Alien conifer invasions in South America: short fuse burning?

Alien conifers have been widely planted in the Southern Hemisphere. Australia, New Zealand and South Africa, all with long histories of alien conifer planting, have major problems with invasive conifers (“wildings”). Widespread planting of alien conifers has a much shorter history in South America, and invasions are a recent phenomenon. A workshop was convened in Argentina in May 2007 to discuss the rapid emergence of problems with invasive conifers in South America. Workshop delegates agreed that: the problem is likely to increase substantially and rapidly in many parts of the continent; the problem is not widely recognized; lessons from elsewhere can be transferred; and collaboration can bring benefits. The need was expressed: for an accurate assessment of the dimensions of the problem; to raise awareness of the problem; for a common research agenda; to initiate management interventions. This paper summarizes the key aims, deliberations, and planned outcomes of the workshop. Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Out of the Palaeotropics? Historical biogeography and diversification of the cosmopolitan ectomycorrhizal mushroom family Inocybaceae

Aim The ectomycorrhizal (ECM) mushroom family Inocybaceae is widespread in north temperate regions, but more than 150 species are encountered in the tropics and the Southern Hemisphere. The relative roles of recent and ancient biogeographical processes, relationships with plant hosts, and the timing of divergences that have shaped the current geographic distribution of the family are investigated. Location Africa, Australia, Neotropics, New Zealand, north temperate zone, Palaeotropics, Southeast Asia, South America, south temperate zone. Methods We reconstruct a phylogeny of the Inocybaceae with a geological timeline using a relaxed molecular clock. Divergence dates of lineages are estimated statistically to test vicariance‐based hypotheses concerning relatedness of disjunct ECM taxa. A series of internal maximum time constraints is used to evaluate two different calibrations. Ancestral state reconstruction is used to infer ancestral areas and ancestral plant partners of the family. Results The Palaeotropics are unique in containing representatives of all major clades of Inocybaceae. Six of the seven major clades diversified initially during the Cretaceous, with subsequent radiations probably during the early Palaeogene. Vicariance patterns cannot be rejected that involve area relationships for Africa–Australia, Africa–India and southern South America–Australia. Northern and southern South America, Australia and New Zealand are primarily the recipients of immigrant taxa during the Palaeogene or later. Angiosperms were the earliest hosts of Inocybaceae. Transitions to conifers probably occurred no earlier than 65 Ma. Main conclusions The Inocybaceae initially diversified no later than the Cretaceous in Palaeotropical settings, in association with angiosperms. Diversification within major clades of the family accelerated during the Palaeogene in north and south temperate regions, whereas several relictual lineages persisted in the tropics. Both vicariance and dispersal patterns are detected. Species from Neotropical and south temperate regions are largely derived from immigrant ancestors from north temperate or Palaeotropical regions. Transitions to conifer hosts occurred later, probably during the Palaeogene.     

Cryptic species, native populations and biological invasions by a eucalypt forest pathogen

Human‐associated introduction of pathogens and consequent invasions is very evident in areas where no related organisms existed before. In areas where related but distinct populations or closely related cryptic species already exist, the invasion process is much harder to unravel. In this study, the population structure of the Eucalyptus leaf pathogen Teratosphaeria nubilosa was studied within its native range in Australia, including both commercial plantations and native forests. A collection of 521 isolates from across its distribution was characterized using eight microsatellite loci, resulting in 112 multilocus haplotypes (MLHs). Multivariate and Bayesian analyses of the population conducted in structure revealed three genetically isolated groups (A, B and C), with no evidence for recombination or hybridization among groups, even when they co‐occur in the same plantation. DNA sequence data of the ITS (n = 32), β‐tubulin (n = 32) and 27 anonymous loci (n = 16) were consistent with microsatellite data in suggesting that T. nubilosa should be considered as a species complex. Patterns of genetic diversity provided evidence of biological invasions by the pathogen within Australia in the states of Western Australia and New South Wales and helped unravel the pattern of invasion beyond Australia into New Zealand, Brazil and Uruguay. No significant genetic differences in pathogen populations collected in native forests and commercial plantations were observed. This emphasizes the importance of sanitation in the acquisition of nursery stock for the establishment of commercial plantations.     

