Incorrect handling of calibration information in divergence time inference: an example from volcanic islands

Divergence time studies rely on calibration information from several sources. The age of volcanic islands is one of the standard references to obtain chronological data to estimate the absolute times of lineage diversifications. This strategy assumes that cladogenesis is necessarily associated with island formation, and punctual calibrations are commonly used to date the splits of endemic island species. Here, we re-examined three studies that inferred divergence times for different Hawaiian lineages assuming fixed calibration points. We show that, by permitting probabilistic calibrations, some divergences are estimated to be significantly younger or older than the age of the island formation, thus yielding distinct ecological scenarios for the speciation process. The results highlight the importance of using calibration information correctly, as well as the possibility of incorporating volcanic island studies into a formal, biogeographical hypothesis-testing framework.     

Weed biological control: applying science to solve seemingly intractable problems

Abstract   Exotic weeds pose a problem of considerable economic and environmental importance to Australia. As a consequence, Australia has developed into a leading centre of research on weed biological control, with over 60 weeds the targets of past and current projects. Using primarily entomological examples, this review highlights the contributions made by Australian scientists to the development of theory and the improvement of practice in weed biological control. It also shows how biological control practitioners have made use of, and contributed to, broader theory and knowledge of plant-herbivore relationships. Finally, it concludes with some reflections on the future direction of biological control in Australia.     

Redberry mite, Acalitus essigi (Hassan) (Acari: Eriophyidae), an additional biological control agent for Rubus species (blackberry) (Rosaceae) in Australia

Abstract  Acalitus essigi , the eriophyoid mite that causes red berry disease in Rubus species (Rosaceae), was collected from the fruits of three species of weedy blackberry, R. anglocandicans , R. laudatus and R. ulmifolius , in south-west Australia. This is the first record for this species in Western Australia and these plants appear to be new host records for A. essigi , which causes uneven ripening of fruit. Information on the mite is reviewed in the context of determining its potential as a biological control agent for Rubus species, especially those that are not susceptible to Phragmidium violaceum (Uredinales), the rust fungus being released against species of European blackberry in Australia. Published records also show that A. essigi will attack a wide range of Rubus species including species of North American origin that currently escape biological control in Australia. It may also be useful for preventing the spread of commercial varieties of Rubus (e.g. raspberry and loganberry) that have escaped to become weedy. However, the mite may have limited dispersal ability and thus require redistribution.     

Prospects for the Management of Invasive Alien Weeds Using Co-Evolved Fungal Pathogens: A Latin American Perspective

Invasive alien weeds pose a serious threat to the biodiversity of natural ecosystems and a significant constraint to agricultural production worldwide. The use of co-evolved natural enemies, a strategy referred to as classical biological control (CBC), has proven to be a potentially efficacious, cost-effective, and safe option for the management of alien weeds. An analysis of CBC of invasive weeds in Latin America is presented, which shows that only 5% of the worldwide releases of agents, overwhelmingly arthropod, have been in this region. Fungal pathogens are increasingly being considered in CBC programmes, and there are now 11 examples of Latin American fungi having been released as biocontrol agents in other regions of the world. In contrast, only three weed pathogens have been deliberately released in the region. Possible reasons for the paucity of CBC programmes in Latin America are presented, despite the presence of a significant number of alien weed species (60 are listed). An analysis of these weeds reveals that many of them could be amenable to control using natural enemies, including nine weed species for which CBC programmes have been successfully implemented elsewhere in the world. In addition, for many of these 60 species, a co-evolved and damaging mycobiota has already been recorded. The prospects for management of invasive alien weeds in Latin America, using co-evolved fungal pathogens, are assessed with particular reference to selected species from the genera Ambrosia, Broussonetia, Calotropis, Commelina, Cyperus, Dichrostachys, Echinochloa, Pittosporum, Rottboellia, Rubus, Sonchus and Ulex. This revised version was published online in July 2006 with corrections to the Cover Date.     

