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Estimating population size in the Subdesert Mesite (Monias benschi): new methods and implications for conservation
Abstract
The subdesert mesite, a terrestrial non-passerine bird endemic to the Mikea Forest of southwest Madagascar, is currently classified as globally threatened (category: Vulnerable). However, accurate assessment of threat in accordance with the IUCN Red List criteria (A, B and C) requires data on effective population size, area of habitat occupied and rate of decline, none of which is available for this species. Here we present the first empirical estimates of its population size using five complementary methods, three incorporating data on territory size and two using data gathered during call-playback surveys conducted throughout its entire global range. Estimates vary from 98,000 to 152,000 individuals, with the most reliable possibly being that generated by distance sampling (115,000). This figure is more than an order of magnitude greater than the only published estimate of
... Playback of vocalizations regularly fails to elicit a response and the species rarely sings after dawn , therefore vocalizations do not provide a useful tool for assessing population size (cf. Tobias and Seddon 2002a). The best means of detecting the species is by searching for footprints and nest-holes; its nest-burrow entrance is distinctive and conspicuous, particularly as it is preferentially sited in open sand on the edge of small clearings or tracks, and its footprints are easily identified with practice (Tobias and Seddon 2002b). ...
... Presumably, it can only dig nest-burrows into soft sand, and not into firm or humic soils. In optimal habitats, the Subdesert Mesite appears to be considerably more abundant, and its total population probably exceeds 100,000 individuals (Tobias and Seddon 2002a), partly because it lives in groups rather than pairs. This disparity notwithstanding, it is possible that the mesite is more highly threatened than the ground-roller simply because it fares poorly in degraded or secondary habitat. ...
... However, the data presented above suggest that a global population estimate of 20,000 mature individuals is more reasonable, in which case, as with the Subdesert Mesite, the species only qualifies for Threatened status if we predict a rapid population decline. Given that over 16% of the original forest cover has declined since 1962, and the annual rate of deforestation is increasing by 0.93% per annum (Seddon et al. 2000, Tobias andSeddon 2002a), this prediction seems plausible. Indeed, although Long-tailed Ground Rollers appear to prefer slightly degraded forest, they do not occur in habitat that has been completely deforested. ...
The Long-tailed Ground-roller (Uratelornis
chimaera) is a globally Vulnerable, restricted-range species of dry forests in south-west Madagascar. We studied a population in 1997–2000, finding that nest-building was relatively synchronous and that pairs preferentially nested next to open areas, such as driveable tracks. By searching for trackside nests and for footprints, we conducted surveys throughout the known range of the species. Total transect coverage was 153 km, along which we encountered a minimum of 28 breeding pairs. By dividing the transects into 41 randomly distributed survey strips, each 1.2 km in length and 200 m broad, we intensively sampled an area of 9.84 km2. Using transect data, we made a tentative estimate of 5.7 mature adults km−2, from which we estimated a global population of 21,092 individuals, based on our calculation from satellite imagery that 3,706 km2 of suitable habitat remained. By comparing habitat data at points with and without ground-rollers we found that, contrary to previous statements, they prefer lower stature or degraded habitats, and have no direct association with the endemic cactus-like tree Didierea
madagascariensis. We used a novel census technique to provide the first quantitative data on population size, population density, breeding behaviour and ecology in the Long-tailed Ground-roller, or any member of the family Brachypteraciidae, information that is crucial to the design of effective conservation programmes.
... Fieldwork was carried out at two sites: PK32 (23°04%57S, 43°37%15E, 200 ha), Mangily (23°07%09S, 43°37%30E, 120 ha) and along nine transects in the Mikea Forest north of Manombo (see Tobias and Seddon 2002b). Detailed descriptions of the vegetation and climate of these sites are given in Seddon et al. (2000). ...
... In Experiment 3 we played recordings of 1 -4 intruders to a total of 104 groups of known size and composition. Of these groups, 13 were located along the Tsifota -Ankililoaka transect on 4 January 1999, 69 were located along eight transects north of Manombo between 28 November and 13 December 1999 and 22 were located along the PK32 -Mikoboka Plateau transect on 25 November 1999 (Tobias and Seddon 2002b). We used the responses of these groups to playback to investigate whether group size, the number of males, the number of females, the number of males per female per group ('sex ratio') or the number of defenders relative to the number of intruders ('odds ratio') influenced the likelihood that a group approached playback. ...
... In experiments 1 and 2 groups were 20 -25 m away at the start of playback, but in experiment 3 playbacks were conducted at varying initial distances (10 -300 m). The methods used for estimating initial distances of these groups are described elsewhere (Tobias and Seddon 2002b). Initial distance had no significant effect on the likelihood of approaching playback of any type (logistic likelihood ratio test, x 2 1 =2.60, ...
It has long been suggested that competing groups of social animals assess one another on the basis of communal vocalisations, but so far this has only been demonstrated in mammals. We investigated this idea in the subdesert mesite, a group-living bird that produces communal songs during aggressive territorial interactions with other groups. Where groups compete as units, differences in group size might outweigh inter-individual differences in determining the outcome of contests. Given this species’ variable social system, we predicted that the composition of groups would also influence their resource holding potential. Playback experiments showed that the number of simulated intruders significantly influenced the strength of response by defending groups hearing the stimulus: groups were less likely to approach but gave more protracted and more communal vocal responses as the number of vocalising intruders increased. We found that the likelihood of a group approaching playback increased as the ratio between the number of males in the defending group and the number of males in the intruding group increased. Furthermore, the ratio of adult males to females in the defending group significantly affected the probability of approach, with the probability increasing as groups became more male-biased. This finding supports the idea that the social structure of groups may be important in determining the outcome of contests between groups. Overall this study provides some indication in birds of relative numerical assessment based on vocal cues.
... The other main components of macro-scale assessments have been demographic factors, including population size and density, and rates of population decline, all of which are theoretically related to extinction risk [15,17]. In general, only crude population estimates are included in global-scale analyses because very few attempts have been made to quantify population sizes and trends across entire global ranges [18,19]. Previous studies have shown that both extrinsic biogeographic and demographic factors are correlated with extinction risk, leading to their widespread inclusion in regional and international conservation status assessments. ...
... However, the accuracy of Red List assessments might be improved by using life history and behaviour to scale terms in the criteria which are difficult to assess or define, such as 'number of mature individuals', 'future rate of decline' and 'severe fragmentation' [20]. These factors are typically judged with a considerable degree of inference (see [18,19]). The IUCN Red List Guidelines [56] on how to assess parameters such as these could usefully be augmented with further guidance in relation to ecological and behavioural factors such as mating systems, sex ratios, reproductive rate and predation pressure, dispersal ability, gap-crossing ability and ecological specialism. ...
Insights into animal behaviour play an increasingly central role in species-focused conservation practice. However, progress towards incorporating behaviour into regional or global conservation strategies has been more limited, not least because standardized datasets of behavioural traits are generally lacking at wider taxonomic or spatial scales. Here we make use of the recent expansion of global datasets for birds to assess the prospects for including behavioural traits in systematic conservation priority-setting and monitoring programmes. Using International Union for Conservation of Nature Red List classifications for more than 9500 bird species, we show that the incidence of threat can vary substantially across different behavioural categories, and that some types of behaviour—including particular foraging, mating and migration strategies—are significantly more threatened than others. The link between behavioural traits and extinction risk is partly driven by correlations with well-established geographical and ecological factors (e.g. range size, body mass, human population pressure), but our models also reveal that behaviour modifies the effect of these factors, helping to explain broad-scale patterns of extinction risk. Overall, these results suggest that a multi-species approach at the scale of communities, continents and ecosystems can be used to identify and monitor threatened behaviours, and to flag up cases of latent extinction risk, where threatened status may currently be underestimated. Our findings also highlight the importance of comprehensive standardized descriptive data for ecological and behavioural traits, and point the way towards deeper integration of behaviour into quantitative conservation assessments.
This article is part of the theme issue ‘Linking behaviour to dynamics of populations and communities: application of novel approaches in behavioural ecology to conservation’.
... The other main components of macro-scale assessments have been demographic factors, including population size and density, and rates of population decline, all of which are theoretically related to extinction risk [15,17]. In general, only crude population estimates are included in global-scale analyses because very few attempts have been made to quantify population sizes and trends across entire global ranges [18,19]. Previous studies have shown that both extrinsic biogeographic and demographic factors are correlated with extinction risk, leading to their widespread inclusion in regional and international conservation status assessments. ...