Some overlooked or misidentified species of Teloschistes from South America and a key to the South-American species

Three species are discussed: Teloschistes hosseusianus Gyelnik, formerly known only from the type locality in Argentina is shown to have a wider distribution in South America. T. stellatus (Mey. & Flot.) Mull. Arg. known only from the type locality in Peru is reported from other localities in Peru and Chile. T. velifer F. Wils. previously known from Australia and New Zealand is reported from six localities in Chile. One of these is T. hollermayeri Ras. which is a synonym of T. velifer. A key is given to the 11 species of Teloschistes so far known from South America.     

Morphological variation among widely dispersed larval populations of anadromous southern hemisphere lampreys (Geotriidae and Mordaciidae)

Larvae of all three southern hemisphere anadromous parasitic lampreys were collected from rivers in Australia, New Zealand and South America. Body intervals were measured, trunk myomeres counted and the frequency of pigmentation in different body regions recorded. Morphometric data were subjected to multiple group principal components analysis (MGPCA) which took into account changes during growth. The components (together with myomere counts) and the pigmentation data were both subjected to discriminant analysis. Ordination and rank correlation tests revealed no evidence for either latitudinal clines or a continuum of circumpolar change amongst larval lamprey populations. Clustering of population centroids clearly distinguished between Mordacia lapicida (Gray) from Chile and M. mordax (Richardson) from south-eastern Australia. Populations of Geotria australis Gray divided into groups representing three geographical regions, namely Argentina, Chile and Australasia (Western Australia, Tasmania and New Zealand). Ammocoetes from Argentina were the most divergent, possessing a more posterior cloaca, taller dorsal fins, a greater gap between dorsal fins, and distinctive pigmentation on the head and caudal fin. Within the Australasian group, Western Australian and New Zealand populations clustered closer than either did with those from Tasmania. The cluster analyses for larval populations of G. australis suggest that, during their marine trophic phase, the adults of this species originating from Argentinian and Chilean rivers follow different migratory routes, whereas those from Western Australia, New Zealand and, to a lesser extent, Tasmania intermix.     

DNA bar-coding reveals source and patterns of <Emphasis Type="Italic">Thaumastocoris peregrinus</Emphasis> invasions in South Africa and South America

Thaumastocoris peregrinus is a recently introduced invertebrate pest of non-native Eucalyptus plantations in the Southern Hemisphere. It was first reported from South Africa in 2003 and in Argentina in 2005. Since then, populations have grown explosively and it has attained an almost ubiquitous distribution over several regions in South Africa on 26 Eucalyptus species. Here we address three key questions regarding this invasion, namely whether only one species has been introduced, whether there were single or multiple introductions into South Africa and South America and what the source of the introduction might have been. To answer these questions, bar-coding using mitochondrial DNA (COI) sequence diversity was used to characterise the populations of this insect from Australia, Argentina, Brazil, South Africa and Uruguay. Analyses revealed three cryptic species in Australia, of which only T. peregrinus is represented in South Africa and South America. Thaumastocoris peregrinus populations contained eight haplotypes, with a pairwise nucleotide distance of 0.2–0.9% from seventeen locations in Australia. Three of these haplotypes are shared with populations in South America and South Africa, but the latter regions do not share haplotypes. These data, together with the current distribution of the haplotypes and the known direction of original spread in these regions, suggest that at least three distinct introductions of the insect occurred in South Africa and South America before 2005. The two most common haplotypes in Sydney, one of which was also found in Brisbane, are shared with the non-native regions. Sydney populations of T. peregrinus, which have regularly reached outbreak levels in recent years, might thus have served as source of these three distinct introductions into other regions of the Southern Hemisphere.     

