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1.
The volcanic island of Grand Comoro, Malagasy biogeographic region, is inhabited by three species of Phelsuma day geckos; two island‐endemic taxa (Phelsuma comorensis and Phelsuma v‐nigra comoraegrandensis) and the introduced Phelsuma dubia. Phelsuma comorensis is restricted to elevations of greater than 150 m above sea level on the northern of the island's two volcanoes and is the only Phelsuma above 300 m. The other species are widespread at low elevations but also reach levels above 900 m at the southern volcano. To investigate these divergent distribution patterns, we used environmental niche models based on climate and habitat data and tested whether predicted climate change may influence species distributions. Analyses of niche overlap did not show significant differences between present‐day and predicted future potential distributions of any Phelsuma species studied, which could be seen as an indicator of resilience towards climate change. Climate models reflected the restricted distribution of P. comorensis with precipitation of the wettest month detected as most important variable, whereas habitat models predicted an island‐wide distribution. While climate appears to determine the distribution of P. comorensis, we propose isolation by migration barriers as an alternative and discuss the detection of causal versus spurious relationships in ecological niche models.  相似文献   

2.
Estimates of population density and abundance are essential for the assessment of nonhuman primate conservation status, especially in view of increasing threats. We undertook the most extensive systematic primate survey yet of the Udzungwa Mountains of Tanzania, an outstanding region for primate endemism and conservation in Africa. We used distance sampling to survey three arboreal monkey species, including the endangered and endemic Udzungwa red colobus (Procolobus gordonorum). Overall, we encountered 306 primate clusters over 287 km walked along 162 line transects. We found the lowest cluster densities for both red colobus and Angolan colobus (Colobus angolensis; 0.8 clusters/km2) in the least protected forest (Uzungwa Scarp Forest Reserve, US), while we found the highest densities (3.2 and 2.6 clusters/km2 for red colobus; 3.2 and 2.7 clusters/km2for Angolan colobus) in two large and protected forests in the national park. Unexpectedly, Magombera, a small forest surrounded by plantations, had the highest densities of red colobus (5.0 clusters/km2), most likely a saturation effect due to the rapid shrinking of the forest. In contrast, Sykes’ monkey (Cercopithecus mitis monoides/moloneyi) had more similar densities across forests (3.1–6.6 clusters/km2), including US, suggesting greater resilience to disturbance in this species. For the endemic red colobus monkey, we estimated an abundance of 45–50,000 individuals across all forests, representing ca. 80% of the global population. Though this is a relatively high abundance, the increasing threats in some of the Udzungwa forests are of continued concern for the long-term survival of red colobus and other primates in the area.  相似文献   

3.
R. J. Safford 《Ostrich》2013,84(3-4):151-154
Safford, R.J. 1996. Notes on the biology of the Mauritius Black Bulbul Hypsipetes olivaceus. Ostrich 67: 151–154.

The Mauritius Black Bulbul Hypsipetes olivaceus is a threatened passerine endemic to Mauritius. Direct observations of food items indicate that it is an arboreal omnivore. Animal prey consists mostly of insects and native day-geckoes (Phelsuma spp.). A wide variety of native and exotic fruits is also taken. The species is apparently monogamous, with an egg-laying season extending from at least November to February, usual clutch and brood sizes of two to three, ability rapidly to lay repeat clutches in a new nest, and post-breeding complete moult. In these respects, its annual cycle resembles that of the other native Mauritian passerines. It occurs at very low population density compared to its Indian Ocean congeners; possible reasons for this are given.  相似文献   

