Elevation,space and host plant species structure Ericaceae root-associated fungal communities in Papua New Guinea

Our study aimed to identify significant predictors (spatial distance, elevation, host plant taxonomy) which shape the structure of endophytic fungal (ENDF) and putative ericoid mycorrhizal (ErMF) communities associated with roots of Ericaceae in Papua New Guinea. Roots of five Ericaceae together with one non-Ericaceae species were sampled at an experimental site and one common Ericaceae species was chosen for sampling along an elevation gradient. ENDF and putative ErMF communities were determined using the 454-sequencing approach. ENDF as well as putative ErMF communities were affected by interacting host plant. While the putative ErMF community was structured by host plants at the genus level, the ENDF community was affected by host plant subfamily level. Composition of ENDF as well as putative ErMF communities were affected by elevation. Non-Ericaceae plant species (Hypericum sp.) harbored similar communities of ENDF as well as putative ErMF as Ericaceae plants. Our study provides a first insight into ErMF and ENDF community ecology of Ericaceae in Papua New Guinea.     

Allozyme and life history variation in five northwardly colonizing North American weed species

The relationships of allozyme and life history variation in a particularly narrow ecological setting are studied. Levels of genetic variation are compared in five introduced, predominantly selfing weedy species that are undergoing rapid range expansion northward in eastern N. America, mostly in monocultures of soybean and maize. In all of these species, a low level of allozyme variation contrasts sharply with the substantial inter- and intrapopulational variation in morphological and phenological life history features. Evolutionary and historical factors, determining variability of the species examined are reviewed, including founder effects, breeding system, environmental homogeneity, polyploidy, domestication, and crop-weed interactions.     

Arbuscular mycorrhiza of introduced and native grasses colonizing zinc wastes: implications for restoration practices

The analysis of mycorrhizal status of grasses introduced under conventional phytoremediation programmes (including covering of the waste area with a layer of uncontaminated soil and watering) and of grasses that spontaneously established in later successional stages, was carried out on the slopes of the 1- to 30-year-old tailings of ZG Trzebionka Mining Company located near Chrzanów (southern Poland). Most grasses were mycorrhizal and the parameters of mycorrhization were higher on the older parts of the waste. Grasses selected for restoration practices were well developed only if the waste was covered with a layer of soil and continuous irrigation took place, both being expensive practices. The field experiment showed that the introduction of standard inoculum containing mycorrhizal fungi indeed improved the development of grasses during early stages, but still was not effective enough due to high erosion of the substratum. A slight improvement was observed when AgroHydroGel was used to lock moisture in the soil, but the plants did not survive for longer time periods. On the contrary, much better results were obtained when vegetatively multiplied grasses selected from specimens originating from natural succession were used to stabilize the vegetation on the bare industrial waste.     

Flowering phenology of some native perennial tropical grasses from north-eastern Australia

The division of north-eastern Australia into tropical and sub-tropical zones at approximately the latitude of 20° S, as suggested by the flowering phenology of Heteropogon contortus, is supported by studies on other perennial grasses of the native pastures. A progressive evolution away from an obligate short-day flowering response which characterizes the tropical forms of Bothriochloa bladhii, perhaps Themeda australis, and the exclusive tropical species Dicanthium tenuiculum, through a quantitative short-day response, as in the more widely distributed B. decipiens var. cloncurrensis, to the day-neutral or opportunistic and largely subtropical species of B. decipiens and D. sericeum, is suggested as a sequence of flowering strategies leading to wider adaptation into the sub-tropics. There is evidence from here and elsewhere that tropical forms or species of perennial grasses are grosser than their subtropical counterparts and this is coupled with their short-day flowering behaviour. The evidence suggests that B. decipiens and D. sericeum are the evolutionary products of taxa nearer to B. decipiens var. cloncurrensis and D. tenuiculum which exhibit day-length control of flowering.     