Crying wolf, crying foul, or crying shame: alien salmonids and a biodiversity crisis in the southern cool-temperate galaxioid fishes?

The galaxioid fishes are the dominant, most speciose group of freshwater fishes (with >50 species) in the lands of the cool southern hemisphere, with representatives in western and eastern Australia, Tasmania, New Caledonia, Lord Howe Island, New Zealand, the Chatham, Auckland and Campbell Islands, Patagonian South America (Chile, Argentina), the Falkland Islands and South Africa. The group is most diverse in Australia and New Zealand. Lepidogalaxiidae is found only in Australia, Retropinnidae in Australia and New Zealand, and Galaxiidae across the entire range of the group. Many species are in serious conservation crisis for a diversity of reasons, including habitat deterioration and possibly fisheries exploitation, but there is enduring and pervasive information that shows that the group has been seriously impacted by the acclimatisation of salmonid fishes originating in the cool-temperate northern hemisphere, particularly brown and rainbow trout. With few exceptions, where these trout have been introduced there has been major decline in the galaxioids, especially Galaxiidae, as a result of a complexly interacting series of adverse impacts from these introduced fishes. In some places, centrarchids and cichlids may also have adverse impacts. In addition, there appear to have been adverse impacts from the translocation of galaxioids into communities where they do not naturally occur. In many instances it appears that displacement of the galaxioids has led to a situation where galaxioids and salmonids no longer co-occur, owing either to displacement or predation, leading to fish communities in which there is no explicit evidence for displacement. These effects are resulting in the galaxioid fishes being amongst the most seriously threatened fishes known.     

Microsatellites and 16S sequences corroborate phenotypic evidence of trans-Andean variation in the parasitoid Microctonus hyperodae (Hymenoptera: Braconidae)

Eight South American geographical populations of the parasitoid Microctonus hyperodae Loan were collected in South America (Argentina, Brazil, Chile and Uruguay) and released in New Zealand for biological control of the weevil Listronotus bonariensis (Kuschel), a pest of pasture grasses and cereals. DNA sequencing (16S, COI, 28S, ITS1, beta-tubulin), RAPD, AFLP, microsatellite, SSCP and RFLP analyses were used to seek markers for discriminating between the South American populations. All of the South American populations were more homogeneous than expected. However, variation in microsatellites and 16S gene sequences corroborated morphological, allozyme and other phenotypic evidence of trans-Andes variation between the populations. The Chilean populations were the most genetically variable, while the variation present on the eastern side of the Andes mountains was a subset of that observed in Chile.     

Landscape characteristics of non‐native pine plantations and invasions in Southern Chile

The spread of non‐native conifers into areas naturally dominated by other vegetation types is a growing problem in South America. This process results in a landscape transformation as the conifers suppress native vegetation leading to reduced biodiversity, lower water availability and altered nutrient dynamics. Previous research highlights the broad spatial extents of land cover change in parts of Chile. However, in Southern Chile, the extent of plantations and the landscape characteristics associated with plantations and ongoing pine invasions are poorly understood. Here, we characterised non‐native pine land cover within one Landsat scene (World Reference System 2 Path 232/Row 92; ~34 000 km²) in Southern Chile. We created training data based on historical high‐resolution imagery, derived land cover predictors from time series of Landsat observations and used a Random Forest classifier to map the distribution of non‐native pines. The overall classification accuracy was 88%, and the accuracy of the non‐native pine class exceeded 90%. Although 71% of non‐native pine patches were within 500 m of other non‐native pine patches, isolated non‐native pine patches were found to occur up to 55 km from the nearest neighbour. These distant plantations could exacerbate invasion risk by creating propagule sources for novel invasion fronts. In relation to landscape characteristics, non‐native pines were found to be more likely to occur in low slope and mid‐elevation areas. Because most of the study area is native forest, most non‐native pine patches border native forest. However, non‐native pine patches were almost three times more likely than random patches to border grass/agriculture. This suggests that grasslands and disturbed sites, which have low resistance to non‐native pine invasion, are disproportionately exposed to pine propagules. Our results indicate that non‐native pine plantations are extensive across Southern Chile, and well poised to cause future invasion.     

