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Society for Conservation Biology: 2002 Annual Meeting

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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 Metapopulation Ecology

Monday 15th July, 13.30 - 15.00, Grimond Lecture Theatre 3

Chair: Richard Griffiths




(BLOCK CAPITALS indicate the presenting author)


13.30 - 13.45
OVASKAINEN, OTSO. Department of Zoology, University of Cambridge, Downing Street, Cambridge CB2 3EJ, UK, <otso. ovaskainen@helsinki.fi>.

METAPOPULATION VIABILITY ANALYSIS

Population viability analysis (PVA) has become a standard tool for assessing the viability of a closed population. In order to assess the persistence of an endangered species at a regional, national or global scale, it is necessary to complement PVA by considerations of processes that take place at a larger spatial scale and a longer temporal scale. Such considerations may be given the term metapopulation viability analysis (MVA). One of the most central tools in MVA is the concept of patch value, defined as the contribution of an individual habitat patch to metapopulation dynamics. We apply MVA to an endangered species of butterfly, illustrating how the biology of the species and regional level presence/absence data may be combined to assess the viability of the species and to compare possible management alternatives.

13.45 - 14.00
GAINES, KAREN H. Department of Biology, University of New Mexico at Albuquerque, New Mexico 87131, USA, <kgaines@unm.edu>.

IT'S NICE TO VISIT, BUT I WOULDN'T RAISE MY KIDS THERE: ODONATE DIVERSITY AND BREEDING ECOLOGY IN NEW MEXICO

The Bitter Lake National Wildlife Refuge in southeastern New Mexico is an unusual ecological complex of wetlands, salt flats, and dozens of water-filled sinkholes of varying sizes, geomorphologies, and water chemistries. Recent collections of over ninety species of adult dragonflies and damselflies suggest that the highest diversity of odonates in the state occurs in this small area, although the composition of the resident breeding population and the environmental factors contributing to this species diversity were unknown. To manage this unique resource, refuge personnel need to understand how species are distributed, what areas provide critical breeding habitat, and how odonate larvae interact with other aquatic organisms, including two rare species of small fish that occupy the same sinkhole habitats. Thousands of odonate exuviae (cast larval skins) and adults were collected at over thirty-five sinkholes in 2000 and 2001. Only one dragonfly species successfully bred in many of the sinkholes, while exuviae of several species observed as adults throughout the refuge were found at only a few sinkholes, suggesting limited breeding habitat availability for these species. Fewer than twenty species bred successfully in the sinkhole complex, indicating that additional sources of species diversity remain to be identified.



14.00 - 14.15
DAVIS, ROBERT. Department of Zoology, University of Western Australia, 35 Stirling Highway, Crawley, 6009, Western Australia, <radavis@cyllene.uwa.edu.au>.

IMPACTS OF HABITAT FRAGMENTATION AND SALINITY ON THE WEST AUSTRALIAN FROG HELEIOPORUS ALBOPUNCTATUS

Heleioporus albopunctatus is a widespread species with a range encompassing south-west Western Australia (WA). Main (1990) suggested that H. albopunctatus has declined or become extinct in parts of the WA wheatbelt due to increases in salinity. I investigated the metapopulation ecology and genetic structuring of populations of adults and larvae of this species in the WA wheatbelt. Forty five populations were monitored over a three year period. This species has terrestrial egg deposition in burrows. When burrows flood, eggs hatch into tadpoles. Of 45 populations, 12 (27%), recruited tadpoles from egg masses. From zero to six of these 12 populations recruited metamorphs over the three years. Thus only a small number of breeding sites regularly recruit, and only during years of good rainfall. Recruitment failure is linked to salinisation and reduced water-holding capacities of the mostly man-made breeding sites. Allozyme analysis indicates a significant degree of subdivision (Fst=0.082, p<0.01) for Wright’s Fst averaged across 22 populations and 4 loci. These data combined with population studies are consistent with habitat loss and salinity, genetic population subdivision and local extinction. The regional persistence of H. albopunctatus metapopulations is probably dependent on a core of successfully recruiting sites to produce dispersing individuals.



