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1.
Limited conservation resources necessitate the prioritization of management efforts and one of the mechanisms for prioritization is the identification of hotspots. For some species of conservation concern, hotspots have been delineated, often using individual abundance as the metric. However, areas that attract individuals from multiple breeding populations may be a higher priority for conservation. These areas may have more abundant resources or habitat quality, and multiple breeding populations simultaneously benefit from conservation actions in these areas. We identified non-spawning aggregations of Lake Sturgeon Acipenser fulvescens in lakes Huron and Erie of the Great Lakes. The spawning period in Lake Sturgeon only represents a brief portion of their life and conservation goals need to include non-spawning areas. Based on 12 microsatellite loci, we determined the population of origin of individuals in the aggregations and computed a modified population-level Simpson’s diversity index (pD). Using this criterion, two hotspots were identified. The North Channel of Lake Huron had the highest diversity of represented populations (pD = 3.14). The second identified hotspot was Saginaw Bay in Lake Huron (pD = 1.78). Both hotspots had evidence of long-distance movement into the area. Monitoring of aggregations should continue to assess temporal variability in hotspot delineation.  相似文献   

2.
A synthetic analysis of the distribution, abundance and some biological traits of the common pandora (Pagellus erythrinus) was performed. Data were gathered in 15 experimental bottom trawl surveys carried out off the southern Tyrrhenian Sea from 1994 to 2008. A total of 2,166 P. erythrinus were found in the investigated area, with a preference for the upper continental shelf (10–100 m). The highest persistence was recorded in the trawl-banned areas. The sex ratio Sr = F/(F + M) ranged between 0.60 and 0.96 (overall 0.78). The size at which 50 % of the individuals were mature was 157 and 170 mm total length for females and males, respectively. The length–weight relationship for all individuals was described by the following parameters: a = 0.016 and b = 2.905. Growth was evaluated (sexes combined) by applying length-based methods; up to eight significant modal components were evidenced. The von Bertalanffy growth parameters for the whole population were estimated at L  = 454 mm, K = 0.08 and t 0 = ?2.57. The present results are in agreement with the information available for the other Mediterranean stocks suggesting common biological features.  相似文献   

3.
Ichthyofaunal diversity of the Dianshan lake in Shanghai, China was assessed during the year 2013 from samples of finfish harvested using fleets of gillnets and trawls of different mesh sizes with the aim of generating necessary data that could support sustainable use of finfish in this lake. Morphometric parameters of specimens caught were taken following standard procedures. Totally 21,308 specimens belonging to 40 species, 15 families and 7 orders were encountered throughout the study period. Seasonal abundance was lowest (395 individuals) during March (spring) and highest (4428 individuals) during August (summer). Cyprinidae was the dominant family (22 species) and Coilia ecetenes taihuensis was the most abundant species (30.69%), followed by Acheilognathus taenianalis (17.8618%), Plagiognathops microlepis (16.567%), Carassius auratus (14.492%). The evenness, richness and biodiversity of the faunal assemblage were also evaluated by Shannon–Wiener index (H′), Margalef’s diversity Index (d) and evenness index (J) respectively. Hypophthalmichthys nobilis was the largest and heaviest fish (34.909 cm, FL; 889.355 g, W), the smallest fish in length recorded was Odontamblyopus rubicundus (4.19 cm) while Plecoglossus altivelis altivelis (1.1 g) was the lowest in terms of mean weight. The mean condition factor for all fish species was (K = 1.72), showing fish species were generally in ‘good’ condition. Fluctuations in species occurrence and abundance noted in our study may be accounted from the variation in the physico-chemical parameters of the Lake in respect to time. But, under such a situation it is evident that the small fish species increased to a great extent and a few like Coilia ecetenes taihuensis became the dominant.  相似文献   

