David R. Genney

Dictyonema coppinsii , a new name for the European species known as Dictyonema interruptum (Basidiomycota: Agaricales : Hygrophoraceae ), with a validation of its photobiont Rhizonema (Cyanoprokaryota: Nostocales : Rhizonemataceae )

The lichenized basidiomycete known as Dictyonema interruptum is a widely distributed but rare, oceanic, western European species known from the British Isles, the Pyrenees, the Azores, and Madeira. Unfortunately, the name has never been validly published. The species was first described in the cyanobacterial genus Calothrix in 1833, which predates the starting point of heterocystous bacterial nomenclature, 1 January 1886. The epithet was never subsequently included in a validly published binomial and its combination into Dictyonema was therefore invalid as well. There was also controversy about whether the epithet applied to the cyanobacterial photobiont (as originally intended) or to the lichen fungus (as proposed later). Because of the lack of a valid description for this epithet, we have chosen to establish a new name, Dictyonema coppinsii Lucking, Barrie & Genney, for the lichenized fungus at hand, whereas the cyanobacterial photobiont is validated with the genus name Rhizonema Lucking & Barrie, adopting the epithet interruptum for it, and placed in a separate family, Rhizonemataceae Budel & Kauff ex Lucking & Barrie.

Fifty years of vegetation change in oceanic-montane liverwort-rich heath in Scotland

Background: Liverwort heath is considered in Scotland to be one of the vegetation types most vulnerable to environmental change, yet detailed insights into its dynamics are lacking. Aims: To assess the nature and extent of plant compositional changes in liverwort heath over 50 years and relate this to environmental change drivers. Methods: Vegetation plots previously recorded 20 and 50 years ago were re-surveyed to assess changes in species composition, plot-level species richness and between-plot variability, using several β-diversity indices and partitioning. The environmental indicator values of the species that showed most change were used to identify the environmental drivers of change. Results: Liverwort heath in north-west Scotland has undergone compositional changes over 50 years, becoming more heterogeneous, and losing some of its distinct character. Dwarf shrubs and specialist liverworts have decreased, while graminoids have increased. Partitioning of change in β diversity indicated that mainly changes in species richness, rather than species turnover, have driven the taxonomic differentiation over time. Grazing, eutrophication and warmer and drier conditions were found to be potentially important drivers of the observed vegetation change. Conclusions: Our results highlight the vulnerability of liverwort heath to environmental change.

Regeneration capacity of oceanic-montane liverworts: implications for community distribution and conservation

Abstract Scotland’s mountains are home to a rare and unique liverwort community, ‘the oceanic-montane liverwort-rich heath’, but its component species are absent from regions where they could potentially thrive. Many biological characteristics of these species are unknown, making it impossible to explain the reasons for their rarity; however, they have not been observed to produce sporophytes within Britain. We use ex situ cultivation of whole liverworts and fragments, and in situ cultivation of fragments, to assess the growth rate and the potential for vegetative reproduction of several species. Most of the species grew from both fragments and as whole plants, indicating that the rarity of the liverwort heath is not due to poor powers of regeneration. We propose that growth rate and the potential to regenerate from fragments are important factors structuring the liverwort heath community, at least locally. Furthermore, this study demonstrates that there is potential for ex situ conservation of rare liverwort species, in situ enhancement of existing populations, and creation of new ones.

Developing monitoring protocols for cost-effective surveillance of lichens

The criteria set out by the International Union for Conservation of Nature to identify threatened species requires information on population trends which, for priority lichen species within Scotland, is lacking. Collecting such data is problematic as there is a lack of empirical information on the performance of different sampling designs and survey methodologies. Using Pseudocyphellaria norvegica as an example species, we tested differences in the efficiency of 3 transect patterns and a 20 minute search for surveying 100×100 m cells of potentially suitable habitat. The methods were not intended to census the total population of the cells but, rather, to provide a standardized, repeatable estimate of the population density to allow detection of trends through time. We also tested the repeatability of the methods between surveyors. The results provided no evidence to suggest that controlled survey methodologies using fixed transect patterns were any better in terms of consistency between surveyors or numbers of occupied trees found than 20 minute searches of the areas within each 100×100 m cell deemed suitable for the target species by an experienced surveyor. Given that following the fixed transect patterns took approximately twice as long as a 20 minute search, the search method would clearly be more cost-effective when there are large numbers of cells to survey. For all survey methods variability between surveyors was high, meaning that it would be extremely difficult to detect temporal changes in populations, and hence identify population trends. We also examined the extent to which recording presence/absence at the 1 ha scale might improve consistency between surveyors and found that it reduced, but did not eliminate, the surveyor variability. Recording only presence/absence would allow greater numbers of cells to be surveyed using the same level of resources, but would reduce the amount of information available per cell for use in analysis of population trends. We conclude that controlling inter-surveyor variability while collecting adequate data for population trend analysis is a major issue when planning and implementing any large-scale survey of lichen species.

