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There are numerous examples of how exotic insect pests and pathogens have altered the dominance of native tree species. Changes to the structure of associated communities will depend on whether the affected species survives and if so, the degree to which it is diminished. In the southeastern USA, Persea borbonia, a common tree found in many coastal plain habitats, is the primary host of laurel wilt disease (LWD); infection rates and main-stem mortality are catastrophically high (>90%) in invaded populations. We simulated the effects of LWD prior to its arrival in coastal Mississippi by girdling and then removing the main stems of P. borbonia trees. Over a 2-year period, we monitored P. borbonia persistence via basal resprouts, understory light availability, and community structure. Removal of P. borbonia main stems resulted in a 50% increase in light transmission (measured at 1 m above ground level). All treated individuals produced basal resprouts, the size and number of which were positively related to initial tree girth. Post-treatment increases in basal area were greatest for the sub-canopy species, Ilex vomitoria, and were significantly higher in treatment versus control plots. Woody seedlings and herbaceous plants showed no significant trends in composition and abundance over time or between control and treatment plots. Our results suggest that removal of P. borbonia and subsequent resprouting causes shifts in P. borbonia size class frequencies and sub-canopy species dominance but has negligible impacts on understory plant community dynamics. 相似文献
3.
In the southeastern US, laurel wilt disease (LWD) is causing widespread mortality of species in the Lauraceae. The principal target, Persea borbonia, is the primary larval host of Papilio palamedes, which is known to feed on other Lauraceae species. Among these potential hosts, the exotic Cinnamomum camphora is the only species that has shown resistance to LWD. We hypothesized that oviposition preference for C. camphora and P. borbonia would correspond to larval performances on these species and that the relative host suitability of C. camphora would indicate an opportunity for host-switching. We used laboratory experiments and field observations to compare performance and preference of P. palamedes between C. camphora and P. borbonia foliage. Our results indicate moderate survivorship on C. camphora compared to P. borbonia and no differences in first and fourth instar growth rates between treatments. Fourth instars consumed relatively less of C. camphora foliage compared to that of P. borbonia, but metabolic efficiency did not differ between treatments. Rearing on the foliage of P. borbonia stump sprouts from LWD-infected trees resulted in significantly higher growth rates and metabolic efficiency as first and fourth instars, respectively. In the field and laboratory, we found no oviposition preference for C. camphora. While females laid eggs on C. camphora during laboratory trials, the same number of eggs was also laid on inanimate objects. We conclude that C. camphora is suitable for larval development but host-switching to this species by P. palamedes will be primarily constrained by the ecological factors that govern oviposition behaviors. 相似文献
4.
Hanula JL Mayfield AE Fraedrich SW Rabaglia RJ 《Journal of economic entomology》2008,101(4):1276-1286
The redbay ambrosia beetle, Xyleborus glabratus Eichhoff (Coleoptera: Curculionidae: Scolytinae), and its fungal symbiont, Raffaelea sp., are new introductions to the southeastern United States responsible for the wilt of mature redbay, Persea borbonia (L.) Spreng., trees. In 2006 and 2007, we investigated the seasonal flight activity of X. glabratus, its host associations, and population levels at eight locations in South Carolina and Georgia where infestations ranged from very recent to at least several years old. Adults were active throughout the year with peak activity in early September. Brood development seems to take 50-60 d. Wood infested with beetles and infected with the Raffaelea sp. was similar in attraction to uninfested redbay wood, whereas both were more attractive than a nonhost species. Sassafras, Sassafras albidium (Nutt.) Nees, another species of Lauraceae, was not attractive to X. glabratus and very few beetle entrance holes were found in sassafras wood compared with redbay. Conversely, avocado, Persea americana Mill., was as attractive to X. glabratus as swampbay, P. palustris (Raf.) Sarg., and both were more attractive than the nonhost red maple, Acer rubrum L. However, avocado had relatively few entrance holes in the wood. In 2007, we compared X. glabratus populations in areas where all mature redbay have died to areas where infestations were very active and more recent. Trap catches of X. glabratus and numbers of entrance holes in trap bolts of redbay were correlated with the number of dead trees with leaves attached. Older infestations where mature host trees had been eliminated by the wilt had low numbers of beetles resulting in trap catches ranging from 0.04 to 0.12 beetles per trap per d compared with 4-7 beetles per trap per d in areas with numerous recently dead trees. Our results indicate beetle populations drop dramatically after suitable host material is gone and provide hope that management strategies can be developed to restore redbay trees. The lack of attraction of X. glabratus to sassafras suggests that spread of X. glabratus may slow once it is outside the range of redbay. 相似文献
5.
