Between‐lake variation in the trophic ecology of an invasive crayfish

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我国特有珍稀植物翅果油树濒危原因分析

翅果油树是我国特有种,为国家2级珍稀濒危保护植物,主要分布于山西南部的低山和丘陵区以及陕西秦岭北麓的户县。翅果油树分布区的生态环境特征是：热量充足,降水量较少,立地条件较差。翅果油树濒危的主要原因有（1）果实形态结构特殊,不利于传播和萌发,（2）果实结实率较低,（3）种子寿命短,发芽率低,（4）翅果油树幼苗缺乏竞争力和（5）人力破坏严重。此外,针对翅果油树的濒危现状和原因,还提出了科学保护对策。     

Reproductive ecology and the persistence of an endangered plant

Amsinckia grandiflora (large-flowered fiddleneck)is an extremely rare California annual wildflower, known only from threepopulations. We conducted field and greenhouse experiments to compare the rareheterostyle with a cryptic self-incompatibility system (A.grandiflora) to a common, self-compatible, homostylous, sympatriccongener (A. tessellata). Inter-species comparisons ofadult plants suggested that in the greenhouse, A.grandiflora balances low floral seed set (seeds per flower) withincreased floral output (flowers/plant) and a greater number of flowers perinflorescence. Seed set from active self-, intra- and inter-morph pollinationswas high in A. grandiflora, indicating that the crypticself-incompatibility system does not prevent seed set in the species. In thefield, A. grandiflora floral output was only slightlygreater than for A. tessellata, and did not fully balance lowerfloral seed set. Amsinckia tessellata average seed weightwas lower than that of A. grandiflora, which, along with the lowernumber of flowers produced, indicated lower maternal investment per nutlet thanfor A. grandiflora. Under conditions of unlimited resources, itappears that A. grandiflora fitness is not intrinsicallylimited when compared to its weedy relative A. tessellata.The differences in nutlet output between A. grandiflora andA. tessellata under field conditions are more likely due todifferential responses to extrinsic factors such as competition and pollinatoravailability.     

The ecology of Hypogeomys antimena, an endemic Madagascan rodent

The subfamily Nesomyinae comprises 11 species of rodents endemic to the island of Madagascar. They show considerable ecological and anatomical diversity but little is known of their biology and they have not been studied to any extent in the wild. We present here the results of a nine-week field study of Hypogeomys antimena , the largest of the Nesomyinae, found only in a restricted area of dry deciduous forest in western Madagascar. Radiotracking data gave a mean home range estimate of 3.5+0.71 ha for 10 animals (five males, five females). Individuals from the same burrow had highly overlapping ranges but ranges of animals from neighbouring burrows showed minimal overlap. We suggest that H. antimena lives in social units, probably consisting of a pair plus their offspring, which occupy exclusive territories. A mark/recapture study gave a minimum population estimate of 48 animals/km² in the study site. The conservation of the species is discussed with reference to its limited distribution and current habitat degradation in the area.     

Multilocus phylogeography of the endemic and endangered angular angelshark (Squatina guggenheim) in the Southwest Atlantic Ocean

Hydrobiologia - The angular angelshark (Squatina guggenheim) is a coastal endangered angel shark from the Southwest Atlantic Ocean and one of the major bycatch victims. Despite major concerns about...     

Community structure and coexistence of the rotifers of an artificial crater lake

Hydrobiologia - The community structure and dynamics of the rotifers of an abandoned and inundated limestone quarry are described. Zooplankton standing crop is low, but the community is rich in...     

