Demographic analyses suggest that chelonians will have a low ability to withstand harvesting, although most have been based on stationary or declining populations. In contrast to this prediction, a population of Testudo graeca grew at the instantaneous rate r = 0.137 from 1980–1990, with a doubling time of 5 years. r was similar in both adult and 10 cm animals, showing that this high rate was not due to changes in population structure, and may thus be taken as an intrinsic rate of increase (rm). rm was higher than that of most large mammals, and suggests that sustainable harvesting would be a viable conservation strategy for chelonians if tightly regulated. Ranching or farming operations for chelonians would be even more likely to succeed, given their high fecundity. A resumption of trade in Mediterranean tortoises is, however, unlikely to be economically sustainable.

Male fiddler crabs have one of their feeding claws greatly enlarged, which may comprise up to 40% of their weight. In southern Portugal (Ria Formosa) the major claw of the fiddler crab Uca tangeri is a local delicacy. Fishermen break off the male major claw and throw the crab back into the mudflat to regenerate a new one. Approximately 38 % of the males sampled had a missing or a regenerating claw. Although individuals are not removed from the population the operational sex ratio is biased towards females since other males and females behave towards clawless males as if they were females. Moreover, removing the major claw from males prevents them from signalling (waving display) to females to attract them to their breeding burrows and it also places them at a disadvantage if they have to defend their burrows from males with intact claws. Thus, the harvesting of male fiddler crab claws has potential consequences at the population level. In this paper we investigated these potential consequences by comparing an exploited population of fiddler crabs at Ria Formosa with a remote population at the Mira estuary that is not under human exploitation. The unexploited population has significantly larger males and a significantly higher density of burrows. The operational sex ratio is also significantly different between the two populations with a female-biased sex ratio in the exploited population. These preliminary results suggest that claw harvesting in fiddler crabs has a measurable effect at the population level. The consequences of this type of fishery in which the individuals are not removed from the population but the population structure is potentially affected need further investigation.

We present a comparative analysis of correlates of Red data book status that controls for phylogeny. As a model system we use 244 species of hoverfly (Diptera: Syrphidae) from the British fauna, with their Red data book statuses in Britain and three regions of Germany. The analysis is confined to four adult characters, with Red data book status as the dependent variable. Associated with an increase in risk of extinction were a decrease in flight period and an increase in wing length (in two regions). Variables representing the number of habitats occupied and whether species were single- or multi-brooded were not associated with an increase in risk of extinction. At this stage we restrict our analysis to the identification of patterns rather than speculation as to causal mechanisms, but the patterns themselves are of value to conservation biologists, provided the methods used to identify them control for the possible confounding effects of phylogeny.

The current decline of the highly endangered African wild dog (Lycaon pictus) may be partly due to the population dynamics induced by their social system. African wild dogs are obligate co-operators, and their need for helpers could generate inverse density dependence at the pack level. We show, through a mathematical model, that this can create an Allee effect, leading to a lower population size and a higher risk of population extinction, compared to populations with direct density dependence. This is due to three different processes. All three processes can increase population extinction individually and probably occur simultaneously in African wild dogs. First, inverse density dependence causes significantly higher rates of pack extinction. Second, it also increases the probability of failure to colonize territories by founders. Third, the Allee effect at the pack level (with a critical number of individuals), generates an Allee effect at the population level (with a critical number of packs). These three processes are likely to apply to other obligate co-operative breeders. Furthermore, our results suggest that habitat fragmentation and destruction, as well as increased human pressure, increase the effects of inverse density dependence. Direct and indirect anthropogenic effects may thus be more detrimental to obligate co-operative breeders than to other species.

