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1.
Large hydroelectric dams are one of the current drivers of habitat loss across Amazonian forests. We investigated how the primate community at a hydroelectric dam in Brazilian Amazonia responded to changes in the landscape and local habitat structure of land‐bridge islands after 21 yr of post‐isolation history. The Balbina Dam, constructed in 1986, inundated 3129 km2 of primary forests and created more than 3500 variable‐sized islands. We conducted primate and habitat structure surveys on 20 islands from 5 to 1815 ha, and extracted forest patch and landscape metrics for each island. The number of primate species per island varied between 0 and 7 species. Primate composition varied substantially according to both island area and forest cover remaining within the landscape, whereas island area alone was the most significant predictor of richness. Locally, tree density and vertical stratification were the most significant explanatory variables of primate composition and richness. A model containing area effects had the most explanatory power regarding site occupancy for most species. Individually, each species responded differently, with howler and brown capuchin monkeys showing greater tolerance to cope with habitat changes. Body size was also an important predictor of primate occupancy. We recommend protecting large fragments and enhancing the suitability of surrounding habitats to ensure primate conservation in most Neotropical fragmented landscapes. Given the flat topography of hydroelectric reservoirs, which mainly favors the formation of small islands, and the escalating hydropower development plans in Amazonia, our findings provide evidence for pervasive detrimental impacts of dams on primate communities. 相似文献
2.
Habitat restoration strategies for fragmented high Andean forest landscapes must consider the influence of within‐patch habitat quality on bird abundance. I examined vegetation and bird abundance at three locations within a highly fragmented Polylepis forest landscape in the Cordillera Vilcanota, southern Peru. Across the landscape, there was significant variation in the vegetation structure of Polylepis forest patches of different size categories, especially in terms of tree girth, tree height, tree density, and canopy vegetation structure. Principal Component Analysis extracted five factors of habitat quality, which together accounted for 74.2% of the variability within 15 habitat variables. Polylepis bird species differed in their responses to habitat quality but, overall, variation in Polylepis bird abundance was not fully captured by the range of habitat quality variables. Tall, dense vegetation cover was clearly important for 11 conservation‐important species, a high density of large trees was important for 10 species and primary forest ground cover was important for eight species. Habitat quality exhibited no significant influence on the abundance of only one species –Asthenes urubambensis. The abundance of seven species was associated with lower elevation forest, but only one species was associated with higher elevation forest. Management of habitat quality in large and medium remnant forest patches throughout the Cordillera Vilcanota, particularly in the 3800–4200 m elevation range, will be a cornerstone in ensuring the persistence of the majority of conservation‐important bird species populations. 相似文献
3.
Todd Keeler-Wolf 《Oecologia》1986,70(2):309-317
Summary The Barred Antshrike (Thamnophilus doliatus) is the most abundant insectivorous foliage-gleaning vertebrate in both closed rain forest and second growth on the island of Tobago. However, it occurs only in second growth on the larger neighbor island of Trinidad and on the neotropical mainland.Habitat niche expansion into Tobago forest has been facilitated by several behavioral traits which set the antshrike apart from other foliage-gleaners of forest and second growth on Tobago. The antshrike captures a higher diversity of foliage, branch & trunk, and terrestrial arthropods. It forages over a wider range of heights and under a wider variety of crown cover situations than any of its closest ecological counterparts on Tobago. The antshrike also takes a wider range of prey sizes and regularly uses additional food sources, including fruit and ants, not taken by other guild members. The broad foraging niche of the antshrike enables it to breed during many times of the year when other narrower-niched foliage-gleaners do not.On Trinidad, although the most common foliagegleaner in second growth, the antshrike was not observed in adjacent closed rain forest. Several facts suggest that diffuse competition may be excluding antshrikes from Trinidad forest: 1) a general pattern of rarity or absence in other parts of its range where there are more guild members; 2) more species and individuals of foliagegleaners with an overall higher biomass in Trinidad forest than in Tobago forest; 3) foliage arthropod resources are significantly (1.7x) lower in Trinidad forest than Tobago forest, suggesting that Trinidad forest guild members may be depressing the quantity of important resources for antshrikes; and 4) Trinidad forest species with the highest foraging similarity to antshrikes have a greater precentage of prey captures comprised of relatively specialized attack behaviors than do Tobago forest antshrikes.Foraging generalists like the Barred Antshrike appear to expand or contract their habitat niches depending upon the number of ecologically similar species in a given habitat. They may occur in high densities in habitats typically foreign to them provided competitors are few and there is sufficient food to supply their catholic requirements. 相似文献
4.
