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1.
The introduction of alien species to new environments is one of the main threats to the conservation of biodiversity. One particularly problematic example is that of wild ungulates which are increasingly being established in regions outside their natural distribution range due to human hunting interests. Unfortunately, we know little of the effects these large herbivores may have on the host ecosystems. This study deals with a first comparative analysis of the habitat requirements of two ungulate species that may be facing competition for resources in the south of Europe: the native Iberian ibex (Capra pyrenaica) and the exotic aoudad (Ammotragus lervia). The aoudad is a North African caprid introduced in 1970 as a game species in south‐eastern Spain. It has adapted well, and populations have been freely expanding since then. Ecological Niche Factor Analysis is used to describe the realized niche of both species where their distribution ranges merge. Both species occupy marginal areas of rugged terrain in the region. Marginality is higher for the Iberian ibex, which also presents a higher tolerance of secondary environmental gradients than the aoudad. Highly suitable areas for each species are secondarily suitable for the other. Reclassified and cross‐tabulated habitat suitability maps showing the areas of potential spatial coexistence and differences in ecological traits between both species are provided. The results obtained do not allow inferring resource competition between these species. However, current aoudad expansion could result in it invading the favoured habitats of the ibex. Inadequate hunting policy and monitoring, and increasing climatic resemblance of the study region to the native aoudad areas, due to a strong desertification process, are facilitating a high rate of expansion. We strongly recommend to eradicate or, at least, monitor these exotic populations, and promote active conservation practices, if one wants to preserve the unique natural resources present in this European region.  相似文献   

2.
Sargassum muticum (Yendo) Fensholt is one of the most well‐known invasive species in the world. There have, however, been few genetic investigations on both its introduced and native populations. There are also some questions about the taxonomic status of this species. This study is the first to assess the genetic diversity of S. muticum on a global scale, by utilizing one marker each from the extranuclear genomes, namely, plastidial RUBISCO and mitochondrial TrnW_I spacers, as well as the nuclear internal transcribed spacer 2 (ITS2). Based on the markers investigated, both the invasive as well as the native populations of this species appeared very homogenous, when compared with other invasive and brown macroalgae. No variation in ITS2 and RUBISCO spacer was revealed in S. muticum populations, including those from its native ranges in Asia and the introduced ranges in Europe and North America. Two TrnW_I spacer haplotypes with a fixed two‐nucleotide difference were found between the populations of eastern Japan and the other 15 populations examined. This study confirms that there is no cryptic diversity in the introduced range of this species. All the materials collected globally are indeed S. muticum. Results depicting the distribution range of the two TrnW_I spacer haplotypes also support the earlier suggestion that the source of the introduced S. muticum populations is most likely western and central Japan (Seto Inland Sea), where the germlings of S. muticum were likely to have been transported with the Pacific oysters previously introduced for farming in Canada, UK, and France in earlier years.  相似文献   

3.
Brazil has one of the greatest bird diversities in the world, with around 1,800 species. However, many species are now threatened by illegal capture and trade that is largely driven by the culture of keeping wild birds as pets. This study documents the nature and purpose of bird capture and trade in the semi-arid Caatinga biome in northeastern Brazil, which has around 510 bird species and a population of around 25 million people. Data were obtained through observation in the homes of bird keepers and at open air markets, as well as through semi-structured and open-ended interviews and informal conversations with 52 wild bird keepers. We recorded 38 species of birds kept as pets in this study. The family with the largest number of species recorded was the Emberizidae (29%), followed by the Columbidae (16%) and the Psittacidae (16%). The most frequently kept species were: Paroaria dominicana, Aratinga cactorum, Icterus jamacaii, Sporophila albogularis, Turdus rufiventris and Cyanocompsa brissonii, which are all native to this region. Among the recorded species, only Pintassilgo (Carduelis yarrellii) is listed as an endangered species in Brazil. Of the people interviewed, 32% observed a reduction in abundance, or disappearance, of several bird species in the region. The need for measures aimed at the sustainability of wild avifauna use is therefore evident. These include law enforcement, commercial breeding and environmental education, of which the last is considered the most likely to be effective.  相似文献   