Although capture–recapture techniques are often used to estimate population size, these approaches are difficult to implement for a wide variety of species. Highly polymorphic microsatellite markers are useful in individual identification, and these ‘molecular tags’ can be collected without having to capture or trap the individual. However, several sources of error associated with molecular identification techniques, including failure to identify individuals with the same genotype for these markers as being different, and incorrect assignment of individual genotypes, could bias population estimates. Simulations of populations sampled for the purpose of estimating population size were used to assess the extent of these potential biases. Population estimates tended to be biased downward as the likelihood of individuals sharing the same genotype increased (as measured by the probability of identity (PI) of the multi-locus genotype); this bias increased with population size. Populations of 1000 individuals were underestimated by ≥5% when the PI was as small as 1.4 × 10−7. A similar-sized bias did not occur for populations of 50 individuals until the PI had increased to approximately 2.5 × 10−5. Errors in genotype assignment resulted in overestimates of population size; this problem increased with the number of samples and loci that were genotyped. Population estimates were often >200% the size of the simulated populations when the probability of making a genotyping error was 0.05/locus and 7–10 loci were used to identify individuals. This bias was substantially reduced by decreasing genotyping error rate to 0.005. If possible, only highly polymorphic loci that are critical for the identification of the individual should be used in molecular tagging, and considerable efforts should be made to minimize errors in genotype determination.

Fluctuating asymmetry (FA), a measure of developmental stability, has been proposed as a simple technique for identifying populations suffering from inbreeding and a loss of genetic diversity. However, there is controversy regarding the relationship between FA and both allozyme heterozygosity and pedigree inbreeding coefficients (F). FA of sternopleural bristle number in Drosophila melanogaster was measured in populations maintained at effective sizes of 25 (8 replicates), 50 (6), 100 (4), 250 (3) and 500 (2) for 50 generations (inbreeding coefficients of 0.05—0.71). FA was calculated from the same data set using three different indices (FA1, FA5 and FA6). There was no significant relationship of FA with pedigree inbreeding coefficients for any of the three indices. The relationship between FA and allozyme heterozygosity was non-significant for indices FA5 and FA6 (the more powerful indices) and only significant for FA1. A second comparison of highly inbred (F ≈ 1) populations with their outbred base population showed significantly greater FA in the inbred populations only when analysed with FA6. Analysis of the same data using FA1 and FA5 showed non-significant relationships in the opposite direction. If a relationship between FA and genetic diversity does exist, it is weak and inconsistent. Consequently, our results do not support the use of FA as a monitoring tool to detect inbreeding or loss of genetic diversity.

Population structure of the threatened long-tailed bat (Chalinolobus tuberculatus) was studied over five summers between 1993 and 1998, in temperate Nothofagus rainforest in Fiordland, New Zealand. Composition of 95 communal groups was sampled and spatial distribution of individually marked bats investigated. Individual C. tuberculatus moved to new roost sites virtually every day. Long term non-random associations among individuals were found by a cluster analysis that revealed three distinct social groups. Groups contained on average 72.0 (± 26.0) (mean ± SD), 99.3 (± 19.0) and 131.7 (± 16.5) marked individuals/year. Collective foraging ranges of the three groups overlapped but roosting occurred in three geographically distinct adjacent areas. Only 1.6% of individuals switched between groups. Non-reproductive females and males switched between groups more often than reproductive females but individuals switched only once or twice during the study and then just for one night. Juveniles of both sexes were associated with their natal group as 1 year-olds and then later when breeding. Social groups were cryptic because foraging ranges of groups overlapped, bats belonging to each group spread over many roosts each day, and these roost sites changed from day to day. Bats moved infrequently between groups, potentially linking the local population assemblages. Future research should explore whether the population is structured in demes. Population structure did not conform to traditional metapopulation models because groups occurred in homogeneous habitat extending over a large geographical area. Conserving bat populations should entail preserving a representative number of subgroups but development of models for predicting minimum number of effective local populations is still required.

Fitness and rates of extinction were compared among populations of the housefly, Musca domestica L., kept either at constant effective sizes of 50, 500 or 1500 or passed through extreme founder events reducing effective size to 5. Populations were maintained for 24 generations, which for small to medium-sized mammals would be less than the 200 years suggested by Soulé et al. (1986) as necessary for maintaining viable populations of endangered species. The results demonstrate that effective population sizes have to be greater than the 50 individuals suggested by Franklin (1980) to retain fitness and escape extinction, even in the short term. In contrast to populations of constant size that exhibited monotonic decreases in fitness through time, populations established with few founders rebounded from initial inbreeding depression. However, they were less adaptable to environmental stress than constant size populations, suggesting that populations founded with few numbers may do well within a single environment but may do far less well if they are reintroduced to natural environments or exposed to rapid environmental changes.