Laurel wilt disease (LWD), a fungal disease vectored by the non-native redbay ambrosia beetle (Xyleborus glabratus Eichhoff), has caused mortality of redbay (Persea borbonia (L.) Spreng.) in the coastal plain of Georgia since 2003. Despite its rapid spread, little research has evaluated its impacts on redbay population structure and forest communities. Diseased populations of redbay in five sites (2–4 years post infestation) were compared to healthy populations in three uninfested sites in five counties in Georgia. The results showed high redbay mortality, shifts in size structure, and changes in community composition. An average of 90 % of redbay trees ≥3 cm diameter at breast height (DBH) were dead in infested sites, compared to 0–35 % in control sites. Mortality was seen in individuals of the smallest stem diameter category (<1.00 cm diameter at ground height). DBH of live redbay trees in control sites was twice that of those in infested sites. Photosynthetically active radiation was 4.8 times greater at infested sites than control sites due to loss of redbay canopy. Community structure measurements showed redbay trees had the greatest mean importance value (IV) at control sites compared to the 8th mean IV at infested sites for live stems. Two species co-dominant to redbay, sweetbay (Magnolia virginiana L.) and loblolly bay (Gordonia lasianthus (L.) J. Ellis), were of higher importance at infested than control sites, suggesting they are increasing in dominance following the mortality of redbay. This study shows LWD has impacted redbay populations and altered associated forest communities in Georgia. 相似文献
6.
The laurel wilt pathogen Raffaelea lauricola was hypothesized to have been introduced to the southeastern USA in the mycangium of the redbay ambrosia beetle, Xyleborus glabratus, which is native to Asia. To test this hypothesis adult X. glabratus were trapped in Taiwan and on Kyushu Island, Japan, in 2009, and dead beetles were sent to USA for isolation of fungal symbionts. Individual X. glabratus were macerated in glass tissue grinders, and the slurry was serially diluted and plated onto malt agar medium amended with cycloheximide, a medium semiselective for Ophiostoma species and their anamorphs, including members of Raffaelea. R. lauricola was isolated from 56 of 85 beetles in Taiwan and 10 of 16 beetles in Japan at up to an estimated 10 000 CFUs per beetle. The next most commonly isolated species was R. ellipticospora, which also has been recovered from X. glabratus trapped in the USA, as were two other fungi isolated from beetles in Taiwan, R. fusca and R. subfusca. Three unidentified Raffaelea spp. and three unidentified Ophiostoma spp. were isolated rarely from X. glabratus collected in Taiwan. Isolations from beetles similarly trapped in Georgia, USA, yielded R. lauricola and R. ellipticospora in numbers similar to those from beetles trapped in Taiwan and Japan. The results support the hypothesis that R. lauricola was introduced into the USA in mycangia of X. glabratus shipped to USA in solid wood packing material from Asia. However differences in the mycangial mycoflora of X. glabratus in Taiwan, Japan and USA suggest that the X. glabratus population established in USA originated in another part of Asia. 相似文献
7.