4.
Climate change elevates conservation concerns worldwide because it is likely to exacerbate many identified threats to animal populations. In recent decades, grassland birds have declined faster than other North American bird species, a loss thought to be due to habitat loss and fragmentation and changing agricultural practices. Climate change poses additional threats of unknown magnitude to these already declining populations. We examined how seasonal and daily weather conditions over 10 years influenced nest survival of five species of insectivorous passerines native to the shortgrass prairie and evaluate our findings relative to future climate predictions for this region. Daily nest survival (= 870) was best predicted by a combination of daily and seasonal weather variables, age of nest, time in season and bird habitat guild. Within a season, survival rates were lower on very hot days (temperatures ≥ 35 °C), on dry days (with a lag of 1 day) and on stormy days (especially for those species nesting in shorter vegetation). Across years, survival rates were also lower during warmer and drier breeding seasons. Clutch sizes were larger when early spring temperatures were cool and the week prior to egg‐laying was wetter and warming. Climate change is likely to exacerbate grassland bird population declines because projected climate conditions include rising temperatures, more prolonged drought and more intense storms as the hydrological cycle is altered. Under varying realistic scenarios, nest success estimates were halved compared to their current average value when models both increased the temperature (3 °C) and decreased precipitation (two additional dry days during a nesting period), thus underscoring a sense of urgency in identifying and addressing the current causes of range‐wide declines.  相似文献   

5.
Hybrid zones represent natural laboratories to study gene flow, divergence and the nature of species boundaries between closely related taxa. We evaluated the level and extent of hybridization between Crocodylus moreletii and Crocodylus acutus using genetic and morphological data on 300 crocodiles from 65 localities. To our knowledge, this is the first genetic study that includes the entire historic range and sympatric zone of the two species. Contrary to expectations, Bayesian admixture proportions and maximum‐likelihood estimates of hybrid indexes revealed that most sampled crocodiles were admixed and that the hybrid zone is geographically extensive, extending well beyond their historical region of sympatry. We identified a few geographically isolated, nonadmixed populations of both parental species. Hybrids do not appear to be F1s or recent backcrosses, but rather are more likely later‐generation hybrids, suggesting that hybridization has been going on for several to many generations and is mostly the result of natural processes. Crocodylus moreletii is not the sister species of C. acutus, suggesting that the hybrid zone formed from secondary contact rather than primary divergence. Nonadmixed individuals from the two species were distinguishable based on morphological characters, whereas hybrids had a complex mosaic of morphological characters that hinders identification in the wild. Very few nonadmixed C. acutus and C. moreletii populations exist in the wild. Consequently, the last nonadmixed C. moreletii populations have become critically endangered. Indeed, not only the parental species but also the naturally occurring hybrids should be considered for their potential conservation value.  相似文献   

6.
The Tokyo bitterling Tanakia tanago (Cyprinidae) was once found throughout the Kanto Plain, central Japan, but most of their habitats have been lost due to human activities such as urbanization and improvement of paddy fields. Subsequently, conservation efforts, including captive breeding and reintroduction, have been ongoing. However, the genetic relationships among populations of this species including captive and remnant wild populations have been uncertain and thus management units for this species have been unidentified. We examined the population differentiation among 12 populations, including four wild and eight captive populations, and their relative genetic diversities to assist in conservation management decisions. Phylogeographic analyses based on partial mitochondrial cytochrome b gene sequences and microsatellite polymorphisms revealed four geographically associated genetic groups in the populations. Northern Tochigi populations have diverged from other populations (0.77% of d A ), likely stemming from allopatric fragmentation following a change in the route of the Naka River, which occurred during the middle of the Pleistocene epoch. Microsatellite analysis has revealed that the genetic diversity of each population is generally low, and that most of the populations have experienced genetic bottlenecks. For future in- and ex-situ conservation programs to succeed, the population structure and genetic variability of remnant populations need to be taken into consideration.  相似文献   