... However, the accuracy of Red List assessments might be improved by using life history and behaviour to scale terms in the criteria which are difficult to assess or define, such as 'number of mature individuals', 'future rate of decline' and 'severe fragmentation' [20]. These factors are typically judged with a considerable degree of inference (see [18,19]). The IUCN Red List Guidelines [56] on how to assess parameters such as these could usefully be augmented with further guidance in relation to ecological and behavioural factors such as mating systems, sex ratios, reproductive rate and predation pressure, dispersal ability, gap-crossing ability and ecological specialism. ...
Insights into animal behaviour play an increasingly central role in species-focused conservation practice. However, progress towards incorporating behaviour into regional or global conservation strategies has been far more limited, not least because standardised datasets of behavioural traits are generally lacking at wider taxonomic or spatial scales. Here we make use of the recent expansion of global datasets for birds to assess the prospects for including behavioural traits in systematic conservation priority-setting and monitoring programmes. Using IUCN Red List classification for >9500 bird species, we show that the incidence of threat can vary substantially across different behavioural syndromes, and that some types of behaviour - including particular foraging, mating and migration strategies - are significantly more threatened than others. When all factors are included in a combined model, behavioural traits have a weaker effect than well-established geographical and ecological factors, including range size, body mass and human population pressures. We also show that the association between behavior and extinction risk is partly driven by correlations with these underlying factors. Overall, these results suggest that a multi-species approach at the scale of communities, continents and ecosystems can be used to identify and monitor threatened behaviours, and to flag up cases of latent extinction risk, where threatened status may currently be underestimated. Our findings also highlight the importance of comprehensive standardized descriptive data for ecological and behavioural traits, and point the way forward to a deeper integration of behaviour into quantitative conservation assessments.
... The most commonly used ecological criteria to support planning processes are based on vegetation characteristics. Examples of common vegetation characteristics to determine preferred areas for conservation are: presence of endemic species (Kala, 2000); presence of species in danger of extinction (Tobias and Seddon, 2002); presence of rare species (Stern, 2003); and fauna/flora richness Store and Kangas, 2001). These criteria can be roughly divided into two conservation strategies known as single large or several small (SLOSS). ...
Urban land-use allocation in areas of transition (ecotones) is a complex task due to tensions between the need to develop residential and industrial areas and the wish to preserve high biodiversity and heterogeneous landscapes. This controversy is especially enhanced in a small and dense country like Israel, where efforts to achieve sustainable development are faced with difficulties typical of sensitive ecological regions and rapid population growth. This study incorporates the use of a multi-criteria mechanism in a GIS for the evaluation of the suitability of ecologically sensitive areas for four possible land-uses: nature reserves; forest plantations; residential areas; and industrial areas. The evaluation procedure pronounces the effect of: existing land-uses; soil characteristics; topographic attributes; vegetation cover; and landscape heterogeneity (as expressed by the Habitat Heterogeneity Model (HHM) that was developed within the frame of this study). The study area is the surroundings of a city that was established 30 years ago and is located in a transition zone between Mediterranean climate and the desert. The evaluation method used here provides a suitability layer for each of the four land-uses and a final layer that could recommend the most suitable land-use for each cell. The outcome of the system developed can be used as a basis for planners and decision makers dealing with the development of cities and their surroundings in regions of high ecological and environmental sensitivity.
... Investigators conducting distance sampling studies should always consider the training of observers at measuring distances (as in e.g. Baldi et al., 2001;Tobias and Seddon, 2002), which has been shown to reduce error and bias in distance estimates (Alldredge et al., in press). Additionally, I recommend the use of best possible technology to aid in the process of distance measurement. ...
... Ensuite, une investigation biologique menée dix ans passés dans différentes localités au sein de la forêt de Mikea a révélé l'importance et l'intérêt biologique en herpétofaune de cette région (Raselimanana, 2004 (Seddon, 2002;Tobias & Seddon, 2002Seddon et al., 2000Seddon et al., , 2002Seddon et al., , 2004Seddon et al., , 2005 ). ...
2012. Un premier aperçu de la faune de vertébrés du bush épineux de Salary-Bekodoy, à l'ouest du Parc National de Mikea, Madagascar. Malagasy Nature, 6: 1-23. uniquement dans la région du Sud-ouest ont été répertoriées. La forêt de Salary-Bekodoy constitue également la nouvelle limite nord connue de la distribution de Coua verreauxi. Deux espèces de petits mammifères, une espèce de chauve-souris et deux espèces de lémuriens y ont été aussi répertoriées. Les informations récoltées sont d'une importance non négligeable aussi bien sur le plan biologique que biogéographique et enrichissent la connaissance relative à cette forêt. Extended abstract To date, no scientific information is available concerning the faunal diversity of the Salary-Bekodoy Forest, in the western portion of the dry forest of the Mikea region, and adjacent to the western limit of the Mikea National Park. A multidisciplinary survey was carried out for seven days in early December 2011 to investigate the vertebrate faunal diversity of this forest. The target groups included amphibians, reptiles, birds, terrestrial small mammals, bats, carnivora, and lemurs. Standard survey methods were used in the representative habitats of the area, including pitfall, Sherman and national traps, mist nets, direct observation, refuge examination, and transect sampling. Despite the dry weather, which is not favorable to animal activity, the investigation revealed 28 species of reptiles, 12 of which are endemic to the south and southwest regions and rarely encountered; these include the burrowing snake Liophidium chabaudi, the arboreal snake Lycodryas inornatus, and an arboreal day gecko Phelsuma standingi. These species are poorly represented in the existing protected area network. Fifty bird species were recorded, of which 12 are confined to the Malagasy dry forest, and two "Vulnerable" species, Monias benschi and Uratelornis chimaera, only occur in the region between the Mangoky and Fiherenana Rivers. The Salary-Bekodoy Forest represents the new northern distributional limit of the "Near Threatened" bird species Coua verreauxi. Two species of tenrecs (Geogale aurita and Echinops telfairi), one bat species (Triaenops furculus), and two lemur species (Lepilemur ruficaudatus and Microcebus griseorufus) Résumé Peu d'information scientifique est disponible sur la faune de la forêt de Salary-Bekodoy, qui fait partie du bloc forestier de Mikea et est adjacente à la partie Ouest du Parc National de Mikea. Cette forêt a fait l'objet d'un inventaire biologique de la faune des vertébrés pendant sept jours au début du mois de décembre 2011. Les groupes cibles incluent les amphibiens, les reptiles, les oiseaux et les mammifères. Des méthodes standardisées telles que le piégeage, la capture à l'aide de filets, les observations directes, la fouille systématique et l'itinéraire échantillon ont été adoptées. Au cours de la visite sur le terrain, l'investigation a permis de recenser 28 espèces d'herpétofaune dont 12 sont endémiques de la région du Sud-ouest et du Sud et rarement rencontrées. Ces espèces sont d'ailleurs peu représentées au sein du réseau des aires protégées. Cinquante espèces d'oiseaux dont 12 restreintes à la forêt sèche et deux se rencontrant
... A final piece in the jigsaw is knowledge, or lack thereof. The quality of information about tropical birds lags far behind that available for the temperate zone in terms of taxonomy (Tobias et al. 2008a), population size (Tobias & Seddon 2002;Seddon & Tobias 2007) and conservation status (Tobias & Brightsmith 2007). Taxonomic revisions tend to reveal that many tropical bird species consist of more than one cryptic species, each with global ranges and populations smaller than previous estimates (Lohman et al. 2010). ...
Bird conservation is a global mission but most of the key battles are being played out in the tropics. This chapter summarizes the key attributes of tropical ecosystems and implications for bird conservation. First, it outlines threats to key tropical environments. Then it argues that tropical species often differ from their temperate-zone counterparts in ways that pose novel challenges for conservation. The chapter concludes that sustainable conservation of tropical birds and the ecosystem services they provide will be achieved only if attention is focused on biotic processes and interactions operating at larger spatial and temporal scales. The strategies proposed by the authors have broad relevance for the management of tropical diversity because birds have long been viewed as a model system for assessing conservation priorities, and act as flagships for numerous conservation programmes.
... Occasionally group size might have been underestimated as incubating birds may not have approached playback. However, over a sample of 69 groups the potential for this factor to confound the results is likely to have been small (see Tobias & Seddon 2002b). ...
