based on data obtained during the first 2.5 years after initial release and by comparing model projections with reality five years after initial release. Spatial parameters were defined by characterising home-ranges of 17 radio-collared females reintroduced to northern Israel starting 1996. Significant factors affecting home-range establishment were: occurrence of Mediterranean woodland (53%+11 cover); occurrence of moderate terrain (average topographical slope was 12.9+3.5); presence of conspecifics (65% of home-ranges overlapped with one to five others); and roads. Demographic parameters were derived from captive herds with adjustments based on field data. We constructed the model using Matlab and GIS. Over the five year period the model predicted the main activity centres found in the wild but only half the area occupied by the deer. Identifying potential activity centres is critical for securing the population's future radiation. The model can serve as a basis for sustainable development relying on the projected radiation of this umbrella species.

The SCB2002 pages are maintained by Christine Eagle
email: C.M.Eagle@ukc.ac.uk
Conference email: scb2002@ukc.ac.uk
Last updated: 30.06.02