Genetic structure of two endangered pitcher plants,Sarracenia jonesii and Sarracenia oreophila (sarraceniaceae)

Sarracenia jonesii and S. oreophila arc insectivorous perennial plants of the southeastern United States. Both pitcher plant taxa arc rare and endangered. Allozyme diversity was assessed for eight of the ten extant populations of S. jonesii and 14 of the 35 remaining S. oreophila populations. Genetic diversity was low and comparable for both species (H_es = 0.086 and 0.082 for S. jonesii and S. oreophila, respectively). Mean population genic diversity (H_ep) was 0.061 for S. jonesii and 0.060 for S. oreophila. Estimates of genetic diversity were typical of those commonly associated with endemic species. Small populations of each species and geographically disjunct populations tended to maintain less genetic diversity. Indirect estimates of gene flow were comparable for S. oreophila (Nm = 1.62) and S. jonesii (Nm = 1.07).     

Efficiency of insect capture by Sarracenia purpurea (Sarraceniaceae), the northern pitcher plant

Pitcher plants (Sarracenia purpurea L.) attract insects to pitchers and then capture them in fluid-filled, pitfall traps, but how efficient are pitcher plants at capturing prey in their natural environment? We monitored insect activity by videotaping pitchers and analyzing videotapes for several variables including identity of each visitor and outcome of each visit (e.g., departure or capture). Efficiency of capture (i.e., number of captures per number of visits) was low. Overall efficiency of capture was 0.83–0.93%, depending on whether potential prey were broadly or narrowly defined. Ants constituted 74% of the potential prey. Efficiency of capture of ants was even lower at 0.37%. Potential prey were more likely to visit pitchers with greater red venation and less water in the pitcher. There was no correlation between number of potential prey visiting a pitcher and pitcher age, length, or mouth width. Also, number of potential prey visits did not correlate with plant size, air temperature, time of day or date of videotaping. While the overall efficiency of prey capture was very low, pitcher plants may still benefit from the additional nutrients. However, the relationship between ants and S. purpurea remains an enigma, since it is unclear whether the plants capture enough ants to compensate for nectar lost to ants.     

Inbreeding, outbreeding, and heterosis in the yellow pitcher plant, Sarracenia flava (Sarraceniaceae), in Virginia

The yellow pitcher plant, Sarracenia flava, is an insectivorous plant restricted to fire-maintained wetland ecosystems in southeastern Virginia. Only four natural sites remain in the state totaling fewer than 100 clumps. Plants from sites located in Dinwiddie, Greensville, Prince George, Sussex counties, and the city of Suffolk were tested for the effects of self-pollination, intrasite outcrossing, and intersite outcrossing on offspring quantity (total seed number and total seed mass) and offspring quality (avarage seed mass, germination, and growth).Self-pollination resulted in significantly lower offspring quantity and quality. Total seed number and total seed mass for self-pollinated capsules were approximately one-fourth that of outcrossed capsules. Germination, survivorship, and growth over 5 yr were also significantly lower for offspring from self-pollinated capsules. Together, these results suggest strong inbreeding depression in this species.Relative to offspring from intrasite crosses, offspring from intersite crosses were significantly larger after 5 yr of growth. This suggests that restoration efforts for Virginia S. flava will be most successful when plants from multiple sites are used.     

Short-term effects of fire and competition on growth and plasticity of the yellow pitcher plant,Sarracenia alata (Sarraceniaceae)

Although recurrent fires are widely assumed to reduce competitive interference of plants of pine savannas, rarely has this assumption been tested explicitly. This 2-yr study reports on the interactive effects of fire and neighbors on short-term growth responses and plasticity in allocation patterns of a carnivorous plant, the yellow pitcher plant, Sarracenia alata. This species relies upon pitfall traps (pitchers) to attract and capture insects to obtain nutrients. Neighbors reduced the growth rate of individual ramet transplants (phytometers) in one but not both years of the study. The effect of neighbors on total (i.e., both above- and belowground) productivity of phytometers was not reduced by a winter fire. Neighbors had a greater effect on large plants than on small plants. Although fire did not affect the growth rate of phytometers in the short term, allocation patterns were greatly altered by both neighbors and fire. Allocation to pitchers increased at the expense of belowground organs following fire and in the absence of neighbors at the unburned site. Results of the current study suggest that adult pitcher plants may tolerate competition from neighboring vegetation by reducing allocation to costly pitchers during years without fire.     