We document the recolonization of an indigenous large herbivore into its historic range. Eighteen wood bison (Bison bison athabascae) were reintroduced into the Mackenzie Bison Sanctuary of the Northwest Territories, Canada, in 1963. The population subsequently increased in number and range, peaking at about 2400 in 1989; numbers were estimated at about 1900 in 1998. Recolonization occurred through a series of increases in local areas followed by pulses of dispersal and range expansion. This pattern was originally described for exotic species' introductions. Differences in diet and overwinter survival of calves over the bison's range suggest that intraspecific competition for food provided the stimulus for range expansion. For a conservation strategy, the reintroduction of animals into several independent sites in their historic range would facilitate recolonization and achieve a faster spread than a reintroduction into one site followed by waiting for the population to spread as a result of its own density dependent responses.

We surveyed birds in cacao (Theobroma cacao) plantations in the state of Tabasco, Mexico. The shade canopy was planted by farmers and consisted of approximately 60 species of trees with no single dominant species. Canopy height averaged 15 m and the structure was multi-storied. We conducted 220 ten minute, 25 m radius point counts for birds and detected 1550 individuals from 81 species. The average number of birds/point and the expected diversity in a fixed number of individuals within the cacao surveyed were well within the range of other lowland habitats, including agricultural sites, that we have surveyed previously in neighbouring Chiapas. In the Tabascan cacao, the migrant group was composed, in part, of forest species, and dimorphic species were represented primarily by males, which in other areas are known to dominate forest or forest-like habitats. In contrast to the composition of migrant species, we found few resident forest specialists in Tabascan cacao. Instead, the tropical resident group was composed of large-bodied generalist species that use small patches of trees in open habitats. These results (moderate diversity, low numbers of forest specialists) differ from the few studies completed in ‘rustic’ cacao systems located near large tracts of forest. The planted shade cacao agroecosystem – at least in the absence of nearby forest – may have a limited value for conserving lost tropical forest bird diversity, but it provides habitat for woodland-associated migratory species. Our results also indicate that the planted shade cacao plantations supported few small omnivorous or frugivorous species, probably because cacao itself, as well as the dominant shade trees, produce primarily mammal or wind dispersed fruit and seeds.

A population viability analysis (PVA) was carried out for populations of the arboreal didelphid Micoureus demerarae in eight small (1.5–15.0 ha) forest fragments in south-eastern Brazil. Analysis was based on field data obtained through demographic studies carried out since 1995. Populations are small, but connected by dispersing individuals, thus forming a metapopulation. Frequency of catastrophic fires was estimated from the Reserve's historical records. We used the computer package VORTEX for all analyses. All populations and the metapopulation were found to be endangered within 100 years (extinction probability > 0.98). A sensitivity analysis was run varying six parameters: three demographic (sex ratio, migration and mortality rates), two environmental (K, fire frequency) and one genetic (level of inbreeding depression). Genetics, K, mortality rates and sex ratio seemed to play major roles to population persistence, whereas catastrophes and migration rates had a secondary role. Among demographic factors, extinction rate was least sensitive to migration rate. Micoureus demerarae can be used as a model species, thus improving our knowledge of how extinction-prone populations of neotropical arboreal marsupials in forest fragments might be, and which management actions could decrease such risks.