Complex patterns of hybridization between exotic and native North American poplar species

? Premise of the study: Poplars and their hybrids are seen as important candidates for bioenergy initiatives. However, many concerns have been raised about large-scale plantations of new poplar cultivars. The deployment of such plants with novel traits brings the risk of potential spread of novel genome regions (including exotic genes, transgenes, or other heritable modifications) into natural populations of related species. The possibility of introgression is especially high in poplars because reproductive barriers between species are weak. Knowledge of the frequency of hybridization between cultivated trees and natural populations is one important step in the risk-assessment process. ? Methods: We studied the rate of spontaneous hybridization from two sexually mature poplar plantations into adjacent natural populations of Populus deltoides and P. balsamifera. The two plantations, both in eastern Canada, contain many different complex hybrid clones with components from exotic species, mostly P. nigra, P. trichocarpa, and P. maximowiczii. We analyzed 12 species-specific single nucleotide polymorphisms from six different genes in 5373 offspring sampled from the natural populations. ? Results: Contributions from all three exotics were found in the offspring, confirming low reproductive barriers among poplar species in these sections. The frequency of hybrid offspring varied among pollen donors, recipient populations, and years. ? Conclusions: The remarkably high rate of hybridization that was found in the smallest natural population sampled suggests that small peripheral populations carry a higher risk of introgression. These results could be used as a starting point for developing regulatory guidelines for the introduction of plants with novel traits.     

Comparison of root-associated communities of native and non-native ectomycorrhizal hosts in an urban landscape

Non-native tree species are often used as ornamentals in urban landscapes. However, their root-associated fungal communities remain yet to be examined in detail. Here, we compared richness, diversity and community composition of ectomycorrhizosphere fungi in general and ectomycorrhizal (EcM) fungi in particular between a non-native Pinus nigra and a native Quercus macrocarpa across a growing season in urban parks using 454-pyrosequencing. Our data show that, while the ectomycorrhizosphere community richness and diversity did not differ between the two host, the EcM communities associated with the native host were often more species rich and included more exclusive members than those of the non-native hosts. In contrast, the ectomycorrhizosphere communities of the two hosts were compositionally clearly distinct in nonmetric multidimensional ordination analyses, whereas the EcM communities were only marginally so. Taken together, our data suggest EcM communities with broad host compatibilities and with a limited numbers of taxa with preference to the non-native host. Furthermore, many common fungi in the non-native Pinus were not EcM taxa, suggesting that the fungal communities of the non-native host may be enriched in non-mycorrhizal fungi at the cost of the EcM taxa. Finally, while our colonization estimates did not suggest a shortage in EcM inoculum for either host in urban parks, the differences in the fungi associated with the two hosts emphasize the importance of using native hosts in urban environments as a tool to conserve endemic fungal diversity and richness in man-made systems.     

Response of the invasive Centaurea maculosa and two native grasses to N-pulses

Nitrogen is often a limiting resource on semi-arid grasslands. During the growing season, N is often only available during short-term pulses associated with wetting events. The Eurasian forb Centaurea maculosa Lam. has invaded millions of hectares of semi-arid grasslands in western North America. C. maculosa's success could be attributed to greater use of N-pulses, or more efficient use of N supplied in those pulses compared with native grasses. In a glasshouse, C. maculosa and two native grasses, the caespitose Pseudoroegneria spicata [Scribn. and Smith] A. Love and the rhizomatous Pascopyrum smithii [Rybd.] A. Love, were established in mixed- and monoculture combinations, and then conditioned to weekly N-pulses of 8, 24, or 72 h for 8 weeks. These pulse durations are typical on semi-arid grasslands. At the end of the 8 weeks, plants were exposed to ¹⁵N-labeled nitrate (¹⁵NO₃ ^–) for 8 h and harvested 16 h later to compare short-term root uptake of ¹⁵NO₃ ^–. C. maculosa did not have greater enrichment (atom % ¹⁵N), rate of ¹⁵N-uptake (mol g^–1 h^–1), or ¹⁵N acquired (relative to ¹⁵N applied) than the grasses. C. maculosa's ¹⁵N-uptake per unit mass was relatively consistent across pulse durations, whereas ¹⁵N-uptake was lower at the longer pulse durations for the grasses. In general, C. maculosa acquired more of the applied ¹⁵N than P. spicata but less than P. smithii. ¹⁵N acquired was often influenced by the neighbour's identity. Regarding growth responses, C. maculosa produced more total biomass than the grasses, except for P. smithii plants growing with C. maculosa conditioned to 72 h pulses of N. Root mass ratios varied depending on the neighbor. Overall, C. maculosa used nitrogen less efficiently than the grasses. C. maculosa's success as an invasive species cannot be explained wholly by a greater response to N-pulses or more efficient use of N-pulses compared with native grasses with which it competes.     

