Phylogenetic Reanalysis of the Saudi Gazelle and Its Implications for Conservation

Abstract: The identification of taxonomically appropriate populations of endangered species for captive breeding and reintroduction programs is fundamental to the success of those programs. The Saudi gazelle (   Gazella saudiya ) was endemic to the Arabian peninsula but is now considered extinct in the wild and is potentially a candidate for captive breeding and reintroduction. Using 375 base pairs of mitochondrial DNA (mtDNA) cytochrome b gene derived from museum samples collected from the wild prior to the presumed extinction of this species, we show that G. saudiya is the sister taxon of the African dorcas gazelle (  G. dorcas ). Reciprocal monophyly of G. saudiya mtDNA haplotypes with G. dorcas , coupled with morphological distinctiveness, suggests that it is an evolutionarily significant unit. These data indicate that captive populations identified previously as potential sources of G. saudiya for captive breeding appear incorrectly designated and are irrelevant to the conservation of G. saudiya. The polymerase chain reaction–restriction fragment length polymorphism ( PCR-RFLP) analysis of several private collections of living gazelles in Saudi Arabia provides no evidence for the survival of G. saudiya. We recommend that field surveys be undertaken to establish whether G. saudiya is indeed extinct in the wild and that other private collections within the Arabian peninsula be screened genetically. We urge caution when captive animals of unknown provenance are used to investigate the phylogenetics of cryptic species groups.     

The costs and benefits of predator inspection behaviour in Thomson's gazelles

Summary When Thomson's gazelles (Gazella thomsoni) detect stalking predators, such as cheetahs (Acinonyx jubatus) and lions (Panthera leo), they often approach and follow the predator for up to 72 min (average 14 min). Coursing predators are rarely approached. Gazelle groups were more likely to approach cheetahs if the groups were larger, if the vegetation was low, or if the cheetahs came closer to the group. Immature gazelles were more likely to approach than adults, and a higher proportion of group members participated in inspection behaviour in small groups than in large ones. Gazelles approached closer in less risky situations: if they were in larger groups or if the vegetation was low. Inspection behaviour caused cheetahs to move further between rests and between hunting attempts. Approaching cheetahs was risky, particularly for younger gazelles (probability of being killed while inspecting a cheetah was 1 in 5000 approaches for adults and 1 in 417 approaches for half-grown/adolescent gazelles), and the risks were higher than monitoring cheetahs from a distance. The time costs of predator inspection were also considerable (less than 4.2% of daylight time budget), suggesting that the benefits must be substantial to offset these costs. The results suggested that inspection behaviour was multifunctional, causing stalking predators to move out of the vicinity, enabling gazelles to monitor the predators' movements, and providing an opportunity, particularly for younger animals, to learn about predators. By approaching, gazelles also inform predators that they have been detected and alert other gazelles to the predators' presence.     

Stotting in Thomson's gazelles: an honest signal of condition

Summary The incidence and context of stotting were studied in Thomson's gazelles. Results suggested that gazelles were far more likely to stot in response to coursing predators, such as wild dogs, than they were to stalking predators, such as cheetahs. During hunts, gazelles that wild dogs selected stotted at lower rates than those they did not select. In addition, those which were chased, but which outran the predators, were more likely to stot, and stotted for longer durations, than those which were chased and killed. In response to wild dogs, gazelles in the dry season, which were probably in poor condition, were less likely to stot, and stotted at lower rates, than those in the wet season. We suggest that stotting could be an honest signal of a gazelle's ability to outrun predators, which coursers take into account when selecting prey.     

Inbreeding Depression in the Speke's Gazelle Captive Breeding Program

Abstract: The Speke's gazelle ( Gazella spekei ) captive breeding program has been presented as one of the few examples of selection reducing the genetic load of a population and as a potential model for the captive breeding of endangered species founded from a small number of individuals. In this breeding program, three generations of mate selection apparently increased the viability of inbred individuals. We reanalyzed the Speke's gazelle studbook and examined potential causes for the reduction of inbreeding depression. Our analysis indicates that the decrease in inbreeding depression is not consistent with any model of genetic improvement in the herd. Instead, we found that the effect of inbreeding decreased from severe to moderate during the first generation of inbreeding, and that this change is responsible for almost all of the decline in inbreeding depression observed during the breeding program. This eliminates selection as a potential explanation for the decrease in inbreeding depression and suggests that inbreeding depression may be more sensitive to environmental influences than is usually thought.     