7.
Adam Britt 《Zoo biology》1998,17(5):379-392
Captive breeding of endangered species is commonly proposed as a means of conserving biodiversity. The suggestion is that captive populations can be built up to provide individuals to reinforce or re-establish wild populations. However, there is evidence to suggest that captive-bred animals lack the skills necessary for survival in their natural habitat. This research was designed to assess whether a group of captive-bred Varecia variegata variegata exhibit such behavioral deficiencies in relation to feeding behavior compared to two wild groups. A further aim was to determine which of four methods of food presentation and two captive environments were most effective in encouraging the exhibition of natural feeding behavior. An identical focal animal, instantaneous time-sampling technique was used to collect data from the wild groups in the Betampona Reserve, Madagascar, and the captive group at Chester, UK. Results from Betampona confirm the highly frugivorous and arboreal nature of V. v. variegata. Under all captive conditions, except the rooftop feed in the cage environment, the captive V. v. variegata spent significantly less time feeding than their wild conspecifics. Suspensory feeding postures are an important adaptation enabling wild V. v. variegata to harvest fruit in the small-branch setting. Similar frequencies of use of such postures to those observed at Betampona were most effectively encouraged among captive V. v. variegata in the cage environment by the rooftop food presentation method and on a naturalistic island exhibit by the suspended method of food presentation. Differences in feeding behavior between the wild and captive V. v.variegata can be explained in terms of structural differences between their environments. As naturalistic captive environments allow lemurs to experience the challenges associated with feeding in the wild, it is strongly recommended that zoos endeavor to provide them with such conditions. Zoo Biol 17:379–392, 1998. © 1998 Wiley-Liss, Inc.  相似文献   

8.
The loss of bird species following human colonization of New Zealand has raised concerns about the consequences for crucial ecosystem functions such as pollination. The understorey shrub Alseuosmia macrophylla (Alseuosmiaceae) exhibits characteristics typical of a bird pollination syndrome, but populations still persist in northern North Island forest remnants despite the local extinction of most endemic bird pollinators, leading to the suggestion that moths – rather than birds – may be the primary pollinators. The aim of this study was to quantify the importance of endemic birds as pollinators of A. macrophylla over several years by comparing plants on Little Barrier Island (LBI), where all extant endemic bird pollinators still occur, to plants at sites on the adjacent North Island in the Waitakere Ranges (WTK), where only one of these species remains common. Flowers on LBI were visited by endemic bellbirds (Anthornis melanura) and stitchbirds (Notiomystis cincta), while at WTK sites the most common visitors were the recently arrived silvereye (Zosterops lateralis) and the introduced honeybee (Apis mellifera), both of which acted principally as nectar robbers. Caged flowers on LBI had significantly lower fruit set than open flowers, and plants at WTK were significantly more pollen‐limited than plants on LBI. This provides evidence that the loss of endemic pollinating birds is the most likely reason for the high pollen limitation found in some North Island A. macrophylla populations, and the very low seed set of these populations could have serious implications for the long‐term persistence of this species.  相似文献   

9.
The genus Agapornis consists of nine small African parrot species that are globally well known as pets, but are also found in their native habitat. Illegal trapping, poaching and habitat destruction are the main threats these birds face in the wild. In aviculture, Agapornis breeding is highly popular all across the globe. Birds are mainly selected based on their plumage colour variations but very little molecular research has been conducted on this topic. There are 30 known colour variations amongst the nine species and most of these are inherited as Mendelian traits. However, to date none of the genes or polymorphisms linked to these variations have been identified or verified. Due to unethical breeding practices, the need for the development of molecular tests such as identification verification tests or species identity tests is growing. Future research is paramount to ensure the conservation of wild populations as well as aiding breeders in improving breeding strategies.  相似文献   

10.
A comprehensive understanding of spatiotemporal ecology is needed to develop conservation strategies for declining species. The king rail (Rallus elegans) is a secretive marsh bird whose range historically extended across the eastern United States. Inland migratory populations have been greatly reduced with most remaining populations inhabiting the coastal margins. Our objectives were to determine the migratory status of breeding king rails on the mid‐Atlantic coast and to characterize home range size, seasonal patterns of movement, and habitat use. Using radiotelemetry, we tracked individual king rails among seasons, and established that at least a segment of this breeding population is resident. Mean (±SE) home range size was 19.8 ± 5.0 ha (95% kernel density) or 2.5 ± 0.9 (50% kernel density). We detected seasonal variation and sex differences in home range size and habitat use. In the nonbreeding season, resident male home ranges coincided essentially with their breeding territories. Overwintering males were more likely than females to be found in natural emergent marsh with a greater area of open water. Females tended to have larger home ranges than males during the nonbreeding season. We report for the first time the use of wooded natural marsh by overwintering females. Brood‐rearing king rails led their young considerable distances away from their nests (average maximum distance: ~600 ± 200 m) and used both wooded natural and impounded marsh. King rails moved between natural marsh and managed impoundments during all life stages, but the proximity of these habitat types particularly benefitted brood‐rearing parents seeking foraging areas with shallower water in proximity to cover. Our results demonstrate the importance of interspersion of habitat types to support resident breeders. Summer draining of impounded wetlands that are seasonally flooded for wintering waterfowl allows regrowth of vegetation and provides additional habitat at a critical time for wading birds.  相似文献   