Structure and species composition of ectomycorrhizal fungal communities colonizing seedlings and adult trees of Pinus montezumae in Mexican neotropical forests

Mexico is a center of diversity for pines, but few studies have examined the ectomycorrhizal (ECM) fungal communities associated with pines in this country. We investigated the ECM communities associated with Pinus montezumae seedlings and mature trees in neotropical forests of central Mexico and compared their structure and species composition. Root tips were sampled on both planted seedlings and naturally occurring adult trees. A total of 42 ECM operational taxonomic units (OTUs) was found on P.?montezumae. Diversity and similarity indices showed that community structure was similar for both plant growth stages, but phylogenetic diversity and Chao-estimated richness were higher for seedlings. Species composition differed between communities. The dominant OTUs belonged to the families Atheliaceae, Cortinariaceae, and Sebacinaceae, although different taxa appeared to colonize seedlings and adults. Only 12 OTUs were shared between seedlings and adults, which suggests that ECM fungi which colonize seedlings are still not fully incorporated into mycelial networks and that ECM taxa colonizing young individuals of P.?montezumae are likely to come from fungal propagules. Intra-generic diversity could be an insurance mechanism to maintain forest productivity under stressed conditions. This is the first report describing the abundance of Atheliaceae in tree roots in neotropical ecosystems.     

Chromosome numbers for native North American unifoliolate species of Crotalaria (Leguminosae)

Chromosome counts are reported for nine taxa of the genusCrotalaria. Previous reports ofn = 16 are confirmed forC. sagittalis L. andC. stipularia Desv. First counts ofn = 16 are reported forC. bupleurifolia var.bupleurifolia, C. nayaritensis, C. polyphylla,C. purshii, C. quercetorum, C. rotundifolia var.rotundifolia, andC. rotundifolia var.vulgaris.     

Assessment of soil fungal communities using pyrosequencing

Pyrosequencing, a non-electrophoretic method of DNA sequencing, was used to investigate the extensive fungal community in soils of three islands in the Yellow Sea of Korea, between Korea and China. Pyrosequencing was carried out on amplicons derived from the 5′ region of 18S rDNA. A total of 10,166 reads were obtained, with an average length of 103 bp. The maximum number of fungal phylotypes in soil predicted at 99% similarity was 3,334. The maximum numbers of phylotypes predicted at 97% and 95% similarities were 736 and 286, respectively. Through phylogenetic assignment using BLASTN, a total of 372 tentative taxa were identified. The majority of true fungal sequences recovered in this study belonged to the Ascomycota (182 tentative taxa in 2,708 reads) and Basidiomycota (172 tentative taxa in 6,837 reads). The predominant species of Ascomycota detected have been described as lichen-forming fungi, litter/wood decomposers, plant parasites, endophytes, and saprotrophs: Peltigera neopolydactyla (Lecanoromycetes), Paecilomyces sp. (Sordariomycetes), Phacopsis huuskonenii (Lecanoromycetes), and Raffaelea hennebertii (mitosporicAscomycota). The majority of sequences in the Basidiomycota matched ectomycorrhizal and wood rotting fungi, including species of the Agaricales and Aphyllophorales, respectively. A high number of sequences in the Thelephorales, Boletales, Stereales, Hymenochaetales, and Ceratobasidiomycetes were also detected. By applying high-throughput pyrosequencing, we observed a high diversity of soil fungi and found evidence that pyrosequencing is a reliable technique for investigating fungal communities in soils.     