We report the results of a census of Indri indri conducted in Betampona Nature Reserve, a lowland rain forest in eastern Madagascar. In addition, we conducted a year-long study of the ranging behavior of 3 groups in the southwestern region of the reserve. We used 2 methods to calculate population density and home range size, and to provide minimum and maximum estimates. Population density of Indri indri ranged from 6.9–13.2 individuals/km2 in Betampona. Mean home range size is 27 ha. The values for population density and home range size are intermediate between values for Indri indri in selectively logged and undisturbed montane rain forest. Our results suggest a relationship between habitat disturbance, population density and home range size for the species. Recent increases in habitat disturbance appear to cause an increase in population density and a decrease in home range size. The results are consistent with ones for other folivorous primate populations. Further research on habitat requirements of Indri and availability in Betampona is necessary to investigate the possibility of translocating Indri from nearby forest fragments into Betampona. 相似文献
5.
Warner MD 《Primates; journal of primatology》2002,43(1):59-71
This study aims to ascertain habitat utilization, in relation to forest structural variation, by a multi-species group of
primates in tropical lowland rainforest in Southeast Peru during dry season. A new approach to assessing habitat utilization
was used. Habitat variation was described by structural and indicator variables collected in quadrats along transects through
a study area within Terra Firme and Floodplain forest. Variables were grouped into ‘factors’ accounting for most of the variation
by means of a Principal Components Analysis (PCA). Presence or absence of the primates within the quadrats, assessed by repeat
transect surveys, was taken to indicate habitat preferences. Discrimination between the habitat and forest structure in areas
of primate presence as opposed to absence was carried out by means of Discriminant Function Analysis (DFA). This highlighted
patterns in most utilized habitat. Vertical utilization of the forest was also assessed along with presence in bamboo and
general activity on encounter. Suggestions of habitat preference and utilization are made for each of the six sympatric species
studied, based on significantly discriminating habitat factors, vertical stratification on encounter and relationships with
bamboo.Saguinus fuscicollis andCebus moloch appeared as habitat generalists.Cebus apella, Saimiri sciureus, andAotus spp., exhibited varying degrees of preference for habitat factors suggesting disturbed forest,Cebus albifrons was more generalistic but with a possible association with primary, naturally disturbed forest.C. appella was encountered in Terra Firme forest significantly more than in Floodplain. ForS. sciureus, C. moloch, andC. apella, upper understory was the most utilized forest layer, forC. albifrons, middle canopy and forS. sciureus andAotus spp., lower understory. Both positive and negative relationships with bamboo were highlighted. Significant positive relationships
betweenAotus spp., and bamboo suggest dense bamboo stands provide important daytime resting sites for this nocturnal species.C. moloch was also shown to utilize bamboo whereasS. fuscicollis appeared to actively avoid it. High levels of conformity with past studies in terms of habitat utilization patterns described
for the species studied supports the conclusion that the methods used in this study provide an effective means of assessing
primate habitat utilization within complex habitat. 相似文献
6.
