Community effects following the deletion of a habitat-forming alga from rocky marine shores

Habitat-forming species increase spatial complexity and alter local environmental conditions, often facilitating a diversified assemblage of plants and animals. Removal of dominant species, therefore, can potentially lead to pronounced changes in diversity and community structure through a series of negative and positive interactions involving several components of the community. Here we test community responses to the deletion of the dominant, canopy-forming alga Hormosira banksii from the mid-intertidal zone of wave-protected rocky shores in southern New Zealand. This species was removed in winter (July) from three 3×3-m areas at each of two platforms (Kaikoura and Moeraki) on the east coast of the South Island. Initially, 59 taxa occurred in stands, but there were only four algal species with greater than 5% cover and three mobile invertebrate species with more than five individuals per 0.25 m². By 6 months after Hormosira removal, most fucoid and coralline algae had burned off, and there were blooms of ephemeral algae in the removal plots, but almost no change within controls. After 2 years, diversity declined by 44% relative to controls at Kaikoura and 36% at Moeraki, and the amount of bare space had increased by tenfold at Kaikoura and twofold at Moeraki. Few sessile or mobile invertebrates were present. Recruitment of Hormosira occurred after 14 months in the removal plots. At this time, a “press” disturbance was initiated into one half of each removal plot to test the effects of continued removal of Hormosira on diversity. Similar “end-points” of the control and “press” removal plots were not reached after 2 years, and even after Hormosira recruitment into the original “pulse” experiment there was little recovery of the community. In this mid-intertidal system with considerable thermal stress, and perhaps in others with few perennial species, diversity and community structure can critically depend on positive associations with a single dominant species.Electronic Supplementary Material Supplementary material is available for this article at and is accessible for authorized users.     

Plant community response following the removal of the invasive Lupinus arboreus in a coastal dune system

The removal of invasive species is common in restoration projects, yet the long‐term effects of pest management programs are seldom assessed. We present results of a long‐term program to remove the invasive species Lupinus arboreus (lupin) from sand dunes in New Zealand. We evaluate the response of plant communities to lupin removal, by comparing total plant cover, the cover of non‐native and native plant species, and species richness between sand dune sites where lupin removal has occurred, not occurred, and where lupin has never been present. Neither lupin presence nor removal had a significant impact on the foredune environment. Following removal, total and other non‐native plant cover remained higher, and the cover of several native sand dune species remained lower compared with uninvaded sites in the deflation and backdune environments. These changes can be attributed to persistent effects associated with the invasion of lupin, but have also developed in response to lupin removal. The results of this study have implications for restoration projects in sand dunes. Pest management alone is unlikely to be sufficient to restore plant communities. Given the difficulties in restoring plant communities once an invasive species has established, managers should prioritize actions to prevent the spread of invasive species into uninvaded areas of sand dunes. Finally, the response to lupin invasion and removal differed between dune habitats. This highlights the importance of tailoring a pest management program to restoration goals by, for example, prioritizing areas in which the impacts of the invading species are greatest.     

Effects of consumers and enrichment on abundance and diversity of benthic algae in a rocky intertidal community

Human alteration of nutrient cycling and the densities of important consumers have intensified the importance of understanding how nutrients and consumers influence the structure of ecological systems. We examined the effects of both grazing and nutrient enrichment on algal abundance and diversity in a high-intertidal limpet-macroalgal community on the South Island of New Zealand, a relatively nutrient-poor environment. We used a fully factorial design with three levels each of grazing (manipulations of limpet and snail densities) and nutrients (nutrient-diffusers attached to the rock). Top-down control by grazers appears to be the driving organizing mechanism for algal communities in this system, with strong negative effects of grazing on algal diversity and abundance across all levels of nutrient enrichment. However, in contrast to the conclusions drawn from the analysis of the whole algal community, there was an interactive effect of grazing and enrichment on foliose algae, an important component of the algal system. When herbivory was reduced to very low levels, enrichment generated increases in the abundance and biomass of foliose algae. As expected, top-down control was the primary determinant of algal community structure in this system, controlling abundance and diversity of macrophytes on the upper shore. Contrary to expectations, however, increased nutrients had no community-wide effects, although foliose algal abundance increases were greatest with high nutrients and reduced grazing. It seems likely that most of the corticated algal species have limited capacity to respond to nutrient pulses in this nutrient-poor environment.     