4.
Brown-headed spider monkeys (Ateles fusciceps), endemic to the Choco-Darien forests and lower Andean forests of NW Ecuador, are considered critically endangered. Unfortunately, scientific data regarding the actual status of populations is lacking. We combined satellite image analysis, species-specific habitat assessment, and a field survey technique using playback to focus conservation efforts for this species. First, we identified remaining forest via a LANDSAT mosaic and then applied species-specific criteria to delineate remaining forest with potential to hold populations. By combining this with the historical distribution from ecological niche modeling and predicted hunting intensity we generated a species-specific landscape map. Within our study area, forest capable of sustaining Ateles fusciceps covers 5872 km2, of which 2172 km2 (40%) is protected. Unprotected forest considered suitable for Ateles fusciceps extends to 3700 km2 but within this only 989 km2 (23%) is under low hunting pressure and likely to maintain healthy populations of Ateles fusciceps. To overcome problems of sampling at low primate density and in difficult mountain terrain we developed a field survey technique to determine presence and estimate abundance using acoustic sampling. For sites under low hunting pressure density of primates varied with altitude. Densities decreased from 7.49 individuals/km2 at 332 masl to 0.9 individuals/km2 at 1570 masl. Based on combining data sets in a gap analysis, we recommend conservation action focus on unprotected lowland forest to the south and west of the Cotacachi-Cayapas Ecological Reserve where hunting pressure is low and population densities of Ateles fusciceps are greatest.  相似文献   

5.
Species monitoring can be strongly limited by terrain accessibility, impeding our understanding of species ecology and thus challenging their conservation. This is particularly true for species living in the canopy, on cliffs or in dense vegetation. Remote sensing imagery may fill this gap by offering a cost-effective monitoring approach allowing to improve species detection in inaccessible areas. We investigated the applicability of drone-based monitoring for a Critically Endangered insular gecko (Phelsuma inexpectata) and two invasive alien gecko species representing a risk for the former (P. grandis and P. laticauda). We determined the approach distance before inducing behavioural response caused by the drone's presence. All three study species showed no escape behaviour to the drone's presence until very close distances (mean distance for P. inexpectata: 33.8 cm; P. grandis: 21.9 cm; P. laticauda: 26.4 cm). We then performed horizontal and vertical approaches with the drone, taking photos every meter starting at 10 m away from the canopy edge to determine an optimal distance for detection while ensuring species-level identification. We examined a total of 328 photos. We found a bimodality in the number of detected geckos for two species, with different individuals recorded between short and intermediate distances. Therefore, we recommend taking photos at two distances of 2–2.5 and 5 m away from the canopy, ideally facing away from the sun and in low wind conditions. We encourage the application of our methodology for Phelsuma spp., but also for other species of similar size and ecology to improve detection in inaccessible areas.  相似文献   

6.
Vietnam belongs to the global hotspots of biodiversity, and new vertebrate species have been regularly discovered from this country. Lizards and in particular geckos are among the groups with the highest discovery rates. One of the most beautiful geckos recently discovered from Vietnam is the Psychedelic Rock Gecko (Cnemaspis psychedelica), an endemic species of Hon Khoai Island, a small island with a total area of only 8 km2 in Ca Mau Province, southern Vietnam. Although Hon Khoai is protected through the Ca Mau Biosphere Reserve, and collecting and exporting of the wild fauna and flora for commercial purpose is prohibited, the beautiful geckos made their way to the international pet trade. But the species is not only threatened by illegal collecting for the pet trade, but also by macaques introduced on this island. To act against this alarming development, Wildlife at Risk (WAR), the Institute of Ecology and Biological Resources (IEBR) and Cologne Zoo decided to cooperate in building up a gecko house as basis for the establishment of a reserve population, which could become the beginning of a potential conservation breeding program for C. psychedelica. The gecko house was planned in May 2014 and finished in November 2014 in WAR's Hon Me Station in Kien Giang Province, southern Vietnam. It has a movable rain cover with sunblind and contains ten large terraria consisting of aluminium, metal gauze and glass. Terrarium furniture mainly consists of cemented rock walls, plants, and natural soil with leaves. The gecko house also has a double door system to prevent accidently escaped geckos from breaking out. The exterior of the gecko house is covered by a large water proof poster which points both in English and Vietnamese languages to the threats to the Psychedelic Rock Gecko and the background of the conservation project. First small gecko breeding groups were transferred from Hon Khoai Island to the Hon Me Station in March 2015, with relevant permits provided by the respective authorities. Furthermore we report about our first experiences with the keeping and breeding of C. psychedelica, and document colour pattern change during juvenile development.  相似文献   

