Convergence in community structure and dietary adaptation in Australian possums and gliders and Malagasy lemurs

Abstract The possums and gliders of Australia and the lemurs of Madagascar are ideally suited for investigation of radiation and convergence in arboreal mammal communities because of their long history of independent radiation in similar biophysical environments. Possum and glider communities at 22 sites in Australia and lemur communities at 18 sites in Madagascar were compared to evaluate patterns of community and species convergence in two shared habitats (evergreen and deciduous monsoon rainforests) and three derived habitats (Australian eucalypt forests and heaths, and Malagasy thorn scrubs). Arboreal mammals were classified into five dietary guilds for comparison of community structure and species adaptation. There is little evidence of convergence in trophic structure at the community level, but strong evidence of convergence in dietary adaptation at the species and niche level. Malagasy rainforest communities were characterized by a higher proportion of frugivore-folivores, and Australian rainforest and moist eucalypt communities by a higher proportion of folivores and folivore-frugivores. Possum and glider communities in temperate eucalypt forests and heaths supported a higher proportion of nectarivores and exudivores. Overall species richness was significantly higher in Madagascar. Four hypotheses are erected to account for these differences. The relative scarcity of frugivores in Australian evergreen rainforests is accounted for by the predominance of bird-dispersed fruits, and fruiting phenologies unsuitable for mammal exploitation and dispersal. Higher folivore diversity in Australian evergreen rainforests is associated with a more pronounced seasonal shortage of edible fruits and new leaf, which has increased dependence on mature leaf. Folivore species richness is greatest in Australian moist eucalypt forests where structural complexity, sustained by serai responses to wildfire, permits a high level of vertical segregation. Increased nectarivory and exudivory in Australian temperate eucalypt forests and heaths is associated with Mediterranean winter rainfall regimes, which permit year round exudate production, and not with the absence of nectar feeding bats as previously supposed. A lower overall species richness in Australian rainforests is attributed to a longer history of contraction and fragmentation by anthropogenic fires (monsoon rainforests) and Pleistocene climatic change (tropical evergreen rainforests). A high degree of convergence is apparent between genera occupying folivore and wood gouging niches, in terms of gastrointestinal morphology (e.g. Pseudocheirus-Lepilemur) and dental morphology (e.g. Dactylopsila-Daubentonia). Divergences are most apparent in adaptations associated with frugivory, including larger body size, diurnality, and bipedal suspension and leaping modes of locomotion (in Eulemur spp.). This study highlights the importance of founding effects, competition from other vertebrate taxa, coevolution between animals and their food plants, and differences in biophysical environments, as determinants of mammalian radiation and convergence.     

Pre‐ and post‐mating reproductive barriers drive divergence of five sympatric species of Naryciinae moths (Lepidoptera: Psychidae)

The biological species concept suggests that species can be separated on the basis of reproductive isolation. However, because natural interbreeding capabilities are often unknown, differences in morphology are generally used to separate species. Alternatively, genetic dissimilarity is used to separate morphologically similar species. Many genetic markers, including the maternally inherited mitochondrial cytochrome oxidase I sequence, cannot show interbreeding and therefore species status of groups may remain unresolved. In species of the genera Dahlica and Siederia (Lepidoptera: Psychidae: Naryciinae) the lack of morphological distinction and unknown interbreeding has led to unclear and unresolved taxonomic status. Mitochondrial DNA sequences suggest five sexual species to occur in Finland. However, their species status remains unconfirmed, due to a lack of knowledge on interbreeding, unclear morphological distinction and the limited variation in mitochondrial DNA. We combine three methods, a cross‐mating experiment, an analysis of mitochondrial and nuclear DNA, and a detailed male genital morphological examination, to establish the species status of the five suspected species. All suspected species exhibit intraspecies mating preference, although several interspecies pairs readily produce offspring. The genetic analysis, however, fails to show hybrids or introgression, suggesting that both pre‐ and post‐copulation mechanisms isolate the species reproductively. Morphological analysis of the male genitalia confirms that the species have diverged. Our results highlight the need of combining behavioural, morphological and genetic methods to determine species status in challenging taxonomic groups. © 2014 The Linnean Society of London, Biological Journal of the Linnean Society, 2014, 112 , 584–605.     