4.
Surveys of genetic structure of introduced populations of nonindigenous species may reveal the source(s) of introduction, the number of introduction events, and total inoculum size. Here we use the mitochondrial cytochrome c oxidase subunit 1 (COI) gene to explore genetic structure and contrast invasion histories of two ecologically similar and highly invasive colonial ascidians, the golden star tunicate Botryllus schlosseri and the violet tunicate Botrylloides violaceus, in their global and introduced North American ranges. Haplotype and nucleotide diversities for B. schlosseri were significantly higher than for B. violaceus both globally (h = 0.872; ?? = 0.054 and h = 0.461; ?? = 0.007, respectively) and in their overlapping North American ranges (h = 0.874; ?? = 0.012 and h = 0.384; ?? = 0.006, respectively). Comparative population genetics and phylogenetic analyses revealed clear differences in patterns of invasion for these two species. B. schlosseri populations on the west and east coasts of North America were seeded from the Pacific and Mediterranean regions, respectively, whereas all North American B. violaceus populations were founded by one or more introduction events from Japan. Differences in genetic structure of invasive populations for these species in North America are consistent with their contrasting probable introduction vectors. B. schlosseri invasions most likely resulted from vessel hull fouling, whereas B. violaceus was likely introduced as a ??fellow traveler?? in the shellfish aquaculture trade.  相似文献   

5.
Seedling survival plays a critical role in maintaining a supply of potential recruits. We examined seedling recruitment, survival and growth in Wollemia nobilis, a rare, long-lived Australian conifer. Wollemia nobilis seedlings and juveniles were monitored for 16 years (1996–2011). While W. nobilis can recruit from seed and, unlike most conifers, persist through resprouting, seed-based recruitment was the primary focus of this study. Sixty-five per cent of new seedlings died within their first year and only 7 % persisted for the 16-year monitoring period. However, 44 % of established juvenile plants (of unknown age at the beginning of the study) persisted throughout the 16-year monitoring period. Growth of seedlings and juveniles was very slow; growth estimates for most individuals had 95 % confidence intervals that included zero. The recruitment strategy of W. nobilis may be to maintain a slow-growing juvenile bank—a strategy typical of other shade-tolerant rainforest trees, including other Araucariaceae. Seedling recruitment in W. nobilis may act together with resprouting to maintain the population.  相似文献   

6.
Defining genetic populations and detecting hybridization with introduced or domestic taxa are two major concerns for the conservation of population-level diversity. We studied the genetic population structure of large, migratory caribou herds (Rangifer tarandus granti) on Alaska’s North Slope and their potential hybridization with introduced domestic reindeer (R. t. tarandus). Using a population genetics approach, we determined: (1) whether the four caribou herds could be differentiated; (2) how distance and population size appear to drive genetic population structure; and (3) how contact with reindeer has affected the genetic identity of herds. Samples from four caribou herds (n = 245) and reindeer (n = 67) were analyzed at 19 microsatellite loci. We found that North Slope caribou are isolated by distance, with no differentiation among herd pairs except for the most geographically distant herds (F st  = 0.003, Jost’s D = 0.023; P-values < 0.001). We detected reindeer-caribou admixture in all populations except Kodiak Island, including 8 % of individuals in caribou herds and 14 % of individuals in Seward Peninsula reindeer herds. However, considering the stable or increasing trend in North Slope herds, reindeer introgression has had no apparent deleterious effect on herd demographics. Our findings indicate long-term genetic exchange among North Slope caribou herds when their ranges overlap, and suggest that herd size may influence susceptibility to reindeer introgression. As North Slope herd ranges are increasingly altered by industrial development, this study can provide a baseline for detecting potential future impacts to what are currently large, diverse, and naturally evolving herds.  相似文献   

7.
Age and growth estimates for the smooth skate, Malacoraja senta, were derived from 306 vertebral centra from skates caught in the North Atlantic off the coast of New Hampshire and Massachusetts, USA. Males and females were aged to 15 and 14 years, respectively. Male and female growth diverged at both ends of the data range and the sexes required different growth functions to describe them. Males followed a traditional growth scenario and were best described by a von Bertalanffy curve with a set L o (11 cm TL) where L inf  = 75.4 cm TL, K = 0.12. Females required the use of back-calculated values to account for a lack of small individuals, using these data they were best described by a von Bertalanffy curve where growth parameters derived from vertebral length-at-age data are L inf  = 69.6 cm TL, K = 0.12, and L o  = 10.  相似文献   