In rural New England, forest fragmentation is caused by housing developments in forested areas. To evaluate the effects of these changes on forest birds, we compared bird assemblages between forests with different housing densities in western Massachusetts. Species occurrences and relative abundances were determined from systematic point count surveys and mist-netting at three plots in forest of low housing density (0–0.05 houses/ha) and of moderate housing density (0.60–6.70 houses/ha) in 1993 and 1994. Among guilds, Neotropical migrants and forest-interior species had significantly lower abundances in forests of moderate housing density. Abundances of ground/shrub nesting birds as a group, and of individual species such as veery (Catharus fuscescens), ovenbird (Seiurus aurocapillus) and wood thrush (Hylocichla mustelina), were greater in forest of low housing density, but blue jays (Cyanocitta cristata) were more abundant in forest of moderate housing density. Although the abundances of ground/shrub nesting birds were positively related to ground cover, this vegetation structure did not differ between forest types. Avian and mammalian nest predators may be responsible for the trends in bird abundance. Avian nest predators may recognize forest of moderate housing density as edge habitat, and this rural development may also support relatively high densities of mammalian nest predators. These trends suggest that birds of New England's relatively extensive forests may be subject to greater fragmentation effects than generally thought, as a result of increasing rural housing development within forests.

The number of tiger subspecies is a major conservation issue that is difficult to resolve owing to small fragmented extant populations and limited historical samples in museums, which compromise the rigour of both molecular and morphological taxonomic studies. Rather than considering a static taxonomic approach to geographical variation in the tiger, we consider the changing biogeographical range of the tiger through the last glacial-interglacial cycle, based on habitat associations of modern tiger specimen records, and environmental reconstructions from the Last Glacial Maximum (LGM; approximately 20000 years before present (B.P.)). We regard this cycle as representative of the numerous glacial cycles that span the evolutionary history of the tiger since its appearance in the fossil record about two million years ago, thereby giving a deep-time perspective. The key issue is to determine the extent to which ancestral populations of the tiger were geographically isolated. If no geographical isolation is likely, and gene flow between tiger populations could be maintained until modern times, then diagnosably distinct populations could not have evolved. Our reconstructions show that only two tiger populations were likely to have experienced significant geographical isolation from the main species distribution; these were to the west of Tibet (during the LGM) and on Japan (throughout the glacial cycle). In addition, the LGM is likely to have seen the partial separation of peninsular Malayan and Sunda Islands tigers from mainland populations. From a biogeographical perspective it seems probable that only three contemporary populations were sufficiently separated for the evolution of distinct populations, which can be regarded as subspecies or evolutionary significant units. Therefore, most variation in modern tiger populations is probably clinal, which has important implications for future conservation strategies both in the wild and in captivity.

As a signatory of the Convention on Biological Diversity, the United Kingdom (UK) Government is obliged to conserve and enhance biodiversity. One step towards addressing this goal is to determine the level of biodiversity conservation already achieved within the current array of protected areas. We used national distribution data for ten taxonomic groups, and location information for three reserve networks, to assess the contribution of nature reserves to biodiversity conservation in Great Britain at the 10 km square (=100 km2) resolution. For several taxonomic groups, 10 km squares containing nature reserves had a significantly greater overlap than random networks with both hotspots (areas of high species richness) and complementary areas (sets of sites within which all species are represented). In addition, more than 94% of species from each taxonomic group have been recorded within the 10 km squares of the three reserve networks. These results provide some encouragement in terms of the UK meeting its commitment to conserve biodiversity.

Translocation is an important tool in conservation biology. However, translocation success is generally low for numerous animal species, therefore experiments are required for improvement. We carried out an experimental translocation of European wild rabbits (Oryctolagus cuniculus). The results may be of great interest for conservation biology, although we used a common species. As rabbits are known to experience a high mortality during the first days following release, it was necessary to assess the influence of handling trauma and environment novelty, respectively, and ways of suppressing them. Both tranquillization treatment during handling and a ‘soft’ release protocol (acclimatization pens in the new territory) were tested. Tranquillization did not increase survival, while the effect of acclimatization depended on sex. Females survived better when acclimatized, while males showed the opposite tendency. This difference is discussed in terms of sex-specific social behaviour, which is possibly an important correlate of translocation success. Finally, environmental stress seemed to override handling stress in determining the level of early survival for translocated wild rabbits.