Development of microalgae communities in the Phytotelmata of allochthonous populations of Sarracenia purpurea (Sarraceniaceae)

The phytotelmata of the North American pitcher plant Sarracenia purpurea are colonised by a great variety of aquatic organisms and, thus, provide an ideal model to study trophic interactions in small freshwater ecosystems. Although algae are discussed as a potential food source for predators, little is known about the structure of algae coenoses in pitchers of S. purpurea. This study aims to elucidate temporal shifts in the algae community structure in pitchers of an allochthonous population of S. purpurea in Saxony, Germany. A total of 78 algae taxa was found in the pitchers. Mean algae abundances in new and old pitchers were similar (2.6 x 10(5) and 2.3 x 10(5) algae ml(-1), respectively). Taxa from the orders Chlamydomonadales, Chlorococcales, and Ochromonadales were the primary colonisers. With increasing age of the pitchers the filamentous green algae from the order Klebsormidiales became more abundant. In contrast, pennate diatoms dominated the algae coenoses in the fen. Algae community structure in vase-shaped 50 ml Greiner tubes was similar to those of natural pitchers. Differences in the temporal patterns of algae coenoses in individual pitchers suggested a colonisation of the pitchers by algae via trapped insects, air and rain water rather than via the surrounding fen. Biomass of algae approximated 0.3 mg C ml(-1), which corresponds to 82.8 % of the living biomass (bacteria, heterotrophic nanoflagellates, algae, protozoans and rotifers). Rotifers were abundant in new pitchers; nematodes and mites were seldom found in all pitchers. A similar qualitative and quantitative composition of the aquatic biocoenoses was observed in pitchers of another allochthonous S. purpurea population growing in Blekinge, Sweden. Biomass of algae represented nearly one quarter of the total organic matter content in the pitchers. Thus, nitrogen and phosphorus compounds present in the algae biomass might be used by the carnivorous S. purpurea plant as additional food source in allochthonous populations in Europe lacking top predators.     

Analysis of amino acids in nectar from pitchers of Sarracenia purpurea (Sarraceniaceae)

Sarracenia purpurea L. (northern pitcher plant) is an insectivorous plant with extrafloral nectar that attracts insects to a water-filled pitfall trap. We identified and quantified the amino acids in extrafloral nectar produced by pitchers of S. purpurea. Nectar samples were collected from 32 pitchers using a wick-sampling technique. Samples were analyzed for amino acids with reverse-phase high-performance liquid chromatography with phenylisothiocyanate derivatization. Detectable amounts of amino acids were found in each of the 32 nectar samples tested. Mean number of amino acids in a nectar sample was 9 (SD = 2.2). No amino acid was detected in all 32 samples. Mean amount of amino acids in a nectar sample (i.e., amount per wick) was 351.4 ng (SD = 113.2). Nine amino acids occurred in 20 of the 32 samples (aspartic acid, cysteine, glutamic acid, glycine, histidine, hydroxyproline, methionine, serine, valine) averaging 263.4 ng (SD = 94.9), and accounting for ~75% of the total amino acid content. Nectar production may constitute a significant cost of carnivory since the nectar contains amino acids. However, some insects prefer nectar with amino acids and presence of amino acids may increase visitation and capture of insect prey.     

Mimicry and mutualism in carnivorous pitcher plants (Sarraceniaceae, Nepenthaceae, Cephalotaceae, Bromeliaceae)

The carnivorous pitcher plants of the Sarraceniaceae, Nepenthaceae and Cephalotaceae seem to have developed attraction and rewarding systems which resemble those of many flowers. Contrary to a previous view, Batcsian mimicry does not appear to apply to pitcher traps because: (a) there is no evidence of insects visiting traps by mistake, (b) no model is known for any one of the traps, (c) the duration of the trap activity and the structure of the plant community are not compatible with a deceptive mimetic status, (d) nectar which is a real reward is provided to visiting insects by the pitcher plants. It is suggested that these plants perform mutual rather than deceptive relations with the insect communities in their habitats. Insects benefit from nectar which is provided by pitchers and which serves for their nutrition in habitats where sources of floral nectar might be either uncommon or absent. At the same time the insects pay the plants in a small portion of their community which is 'sacrificed' as prey and consumed by the plants, which grow in nutrient deficient soils.     