Phytophagous insect-woody sprout interactions in tropical eucalypt forest. I. Insect herbivory

Abstract Foliar insect damage levels on woody sprouts in the ground layer of two tropical eucalypt forest communities on Melville Island were between 7.8 and 43.2%. Of eight common tree species, Eucalyptus confertiflora was damaged most by insects and Buchanania obovata and Terminalia ferdinandiana the least. Seasonal trends in insect damage were not consistent between plant species and were not always consistent between vegetation types for a particular plant species. The results of this study are not consistent with hypotheses suggesting that insect grazing is a critical determinant of tree species dominance or woody sprout dormancy.     

LAND USE AND SUMMER BIRD POPULATIONS IN NORTHWESTERN GALICIA, SPAIN

Summer bird populations were studied in ten sites: two heathlands, two maritime pine Pinus pinaster plantations, one, four, seven and 13-year-old eucalypt Eucalyptus globulus plantations, one climax oak Quercus robur woodland, and a farmland area in northwestern Galicia, Spain. The farmland and oak wood contained the greatest number of species (24 and 17 respectively) while the one and four-year-old eucalypt stands contained the fewest species (four and six respectively). Avian density was highest in the oak wood (93 birds/ 10 ha) and lowest in a heathland site, the four and one-year-old eucalypt stands (26,13, and seven bird/10 ha respectively). The wren was the most widespread and dominant species occurring in all study areas except the one-year-old eucalypt stand. Mean bird species diversity for the four eucalypt stands was significantly lower than mean bird species diversity for the other wooded habitats. The avian communities of the heathlands, maritime pine and eucalypt plantations, in contrast to the oak wood and farmland, show an excessively high dominance of one species. Using avian dominance as a biological index of habitat perturbation suggests that over half the landscape (4000 km²) in northwestern Galicia is suffering from chronic stress. The newest stress to the avifauna in a long history of land exploitation by man is the importation and cultivation on grand scale of eucalypts. Balancing this tendency, traditional, small-scale farming on the mountainous terrain leads to the development of many tiny parcels whose average size is 0.28 ha; this in turn creates much ‘edge’ in hedgerow which serves to maintain a relatively rich avian species diversity in farmland.     

The effects of willow and eucalypt leaves on feeding preference and growth of some Australian aquatic macroinvertebrates

The effect of leaf species (willow, Salix fragilis L., and white gum, Eucalyptus viminalis Labill.) and leaf state (senescent or green) on the feeding selectivity and growth rates of three species of macroinvertebrate Notalina sp. Mosely (Trichoptera: Leptoceridae), Koorrnonga sp. Campbell and Suter (Ephemeroptera: Leptophlebiidae) and Physastra gibbosa (Gould) (Mollusca: Planorbidae) were tested in the laboratory. All three species of macroinvertebrate selected green willow most strongly over the other leaf types (senescent willow, green eucalypt and senescent eucalypt). Growth rates of P. gibbosa and Notalina sp. were significantly greater on green willow than on the other leaf types. We were unable to measure the growth of Koorrnonga sp. Invertebrates had access to softer internal tissues of leaf material during preference trials, therefore we do not think that leaf structure was the main influence on selection between these materials. Green willow material may have been a better food source because of the noticeably thicker biofilm that it supported, and this material may also retain higher levels of nutrients than abscissed leaves. We speculate that willow leaves may provide a preferred source of food but will be available for less time than native eucalypt detritus.     