Heterozygosity‐Fitness Correlations and Inbreeding Depression in Two Critically Endangered Mammals

The relation among inbreeding, heterozygosity, and fitness has been studied primarily among outbred populations, and little is known about these phenomena in endangered populations. Most researchers conclude that the relation between coefficient of inbreeding estimated from pedigrees and fitness traits (inbreeding‐fitness correlations) better reflects inbreeding depression than the relation between marker heterozygosity and fitness traits (heterozygosity‐fitness correlations). However, it has been suggested recently that heterozygosity‐fitness correlations should only be expected when inbreeding generates extensive identity disequilibrium (correlations in heterozygosity and homozygosity across loci throughout the genome). We tested this hypothesis in Mohor gazelle (Gazella dama mhorr) and Iberian lynx (Lynx pardinus). For Mohor gazelle, we calculated the inbreeding coefficient and measured heterozygosity at 17 microsatellite loci. For Iberian lynx, we measured heterozygosity at 36 microsatellite loci. In both species we estimated semen quality, a phenotypic trait directly related to fitness that is controlled by many loci and is affected by inbreeding depression. Both species showed evidence of extensive identity disequilibrium, and in both species heterozygosity was associated with semen quality. In the Iberian lynx the low proportion of normal sperm associated with low levels of heterozygosity was so extreme that it is likely to limit the fertility of males. In Mohor gazelle, although heterozygosity was associated with semen quality, inbreeding coefficient was not. This result suggests that when coefficient of inbreeding is calculated on the basis of a genealogy that begins after a long history of inbreeding, the coefficient of inbreeding fails to capture previous demographic information because it is a poor estimator of accumulated individual inbreeding. We conclude that among highly endangered species with extensive identity disequilibrium, examination of heterozygosity‐fitness correlations may be an effective way to detect inbreeding depression, whereas inbreeding‐fitness correlations may be poor indicators of inbreeding depression if the pedigree does not accurately reflect the history of inbreeding. Correlaciones Heterocigosidad‐ Adaptabilidad y Depresión Endogámica en Dos Especies de Mamíferos Críticamente en Peligro     

Satellite tracking reveals a dichotomy in migration strategies among juvenile loggerhead turtles in the Northwest Atlantic

Few data are available on the movements and behavior of immature Atlantic loggerhead sea turtles (Caretta caretta) from their seasonal neritic foraging grounds within the western north Atlantic. These waters provide developmental habitat for loggerheads originating from several western Atlantic nesting stocks. We examined the long-term movements of 23 immature loggerheads (16 wild-caught and seven headstart turtles) characterizing their seasonal distribution, habitat use, site fidelity, and the oceanographic conditions encountered during their migrations. We identified two movement strategies: (1) a seasonal shelf-constrained north–south migratory pattern; and (2) a year-round oceanic dispersal strategy where turtles travel in the Gulf Stream to the North Atlantic and their northern dispersal is limited by the 10–15°C isotherm. When sea surface temperatures dropped below 20°C, neritic turtles began a migration south of Cape Hatteras, North Carolina (USA) where they established fidelity to the waters between North Carolina’s Outer Banks and the western edge of the Gulf Stream along outer continental shelf. Two turtles traveled as far south as Florida. Several turtles returned to their seasonal foraging grounds during subsequent summers. Northern movements were associated with both increased sea surface temperature (>21°C) and increased primary productivity. Our results indicate strong seasonal and interannual philopatry to the waters of Virginia (summer foraging habitat) and North Carolina (winter habitat). We suggest that the waters of Virginia and North Carolina provide important seasonal habitat and serve as a seasonal migratory pathway for immature loggerhead sea turtles. North Carolina’s Cape Hatteras acts as a seasonal “migratory bottleneck” for this species; special management consideration should be given to this region. Six turtles spent time farther from the continental shelf. Three entered the Gulf Stream near Cape Hatteras, traveling in the current to the northwest Atlantic. Two of these turtles remained within an oceanic habitat from 1 to 3 years and were associated with mesoscale features and frontal systems. The ability of large benthic subadults to resume an oceanic lifestyle for extended periods indicates plasticity in habitat use and migratory strategies. Therefore, traditional life history models for loggerhead sea turtles should be reevaluated.     