In 1997–2000 we studied a population of Subdesert Mesites Monias benschi consisting of 35–68 adults comprising 32 groups of two to nine birds (modal group size of four). The study population was significantly male-biased in 1999 but not in 1997 or 1998. Overall, both sexes were philopatric, but when dispersal (or eviction) occurred, it appeared to be female-biased. Over 40% of groups contained more than two adult males, whilst < 15% contained more than two adult females. Whilst there was no evidence of behavioural dominance by females, intrasexual aggression within groups was observed only amongst females. In contrast to other birds occupying the same habitat, breeding in mesites was not tied to rainfall, and occurred throughout the year. Each breeding unit constructed several nests every year, only one of which was used. All adult males and at least one adult female co-operated to raise one or two clutches of one or two eggs per year. Males and females contributed equally to incubation. Chick production and chick survival were not related to group size or territory size. Groups defended large, permanent, and multipurpose territories and all group members contributed to territory defence. Territory size was positively correlated with the number of males in groups, but not with overall group size. Territories were tightly packed with very few areas unoccupied. Transect surveys conducted throughout the narrow geographical range of this species revealed its presence in a range of semi-arid habitat types. Small groups were more likely to be detected in intact, high-stature forest, whilst large groups were more likely to be detected in low-stature forest containing numerous spiny, xerophytic trees Didierea madagascariensis.
... Thus, it seems likely that a significant proportion of species classified as threatened, if subjected to detailed field work and analysis, would be shown to be more widespread or numerous than suspected on the basis of limited data (e.g. Jones et al., 1995;Tobias and Seddon, 2002;Seddon and Tobias, 2007;Tobias et al., in press;Trainor, in press). ...
Until recently thought to be secure (i.e. Least Concern), the Blue-headed Macaw is now classified as Endangered in the IUCN Red List, based on an apparent decline and a population estimate of <2500 mature individuals. We review published and unpublished sources, collating records from 61 localities in Peru, Brazil and Bolivia, and compiling information on habitat use, seasonality, group size, demography, and population density. We find the species to be associated with disturbed habitats at one site, but a broader analysis revealed no significant associations with forest type, riverine habitats, degree of disturbance or altitude. By mapping locality records, and accounting for discontinuities, we calculate an Extent of Occurrence of 460,000 km2. Range-wide data on encounter rates and flock sizes suggest that the species is sedentary and gregarious, with an overall population density of one mature individual per 10–50 km2. Our figures for range size and density (both highly conservative) indicate that the global population estimate should be revised upwards to 9200–46,000 mature individuals. Balanced against an increasing threat from trade, these data argue for a reversal in status to Vulnerable, with a shift to Near Threatened possible in future. Given these recent fluctuations in conservation status, the Blue-headed Macaw provides valuable insight into the difficulties of using IUCN Red List criteria to assess poorly known taxa. Red List assessments should be based on extensive reviews where possible, and analyses using Red List data should consider effects of data quality.
... The most commonly used ecological criteria to support planning processes are based on vegetation characteristics. Examples of common vegetation characteristics to determine preferred areas for conservation are: presence of endemic species (Kala, 2000); presence of species in danger of extinction (Tobias and Seddon, 2002); presence of rare species (Stern, 2003); and fauna/flora richness Store and Kangas, 2001). These criteria can be roughly divided into two conservation strategies known as single large or several small (SLOSS). ...
Urban land-use allocation in areas of transition (ecotones) is a complex task due to tensions between the need to develop residential and industrial areas and the wish to preserve high biodiversity and heterogeneous landscapes. This controversy is especially enhanced in a small and dense country like Israel, where efforts to achieve sustainable development are faced with difficulties typical of sensitive ecological regions and rapid population growth. This study incorporates the use of a multi-criteria mechanism in a GIS for the evaluation of the suitability of ecologically sensitive areas for four possible land-uses: nature reserves; forest plantations; residential areas; and industrial areas. The evaluation procedure pronounces the effect of: existing land-uses; soil characteristics; topographic attributes; vegetation cover; and landscape heterogeneity (as expressed by the Habitat Heterogeneity Model (HHM) that was developed within the frame of this study).The study area is the surroundings of a city that was established 30 years ago and is located in a transition zone between Mediterranean climate and the desert. The evaluation method used here provides a suitability layer for each of the four land-uses and a final layer that could recommend the most suitable land-use for each cell. The outcome of the system developed can be used as a basis for planners and decision makers dealing with the development of cities and their surroundings in regions of high ecological and environmental sensitivity.
... Both species are classified as globally Vulnerable (IUCN, 2008) based on rates of habitat loss and associated population decline. The global population of M. benschi is estimated at over 100, 000 individuals (Tobias & Seddon, 2002), while that of U. chimaera is estimated at around 20,000 (Seddon & Tobias, 2007). While M. benschi is considerably more abundant within relatively undisturbed habitat, the Mikea forest is increasingly degraded over much of its extent (Seddon et al., 2000), creating conditions more favorable to U. chimaera. ...
Madagascar’s recently established protected areas seek to contribute to both conservation and
development objectives. They comprise mainly multiple-use protected areas in which a range of
human activities are permitted, hence the impacts of forest use on biodiversity must be understood if such sites are to be designed and managed to minimize biodiversity loss. Here a review is conducted of the literature on the impacts of habitat change on Malagasy terrestrial biodiversity, and the associated range of responses of terrestrial taxa to habitat change are analyzed. Habitat change may lead to increases or decreases in species richness or abundance in the short term, but the use of measures of species richness alone may mask a turnover of taxa from specialists to generalists and from endemic to nonendemic. Dry forest species and communities may be less sensitive to habitat change than those of humid forests, and biodiversity impacts appear to follow a gradient of management intensity, with selective logging and edge effects having less impact on faunal communities than secondary forests and plantations. Priorities for future research are suggested and the implications of existing research for protected area management (including zoning, the choice of management objectives, target viability analyses and monitoring) are discussed. Although new protected areas provide complementary conservation services to the existing network of strict protected areas, the latter may be essential for the long-term maintenance of high priority endemic taxa.
... Social organization is very fluid: some groups comprise related individuals whereas others contain coalitions of unrelated birds; both sexes are essentially philopatric, but dispersal (or eviction) appears to be female-biased (; N. Seddon, unpublished data). The species is restricted to a 3700 km 2 area of semi-arid coastal woodland and scrub in southwest Madagascar (Seddon et al. 2001), where its total population was recently estimated at 115 000 individuals (Tobias & Seddon 2002). We studied 23 unique groups of mesites (electronic Appendix A, table 2) during three field seasons (September–January, 1997–2000 nations of coloured plastic leg-rings, and took 0.2 ml blood samples and standard biometric measurements (Seddon 2001; ). ...
Recent studies of non-social animals have shown that sexually selected traits signal at least one measure of genetic quality: heterozygosity. To determine whether similar cues reveal group quality in more complex social systems, we examined the relationship between territory size, song structure and heterozygosity in the subdesert mesite (Monias benschi), a group-living bird endemic to Madagascar. Using nine polymorphic microsatellite loci, we found that heterozygosity predicted both the size of territories and the structure of songs used to defend them: more heterozygous groups had larger territories, and more heterozygous males used longer, lower-pitched trills in their songs. Heterozygosity was linked to territory size and song structure in males, but not in females, implying that these traits are sexually selected by female choice and/or male-male competition. To our knowledge, this study provides the first direct evidence in any animal that territory size is related to genetic diversity. We also found a positive association between seasonal reproductive success and heterozygosity, suggesting that this heritable characteristic is a reliable indicator of group quality and fitness. Given that heterozygosity predicts song structure in males, and can therefore be determined by listening to acoustic cues, we identify a mechanism by which social animals may assess rival groups, prospective partners and group mates, information of potential importance in guiding decisions related to conflict, breeding and dispersal.
... The species is restricted to a 3700-km 2 area of semiarid coastal woodland and scrub in southwest Madagascar (Seddon et al . 2000), where its total population has been estimated at 115 000 individuals (Tobias & Seddon 2002). We studied a total of 23 unique groups during three field seasons (September–January 1997–2000; see Appendix I) at two sites in their natural range, separated by 6 km of contiguous vegetation: PK32 (23 ° 04 ′ 57 ′′ S, 43 ° 37 ′ 15 ′′ E; 200 ha) and Mangily (23 ° 07 ′ 09 ′′ S, 43 ° 37 ′ 30 ′′ E; 120 ha). ...
In the first molecular study of a member of the threatened avian family, Mesitornithidae, we used nine polymorphic microsatellite loci to elucidate parentage, patterns of within-group kinship and occurrence of extra-group paternity in the subdesert mesite Monias benschi, of southwest Madagascar. We found this cooperatively breeding species to have a very fluid mating system. There was evidence of genetic monogamy and polygynandry: of the nine groups with multiple offspring, six contained one breeding pair with unrelated helpers and three contained multiple male and female breeders with related helpers. Although patterns of within-group kinship varied, there was a strong positive relationship between group size and relatedness, suggesting that groups form by natal philopatry. There was also a strong positive correlation between within-sex and between-sex relatedness, indicating that unlike most cooperatively breeding birds, philopatry involved both sexes. In contrast to predictions of kin selection and reproductive skew models, all monogamous groups contained unrelated individuals, while two of the three polygynandrous groups were families. Moreover, although between-group variation in seasonal reproductive success was related to within-group female relatedness, relatedness among males and between the sexes had no bearing on a group's reproductive output. While kin selection may underlie helping behaviour in females, factors such as direct long-term fitness benefits of group living probably determine helping in males. Of the 14 offspring produced by fully sampled groups, at least two were sired by males from neighbouring groups: one by a breeding male and one by a nonbreeding male, suggesting that males may augment their reproductive success through extra-group paternity.