Mammalian herbivores reveal marked genetic divergence among populations of an endangered plant species

Quantitative genetically based traits in dominant and keystone tree species can have extended effects on other biota and also on ecosystem processes. This has direct implications for managed plant systems, where choice of genetic stock in conservation or commercial plantings will affect the ecological and evolutionary trajectory of the associated biotic communities. Hence an understanding of genetic variation in quantitative traits, especially those that relate directly to fitness, should be incorporated into the management of species. In plants, quantitative traits such as foliar defences that mediate the complexity of biotic interactions (e.g. herbivory), may be key fitness traits to consider in the management of gene pools of species that are of high conservation value. In this paper we examine the interactions of an endangered eucalypt species, Eucalyptus morrisbyi and a marsupial herbivore, the common brushtail possum Trichosurus vulpecula. We investigate the genetic variability of resistance of plants sourced from two populations and genetic variability in foliage defences as key quantitative traits that may be essential for survival of this eucalypt species. Trichosurus vulpecula detect clear genetic divergence in the two E. morrisbyi populations as evidenced by their browsing preferences in the field. In addition, trees from the more susceptible population (Calverts Hill) suffered fitness consequences with lower flowering than trees from the more resistant population (Risdon Hills). Field feeding preferences were confirmed in captive feeding trials arguing differences were due to foliar attributes consistent with the genetic‐based differences observed in key chemical and physical foliage traits. Biotic interactions such as herbivory may affect populations of rare plant species. Results of this study highlight the need to understand the degree of genetic differentiation of resistance to herbivores and in the quantitative traits mediating these interactions in species of high conservation value, as these traits affect the adaptive potential of populations.     

Insect damage in Eucalyptus: A review of plantations in Chile

Chile has more than 330 000 ha of eucalypt plantations, predominantly in the eighth to the tenth region (approximately 34 to 41°S). Eucalyptus globulus ssp. globulus is the principal eucalypt planted, but Eucalyptus nitens, Eucalyptus camaldulensis, Eucalyptus delegatensis and Eucalyptus viminalis are also grown. There are four main insect pests that have been detected attacking these eucalypts in Chile: the defoliator Gonipterus scutellatus, the bark borers Phoracantha semipunctata and Phoracantha recurva and the native wood borer Chilecomadia valdiviana. More recently, Thyrinteina arnobia and Ctenarytaina eucalypti have been detected. Gonipterus scutellatus and P. recurva have been discovered in Chile within the last 2 years and it is hoped they may still be eliminated using a combination of biological control and chemical control of local populations. Phoracantha recurva and P. semipunctata are not considered a problem because attack only occurs in areas of water deficit, away from current eucalypt plantations. Chilecomadia valdiviana can damage plantations of E. nitens but rarely attacks other eucalypts.?Chilecomadia valdiviana may cause future problems through further host shifts. Thyrinteina arnobia has only been detected during quarantine surveillance in the port of Valparaiso. Ctenarytaina eucalypti, recently detected in August 1999, had an initial limited distribution in the first region. However, since then, this insect has expanded its distribution south up to the tenth region. None of the insects recorded on eucalypts in Chile to date currently presents a threat to the eucalypt industry. It is also essential that additional resources are made available for their continued monitoring and control, particularly given that the 44% of plantations are held by small to medium property owners that would otherwise be unable to control a serious outbreak because of economic restrictions.     

Disentangling the roles of chance,abiotic factors and biotic interactions among epiphytic bryophyte communities in a tropical rainforest (Yunnan,China)

• Epiphytes offer an appealing framework to disentangle the contributions of chance, biotic and abiotic drivers of species distributions. In the context of the stress-gradient theory, we test the hypotheses that (i) deterministic (i.e., non-random) factors play an increasing role in communities from young to old trees, (ii) negative biotic interactions increase on older trees and towards the tree base, and (iii) positive interactions show the reverse pattern.
• Bryophyte species distributions and abiotic conditions were recorded on a 1.1 ha tropical rainforest canopy crane site. We analysed co-occurrence patterns in a niche modelling framework to disentangle the roles of chance, abiotic factors and putative biotic interactions among species pairs.
• 76% of species pairs resulted from chance. Abiotic factors explained 78% of non-randomly associated species pairs, and co-occurrences prevailed over non-coincidences in the remaining species pairs. Positive and negative interactions mostly involved species pairs from the same versus different communities (mosses versus liverworts) and life forms, respectively. There was an increase in randomly associated pairs from large to small trees. No increase in negative interactions from young to old trees or from the canopy to the base was observed.
• Our results suggest that epiphytic bryophyte community composition is primarily driven by environmental filtering, whose importance increases with niche complexity and diversity. Biotic interactions play a secondary role, with a very marginal contribution of competitive exclusion. Biotic interactions vary among communities (mosses versus liverworts) and life forms, facilitation prevailing among species from the same community and life form, and competition among species from different communities and life forms.