Population genetics and phylogeography of endangered Oxytropis campestris var. chartacea and relatives: arctic-alpine disjuncts in eastern North America

Fassett's locoweed (Oxytropis campestris var. chartacea, Fabaceae) is an endangered perennial endemic to Wisconsin. Patterns of genetic variation within and among six remaining populations and their relationship to other members of the O. campestris complex were analysed using AFLPs from 140 accessions across northern North America. Within-population measures of genetic diversity were high (mean expected heterozygosity HE = 0.16; mean nucleotide diversity pi = 0.015) compared with other herbaceous plants. Estimates of among-population differentiation were low (FST = 0.12; PhiST = 0.29), consistent with outcrossing. Genetic and geographical distances between populations were significantly correlated within Fassett's locoweed (r2 = 0.73, P < 0.002 for Mantel test) and O. campestris as a whole (r2 = 0.63, P < 0.0001). Individual and population-based phylogenetic analyses showed that Fassett's locoweed is monophyletic and sister to O. campestris var. johannensis. Morphometric analyses revealed significant differences between Fassett's locoweed and populations of var. johannensis. The first chromosome count for Fassett's locoweed indicates that it is tetraploid (2n = 32), unlike hexaploid var. johannensis. High within-population diversity and relatively low among-population differentiation are consistent with populations of Fassett's locoweed being relicts of a more continuous Pleistocene distribution. Our data support the continued recognition of Fassett's locoweed and protection under federal and state regulations. High levels of genetic diversity within populations suggest that maintain-ing the ecological conditions that favour the life cycle of this plant may be a more pressing concern than the erosion of genetic variation.     

Seedling recruitment and survival of an endangered limestone endemic in its natural habitat and experimental reintroduction sites

The largest and most fecund population of the endangered Purshia subintegra is restricted to limestone mesas in Verde Valley, Arizona, USA, where habitat destruction is imminent. To examine factors limiting its distribution and potential for expansion, we compared recruitment and survival of seedlings growing in soils from occupied and unoccupied habitat in caged field experiments and compared survival of caged and wild seedling cohorts from 1998 to 2003. In field tests, seeds germinated in soils from occupied and unoccupied habitats. Seedling survival, however, was greatest in currently occupied habitat and dropped to zero in some unoccupied habitats with the onset of severe drought. Among 16 factors measured, soil moisture significantly explained between 62% and 71% of the variation in recruitment in both wild and caged plots. Shrubs conferred protection to wild seedlings, but decreased caged seedling survival. For 5 yr following germination, caged seedlings had greater survival than natural seedling cohorts indicating that reintroduction was comparatively more successful than natural recruitment. Expansion of P. subintegra into novel habitats is limited by soil moisture capacity, and this condition varied during the experimental time frame. Reintroductions to limestone mesas are possible and most promising if cages and supplemental watering are used.     

Seasonality in diet and feeding habits of the endemic Chala tilapia (Oreochromis hunteri) and two introduced tilapiine cichlids in Lake Chala,East Africa

Hydrobiologia - Oreochromis cf. korogwe and Coptodon rendalli, two tilapiine fishes introduced to Lake Chala (Kenya/Tanzania) ~?40&nbsp;years ago, may negatively affect the endemic Chala...     

Endemic species may have complex histories: within‐refugium phylogeography of an endangered Iberian vole

Glacial refugia protected and promoted biodiversity during the Pleistocene, not only at a broader scale, but also for many endemics that contracted and expanded their ranges within refugial areas. Understanding the evolutionary history of refugial endemics is especially important in the case of endangered species to recognize the origins of their genetic structure and thus produce better informed conservation practices. The Iberian Peninsula is an important European glacial refugium, rich in endemics of conservation concern, including small mammals, such as the Cabrera vole (Microtus cabrerae). This near‐threatened rodent is characterized by an unusual suite of genetic, life history and ecological traits, being restricted to isolated geographic nuclei in fast‐disappearing Mediterranean subhumid herbaceous habitats. To reconstruct the evolutionary history of the Cabrera vole, we studied sequence variation at mitochondrial, autosomal and sex‐linked loci, using invasive and noninvasive samples. Despite low overall mitochondrial and nuclear nucleotide diversities, we observed two main well‐supported mitochondrial lineages, west and east. Phylogeographic modelling in the context of the Cabrera vole's detailed fossil record supports a demographic scenario of isolation of two populations during the Last Glacial Maximum from a single focus in the southern part of the Iberian Peninsula. In addition, our data suggest subsequent divergence within the east, and secondary contact and introgression of the expanding western population, during the late Holocene. This work emphasizes that refugial endemics may have a phylogeographic history as rich as that of more widespread species, and conservation of such endemics includes the preservation of that genetic legacy.     