14.15 - 14.30
YOUNG, SUSAN L. and Richard A. Griffiths. Durrell Institute of Conservation and Ecology, University of Kent at Canterbury, Canterbury, Kent, CT2 7NS, UK, <sly1@ukc.ac.uk>.

IS COLONISATION OF EMPTY PATCHES A CHANCY BUSINESS? AN EMPIRICAL TEST USING AMPHIBIANS

Considerable debate exists concerning the role of stochastic versus deterministic factors in metapopulation dynamics. Because habitat patches are invariably heterogenous, it is difficult to determine whether extinction-colonisation patterns are due to inherent differences in patch quality or whether chance factors play a role. If chance factors are important in the foundation of a population, then differences between otherwise identical habitat patches in the numbers of colonisers may arise. On the other hand, if deterministic factors - such as patch quality - are important, colonisers would be expected to distribute themselves evenly between identical patches. We tested these ideas by monitoring the colonisation by amphibians of four identical and adjacent ponds installed in a field within a suburban landscape. The ponds were colonised rapidly by common frogs and three species of newts, and successful breeding was observed two years after pond creation. Although there was some movement of individuals between the ponds, after four years there were differences between the ponds in newt numbers and productivity. The results suggest that colonisation of empty patches can be down to chance.



14.30 - 14.45
VIGNIERI, SACHA, and Jim Kenagy. Department of Zoology and Burke Museum, University of Washington, Seattle, WA 98195, USA, <sachav@u.washington.edu>.

CAN LOCAL RESULTS PREDICT REGIONAL EFFECTS: HIERARCHICAL POPULATION STRUCTURE IN PACIFIC JUMPING MICE

A relationship exists between the demographic processes occurring within a single sub-population and the persistence of a species as a whole. This relationship is especially important in species that are distributed patchily due to habitat heterogeneity or habitat fragmentation. In such species, breeding structure and the number of successful migrants contribute directly to the degree of relatedness and stability of the sub-population. The Pacific jumping mouse, Zapus trinotatus, a species distributed across naturally patchy riparian habitat, provides a unique model system in which to examine how processes occurring at the smallest population scale translate into population structure observed at higher levels. To reveal the connections that exist across hierarchical population levels in this species, we use a combination of mark-recapture methods and multiple microsatellite loci to examine the demographic processes, social structure, and genetic relatedness within a single sub-population and the conversion of these patterns into genetic population structure at local and regional scales. A quantitative trend may exist between population scales (sub-population, metapopulation, metapopulation groups). These data are used to construct a population model that has the potential to predict the effects that forced isolation at the small scale (i.e. fragmentation) may have on subsequently higher scales.



14.45 - 15.00
LOWE, WINSOR H. Department of Biological Sciences, Dartmouth College, Hanover, New Hampshire 03755-3577, USA, <winsor.lowe@dartmouth.edu>.

LANDSCAPE-SCALE SPATIAL POPULATION DYNAMICS IN HUMAN-IMPACTED STREAM SYSTEMS

The movement of individuals among populations can be critical in preventing local and landscape-scale species extinctions in systems exposed to human perturbation. Current understanding of spatial population dynamics in streams is largely limited to the reach scale and is therefore inadequate to address species response to spatially extensive perturbation. Using model simulations, I examined species response to perturbation in a drainage composed of multiple, hierarchically arranged stream-patches connected by in-stream and overland pathways of dispersal. Patch extinction probability, the proportion of initially occupied patches extinct after 25 years, was highly sensitive to the extent of species occupancy and perturbation within the drainage, longitudinal species distribution, perturbation decay rate and the covariance pattern of stochastic effects on colonisation and extinction probabilities. Results of these simulations underscore the importance of identifying and preserving source populations and dispersal routes for stream species in human-impacted landscapes. They also highlight the vulnerability of headwater specialist taxa to anthropogenic perturbation, and the strong positive effect on species resilience of habitat rehabilitation when recolonisation is possible. Efforts to conserve and manage stream species may be greatly improved by accounting for landscape-scale spatial population dynamics.