Bimodal orientation and the occurrence of temporary reverse bird migration during autumn in south Scandinavia

Extensive ringing data from a coastal site (Falsterbo Bird Observatory) in southwesternmost Sweden were used to investigate the occurrence of reverse autumn migration among 20 passerine bird species of widely different migration categories. The data demonstrate that reverse migration is a widespread and regular phenomenon among nocturnal as well as diurnal migrants and among irruptive migrants, temperate zone migrants, and long-distance migrants destined for tropical winter quarters. The reoriented movements were directed approximately opposite to the normal migration direction, i.e. between NNW and ENE from the coast and towards inland. Median distances of reverse movements varied between 9 and 65 km. Some individuals of irruptive and partial migrants settled to winter in the reverse direction. Bird species with relatively small fat reserves at capture were more likely to perform reverse migratory movements than species with larger fat deposits. In two species birds performing forward migration were significantly heavier within 10 days after capture than individuals performing reverse movements. The reoriented movements probably are of adaptive significance for birds confronted with the sea and pre-disposed to refuelling during migration. A bimodal orientation mechanism will bring the birds from an area with high competition for food and high predation risk to more suitable resting and feeding grounds before resuming migration in the forward direction and crossing the barrier. Received: 11 July 1995/Accepted after revision: 19 November 1995     

Estimating Plecoglossus altivelis altivelis migration using a mass balance model expressed by hydrological distribution parameters in a major limpid river basin in Japan

We examined the influence of several hydrological and meteorological parameters on the migratory movements of ayu Plecoglossus altivelis altivelis in central Japan. When comprehensively evaluating rivers and ayu behaviour on a catchment scale, the subjects of analysis typically include human activities and hydrological and meteorological phenomena. However, limiting analyses to such factors may be too restrictive when human activities are being conducted. Accordingly, we incorporated a biological viewpoint into the evaluation method, analysing hydrological data (river discharge, river water temperature, sea water temperature) to determine watershed characteristics and examining the relationship between these characteristics and the habitat conditions of ayu. Then we constructed a numerical model for ayu migratory runs that incorporated ayu ecology and watershed characteristics. Analyses of ayu movements from a lower estuarine dam demonstrated that downstream displacements were associated with high water flows of more than 200 m³ s⁻¹ at the beginning of summer. We conclude that it is important to consider the effects of environmental parameters on the movements of different fish species to understand the causes of spatial variation in fish distribution in lowland rivers.     

Mating effort and space use of an alpine ungulate during the rut

In ungulates, the rut generally leads to increased intra and interpopulation movements for males. Because movements induce energetic costs and missed feeding opportunities, they could be an indication of male mating effort. We studied space use of 44 male mountain goats (Oreamnos americanus) from three neighboring subpopulations in southeast Alaska, during the rut from 2005 to 2008. Using mixed models and an information theoretic approach with AIC, we analyzed the relationships between individual traits of males and their space use. We found no indication of breeding migration between subpopulations. Distances between individual seasonal ranges were not related to any individual trait. Daily movements, home range sizes, and total distance traveled during the rut did not vary with mass or age of individuals. As such, effects of individual traits on male space use during the rut appear weak and observed space use patterns do not support any of the main mating effort hypotheses.     

The relationship between loggerhead turtle (<Emphasis Type="Italic">Caretta caretta</Emphasis>) movement patterns and Mediterranean currents

Previous studies have shown that loggerhead sea turtles (Caretta caretta), monitored by satellite telemetry, complete long-distance migration between the western and eastern Mediterranean basins following a seasonal pattern. This study investigated if these migration routes may be influenced by surface currents by superimposing the tracks of three loggerhead turtles (curved carapace length >55 cm), migrating from the western to the eastern Mediterranean basin, on Lagrangian data of current developed into pseudo-eulerian speed fields. The average travel speed of the turtles was 1.6 km h⁻¹ and did not depend on the current speed or direction. We observed a connection between surface currents and the turtles’ migration routes, although not a conclusive one. These observations show that neritic stage loggerhead turtles conduct migration in two distinct alternate phases: the first characterized by high and constant speed of travel both when swimming with or against currents and the second typified by low travel speeds and a good concurrence between the trailed routes and the course of the currents. These two phases corresponded to two types of movements, one where the turtle migrates actively to reach a specific destination (either neritic foraging, wintering or nesting ground) and the other, where the turtle drifts with the mesoscale current and forages pelagically. It seemed thus, that the influence of currents on a turtle’s movements depends on the turtle’s momentary behaviour and location of residence.     