     

广东翁源青云山自然保护区森林群落优势树种的生态位特征

为探讨广东翁源青云山自然保护区植被的生境适应性和竞争机制,对青云山自然保护区森林群落优势树种的生态位特征进行了分析。结果表明,群落优势种的重要值之和为49.01,其中杉木（Cunninghamia lanceolata）的重要值最大,毛竹（Phyllostachys edulis）的变异系数最大。优势种的Levins和Shannon生态位宽度较为一致,罗浮柿（Diospyros morrisiana）、栲（Castanopsis fargesii）、木荷（Schima superba）、鼠刺（Itea chinensis）和罗浮锥（C.faberi）的生态位宽度较大,而毛竹、杉木、黧蒴锥（C.fissa）和华润楠（Machilus chinensis）的生态位宽度相对较窄。所有物种对间的生态位重叠度和生态位相似性较小,表明共存物种的种间竞争不激烈,因而群落处于相对稳定的状态。生态位宽度与重要值的关系不显著,而与重要值变异系数呈显著的负相关关系,表明重要值变异系数是影响生态位宽度的重要因素。这为青云山自然保护区森林资源的保护和管理提供重要的科学依据。     

Outbreak of an invasive paropsine beetle in south‐west Ireland: preference,performance and damage to Eucalyptus

An exotic, paropsine beetle –Paropsisterna nr. gloriosa Blackburn – occurred at high densities in south‐west Ireland in 2007. In bioassays, adults and larvae fed on foliage from a variety of eucalypt species. Eggs and neonates occurred only in association with new foliage. Despite their ability to consume old foliage, adult beetles had a high preference for new leaves with low specific leaf weights (softer leaves). In choice tests, adults that depleted new foliage of their preferred host, moved to new foliage of a second host but not older foliage of the preferred host. A 2008 survey of southern Ireland indicated that P. nr. gloriosa was restricted to County Kerry, largely associated with foliage plantations in that county. The distribution of damage suggests that the initial spread of the beetle was facilitated by foliage‐trade activities. Eucalyptus parvula L.A.S. Johnson & K.D. Hill was the most heavily damaged species at many plantations. Eucalyptus pulverulenta Sims and Eucalyptus cordata Labill. were highly resistant to the beetle as indicated by low levels of damage in the field and reduced fitness of larvae in feeding trials. Nevertheless, at the plantation with the highest overall levels of damage, adult beetles moved to feed on E. pulverulenta. A progressive dispersal from plantations also caused slight damage to neighbouring ornamental eucalypts. Clear preferences by P. nr. gloriosa for new foliage, irrespective of eucalypt species, suggests that pollarding – the removal of top branches to produce dense juvenile foliage – accelerated population build‐up during 2007.     

Exotic riparian vegetation lowers fungal diversity but not leaf decomposition in Portuguese streams

1. We characterised the fungal communities of eight streams in Portugal, four bordered by native deciduous forest and four bordered by pure stands of Eucalyptus globulus .
2. Aquatic hyphomycete species richness and evenness, but not numbers of water-borne conidia, of aquatic hyphomycetes were significantly lower in eucalypt bordered streams.
3. Multivariate analyses subdivided the fungal communities into two distinct groups corresponding to riparian vegetation.
4. Despite these differences in the dominant decomposer community, decay rates of eucalypt leaves (accounting for ≥98% of naturally occurring leaves in eucalypt bordered streams, absent in native forest) and chestnut leaves (occurring naturally in native forests) did not differ between the two groups of streams.     