The aim of this study is to estimate the population size of Aegla longirostri Bond-Buckup and Buckup, 1994 in a subtropical low-order stream using the mark-recapture technique. We also tested if the Bayesian model is a promising estimator of population size. Data were collected in two periods, in spring 2010 (seven-day sampling) and in fall 2011(five-day sampling). The animals were sexed, measured, marked in the field, and released in the same spots from which they were collected. During the study period, 445 adults were captured (343 in the spring and 102 in the fall). The estimated population size was 1,005-1,028.8 individuals in the spring and 234-236 in the fall, according to the Schumacher-Eschmeyer and Schnabel methods, original arTiCle Nauplius, 26: e2018016
The decline of the Black-eared Miner Manorina melanotis has been caused primarily by habitat degradation and vegetation clearance. To better direct conservation actions for this species there was a need to assess habitat requirements on a regional-scale and to estimate the population size using quantitative methods. We used vegetation mapping and the current distribution of the Black-eared Miner to determine regional-scale habitat requirements. These findings were combined with the results of distance sampling to provide population estimates. The species is restricted to large tracts of intact mallee in the Murray Mallee of southeastern Australia that have not been burnt for at least 45 years. The density of Black-eared Miners is highest in areas that are dominated by mallee-Triodia associations and have not been intensively grazed. The Bookmark Biosphere Reserve supports an estimated 501 (270-927, 95% Cl) colonies, containing 3 758 (2 026-6 954) phenotypically pure Black-eared Miners, 2 255 (1 215-4170) hybrids and small numbers of Yellow-throated Miners Manorina flavigula. However, the effective population size is considerably smaller (390 Black-eared Miners (210-726) and 234 hybrids (126-433)), due to a skewed adult sex ratio (1 female: 1.81 males) and complex social organization. A smaller population also persists in the Murray Sunset National Park containing 53 (32-85) Black-eared Miner/hybrid colonies. Both populations face a high risk of extinction from large-scale wildfire. The endangered status of the species under IUCN criteria remains warranted.
Global climate fluctuations have significantly influenced the distribution and abundance of biodiversity [1]. During unfavorable glacial periods, many species experienced range contraction and fragmentation, expanding again during interglacials [2-4]. An understanding of the evolutionary consequences of both historical and ongoing climate changes requires knowledge of the temporal dynamics of population numbers during such climate cycles. Variation in abundance should have left clear signatures in the patterns of intraspecific genetic variation in extant species, from which historical effective population sizes (Ne) can be estimated [3]. We analyzed whole-genome sequences of 38 avian species in a pairwise sequentially Markovian coalescent (PSMC, [5]) framework to quantitatively reveal changes in Ne from approximately 10 million to 10 thousand years ago. Significant fluctuations in Ne over time were evident for most species. The most pronounced pattern observed in many species was a severe reduction in Ne coinciding with the beginning of the last glacial period (LGP). Among species, Ne varied by at least three orders of magnitude, exceeding 1 million in the most abundant species. Several species on the IUCN Red List of Threatened Species showed long-term reduction in population size, predating recent declines. We conclude that cycles of population expansions and contractions have been a common feature of many bird species during the Quaternary period, likely coinciding with climate cycles. Population size reduction should have increased the risk of extinction but may also have promoted speciation. Species that have experienced long-term declines may be especially vulnerable to recent anthropogenic threats.
Copyright © 2015 The Authors. Published by Elsevier Ltd.. All rights reserved.
Assessing the risk of extinction to species forms an essential part of regional conservation initiatives that facilitate the allocation of limited resources for conservation. The present study conducted conservation priority assessments for 221 South African terrestrial mammal species using existing data sources. These data sources included regional IUCN Red List assessments, regional geographic distributions, relative endemism, taxonomic distinctiveness, relative body mass and human density. These components were in turn subjected to two quantitative conservation priority assessment techniques in an attempt to determine regional conservation priorities for South African terrestrial mammals. The top 22 mammal species (i.e. the top 10% of assessed species) identified by both regional conservation priority assessment techniques to be of conservation priority, consistently identified 13 South African terrestrial mammal species to be of high conservation priority. Seven of the 13 species were from the order Afrosoricida, two species from the order Eulipotyphla, with one species each from the orders Chiroptera, Lagomorpha, Pholidota, and Rodentia. More importantly, 12 of the 13 mammal species were also listed as threatened in the 2004 Red Data Book of South African Mammals. These results suggest that the two conservation priority assessment techniques used in the present study may represent a practical and quantitative method for determining regional conservation priorities, and include measures that represent vulnerability, conservation value, and threat.
Some plants of Hebei Province in China are under threat from human activities, such as over-herding and over-exploitation
of wild medicinal plants and industrial plants, etc. To identify the plants in danger in the province and to inspect the quality
of the environment encompassing Beijing and Tianjin, a red list of the threatened flora of Hebei Province was produced by
using the IUCN Red List Criteria (version 3.1) and its guidelines (version 6.2). Some 262 species were assessed and the results
were as follows: (1) the threatened flora include 211 species, accounting for 7.95% of the total native vascular plants. Among
them, 44 are Critically Endangered, 80 Endangered and 87 Vulnerable; (2) the destruction of the habitat caused by human activities
and the actual or potential exploitation of the plants themselves were the main threat factors of Hebei flora; (3) most of
the threatened plants are located in the western, northern and northeastern mountainous regions, namely the key regions of
Hebei plant diversity; the endemic and regionally endemic species are severely threatened. Consequently, the assessment not
only presented the threatened status of Hebei flora but also indicated the relatively fragile health status of the environment
of Beijing and Tianjin. Thus, it is suggested that the application of the IUCN Red List Criteria at the regional level, as
an index, could reflect the health status of the local ecosystem. In addition, more concrete measures are needed to conserve
the plant diversity and the natural ecosystem of Hebei Province and even the whole region encompassing Beijing and Tianjin.
The ‘hotspot approach’ considers that endemism and threatened species are key factors in protected area designation. Three wetland and forest sites have been proposed to be included into Madagascar’s system of protected areas (SAPM – Système des Aires Protégées de Madagascar). These sites are Manambolomaty (14,701 ha) and Mandrozo (15,145 ha) in the west and Bemanevika (37,041 ha) in the north. Biodiversity inventories of these three sites recorded 243 endemic species comprised of 44 reptiles, 54 amphibians, 104 birds, 23 smallmammals, 17 lemurs and one fish. Of these 243 species, 30 are threatened taxa comprising two Critically Endangered (CR), 11 Endangered (EN) and 17 Vulnerable (VU) species. The long term ecological viability of these sites has been shown by population stability of the two Critically Endangered flagship species, the Madagascar fish eagle (Haliaeetus vociferoides) in Manambolomaty and Mandrozo and the recently rediscovered Madagascar pochard (Aythya innotata) in Bemanevika. Other threatened species and high biological diversity also justifies their inclusion into Madagascar’s SAPM.
The original publication is available at http://www.springer.com/ It is crucial for biodiversity conservation that protected areas are large and effective enough to support viable populations of their original species. We used a point count distance sampling method to estimate population sizes of a range of bird species in three Atlantic forest protected areas of size 5600, 22,500, and 46,050 ha. Population sizes were generally related to reserve area, although in the mid-sized reserve, there were many rare species reflecting a high degree of habitat heterogeneity. The proportions of forest species having estimated populations >500 ranged from 55% of 210 species in the largest reserve to just 25% of 140 species in the smallest reserve. All forest species in the largest reserves had expected populations >100, but in the small reserve, 28% (38 species) had populations <100 individuals. Atlantic forest endemics were no more or less likely to have small populations than widespread species. There are 79 reserves (>1000 ha) in the Atlantic forest lowlands. However, all but three reserves in the north of the region (Espírito Santo and states north) are smaller than 10,000 ha, and we predict serious levels of local extinction from these reserves. Habitat heterogeneity within reserves may promote species richness within them, but it may also be important in determining species loss over time by suppressing populations of individual species. We suggest that most reserves in the region are so small that homogeneity in the habitat/altitude within them is beneficial for maintenance of their (comparatively small) original species compliment. A lack of protection in the north, continued detrimental human activity inside reserves, and our poor knowledge of how well the reserve system protects individual taxa, are crucial considerations in biodiversity management in the region.