Thermal biology of Typhlodromips montdorensis: implications for its introduction as a glasshouse biological control agent in the UK

The recent unexpected local establishment of a non‐native predatory mite, Neoseiulus californicus (McGregor) (Acari: Phytoseiidae), in the UK prompted us to undertake this study, which investigated the thermal biology of an alien species Typhlodromips montdorensis (Schicha) (Acari: Phytoseiidae). Laboratory and field experiments on its cold tolerance were used to assess its establishment potential outside of glasshouse environments in the UK. Currently, T. montdorensis is being tested as a glasshouse biological control agent against thrips and spider mites, but is not yet licensed for release in the UK. Typhlodromips montdorensis has a developmental threshold of between 10.3 and 10.7 °C, and a thermal budget of between 108.7 and 105.3 degree‐days when estimated by weighted and simple linear regression, respectively. Under outdoor conditions, T. montdorensis could theoretically complete up to six generations a year. The supercooling points of female and larval T. montdorensis were ?22 to ?24 °C with 100% pre‐freeze mortality apparent in both acute and chronic low temperature exposures. Typhlodromips montdorensis were unable to enter diapause under a selected laboratory regime. No reproduction occurred in the field from November to March, with 100% mortality within 7–14 days of release during this period. It is concluded that T. montdorensis would be a ‘safe candidate’ for introduction as a glasshouse biological control agent in the UK.     

Can an a priori strategy be developed for biological control? The case of Onopordum spp. thistles in Australia

Abstract  Between 1992 and 2000, seven insect agents were released in Australia for the biological control of Onopordum spp. thistles. This paper describes the protocol used for the selection of these agents, starting with the development of a preliminary strategy, based on the ecology and population dynamics of the target weed. The strategy informed the surveys for natural enemies in the native range of Onopordum , targeting insects that attacked key transitional stages of the weed's life cycle. Ongoing studies of Onopordum populations in both Australia and Europe, plus experimental studies on the ecology, potential impact and preliminary host specificity of the agents, led to the refinement of the strategy and the selection and prioritisation of the agents. It is argued that development of an explicit strategy prior to release should be encouraged, as it forces researchers to revisit the rationale for and aims of particular biological control projects, ensuring that the process of agent selection remains focused. It also provides a tool to improve the process of agent selection, as subsequent results can be measured against the strategy and agent success or failure evaluated against the a priori expectations.     

DNA fingerprinting reveals significant amounts of genetic variation in a wild raspberry Rubus idaeus population

Establishing the genotypic distribution in natural plant populations is an important part of ecological studies concerning plant growth, reproduction and turn-over. Restriction enzyme-digested DNA samples, isolated from 24 plants of a natural Rubus idaeus population, were analysed with DNA fingerprinting using the M13 repeat sequence as well as a synthetic (AC)/(TG) polydinucleotide as hybridization probes. All the examined samples exhibit unique DNA fingerprint patterns, suggesting that vegetative reproduction may be considerably more restricted in wild R. idaeus populations than previously assumed. By comparison, all samples of the apomictic blackberry species Rubus nessensis, collected on the same location, were completely identical.     

Timberline and alpine vegetation on the tropical and warm-temperate oceanic islands of the world: elevation, structure and floristics

In the oceans of the tropical and warm-temperate zone (40° N–40° S), only a small number of islands are high enough to show timberline and alpine vegetation. Excluding large islands with a more continental climate, only the following oceanic islands are relevant: Pico (Azores), Madeira, Tenerife, Gran Canaria and La Palma (Canary islands), Fogo (Cape Verde islands), Fernando Poo (Bioko) and Tristan da Cunha in the Atlantic Ocean, Réunion and Grande Comore (Ngazidja) in the Indian Ocean, Yakushima (Japan), Maui and Hawaii (Hawaiian islands), and Mas Afuera (Juan Fernandez islands) in the Pacific Ocean. Timberline and alpine vegetation exist here under a unique combination of a highly oceanic climate and a marked geographic isolation which contrasts with the tropical alpine vegetation in the extended mountains of South America, Africa and Southeast Asia.This review seeks to identify common physiognomic patterns in the high elevation vegetation that exist despite the fact that the islands belong to different floristic regions of the world. Based on the existing literature as well as personal observation, an overview of the elevation, physiognomy and floristics of the forest (and tree) line and the alpine vegetation on 15 island peaks is given.The forest line ecosystems are dominated either by conifers (Canary islands, Yakushima), heath woodland (Azores, Madeira, Réunion, Grande Comore, Fernando Poo) or broad-leaved trees (Hawaiian islands, Juan Fernandez islands, Tristan da Cunha). In the subalpine and alpine belts, dry sclerophyllous scrub occurs on island mountains that are exposed to the trade winds (Canary islands, Cape Verde islands, Hawaiian islands, Réunion, Grande Comore). These peaks are more or less arid above the forest line because a temperature inversion restricts the rise of humid air masses further upslope. In the summit regions of the remaining islands, which are located either in the wet equatorial and monsoonal regions or in the temperate westerly zones without an effective inversion layer, mesic to wet vegetation types (such as grassland, alpine heathland and fern scrub) are found.Compared to mountains at a similar latitude in continental areas, the forest line on the islands is found at 1000 to 2000 m lower elevations. The paper discusses four factors that are thought to contribute to this forest line depression: (1) drought on trade-wind exposed island peaks with stable temperature inversions, (2) the absense of well-adapted high-altitude tree species on isolated islands, (3) immaturity of volcanic soils, and (4) an only small mountain mass effect that influences the vertical temperature gradient.     