Conservation of wildlife populations requires extensive knowledge of their habitat requirements, efficient methods to evaluate habitat quality, and an understanding of the value of fragments and edges. Kibale National Park, Uganda has areas that differ in the densities of 2 species of frugivorous monkeys—Cercopithecus mitis and Lophocebus albigena—including one on an edge and forest fragments outside the park that lack both species. We compared the basal area densities of important food trees with primate densities. The density of Cercopithecus mitis correlates most strongly with the basal area density of all types of food trees combined. The density of Lophocebus albigena does not correlate with the basal area densities of any category of food trees or with fruit availability. An index of their density—number of groups seen per km walked—correlates to fruit availability but with marginal significance. Lack of a relationship between the basal area densities of food trees and density of Lophocebus albigena may be the result of a mismatch in scale between the forest area measured and their large home ranges. We compared the unused area of forest to the other areas of the forest and the fragments and found it had higher basal area densities in all food tree categories for both species than the fragments and lower basal area densities of most categories than the other parts of the forest, indicating that the fragments are poor quality and would probably be unused even if dispersal were likely. 相似文献
7.
We analyzed the spatial distributions of two congeneric tree species, Neolistea aciculata and Neolistea sericea (Lauraceae), in a warm‐temperate forest on Miyajima Island, south‐western Japan. Both species were mainly found in valley sites on the island. Hence, these species shared the same topographic habitat niche. However, we found a clear difference between the spatial distributions of the two species in relation to the light environment. Neolistea aciculata was predominantly found in stands with low light, such as beneath the canopy of dense evergreen broadleaved forest. In contrast, N. sericea was predominantly associated with ample light, such as in secondary Pinus densiflora forest. In stands with moderate light conditions, both species were found. This habitat niche segregation in relation to light conditions presumably allows the coexistence of these two species in the predominantly successional forest on Miyajima Island. 相似文献
8.
Habitat structure and anthropogenic disturbance are known to affect primate diversity and abundance. However, researchers
have focused on lowland rain forests, whereas endangered deciduous forests have been neglected. We aimed to investigate the
relationships between primate diversity and abundance and habitat parameters in 10 deciduous forest fragments southeast of
Santa Cruz, Bolivia. We obtained primate data via line-transect surveys and visual and acoustic observations. In addition,
we assessed the vegetation structure (canopy height, understory density), size, isolation time, and surrounding forest area
of the fragments. We interpreted our results in the context of the historical distribution data for primates in the area before
fragmentation and interviews with local people. We detected 5 of the 8 historically observed primate species: Alouatta caraya, Aotus azarae boliviensis, Callithrix melanura, Callicebus donacophilus, and Cebus libidinosus juruanus. Total species number and detection rates decreased with understory density. Detection rates also negatively correlated with
forest areas in the surroundings of a fragment, which may be due to variables not assessed, i.e., fragment shape, distance
to nearest town. Observations for Alouatta and Aotus were too few to conduct further statistics. Cebus and Callicebus were present in 90% and 70% of the sites, respectively, and their density did not correlate with any of the habitat variables
assessed, signaling high ecological plasticity and adaptability to anthropogenic impact in these species. Detections of Callithrix were higher in areas with low forest strata. Our study provides baseline data for future fragmentation studies in Neotropical
dry deciduous forests and sets a base for specific conservation measures. 相似文献
9.
Ross L. Goldingay Darren G. Quin Orlando Talamo Janice Mentiplay‐Smith 《Ecological Management & Restoration》2020,21(2):131-142
Habitat preferences need to be understood if species are to be adequately managed or conserved. Habitat preferences are presumed to reflect requirements for food, shelter and breeding, as well as interactions with predators and competitors. However, one or more of these requirements may dominate. Tree‐cavity‐dependent wildlife species are one example where shelter or breeding site requirements may dominate. We installed 120 nest boxes across 40 sites to target the vulnerable Brush‐tailed Phascogale (Phascogale tapoatafa) and the non‐threatened Sugar Glider (Petaurus breviceps). The provision of shelter sites where few of quality are available may enable better resolution of habitat preferences. Over three years, we observed the Brush‐tailed Phascogale at 17 sites, whereas the Sugar Glider was observed at 39 sites. We tested four broad hypotheses (H1–H4) relating to habitat that may influence occupancy by these species. There was no influence of hollow (cavity) abundance (H1) on either species suggesting our nest boxes had satisfied their shelter requirements. There was no influence of habitat structure (canopy and tree proximity) (H2) immediately around the nest box trees. We found no influence of distance to the forest edge (H3). Variables at and away from the nest box site that appear to reflect foraging substrates (H4) were influential on the Brush‐tailed Phascogale. Sugar Glider occupancy was only influenced by a single variable at the nest box site. The lack of influence of any other variables is consistent with the very high occupancy observed, suggesting most of the forest habitat is suitable when shelter sites are available. We found no evidence that the Sugar Glider reduced site use by the Brush‐tailed Phascogale. 相似文献
10.