Keiko Sasaki Tomohiro Ichinose Tomoko Doko Ikuko Imoto Fred Jopp 《Landscape and Ecological Engineering》2016,12(1):61-72
Distributions of lucidophyllous species are limited due to the fragmentation of laurel forest. On Komayama Hill in central Japan, we evaluated the colonization of typical lucidophyllous vascular plants from a 350-year-old laurel forest into adjacent abandoned secondary forest for conservation and restoration purposes. A total of 14 consecutive subplots were established along the vegetation border between the two forests (length, 30 m; width, 5 m), extending 70 m into the secondary forest; 18 quadrats of old-growth forest were surveyed. Edge effects of old-growth forest were found to play an important role in re-establishing lucidophyllous saplings and seedlings in the secondary forest. In particular, the abundances of the four dominant canopy species of the old-growth forest significantly decreased with increasing distance. Hence, they are expected to colonize further into the secondary forest and, ultimately, to dominate the canopy. However, the number of lucidophyllous species did not change with distance. Species such as Ficus nipponica, Damnacanthus indicus, Ilex integra, and Lemmaphyllum microphyllum were near-completely or completely limited to the old-growth forest. They are known to be negatively affected by forest fragmentation and were observed to be struggling to colonize the exterior of the old-growth forest even after 60 years of abandonment. Their absence highlighted the limited colonization capacities of some old-growth forest species and underlined the time required for habitat restoration following human disturbance. We conclude that it is important to consider the population dynamics of dominant canopy species and the colonization of these interior species when assessing the habitat expansion of lucidophyllous species and hence the restoration of degraded lands. 相似文献
8.
Spatial patterns of trees and juveniles in a laurel forest of Tenerife, Canary Islands 总被引:5,自引:0,他引:5
Spatial patterns are important characteristics of the forest and theycan reveal such things as successional status and ecological characteristics ofthe species. We tested the hypothesis that spatial distribution will bedifferent, depending on whether the species is intolerant or tolerant to shade.We assessed the spatial distribution of trees (> 4 cm dbh) andjuveniles in eight laurel forest plots. A univariate spatial analysis(performed with Ripley's K1) showed that all tree species havesignificantaggregation at short distances (2 m). Nevertheless, two groups ofspecies could be differentiated: Erica scoparia,Myrica faya and Ilex canariensisshowed a tendency for aggregation at large distances (larger than 6m)while L. azorica and Prunuslusitanicashowed aggregation only at shorter distances. Ripley's BivariateK1,2 analyses showed no significant differences in the spatialdistribution ofanalyzed species pairs from a null model. Only Laurusazoricahad a sufficient sample size for analysis of juvenile distribution. Aunivariateanalysis revealed thatL. azorica seedlings (stems < 50 cm high)were clumped in some plots up to 5 m, but this was not consistent.Saplings (stems > 50 cm high and < 4 cm dbh)didnot show strong clumping even at short distances. L.azoricasaplings had no significant aggregation with, nor repulsionfrom, adults of the same or different species. Spatial patterns of the speciesshould be considered in the development of restoration plans of the laurelforest 90%of which has disappeared or been intensively disturbed on Tenerife Island. 相似文献
9.
Patterns of invasion within a grassland community 总被引:15,自引:1,他引:14
10.
Seasonal changes in cold-resistance in five Proteaceae: Gevuina avellana, Lomatia hirsuta, Lomatia dentata, Lomatia ferruginea and Embothrium coccineum were studied in the Botanical Garden, Universidad Austral de Chile in Valdivia, Chile. All species presented such changes in relation to the minimum air temperatures but not in relation to rainfall. Cold-resistance increased together with the temperature decrease from March to May. Maximum resistance was observed in winter (June to August). The spring temperature increase caused a decrease of cold-resistance, which reached its maximum from spring (November) to summer (December to February). The results obtained for cold-resistance correspond to the weather conditions found in natural biotopes of the species. 相似文献
11.
. Spatial and temporal changes in the microbial community structure in a maritime Antarctic freshwater lake were investigated over a single day/night cycle in December 1999. The community structure of key microbial planktonic groups varied with depth and this was related to both physical and chemical stratification. However, in most cases, the community structure observed at specific depths did not change over the time period studied. These results suggested short-term stability in community structure, with only some minor effects of the diel changes in irradiance on the vertical distribution of planktonic organisms. This is in marked contrast to medium- and long-term studies, which show significant changes in microbial community structure with both time and depth. 相似文献
12.
