Salgado, J., Sayer, C. D., Willby, N., Baker, A. G., Goldsmith, B., McGowan, S., Davidson, T. A., Bexell, P., Patmore, I. R. & Okamura, B. (2021) Habitat heterogeneity enables spatial and temporal coexistence of native and invasive macrophytes in shallow lake landscapes. River Research and Applications. https://doi.org/10.1002/rra.3839
First published: 15 July 2021
Macrophyte invasive alien species (IAS) fitness is often hypothesised to be associated with beneficial environmental conditions (environmental matching) or species-poor communities. However, positive correlations between macrophyte IAS abundance and native plant richness can also arise, due to habitat heterogeneity (defined here as variation in abiotic and native biotic conditions over space and time). We analysed survey and palaeoecological data for macrophytes in satellite lakes along the Upper Lough Erne (ULE) system (Northern Ireland, UK), covering a gradient of eutrophication and connectivity to partition how environmental conditions, macrophyte diversity and habitat heterogeneity explained the abundance of Elodea canadensis, a widely distributed non-native macrophyte in Europe. E. canadensis abundance positively correlated with macrophyte richness at both the within- and between-lake scales indicating coexistence of native and invasive species over time. E. canadensis was also more prolific in highly connected and macrophyte-rich lakes, but sparser in the more eutrophic-isolated ones. Partial boosted regression trees revealed that in eutrophic-isolated lakes, E. canadensis abundances correlated with water clarity (negatively), plant diversity (positively), and plant cover (negatively) whereas in diverse-connected lakes, beta diversity (both positively and negatively) related to most greatly E. canadensis abundance. Dense macrophyte cover and unfavourable environmental conditions thus appear to confer invasibility resistance and sufficient habitat heterogeneity to mask any single effect of native biodiversity or environmental matching in controlling E. canadensis abundance. Therefore, in shallow lake landscapes, habitat heterogeneity variously enables the coexistence of native macrophytes and E. canadensis, reducing the often-described homogenisation effects of invasive macrophytes.
I am sharing a diagram drawn as a memory aid to support field botanists remembering the origins of the species and hybrids of mints find in Britain and Ireland (genus Mentha). It is based on Stace IV and R. M. Harley’s account of the genus Mentha in Stace et al. 2015. Hybrid Flora of the British Isles. The diagram does not reflects the full complexity of each taxa and is a simplification based on best current knowledge. In addition, it does not include the interesting new insights presented in Heylen et al 2021.
This blog post reports on the discovery of a small population of Acaena inermis near Danby Beacon in the North York Moors National Park. Unlike other piri piri bur species such as A. novae-zelandiae (e.g. Invasive Species Compendium, CABI, 2021, https://www.cabi.org/isc/datasheet/111979), A. inermis is not known as an undesirable alien, however population dynamic is relatively unknown in Britain.
The population described here is nonetheless of biological interest based on the distance to known records and the site being located within a designated area for nature conservation. It is also an opportunity to highlight the species and some of its characteristics to other field botanists and conservationists, hopefully to improve recording coverage.
Distribution in Britain and Ireland and description of the Danby Beacon location
A. inermis is a relatively rare alien plant in Britain and Ireland, with scattered records from lowland location (from Southern England to Edinburg) and a few well known clusters of records from upland natural habitats: Isle of Skye, the Grampians, the Southern Uplands of Scotland, and in England in the Cheviot Hills (Coquet dale). These small clusters of upland populations appear well established, some since the 1970s and the Skye population may be increasing with new sites having been reported in recent years (e.g. Bungard, 2019, https://skyeraasayplants.wordpress.com/2019/05/31/aliens-day/; BSBI 2021 map).
The new location reported here is isolated by about 100 km from three other English presences hitherto reported (South Yorkshire, Skipton area, Coquet Valley). Although there may be unknown sites in between that could have acted as stepping stones, the population presented here is more likely to be an independent introduction from cultivation into the wild.
At Danby Beacon, the population is located on a lay-by popular with visitor (NZ726085, at or adjacent to NZ726308656), with a lovely view to the SW, popular with visitors for picnics and for quiet time in a camping chair by the car. Due to this relative popularity, it can be speculated that propagules of the plant reached the site on car tyres. The propagules could have been directly brought from a garden or a drive way to to this lay-by by visitors of the national park. The habitat is a species rich acidic grasssland, with species such as Antennaria dioica, Euphrasia sp., Veronica officinalis, Galium saxatile, Nardus stricta, Festuca rubra, Cynosurus cristatus, Calluna vulgaris, Trifolium repens, Polygala serpyllifolia, Carex pilulifera, Pilosella officinals, Leontodon saxatile, and other species.
Invasives and conservation
Reporting the first introduction of alien plant in an area can be important to identify the pace and vectors of colonisation, especially in genera with well known undesirable species. The North York Moors national park authority, has already taken action against A. novae-zelandiae in one location and may want to keep on eye on this new comer in the area, until we know more about the population dynamic of A. inermis in the area. Acidic grassland where the population is located is a highly threatened habitats in Britain (see e.g. Carly Stevens 2011 paper).