濒危植物矮牡丹致濒原因分析

矮牡丹是我国特有种,为国家3级濒危保护植物。仅分布于山西南部(稷山和永济)和陕西中北部(华山、铜川和延安)。矮牡丹分布区的生态环境特征是：热量条件较好,降水量较少,立地条件较差。在落叶阔叶林和落叶阔叶灌丛中,矮牡丹往往多为伴生成分。偶尔可成为灌木层的优势种。矮牡丹濒危的主要原因有：(1)开花和结实率较低,产生的种子较少;(2)种子的特殊休眠特性导致萌发率较低;(3)生长发育缓慢;(4)竞争能力较弱和(5)人为干扰严重。此外。针对矮牡丹的濒危现状和原因,还提出了科学保护对策。     

The cytotaxonomy and origin ofRanunculus yaegatakensis,an endemic taxon of Yakushima Island

Ranunculus yaegatakensis, a close relative of the widespreadR. silerifolius, is endemic to the alpine region (ca. 1,600 m alt.) of Yakushima Island. This species differs morphologically fromRanunculus silerifolius mainly due to its dwarfism and leaf shape, but has an identical karyotype with one (Karatsu-type) of the four cytotype ofR. silerifolius. Ranunculus yaegatakensis is highly cross-compatible with the Karatsu-type plants ofR. silerifolius. Their F₁ hybrids show regular meiotic behaviors and set seeds successfully. In addition, the Karatsu-type ofRanunculus silerifolius is found in individuals that are collected not only from the lowland of Yakushima Island but from its neighboring islands. It is supposed to be more specialized than other cytotypes. This evidence suggests thatRanunculus yaegatakensis has been derived from the Karatsu-type plants ofR. silerifolius. We suggest thatRanunculus yaegatakensis be reduced to a variety ofR. silerifolius.     

The late Pleistocene desiccation of Lake Victoria and the origin of its endemic biota

A brief review is provided in some advances in understanding the ecology of pike Esox lucius Linnaeus over the last 10 years. Based on long-term studies and manipulative, often short-term experiments (laboratory, field and mesocosms) several established theories have been supported, as well as new concepts developed. Despite their wide distribution pike show low levels of polymorphism and divergence indicative of a recent common ancestral population. Recent genetic studies, however, indicate a single refugium in North America compared to several refugia in Europe. Pike are found in rivers, lakes and weakly saline waters. Variables such as growth and mortality are mainly affected by factors such as temperature, water transparency, productivity, availability of prey and density of pike and other predators. In choice of habitat pike have been shown to support the ideal free-distribution theory. The importance of macrophyte habitat in the life history of pike has been reconfirmed and pike have been shown to be flexible in response to water clarity. Pike are extremely ‘plastic’ in choice of prey types, prey size and in response to prey behaviour (e.g. they are unaffected by shoal size). Predation by pike not only affects abundance and biomass of prey (including younger and smaller pike through cannibalism which plays a major role in population dynamics, other fishes and invertebrates) but also evolution and adaptation of their morphology (in particular body shape) and behaviours. There appears to be no relationship between stock and recruitment. Recruitment is influenced by several abiotic factors in lakes and rivers. Pike play a major role in structuring freshwater communities and have been used in stocking programmes to improve water quality (biomanipulation). Many new concepts have been developed in pike behaviour in maximizing these stocking programmes both in biomanipulation and fisheries management. Despite many recent advances in understanding the ecology of pike, particularly at the individual level, developments in quantifying and modelling the role of pike as a top predator in large ecosystems have been limited, probably due to the difficulties of sampling natural populations. Guest editors: J. M. Farrell, C. Skov, M. Mingelbier, T. Margenau & J. E. Cooper International Pike Symposium: Merging Knowledge of Ecology, Biology, and Management for a Circumpolar Species     

Conservation genetics and ecology of an endemic montane palm on Lord Howe Island and its potential for resilience