Dynamics of root growth and decay in two grasses native to semi-arid Argentina

The pattern of root growth and decay in Stipa tenuis Phil, and Piptochaetium napostaense (Speg.) Hack, was examined under field conditions in root observation chambers. The roots of both species grew uninterruptedly throughout the whole year. Root elongation during spring, summer, and early autumn can be six and five times as high as that in the late autumn to winter period for S. tenuis and P. napostaense, respectively. Root decay was a continuous process in both species throughout the year, with maximum decay rates occurring from late spring through to the middle of autumn. Comparison of minimum and maximum values registered during the year showed a root decay ratio of about 4:1 for S. tenuis and one of 5:1 for P. napostaense. During the period of maximum root growth, both species showed a pulse-like pattern of root elongation in response to rapid changes in water availability. In a semi-arid region in which the soil is notably shallow, root growth behaviour of this kind should allow these species to respond opportunistically to water.     

Ectomycorrhizal fungal communities associated to Nothofagus species in Northern Patagonia

Ectomycorrhizal fungi constitute an important component of soil biota in Nothofagus forests in Patagonia. However, ectomycorrhizal fungal community is poorly known in this region. Here, we assess biodiversity and community compositions of ectomycorrhizal fungal species associated with Nothofagus dombeyi, N. obliqua and N. alpina. We selected three monospecific Nothofagus forest sites for each species within the boundaries of the Lanin National Park in Northern Patagonia. Ectomycorrhizal fungal species were identified based on morphotyping and rDNA (ITS and 28S rDNA) sequence analysis using both universal and taxon-specific primers. Contrary to previous studies on congeneric host trees, our results showed no significant differences among Nothofagus forest types in terms of fungal biodiversity and community composition. However, altitude had a strong effect on the structure of the ectomycorrhizal fungal community associated with Nothofagus spp.     

镉胁迫对2种油菜土壤真菌群落的影响

[背景] 人类活动引起的农田重金属污染已成为严重的环境问题。镉（Cd）是最具毒性的重金属之一,能对人体和生态系统构成威胁。[目的] 研究不同浓度镉处理对2种油菜（甘蓝型油菜和芥菜型油菜）的土壤（根际和非根际）真菌群落的影响,为镉的生物修复和健康风险评估提供理论基础。[方法] 对2种油菜土壤（根际和非根际）真菌转录间隔区（Internal Transcribed Spacer,ITS）进行高通量测序,分析镉对根际和非根际土壤真菌群落的影响。[结果] 镉胁迫改变了土壤真菌群落的组成和结构,但对2种油菜土壤真菌群落的α多样性几乎无显著影响。土壤镉浓度和生物量与2种油菜根际土壤真菌群落显著相关,芥菜型油菜非根际土壤真菌群落也与镉污染浓度显著相关。土壤真菌分子生态网络也受到镉污染的影响,甘蓝型油菜根际土壤网络稳定性降低,共生关系减少。甘蓝型油菜非根际土壤网络稳定性升高,但共生关系减少。芥菜型油菜的根际和非根际土壤的网络稳定性升高,而且共生关系增多。[结论] 镉污染会影响土壤系统中的本土真菌群落,从而可能进一步改变土壤的生态系统功能。     

Hybridization among three native North American Canis species in a region of natural sympatry

Background

Population densities of many species throughout the world are changing due to direct persecution as well as anthropogenic habitat modification. These changes may induce or increase the frequency of hybridization among taxa. If extensive, hybridization can threaten the genetic integrity or survival of endangered species. Three native species of the genus Canis, coyote (C. latrans), Mexican wolf (C. lupus baileyi) and red wolf (C. rufus), were historically sympatric in Texas, United States. Human impacts caused the latter two to go extinct in the wild, although they survived in captive breeding programs. Morphological data demonstrate historic reproductive isolation between all three taxa. While the red wolf population was impacted by introgressive hybridization with coyotes as it went extinct in the wild, the impact of hybridization on the Texas populations of the other species is not clear.

Methodology/ Principal Findings

We surveyed variation at maternally and paternally inherited genetic markers (mitochondrial control region sequence and Y chromosome microsatellites) in coyotes from Texas, Mexican wolves and red wolves from the captive breeding programs, and a reference population of coyotes from outside the historic red wolf range. Levels of variation and phylogenetic analyses suggest that hybridization has occasionally taken place between all three species, but that the impact on the coyote population is very small.