Early onset of vegetation growth vs. rapid green-up: impacts on juvenile mountain ungulates

Seasonal patterns of climate and vegetation growth are expected to be altered by global warming. In alpine environments, the reproduction of birds and mammals is tightly linked to seasonality; therefore such alterations may have strong repercussions on recruitment. We used the normalized difference vegetation index (NDVI), a satellite-based measurement that correlates strongly with aboveground net primary productivity, to explore how annual variations in the timing of vegetation onset and in the rate of change in primary production during green-up affected juvenile growth and survival of bighorn sheep (Ovis canadensis), Alpine ibex (Capra ibex), and mountain goats (Oreamnos americanus) in four different populations in two continents. We indexed timing of onset of vegetation growth by the integrated NDVI (INDVI) in May. The rate of change in primary production during green-up (early May to early July) was estimated as (1) the maximal slope between any two successive bimonthly NDVI values during this period and (2) the slope in NDVI between early May and early July. The maximal slope in NDVI was negatively correlated with lamb growth and survival in both populations of bighorn sheep, growth of mountain goat kids, and survival of Alpine ibex kids, but not with survival of mountain goat kids. There was no effect of INDVI in May and of the slope in NDVI between early May and early July on juvenile growth and survival for any species. Although rapid changes in NDVI during the green-up period could translate into higher plant productivity, they may also lead to a shorter period of availability of high-quality forage over a large spatial scale, decreasing the opportunity for mountain ungulates to exploit high-quality forage. Our results suggest that attempts to forecast how warmer winters and springs will affect animal population dynamics and life histories in alpine environments should consider factors influencing the rate of changes in primary production during green-up and the timing of vegetation onset.     

Tracking migration routes and the annual cycle of a trans-Sahara songbird migrant

Movement ecology studies have highlighted the importance of individual-based research. As tracking devices have not been applicable for identifying year-around movements of small birds until recently, migration routes of such species relied on visual observations and ring recoveries. Within the Palaearctic–African migration system, loop migration seems to be the overall migration pattern. The interindividual variations within species-specific migration routes are, however, unknown. Here, we track the individual migration routes and annual cycles of male Northern Wheatears Oenanthe oenanthe, a trans-Sahara songbird migrant from a German breeding population with light-level geolocators. Two migrated most likely via Spain towards western Africa but returned via Corsica/Sardinia, while two others seemed to migrate via Sardinia and Corsica in autumn and via Spain and France in spring (loop migration). The fifth took presumably the same route via France and the Balearics in both seasons. All birds wintered in the Sahel zone of western Africa. Overall migration distances for autumn and spring were similar (about 4,100?km), whereas the overall migratory speed was generally higher in spring (126?km?day^?1) than in autumn (88?km?day^?1). Birds spent about 130?days at the breeding area and 147?days at the wintering grounds.     

The good and the bad stopover: behaviours of migrant reed warblers at two contrasting sites

Successful migration for passerine birds depends largely on the quality of stopover habitats, but we still lack complete knowledge of how migrants search for habitats en route and how they behave when landing at poor quality stopover sites. We compared the distance of exploratory movements and stopover durations of the reed warbler Acrocephalus scirpaceus, a reedbed habitat specialist, released at suitable (reed bed) and unsuitable (sand dune) stopover sites. Birds tape-lured during nocturnal migration to a sand dune were captured, radio-tagged, released and tracked at two sites of contrasting habitat quality. Lean birds were found to move further in the dunes (max. 300 m) than in reeds (max. 200 m), whereas ‘fat’ individuals at both sites remained stationary. Birds spent just 1 day in the dunes and up to 13 days in the reeds. Our results suggest that some nocturnal migrants with restricted diurnal exploratory movements depend on stopover site selection when ceasing nocturnal flight.     