Effects of repeated harvesting of forest residues on the ectomycorrhizal community in a Swedish spruce forest 总被引:1,自引:0,他引:1
The use of biofuels has been proposed as one possible substitute for fossil fuels, which contribute substantially to the increase in [CO2 ] in the atmosphere. However, increased harvesting of forest residues for biofuel might affect the availability of base cations, P and N, as well as the development, community dynamics and function of ectomycorrhizas. This in turn might influence nutrient uptake and tree growth. In this study we investigated the effects of repeated forest residue harvesting on ectomycorrhizal species colonizing spruce roots in the humus layer of a 35-yr-old forest. Harvesting significantly decreased the thickness of the humus layer as well as decreasing the numbers of ectomycorrhizal root tips both per metre root length and per unit humus volume. Changes in mycorrhizal community structure were studied by ITS typing with the use of PCR–RFLP analysis. In total, 19 different ITS types were found on two different sampling occasions (autumn and spring); 11 of these were common to both samplings. Nine of the ITS types were identified to at least the genus level by comparison with RFLP patterns of identified fruiting bodies or axenic cultures. Five species, Cortinarius sp. 2, Thelephora terrestris (Ehrenb.) Fr., Lactarius theiogalus (Bull.:Fr.) S. F. Gray s.st. Neuhoff, Tylospora fibrillosa Donk and Tö-96-12, occurred on over 5% of the total sampled root tips. Together these five types colonized 63% of the mycorrhizas screened. A similarity index assessment showed no shift in mycorrhizal community structure as a result of harvesting. Our findings suggest that the repeated removal of forest residues might have a strong effect on the quantity and development of ectomycorrhizal roots in the organic horizon, but little effect on the species composition of the community. 相似文献
13.
Rauno V. Alatalo 《Ecography》1978,1(4):367-376
The annual minimum energy consumption of the bird community was 2524 × 103 kcal km−2 , of which 44% was consumed by wintering species and 73% by passerines. The daily energy consumption was in summer 14–16 × 103 and in winter 1–2 × 103 kcal km−2 . In spruce forests and in afforested swamps birds required approximately 0.12% of the net primary production. Their total annual energy consumption was covered by invertebrates (59%), vertebrates (2%) and vegetable matter (39%); the food derived from the ground (55%), from trees (44%) and from the air (1%). Arboreal insectivorous passerines, ground passerines and gallinaceous birds were the most important ecological guilds. Among passerines existence metabolism accounted for 73% of the annual energy consumption, extra activity for 17%, breeding activity for 1%, moult for 4% and nestlings for 4%. 相似文献
14.
A Markovian modeling approach was used to explore territorial interactions among three forest raptors coexisting in a forested
natural area in southeast Spain: the booted eagle (Hieraaetus pennatus), the common buzzard (Buteo buteo) and the northern goshawk (Accipiter gentilis). Using field data collected over a period of 12 years, 11 annual transition matrices were built, considering four occupancy
states for each territory. The model describes transitional processes (colonization, abandonment, replacement and persistence),
permits temporal variations in the transition matrix to be tested, and simulates territorial occupation for a few subsequent
years. Parameters for the species and community dynamics were described in terms of turnover times and damping ratio. A perturbation
analysis was performed to simulate the effects of changes in the transition probabilities on the stable state distribution.
Our results indicate the existence of a stable community, largely dominated by the booted eagles, and described by a time-invariant
transition matrix. Despite the stability observed, the territorial system is highly dynamic, with frequent abandonment and
colonization events, although interspecific territorial interactions (the replacement of one species by another) are uncommon.
Consequently, the three species appear to follow relatively independent occupancy dynamics. Simulation of potential management
actions showed that substantial increases in the number of territories occupied by the less common species (goshawk and buzzard)
can only be attained if relatively large increases in their reoccupation and colonization rates are considered. 相似文献
15.