In this chapter, several observations and inferences about the evolutionary dynamics and character evolution of the 12S rDNA molecule have been presented. These include variation in secondary structure resulting from stem migration and uncompensated insertions and deletions within stems; replication slippage as a mechanism of sequence length variation in loops; differences in per-site substitution rates between birds and mammals; the process of compensatory substitution in stems; and differences in distributions of synapomorphies and homoplasies that are spatially correlated with functional and structural regions of 12S rDNA. A robust but simplified estimate of the instantaneous ratio of rates between transversions to transitions is calculated for the 12S rDNA of Gruiformes. 12S rDNA is not entirely saturated by homoplasious substitutions at the levels of gruiform divergence, because it performs well at resolving much older divergences. Yet it exhibits sufficient noise to hinder the resolution of a phylogeny that may be characterized by relatively short internodal branches. High rates of substitution thus are not confined to particular sites across taxa; they are found in different locations in different lineages.
This book is available for purchase, The 1993 version is available on the page at http://distancesampling.org/downloads/distancebook1993/index.html
The Montserrat Oriole Icterus oberi is endemic to the Caribbean island of Montserrat where, prior to 1995, it was widely distributed across the island's three main interior mountain ranges: the Centre, Soufriere and South Soufriere Hills. In July 1995, a long-dormant volcano on Chances Peak in the Soufriere Hills began to erupt. Since then the forest habitat of the oriole on the Soufriere and South Soufriere Hills has been devastated by pyroclastic flows and surges, heavy ash eruptions and rock falls. The Montserrat Oriole populations that inhabited these two mountain ranges have probably been lost. In December 1997, a census of the remaining Centre Hills population was undertaken to assess its status in the face of the heavy ash fall that occurred earlier the same year. To do this, a systematic grid of 140 sample points was overlaid on an area of 1,437.5 n a encompassing the Centre Hills, and a 10-minute count of all bird species was undertaken at 137 of these points during an eight-day survey period. The distance from the point to each oriole detected was measured and records of all other species were allocated to one of five distance bands radiating out from the point. Distance sampling was used to model densities, and thus to estimate population sizes, of eight bird species in the study area. It was estimated that 4,000 (95% CIs 1,500–7,800) Montserrat Orioles remain in the Centre Hills and thus the world. Although the probability of pyroclastic flows and surges overrunning the Centre Hills is considered rerrtote, it is recommended that the Montserrat Oriole be classified as Globally Threatened (Endangered) under the revised IUCN threat categories because of its loss of breeding habitat since 1995.
As an island endemic, the Island Scrub-Jay's Aphelocoma
insularis population status and conservation are of concern. In addition, because the Island Scrub-Jay is easily observed, it is an ideal candidate for monitoring the effects of management efforts on Santa Cruz Island, California. We used estimates of territory size in several different habitats occupied by the Island Scrub-Jay and the total area of these habitats on the island to develop an empirical estimate of the population size for this species. Our most conservative, and we feel most realistic, estimate for the Island Scrub-Jay breeding population is 7,000 individuals and for the non-breeding population 5,500 individuals, yielding a total population estimate of 12,500. Even though conservative, this estimate is larger than earlier estimates of 4,000 to 6,000 individuals. Even so, our data suggest no reason exists for immediate concern regarding the population viability of the Island Scrub-Jay and they provide a baseline for future estimates and comparisons. Most importantly, this population estimate can be used to monitor the influence on the Island Scrub-Jay of future island management efforts, especially regarding exotic tree species and feral pigs.
A survey was undertaken in 1995 to assess the conservation status of the Madeira Laurel Pigeon Columba trocaz, a threatened species endemic to the Island of Madeira. The first large scale survey was carried out 1986, following the cessation of legal hunting of the species, to provide a baseline for future monitoring of population changes. The current study therefore aims to (1) compare population size with those of 1986 and (2) employ distance sampling methods (not used in 1986) to obtain estimates of population density and size. Eighteen transects (13 repeated from the 1986 survey and five new) were conducted in the four main areas of laurel forest. Pigeon numbers had increased on nearly all transects but some of the highest increases, proportionately and often numerically, were in areas with lower numbers in 1986. We estimate the current population to be 10,400 individuals, a considerable increase since 1986, probably due to a ban on hunting. As laurel forest habitat is now very well protected the Madeira Laurel Pigeon is relatively safe from extinction.
A relation between body size and threat of extinction for animal species has often been hypothesized. However, evidence for the form of the relation is equivocal, and studies can be found reporting positive, negative, or no relation between body size and extinction risk. One way to assess this relation is to compare the body sizes of species considered to be globally threatened with those of species considered to be less at risk. We adopt this approach for birds, considering a bird to be in danger of global extinction if it was listed by Collar & Andrew (ICBP technical publication no. 8 (1988)). Threatened species of bird are, on average, larger-bodied than non-threatened species. This difference is not due to size differences between island endemic species and species with continental distributions. Island endemic and continental species show no consistent body size differences. The relation between body mass and threat of extinction is not due to differences between higher taxa: within taxa, there is still a relation between body size and extinction threat. We present evidence that the degree of threat faced by endangered species may also be related to body mass. We discuss possible explanations for the observed patterns, and conclude that a genuine tendency for large-bodied birds to be more at risk from extinction than small-bodied species is the most likely.
Overall, 217 lions (>1 year) Panthera leo (Linnaeus) and 2069 spotted hyaenas (>8 mo) Crocuta crocuta (Erxleben) responded to broadcast vocalizations, call-ins, during six surveys in the Masai Mara National Reserve, Kenya.
Carnivore response varied seasonally and was significantly higher and more uniform when migratory prey were absent. Variation in wildebeest abundance, by affecting food availability, was the only significant predictor of response. Variability in response with overall prey abundance was higher for lions than hyaenas. Lion response occurred within a radius of 2·5 km, was independent of age and sex but dropped virtually to zero whenever lions possessed a carcass at the time of broadcasting.
An independent total census recorded 547 lions (all ages) in the Reserve, 9·96% of which were nomads. This proportion increased by 7·94% following the influx of migrants and raised lion (>1 year) density from 0·292 to 0·320 lions/km2. The call-in estimate of 0·294±0·009 (95% c.l.) lions/km2 practically equalled the total count. The high precision and low bias (−0·224%) of this estimate imply that call-in surveys are reliable and may be employed to effectively monitor carnivore populations in the long term. Under simple random sampling, covering about 20% of an area would seem adequate to produce reliable density estimates.
Historical ecological studies provide information about the origins of species in an area and the origins of traits characterizing the interactions between those species and their environment. Incorporating this evolutionary information into conservation policies will broaden the base of options for making effective decisions about the preservation of biodiversity.
Collar et al. (1994) estimate that of the 9,672 extant species of bird, 1,111 are threatened by extinction. Here, we test whether these threatened species are simply a random sample of birds, or whether there is something about their biology that predisposes them to extinction. We ask three specific questions. First, is extinction risk randomly distributed among families? Second, which families, if any, contain more, or less, threatened species than would be expected by chance? Third, is variation between taxa in extinction risk associated with variation in either body size or fecundity? Extinction risk is not randomly distributed among families. The families which contain significantly more threatened species than expected are the parrots (Psittacidae), pheasants and allies (Phasianidae), albatrosses and allies (Procellariidae), rails (Rallidae), cranes (Gruidae), cracids (Cracidae), megapodes (Megapodidae) and pigeons (Columbidae). The only family which contains significantly fewer threatened species than expected is the woodpeckers (Picidae). Extinction risk is also not distributed randomly with respect to fecundity or body size. Once phylogeny has been controlled for, increases in extinction risk are independently associated with increases in body size and decreases in fecundity. We suggest that this is because low rates of fecundity, which evolved many tens of millions of years ago, predisposed certain lineages to extinction. Low-fecundity populations take longer to recover if they are reduced to small sizes and are, therefore, more likely to go extinct if an external force causes an increase in the rate of mortality, thereby perturbing the natural balance between fecundity and mortality.
The effective population size (Ne ) depends strongly on mating system and generation time. These two factors interact such that, under many circumstances, Ne is close to N/2, where N is the number of adults. This is shown to be the case for both simple and highly polygynous mating systems. The random union of gametes (RUG) and monogamy are two simple systems previously used in estimating Ne , and here a third, lottery polygyny, is added. Lottery polygyny, in which all males compete equally for females, results in a lower Ne than either RUG or monogamy! Given nonoverlapping generations the reduction is 33% for autosomal loci and 25% for sex-linked loci. The highly polygynous mating systems, harem polygyny and dominance polygyny, can give very low values of Ne /N when the generation time (T) is short. However, as T is lengthened, Ne approaches N/2. The influence of a biased sex ratio depends on the mating system and, in general, is not symmetrical. Biases can occur because of sex differences in either survival or recruitment of adults, and the potential for a sex-ratio bias to change Ne is much reduced given a survival bias. The number of juveniles present also has some influence: as the maturation time is lengthened, Ne increases.