Correlating seabird movements with ocean winds: linking satellite telemetry with ocean scatterometry

Satellite telemetry studies of the movements of seabirds are now common and have revealed impressive flight capabilities and extensive distributions among individuals and species at sea. Linking seabird movements with environmental conditions over vast expanses of the world’s open ocean, however, remains difficult. Seabirds of the order Procellariiformes (e.g., petrels, albatrosses, and shearwaters) depend largely on wind and wave energy for efficient flight. We present a new method for quantifying the movements of far-ranging seabirds in relation to ocean winds measured by the SeaWinds scatterometer onboard the QuikSCAT satellite. We apply vector correlation (as defined by Crosby et al. in J Atm Ocean Tech 10:355–367, 1993) to evaluate how the trajectories (ground speed and direction) for five procellariiform seabirds outfitted with satellite transmitters are related to ocean winds. Individual seabirds (Sooty Shearwater, Pink-footed Shearwater, Hawaiian Petrel, Grey-faced Petrel, and Black-footed Albatross) all traveled predominantly with oblique, isotropic crossing to quartering tail-winds (i.e., 105–165° in relation to birds’ trajectory). For all five seabirds, entire track line trajectories were significantly correlated with co-located winds. Greatest correlations along 8-day path segments were related to wind patterns during birds’ directed, long-range migration (Sooty Shearwater) as well as movements associated with mega-scale meteorological phenomena, including Pacific Basin anticyclones (Hawaiian Petrel, Grey-faced Petrel) and eastward-propagating north Pacific cyclones (Black-footed Albatross). Wind strength and direction are important factors related to the overall movements that delineate the distribution of petrels at sea. We suggest that vector correlation can be used to quantify movements for any marine vertebrate when tracking and environmental data (winds or currents) are of sufficient quality and sample size. Vector correlation coefficients can then be used to assess population—or species-specific variability and used to test specific hypotheses related to how animal movements are associated with fluid environments.     

榆林地区植被时空分异特征及其影响因素研究

植被作为反映陆地生态系统和气候的重要指标,对研究全球或区域生态环境变化具有重要作用.以地处黄土高原生态脆弱区的榆林市为研究区,基于地理探测器模型,选取坡向、坡度、气温、降水和土壤类型5类自然因子,土地利用类型、人口密度和GDP 3类人文因子,分析榆林地区植被空间分异特征及其驱动力,并揭示了促进植被生长影响因子的最适宜特...     

Movement ecology: size-specific behavioral response of an invasive snail to food availability

Immigration, emigration, migration, and redistribution describe processes that involve movement of individuals. These movements are an essential part of contemporary ecological models, and understanding how movement is affected by biotic and abiotic factors is important for effectively modeling ecological processes that depend on movement. We asked how phenotypic heterogeneity (body size) and environmental heterogeneity (food resource level) affect the movement behavior of an aquatic snail (Tarebia granifera), and whether including these phenotypic and environmental effects improves advection-diffusion models of movement. We postulated various elaborations of the basic advection diffusion model as a priori working hypotheses. To test our hypotheses we measured individual snail movements in experimental streams at high- and low-food resource treatments. Using these experimental movement data, we examined the dependency of model selection on resource level and body size using Akaike's Information Criterion (AIC). At low resources, large individuals moved faster than small individuals, producing a platykurtic movement distribution; including size dependency in the model improved model performance. In stark contrast, at high resources, individuals moved upstream together as a wave, and body size differences largely disappeared. The model selection exercise indicated that population heterogeneity is best described by the advection component of movement for this species, because the top-ranked model included size dependency in advection, but not diffusion. Also, all probable models included resource dependency. Thus population and environmental heterogeneities both influence individual movement behaviors and the population-level distribution kernels, and their interaction may drive variation in movement behaviors in terms of both advection rates and diffusion rates. A behaviorally informed modeling framework will integrate the sentient response of individuals in terms of movement and enhance our ability to accurately model ecological processes that depend on animal movement.     

Is catchment productivity a useful predictor of taxa richness in lake plankton communities?