Antonio Rossano Mendes Pontes 《International journal of primatology》1997,18(2):131-157
I studied a primate community on a tropical rainforest island, in the northernmost area of the Brazilian Amazonia. While walking through six distinct habitats along a 12-km trail, running toward the center of the island—a remote undisturbed area—I collected data on the use of the different forest types and forest strata by the primate community and the formation of either mixed groups or species assemblages. Five species are present: Cebus olivaceus, C. apella, Saimiri sciureus, Ateles belzubuth, and Alouatta seniculus. They seemed to be habitat generalists, using most habitat types. The five species used the higher strata more significantly, probably because Maracá does not present well-defined forest floors, which could be a result of being located in the transition between the great areas of savannah and the Amazonian seasonally dry forests. The five species all formed some polyspecific associations, which involved sharing the available food resource. Mixed groups were significantly more frequent and therefore possibly more important to Saimiri, which was not the case in relation to the other four species. Assemblages, defined as the presence in the same clumped resource, without coordinated activity, of 3 primate species, were recorded primarily in fruiting fig trees. I suggest that assemblages are impelled by food constraints, forcing cofeeding in large seasonal resources, highlighting the ecological importance of figs to these primates. Linear regression models show that the number of feeding bouts in each habitat type is positively related to the number of fruiting trees exploited, but the density of these fruit trees, diversity of plant species, tree height, and total basal area of each habitat type have no relationship to feeding. 相似文献
11.
Julián G. Mangas Jorge Lozano Sara Cabezas-Díaz Emilio Virgós 《Biodiversity and Conservation》2008,17(1):43-51
Carnivores are umbrella species with a key role in ecosystems. In the Mediterranean, they face with several conservation problems,
mainly habitat loss or transformation. In this region, scrubland habitats are considered of minor conservation relevance as
compared to mature forest formations. Conservation of scrublands in Mediterranean ecosystems is also difficult because to
control fires, they are removed over large areas. For carnivores, scrublands may be essential to guarantee shelter and food.
Here, we analyzed the importance of scrublands and other habitat variables in determining the richness of medium-sized carnivores
in a typical Mediterranean area of central Spain (Monfragüe Natural Park). The Park was divided into plots of 2 × 2 km (n = 30). In each plot, a 2 km-length survey route was walked searching for carnivore scats. We recorded the number of species
of carnivores and we related this value to several habitat variables. Habitat variables were summarized by means of Principal
Component Analysis (PCA). Habitat models were developed by, using multiple regression models, including PCA factors and the
habitat type as predictors. The only variable included in the final model was the first PCA factor. Carnivore richness was
positively associated with large tree, shrub, and rock cover areas, which is the typical habitat structure of scrublands.
This habitat offers the best available area for shelter and may be considered as a key element for carnivore conservation
in the Mediterranean region. To reconciliate carnivore conservation and forestry management, we proposed small-scale clearances
as a management alternative to typical large scrubland removals. 相似文献
12.