Extinction and recolonization of coastal megafauna following human arrival in New Zealand

Extinctions can dramatically reshape biological communities. As a case in point, ancient mass extinction events apparently facilitated dramatic new evolutionary radiations of surviving lineages. However, scientists have yet to fully understand the consequences of more recent biological upheaval, such as the megafaunal extinctions that occurred globally over the past 50 kyr. New Zealand was the world''s last large landmass to be colonized by humans, and its exceptional archaeological record documents a vast number of vertebrate extinctions in the immediate aftermath of Polynesian arrival approximately AD 1280. This recently colonized archipelago thus presents an outstanding opportunity to test for rapid biological responses to extinction. Here, we use ancient DNA (aDNA) analysis to show that extinction of an endemic sea lion lineage (Phocarctos spp.) apparently facilitated a subsequent northward range expansion of a previously subantarctic-limited lineage. This finding parallels a similar extinction–replacement event in penguins (Megadyptes spp.). In both cases, an endemic mainland clade was completely eliminated soon after human arrival, and then replaced by a genetically divergent clade from the remote subantarctic region, all within the space of a few centuries. These data suggest that ecological and demographic processes can play a role in constraining lineage distributions, even for highly dispersive species, and highlight the potential for dynamic biological responses to extinction.     

Small-scale spatial dynamics of plant species in a grassland community over six years

Abstract. In a species-rich mountain grassland in the Krkonosse Mts., Czechoslovakia, data from four permanent plots of 50 cm x 50 cm were recorded annually from 1985 to 1990 to study the spatial dynamics of the species. Plots were divided into 15 x 15 subplots and the number of vegetative units of all plants within each subplot was determined. There was not much net change at the plot level, but the subplots were very dynamic. Two aspects of the spatial dynamics of the species were followed: (1) persistence, i.e. the tendency of the species to remain in the same subplot, and (2) long-distance spreading, i.e. movement to subplots beyond the immediate neighbourhood. Species differed widely in their persistence and longdistance spreading and were classified into mobility types: long-range guerrilla, short-range guerrilla, phalanx and 'sitting’. The mobility types were, to a certain extent, correlated with the growth form of plants, but some species of one growth form showed different types of small-scale dynamics and some species with different growth forms had the same spatial dynamics.     

Species richness, diversity and biomass production of desert annuals in an ungrazed Rhanterium epapposum community over three growth seasons in Kuwait

Two blocks, each consisting of twelve 0.25 m²permanent plots, were established in a community dominated by desert annuals inan area of Kuwait protected from grazing, and community attributes wereinvestigated over three growth seasons. A linear relationship was found betweenestimated desert annual cover and biomass production. Species frequency wasassessed by the number of 100 cm² subplots occupied byaspecies in a block (block incidence). Over the three seasons,vegetation features varied considerably. The first season (spring 1997) wascharacterised by very sparse vegetation cover, low vegetation block incidence(sum of individual block incidences of each species present in a block) and lowspecies richness. The second season (spring 1998) had high vegetation cover,relatively low vegetation block incidence, but high species richness. In thethird season (spring 2000), vegetation cover was very sparse (as in 1997), butboth blocks had the highest vegetation block incidence of the three years andspecies richness was moderately high, although individual plants were verysmall. The growth period was much shorter in the very productive andspecies-rich 1998 season than in 2000. Fluctuations in biomass and speciesincidence coincided with pronounced variation in key meteorological variables,in particular the onset of the first rains, the amount of rainfall during thegrowing season and its temporal distribution. Species composition, however,appears mainly to be determined by the amount and possibly the timing of thefirst rainfalls of the season to trigger germination. There was little evidenceto suggest that particularly favourable or unfavourable microsites existed inplots for more than one vegetation period, either for individual species or fordiversity in general. Despite substantial between-season fluctuations inincidence, the relative abundances of the more frequent species to each otherremained broadly similar over the three seasons, with Plantagoboissieri being the predominant species and accounting for thelargest proportion of biomass.     

大型无脊椎动物群落指数和群落数量指数在河流水质评价中的应用

本文介绍了新西兰常用的大型无脊椎动物群落指数(MCI)和大型无脊椎动物群落数量指数(QMCI)的原理及使用方法,并利用MCI和QMCI对新西兰惠灵顿地区40条河流53个监测点进行评价.结果表明:MCI和QMCI均与河流营养指标呈极显著相关关系,可用来监测和评价水体的营养污染状况;二者快速准确地监测出惠灵顿地区河流水质总体良好,但部分河流污染严重,并分析了污染的原因.MCI与QMCI存在极显著相关关系,但MCI与营养指标间的相关关系大于QMCI,可以准确地反映出水体中营养元素的富集状况.     