8.
Radiotelemetry and unmarked occupancy modeling have been used to estimate animal population growth, but have not been compared for ungulates. We compared white-tailed deer (Odocoileus virginianus) population growth estimates from radiomarked individuals and occupancy modeling of unmarked individuals and evaluated advantages and disadvantages of each method. Estimates of population growth were obtained using remote camera (N = 54/year) detection/non-detection occupancy surveys of unmarked deer and from survival and recruitment data of radiomarked adult females (N = 87) and neonate fawns (N = 127) in a predominantly forested region of the Upper Peninsula of Michigan, USA, 2009–2011. We hypothesized that occupancy models and radiotelemetry data would have similar population growth trends because both methods sampled the same temporally closed population. Percent changes in camera trap data generally reflected finite population growth (λ) of radiomarked deer which increased (λ = 1.10 ± 0.01) from 2009 to 2010, but decreased (λ = 0.87 ± 0.02) from 2010 to 2011. Also, unmarked adult female abundance and fawn:adult female ratios generally reflected trends in radiomarked deer survival and recruitment. Royle–Nichols occupancy model abundance estimates had wide confidence intervals, which may preclude using this method from accurately estimating deer population growth. Radiotelemetry provided more precise population growth estimates, while allowing collection of vital rates and location data. However, the Royle–Nichols occupancy model may be preferred to radiotelemetry because it reflected yearly variation in population growth with reduced labor and no invasive marking. Researchers should consider the objectives and logistics of their study when choosing a specific method.  相似文献   

9.
Small or isolated populations are highly susceptible to stochastic events. They are prone and vulnerable to random demographic or environmental fluctuations that could lead to extinction due to the loss of alleles through genetic drift and increased inbreeding. We studied Ambystoma leorae an endemic and critically threatened species. We analyzed the genetic diversity and structure, effective population size, presence of bottlenecks and inbreeding coefficient of 96 individuals based on nine microsatellite loci. We found high levels of genetic diversity expressed as heterozygosity (Ho = 0.804, He = 0.613, He* = 0.626 and HNei = 0.622). The population presents few alleles (4–9 per locus) and genotypes (3–14 per locus) compared with other mole salamanders species. We identified three genetically differentiated subpopulations with a significant level of genetic structure (FST = 0.021, RST = 0.044 y Dest = 0.010, 95 % CI). We also detected a reduction signal in population size and evidence of a genetic bottleneck (M = 0.367). The effective population size is small (Ne = 45.2), but similar to another mole salamanders with restricted distributions or with recently fragmented habitat. The inbreeding coefficient levels detected are low (FIS = ?0.619–0.102) as is gene flow. Despite, high levels of genetic diversity A. leorae is critically endangered because it is a small isolated population.  相似文献   

10.
The growth/survival trade-off is a fundamental aspect of life-history evolution that is often explained by the direct energetic requirement for growth that cannot be allocated into maintenance. However, there is currently no empirical consensus on whether fast-growing individuals have higher resting metabolic rates at thermoneutrality (RMRt) than slow growers. Moreover, the link between growth rate and daily energy expenditure (DEE) has never been tested in a wild endotherm. We assessed the energetic and survival costs of growth in juvenile eastern chipmunks (Tamias striatus) during a year of low food abundance by quantifying post-emergent growth rate (n = 88), RMRt (n = 66), DEE (n = 20), and overwinter survival. Both RMRt and DEE were significantly and positively related to growth rate. The effect size was stronger for DEE than RMRt, suggesting that the energy cost of growth in wild animals is more likely to be related to the maintenance of a higher foraging rate (included in DEE) than to tissue accretion (included in RMRt). Fast growers were significantly less likely to survive the following winter compared to slow growers. Juveniles with high or low RMRt were less likely to survive winter than juveniles with intermediate RMRt. In contrast, DEE was unrelated to survival. In addition, botfly parasitism simultaneously decreased growth rate and survival, suggesting that the energetic budget of juveniles was restricted by the simultaneous costs of growth and parasitism. Although the biology of the species (seed-storing hibernator) and the context of our study (constraining environmental conditions) were ideally combined to reveal a direct relationship between current use of energy and future availability, it remains unclear whether the energetic cost of growth was directly responsible for reduced survival.  相似文献   