7.
The Mauritius Kestrel Falco punctatus, once the rarest kestrel worldwide, became an icon of bird conservation after it recovered from four to six individuals in 1974 to some 800 by 2005 following intense conservation management. Its population however then halved within about a decade prompting a re-evaluation of the IUCN status and up listing of the species in 2014 and an increased conservation attention. Drivers of this new decline are unclear and the influence of habitat structure and diet on breeding success may be important contributors but have received relatively little attention, particularly in the way they may interact to influence production of new fledglings. We address this knowledge gap by studying whether breeding success is influenced by habitat structure (in terms of cover of the invasive Ravenala in native habitats, an alien plant causing strong structural shift in the forests that it invades, and extent of cleared area), diet composition and food pass frequency (as a proxy for food intake) and food quality at 28 nests of a re-introduced kestrel population in south east Mauritius during the 2015–2016 breeding season. The kestrel’s diet comprised native and alien birds, reptiles, insects, and small alien mammals, with a disproportionately high proportion of Phelsuma gecko. A higher frequency of food provisioning and percentage cover of Ravenala both contributed to higher breeding success. Ravenala may increase gecko density or increase gecko detectability and predation by the kestrel, or both, while changed land use (pasture and sugar cane fields) may increase prey diversity in the form of non-forest prey known to be eaten by Kestrels (e.g. alien agamids, small mammals and birds). These prey related influences on breeding suggest that the Bambou mountain range provides a human-generated novel ecosystem altering food availability and increasing the kestrel’s breeding success. However, Ravenala is an invasive alien species harmful to the wider forest biodiversity. Progressive weeding of Ravenala and concurrent re-introduction and augmentation of native palms and Pandanus species which geckos can use at comparable densities to Ravenala, is recommended. This would likely improve the kestrel’s hunting habitat quality and maintain high gecko density or detectability and the vegetation structure required for hunting manoeuvrability and prey availability without the negative consequences of invasive Ravenala.  相似文献   

8.
Anthonomus grandis, the cotton boll weevil, causes severe cotton crop losses in North and South America. Here we demonstrate the presence of starch in the cotton pollen grains and young ovules that are the main A. grandis food source. We further demonstrate the presence of α-amylase activity, an essential enzyme of carbohydrate metabolism for many crop pests, in A. grandis midgut. Two α-amylase cDNAs from A. grandis larvae were isolated using RT-PCR followed by 5′ and 3′ RACE techniques. These encode proteins with predicted molecular masses of 50.8 and 52.7 kDa, respectively, which share 58% amino acid identity. Expression of both genes is induced upon feeding and concentrated in the midgut of adult insects. Several α-amylase inhibitors from plants were assayed against A. grandis α-amylases but, unexpectedly, only the BIII inhibitor from rye kernels proved highly effective, with inhibitors generally active against other insect amylases lacking effect. Structural modeling of Amylag1 and Amylag2 showed that different factors seem to be responsible for the lack of effect of 0.19 and α-AI1 inhibitors on A. grandis α-amylase activity. This work suggests that genetic engineering of cotton to express α-amylase inhibitors may offer a novel route to A. grandis resistance.  相似文献   

9.
Aquilaria crassna Pierre ex Lec. and Tectona grandis Linn.f. are sources of resin-suffused agarwood and teak timber, respectively. This study investigated arbuscular mycorrhizal (AM) fungus community structure in roots and rhizosphere soils of A. crassna and T. grandis from plantations in Thailand to understand whether AM fungal communities present in roots and rhizosphere soils vary with host plant species and study sites. Terminal restriction fragment length polymorphism complemented with clone libraries revealed that AM fungal community composition in A. crassna and T. grandis were similar. A total of 38 distinct terminal restriction fragments (TRFs) were found, 31 of which were shared between A. crassna and T. grandis. AM fungal communities in T. grandis samples from different sites were similar, as were those in A. crassna. The estimated average minimum numbers of AM fungal taxa per sample in roots and soils of T. grandis were at least 1.89 vs. 2.55, respectively, and those of A. crassna were 2.85 vs. 2.33 respectively. The TRFs were attributed to Claroideoglomeraceae, Diversisporaceae, Gigasporaceae and Glomeraceae. The Glomeraceae were found to be common in all study sites. Specific AM taxa in roots and soils of T. grandis and A. crassna were not affected by host plant species and sample source (root vs. soil) but affected by collecting site. Future inoculum production and utilization efforts can be directed toward the identified symbiotic associates of these valuable tree species to enhance reforestation efforts.  相似文献   