Lepidorrhachis mooreana (Arecaceae) is a monotypic palm genus endemic to the remote Lord Howe Island where it is restricted to a small area of cloud forest above 750 m that is likely to be vulnerable to climate change. We investigated genetic diversity and key demographic parameters to assess the palm’s potential long term viability including possible climate change impacts. The palm was found on only one of the island’s two mountain summits, where the sampled sites were effectively behaving as one panmictic population. The moderate genetic diversity found indicates some adaptive potential for L. mooreana. The population was effectively inbred. Large numbers of fruit are produced, but successful juvenile recruitment is limited by predation by introduced rats. The relatively large population size increases the potential for selection for adaptation to a changing climate.     

濒危植物南方红豆杉濒危原因分析

南方红豆杉是我国第三纪孑遗特有树种,为国家1级濒危保护植物,主要分布于在长江流域、南岭山脉以及广东、广西、江西、河南、陕西、甘肃、台湾和山西等省（区）的山地。南方红豆杉分布区的生态环境特征是：热量充足,温暖潮湿。南方红豆杉濒危的主要原因有：（1）种子产生量少,萌发率和幼苗成活率较低（2）种群缺乏较强的竞争力,（3）地理分布的局限性,（4）对生境要求的特殊性和（5）人为破坏严重。此外,针对南方红豆杉濒危现状和原因,还提出了科学保护和可持续利用的对策。     

Conservation genetics of an endemic and endangered epiphytic Laelia speciosa (Orchidaceae)

We used isozymes (16 loci in 11 enzymatic systems) from Laelia speciosa, an endemic and endangered epiphytic orchid of Mexico, to assess the genetic diversity and population genetic structure in nine populations distributed along its geographic range, as well as to detect those populations that are genetically unique and therefore deserve high-priority protection. On average, the genetic diversity was high (percentage of polymorphic loci, P(p) = 76%, mean number of alleles per locus, A = 3.34, the average observed heterozygosity H(O) = 0.302, the average expected heterozygosity H(E) = 0.382). Moderate levels of inbreeding (?f = 0.216, 95% confidence interval = 0.029-0.381) were found. Low levels of genetic differentiation were observed among populations ((p) = 0.040); however, there was a significant correlation between geographic and genetic distances among the populations (Mantel test: r(2) = 0.43, P < 0.05). Populations located within the same mountain range were genetically more similar. Private alleles were found, so proper management requires protection and maintenance of genetic diversity throughout its range. In case of reintroduction, we suggest using individuals propagated from seeds from as many capsules as possible, from close populations. An ex situ conservation strategy also is proposed.     

Micropropagation of Turbinicarpus laui Glass et Foster, an endemic and endangered species

Summary In a short period of time, a large number of adventitious shoots were regenerated from longitudinal sections of in vitro-germinated seedlings of the endangered Mexican cactus, Turbinicarpus laui. The induction medium consisted of Murashige and Skoog salts, supplemented with 6-benzylaminopurine (BA) and α-naphthaleneacetic acid (NAA) in a wide range of combinations. The most effective concentrations of growth regulators for shoots initiation were 8.8–13.32 μM BA with 0–2.68 μM NAA. After 3–4 mo., individualized shoots were rooted on half-strength Murashige and Skoog medium and then transferred to soil to acclimatize under greenhouse conditions. In vitro strategies play a key role in the conservation and propagation of this commercially important endangered species of cactus.     

The role of salinity tolerance and competition in the distribution of an endangered desert salt marsh endemic