Tape playback is often the only efficient technique to survey for secretive birds. We measured the vocal responses and movements of radiotagged black rails (Laterallus jamaicensis; 26 M, 17 F) to playback of vocalizations at 2 sites in Florida during the breeding seasons of 1992-95. We used coefficients from logistic regression equations to model probability of a response conditional to the birds' sex, nesting status, distance to playback source, and time of survey. With a probability of 0.811, nonnesting male black rails were most likely to respond to playback, while nesting females were the least likely to respond (probability = 0.189). We used linear regression to determine daily, monthly, and annual variation in response from weekly playback surveys along a fixed route during the breeding seasons of 1993-95. Significant sources of variation in the regression model were month ( $F_{3,48}$ = 3.89, P = 0.014), year ( $F_{2,48}$ = 9.37, P < 0.001), temperature ( $F_{1,48}$ = 5.44, P = 0.024), and month × year ( $F_{5,48}$ = 2.69, P = 0.031). The model was highly significant (P < 0.001) and explained 54% of the variation of mean response per survey period (r2 = 0.54). We combined response probability data from radiotagged black rails with playback survey route data to provide a density estimate of 0.25 birds/ha for the St. Johns National Wildlife Refuge. The relation between the number of black rails heard during playback surveys to the actual number present was influenced by a number of variables. We recommend caution when making density estimates from tape playback surveys.
We broadcast vocalizations of pied-billed grebe (Podilymbus podiceps), American bittern (Botaurus lentiginosus), least bittern (Ixobrychus exilis), Virginia rail (Rallus limicola), and sora (Porzana carolina) to derive a standardized method to monitor breeding populations of these secretive waterbirds. Broadcast of tape-recorded calls at 60 wetlands in Maine improved species detectability by 93-1, 320% over passive observation. Detection rates at wetlands where target species were known to occur ranged between 0.56 (least bittern) and 0.86 (pied-billed grebe) per survey visit. Three visits to a wetland were adequate to determine the presence or absence of all species with 90% certainty. Least bitterns, soras, and Virginia rails were detected primarily within 50 m of observers; pied-billed grebes and American bitterns were detected up to 500 m distant. Most responses were aural. Responsiveness of each species varied nonsystematically in relation to seasonal chronology, time of day, wind, precipitation, and cloud cover. Single, annual surveys at a stratified random sample of wetlands (i.e., waterbird "miniroutes") can generate sufficient encounter rates for these species to monitor population trends.
The effective population size (N<sub>e</sub>) depends strongly on mating system and generation time. These two factors interact such that, under many circumstances, N<sub>e</sub> is close to N/2, where N is the number of adults. This is shown to be the case for both simple and highly polygynous mating systems. The random union of gametes (RUG) and monogamy are two simple systems previously used in estimating N<sub>e</sub>, and here a third, lottery polygyny, is added. Lottery polygyny, in which all males compete equally for females, results in a lower N<sub>e</sub> than either RUG or monogamy. Given nonoverlapping generations the reduction is 33% for autosomal loci and 25% for sex-linked loci. The highly polygynous mating systems, harem polygyny and dominance polygyny, can give very low values of N<sub>e</sub>/N when the generation time (T) is short. However, as T is lengthened, N<sub>e</sub> approaches N/2. The influence of a biased sex ratio depends on the mating system and, in general, is not symmetrical. Biases can occur because of sex differences in either survival or recruitment of adults, and the potential for a sex-ratio bias to change N<sub>e</sub> is much reduced given a survival bias. The number of juveniles present also has some influence: as the maturation time is lengthened, N<sub>e</sub> increases.
The order Gruiformes, for which even familial composition remains controversial, is perhaps the least well understood avia order from a phylogenetic perspective. The history of the systematics of the order is presented, and the ecological and biogeographi characteristics of its members are summarized. Using cladistic techniques, phylogenetic relationships among fossil and moder genera of the Gruiformes were estimated based on 381 primarily osteological characters; relationships among modern specie of Grues (Psophiidae, Aramidae, Gruidae, Heliornithidae and Rallidae) were assessed based on these characters augmented b 189 characters of the definitive integument. A strict consensus tree for 20,000 shortest trees compiled for the matrix o gruiform genera (length = 967, CI = 0.517) revealed a number of nodes common to the solution set, many of which were robus to bootstrapping and had substantial support (Bremer) indices. Robust nodes included those supporting: a sister relationshi between the Pedionomidae and Turnicidae; monophyly of the Gruiformes exclusive of the Pedionomidae and Turnicidae; a siste relationship between the Cariamidae and Phorusrhacoidea; a sister relationship between a clade comprising Eurypyga and Messelornis and one comprising Rhynochetos and Aptornis; monophyly of the Grues (Psophiidae, Aramidae, Gruidae, Heliornithidae and Rallidae); monophyly of a clade (Gruoidea) comprisin (in order of increasingly close relationship) Psophia, Aramus, Balearica and other Gruidae, with monophyly of each member in this series confirmed; a sister relationship between the Heliornithida and Rallidae; and monophyly of the Rallidae exclusive of Himantornis. Autapomorphic divergence was comparatively high for Pedionomus, Eurypyga, Psophia, Himantornis and Fulica; extreme autapomorphy, much of which is unique for the order, characterized the extinct, flightless Aptornis.
In the species–level analysis of modern Grues, special efforts were made to limit the analytical impacts of homoplasy relate to flightlessness in a number of rallid lineages. A strict consensus tree of 20,000 shortest trees compiled (length = 1232 CI = 0.463) confirmed the interfamilial relationships resolved in the ordinal analysis and established a number of other variably supported groups within the Rallidae. Groupings within the Rallidae included: monophyly of Rallidae exclusive o Himantornis and a clade comprising Porphyrio (including Notornis) and Porphyrula; a poorly resolved, basal group of genera including Gymnocrex, Habroptila, Eulabeornis, Aramides, Canirallus and Mentocrex; an intermediate grade comprising Anurolimnas, Amaurolimnas, and Rougetius; monophyly of two major subdivisions of remaining rallids, one comprising Rallina (paraphyletic), Rallicula, and Sarothrura, and the other comprising the apparently paraphyletic ‘long–billed’ rails (e.g. Pardirallus, Cyanolimnas, Rallus, Gallirallus and Cabalus and a variably resolved clade comprising ‘crakes’ (e.g. Atlantisia, Laterallus and Porzana, waterhens (Amaurornis), moorhens (Gallinula and allied genera) and coots (Fulica). Relationships among ‘crakes’ remain poorly resolved; Laterallus may be paraphyletic, and Porzana is evidently polyphyletic and poses substantial challenges for reconciliation with current taxonomy. Relationships amon the species of waterhens, moorhens and coots, however, were comparatively well resolved, and exhaustive, fine–scale analyse of several genera (Grus, Porphyrio, Aramides, Rallus, Laterallus and Fulica) and species complexes (Porphyrio porphyrio –group,Gallirallus philippensis –group and Fulica americana –group) revealed additional topological likelihoods. Many nodes shared by a majority of the shortest trees under equal weightin were common to all shortest trees found following one or two iterations of successive weighting of characters. Provisiona placements of selected subfossil rallids (e.g. Diaphorapteryx, Aphanapteryx and Capellirallus ) were based on separate heuristic searches using the strict consensus tree for modern rallids as a backbone constraint.
These analyses were considered with respect to assessments of robustness, homoplasy related to flightlessness, challenge and importance of fossils in cladistic analysis, previously published studies and biogeography, and an annotated phylogeneti classification of the Gruiformes is proposed.
A framework for risk assessment. A probabilistic framework. Causes of Extinction. Summary. White rhinoceros on Ndumu. Formulating a birth-and death model. Parameters and initial condition. The deterministic prediction. Adding demographic stochasticity. Introducing a population ceiling. Removing constant numbers. Environmental variation. Risk Assessment. Summary. Useful methods when data are scarce. The Exonential model for population growth. Density dependence, the logistic equation and magpie geese. Other forms of density dependence. A model for suburban shrews. More about unstructured models. Summary. Structured populations. Age structure. The Leslie matrix. Stage structure. Simulating variability. Correlation and authocorrelation. Migration and dispersal. Density and dependence. Conclusion. Summary. Spatial structure and metapopulation dynamics. Conservation of spatial structure. Occupancy models. Population dynamic model. Summary. Conservation genetics. Consequences of loss of genetic diversity. Drift, risk and genetic diversity. The effects of inbreeding on population dynamics. Stochastic model for Banksia Cunteata. The genetics of metapopulations. Summary. Extensions of risk assessment. Appendices. Reference. Index. Conclusions. Random numbers. Random events and correlated random numbers. More about sensitivity analysis. References. Index.