On humans and wildlife in Mediterranean islands 总被引:1,自引:1,他引:0
Jacques Blondel 《Journal of Biogeography》2008,35(3):509-518
Aim To investigate the effects of human‐induced landscape changes in Mediterranean islands on the ecological and evolutionary responses of bird communities and populations. The combination of mass extinction of large mammals and massive deforestation by humans was hypothesized to produce new selection regimes to which organisms were likely to respond. Habitat selection and niche breadth have been investigated at the scale of species, and phenotypic variation at the scale of local populations. Location The study was carried out along habitat gradients and in habitat mosaics at different spatial scales on the island of Corsica and in areas of similar size and structure in continental France. Methods Two sets of gradients have been used for investigating habitat selection and niche breadth: gradients of altitude, and gradients of vegetation structure. Population studies focused on the blue tit, Cyanistes caeruleus. Large samples of breeding attempts by this species in 10 habitats provided detailed data on phenotypic variation of fitness‐related traits both on Corsica and on the mainland. Results The extent of niche space used by birds differed substantially depending on which habitat gradient was considered. Many species have been found to contract their habitat niche along the elevation gradient on Corsica compared with the mainland, whereas all species in the vegetation gradient broadened their niche on the island. Breeding patterns of the blue tit differed considerably depending on whether they settle in deciduous oaks (Quercus humilis) or in evergreen sclerophyllous oaks (Quercus ilex). Phenotypic variation of breeding traits was much higher on the island, where more populations were correctly timed for the best breeding period than on the mainland, a pattern that is likely to result from lower dispersal of organisms on the island. Main conclusions The differences in observed niche breadth between the two series of habitat gradients is explained both by the species‐specific ecology of the species and the human‐induced environmental history of Corsica. Large‐scale landscape changes provided new opportunities for island colonization by non‐forest species, which are isolated as small, ‘fugitive’ local populations. In both gradients, forest species that are typical components of the Corsican bird fauna definitely expanded their niche and occupied a wider range of habitats on Corsica than on the mainland. At the population scale, landscapes included habitat patches with contrasted selection regimes, which resulted in high phenotypic variation for many fitness‐related traits. Reduced dispersal of birds on the island resulted in a much higher degree of local differentiation on Corsica than on the mainland. 相似文献
13.
Aim Evolutionary theory predicts that levels of genetic variation in island populations will be positively correlated with island area and negatively correlated with island isolation. These patterns have been empirically established for oceanic islands, but little is known about the determinants of variation on habitat islands. The goals of this study were twofold. Our first aim was to test whether published patterns of genetic variation in mammals occurring on montane habitat islands in the American Southwest conformed to expectations based on evolutionary theory. The second aim of this research was to develop simple heuristic models to predict changes in genetic variation that may occur in these populations as a result of reductions in available mountaintop habitat in response to global warming. Location Habitat islands of conifer forest on mountaintops in the American Southwest. Methods Relationships between island area and isolation with measures of allozyme variation in four species of small mammal, namely the least chipmunk (Tamias minimus), Colorado chipmunk (Tamias quadrivittatus), red squirrel (Tamiasciurus hudsonicus), and Mexican woodrat (Neotoma mexicana), were determined using correlation and regression techniques. Significant relationships between island area and genetic variation were used to develop three distinct statistical models with which to predict changes in genetic variation following reduction in insular habitat area arising from global warming. Results Patterns of genetic variation in each species conformed to evolutionary predictions. In general, island area was the most important determinant of heterozygosity, while island isolation was the most important determinant of polymorphism and allelic diversity. The heuristic models predicted widespread reductions in genetic variation, the extent of which depended on the population and model considered. Main conclusions The results support a generalized pattern of genetic variation for any species with an insular distribution, with reduced variation in smaller, more isolated populations. We predict widespread reductions in genetic variation in isolated populations of montane small mammals in the American Southwest as a result of global warming. We conclude that climate‐induced reductions in the various dimensions of genetic variation may increase the probability of population extinction in both the short and long term. 相似文献
14.