10.
AimTo investigate whether the frequently advocated climate‐matching species distribution modeling approach could predict the well‐characterized colonization of Florida by the Madagascar giant day gecko Phelsuma grandis.LocationMadagascar and Florida, USA.MethodsTo determine the climatic conditions associated with the native range of P. grandis, we used native‐range presence‐only records and Bioclim climatic data to build a Maxent species distribution model and projected the climatic thresholds of the native range onto Florida. We then built an analogous model using Florida presence‐only data and projected it onto Madagascar. We constructed a third model using native‐range presences for both P. grandis and the closely related parapatric species P. kochi.ResultsDespite performing well within the native range, our Madagascar Bioclim model failed to identify suitable climatic habitat currently occupied by P. grandis in Florida. The model constructed using Florida presences also failed to reflect the distribution in Madagascar by overpredicting distribution, especially in western areas occupied by P. kochi. The model built using the combined P. kochi/P. grandis dataset modestly improved the prediction of the range of P. grandis in Florida, thereby implying competitive exclusion of P. grandis by P. kochi from habitat within the former''s fundamental niche. These findings thus suggest ecological release of P. grandis in Florida. However, because ecological release cannot fully explain the divergent occupied niches of P. grandis in Madagascar versus Florida, our findings also demonstrate some degree of in situ adaptation in Florida.Main conclusionsOur models suggest that the discrepancy between the predicted and observed range of P. grandis in Florida is attributable to either in situ adaptation by P. grandis within Florida, or a combination of such in situ adaptation and competition with P. kochi in Madagascar. Our study demonstrates that climate‐matching species distribution models can severely underpredict the establishment risk posed by non‐native herpetofauna.  相似文献   

11.
The site specific impact on the benthic fauna was assessed within a 4.64 km2 area of intensive aquaculture situated on the eastern side of Hios island (Aegean Sea, Greece) at 11 stations seasonally between November 2000 and October 2001. The benthic fauna showed marked changes in species numbers, diversity and faunal abundance between farm and control sites. The polychaetes Nereis diversicolor, Scolelepis fuliginosa and Capitella capitata were the most dominant species at the farm sites (35% of the total abundance), whilst the most dominant species at the control sites were the polychaete Hyalinoecia brementi and the sipunculid Aspidosiphon muelleri (23% of the total abundance). Species richness, diversity and evenness were higher at the control sites whereas numerical abundance was higher at the farm sites. K-dominance curves suggest a minor impact on the benthic community at the farm sites and temporal changes on macrobenthic assemblages.  相似文献   

12.
Invasive alien plants can compete with native plants for resources, and may ultimately decrease native plant diversity and/or abundance in invaded sites. This could have consequences for native mutualistic interactions, such as pollination. Although invasive plants often become highly connected in plant-pollinator interaction networks, in temperate climates they usually only flower for part of the season. Unless sufficient alternative plants flower outside this period, whole-season floral resources may be reduced by invasion. We hypothesized that the cessation of flowering of a dominant invasive plant would lead to dramatic, seasonal compositional changes in plant-pollinator communities, and subsequent changes in network structure. We investigated variation in floral resources, flower-visiting insect communities, and interaction networks during and after the flowering of invasive Rhododendron ponticum in four invaded Irish woodland sites. Floral resources decreased significantly after R. ponticum flowering, but the magnitude of the decrease varied among sites. Neither insect abundance nor richness varied between the two periods (during and after R. ponticum flowering), yet insect community composition was distinct, mostly due to a significant reduction in Bombus abundance after flowering. During flowering R. ponticum was frequently visited by Bombus; after flowering, these highly mobile pollinators presumably left to find alternative floral resources. Despite compositional changes, however, network structural properties remained stable after R. ponticum flowering ceased: generality increased, but quantitative connectance, interaction evenness, vulnerability, H’2 and network size did not change. This is likely because after R. ponticum flowering, two to three alternative plant species became prominent in networks and insects increased their diet breadth, as indicated by the increase in network-level generality. We conclude that network structure is robust to seasonal changes in floral abundance at sites invaded by alien, mass-flowering plant species, as long as alternative floral resources remain throughout the season to support the flower-visiting community.  相似文献   