11.
A growing body of evidence indicates that second‐generation energy crops can play an important role in the development of renewable energy and the mitigation of climate change. However, dedicated energy crops have yet to be domesticated in order to fully realize their productive potential under unfavorable soil and climatic conditions. To explore the possibility of domesticating Miscanthus crops in northern China where marginal and degraded land is abundant, we conducted common garden experiments at multiple locations to evaluate variation and adaptation of three Miscanthus species that are likely to serve as the wild progenitors of the energy crops. A total of 93 populations of Miscanthus sinensis, Miscanthus sacchariflorus, and Miscanthus lutarioriparius were collected across their natural distributional ranges in China and grown in three locations that represent temperate grassland with cold winter, the semiarid Loess Plateau, and relatively warm and wet central China. Evaluated with growth traits such as plant height, tiller number, tiller diameter, and flowering time, the Miscanthus species showed high levels of genetic variation within and between species. There were significant site × population interactions for almost all traits of M. sacchariflorus and M. sinensis, but not M. lutarioriparius. The northern populations of M. sacchariflorus had the highest establishment rates at the most northern site owing to their strong cold tolerance. An endemic species in central China, M. lutarioriparius, produced not only the highest biomass of the three species but also higher biomass at the Loess Plateau than the southern site near its native habitats. These results demonstrated that the wild species harbored a high level of genetic variation underlying traits important for crop establishment and production at sites that are colder and drier than their native habitats. The natural variation and adaptive plasticity found in the Miscanthus species indicated that they could provide valuable resources for the development of second‐generation energy crops.  相似文献   

12.
G. Beven 《Ostrich》2013,84(1):65-73
The genus Poicephalus is one of four genera of parrots found on the African continent. However, little is known about this group of parrots as few studies have been undertaken in the wild and they remain one of the least studied groups of parrots. Decisions on their conservation status and determining appropriate trade quotas are often based on very limited information. Observing and collecting ecological and behavioural data on parrots in their natural habitat is difficult and accordingly the data from wild populations are limited. Genetic markers provide a potential method to obtain data on a species’ ecology, e.g. effective population size and reproductive behaviour, which can assist conservation management. However, developing or screening genetic markers for such investigations can be costly and time consuming and is not guaranteed; these constraints may deter researchers from considering or including them in proposals. This study has characterised 17 microsatellite loci across most species of the African Poicephalus parrots in order to encourage researchers to collect samples and/or to develop genetic studies for Poicephalus parrots. Additional knowledge from wild populations will benefit these little-known parrots.  相似文献   

13.
Genomic introgression through interspecific hybridization has been observed in some species of the freshwater fish family Cobitidae. Within this family, a Cobitis hankugensisIksookimia longicorpa diploid–triploid hybrid species complex on the Korean peninsula is unique in displaying hybridogenesis, a unisexual reproduction mode that allows hybrids to mediate the transfer of mitochondrial DNA (but not nuclear DNA) between the two parent species. However, populations of the parental species in the wild have never been examined for the potential effect of introgression on their genomes. To address the genetic consequences of unisexual hybridization on the parental species, we examined genetic structure of the two parental species, C. hankugensis and I. longicorpa, in three independent natural habitats where they coexist with their hybrid complex using DNA sequence data of one mitochondrial gene and three nuclear genes. We found that mitochondrial introgression between the two species was extensive in all the examined localities, while there was no evidence of nuclear introgression across the species boundary. This result indicates that the hybridogenetic individuals mediate mitochondrial introgression from one species to the other, producing mito‐nuclear mosaic genomes such as C. hankugensis nuclear genomes associated with I. longicorpa mitochondrial DNA and the reverse. The direction and degree of introgression varied among the three localities, but the underlying mechanisms for this observation proved elusive. Introgression might depend on which species serves as the predominant sperm or ovum donor or the environmental conditions of the localities. The present study suggests that introgressive hybridization between pure C. hankugensis and I. longicorpa species is highly likely where the two species co‐occur with hybridogenetic individuals, but the consequence of introgression could be variable due to the history and environmental characteristics of particular populations across the parental species’ ranges.  相似文献   