Remains of a large-bodied species of endemic nesomyid rodent, Macrotarsomys petteri Goodman and Soarimalala, 2005, were identified from subfossil deposits recovered from Andrahomana Cave in extreme southeastern Madagascar. This recently described extant species was previously only known from a single specimen collected at a site about 450 km northwest of Andrahomana and with distinctly different forest habitat than currently found in the vicinity of the cave. Radiocarbon dating of remains of M. petteri from the cave site indicates that it persisted in the region subsequent to human settlement. Previous reports of a large member of Macrotarsomys from other Quaternary sites in southern Madagascar are almost certainly of M. petteri. It is proposed that this species once had a broad distribution across the southern portion of the island during a more mesic period and subsequent aridification of the region has led to its local extirpation across most of its former range. To cite this article: S.M. Goodman et al., C. R. Palevol 5 (2006). 相似文献
15.
Irene Romero-Nájera Alfredo D. Cuarón Cristopher González-Baca 《Biodiversity and Conservation》2007,16(4):1183-1195
Species introductions are among the most pervasive types of disturbance, seriously affecting island biota and ecosystem dynamics.
The management of introduced generalist species, which may live in a wide range of environmental conditions, can be particularly
difficult and is a major challenge for the conservation of native insular species. Boa constrictor was introduced onto Cozumel Island, Mexico, in 1971. The introduction of this generalist predator has affected negatively
the native species (many of them endemic to the island) on which the boa feed. It is important to determine temporal variation
in boa abundance, the areas of the island in which boas live, and the vegetation types they use in order to develop management
strategies to reduce boa pressure on the native biota. We used nocturnal road transect sampling and occasional boa encounters
during field work, to estimate boa distribution, abundance and habitat use, taking into account its spatiotemporal patterns
on Cozumel Island. This study confirms that Boa constrictor is well established, widespread, and abundant on the island. Our results show that boas are distributed throughout Cozumel,
in all vegetation types and geographical regions. Overall, there were 0.11 ± 0.03 boa/10 km road transect. There were no
significant spatiotemporal differences in boa activity (time of day) and abundance (monthly, seasonally, by vegetation types
or regions of the island). According to the habitat use analysis, there were, however, fewer boas than expected in the subdeciduous
tropical forest we sampled and in the central-northern region of the island, which coincide with areas inhabited by humans.
There were more boas in areas uninhabited by humans, and there was a tendency towards a greater proportion of dead boas in
inhabited areas and live boas in uninhabited areas. Cozumel boas are habitat generalists, which are affected by human induced
mortality in inhabited areas. There is a vast area uninhabited by humans, with natural vegetation, on the island where boas
have suitable habitats available for their continuous existence on Cozumel. This situation, and the adaptability of the boa,
makes the control or eradication of this introduced species a critical conservation challenge. 相似文献
16.
Ramon Castelo 《Biodiversity and Conservation》1994,3(9):808-827
The present study on the fish fauna of Bioko reports a total of 43 species of 21 families; 18 of which are new records for the island. Bioko's icthyofauna is made up of 17 freshwater and 26 saltwater and brackish water species. Freshwater fishes are primarily restricted to a narrow belt along the north and west of the island, similar to the adjacent volcanic region around Mount Cameroon. The rest of the island, however, is inhabited by salt tolerant fishes, as found in São Tomé, Príncipe and Annobón. Fish communities also vary according to elevation since rivers on Bioko are characterized by steep gradients from source to sea. Pressures on Bioko's river systems are not alarmingly high but may increase in the future because of the use of toxic products (lime and insecticides) for fishing. There is no doubt that this is having a significant effect on northern and western rivers which are precisely the most species-rich. Aphyosemion oeseri, which is endemic to Bioko, and which has a distribution restricted to the small northern rivers is in great danger of extinction. P. monkei is in a similarly precarious situation, given that it is extremely rare and will probably disappear altogether in a few years from the island's rivers. Before the situation becomes irreversible urgent measures must be taken to improve matters through educational campaigns as well as through cleaning up heavily-polluted rivers and re-stocking them with fish species from neighbouring river basins. 相似文献
17.
18.