Conclusion/Significance

Our results demonstrate that the factors driving introgressive hybridization in sympatric Texan Canis are multiple and complex. Hybridization is not solely determined by body size or sex, and density-dependent effects do not fully explain the observed pattern either. No evidence of hybridization was identified in the Mexican wolf captive breeding program, but introgression appears to have had a greater impact on the captive red wolves.     

Migratory patterns and connectivity of two North American grassland bird species

Effective management and conservation of migratory bird populations require knowledge and incorporation of their movement patterns and space use throughout the annual cycle. To investigate the little‐known migratory patterns of two grassland bird species, we deployed 180 light‐level geolocators on Grasshopper Sparrows (Ammodramus savannarum) and 29 Argos‐GPS tags on Eastern Meadowlarks (Sturnella magna) at Konza Prairie, Kansas, USA, and six US Department of Defense (DoD) installations distributed across the species' breeding ranges. We analyzed location data from 34 light‐level geolocators and five Argos‐GPS tags attached for 1 year to Grasshopper Sparrows and Eastern Meadowlarks, respectively. Grasshopper Sparrows were present on the breeding grounds from mid‐April through early October, substantially longer than previously estimated, and migrated on average ~2,500 km over ~30 days. Grasshopper Sparrows exhibited strong migratory connectivity only at a continental scale. The North American Great Lakes region likely serves as a migratory divide for Midwest and East Coast Grasshopper Sparrows; Midwest populations (Kansas, Wisconsin, and North Dakota; n = 13) largely wintered in Texas or Mexico, whereas East Coast populations (Maryland and Massachusetts, n = 20) wintered in the northern Caribbean or Florida. Our data from Eastern Meadowlarks provided evidence for a diversity of stationary and short‐ and long‐distance migration strategies. By providing the most extensive examination of the nonbreeding movement ecology for these two North American grassland bird species to date, we refine information gaps and provide key insight for their management and conservation.     

Diversity of root-associated arbuscular mycorrhizal fungal communities in a rubber tree plantation chronosequence in Northeast Thailand

Rubber tree (Hevea brasiliensis) is of major economic importance in Southeast Asia and for small land holders in Thailand in particular. Due to the high value of latex, plantations are expanding into unsuitable areas, such as the northeast province of Thailand where soil fertility is very low and therefore appropriate management practices are of primary importance. Arbuscular mycorrhizal fungi (AMF) contribute to plant growth through a range of mechanisms and could play a key role in a more sustainable management of the rubber plantations. We described the diversity of AMF associated with rubber tree roots in Northeast Thailand in relation to tree age and soil parameters along a chronosequence of rubber tree plantations. Cassava fields were included for comparison. Rubber tree and cassava roots harbored high diversity of AMF (111 Virtual Taxa, VT), including 20 novel VT. AMF VT richness per sample was consistently high (per site mean 16 to 21 VT per sample) along the chronosequence and was not related to soil properties. The composition of AMF communities differed between cassava and rubber tree plantations and was influenced by soil texture and nutrient content (sand, K, P, Ca). AMF community composition gradually shifted with the age of the trees. Our results suggest that the high diversity of AMF in this region is potentially significant for maintaining high functionality of AMF communities.     

Responses to simulated herbivory and water stress in two tropical C4 grasses

Summary The African grass Hyparrhenia rufa has established itself successfully in South American savannas (Llanos) and displaced dominant native grasses such as Trachypogon plumosus from the wetter and more fertile habitats. Several ecophysiological traits have been related to the higher competitive capacity of H. rufa. To further analyze the behavior of both species, their growth, biomass allocation, physiological and architectural responses to defoliation and water stress were compared under controlled conditions. Although total, aerial and underground biomass decreased under defoliation in both grasses, increases in clipped-leaf biomass and area compensated for defoliation in H. rufa but not in T. plumosus. This difference was due mainly to a higher proportion of assimilates being directed to leaf and tiller production and a higher leaf growth rate in the African grass as compared to T. plumosus, which showed incrased senescence under frequent defoliation. In both species, water stress ameliorated the effects of defoliation. The ability to compensate for defoliated biomass in H. rufa is possibly related to its long coevolution with large herbivores in its original African habitat and is apparently one of the causes of its success in Neotropical savannas.