14.
The mite Ornithonyssus bursa (Berlese) (Mesostigmata: Macronyssidae) is considered a poultry pest causing important infestations in chickens and it is considered a potential vector of arbovirus. Despite being considered a common parasite in wild birds, there is scarce published information about its potential hosts and effects on them. Here we present new bird hosts for O. bursa, assess the presence of Alphavirus, Flavivirus and Bunyavirus in mites from three host species, and discuss its potential impact on wild bird populations. We found O. bursa infecting five raptor and six passerine wild bird species. For nine of these species, this is the first record of infection by O. bursa. Although all analysed mites were negative for the examined arboviruses, the small sample size of mites does not allow further conclusions at the present moment. Because of the general nature of this ectoparasite, its presence in migratory long dispersal and endangered bird species, and the seropositivity for arboviruses in some of the species studied here, we consider it critical to assess the role of O. bursa and other ectoparasites as vectors and reservoirs of pathogens and as potential deleterious agents in wild bird populations.  相似文献   

15.
Native bird species show latitudinal gradients in body size across species (Bergmann's rule), but whether or not such gradients are recapitulated in the alien distributions of bird species are unknown. Here, we test for the existence of Bergmann's rule in alien bird species worldwide, and investigate the causes of the observed patterns. Published databases were used to obtain the worldwide distributions of established alien bird populations, the locations of alien bird introductions, and bird body masses. Randomisation tests and linear models were used to assess latitudinal patterns in the body masses of introduced and established alien bird populations. Established alien bird species exhibit Bergmann's rule, but this is largely explained by where alien bird species have been introduced: latitudinal variation in the body masses of established alien bird species simply reflects latitudinal variation in the body masses of introduced species. There is some evidence that body mass is implicated in whether or not established species’ alien ranges spread towards or contract away from the Equator following establishment. However, most alien bird ranges are encompassed by the latitudinal band(s) to which the species was introduced. Bergmann's rule in alien birds is therefore a consequence of where humans have introduced different species, rather than of natural processes operating after population introduction.  相似文献   

16.
The genetic effects of population bottlenecks have been well studied theoretically, in laboratory studies, and to some extent, in natural situations. The effects of serial population bottlenecks (SPBs), however, are less well understood. This is significant because recurrent population bottlenecks are likely to be a common feature of the life history of many species. The lack of understanding of SPBs in natural populations has certainly been hampered by a lack of good examples where it can be studied. We report the results of a study into island populations of North Island Saddleback (Philesturnus carunculatus rufusater) that have undergone 13 translocations since 1964, all but one of these has been deliberate and for which detailed records are available. We have examined nine island populations of this passerine bird, from the source population, three first-order bottlenecked and five second-order bottlenecked populations. We examine variation in these nine populations using multilocus minisatellite DNA markers, together with Mendelian loci comprising six microsatellite DNA loci and a variable isozyme locus. Despite the generally low level of genetic variation in the Saddleback source population, we were able to detect a pattern of significant changes in both the mean number of minisatellite DNA bands per individual and the frequency of alleles at the Mendelian loci, with increasing population bottlenecks. This study generally shows that in a natural population, SPBs result in more pronounced genetic changes than do single population bottlenecks by themselves, thereby highlighting their importance for the conservation of rare and endangered species.  相似文献   