Understanding spatial variation in abundance is essential for forecasts of responses to environmental change impacts on diversity and the consequent conservation actions. However, few studies have sought to distinguish the causal basis of abundance structure and range limits. Here we do so for an invasive springtail species, Pogonognathellus flavescens, in a cold temperate island setting. Local microclimate variables and physiological tolerances of this habitat generalist suggest that it should be widely distributed across a range of habitats below 200 m elevation on the island. By contrast, island‐wide and local abundance surveys show that it is restricted to indigenous Poa cookii tussock grassland habitats in the southeast. Preference for this habitat is correlated with the presence of vertebrates and a threshold response to soil Ca and pH, with preference for low values of both. Habitat specificity may be the consequence of a founder effect because the species is characterized by only a single mitochondrial COI haplotype. Nonetheless, P. flavescens is absent from many other areas of suitable P. cookii habitat around the island. The most plausible explanation appears to be dispersal limitation (i.e. a contingent absence). Despite high locomotion speeds measured in the laboratory at optimum and mean annual soil temperatures (0.97 and 0.42 cm s?1 at 26°C and 6.5°C, respectively), dispersal in the field indicated that >100 yr would be required to reach all available habitat in the absence of jump dispersal, for which few vectors exist. Thus, current range limits are set by dispersal limitation (i.e. contingent absences) whilst abundance structure is a function of variation in soil substrate quality. Edaphic variables both in this species and other soil invertebrates may be more significant than climatic factors in determining abundance and occurrence, indicating that they should be routinely included in species distribution models. Low genetic diversity and high habitat preference suggest that in the absence of introduction of additional individuals, the species will not spread rapidly at the island. However, over time, the widening distribution of its preferred habitat, P. cookii, as a consequence of a major management intervention (the eradication of feral cats), may enable it to colonize all suitable areas. 相似文献
19.
Robert W. Martin Nigel J. Collar Panji Fauzen Hanom Bashari Adi Widyanto John S. Tasirin Stuart J. Marsden 《Restoration Ecology》2023,31(1):e13770
Remnant forests on the small Wallacean island of Sangihe north of Sulawesi hold the entire ranges of more critically endangered (CR) bird species than any other comparable area on earth. We develop habitat association models for three of these CR species to identify critical habitat features as well as areas where habitat falls slightly short of suitability, and to determine whether another area of forest away from the largest block might be suitable as an insurance site for a translocated population. Hopes for all three species appear almost totally pinned to forest within a 13 km2 area of the Sahendaruman crater, with virtually no near-suitable habitat away from this site. There is, however, little overlap in habitats between one CR species and the other two: cerulean flycatcher Eutrichomyias rowleyi is associated with mature streamside forest with full canopy cover, lianas, and mid-level growth, while Sangihe whistler Coracornis sanghirensis and Sangihe golden bulbul Hypsipetes platenae are restricted to ridgetop forest with full canopy cover and large trees. We pinpoint small areas (around 5 km2) of forest in the crater that are already suitable or can be made so with habitat management, and these are absolute priorities for conservation action. We show how habitat characteristics identified within models might be enhanced, and how features, especially certain tree species, can be used as indicators of future habitat improvement. 相似文献
20.
L. Hansson 《Oecologia》1982,52(2):246-252
Summary Several pairs of species of microtine rodents show inverse distributions or abundance. Here I determine if the inverse abundance relationship of the bank vole Clethrionomys glareolus (a forest species) and the field vole Microtus agrestis (an open field species) could be explained by habitat selection. Habitat selection was examined by choice experiments with combinations of soil and vegetation types, and with separate habitat factors. The effects of early experience and social behaviour were also studied, e.g. in a large outdoor enclosure.
M. agrestis showed a stronger dependence on shelter (e.g. easily excavated soil or thick grassy vegetation) than C. glareolus, while the presence of preferred food did not affect habitat selection for either species. In both species, laboratory-bred specimens showed considerably fewer preferences. Habitat selection in subadult C. glareolus was influenced by social clumping, while territorial behaviour made more even distributions in M. agrestis.The less rigid habitat selection and weaker territorial behaviour observed in the forest species (Clethrionomys) compared with a species from temporary habitats (Microtus) is not consistent with present concepts of r- and K-selection. 相似文献