13.
Due to their secretive habits, predicting the pattern of spatial distribution of small carnivores has been typically challenging, yet for conservation management it is essential to understand the association between this group of animals and environmental factors. We applied maximum entropy modeling (MaxEnt) to build distribution models and identify environmental predictors including bioclimatic variables, forest and land cover type, topography, vegetation index and anthropogenic variables for six small carnivore species in Mudumalai Tiger Reserve. Species occurrence records were collated from camera-traps and vehicle transects during the years 2010 and 2011. We used the average training gain from forty model runs for each species to select the best set of predictors. The area under the curve (AUC) of the receiver operating characteristic plot (ROC) ranged from 0.81 to 0.93 for the training data and 0.72 to 0.87 for the test data. In habitat models for F. chaus, P. hermaphroditus, and H. smithii “distance to village” and precipitation of the warmest quarter emerged as some of the most important variables. “Distance to village” and aspect were important for V. indica while “distance to village” and precipitation of the coldest quarter were significant for H. vitticollis. “Distance to village”, precipitation of the warmest quarter and land cover were influential variables in the distribution of H. edwardsii. The map of predicted probabilities of occurrence showed potentially suitable habitats accounting for 46 km2 of the reserve for F. chaus, 62 km2 for V. indica, 30 km2 for P. hermaphroditus, 63 km2 for H. vitticollis, 45 km2 for H. smithii and 28 km2 for H. edwardsii. Habitat heterogeneity driven by the east-west climatic gradient was correlated with the spatial distribution of small carnivores. This study exemplifies the usefulness of modeling small carnivore distribution to prioritize and direct conservation planning for habitat specialists in southern India.  相似文献   

14.
Territorial activity was studied using satellite tracking of four brown bears (Ursus arctos) in Kamchatka in 2005–2006 and three brown bears on Sakhalin in 2011–2012. The size of annual home ranges was 6.09–27.58 km2 for females and 153.12 km2 for males. The size of the nuclear zone of the annual home ranges did not exceed 1.68 km2. Seasonal home ranges were largest in August-September and smallest in May. The home ranges of two females in Kamchatka were significantly overlapped, the lesser degree of overlap was noted for two females on Sakhalin. The nature of the use of the study area by bears, essentially depends on the seasonal distribution of food, in particular salmon.  相似文献   

15.
1. A major limitation to effective management of narrow‐range crayfish populations is the paucity of information on the spatial distribution of crayfish species and a general understanding of the interacting environmental variables that drive current and future potential distributional patterns. 2. Maximum Entropy Species Distribution Modeling Software (MaxEnt) was used to predict the current and future potential distributions of four endemic crayfish species in the Ouachita Mountains. Current distributions were modelled using climate, geology, soils, land use, landform and flow variables thought to be important to lotic crayfish. Potential changes in the distribution were forecast by using models trained on current conditions and projecting onto the landscape predicted under climate‐change scenarios. 3. The modelled distribution of the four species closely resembled the perceived distribution of each species but also predicted populations in streams and catchments where they had not previously been collected. Soils, elevation and winter precipitation and temperature most strongly related to current distributions and represented 65–87% of the predictive power of the models. Model accuracy was high for all models, and model predictions of new populations were verified through additional field sampling. 4. Current models created using two spatial resolutions (1 and 4.5 km2) showed that fine‐resolution data more accurately represented current distributions. For three of the four species, the 1‐km2 resolution models resulted in more conservative predictions. However, the modelled distributional extent of Orconectes leptogonopodus was similar regardless of data resolution. Field validations indicated 1‐km2 resolution models were more accurate than 4.5‐km2 resolution models. 5. Future projected (4.5‐km2 resolution models) model distributions indicated three of the four endemic species would have truncated ranges with low occurrence probabilities under the low‐emission scenario, whereas two of four species would be severely restricted in range under moderate–high emissions. Discrepancies in the two emission scenarios probably relate to the exclusion of behavioural adaptations from species‐distribution models. 6. These model predictions illustrate possible impacts of climate change on narrow‐range endemic crayfish populations. The predictions do not account for biotic interactions, migration, local habitat conditions or species adaptation. However, we identified the constraining landscape features acting on these populations that provide a framework for addressing habitat needs at a fine scale and developing targeted and systematic monitoring programmes.  相似文献   