Biotic homogenization is seen as the consequence of preferential loss of native species followed by ecological replacement with widespread exotics. Homogenization is not random in its effects on higher taxa. Using Monte Carlo simulations (rather than binomial statistics) we find taxonomic patterns in the risk of extinction and probability of successful introduction among birds. Sixteen avian families selectively contain extinct or threatened birds. Eight avian families selectively contain successfully introduced birds. Eight of these 24 taxonomically selected families have not been identified in previous studies, presumably because they are species-poor. The 22 living taxonomically selected families are classified into four homogenization categories. These categories reflect how extinction and invasion are combining in their effects at the family level. Range size, as indexed by island endemism, and human influence are the primary forces driving taxonomic homogenization patterns among birds. There is no evidence that evolutionary age influences homogenization patterns. Phylogenetic comparative analyses, which explicitly recognize the role of human influence, are needed to elucidate more detailed ecological correlates to homogenization trends.

The general problem of evaluating the potential success of mammalian reintroduction plans has been tackled by a case study illustrating a four-phase approach to finding and assessing potential sites for the reintroduction of European beavers, Castor fiber, to Scotland, combining the use of Geographic Information Systems (GIS), fieldwork and population modelling. Phase 1 used GIS to investigate the wider availability of habitat for beavers in Scotland, and predicted that there is the capacity to support in the order of 180 to 390 beaver families. Phase 2 involved the preliminary assessment of nine sites using brief field surveys. Phase 3 focused further on the three most suitable sites, where a thorough habitat survey was used as a basis for calculating carrying capacities of between three and five families. Finally, phase 4 used population modelling to assess the viability and likely spread of beavers following release at these three best sites. High, medium and low parameters were derived from the literature, and populations were predicted to persist and spread as long as at least the medium parameters were used. This exercise illustrates the power of combining field surveys and GIS-based population modelling as a tool for planning reintroductions in general, and as a foundation for planning the reintroduction of beavers in particular.

The amount of genetic differentiation between the African wild cat (Felis lybica) and the domestic cat (F. catus) in southern Africa is not known, but there is concern that interbreeding between the two may have been sufficiently extensive to threaten the status of the wild cat as a genetically distinct population. Eight hypervariable microsatellite loci were therefore used to determine the genetic relationships within and among wild and domestic cat populations. Measures of genetic differentiation, including FST and RST, confirmed significant differentiation between the wild and domestic cat populations and no significant differentiation between two widely separate domestic cat populations. Our data indicate that the level of genetic introgression is lower than previously thought. This enhances the conservation status of the African wild cat and demonstrates the need for the implementation of feral cat control in and around game reserves and rural areas.

We synthesize the results of empirical studies of marine reserves to assess the potential benefits of protection for fish populations. Our meta-analyses demonstrate that the overall abundance of fishes inside reserves is, on average, 3.7 times higher than outside reserve boundaries. This enhancement is mainly a result of a significant increase in abundance of species that are the target of fisheries. Non-target species are equally abundant inside and outside reserves. Large-bodied species also respond more to protection, irrespective of their fishery status. Species within genera show great heterogeneity in their response to protection despite similarities in their life histories. Our study confirms that marine reserves benefit fish populations and highlights the need for monitoring prior to reserve establishment to provide more accurate, habitat-controlled studies of the effects of marine reserves on fish populations.

Osmoderma eremita, an endangered beetle restricted to hollow trees, was surveyed in stands of different size, isolation and physical characteristics in an area in south-eastern Sweden. To infer habitat occupancy the presence/absence of fragments of adult body parts was used. Mark–release–recapture of adults with pitfall traps set in tree hollows was carried out to estimate local population size. Habitat occupancy/tree was higher in larger stands than in smaller stands, but there was no correlation between occupancy/stand and isolation of stands. This suggests dispersal is important in the population processes within stands, but not between stands. Osmoderma eremita was found in most of the larger stands and this probably mirrors the fact that the density of old-growth oaks has been much higher in the area than today. Habitat fragmentation over the last two centuries has disrupted the network of habitat patches, thus preventing dispersal into smaller, younger stands. A minimum number of suitable trees aggregated in stands seems to be necessary to provide long-term viability of local O. eremita populations. To preserve viable O. eremita populations, it is therefore necessary to increase size and connectivity of stands with hollow trees.