<Emphasis Type="Italic">Pinus contorta</Emphasis> invasion in the Chilean Patagonia: local patterns in a global context

Alien conifer invasions are affecting ecosystems across the globe, but until recently, reports of such invasions in South America were scarce. Pinus contorta was first established in Chilean Patagonia for erosion control caused by historical fires and cattle farming. Recently, the species has been planted over large areas for commercial purposes. It is well adapted to local conditions and is now spreading into natural areas. This study analyzes natural regeneration of Pinus contorta around Coyhaique city, Chile, to determine the spatial patterns of invasion. Five study sites were selected, four with grasslands dominated by exotic species and one site in the steppe. In each site, the plantation (seed source) was characterized using morphological attributes and density. Regeneration, density, height and age at different distances from the seed source were recorded, and ground cover was measured as an environmental factor influencing the invasion process. A comparative analysis was also conducted between the situation in Chile and other countries affected by P. contorta invasion. In Chile, P. contorta regeneration is significantly influenced by distance from the seed source. Higher densities are found close to the parent stand (up to 13,222 trees ha⁻¹), decreasing as distance from the seed source increases. Age and height structure indicate that the invasion process is at an early stage, and this offers a unique opportunity to study the process of invasion and to monitor it over time. In order to preserve the distinctiveness of Patagonian ecosystem, decisive action is required to control invasive conifers, with P. contorta as the number one priority. Relative to control, there is much that can be learnt from the experiences of other countries, such as New Zealand.     

Recent advances in the understanding of Xanthomonas citri ssp. citri pathogenesis and citrus canker disease management

Taxonomic status : Bacteria; Phylum Proteobacteria; Class Gammaproteobacteria; Order Xanthomonadales; Family Xanthomonadaceae; Genus Xanthomonas; Species Xanthomonas citri ssp. citri (Xcc). Host range : Compatible hosts vary in their susceptibility to citrus canker (CC), with grapefruit, lime and lemon being the most susceptible, sweet orange being moderately susceptible, and kumquat and calamondin being amongst the least susceptible. Microbiological properties : Xcc is a rod‐shaped (1.5–2.0 × 0.5–0.75 µm), Gram‐negative, aerobic bacterium with a single polar flagellum. The bacterium forms yellow colonies on culture media as a result of the production of xanthomonadin. Distribution : Present in South America, the British Virgin Islands, Africa, the Middle East, India, Asia and the South Pacific islands. Localized incidence in the USA, Argentina, Brazil, Bolivia, Uruguay, Senegal, Mali, Burkina Faso, Tanzania, Iran, Saudi Arabia, Yemen and Bangladesh. Widespread throughout Paraguay, Comoros, China, Japan, Malaysia and Vietnam. Eradicated from South Africa, Australia and New Zealand. Absent from Europe.     

Welcome back New Zealand: regional biogeography and Gondwanan origin of three endemic genera of mite harvestmen (Arachnida, Opiliones, Cyphophthalmi)