Three different methods (visual detection on transects, call-playback and territory mapping) were used to estimate the densities of the White-breasted Mesite M. variegata in W Malagasy deciduous forest. The species is threatened and belongs to an endemic family of uncertain affinities. The population in the Menabe region, Madagascar, surveyed using call-playback is estimated at 3 000-19 000 individuals; that of Ankarafantsika, NW Madagascar, 6 000-26 000 individuals. The white-breasted mesite occurs at highest densities and with highest productivity in logged forest near rivers in the S of its range and in undisturbed sand-forest in the north, and is present at low density or absent from some areas of apparently suitable habitat, as well as forest that is secondary or has been severely damaged by burning. It is probably not immediately at risk from rats, dogs or selective exploitation, but hunting and forest burning through accidental bushfires or clearance for agriculture are locally important threats. -Author
The classification of species with respect to their conservation status using the IUCN criteria is an important process in many countries, providing a guide for setting conservation priorities. Recent advances have resulted in several approaches to dealing with uncertainty in data used to classify species. These methods demand an unambiguous and transparent logical structure for the criteria. We suggest some changes to the ways in which the criteria are represented that correct an unnecessary inconsistency and which may serve to avoid important errors when uncertainty in the data is considered explicitly.
The last flightless bird of the western Indian Ocean, Dryolimnas cuvieri aldabranus survives only on Aldabra. Its population numbered some 8,000 in 1973–1976. Surveys suggest numbers remained roughly constant between 1968 and 1988 (with a fluctuation of only 4% in responses to call playback between 1983 and 1988), but distribution continued to contract. Longevity can reach over 8.5 years (but is probably lower on average), and some birds remain within 100 m of the site of ringing for at least five years. Feral predators remain a threat, and captive populations are recommended. The monitoring procedure may have value for other Gruiformes.
The effective size (N(c)) of a population can be estimated from demographic information. We evaluated a recent model, showing that N(c) depends strongly on the relationship between age at reproductive maturity (M) and average adult lifespan (A). N(c) converges on half the number of potentially reproducing adults (N/2) as M decreases relative to A, but it increases linearly as M increases for a given value of A. Therefore, convergrence of N(c) on N/2 is more likely in organisms with a short sexual maturation period scaled to adult lifespan. To assess the generality of this convergence we asked whether most organisms are characterized by this requisite relationship between M and A. The dimensionless number M/A is approximately invariant within taxa, but it is markedly different across taxa. Previous work focused on birds and mammals, taxa with unusually small M/A (0.4 and 0.75). Other animal taxa take longer than most birds and mammals to reach maturity for a given reproductive lifespan, so they are characterized by larger M/A (e.g., fish, 2.0). In theory, these taxon- specific life histories strongly influence N(c). We conclude that N(c) is expected to approach N/2, provided that M/A is (unusually) small, and that N(c)/N among poikilotherms may often exceed that of mammals and especially birds.
Australian state and federal agencies use a broad range of methods for setting conservation priorities for species at risk. Some of these are based on rule sets developed by the International Union for the Conservation ofNature, while others use point scoring protocols to assess threat. All of them ignore uncertainty in the data. In this study, we assessed the conservation status of 29 threatened vascular plants from Tasmania and New South Wales using a variety of methods including point scoring and rule-based approaches. In addition, several methods for dealing with uncertainty in the data were applied to each of the prioritysetting schemes. The results indicatethat the choice of a protocol for setting priorities and the choice of the way in which uncertainty is treated may make important differences to the resulting assessments of risk. The choice among methods needs to be rationalized within the management context in which it is to be applied. These methods are not a substitute for more formal risk assessment.
Subdesert mesites produced ve distinct types of vocal element which they combined to produce two broad classes of song 'syllable'. One of these syllables was exclusive to males and the other was mainly given by females. Song syllables were either produced in series by single individuals to give solo songs, or 2-5 ve birds vocalised simultaneously with varying degrees of temporal precision to give duets and choruses. Pair-duets were the most common and male solos the least common form of song recorded. Females initiated and terminated signi cantly more songs than males and male syllables followed female syllables more promptly than the converse. However, the syllable structure of male and female solos changed when synchronised to form pair-duets indicating that, in contrast to most previous studies of duetting species, these songs are a function of both male and female behaviour. Only a subset of each group contributedto duets and choruses and participationwas positively correlated with mass for males and females both within and across groups. Song activity remained at a low but relatively constant rate throughout both the day and season. The wide variety of contexts in which songs were produced indicated that they serve multiple functions: some appear to be cooperative endeavours (e.g. to maintain contact in dense vegetation and 2) I am indebted to the Ministry of Water and Forest (Antananarivo) for granting me permission to conduct research in Madagascar, and to Parc Botanique et Zoologique de Tsimbazaza and Projet ZICOMA (BirdLife International) for their support of the project. I am particularly grateful to Joe Tobias, Stuart Butchart, Lucy Odling-Smee and Julien Ramanampamonjy for their ideas and invaluable help in the eld. My sincere thanks also go to Nick Davies for his advice and support, and to Michelle Hall and an anonymous referee for comments that helped improve this paper.
The World Conservation Union (IUCN) defined a set of categories for conservation status supported by decision rules based on thresholds of parameters such as distributional range, population size, population history, and risk of extinction. These rules have received international acceptance and have become one of the most important decision tools in conservation biology because of their wide applicability, objectivity, and simplicity of use. The input data for these rules are often estimated with considerable uncertainty due to measurement error, natural variation, and vagueness in definitions of parameters used in the rules. Currently, no specific guidelines exist for dealing with uncertainty. Interpretation of uncertain data by different assessors may lead to inconsistent classifications because attitudes toward uncertainty and risk may have an important influence on the classification of threatened species. We propose a method of dealing with uncertainty that can be applied to the current IUCN criteria without altering the rules, thresholds, or intent of these criteria. Our method propagates the uncertainty in the input parameters and assigns the evaluated species either to a single category (as the current criteria do) or to a range of plausible categories, depending on the nature and extent of uncertainties.
Accurate estimation of effective population size is important in attempts to conserve small populations of animals or plants. We review the genetic and ecological methods that have been used to estimate effective population size in the past and suggest that, while genetic methods may often be appropriate for the estimation of Ne, and its monitoring, ecological methods have the advantage of providing data that can help predict the effect of a changed environment on Ne. Estimation of Ne, is particularly complex in populations with overlapping generations, and we summarize previous empirical estimates of Ne that used ecological methods in such populations. Since it is often difficult to assess what parameters and assumptions have been used in previous calculations, we suggest a method that provides a good estimate of Ne, makes clear what assumptions are involved, and yet requires a minimum of information. The method is used to analyze data from 14 studies. In 36% (5) of these studies, our estimate is in excellent agreement with the original, and yet we use significantly less information, in 21% (3) the original estimate is markedly lower, in 43% (6) it is markedly higher. Reasons for the discrepancies are suggested. Two of the underestimates involve a failure in the original to account for a long maturation time, and four of life overestimates involve problems in the original with the correction for overlapping generations.
With recently derived algorithms, it is possible to calculate the relative phylogenetic distinctiveness of taxa with respect to patterns of phylogenetic branching. We extended this approach by exploring the relative extent to which taxa represent phenotypic biodiversity. We devised a method, based on the use of independent contrasts, that measures the amount of phenotypic change that occurs when lineages diverge. We use this method to quantify the extent to which a taxon represents the phenotypic diversification that has occurred in the past. We applied our method to an analysis of variation in clutch size across 133 avian families. All families did not contribute equally to representing clutch size diversification. The top 10 avian families in terms of representing clutch size diversification were the mesites ( Mesitornithidae), cranes (Gruidae), bustards (Otidae), new world quail (Odontophoridae), seriemas (Cariamidae), finfoots ( Heliornithidae), swallows ( Hirundinidae), megapodes ( Megapodiae), and guans (Cracidae). The 217 species in these 10 families (2.3% of all bird species, 7.5% of families) represented 19.3% of diversification in clutch size. Seventeen percent of overall clutch size diversification was represented by taxa threatened with extinction. The 10 families that represent the greatest proportion of overall clutch size diversification threatened by extinction were the mesites ( Mesitornithidae), kagu ( Rhynochetidae), cranes (Gruidae), kiwis (Apterygidae), new world quail (Odontophoridae), megapodes ( Megapodiae), cassowaries (Casuariidae), finfoots ( Heliornithidae), guans (Cracidae), and logrunners (Orthonychidae). The 42 threatened species (0.5% of all bird species, 3.8% of all threatened bird species) in these 10 families encompassed 53% of the clutch size diversification whose representation was threatened with extinction. Our results suggest that this type of analysis could potentially help prioritize species-based conservation efforts by identifying those taxa that contribute most toward representing the evolutionary processes that lead to current phenotypic biodiversity.