Influence of Fruit Availability on Ecological Overlap among Four Neotropical Primates at Tinigua National Park,Colombia1

Data on fruit abundance and ecological overlap among Ateles belzebuth, Lagothrix lagothricha, Cebus apella, andAlouatta seniculus were gathered during 13 months at Tinigua National Park (Colombia), in an effort to test the following hypotheses concerning competition for fruits. Coexistence is possible because: (1) during periods when fruit availability is limited, the species utilize different resources; and (2) the species have different fruit preferences independent of fruit production in the forest. Differences were found in resource use (diet and habitat) for all four species. Despite these differences, all four devoted large proportions of time feeding on fruit. Fruit abundance influenced their activity patterns. Ninety percent of all interspecific aggressive interactions (TV = 69) were seen in fruiting trees. The first hypothesis was best supported, given that all species significantly increased their intake of the vegetative parts of plants during periods of fruit scarcity. Fruit partitioning during periods of scarcity was observed clearly only for one pair of species (C. apella and L. lagothricha). In general, the second hypothesis was not supported as a mechanism for reducing competition because most fruit species were consumed by more than one primate species. Fruit preferences, however, may be particularly important in explaining differences in niche overlap between the most ecologically similar species: A. belzebuth relied heavily on the fruits of one palm species (Oenocarpus bataud) during periods of fruit scarcity and abundance, while L. lagothricha completely ignored this fruit.     

Response of 11 eucalyptus species to inoculation with three arbuscular mycorrhizal fungi

 Numerous publications have reported growth stimulation of Eucalyptus following ectomycorrhizal inoculation in nursery or field conditions. Although Eucalyptus species can also form arbuscular mycorrhiza, their dependency on this type of mycorrhiza is still debatable. This paper presents information on the effect of inoculation of arbuscular mycorrhizal fungi on eucalypt growth. Twenty weeks after mycorrhizal inoculation, Eucalyptus seedlings' stem dry weight could be increased up to 49% compared to non-inoculated control plants. Intensity of root colonization by a given fungus depended on the host species, but it was not related to a plant growth response. Leaf phosphorus concentration of non-inoculated Eucalyptus seedlings varied greatly between species. Increases in leaf phosphorus concentration following mycorrhizal infection were not necessarily associated with plant growth stimulation. The most mycorrhiza-dependent Eucalyptus species tended to be those having the highest leaf phosphorus concentration in the absence of a fungal symbiont. These mycorrhiza-dependent Eucalyptus species seem to have greater phosphorus requirements and consequently to rely more on the symbiotic association. Accepted: 1 September 1995     

Do Eucalyptus plantations host an insect community similar to remnant Eucalyptus forest?

Abstract We examined the potential of forest plantations to support communities of forest‐using insects when planted into an area with greatly reduced native forest cover. We surveyed the insect fauna of Eucalyptus globulus (Myrtaceae) plantations and native Eucalyptus marginata dominated remnant woodland in south‐western Australia, comparing edge to interior habitats, and plantations surrounded by a pastoral matrix to plantations adjacent to native remnants. We also surveyed insects in open pasture. Analyses focused on three major insect orders: Coleoptera, Lepidoptera and Hymenoptera. Plantations were found to support many forest‐using insect species, but the fauna had an overall composition that was distinct from the remnant forest. The pasture fauna had more in common with plantations than forest remnants. Insect communities of plantations were different from native forest both because fewer insect species were present, and because they had a few more abundant insect species. Some of the dominant species in plantations were known forestry pests. One pest species (Gonipterus scutellatus) was also very abundant in remnant forest, although it was only recently first recorded in Western Australia. It may be that plantation forestry provided an ecological bridge that facilitated invasion of the native forest by this nonendemic pest species. Plantation communities had more leaf‐feeding moths and beetles than remnant forests. Plantations also had fewer ants, bees, evanioid wasps and predatory canopy beetles than remnants, but predatory beetles were more common in the understory of plantations than remnants. Use of broad spectrum insecticides in plantations might limit the ability of these natural enemies to regulate herbivore populations. There were only weak indications of differences in composition of the fauna at habitat edges and no consistent differences between the fauna of plantations adjacent to remnant vegetation and those surrounded by agriculture, suggesting that there is little scope for managing biodiversity outcomes by choosing different edge to interior ratios or by locating plantations near or far from remnants.     