Aim Biogeographers have long been intrigued by New Zealand’s biota due to its unique combination of typical ‘continental’ and ‘island’ characteristics. The New Zealand plateau rifted from the former supercontinent Gondwana c. 80 Ma, and has been isolated from other land masses ever since. Therefore, the flora and fauna of New Zealand include lineages that are Gondwanan in origin, but also include a very large number of endemics. In this study, we analyse the evolutionary relationships of three genera of mite harvestmen (Arachnida, Opiliones, Cyphophthalmi) endemic to New Zealand, both to each other and to their temperate Gondwanan relatives found in Australia, Chile, Sri Lanka and South Africa. Location New Zealand (North Island, South Island and Stewart Island). Methods A total of 94 specimens of the family Pettalidae in the suborder Cyphophthalmi were studied, representing 31 species and subspecies belonging to three endemic genera from New Zealand (Aoraki, Neopurcellia and Rakaia) plus six other members of the family from Chile, South Africa, Sri Lanka and Australia. The phylogeny of these taxa was constructed using morphological and molecular data from five nuclear and mitochondrial genes (18S rRNA, 28S rRNA, 16S rRNA, cytochrome c oxidase subunit I and histone H3, totalling c. 5 kb), which were analysed using dynamic as well as static homology under a variety of optimality criteria. Results The results showed that each of the three New Zealand cyphophthalmid genera is monophyletic, and occupies a distinct geographical region within the archipelago, grossly corresponding to palaeogeographical regions. All three genera of New Zealand mite harvestmen fall within the family Pettalidae with a classic temperate Gondwanan distribution, but they do not render any other genera paraphyletic. Main conclusions Our study shows that New Zealand’s three genera of mite harvestmen are unequivocally related to other members of the temperate Gondwanan family Pettalidae. Monophyly of each genus contradicts the idea of recent dispersal to New Zealand. Within New Zealand, striking biogeographical patterns are apparent in this group of short‐range endemics, particularly in the South Island. These patterns are interpreted in the light of New Zealand’s turbulent geological history and present‐day patterns of forest cover.     

Support for vicariant origins of the New Zealand Onychophora

Aim The distribution of Onychophora across the southern continents has long been considered the result of vicariance events. However, it has recently been hypothesized that New Zealand was completely inundated during the late Oligocene (25–22 Ma) and therefore that the entire biota is the result of long-distance dispersal. We tested this assumption using phylogenetic and molecular dating of DNA sequence data from Onychophora. Location New Zealand, Australia, South Africa, Chile (South America). Methods We obtained DNA sequence data from the nuclear genes 28S and 18S rRNA to reconstruct relationships among species of Peripatopsidae (Onychophora). We performed molecular dating under a Bayesian relaxed clock model with a range of prior distributions using the rifting of South America and South Africa as a calibration. Results Our phylogenetic trees revealed that the New Zealand genera Ooperipatellus and Peripatoides, together with selected Australian genera (Euperipatoides, Phallocephale and an undescribed genus from Tasmania), form a monophyletic group that is the sister group to genera from Chile (Metaperipatus) and South Africa (Peripatopsis and Opisthopatus). The relaxed clock dating analyses yielded mean divergence times from 71.3 to 78.9 Ma for the split of the New Zealand Peripatoides from their Australian sister taxa. The 0.95 Bayesian posterior intervals were very broad and ranged from 24.5 to 137.6 Ma depending on the prior assumptions. The mean divergence of the New Zealand species of Ooperipatellus from the Australian species Ooperipatellus insignis was estimated at between 39.9 and 46.2 Ma, with posterior intervals ranging from 9.5 to 91.6 Ma. Main conclusions The age of Peripatoides is consistent with long-term survival in New Zealand and implies that New Zealand was not completely submerged during the Oligocene. Ooperipatellus is less informative on the question of continuous land in the New Zealand region because we cannot exclude a post-Oligocene divergence. The great age of Peripatoides is consistent with a vicariant origin of this genus resulting from the rifting of New Zealand from the eastern margin of Gondwana and supports the assumptions of previous authors who considered the Onychophora to be a relict component of the New Zealand biota.     