Improving our understanding of A. inermis distribution
Acaena inermis is a species from New Zealand, first recorded in the wild in the Britain or Ireland in the 1970s. Identification of the Danby Beacon population was based on the CRIB account for Acaena (Yeo, 1988, https://bsbi.org/wp-content/uploads/dlm_uploads/Acaena_Crib.pdf). There is also abundant photography on the internet as the species is a popular rockery plant. The species, as well as one cultivated variety (Acaena inermis cv ‘Purpurea’) is widely available from nurseries for outdoor gardens. It is not clear to me whether the population described here belongs to this the ‘Purpurea’ cv or not, and even not clear from internet searches whether all specimens of this species can be found under the name ‘Purpurea’ due to the type colouration of the foliage. I would be keen to hear from experienced nursery-people on this point.
At the Danby Beacon site the plant is extremely difficult to spot due to its size, prostrate stem and colour, which mimics topsoil litter. In addition, the bright red spines that can develop on the fruits were not observed by the end of July 2021.
In my function of trustee and co-website editor, I was able to take part and co-lead the development of a major website for the British Bryological Society (BBS). The new website significantly improves the design, navigation, accessibility, functionality, SEO, and content, in comparison to our previous website – altogether strongly contributing to delivering the mission of the Society: promote a wider interest in all aspects of bryology.
I expect most people will fall in love with the featured photography and these tiny plants, but you will also found a wealth of scientific resources about bryophytes on the new website. There is more than one page per day in the year, each contains expert knowledge about bryophytes, about the Society itself… and even the lives of bygone bryologists.
The editorial will give you some background about the aims and justification for developing this blog website. I look forward to leading the editorial board initially and work alongside early carer researchers to transform the School’s research culture – let’s get writing!
Van Asperen, E.N., Perrotti, A.,Baker, A. (2020) Coprophilous fungal spores: NPPs for the study of past megaherbivores. Geological Society, London, Special Publications, 511, https://doi.org/10.1144/SP511-2020-41
Published online on Dec. 2020 /Jan. 2021
This publication, lead by my colleague Eline van Asperen, will be an invaluable resources to scholars researching past populations of megharbivores or other aspects of palaeoeology using non-pollen palynomorphs, whether be it for the MSc dissertation, PhD, postdoc or at any point of their career. It is supplemented by an open-access key to the identification of dung fungal spores, which supersedes that previously provided on this blog (but some may find useful to still have access to both!):
Spores from coprophilous fungi are some of the most widely used non-pollen palynomorphs. Over the last decades, these spores have become increasingly important as a proxy to study the Pleistocene and Holocene megafauna. Although the number of types used in palaeoecology is relatively small, there is a wide range of coprophilous fungal taxa whose utility in palaeoenvironmental reconstruction remains under-researched. However, environmental and taphonomic factors influencing preservation and recovery of these spores are still poorly understood. Furthermore, our understanding of whether and how spores are transported across the landscape is limited.
Dung fungal spore presence appears to correlate well with megaherbivore presence. However, depending on the site, some limitations can remain to quantitative reconstructions of megaherbivore abundance from dung fungal spore records. The presence of dung fungal spores is often more significant than their absence and variation in in abundance with time should be interpreted with caution. Correlation with other proxies may provide a promising way forward.
The majority of studies using dung fungal spores as an indicator for large herbivore abundance are of records of Late Pleistocene and Holocene age, with a focus on Late Quaternary megafaunal extinction. However, more research could potentially extend records further back in time.
Dr Ambroise Baker and Dr Jamie Bojko, are offering a unique opportunity to undertake PhD studies researching the recolonization and resilience of seals (Phoca vitulina and Halichoerus grypus) in the Tees estuary, UK, following heavy industrialisation. This project connects with local partners, veterinarians and conservation groups, who provide long-standing data sets of seal population size, disease and behaviour. These data, complemented by data collected during the project, will be used to develop a model of ecosystem recovery and explore a positive narrative for conservation.
This exciting project focuses on how the population dynamic of a charismatic apex predator responds to pollution, disease, and connectivity across the North Sea. The student will have an opportunity to undertake multidisciplinary research, and develop a unique range of skills, from multivariate quantitative analysis, data collection in the field as well as molecular work in our state-of-the-art laboratories. This is a fantastic chance to work with a range of collaborators, providing additional insights into a professional career in ecology. We are looking for candidates with a strong interest in molecular ecology and environmental science, with a positive approach to develop conservation solutions within coupled human-nature systems.
Any question, email Ambroise and Jamie – firstname.lastname@example.org and email@example.com
I simply can’t wait for the Festival of Ecology in Dec 2020, an all online event that replaces the British Ecological Society’s traditional in-person annual meeting this year. BES events are always a huge source of inspiration with talks from researchers around the World, discussions, and an opportunity to meet with long-time-no-see colleagues.
In addition, this year I am going to present some of my work on megafauna with a 15-mins talk:
Reviving the function of extinct megafauna: inspiration from the past
This website will contribute to raising the profile of our research and academic activities. The hope is that, as we are all individually growing our academic portfolios and that the group grows with new researchers joining, the site will grow into a go-to resource of information about our successes, for colleagues around the world, partners, at the university as well as for existing and prospective students.