The Radiation of Darwin’s Giant Daisies in the Galápagos Islands

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Examination of sex attractants for monitoring weed biological control agents in Hawaii

The identification of sex attractants was undertaken for potential use in the study of two biological control agents against Rubus spp. in Hawaii. Attractants for Croesia zimmermani (Lepidoptera: Tortricidae) and Schreckensteinia festaliella (Lepidoptera: Heliodinidae) were developed by field screening a variety of putative lures in sticky traps, based on attractants for congeneric species. Croesia zimmermani was most attracted to E11-tetradecen-1-ol and E11-tetradecenal, while S. festaliella was attracted to (10,12)-(E,E)-hexadecadienal alone. Development of monitoring systems based on sex attractants can enable better evaluation of biocontrol programmes, and provide cost-effective information on presence/absence, density, phenology, synchrony with the host, dispersal rate and other useful parameters.     

世界黑莓产业发展和研究现状及前景

在查阅大量文献资料的基础上,结合作者的研究成果,对国内外黑莓(Rubus spp.)产业发展及研究现状进行了综述,并分析了存在的问题,阐述了中国黑莓产业的发展优势和产业化前景.目前黑莓在全世界的种植面积约为20 035 hm2,年产量1.5×105 ～2.0×105 t,栽培区域遍及各大洲,其中塞尔维亚的黑莓种植面积位居世界第一,美国的黑莓年产量居世界第一,亚洲仅中国种植黑莓;近几年来,罗马尼亚、波兰、墨西哥、智利、匈牙利、中国以及美国的黑莓种植面积增长较快;因黑莓极不易贮存,绝大多数鲜果用于加工.国外以常规育种技术为主、分子技术为辅培育出许多黑莓品种,栽培技术已经非常成熟,成功实现了机械化采收,并逐步推广黑莓的有机生产体系和大棚栽培技术.国外黑莓生产中面临的主要问题是经济、冻害和病虫害等.黑莓于1986年引入中国,从1994年开始推广,至2010年种植面积约4 500 hm2,主要集中在江苏省的溧水县、赣榆县和溧阳市,90％以上鲜果加工成速冻果出口.在国外引种和国内野生种质资源收集的基础上,中国的研究者开展了黑莓的选种和育种研究,并培育和筛选出适宜于本地种植的黑莓优良品种;黑莓的栽培、加工技术研究也取得了显著的成果,并研制出一些加工产品.当前中国黑莓产业主要面临主栽品种单一、农药残留量超标、栽培条件差等方面的问题,制约了黑莓产业的发展.由于黑莓适于低山丘陵栽培,具有结果早、见效快、营养价值高等优势,在中国具有广阔的发展前景.     

Chlorophyll fluorometry as a method of determining the effectiveness of a biological control agent in post-release evaluations

ABSTRACT

The impact of the planthopper Megamelus scutellaris, a biocontrol agent of water hyacinth in South Africa, was assessed using chlorophyll fluorometry in a greenhouse study under two different eutrophic nutrient treatments and agent densities (high and low). The results indicated that plants grown in low nutrients with high densities of M. scutellaris showed the greatest reduction in the fluorescence parameters Fv/Fm and PI_abs. The successful use of chlorophyll fluorometry for the detection of subtle insect damage to water hyacinth leaves could have future application in post-release studies to measure the impact of M. scutellaris in the field.     

Trophic web associated with the South American tomato moth Tuta absoluta: implications for its conservation biological control in Argentina

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The concept of biological control methods in aquaculture

Microbial techniques of biocontrol using the interaction ofmicroorganisms to repress the growth of deleterious bacteria andviruses were developed. The bacterial strain used in this work alsoimproved the growth of fishes and crustaceans. Using the conceptandprocedures of the biocontrol method described here, the aquacultureproduction became stable and evenincreased.     