16.
The salt marsh harvest mouse (Reithrodontomys raviventris; RERA) is an endangered species endemic to the coastal wetlands of the San Francisco Estuary, California. RERA are specialized to saline coastal wetlands, and their historical range has been severely impacted by landscape conversion and the introduction of non‐native plant and rodent species. A better understanding of their diet is needed to assess habitat quality, particularly in relation to potential competitors. We investigated three questions using DNA metabarcoding with ITS2 and trnL markers: (1) Do RERA specialize on the native plant, pickleweed (Salicornia pacifica), (2) Do RERA consume non‐native plants, and (3) What is the dietary niche breadth and overlap with three sympatric native and non‐native rodents? RERA diet was dominated by two plants, native Salicornia and non‐native salt bush (Atriplex spp.), but included 48 plant genera. RERA diet breadth was narrowest in fall, when they consumed the highest frequencies of Salicornia and Atriplex, and broadest in spring, when the frequencies of these two plants were lowest. Diet breadth was slightly lower for RERA than for co‐occurring species in pairwise comparisons. All four species consumed similarly high frequencies of wetland plants, but RERA consumed fewer grasses and upland plants, suggesting that it may be less suited to fragmented habitat than sympatric rodents. Diet overlap was lowest between RERA and the native California vole (Microtis californicus). In contrast, RERA diet overlapped substantially with the native western harvest mouse (R. megalotis) and non‐native house mouse (Mus musculus), suggesting potential for competition if these species become sufficiently abundant.  相似文献   

17.
Shan D  Zhao M L  Han B  Han G D 《农业工程》2006,26(10):3175-3182
The Stipa grandis steppe in the Inner Mongolia Autonomous Region occupies an area of 2798081 hm2. On the basis of the genetic variation, it was found that its adaptability to the environmental conditions under grazing pressure was significant. Using the Inter-Simple Sequence Repeat (ISSR) procedure, the changes to the genetic diversity of the Stipa grandis population under different grazing pressures were observed. Plant samples were collected from a series of grazing gradients of the Stipa grandis steppe in Dalinuoer National Nature Reserve in the Inner Mongolia (located at 116°38′–116°41′E and 43°25′–43°27′N.), which has the following vegetation types in abundance: Leymus chinensis is the constructive species; the dominant species include Stipa grandis, Cleistogenes squarrosa, and Artemisia frigida; the companion species is Potentilla acaulis and others. According to the grazing pressure, the following four grazing gradients were identified from the dwellings of the herdsmen to the enclosure site: (1) no grazing (CK enclosure site); (2) light grazing (LG); (3) moderate grazing (MG); (4) heavy grazing (HG). Young leaves of each Stipa grandis were collected during the growing season. The results showed that the Stipa grandis showed abundant genetic diversity despite the fact that certain polymorphic loci were lost; at the same time, new polymorphic loci emerged when grazing pressure increased; a total of 10 primers were used, and 74 bands were produced in total, of which 65 bands were polymorphic; the total percentage of polymorphism was 89%; the percentage of polymorphic loci of the Stipa grandis population decreased with the increase of grazing pressure; the percentage of polymorphic loci was 62.2% in the no-grazing (CK) population, 64.9% in the light-grazing (LG) population, 58.1% in the moderate-grazing (MG) population, and 56.8% in the heavy-grazing (HG) population; the genetic diversity of the population in the descending order using the Shannon's information index is as follows: (1) light grazing (0.3486); (2) no grazing (0.3339); (3) moderate grazing (0.3249); (4) heavy grazing (0.2735) with the same distributional pattern as the Nei's genetic diversity index. The test showed the following: As the grazing pressures increased, the change of genetic diversity decreased; the genetic differentiation coefficient among the population (Gst) was 0.1984, which showed the presence of small partial genetic diversity (19.8%) among populations; gene flow (Nm*) between primers varied from 0.9806 to 3.4463, and the mean gene flow (Nm*) was 2.0202; the UPGMA cluster figure that was constructed on the basis of the genetic distance matrix showed four populations that became genetically closer at each step: (1) The first group was the moderate-grazing (MG) population and the heavy- grazing (HG) population; (2) The second group consisted of the no-grazing (CK) population and the light-grazing (LG) population; (3) The two groups gathered together.  相似文献   