The influence of catchment variables on lake organisms is understudied. The terrestrial zone in the vicinity of lakes is, however, probably highly important for biota due to the effects on water chemistry and to various processes operating across ecosystem boundaries. We examined the relative importance of lake and catchment variables, as well as large-scale geographical factors, on the taxa richness of phyto- and zooplankton in 100 small lakes in Finland. In variation partitioning, the variability of phytoplankton richness was most strongly related to the effects of lake variables, the joint effects of lake and catchment variables, and the joint effects of all three groups of variables. Zooplankton richness, in turn, was most strongly related to the effects of lake and catchment variables and the joint effect of lake and catchment variables. The exact results of the variation partitioning depended on the catchment sizes considered in the regression models. Among lake variables, planktonic richness was strongly related to variables indicating productivity. Among catchment variables, the normalized difference vegetation index (NDVI), indicating catchment productivity, showed a relatively strong association with planktonic richness. These results provide evidence that catchment variables such as the NDVI may be efficient predictors of planktonic richness in small lakes. It is possible that individual lakes embedded in a highly productive landscape have higher taxa richness than solitary, potentially productive lakes because of the high influx of dispersing propagules from the regional pool. We also suggest that catchment variables may respond to environmental changes at different scales than the lake variables, and explicit consideration of catchment productivity would therefore be useful when planning research and monitoring programs for freshwater organisms.     

Relationship between Coefficient of Inbreeding and Parasite Burden in Endangered Gazelles

Abstract: We studied the effects of inbreeding depression on parasite infection in three species of endangered gazelles: Gazella cuvieri , G. dama, and G. dorcas . Coefficients of inbreeding were calculated for all individuals because complete genealogies were available. The levels of inbreeding differ both intra- and interspecifically. We collected samples of feces and determined nematode infection by counting nematode eggs in the samples. At the interspecific level, the species with the highest mean levels of inbreeding (  G. cuvieri ) had the highest levels of gastrointestinal parasites. Analyses done at the intraspecific level revealed a positive relationship between individual coefficient of inbreeding and parasite infection in G. cuvieri , but not in the species with the intermediate and lowest levels of inbreeding. Our findings suggest that high levels of inbreeding may make individuals more susceptible to parasitism, even under favorable environmental conditions, so this factor should be taken into account by those managing endangered species.     

Discrimination of ocean wave features by hatchling loggerhead sea turtles, Caretta caretta

At the beginning of their offshore migration, hatchling sea turtles orient directly into oceanic waves as they swim away from land. Recent experiments have demonstrated that hatchlings swimming underwater can determine the propagation direction of waves by monitoring the circular movements they experience as waves pass above. During July and August 1993, we studied how loggerhead sea turtle hatchlings (Caretta caretta L.) from the east coast of Florida, USA, responded to a range of wave parameters. We constructed a wave simulator to reproduce in air the circular movements that normally occur beneath small ocean waves. Hatchlings suspended in air and subjected to these orbital movements attempted to orient into simulated waves when periods and amplitudes were similar to those found near the Florida coast. Orbital movements with longer periods (greater than 10 s), however, failed to elicit responses. The results demonstrate that hatchling loggerheads can distinguish between waves with different periods and amplitudes, and that Florida hatchlings respond most strongly to orbital movements closely resembling those of waves that occur near their natal beach. Received: 28 May 1996 / Accepted: 17 September 1996     

三江源地区基于植被生长季的NDVI对气候因子响应的差异性研究

采用1999—2008年NDVI和三江源地区及周边31个气象站点的温度和降水旬数据,在确定每年5月中旬至9月底作为三江源地区植被生长季（14旬）的基础上,分析NDVI对气候因子变化响应的区域差异。结果显示：以巴颜喀拉山为界,三江源西部生长季内NDVI指数对温度、降水的线性相关性明显比中东部普遍,同时,不同海拔地段响应程度存在着明显的差异,且海拔5300m左右为线性响应的最高限,NDVI对气候因子的线性响应主要表现为对温度正相关和降水负相关。因此,对三江源生长季内植被生长而言,水条件明显好于温度条件,并且温度对植被覆盖的影响通过直接正相关和降水负相关表现出来,温度是三江源地区植被生长的主导因子。