Rare plants are often associated with distinctive soil types, and understanding why endemic species occur in unique environments is fundamental for their management. At Ash Meadows National Wildlife Refuge in southern Nevada, USA, we evaluated whether the limited distribution of endangered Amargosa niterwort (Nitrophila mohavensis) is explained by this species’ tolerance of saline soils on salt-encrusted mud flats compared with the broadly distributed desert saltgrass (Distichlis spicata var. stricta). We simultaneously explored whether niterwort distribution is restricted from expanding due to interspecific competition with saltgrass. Surface soils collected throughout niterwort’s range were unexpectedly less saline with lower extractable Na, seasonal electroconductivity, and Na absorption ratio, and higher soil moisture than in adjacent saltgrass or mixed shrub habitats. Comparison of niterwort and saltgrass growth along an experimental salinity gradient in a greenhouse demonstrated lower growth of niterwort at all but the highest NaCl concentrations. Although growth of niterwort ramets was similar when transplanted into both habitats at the refuge below Crystal Reservoir, niterwort reproductive effort was considerably higher in saltgrass compared to its own habitat, implying reallocation of resources to sexual reproduction to maximize fitness when the probability of ramet mortality increases with greater salinity stress. Saltgrass was not a demonstrated direct competitor of niterwort; however, this species is known to increase soil salinity by exuding salt ions and through litterfall. Niterwort conservation will benefit from protecting hydrological processes that reduce salinity stress and preventing saltgrass colonization into niterwort habitat.     

Drosophyllum lusitanicum, an endangered West Mediterranean endemic carnivorous plant: threats and its ability to control available resources

Drosophyllum lusitanicum (L.) Link (Droseraceae), Erva pinheira orvalhada, an endangered carnivorous plant, is a local endemic of clearings in pine, cork oak and oak forests or their successional shrublands in the western Iberian Peninsula and Morocco. The conservation status, distribution and population dynamics of this species are only partially known, both for Spanish and Portuguese occurrences. Portuguese distribution data from herbarium and bibliographic sources were collected for this study. Field work on 50 populations was undertaken in order to improve knowledge on their conservation status and possible threats. Natural causes, infrastructure and housing construction are stressed as the most important threats. Germination tests were carried out and the distribution patterns, plant height and the number of flowers were studied in an arbitrarily chosen population. A relatively high light requirement and low competitive ability to gain light are considered factors likely for the microdistribution pattern. Drosophyllum lusitanicum cannot compete for light in habitats with intense competition. Seeds from D. lusitanicum have reduced probability of germination when adult plants are already growing in the area. It is hypothesized that seed germination shows a similar pattern to flowering, viz over a considerable time rather than in a sudden flush. This strategy may be a key factor for the species' survival, representing attempts to take advantage of available resources, preventing intraspecific competition and, finally, preventing sudden total disappearance of a population, resulting from any catastrophic events due to natural causes or to human activity. As a result of this study, some conservation measures are suggested.   © The Linnean Society of London, Botanical Journal of the Linnean Society , 2002, 140 , 383–390.     

Variation in the thermal ecology of an endemic iguana from Mexico reduces its vulnerability to global warming

The persistence of reptile populations in a specific location is influenced by individuals’ capacity to regulate their body temperatures, among other factors. Anthropogenic climate change may pose a risk to the survival of ectothermic animals due to their dependence on external heat sources to thermoregulate. In this study, we calculated indices of thermal habitat quality, thermoregulatory precision, and thermoregulatory effectiveness for the endemic spiny-tailed iguana Ctenosaura oaxacana. We evaluated these indices and the thermoregulatory behavior of the iguanas in the four types of vegetation that provide the most favorable conditions for thermoregulation. We also performed our experiments during both the wet and dry seasons to capture the full range of thermal conditions available to C. oaxacana over the course of a year. Finally, we evaluated the potential niche for the iguana in the years 2020, 2050, and 2080. Thermoregulation depends on both seasonal and environmental factors in this species. We found that thermoregulation effectiveness in both wet and dry seasons depends not only on the thermal conditions of the immediate environment, but also on the cover vegetation and habitat structure available across the range of habitats the species uses. Thus, heterogeneous habitats with dispersed vegetation may be most suitable for this species’ thermoregulatory strategy. Likewise, niche modeling results suggested that suitable habitat for our study species may continue to be available for the next few decades, despite global warming tendencies, as long as cover vegetation remains unaltered. Our results suggest that thermoregulation is a complex process that cannot be generalized for all ectothermic species inhabiting a given region. We also found that temperature changes are not the only factor one must consider when estimating the risk of species loss. To understand the necessary thermal conditions and extinction risk for any ectothermic species, it is necessary to focus studies on the species’ general ecology.