Populations of invasive species often exhibit a high degree of spatial and temporal variability in abundance and hence their
effects on resident communities. Here, we examine behavioural, genetic and environmental factors that influence variation
in populations of the yellow crazy ant, Anoplolepis gracilipes, on the remote Nukunonu Atoll of Tokelau, Pacific Ocean. Behavioural assays revealed high levels of aggression between two
groups of yellow crazy ants from different islands, and genetic analysis confirmed the presence of two distinct populations
with unique mitochondrial (mt)DNA haplotypes, designated A and D. The two populations likely resulted from two separate invasion
events. The populations exhibited significant differences in abundance of A. gracilipes, with a mean sevenfold difference in relative abundance between the two main haplotypes. The higher density haplotype D population
coexisted with 50% fewer other ant species and altered ant community composition. Vegetation composition was also significantly
different on islands harbouring the two populations. The results suggest genetic differences could play a role in the spatial
and temporal variation in the effect of the yellow crazy ant on a small oceanic atoll. We could not differentiate between
genetic effects and effects of vegetation. However, our results indicate that spatial variability in behaviour and impacts
within populations of invasive species could be in part due to genetic differences, and play a substantial role in influencing
the outcome of biological invasions. 相似文献
16.
Cecilia Callejas Paul R. Gill Ana I. Catalán Gastón Azziz Susana Castro-Sowinski Silvia Batista 《World journal of microbiology & biotechnology》2011,27(6):1507-1512
Cyanobacterial 16S ribosomal RNA gene diversity was examined in a benthic mat on Fildes Peninsula of King George Island (62o09′54.4′′S,
58o57′20.9′′W), maritime Antarctica. Environmental DNA was isolated from the mat, a clone library of PCR-amplified 16S rRNA
gene fragments was prepared, and amplified ribosomal DNA restriction analysis (ARDRA) was done to assign clones to seven groups.
Low cyanobacterial diversity in the mat was suggested in that 83% of the clones were represented by one ARDRA group. DNA sequences
from this group had high similarity with 16S rRNA genes of Tychonema bourrellyi and T. bornetii isolates, whose geographic origins were southern Norway and Northern Ireland. Cyanobacterial morphotypes corresponding to
Tychonema have not been reported in Antarctica, however, this morphotype was previously found at Ward Hunt Lake (83oN), and in western
Europe (52oN). DNA sequences of three of the ARDRA groups had highest similarity with 16S rDNA sequences of the Tychonema group accounting for 9.4% of the clones. Sequences of the remaining three groups (7.6%) had highest similarity with 16S rRNA
genes of uncultured cyanobacteria clones from benthic mats of Lake Fryxell and fresh meltwater on the McMurdo Ice Shelf. 相似文献
17.
Impact of Prunus serotina invasion on understory functional diversity in a European temperate forest
Olivier Chabrerie Jérôme Loinard Sidonie Perrin Robert Saguez Guillaume Decocq 《Biological invasions》2010,12(6):1891-1907
We investigated the relationships between the overstory dominance of Prunus serotina, and the functional diversity of the understory plant communities, in a managed European forest. Vegetation, habitat characteristics and disturbance history were surveyed in 32 invaded stands vs. 32 paired uninvaded stands, after a random stratification. Community specialization and functional diversity indices were compared and a RLQ analysis was run to link species traits to environmental variables. The herb layer of invaded stands exhibited significantly more specialist species and a lower trait diversity compared to uninvaded stands, with respect of species richness and vegetation cover. Light arrival to the forest floor and soil properties explained most of the variation in the RLQ analysis, but 20% of the variation strongly correlated with P. serotina dominance and associated disturbances. Traits characterizing shade-tolerant, short-living ruderals and shade-avoiders (vernal geophytes) were significantly associated to invaded stands, while those associated to light-demanding graminoids characterized uninvaded stands. The establishment of functionally close species (seedlings and saplings of native woody species) tended to be lower in invaded stands. We concluded that the invader was becoming the new ecosystem engineer, first by inducing trait convergence and community specialization, thus promoting traits that enable species to capture resources in the new environment it was creating, and second by reducing the grain of local heterogeneities. 相似文献
18.