Resumen: Con algoritmos recientemente calculados es posible estimar el grado de distinción filogenética de taxones con respecto a patrones de ramificación filogenética. Extendimos esta estrategia al explorar el grado relativo al cual los taxones representan a la biodiversidad fenotípica. Diseñamos un método basado en el uso de contrastes independientes que mide la cantidad de cambio fenotípico que ocurre cuando los linajes se bifurcan. Utilizamos este método para cuantificar el grado al que un taxón representa la diversificación fenotípica que ha ocurrido en el pasado. Aplicamos nuestro método a un análisis de variación en el tamaño de nidada en 133 familias de aves. No todas las familias contribuyeron de igual manera a la representación de la diversificación del tamaño de nidada. Las principales 10 familias de aves, en cuanto a la representación de la diversificación del tamaño de la nidada fueron los monias ( Mesitornithidae), grullas (Gruidae), avutardas (Otidae), perdices del nuevo mundo (Odontophoridae), cariamas (Cariamidae), pájaros cantil (Heliornithidae), golondrinas ( Hirundinidae), megápodos ( Megapodiae) y pavones (Cracidae). Las 217 especies en estas 10 familias (2.3% de todas las especies de aves, 7.5% de las familias) representaron el 19.3% de la diversificación del tamaño de nidada. El diecisiete por ciento de la diversificación total del tamaño de nidada estuvo representado por taxones amenazados de extinción. Las 10 familias que representan la mayor proporción de la diversificación total del tamaño de nidada amenazadas de extinción fueron los monias (Mesitornithidae), kagu ( Rhynochetidae), grullas (Gruidae), kiwis (Apterygidae), perdices del nuevo mundo (Odontophoridae), megápodos ( Megapodiae), casuarios (Casuariidae), pájaros cantil ( Heliornithidae), pavones (Cracidae) y log-runners (Orthonychidae). Las 42 especies amenazadas (0.5% de todas las especies de aves, 3.8% de todas las especies de aves amenazadas) dentro de estas 10 familias abarcaron el 53% de la diversificación del tamaño de nidada, cuya representación estuvo amenazada por la extinción. Nuestros resultados sugieren que este tipo de análisis podría potencialmente ayudar a priorizar los esfuerzos de conservación basados en especies al identificar aquellos taxones que más contribuyan a la representación de los procesos evolutivos que conduzcan a la biodiversidad fenotípica actual.
Conservation biologists and natural resource managers are both working to maintain species, but their approaches and priorities differ. The contrast was highlighted when the World Conservation Union (IUCN) listed some commercial fish species, such as the Atlantic cod (Gadus morhua), in the 1996 Red List of Threatened Animals. These species qualified under IUCN’s criteria because they had undergone a marked decline in abundance. Disagreements over these listings revealed fundamental differences between resource managers and conservation biologists. Resource managers aiming to maximize continuing yields using specific, explicit, and data-rich models, generally have not considered risk assessment and sometimes face the necessity for political compromises. Conservation biologists generally consider a wide diversity of species and operate in a data-poor and precautionary context with an overall aim of minimizing extinction risk. The IUCN Red List is an extreme case in point and uses simple criteria for evaluating the conservation status of all species. Under these circumstances, it can do little more than indicate a species’ status in order to prompt further investigation by the appropriate body. We suggest that productive collaboration between conservation biologists and resource managers will start with an understanding of these different perspectives and will benefit from common interests in precautionary approaches, ecosystem approaches, and adaptive management studies.
In 1997–2000 we studied a population of Subdesert Mesites Monias benschi consisting of 35–68 adults comprising 32 groups of two to nine birds (modal group size of four). The study population was significantly male-biased in 1999 but not in 1997 or 1998. Overall, both sexes were philopatric, but when dispersal (or eviction) occurred, it appeared to be female-biased. Over 40% of groups contained more than two adult males, whilst < 15% contained more than two adult females. Whilst there was no evidence of behavioural dominance by females, intrasexual aggression within groups was observed only amongst females. In contrast to other birds occupying the same habitat, breeding in mesites was not tied to rainfall, and occurred throughout the year. Each breeding unit constructed several nests every year, only one of which was used. All adult males and at least one adult female co-operated to raise one or two clutches of one or two eggs per year. Males and females contributed equally to incubation. Chick production and chick survival were not related to group size or territory size. Groups defended large, permanent, and multipurpose territories and all group members contributed to territory defence. Territory size was positively correlated with the number of males in groups, but not with overall group size. Territories were tightly packed with very few areas unoccupied. Transect surveys conducted throughout the narrow geographical range of this species revealed its presence in a range of semi-arid habitat types. Small groups were more likely to be detected in intact, high-stature forest, whilst large groups were more likely to be detected in low-stature forest containing numerous spiny, xerophytic trees Didierea madagascariensis.
The dry forests constitute one of the most distinct, yet least protected, ecosystems in Madagascar, an island renowned for high levels of endemism. They generally have been considered one of the most intact of Madagascar's climax vegetation types and accordingly have received little conservation effort. In particular, the Mikea Forest, a unique area between the Mangoky and Fiherenana rivers, currently receives negligible formal protection. It contains remarkably diverse plant and reptile assemblages, including several taxa that are found nowhere else, plus the only populations of two threatened bird species: the subdesert mesite Monias benschi and long-tailed ground-roller Uratelornis chimaera. From satellite imagery we estimate that primary forest cover declined by 15.6 per cent from 1962 to 1999, and that the rate of deforestation has increased from 0.35 per cent per annum in 1962–94 to 0.93 per cent per annum over the past 5 years. The most important factors underlying this process are slash-and-burn maize cultivation in the northern Mikea Forest and charcoal production at its southern fringe. Given these alarming circumstances, we suggest that combinations of conservation measures are required to safeguard the biological diversity of the area. Specifically, we recommend the establishment of a large protected area to the north of Manombo, a coordinated network of community-based conservation areas throughout the Mikea Forest, development projects to improve agriculture, and a regional research and education centre.
Politicians and scientists alike now agree that a priority list of global centres for preservationof biological diversity is required. Diversity has generally been measured only in terms of species richness, or in the form of indices combining richness with abundance. Such measures are considered inadequate for the task in hand. A novel index, based on the information content of cladistic classifications and giving a measure of taxonomic distinctness, is introduced. This taxic diversity measure, when coupled with detailed knowledge of distribution, can be used in modified analyses of the type previously developed as ‘critical faunas analysis’ or ‘network analysis’. Central to all such analyses is the concept of complementarity of floras or faunas. By employing complementariry, step-wise procedures can identify optimally efficient, single-site sequences of priority areas for a group, taking existing reserves into account or not, as required. For practical planning it is concluded that two basic rounds of analysis are required: first, recognition of global priority areas by taxic diversity techniques; secondly, within any such area, analysis without taxic weighting (as being developed by Margules and his co-workers) to identify a network of reserves to contain all local taxa and ecosystems. The paper concludes with a brief discussion of some immediate prospects for development of a systematic approach to global conservation evaluation.
There has been a recent interest in integrating an understanding of behaviour into conservation biology. Unfortunately, there has been no paradigm for such a process. Without a clear framework for integration, conservation biologists may have difficulties recognising how behavioural knowledge can help solve real-world conservation problems. Effective population size (Ne) is a key demographic parameter used to understand population viability. A variety of behaviours and behavioural traits impact Ne, yet their importance for conservation is under-appreciated. We suggest that identifying behavioural traits that affect Ne provides a paradigm for integrating behavioural biology into conservation biology. Behaviour can affect Ne through at least three different mechanisms: reducing N — the population size; reducing r — the population growth rate, and/or by increasing reproductive skew. We discuss how nine common behavioural traits can reduce Ne, and suggest how an understanding of these traits may inform management of both free-living and captive animals.
The classification of endangered species uses categories “extinct in the wild”, “endangered” and so on that are intrinsically vague. This vagueness presents various problems for those trying to classify species. The usual way of dealing with this vagueness is to eliminate it by providing precise definitions of the categories in question. In this paper we propose a fuzzy set-theoretic alternative that respects the inherent vagueness of the crucial categories without compromising the utility of the classification scheme. Moreover, we argue that it leads to intuitively more appropriate classifications in many cases.