Phylogeny of Cyttaria inferred from nuclear and mitochondrial sequence and morphological data

Cyttaria species (Leotiomycetes, Cyttariales) are obligate, biotrophic associates of Nothofagus (Hamamelididae, Nothofagaceae), the southern beech. As such Cyttaria species are restricted to the southern hemisphere, inhabiting southern South America (Argentina and Chile) and southeastern Australasia (southeastern Australia including Tasmania, and New Zealand). The relationship of Cyttaria to other Leotiomycetes and the relationships among species of Cyttaria were investigated with newly generated sequences of partial nucSSU, nucLSU and mitSSU rRNA, as well as TEF1 sequence data and morphological data. Results found Cyttaria to be defined as a strongly supported clade. There is evidence for a close relationship between Cyttaria and these members of the Helotiales: Cordierites, certain Encoelia spp., Ionomidotis and to a lesser extent Chlorociboria. Order Cyttariales is supported by molecular data, as well as by the unique endostromatic apothecia, lack of chitin and highly specific habit of Cyttaria species. Twelve Cyttaria species are hypothesized, including all 11 currently accepted species plus an undescribed species that accommodates specimens known in New Zealand by the misapplied name C. gunnii, as revealed by molecular data. Thus the name C. gunnii sensu stricto is reserved for specimens occurring on N. cunninghamii in Australia, including Tasmania. Morphological data now support the continued recognition of C. septentrionalis as a species separate from C. gunnii. Three major clades are identified within Cyttaria: one in South America hosted by subgenus Nothofagus, another in South America hosted by subgenera Nothofagus and Lophozonia, and a third in South America and Australasia hosted by subgenus Lophozonia, thus producing a non-monophyletic grade of South American species and a monophyletic clade of Australasian species, including monophyletic Australian and New Zealand clades. Cyttaria species do not sort into clades according to their associations with subgenera Lophozonia and Nothofagus.     

Southern hemisphere biogeography inferred by event-based models: plant versus animal patterns

The Southern Hemisphere has traditionally been considered as having a fundamentally vicariant history. The common trans-Pacific disjunctions are usually explained by the sequential breakup of the supercontinent Gondwana during the last 165 million years, causing successive division of an ancestral biota. However, recent biogeographic studies, based on molecular estimates and more accurate paleogeographic reconstructions, indicate that dispersal may have been more important than traditionally assumed. We examined the relative roles played by vicariance and dispersal in shaping Southern Hemisphere biotas by analyzing a large data set of 54 animal and 19 plant phylogenies, including marsupials, ratites, and southern beeches (1,393 terminals). Parsimony-based tree fitting in conjunction with permutation tests was used to examine to what extent Southern Hemisphere biogeographic patterns fit the breakup sequence of Gondwana and to identify concordant dispersal patterns. Consistent with other studies, the animal data are congruent with the geological sequence of Gondwana breakup: (Africa(New Zealand(southern South America, Australia))). Trans-Antarctic dispersal (Australia <--> southern South America) is also significantly more frequent than any other dispersal event in animals, which may be explained by the long period of geological contact between Australia and South America via Antarctica. In contrast, the dominant pattern in plants, (southern South America(Australia, New Zealand)), is better explained by dispersal, particularly the prevalence of trans-Tasman dispersal between New Zealand and Australia. Our results also confirm the hybrid origin of the South American biota: there has been surprisingly little biotic exchange between the northern tropical and the southern temperate regions of South America, especially for animals.     

Biogeography of the Monimiaceae (Laurales): a role for East Gondwana and long‐distance dispersal,but not West Gondwana