18.
Most recorded extinctions have occurred on oceanic islands, mainly as a result of introduced mammalian predators. The impact of introduced non-mammalian competitors, however, is poorly understood. The house gecko, Hemidactylus frenatus, is one of the most successful invasive reptiles and has been implicated in the decline of endemic geckos and other taxa on a number of tropical and subtropical islands. We investigated the patterns of niche utilization between the house gecko and endemic ornate day gecko, Phelsuma ornata, in Mauritius, two species which were not believed to compete because they had different diel activity periods. The dietary and temporal niche partitioning of the two species were examined in relation to seasonal invertebrate prey abundance for three seasons. Dietary overlap between the two species was least when prey abundance was lowest and temporal overlap in activity greatest. Exploitative competition was therefore inferred, whereby changes in dietary overlap were attributed to shifts in prey selection by the day, but not the house, gecko, which was hypothesized to deplete prey. The compensatory response of the day gecko may have been to increase its tendency for cannibalism, such that the smaller house gecko was indirectly responsible for population reduction of its larger competitor. This is the first study to show how an invasive nocturnal gecko may be affecting a predominantly diurnal species.  相似文献   

19.
Question: Spatial prediction of plant populations is essential for conservation management. This is especially true for rare and/or threatened endemic species, for which knowledge of determinants of distribution is necessary to mitigate threats and counteract decline. We therefore ask if the distribution of an endemic species can be accurately predicted by georeferenced environmental variables or, if anthropogenic variables also need to be taken into account. Location: Alps, Hautes‐Alpes, France. Methods: Potential distribution area and abundance of Eryngium spinalba were predicted with logistic regression and ordinal logistic regression, respectively, in a 57‐km2 watershed. Results: Aspect, global solar radiation in March, elevation and grazing pressure were the main predictors of the probability of occurrence of Eryngium spinalba. Taking into account the persistence of agro‐pastoral activities by diachronic analysis (Napoleonic cadastral map and orthorectified photographs) improved predictions from the model and the level of spatial concordance with independent surveys. Conclusions: Niche modelling improved our understanding of the distribution of this threatened species which, in the context of land abandonment, is diminishing as a result of the decline of its favoured habitats. The key role of pastoral activities and historic continuity for its distribution and persistence was clearly demonstrated.  相似文献   

20.
Anthrax, caused by the bacterium Bacillus anthracis, is a zoonotic disease that persists throughout much of the world in livestock, wildlife, and secondarily infects humans. This is true across much of Central Asia, and particularly the Steppe region, including Kazakhstan. This study employed the Genetic Algorithm for Rule-set Prediction (GARP) to model the current and future geographic distribution of Bacillus anthracis in Kazakhstan based on the A2 and B2 IPCC SRES climate change scenarios using a 5-variable data set at 55 km2 and 8 km2 and a 6-variable BioClim data set at 8 km2. Future models suggest large areas predicted under current conditions may be reduced by 2050 with the A2 model predicting ∼14–16% loss across the three spatial resolutions. There was greater variability in the B2 models across scenarios predicting ∼15% loss at 55 km2, ∼34% loss at 8 km2, and ∼30% loss with the BioClim variables. Only very small areas of habitat expansion into new areas were predicted by either A2 or B2 in any models. Greater areas of habitat loss are predicted in the southern regions of Kazakhstan by A2 and B2 models, while moderate habitat loss is also predicted in the northern regions by either B2 model at 8 km2. Anthrax disease control relies mainly on livestock vaccination and proper carcass disposal, both of which require adequate surveillance. In many situations, including that of Kazakhstan, vaccine resources are limited, and understanding the geographic distribution of the organism, in tandem with current data on livestock population dynamics, can aid in properly allocating doses. While speculative, contemplating future changes in livestock distributions and B. anthracis spore promoting environments can be useful for establishing future surveillance priorities. This study may also have broader applications to global public health surveillance relating to other diseases in addition to B. anthracis.  相似文献   

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