A molecular approach to explore the extent of the threatened fungus Hypocreopsis rhododendri within wood

Hypocreopsis rhododendri is a rare fungus that grows on woody stems in hyperoceanic climax scrub on the west coasts of Britain, Ireland, and France. Knowledge of the distribution and abundance of the fungus is based entirely on sporocarp records; it does not account for any occurrence as vegetative mycelia. To address this issue, a H. rhododendri-specific polymerase chain reaction (PCR) was developed and used to assay Corylus avellana (hazel) stems for the presence of H. rhododendri mycelia. The primers ITSHrF and ITSHrR were designed within the internal transcribed spacer 2 region, and their specificity to H. rhododendri was established by their failure to amplify DNA extracted from 14 other Hypocreaceae species. The sensitivity of the assay was demonstrated by amplifying DNA extracted from 4 mg C. avellana wood spiked with 0.0013 % H. rhododendri mycelium. Samples of wood and bark were then taken from around and directly underneath 11 H. rhododendri sporocarps and assayed for the presence of H. rhododendri. PCR products were obtained from a third of the surface bark samples, but only one faint product was obtained from 70 samples taken from beneath the outer bark. The results support the view that H. rhododendri does not form mycelia within stems. We suggest that H. rhododendri is not a saprotrophic fungus, but instead appears to be a parasitic on the wood decay fungus Hymenochaete corrugata, with which it always occurs. Evidence that tissue of H. corrugata is present within the sporocarps of H. rhododendri is discussed.

Understorey plant community composition reflects invasion history decades after invasive Rhododendron has been removed

A growing awareness of the destructive effects of non-native invasive species has led to a massive increase in removal programmes around the world. However, little is generally known about what happens to sites following the removal of the invasives and the implicit assumption that the native community will return, unaided, to pre-invasion conditions is often left untested. n n nWe assessed recovery of the native understorey plant community following removal of the non-native invasive Rhododendron ponticum L. from Scottish Atlantic oak woodland. We recorded understorey community composition in sites covering a gradient of increasing R. ponticum density, and across a separate series of sites covering a chronosequence of time since R. ponticum removal. We then compared both of these series to the target community found in uninvaded sites. We also analysed differences in soil chemistry between the sites to test for chemical legacy effects of invasion in the soil. n n nNative understorey cover declined as R. ponticum density increased, with bryophytes dropping to less than a third of the cover present in uninvaded sites and forbs and grasses being completely extirpated under dense stands. n n nCleared sites showed no evidence of returning to the target community, even after 30xa0years of recovery, and instead formed a bryophyte-dominated “novel community,” containing few of the typical oak woodland vascular plants. n n nContrary to expectation, soil pH, C:N ratio and nutrient concentrations (N, P, K, Ca and Mg) were not affected by the invasion of R. ponticum, and chemical legacy effects in the soil were not responsible for the failure of the native community to revert to pre-invasion conditions. Instead, we hypothesise that the rapid formation of a bryophyte mat, coupled with the often substantial distances to potential seed sources, hindered vascular plant recolonisation. n n nSynthesis and applications. Clear evidence of invasion history can be detected in the understorey plant community even decades after the successful removal of the invasive Rhododendron ponticum L. This finding demonstrates that native communities may be unable to recover effectively of their own accord following invasive species removal, and will require further management interventions in order to achieve restoration goals.

Transplanting the leafy liverwort Herbertus hutchinsiae : A suitable conservation tool to maintain oceanic-montane liverwort-rich heath?

Background: Translocating plants for conservation purposes can be a useful tool to enhance existing populations, restore lost populations or create new ones, but has rarely been done for bryophytes, especially liverworts. Aims: Here, the leafy liverwort Herbertus hutchinsiae, a representative species of oceanic-montane liverwort-rich heath, was translocated to unoccupied habitat within its current range, to establish whether its restricted distribution is due to habitat or dispersal limitation. Methods: Feasibility of establishing new populations outside the current distribution range was assessed, to test the suitability of the species for assisted colonisation. Furthermore, transplants were grown at degraded sites where the species had declined to assess potential for restoration. Results: Although maximal growth rates occurred within-range, transplants grew at all sites, indicating that the species could be dispersal limited; a conclusion supported by distribution modelling. Conclusions: Assisted colonisation is thus an option for this species to overcome dispersal limitation and to track future climate space. Reinforcement of populations at degraded sites is only recommended if the pressure causing the degradation has been removed. These findings provide an evidence base for practical conservation management.