11.
Age and growth estimates for the shortfin mako, Isurus oxyrinchus, derived from vertebral centra of 258 specimens (118 males, 140 females), ranging in size from 64 to 340 cm fork length (FL) were compared with data from 22 tag–recaptured individuals (74–193 cm FL) and length–frequency data from 1822 individuals (1035 males, 787 females; 65–215 cm FL). Annual band-pair deposition, confirmed by a concurrent bomb radiocarbon validation study, was used as the basis for band interpretation. Validation was further confirmed with a tetracycline-injected male shortfin mako recaptured after being at liberty off South Africa for 1 year and aged at 18 years. Growth rates from tag–recapture analysis (GROTAG) were higher than those derived from vertebral annuli and were only available from sharks up to 193 cm FL at recapture. Modal length–frequency data were used to verify the first four age classes. Growth curves were fit using both von Bertalanffy and Gompertz models. The 3-parameter version of the von Bertalanffy growth function produced the most biologically reasonable values for males, based on observed data (L  = 253 cm FL, K = 0.125 year?1 (estimated longevity = 21 year), and L 0 = 72 cm). The 3-parameter version of the Gompertz growth function produced the most biologically reasonable estimates, for females (L  = 366 cm FL, K = 0.087 year?1 (estimated longevity = 38 year) and L 0 = 88 cm. Males and females were aged to 29 (260 cm FL) and 32 years (335 cm FL), respectively. Both sexes grew similarly to age 11 (207 cm FL, 212 cm FL for males and females, respectively) when the curve leveled in males and continued to rise in females. Age at 50% maturity was estimated at 8 years for males (185 cm FL) and 18 years for females (275 cm FL). The species grows slower, matures later and has a longer life span than previously reported in North Atlantic waters.  相似文献   

12.
The annual variability in growth and life history traits of brown trout (Salmo trutta L.) and Arctic charr (Salvelinus alpinus (L.)) in Lake Atnsjøen, a Norwegian subalpine lake, was studied over a period of 13 years (1985–1997). The extent to which life-history characteristics recorded on one occasion can be regarded as representative for the population was explored. We found inter-cohort variation in growth for both species; estimates of asymptotic length (L ) in ten cohorts ranged between 225–305 mm (CV = 10.5%) for brown trout and 273–301 mm (CV = 4.1%) for Arctic charr. However, this variation was much lower than inter-population variation for brown trout based on single samples from 169 populations (CV = 24.6%). In Lake Atnsjøen, annual growth increment correlated highly with the number of days warmer than 7?°C (R 2=0.60–0.89) for brown trout, and days warmer than 10?°C (R 2=0.40–0.58) for Arctic charr. Females of Arctic charr were younger at sexual maturity than males, while no such difference was found in brown trout. Generally speaking, early maturing individuals of both species grew faster, particularly from age-2 and onwards, than immature individuals. Early maturing individuals, however, were smaller at maturity than those maturing one year older. Age and size at maturity were significantly correlated with asymptotic lengths only in Arctic charr females.  相似文献   