17.
Global warming is predicted to cause substantial habitat rearrangements, with the most severe effects expected to occur in high‐latitude biomes. However, one major uncertainty is whether species will be able to shift their ranges to keep pace with climate‐driven environmental changes. Many recent studies on mammals have shown that past range contractions have been associated with local extinctions rather than survival by habitat tracking. Here, we have used an interdisciplinary approach that combines ancient DNA techniques, coalescent simulations and species distribution modelling, to investigate how two common cold‐adapted bird species, willow and rock ptarmigan (Lagopus lagopus and Lagopus muta), respond to long‐term climate warming. Contrary to previous findings in mammals, we demonstrate a genetic continuity in Europe over the last 20 millennia. Results from back‐casted species distribution models suggest that this continuity may have been facilitated by uninterrupted habitat availability and potentially also the greater dispersal ability of birds. However, our predictions show that in the near future, some isolated regions will have little suitable habitat left, implying a future decrease in local populations at a scale unprecedented since the last glacial maximum.  相似文献   

18.
Zoonotic pathogens often infect several animal species, and gene flow among populations infecting different host species may affect the biological traits of the pathogen including host specificity, transmissibility and virulence. The bacterium Campylobacter jejuni is a widespread zoonotic multihost pathogen, which frequently causes gastroenteritis in humans. Poultry products are important transmission vehicles to humans, but the bacterium is common in other domestic and wild animals, particularly birds, which are a potential infection source. Population genetic studies of C. jejuni have mainly investigated isolates from humans and domestic animals, so to assess C. jejuni population structure more broadly and investigate host adaptation, 928 wild bird isolates from Europe and Australia were genotyped by multilocus sequencing and compared to the genotypes recovered from 1366 domestic animal and human isolates. Campylobacter jejuni populations from different wild bird species were distinct from each other and from those from domestic animals and humans, and the host species of wild bird was the major determinant of C. jejuni genotype, while geographic origin was of little importance. By comparison, C. jejuni differentiation was restricted between more phylogenetically diverse farm animals, indicating that domesticated animals may represent a novel niche for C. jejuni and thereby driving the evolution of those bacteria as they exploit this niche. Human disease is dominated by isolates from this novel domesticated animal niche.  相似文献   

19.
Malaria caused by Plasmodium parasites is one of the worst scourges of mankind and threatens wild animal populations. Therefore, identifying mechanisms that mediate the spread of the disease is crucial for both human health and conservation. Human‐induced climate change has been hypothesized to alter the geographic distribution of malaria pathogens. As the earth warms, arthropod vectors may display a general range expansion or may enjoy longer breeding season, both of which can enhance parasite transmission. Moreover, Plasmodium species may directly benefit for elevating temperatures, which provide stimulating conditions for parasite reproduction. To test for the link between climate change and malaria prevalence on a global scale for the first time, I used long‐term records on avian malaria, which is a key model for studying the dynamics of naturally occurring malarial infections. Following the variation in parasite prevalence in more than 3000 bird species over seven decades, I show that the infection rate by Plasmodium is strongly associated with temperature anomalies and has been augmented with accelerating tendency during the last 20 years. The impact of climate change on malaria prevalence varies across continents, with the strongest effects found for Europe and Africa. Migration habit did not predict susceptibility to the escalating parasite pressure by Plasmodium. Consequently, wild birds are at an increasing risk of malaria infection due to recent climate change, which can endanger both naïve bird populations and domesticated animals. The prevailing avian example may provide useful lessons for understanding the effect of climate change on malaria in humans.  相似文献   

20.
Quantitative genetic studies in natural populations are of growing interest to speciation research since divergence is often believed to arise through micro-evolutionary change, caused by natural selection on functional morphological traits. The species flock of cichlid fishes in Africa’s oldest lake, Lake Tanganyika, offers a rare opportunity to study this process. Using the cichlid species Tropheus moorii, we assessed the potential for microevolution in a set of morphological traits by estimating their quantitative genetic basis of variation. Two approaches were employed: (1) estimation of trait heritabilities (h 2) in situ from a sample of wild caught fish, and (2) estimation of h 2 from first generation offspring produced in a semi-natural breeding experiment. In both cases, microsatellite data were used to infer pedigree structure among the sampled individuals and estimates of h 2 were made using an animal model approach. Although power was limited by the pedigree structures estimated (particularly in the wild caught sample), we nonetheless demonstrate the presence of significant additive genetic variance for aspects of morphology that, in the cichlid species Tropheus moorii, are expected to be functionally and ecologically important, and therefore likely targets of natural selection. We hypothesize that traits showing significant additive genetic variance, such as the mouth position have most likely played a key role in the adaptive evolution of the cichlid fish Tropheus moorii.  相似文献   

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