Invasion by Rhododendron ponticum depletes the native seed bank with long-term impacts after its removal

The soil seed bank plays an important role in determining what plant species emerge following the removal of monodominant invasive species. A depleted seed bank may provide a substantial barrier to site restoration, however, little is known about what changes occur in the seed bank during invasion and following clearance. This study used greenhouse germination trials to quantify and compare the seed bank present in 30 Scottish Atlantic oak woodland sites under three treatments: (1) sites featuring dense stands of the non-native invasive shrub Rhododendron ponticum; (2) sites that had been previously subject to dense R. ponticum stands but which had been cleared; and (3) uninvaded control sites. Seed banks of densely invaded and cleared sites had significantly lower species richness than those of uninvaded control sites with a lower abundance of graminoid, and to a lesser extent forb seeds than the uninvaded controls. The seed bank community composition differed significantly between the three site types. Uninvaded sites featured a wide array of species, densely invaded sites were dominated by R. ponticum seeds and cleared sites were dominated by birch (Betula sp.) seeds. Cleared sites contained very few R. ponticum seeds indicating that once effective clearance had been achieved, re-invasion would be unlikely to occur from the soil seed bank. Our findings revealed that the soil seed bank present in cleared sites was very different from the seed bank of uninvaded control sites, with clear implications for site restoration.

A method for the direct detection of airborne dispersal in lichens.

This study sets out a novel method to determine dispersal distances in lichens. Direct measurement of dispersal often remains difficult for lichens and other small inconspicuous species because of the need to track microscopic reproductive propagules, which even if they can be captured, cannot be identified using traditional morphological approaches. A low‐cost device (<£200) was developed to trap the reproductive propagules of lichens, capable of sampling around 0.1 m3 of air per minute. In parallel, molecular techniques were developed to enable species‐specific detection of propagules caught by the devices, with identification using novel species‐specific primers and optimization of a standard DNA extraction and nested PCR protocol. The methods were tested for both their sensitivity and specificity against a suite of lichen epiphytes, differing in their reproductive mechanisms, dispersal structures and rarity. Sensitivity tests showed that the molecular techniques could detect a single asexual propagule (soredium or isidium), or as few as 10 sexual spores. As proof of concept, propagule traps were deployed into a wooded landscape where the target epiphytes were present. Extractions from deployed propagule traps were sequenced, showing that the method was able to detect the presence of the target species in the atmosphere. As far as we are aware, this is the first attempt to use mechanized propagule traps in combination with DNA diagnostics to detect dispersal of lichens. The tests carried out here point the way for future dispersal studies of lichen epiphytes and other passively dispersed microscopic organisms including fungi or bryophytes.

Tiny niches and translocations: the challenge of identifying suitable recipient sites for small and immobile species

Assisted colonisation, one form of species translocation, has been proposed as a tool for helping species to track suitable conditions in a changing climate. There are considerable practical challenges associated with it, including predicting where to place translocated individuals. This problem may be particularly big for small and immobile species, where small-scale micro-environmental conditions de-couple them from environmental conditions as projected in large-scale climate models. nTo investigate this problem we developed a survey-based model to predict the occurrence of our target species, the fruticose terricolous arctic-alpine lichen, Flavocetraria nivalis, within the Cairngorm Mountains. nWe then undertook an experimental translocation of this species. A second model, using variables that were significant in the survey-based model, was only fair at predicting the initial pattern of survival at the recipient site. nHowever, model fit of the translocation survival model improved over time as the distribution of surviving individuals more accurately reflected the distribution of suitable environmental conditions. In addition, model predictive power increased with the addition of data on micro-climatic conditions at recipient plots. nSynthesis and applications. Our results demonstrate that, for species which respond strongly to local environmental conditions, are immobile and, to some extent, decoupled from larger-scale climates, it may be difficult to build a priori accurate predictive models of habitat suitability. In these cases, a combination of modelling and expert judgement, along with the movement of substantial numbers of transplants, may be the appropriate options for maximising the success of assisted colonisation. n n nThis article is protected by copyright. All rights reserved.