Aim The biogeography of the tropical plant family Monimiaceae has long been thought to reflect the break‐up of West and East Gondwana, followed by limited transoceanic dispersal. Location Southern Hemisphere, with fossils in East and West Gondwana. Methods We use phylogenetic analysis of DNA sequences from 67 of the c. 200 species, representing 26 of the 28 genera of Monimiaceae, and a Bayesian relaxed clock model with fossil prior constraints to estimate species relationships and divergence times. Likelihood optimization is used to infer switches between biogeographical regions on the highest likelihood tree. Results Peumus from Chile, Monimia from the Mascarenes and Palmeria from eastern Australia/New Guinea form a clade that is sister to all other Monimiaceae. The next‐deepest split is between the Sri Lankan Hortonia and the remaining genera. The African Monimiaceae, Xymalos monospora, then forms the sister clade to a polytomy of five clades: (I) Mollinedia and allies from South America; (II) Tambourissa and allies from Madagascar and the Mascarenes; (III) Hedycarya, Kibariopsis and Leviera from New Zealand, New Caledonia and Australia; (IV) Wilkiea, Kibara, Kairoa; and (V) Steganthera and allies, all from tropical Australasia. Main conclusions Tree topology, fossils, inferred divergence times and ances‐tral area reconstruction fit with the break‐up of East Gondwana having left a still discernible signature consisting of sister clades in Chile and Australia. There is no support for previous hypotheses that the break‐up of West Gondwana (Africa/South America) explains disjunctions in the Monimiaceae. The South American Mollinedia clade is only 28–16 Myr old, and appears to have arrived via trans‐Pacific dispersal from Australasia. The clade apparently spread in southern South America prior to the Andean orogeny, fitting with its first‐diverging lineage (Hennecartia) having a southern‐temperate range. The crown ages of the other major clades (II–V) range from 20 to 29 Ma, implying over‐water dispersal between Australia, New Caledonia, New Zealand, and across the Indian Ocean to Madagascar and the Mascarenes. The endemic genus Monimia on the Mascarenes provides an interesting example of an island lineage being much older than the islands on which it presently occurs.     

松树蜂与其共生真菌的互利共生关系

松树蜂Sirex noctilio Fabricius是一种重要的国际林业检疫性害虫,主要危害针叶树,原产欧亚大陆和北非。近100多年来,先后入侵大洋洲(新西兰和澳大利亚)、南美洲(乌拉圭、阿根廷、巴西和智利)、北美洲(加拿大和美国),以及南非。2013年8月,在中国黑龙江省内首次发现松树蜂,目前发现其主要危害樟子松。松树蜂能与一种淀粉韧革菌属Amylostereum的真菌Amylostereum areolatum(Fr.)Boidin形成严格的互利共生关系,该虫除直接钻蛀树木外,还能通过产卵行为将自身毒素腺体分泌的毒素和体内共生真菌随同虫卵一起注入寄主树木体内,形成"虫-毒-菌"3个致害因子相互协作的特殊危害方式,加速树势的衰弱并造成寄主树木死亡。本文就国内外松树蜂与其共生菌互利共生关系的研究进行了综述,分别从结构与功能的层次上对其互利共生关系进行了梳理和总结,重点阐释了松树蜂与共生菌的营养共生关系,松树蜂携带传播共生菌的机制,共生菌的种群遗传学以及松树蜂毒素和共生菌在危害寄主树木时的协同关系等。以期为开展关于松树蜂的专项研究提供一些合理的建议,同时为积极有效地防控该害虫提供科学依据。     

Biogeography and phylogeny of the New Zealand cicada genera (Hemiptera: Cicadidae) based on nuclear and mitochondrial DNA data

Aim Determine the geographical and temporal origins of New Zealand cicadas. Location New Zealand, eastern Australia and New Caledonia. Methods DNA sequences from 14 species of cicadas from New Zealand, Australia, and New Caledonia were examined. A total of 4628 bp were analysed from whole genome extraction of four mitochondrial genes (cytochrome oxidase subunits I and II, and ribosomal 12S and 16S subunits) and one nuclear gene (elongation factor‐1 alpha). These DNA sequences were aligned and analysed using standard phylogenetic methods based primarily on the maximum likelihood optimality criterion. Dates of divergences between clades were determined using several molecular clock methods. Results New Zealand cicadas form two well‐defined clades. One clade groups with Australian taxa, the other with New Caledonian taxa. The molecular clock analyses indicate that New Zealand genera diverged from the Australian and New Caledonian genera within the last 11.6 Myr. Main conclusions New Zealand was likely colonized by two or more invasions. One NZ lineage has its closest relatives in Australia and the other in New Caledonia. These invasions occurred well after New Zealand became isolated from other land masses, therefore cicadas must have crossed large bodies of water to reach New Zealand.     