Environmental effects on growth phenology of co-occurring Eucalyptus species

Growth is one of the most important phenological cycles in a plant’s life. Higher growth rates increase the competitive ability, survival and recruitment and can provide a measure of a plant’s adaptive capacity to climate variability and change. This study identified the growth relationship of six Eucalyptus species to variations in temperature, soil moisture availability, photoperiod length and air humidity over 12 months. The six species represent two naturally co-occurring groups of three species each representing warm-dry and the cool-moist sclerophyll forests, respectively. Warm-dry eucalypts were found to be more tolerant of higher temperatures and lower air humidity than the cool-moist eucalypts. Within groups, species-specific responses were detected with Eucalyptus microcarpa having the widest phenological niche of the warm-dry species, exhibiting greater resistance to high temperature and lower air humidity. Temperature dependent photoperiodic responses were exhibited by all the species except Eucalyptus tricarpa and Eucalyptus sieberi, which were able to maintain growth as photoperiod shortened but temperature requirements were fulfilled. Eucalyptus obliqua exhibited a flexible growth rate and tolerance to moisture limitation which enables it to maintain its growth rate as water availability changes. The wider temperature niche exhibited by E. sieberi compared with E. obliqua and Eucalyptus radiata may improve its competitive ability over these species where winters are warm and moisture does not limit growth. With climate change expected to result in warmer and drier conditions in south-east Australia, the findings of this study suggest all cool-moist species will likely suffer negative effects on growth while the warm-dry species may still maintain current growth rates. Our findings highlight that climate driven shifts in growth phenology will likely occur as climate changes and this may facilitate changes in tree communities by altering inter-specific competition.     

Is decline in high altitude eucalypt forests related to rainforest understorey development and altered soil bacteria following the long absence of fire?

Abstract The objective of this study was to identify attributes of the understorey vegetation, soil root biomass, soil chemistry and microbial community that may be associated with tree decline in high altitude eucalypt forests in Tasmania. The sites studied were in healthy eucalypt forest, forest in decline and forest containing dead eucalypts dominated by rainforest, in north‐east (Eucalyptus delegatensis forest) and in north‐west (Eucalyptus coccifera forest) Tasmania. In both regions bare ground, rock and shrubby species were associated with healthy sites whereas decline sites were associated with moss and a tall understorey with a high percentage cover of rainforest species. Healthy sites had low root biomass in the top 10 cm of the soil profile relative to decline and rainforest sites. Seedlings of high altitude species were grown in rainforest soil (0.314% N and 0.060% P) and healthy eucalypt soil (0.253% N and 0.018% P). The four eucalypt species studied had similar root to shoot ratio in the two soils, but the rainforest species, Nothofagus cunninghamii and Leptospermum lanigerum, had higher root to shoot ratio in the healthy eucalypt than in the rainforest soil. We produced three soil filtrates: (i) fungi and bacteria present; (ii) bacteria only present and; and (iii) sterile, from healthy, decline and rainforest sites in north‐east and in north‐west Tasmania and used linseed as a germination bioassay. Filtrates from the north‐east decline and rainforest sites induced a significantly greater dysplastic germination response than healthy sites in (i) and (ii) filtrates, but this was not found in filtrates from sites in the north‐west. We conclude that while the development of a rainforest understorey and elevated soil root biomass in the long absence of fire is generally associated with high altitude eucalypt decline, altered bacterial and/or chemical attributes of soil are not always associated with high altitude eucalypt decline.     