13.
Morphology can contain valuable information about the ecological performance of reef fishes, but it has rarely been used in combination with social traits. Social behavior is known to influence the ecological role of fishes; however, the ecological basis for pairing in reef fishes is not well understood. Field observations of 2,753 individuals, in 47 species in six families of biting reef fishes (Acanthuridae, Chaetodontidae, Kyphosidae, Labridae, Pomacanthidae, Siganidae), were used in combination with six morphological measurements, to examine the morphology of fishes in different social systems. A principal components analysis of morphological traits segregated species with high proportions of pairing individuals from non-pairing species along principal component 1, explaining 40.8 % of the variation. Pairing species were characterized by large eyes, concave foreheads, pointed snouts, deep bodies, and small maximum sizes. There was a significant positive relationship between these morphological traits (i.e., scores on PC1) and the prevalence of pairing within the Chaetodontidae (r 2 = 0.59; P = 0.026), Siganidae (r 2 = 0.72; P = 0.004), and Acanthuridae (r 2 = 0.82; P < 0.001). This was consistent when traits were corrected for phylogenetic effects. No pattern was evident in the scarine Labridae (r 2 = 0.15; P = 0.17). The morphological characteristics found among pairing species suggest that pairing species share common ecological traits, including foraging for small prey items in micro-topographically complex environments such as reef crevices. These ecological traits may have played a role in the evolution of pairing behavior and subsequently led to the development of reproductive patterns based on monogamy.  相似文献   

14.
We assessed the genetic structure and diversity of Reithrodontomys spectabilis, a critically endangered, endemic rodent from Cozumel Island, México. A total of 90 individuals were trapped from September 2001 to January 2005. Microsatellite data analysis revealed high genetic diversity values: a total of 113 alleles (average 12.5 per locus), H o  = 0.78, H e  = 0.80. These high values can be related to Cozumel’s size (478 km2) and extensive native vegetation cover, factors that could be promoting a suitable population size, high heterozygosity and the persistence of rare alleles in the species, as well as some long-term movement of individuals between sampling localities. A strong genetic structure was also observed, with at least four genetic groups, associated with a pattern of isolation by distance. We found a strong allelic and genetic differentiation shown between localities, with negligible recent gene flow and low inbreeding coefficients. The species life history and ecological characteristics—being nocturnal, semi-terrestrial, a good tree climber, having lunar phobia and significant edge effect—are likely affecting its genetic structure and differentiation. The high genetic diversity and population structure award R. spectabilis a significant conservation value. Our results can serve as a basis for future research and conservation of the species, particularly considering the problems the island is facing from habitat perturbation, urbanization and introduction of exotic species. In view of the structure and genetic variability observed, it is essential to establish and reinforce protected areas and management programs for the conservation of the endemic and endangered Cozumel Harvest mice.  相似文献   

15.
16.
Knowledge of cetacean species composition and their distribution in the south-east Atlantic sector of the Southern Ocean is scarce. During a survey in February–March 2008, systematic whale sightings were carried out along transect lines following the 5° and 15° E meridians between 35° and 67° S. In total, 67 toothed whales and 126 baleen whales were observed. Both fin whales (four animals) and Antarctic minke whales Balaenoptera bonaerenses (three animals) in addition to 16 individuals of unidentified species were among the observed baleen whales. The dominating baleen whale species in our study was humpback whales Megaptera novaeangliae with 108 individuals observed. They occurred single or in groups up to seven individuals (N mean = 2.5 ind) and eight of the counts were of calves. The relationship between humpback whale occurrence and environmental variables including Antarctic krill (Euphausia superba) abundance from acoustic recordings, hydrography, bathymetry and production was tested using general additive models. Only temperature increased the predictive power of the model with whale occurrence increasing with the decreasing temperature in more southern areas.  相似文献   

17.
To estimate nodule biomass of Alnus hirsuta var. sibirica, an N2-fixing tree species, we examined the distribution pattern and size structure of nodules in a 17 to 18 year old stand naturally regenerated after disturbance by road construction in Japan. Nodules were harvested within 1 m from the outer edge of stems of plants with different sizes on four occasions from June to October. The diameter of the subtending root at the base of each nodule and nodule dry weight were measured in 20 cm increments outwards from the base of each stem. Horizontal distribution of nodules around each tree varied greatly among tree diameters at 1.3 m (dbh) within the even-aged stand. In particular, smaller individuals had a concentrated distribution of nodules close to the stem. Nodule abundance occurred further from the stems with increasing tree size. Nodule biomass within 1 m from the outer edge of individual stems increased with tree size ([nodule biomass] = 0.442 [dbh]2.01, R 2?=?0.747, P?<?0.05). By using the relationship, nodule biomasses were estimated to be 84.1 kg ha?1. These results suggest that it is necessary to take into account tree size and patterns of tree distribution in nodule biomass estimates.  相似文献   