West Wind Drift revisited: testing for directional dispersal in the Southern Hemisphere using event-based tree fitting

Aim Recent studies suggest that if constrained by prevailing wind or ocean currents dispersal may produce predictable, repeated distribution patterns. Dispersal mediated by the West Wind Drift (WWD) and Antarctic Circumpolar Current (AAC) has often been invoked to explain the floristic similarities of Australia, South America and New Zealand. If these systems have been important dispersal vectors then eastward dispersal – from Australia to New Zealand and the western Pacific to South America – is expected to predominate. We investigate whether phylogenies for Southern Hemisphere plant groups provide evidence of historical dispersal asymmetry and more specifically whether inferred asymmetries are consistent with the direction of the WWD/AAC. Location Southern Hemisphere. Methods We assembled a data set of 23 published phylogenies for plant groups that occur in New Zealand, Australia and/or South America. We used parsimony‐based tree fitting to infer the number and direction of dispersals within each group. Observed dispersal asymmetries were tested for significance against a distribution of expected values. Results Our analyses suggest that dispersal has played a major role in establishing present distributions and that there are significant patterns of asymmetry in Southern Hemisphere dispersal. Consistent with the eastward direction of the WWD/ACC, dispersal from Australia to New Zealand was inferred significantly more often than in the reverse direction. No significant patterns of dispersal asymmetry were found between the western Pacific landmasses and South America. However, eastward dispersal was more frequently inferred between Australia and South America, while for New Zealand–South American events westward dispersal was more common. Main conclusions Our results suggest that eastward circumpolar currents have constrained the dispersal of plants between Australia and New Zealand. However, the WWD/ACC appear to have had less of an influence on dispersal between the western Pacific landmasses and South America. This observation may suggest that differences in dispersal mechanism are important – direct wind or water dispersal vs. stepping‐stone dispersal along the Antarctic coast. While our analyses provide useful preliminary insights into dispersal asymmetry in the Southern Hemisphere we will need larger data sets and additional methodological advances in order to test fully these dispersal patterns and infer processes from phylogenetic data.     

The biogeography of the austral, subalpine genus Ourisia (Plantaginaceae) based on molecular phylogenetic evidence: South American origin and dispersal to New Zealand and Tasmania

Molecular phylogenetic analyses of 26 of the 28 species of Ourisia , including eight of ten subspecies and two purported natural hybrids, are presented and used to examine the biogeography of the genus, which is distributed in subalpine to alpine habitats of South America, New Zealand and Tasmania. Gondwanan vicariance, often cited as the cause of this classic austral biogeographical pattern, was rejected by parametric bootstrapping of our combined dataset. Alternatively, various lines of evidence are presented in favour of a South American origin of Ourisia and subsequent dispersal to Australasia. Specifically, the genus likely arose in the Andes of central Chile and spread to southern Chile and Argentina, to the north-central Andes, and finally to Tasmania and New Zealand. The ancestor of the New Zealand species probably first arrived on the South Island, where the New Zealand species of Ourisia are most diverse, and migrated to the North and Stewart Islands. Because the Tasmanian and New Zealand species are sister to one another, the direction of dispersal between these two areas is equivocal. These results agree with other molecular phylogenetic studies that show that past dispersal between southern hemisphere continents has played an important role in the evolutionary history of many high-elevation austral plants. Our data also show that within South America, many of the geographical barriers (with the exception of the Atacama Desert) that have played a role in the evolution of other plant groups have not affected Ourisia species. Within New Zealand, the phylogeny and biogeography of species of Ourisia coincide with the geological history of the country and patterns of other alpine plants. © 2006 The Linnean Society of London, Biological Journal of the Linnean Society , 2006, 87 , 479–513.