Andrew Henderson Beat Fischer Aldicir Scariot Manoel A. Whitaker Pacheco Renata Pardini 《Brittonia》2000,52(2):149-159
The flowering phenology of 27 taxa of palms in a lowland moist forest in the central Amazon was recorded over a 40 month period. Phenological data were transformed into measures, of synchrony, regularity, and duration. Flowering was observed at all times of year and there was no correlation with rainfall either for the current month or for any monthly lag interval. The 27 taxa were divided into three pollination groups—weevil, bee/fly, or beetle—based on their behavior at anthesis. Phenology was significantly correlated with pollination groups. Weevilpollinated palms had higher synchrony and shorter duration of flowering than other groups. Bee/fly-pollinated palms had lower synchrony and longer duration of flowering. The beetle-pollinated palms were intermediate between the two other groups. Seasonal regularity of flowering was similar in all three groups. We suggest that, at least inBactris, taxa exhibit staggered flowering. 相似文献
19.
Seasonal dynamics of the planktonic microbial community in a maritime Antarctic lake undergoing eutrophication 总被引:6,自引:0,他引:6
The abundance, biomass and community structure of phytoplankton,bacterioplankton and protozooplankton in a maritime Antarcticlake were determined at approximately monthly intervals fromDecember 1994 to February 1996 and compared with data from earlierstudies. Heywood Lake has become significantly eutrophic duringthe last three decades because of excreta from the expandingfur seal population in its catchment. Marked seasonal variationsin the abundance, composition and productivity of biota werecorrelated with the seasonality of both physical factors andnutrient levels. Protozooplankton were abundant, diverse andusually dominated by heterotrophic nanoflagellates (HNF), withHNF abundance peaking at 2.35 x 107 l1 in summer. Highnumbers of naked amoebae were sometimes present, reaching amaximum of 4.8 x 103 l1 in March. An estimated 89 speciesof protozoa were observed during the study, indicating substantiallymore diversity than is found in continental Antarctic lakes.Diversity was highest in spring and lowest in winter, when theentire water column became anoxic and the plankton were dominatedby bacteria and a few species of relatively large anaerobicflagellates. The current status of the lake is compared withdata for continental Antarctic and lower latitude lakes. Earlierstudies of biota and physical/chemical parameters in HeywoodLake are used to examine the effects of eutrophication overthree decades. Observed changes include increased microbialabundance and changes in both community structure and seasonalpatterns. 相似文献
20.
Emma Cebrian Fiona Tomas Paula López-Sendino Montserrat Vilà Enric Ballesteros 《Biological invasions》2018,20(10):2839-2848
The biotic resistance hypothesis predicts that more diverse communities should have greater resistance to invasions than species-poor communities. However for facultative and obligate epiphytic invaders a high native species richness, abundance and community complexity might provide more resources for the invader to thrive to. We conducted surveys across space and time to test for the influence of native algal species abundance and richness on the abundance of the invasive facultative epiphytic filamentous alga Lophocladia lallemandii in a Mediterranean Cystoseira balearica seaweed forest. By removing different functional groups of algae, we also tested whether these relationships were dependent on the complexity and abundance of the native algal community. When invasion was first detected, Lophocladia abundance was positively related to species richness, but the correlation became negative after two years of invasion. Similarly, a negative relationship was also observed across sites. The removal experiment revealed that more complex native communities were more heavily invaded, where also a positive relationship was found between native algal richness and Lophocladia, independently of the native algal abundance. Our observational and experimental data show that, at early stages of invasion, species-rich seaweed forests are not more resistant to invasion than species-poor communities. Higher richness of native algal species may increase resource availability (i.e. substrate) for invader establishment, thus facilitating invasion. After the initial invasion stage, native species richness decreases with time since invasion, suggesting negative impacts of invasive species on native biodiversity. 相似文献