Rapid molecular technique for identification of a biological control agent Rhodosporidium diobovatum

The purpose of this study was to develop a rapid molecular technique for identification of the biological control agent, Rhodosporidium diobovatum. DNA from all yeast cultures described below was extracted, amplified by PCR using primers specific to septate fungi, and fixed to nylon membranes. Using sequence information obtained from the GenBank database, Rhodosporidium diobovatum-specific oligonucleotides were designed and, after labeling with digoxigenin-d-UTP, were used as probes in a dot-blot hybridization assay. After preliminary testing, two probes were selected for further study. For probe RD3, a positive reaction was obtained at 38, 42 and 48°C with R. diobovatum in pure culture. Other yeast isolates such as Rhodosporidium toruloides, R. fluviale, R. babjevae, R. sphaerocarpum, R. kratochvilovae, R. azoricum, Pichia anomala, and some common greenhouse pathogens tested gave a negative result. The other probe (RD1) reacted with two species, R. diobovatum and R. babjevae at 42°C. The present dot-blot assay can be used reliably to identify the biocontrol agent, Rhodosporidium diobovatum, from pure culture and plant tissue.     

Biodegradation of mango kernel by Syncephalastrum racemosum and its biological control

Poor germination of mango seed due to fungal decay is a common problem in mango nurseries. The main causal fungus behind this problem is a black spore producing fungus, Syncephalastrum racemosum. This fungus exhibited high amylolytic activity and hence utilised the starch present in mango kernel for its own growth, thereby resulting in the death of emerging radical and plumule, which ultimately causes the death of emerging seedlings. A simple biocontrol device has been worked out by modifying the storage conditions of the mango seeds from aerobic to facultative. This change resulted in yeast growth on the pulp sticking to the mango seed, which in turn produced alcohol and prevented the growth of this fungus. The germination of such seeds has been found to be about 85–90%.     

Impact of the biological control agent Phlebiopsis gigantea on its resident genetic structure in the Baltic Sea area

The basidiomycete Phlebiop sis gigantea (Fr.) Jülich has been used in Swedish forestry as a biocontrol agent against the root and butt-rot pathogen Heterobasidion annosum s.l. on freshly cut Picea abies stumps since the early 1990s. Until 2005, the commercial preparation of this biological stump treatment, Rotstop®, has been based on a single strain of P. gigantea that has been applied on more than 47,000 ha annually in Fennoscandia. This paper reports on the spread of genetic material from the Rotstop® biocontrol strain of P. gigantea to resident populations of P. gigantea. We conclude that the inoculated fungus remained to a large extent restricted to the treated plots and did not spread to the adjacent areas, dominated by the natural spore deposition from resident populations of the fungus. Furthermore, the study demonstrates high genetic diversity and low geographic differentiation in P. gigantea populations in the geographical area around the Baltic Sea.     

Use of plants by Myzus persicae in agroecosystems: Potential applications in conservation biological control

Myzus persicae (Sulzer) is a highly polyphagous aphid species that attacks several economically important crop plants. Here, trophic webs involving M. persicae, its host plants and its parasitoids were described and quantified in wheat, oat and alfalfa agroecosystems from central Argentina, with special emphasis on the sub-habitats where interactions occur: crops and adjacent field margins. Three fields cultivated with each crop species and their margins were sampled during three years; aphid abundance and mummification percentage were compared among crop plants and the diverse natural vegetation in the borders. Interactions were described using a quantitative food web approach, and abundance and mummification percentage e data were analysed using a generalized linear model. Four plant species present in the borders (Capsella bursa-pastori, Rapistrum sp., Melilotus sp. and Trifolium repens) hosted M. persicae and its parasitoids. The alfalfa agroecosystem produced a significantly higher number of aphids than oat and wheat; however, in all cases, crops and borders sustained similar aphid abundance. A total of six Aphidiinae species attacked M. persicae, with no significant differences in the richness of parasitoid species between the borders and the crops, but with significant differences in parasitoid abundance, being higher in the crops. Mummification percentage were higher in crops than in the borders, with Lysiphlebus testaceipes, Aphidius colemani and A. ervi being the most abundant species. Almost 70% of M. persicae individuals were collected from fields borders, which highlights the importance of including these sites in studies of trophic interactions in crop fields.