Conservation of genetic diversity in the endangered plant Eriogonum ovalifolium var. vineum (Polygonaceae)

The purpose of his research was to describethe organization of genetic variation in thefederally endangered plant taxon Eriogonumovalifolium var. vineum using allozymes. Such information can help prioritize sites andmanagement choices for capturing andmaintaining genetic variation and can reducethe number of populations necessary to committo conservation, thus reducing costs andconflicts with competing land uses. Information on genetic diversity patterns alsoprovides insight into evolutionary anddemographic history of a taxon which canprovide means to assess future risk of erosionof diversity. Similar to other Eriogonumovalifolium varieties, E. ovalifoliumvar. vineum is diverse atboth the taxon (proportion of polymorphic loci[P] = 0.55 and alleles per locus [A] =5.45 [SD = 2.5]) and population (P = 0.56 [SD =0.11] and A = 2.68 [SD = 0.35]) levels. Gene diversity (H _e) withinpopulations averaged 0.19 (SD = 0.03). Wefound some evidence for limited clonalreproduction within populations. Populationswere moderately differentiated from one another(_S = 0.14) and showed moderatedeviations from Hardy-Weinberg equilibriumwithin populations (f = 0.14 and F =0.19). Mean Nei's genetic distance (D)among all pairs of populations was 0.02. Populations with high levels of multiplemeasures of genetic diversity, high levels ofdifferentiation, and low levels of apparentinbreeding are suggested as conservationpriorities.     

Population growth and production of Habrotrocha rosa Donner (Rotifera: Bdelloidea) and its contribution to the nutrient supply of its host,the northern pitcher plant,Sarracenia purpurea L. (Sarraceniaceae)

The population growth and biomass production of the pitcher-plant (Sarracenia purpurea L.) inquiline, Habrotocha rosa Donner (Rotifera: Bdelloidea), its consumption by other pitcher-plant inqulines, and its excretion of phosphorus (PO4–P) and nitrogen (NO3–N and NH4–N), were investigated in laboratory experiments. Observed population growth and production rate of H. rosa were higher at pH 4 (2.3 rotifers d-1) than at pH 3 (1.3 rotifers d-1), 5 (1.9 rotifers d-1), or 6 (0.8 rotifers d-1). Populations of H. rosa are an abundant and reliable food source for larvae of the dipteran inqulines Wyeomyia smithii (Coq.) and Blaesoxipha fletcheri (Aldrich) that co-occur with H. rosa in S. purpurea pitchers. Abundance of H. rosa within a pitcher is negatively associated with abundance of dipteran larvae, and these larvae consume rotifers in direct proportion to rotifer density (Type I functional response). Habrotrocha rosa may also account for the majority of the plant's supply of N and P. An average population of rotifers in the field (∼400 per pitcher) can excrete ∼5.2 μg NO3-N, ∼3.91 μg NH4-N, and ∼18.4 μg PO4–P per day into a single leaf, and excretion rate is independent of water pH. Over the six-month growing season of pitcher-plants in Massachusetts, U.S.A., we estimate that rotifers could supply 8.8–43 mg of N and 18.2–88 mg of P. These values far exceed the amount of N and P previously estimated to be supplied annually to the plants through insect capture or rainfall. This revised version was published online in September 2006 with corrections to the Cover Date.     

Occurrence of the rotifer,Habrotrocha cf. rosa Donner,in the purple pitcher plant,Sarracenia purpurea L., (Sarraceniaceae) along the eastern seaboard of North America

Sarracenia purpurea L. plants were studiedin seven bogsalong the eastern seaboard of the United States fromNew Jersey to Georgia. Water sampled from 225 leaveswas found to contain several invertebrates. A singlebdelliod rotifer, a form of Habrotrocha cf. rosaDonner very similar to that described by Bateman(1987) in S. purpurea in western Newfoundland,was identified in 70% of the leaves. Investigationsare in progress to examine the possibility that thisstrong association indicates H. cf. rosa isspecific to S. purpurea.     