Invasion patterns across multiple scales by Hieracium species over 25 years in tussock grasslands of New Zealand's South Island

Studying patterns of species invasions over time at multiple spatial scales may help us to elucidate important factors driving those patterns and how they change according to temporal or spatial resolution. Here we provide a large, long‐term, landscape‐scale study of the invasion of three Hieracium species using a dataset that encompasses vegetation change on 124 transects over 25 years across the lower eastern South Island of New Zealand. We investigated the relationships between key environmental and ecological factors and the invasion trajectories of H. lepidulum, H. pilosella and H. praealtum, at two spatial scales: (i) among‐transect colonization and (ii) within‐transect changes in frequency and per cent cover. Our results show that the colonization and spread of Hieracium species among and within transects reflect (i) the importance of initial environmental and biological conditions, (ii) that our sampling captured different periods of the invasion trajectories of each of the three species, and (iii) the effects of differences in life histories of the three species.     

Rapid recovery of mammal fauna in the central Kimberley,northern Australia,following the removal of introduced herbivores

Australia has lost more native mammal species than any other country in the past two centuries, and this record of loss looks likely to worsen over the next few decades. Small‐ to medium‐sized mammals are declining in both distribution and density across large tracts of northern Australia's tropical savannas, including within protected areas. The most likely causes are a combination of changed fire patterns, the impacts of introduced herbivores and predation by feral cats. Here, in contrast to the prevailing trend across northern Australia, we report the recovery of native mammals in response to a large‐scale (>40 000 ha) destocking experiment carried out at Mornington Wildlife Sanctuary in the central Kimberley, north‐west Australia. Following the removal of introduced herbivores from 2004, the species richness and abundance of small native rodents and dasyurids increased significantly across all sampled habitats over the next 3 years. We discuss the implications of these results for guiding land management and applied research to help to reduce the impending risk of mammalian extinctions in northern Australia.     

Arbuscular mycorrhiza and Collembola interact in affecting community composition of saprotrophic microfungi

The functioning of the plant-mycorrhiza system depends on interactions with other organisms, including saprotrophic (ST) soil fungi. The interactions between mycorrhizal and ST fungi are likely affected by fungivorous soil animals, such as Collembola. In a two-factorial laboratory experiment lasting for 30 weeks we assessed the effects of an arbuscular mycorrhizal fungus (Glomus mosseae) and Collembola (Protaphorura fimata, Heteromurus nitidus and Folsomia candida) on the community composition of ST microfungi in soil planted with the invasive grass Cynodon dactylon. The presence of mycorrhiza substantially reduced total plant biomass and reduced N and P availability to the soil microflora, though these effects were less pronounced in the presence of Collembola. The density of Collembola was high (corresponding to about 2×10⁵ individuals m^–2) and was not affected by the presence of G. mosseae. In spite of the large amount of mycorrhizal mycelium in soil, it contributed little to Collembola nutrition. The presence of mycorrhiza strongly affected the community structure of ST soil fungi. In particular, mycorrhiza reduced the relative abundance of Trichoderma harzianum and Exophiala sp., but increased the abundance of Ramichloridium schulzeri and several sterile forms. However, the difference between fungal communities in mycorrhizal and non-mycorrhizal treatments was much more pronounced in the presence of Collembola. Presumably, the intense grazing by Collembola destabilized the ST fungal community, thereby making it more susceptible to the influence of G. mosseae. These results document for the first time that fungal feeding soil invertebrates can significantly affect the interactions between mycorrhizal fungi and ST soil microorganisms.     

A comparison of restoration techniques to accelerate recovery of litter decomposition and microbial activity in an experimental peat bog restoration trial

Restoration of mined Restionaceae-dominated peat bogs in northern New Zealand is currently initiated by establishing native vegetation cover to minimise erosion of the remaining peat. The relative effects of various restoration techniques on litter decomposition and microbial activity within experimental litter bags were investigated in a restoration trial established on a mined peat surface. Decomposition and microbial activity of litter were compared between four different restoration treatments: direct transfer of intact habitat ‘islands’; the addition of processed peat with seed; the addition of processed peat with no seed; and recently mined peat surface (a ‘do nothing’ restoration option), with the four treatments replicated at each of five distances from an undisturbed peat bog. Treatments were compared with an undisturbed peat bog (control). Litter decomposition and associated microbial respiration rates were significantly higher in the undisturbed peat bog sites than in any of the restoration treatments, but the technique used to restore mined peatlands did have a significant effect on these ecosystem process rates. Results suggest that ecosystem processes such as decomposition and microbial community activity recover faster with restoration techniques such as direct transfer of intact habitat islands, than with other techniques such as simple seed addition. However, even after 12 months, litter decomposition and microbial activity in restored habitats were still far from reaching the levels recorded in the undisturbed peat bog. In addition, there was a strong relationship between the effort (and cost) applied to plant community restoration treatments and the rate of decomposition and microbial community activity.     