Overlapping trophic niches among co‐occurring amphipods from a cryptic species complex

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舟山群岛次生林优势种群的生态位与种间联结

为探讨舟山群岛次生林优势种群的关系,对桃花岛1 hm2固定样地进行调查,分析了15个优势种群的生态位特征和种间联结性。结果表明,豹皮樟(Litsea coreana var.sinensis)、红楠(Machilus thunbergii)和野梧桐(Mallotus japonicus)具有较大的生态位宽度,其Levins生态位宽度分别为1.3563、1.3170、1.3097,Hurlbert生态位宽度分别为0.8572、0.7373、0.7154,而朴树(Celtis sinensis)、柘(Maclura tricuspidata)和梾木(Cornus macrophylla)的生态位宽度较小。生态位相似比例大于0.5的种对有39对,占总对数的37.1%。生态位宽度大的种群之间相似比例较大,生态位宽度大的种群与生态位宽度小的种群也可能产生较大的重叠值,而生态位宽度小的种群一般不会与生态位宽度大的种群产生较大的重叠值。15个优势种群间总体呈现不显著负关联性,X2检验和联结系数结果均表明,负联结的种对较正联结的种对多。因此,舟山群岛次生林优势种群种间联结相对松散,具有一定独立性,但独立程度较低,群落尚不成熟,处于动态演替的不稳定阶段。阳性先锋树种天仙果处于衰退阶段,次生林将逐渐恢复成豹皮樟和红楠占优势的地带性常绿阔叶林。     

Livestock grazing and forest structure regulate the assembly of ecological clusters within plant networks in eastern Australia

Questions

How do changes in grazing intensity by different herbivores and differences in forest structure affect the assembly of ecological clusters within plant ecological networks in dryland plant communities?

Location

Eastern Australia across an area of 0.4 million km².

Methods

We used correlation network analysis and structural equation modelling to examine how changes in grazing intensity, by different herbivores, and differences in forest structure (tree canopy cover, basal area and density) and soil fertility influenced the assembly of ecological clusters of plant communities (i.e. relative abundance of ecological clusters formed by co‐occurring plant species within an ecological network) in three forested communities from eastern Australia.

Results

Livestock grazing and forest structure regulated the relative abundance of ecological clusters within plant networks, but their effects on these plant assemblies were highly dependent on the ecological cluster and forest community type, with no single winner or loser across forest types, conditions or grazing intensities. Thus, the relative abundance of some ecological clusters increased under grazing while others declined, a response that was maintained across different forest structures. The relative importance of grazing, forest structure and soil fertility varied across forest community type. The two eucalypt communities exhibited mixed effects of grazing and forest structure (Eucalyptus largiflorens ) or forest structure only (Eucalyptus camaldulensis ). In the third (Callitris glaucophylla ) community, grazing played a larger role in controlling the plant community assembly. Soil fertility (soil C and P) effects were of a similar magnitude to grazing and forest structure, but the effects differed among clusters.

Conclusions

Livestock grazing and forest structure regulated the relative abundance of ecological clusters within networks of plant communities in forests in eastern Australia. Our study uses a novel approach of ecological clusters to show that differences in grazing and forest structure will always disadvantage some plant ecological clusters. Furthermore, changes in one cluster will ultimately affect other clusters. Any changes in management therefore will have varied effects on different ecological plant clusters.

     

Landscape drivers of genomic diversity and divergence in woodland Eucalyptus

Spatial genetic patterns are influenced by numerous factors, and they can vary even among coexisting, closely related species due to differences in dispersal and selection. Eucalyptus (L'Héritier 1789; the “eucalypts”) are foundation tree species that provide essential habitat and modulate ecosystem services throughout Australia. Here we present a study of landscape genomic variation in two woodland eucalypt species, using whole‐genome sequencing of 388 individuals of Eucalyptus albens and Eucalyptus sideroxylon. We found exceptionally high genetic diversity (π ≈ 0.05) and low genome‐wide, interspecific differentiation (F_ST = 0.15) and intraspecific differentiation between localities (F_ST ≈ 0.01–0.02). We found no support for strong, discrete population structure, but found substantial support for isolation by geographic distance (IBD) in both species. Using generalized dissimilarity modelling, we identified additional isolation by environment (IBE). Eucalyptus albens showed moderate IBD, and environmental variables have a small but significant amount of additional predictive power (i.e. IBE). Eucalyptus sideroxylon showed much stronger IBD and moderate IBE. These results highlight the vast adaptive potential of these species and set the stage for testing evolutionary hypotheses of interspecific adaptive differentiation across environments.