Genetic variability and founder effect in the pitcher plant Sarracenia purpurea (Sarraceniaceae) in populations introduced into Switzerland: from inbreeding to invasion

BACKGROUND AND AIMS: The long-lived and mainly outcrossing species Sarracenia purpurea has been introduced into Switzerland and become invasive. This creates the opportunity to study reactions to founder effect and how a species can circumvent deleterious effects of bottlenecks such as reduced genetic diversity, inbreeding and extinction through mutational meltdown, to emerge as a highly invasive plant. METHODS: A population genetic survey by random amplified polymorphism DNA markers (RAPD) together with historical insights and a field pollination experiment were carried out. KEY RESULTS: At the regional scale, S. purpurea shows low structure (thetast=0.072) due to a recent founder event and important subsequent growth. Nevertheless, multivariate statistical analyses reveal that, because of a bottleneck that shifted allele frequencies, most of the variability is independent among populations. In one population (Tenasses) the species has become invasive and genetic analysis reveals restricted gene flow and family structure (thetast=0.287). Although inbreeding appears to be high (Fis >0.410 from a Bayesian estimation), a field pollination experiment failed to detect significant inbreeding depression upon F1 seed number and seed weight fitness-traits. Furthermore, crosses between unrelated individuals produced F1 seeds with significantly reduced fitness, thus showing local outbreeding depression. CONCLUSIONS: The results suggest that, under restricted gene flow among families, the species may not only have rapidly purged deleterious alleles, but also have undergone some form of selection for inbreeding due to co-adaptation between loci.     

Spatial genetic structure and clonal diversity of island populations of lady's slipper (Cypripedium calceolus) from the Biebrza National Park (northeast Poland)

Three populations of the rare and endangered plant species Cypripedium calceolus were included in a study of genetic diversity and spatial genetic structure in the Biebrza National Park, northeast Poland. Analysis of 11 allozyme loci indicate that the populations of this species contained high genetic variability (P = 45.5%, A= 1.73). On the other hand, the genetic differentiation (FST = 0.014, P < 0.05) among C. calceolus populations was very low when compared to other species with similar life history characteristics. The observed high rate of gene flow (Nm = 18) may suggest that the populations studied derived from each other in the recent past. Five polymorphic allozyme markers identified 109 multilocus genotypes in three populations and the majority of them (67%) were population-specific. One of the populations studied, characterized by particularly extensive vegetative reproduction, showed the lowest clonal diversity (G/N = 0.15) and heterozygosity (HO = 0.111) values and the highest FIS(0.380), when compared to other two populations (G/N = 0.26-0.27, HO= 0.166-178, FIS = 0.024-0.055). This may indicate that clonal reproduction has an important influence on the genetic structure of C. calceolus populations. The longevity of genets, the out-crossing breeding system and the presence of recruitment from seeds are factors maintaining genetic diversity in C. calceolus.     

濒危植物猪血木人工繁殖幼苗的遗传多样性及对种群复壮的启示

猪血木为山茶科特有的单型属珍稀濒危植物,目前仅在广东省阳春市八甲镇有分布,且种群数量不足200株,为给濒危植物猪血木的种群成功回归自然和种群复壮提供科学依据,采用AFLP分子技术,对7个种源人工繁殖的猪血木幼苗遗传多样性进行研究。结果表明:6对引物共检测到位点数为115个,其中多态位点数为68个,多态位点所占比率为59.13%,观察等位基因数(Na)为1.5826、有效等位基因数(Ne)为1.3813、Nei′s基因多样性(H)为0.2215、Shannon多样性指数(Ⅰ)为0.3280。UPGMA聚类将7个种源的幼苗划分为3支,不同种源间幼苗的遗传距离与种源地理距离存在显著相关性(P<0.05)。说明不同种源人工繁殖猪血木幼苗仍保持较高的遗传多样性。建议采集不同种源种子进行人工繁殖和人工种群构建,促进物种的种群复壮。     

Random amplified polymorphic DNA (RAPD) markers reveal less genetic variation in the endangered plant Cerastiumfischerianum var. molle than in the widespread conspecific C. fischerianum var. fischerianum (Caryophyllaceae)

Random amplified polymorphic DNA (RAPD) analysis was used to assess the level of genetic diversity in an endangered plant Cerastiumfischerianum var. molle and the widespread conspecific C. fischerianum var. fischerianum. At both the variety and the population level, C. fischerianum var. molle had a lower level of RAPD variation than var. fischerianum. Analysis of molecular variance ( AMOVA ) showed that most of the genetic diversity exists among populations for both varieties. Genetic differentiation among populations probably resulted from the highly selfing habits of both varieties. To conserve C. fischerianum var. molle genetically, preservation of only a part of the population is insufficient.     