Establishment of exotic parasites: the origins and characteristics of an avian malaria community in an isolated island avifauna

Knowledge of the processes favouring the establishment of exotic parasites is poor. Herein, we test the characteristics of successful exotic parasites that have co-established in the remote island archipelago of New Zealand, due to the introduction of numerous avian host species. Our results show that avian malaria parasites (AM; parasites of the genus Plasmodium) that successfully invaded are more globally generalist (both geographically widespread and with a broad taxonomic range of hosts) than AM parasites not co-introduced to New Zealand. Furthermore, the successful AM parasites are presently more prevalent in their native range than AM parasites found in the same native range but not co-introduced to New Zealand. This has resulted in an increased number and greater taxonomic diversity of AM parasites now in New Zealand.     

Emergent Impacts of Ant and Spider Interactions: Herbivory Reduction in a Tropical Savanna Tree

Multiple predators often have effects on their common prey populations that cannot be predicted by summing the effects of each predator at a time. When predators forage on the same vegetation substrate, intraguild interactions might cause emergent outcomes for the plants on which the predators co‐occur. We experimentally evaluated the effects of spiders and ants on herbivory and reproduction in the extrafloral nectary‐bearing tree Qualea multiflora (Vochysiaceae). Plants were divided in four experimental groups, depending on the presence or absence of ants and spiders. We compared the effects of each treatment on richness and abundance of chewing and sucking herbivores and on herbivory (leaf area loss). We also evaluated the impact of predators on the production of buds, fruits and seeds, and weight of the fruits. The presence of ants reduced the abundance and richness of spiders, but spiders did not affect the abundance and richness of ants. Only the removal of ants resulted in a significant increase in the abundance of herbivores and herbivore richness. Herbivory, however, was also affected by spiders. In addition, we found a significant interaction effect of ants and spiders on herbivory, indicating an emergent multiple predator effect. Neither ants nor spiders had an impact on the number of buds produced, number of fruits per bud, and seeds per fruits or fruit weight. This study highlights the importance of evaluating the effect of the predator fauna as a whole and not only one specific group on herbivory.     

Examining carry‐over effects of winter habitat on breeding phenology and reproductive success in prairie warblers Setophaga discolor

Winter habitat quality can influence breeding phenology and reproductive success of migratory birds. Using stable isotope ratios of carbon (δ¹³C) from bird claws and red blood cells collected in Massachusetts, USA, we assessed if winter habitat occupancy carried over to affect prairie warbler Setophaga discolor breeding arrival dates, body condition upon arrival, pairing success, first‐egg dates and reproductive success. In two of three years (in 2011 and 2012, but not in 2013), after‐second‐year (ASY) males wintering in drier habitat, as indicated by enriched δ¹³C values, arrived later on the breeding grounds. Based on the North Atlantic Oscillation index, there was likely less rainfall in the Caribbean wintering grounds during the winters of 2011 and 2012 compared to the winter of 2013, suggesting increased winter rainfall in 2013 may have diminished the influence of winter habitat occupancy on arrival date. We did not find any effects of winter habitat on breeding season phenomena for second‐year (SY) males or females, but our sample sizes for these age/sex classes were relatively low. Although winter habitat quality influenced arrival dates of ASY males, there was no evidence that it affected reproductive performance, perhaps because of high rates of nest depredation in our system. Our study adds to a growing body of research that shows the influence of carry‐over effects can differ among species and within populations, and also can be modulated by other environmental conditions. This information enriches our understanding of the role of carry‐over effects in population limitation for migratory birds.     

Twenty years of research on community composition and species distribution of arbuscular mycorrhizal fungi in China: a review

The biodiversity and distribution of arbuscular mycorrhizal fungi (AMF) in different ecosystems and plant communities in China has received increasing interest over the past decades. This has led to a steady increase in the number of scientific papers published on this topic. Studies have surveyed AMF-colonizing rhizospheres of most families of angiosperms, bryophytes, pteridophytes, and gymnosperms. China has about 30,000 plant species (one eighth of the plant species worldwide). A total of 104 AMF species within nine genera, including 12 new species, have been reported in environments such as croplands, grasslands, forests, and numerous disturbed environments. In this paper, we review data published over the past 20 years on AMF community composition and species distribution, the mycorrhizal status of plants, AMF spore communities in different habitats, and germplasm collections in China. Possible future trends in the study of the biodiversity of AMF are also briefly discussed. In particular, the aim of our review is to make some of the recent work published in the Chinese literature accessible to a wider international audience.     