18.
The Sinai primrose (Primula boveana) is one of the most endangered plant species worldwide, with less than 200 wild individuals surviving in the Sinai mountains of Egypt. There has been a decline in both the number and size of its populations in recent times, possibly caused by threats that include habitat aridification and the impact of human activities. Studying the standing genetic variation and extent of inbreeding of P. boveana is necessary for the design of appropriate conservation strategies for this species. In the present work, we used a set of seven, recently developed, polymorphic microsatellite markers to characterize the genetic variation and levels of inbreeding of the extant populations of P. boveana. We found low levels of genetic variation (H T = 0.470), high differentiation between populations (F ST = 0.737, R ST = 0.935), and very elevated levels of inbreeding (F = 0.862) due to recurrent selfing. These results may be the reflection of low levels of genetic variation and high levels of inbreeding over a long evolutionary period, suggesting that the current genetic pool of the species may enable P. boveana to persist in a habitat where water availability and pollinator services are restricted. Nevertheless, in sight of its rapidly dwindling abundance, it seems prudent to adopt swift measures, including habitat restoration and ex-situ conservation, to prevent the impending extinction of this emblematic species.  相似文献   

19.
We evaluated spatial variation in fish larval supply to a temperate, lagoon type estuary (Barnegat Bay, New Jersey) by determining species composition, size, and stage into inlets (n = 2), thoroughfares between adjacent estuaries (n = 3), and within the estuary (n = 4) in seasonal, synoptic sampling on night time flood tides during 2010–2014. Larval supply, as sampled with identical plankton nets (1 m diameter, 1 mm mesh) was dominated by post-flexion stage individuals (most 5–10 but reaching 70+ mm) from species spawned in the Atlantic Ocean from a variety of sources (e.g., Sargasso Sea, outer and inner continental shelf) and in the bay. While abundance for individual species varied among locations and years, in general, the larval composition was similar across inlets, thoroughfares, and within the bay within the same seasons. Homogenization across locations was likely the result of the tidal exchanges between the ocean, the estuary, and the adjacent locations. These exchanges provide numerous, redundant sources of larvae to this estuarine nursery. The similarity in larval supply among inlets, thoroughfares, and within the estuary indicates that the longer term study location behind Little Egg Inlet is representative for this, and probably other, estuaries along the New Jersey shore.  相似文献   

20.
Unravelling the mechanisms of how antibiotics influence growth performance through changes in gut microbiota can lead to the identification of highly productive microbiota in animal production. Here we investigated the effect of zinc bacitracin and avilamycin on growth performance and caecal microbiota in chickens and analysed associations between individual bacteria and growth performance. Two trials were undertaken; each used 96 individually caged 15-day-old Cobb broilers. Trial 1 had a control group (n = 48) and a zinc bacitracin (50 ppm) treatment group (n = 48). Trial 2 had a control group (n = 48) and an avilamycin (15 ppm) treatment group (n = 48). Chicken growth performance was evaluated over a 10-day period, and caecal microbiota was characterised by sequencing of bacterial 16S rRNA gene amplicons. Avilamycin produced no effect on growth performance and exhibited little significant disturbance of the microbiota structure. However, zinc bacitracin reduced the feed conversion ratio (FCR) in treated birds, changed the composition and increased the diversity of their caecal microbiota by reducing dominant species. Avilamycin only produced minor reductions in the abundance of two microbial taxa, whereas zinc bacitracin produced relatively large shifts in a number of taxa, primarily Lactobacillus species. Also, a number of phylotypes closely related to lactobacilli species were positively or negatively correlated with FCR values, suggesting contrasting effects of Lactobacillus spp. on chicken growth performance. By harnessing such bacteria, it may be possible to develop high-productivity strategies in poultry that rely on the use of probiotics and less on in-feed antibiotics.  相似文献   

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