Genetic diversity and morphological differentiation in Liatris helleri (Asteraceae), a threatened plant species

Liatris helleri (Asteraceae) is an insect-pollinated herbaceous perennial endemic to several high-elevation sites in the Blue Ridge Mountains of North Carolina. Allozymes were used to describe the genetic diversity and population structure in nine populations of this rare, federally listed species. Differences in leaf morphology were also examined for greenhouse-grown plants representing several populations. The proportion of the total genetic diversity found among populations, as indicated by the allozyme data, was 16%. Higher levels of population differentiation were found for differences in leaf shape; population of origin accounted for 37% of the variation in maximum leaf width, while families within populations accounted for 7%. In contrast to many endemic species, L. helleri maintains fairly high levels of genetic diversity. For the species, the percent polymorphic loci was 87.5, the average number of alleles at variable loci was 3.00 and the gene diversity was 0.276. Mean population values were percent polymorphic loci =58.4, mean number of alleles per polymorphic locus =2.59 and gene diversity =0.219. The estimated gene flow was low (Nm=0.85–1.32) and a relatively high correlation (r=0.55; p<0.005) was found between linear geographic and genetic distance. This suggests that the populations are partially isolated by distance, despite the limited range (<60 km) of the species. We recommend that population distinetiveness be maintained in restoration efforts.     

Genetic diversity and geographic differentiation in endangered Ammopiptanthus (Leguminosae) populations in desert regions of northwest China as revealed by ISSR analysis

• Background and Aims The desert legume genus Ammopiptanthuscomprises two currently endangered species, A. mongolicus andA. nanus. Genetic variability and genetic differentiation betweenthe two species and within each species were examined. • Methods Inter-simple sequence repeat (ISSR) marker datawere obtained and analysed with respect to genetic diversity,structure and gene flow. • Key Results Despite the morphological similarity betweenA. mongolicus and A. nanus, the two species are geneticallydistinct from each other, indicated by 63 % species-specificbands. Low genetic variability was detected for both populationlevel (Shannon indices of diversity H_pop = 0·106, percentageof polymorphic loci P = 18·55 % for A. mongolicus; H_pop= 0·070, P = 12·24 % for A. nanus) and specieslevel (H_sp = 0·1832, P = 39·39 % for A. mongolicus;H_sp = 0·1026, P = 25·89 % for A. nanus). Moderategenetic differentiation was found based on different measures(AMOVA _ST and Hickory ^B) in both A. mongolicus (0·3743–0·3744)and A. nanus (0·2162–0·2369). • Conclusions The significant genetic difference betweenthe two species might be due to a possible vicariant evolutionaryevent from a single common ancestor through the fragmentationof their common ancestor's range. Conservation strategies forthese two endangered species are proposed.     

Allozyme Variation and the Genetic Structure of Populations of the Rare Sedge Carex misera (Cyperaceae)

Abstract Carex misera is a rare sedge, endemic to rocky outcrops and mountain summits within the southern Appalachian Mountains from northern Georgia to northern North Carolina. We assessed allozyme diversity for 406 individuals from nine populations over most of the geographic range. Twenty-seven putative loci were assayed and eight (30%) were found to be polymorphic. Nei's gene diversity statistics ( H _T =0.043, H _S =0.019, G _ST =0.551) indicated low levels of variation but relatively highly differentiated populations, suggesting little gene flow. Significant deviations from genotypic expectations under Hardy-Weinberg equilibrium, high positive fixation indices, and the existence of small genetic neighborhoods within populations suggest that at least some inbreeding occurs. Cluster analysis of Nei's genetic identity statistics and principal component analysis of allele frequency data showed high similarity among the six southern populations with the two northern populations more differentiated from them and from each other. These results suggest that preservation of the northern populations is necessary to conserve the already low levels of genetic diversity within the species.     

Molecular genetic variation following a population crash in the endangered Mauna Kea silversword, Argyroxiphium sandwicense ssp. sandwicense (Asteraceae)

The endangered Mauna Kea silversword, Argyroxiphium sandwicense ssp. sandwicense (Asteraceae), has experienced a severe decline in distribution and abundance because of predation by alien ungulates. The small remnant natural population on the Mauna Kea volcano contains only 46 individuals. By contrast, the Haleakala silversword, A. sandwicense ssp. macrocephalum, consists of a large, vigorous population exceeding 60 000 individuals. Molecular genetic variation in the two populations was assessed using random amplified polymorphic DNA (RAPD) loci. Despite its severe crash in size, the Mauna Kea population did not differ significantly from the Haleakala population in the number of detectably polymorphic loci or in heterozygosity. The lack of substantial reduction in genetic variation, at least as measured with RAPD loci, suggests that the Mauna Kea population may not yet have gone through multiple generations at very small size.