The relative importance of positive and negative interactions for pollinator attraction in a plant community

Plant–pollinator interactions provide ideal frameworks for studying interactions in plant communities. Despite the large potential influence of such interactions on plant community structure, biodiversity and evolutionary processes, we know surprisingly little about the relative importance of positive and negative interactions among plant species for pollinator attraction. Therefore, we explored the relationships between conspecific and heterospecific floral densities and the flower visitation rates of nine plant species mainly visited by bumble bees, and six plant species mainly visited by flies, in a temperate grassland, through stepwise multiple regressions. Significant relationships were interpreted as interactions for pollinator attraction. Our results revealed that positive intra- and interspecific interactions for pollinator attraction were far more frequent than negative ones. Seventeen interspecific interactions were revealed of which 14 were significantly positive, whereas three of four significant intraspecific interactions were positive. Seven species experienced only positive interactions and two species experienced only negative interactions. The results presented here indicate that negative interactions are not necessarily the dominant ecological interaction for pollination among plants within a community, and the study represents a straightforward approach to study intra- and interspecific interactions among multiple species within a community. We discuss which mechanisms may drive the positive interactions for pollinator attraction and whether this may result in facilitative effects on reproductive success. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Changes in soil and vegetation following stabilisation of dunes in the southeastern fringe of the Tengger Desert, China

Properties of the soil and sand-binding vegetation were measured at five sites plus a control on dunes of the Tengger Desert stabilized for periods of up to 50 years. In the topsoil, fine particles, total N, P, K and organic matter increased significantly with increasing site age. However, there were no significant changes in deeper soil profiles (>0.4 m depth). Soil pH, calcium carbonate content, and total salt content tended to increase with age. Soil water in the topsoil changed little with increasing age, but was closely related to rainfall during the 50-year period. For deeper soil layers (0.4–3.0 m) soil water decreased significantly with age. After revegetation, the number of herbaceous species increased up to 30 years and then levelled off to 12–14 species, whereas the number of shrub species decreased from the 10 initial sand-binding species to only 3 species. Shrub cover decreased from a highest average of about 33% to the current 9%, whereas cover and biomass of herbaceous species increased throughout succession from 1956 to 2006. The development of soil and cryptogamic crusts on the surface of stabilized dunes enhanced the colonization and establishment of herbaceous plants due to increasing water availability, clay and silt content and soil nutrients. We propose that changes in properties of the surface soil led to increased interception of water, favoring shallow rooted grasses and forbs over perennial shrubs.     

Perturbation and delayed recovery of the reed invertebrate assemblage in Camargue marshes sprayed with Bacillus thuringiensis israelensis

Bacillus thuringiensis var. israelensis (Bti) is the most commonly used larvicide to control mosquitoes worldwide. Considered as nontoxic to most organisms, Bti can nevertheless cause trophic perturbations to natural communities by reducing the abundance of Chironomidae, which are a key element of wetland food webs. Since August 2006, up to 8400 of the 33 000 ha of mosquito larval biotopes in the Camargue (Rhône delta, in southern France), are monitored by a public agency and Bti‐sprayed (aqueous solution of VectoBac 12AS at 2.5 L/ha) whenever mosquito larvae (Ochlerotatus caspius and Oc. detritus) appeared in water bodies. This resulted in 30–50 aerial treatments/year, in addition to ground spraying of unknown frequency. The sprayed habitats include Phragmites australis reedbeds, which support a specific avifauna of conservation concern. We compared the abundance of invertebrate prey available to passerine birds at treated and control sites relative to the predicted values based on hydrology over a 9‐year period. Food available to reed passerines was significantly reduced at treated areas, translating into a 34% decrease in breeding birds based on predictive modeling. The most affected arthropods were Diptera, Aranaea, Coleoptera, and Hymenoptera. No cumulative effects were observed over time, but the recovery of the invertebrate assemblage after the cessation of mosquito control was delayed due to Bti spore persistence and proliferation in the sediments. While hydrology remains a prime factor influencing primary and secondary productivity of the Camargue reed marshes, Bti spraying had significant negative effects on animal communities at several trophic levels.