New paper: Heterogeneity enables coexistence of native and invasive aquatic plants

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
Abstract:
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.

New Paper: Dung fungal spores for the study of past megaherbivores

Van Asperen, E.N., Perrotti, A., Baker, A. (2020) Coprophilous fungal spores: NPPs for the study of past megaherbivores.

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!):

https://doi.org/10.6084/m9.figshare.c.5240664

Abstract:

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.

New Paper: Late-Quaternary megaherbivore extinctions in interior Alaska

Conroy, K.J., Baker, A.G., Jones, V.J., van Hardenbroek, M., Hopla, E.J., Collier, R., Lister, A.M., Edwards, M.E. (2020) Tracking late-Quaternary extinctions in interior Alaska using megaherbivore bone remains and dung fungal spores. Quaternary Research. DOI: https://doi.org/10.1017/qua.2020.19

Article first published online:  28 April 2020

Read article by following this link, taking you to the Cambridge University Press Core collection.

This research is considerably questioning some of the accepted wisdoms surrounding late-Quaternary extinctions of megaherbivore.  While research so far has associated the extinctions with dramatic ecosystem changes and crashes in abundance in all megaherbivores species – including those species that survived – here, we show that it is not systematically the case, by providing the counterexample of interior Alaska.

There is an increasing interest in of the late-Quaternary extinction, to understand their consequences for ecosystems function. Understanding these consequences help us guide rewilding initiatives and harness the potential of large vertebrate as ecosystem engineers in a more creative way, as explained in this article I have written for The Conversation.

Quaternary Research article abstract:

“One major challenge in the study of late-Quaternary extinctions (LQEs) is providing better estimates of past megafauna abundance. To show how megaherbivore population size varied before and after the last extinctions in interior Alaska, we use both a database of radiocarbon-dated bone remains (spanning 25-0 ka) and spores of the obligate dung fungus, Sporormiella, recovered from radiocarbon-dated lake-sediment cores (spanning 17-0 ka).

Bone fossils show that the last stage of LQEs in the region occurred at about 13 ka ago, but the number of megaherbivore bones remains high into the Holocene. Sporormiella abundance also remains high into the Holocene and does not decrease with major vegetation changes recorded by arboreal pollen percentages. At two sites, the interpretation of Sporormiella was enhanced by additional dung fungal spore types (e.g. Sordaria).

In contrast to many sites where the last stage of LQEs is marked by a sharp decline in Sporormiella abundance, in interior Alaska our results indicate the continuance of megaherbivore abundance, albeit with a major taxonomic turnover (including Mammuthus and Equus extinction) from predominantly grazing to browsing dietary guilds.

This new and robust evidence implies that regional LQEs were not systematically associated with crashes of overall megaherbivore abundance.”

The Conversation article: Late-Quaternary megafauna extinctions in interior Alaska

In an effort to make my research more accessible to a wider audience, I have just published an article in The Conversation. The aim of this piece is to explain the relevance of my latest scientific article to nature conservation and as a support for rewilding initiatives around the globe such as Rewilding Britain and Rewilding Europe.

Link for The Conversation article.

Link to original research published in the journal Quaternary Research.

 

New Paper: The effectiveness of aquatic plants as surrogates for wider biodiversity…

Law A., A. Baker, C. Sayer, G. Foster, I.D.M. Gunn, P. Taylor, Z. Pattison, J. Blaikie, N.J. Willby (2019) The effectiveness of aquatic plants as surrogates for wider biodiversity in standing fresh waters. Freshwater Biology.  https://doi.org/10.1111/fwb.13369

Article first published online: 15 July 2019

This is our first research paper based on of work conducted during my second postdoc part of the research programme Hydroscape.  We present some of the data Alan and I collected during two seasons of field work (some of it reported here, and here and here) as well as applying Structural Equation Modelling, aka SEM, a statistical methods we learned during a one-week long PR Statistics course.

Abstract below:

White water lily and pollinators in Norfolk
The diversity of aquatic plant appears to be tightly associated with invertebrate diversity: here native white water lily and pollinators in Norfolk
  1. Freshwaters are among the most globally threatened habitats and their biodiversity is declining at an unparalleled rate. In an attempt to slow this decline, multiple approaches have been used to conserve, restore or enhance waterbodies. However, evaluating their effectiveness is time‐consuming and expensive. Identifying species or assemblages across a range of ecological conditions that can provide a surrogate for wider freshwater biodiversity is therefore of significant value for conservation management and planning.
  2. For lakes and ponds in three contrasting landscapes of Britain (lowland agricultural, eastern England; upland, north‐west England; urban, central Scotland) we examined the link between macrophyte species, macrophyte morpho‐group diversity (an indicator of structural diversity) and the richness of three widespread aquatic macroinvertebrate groups (molluscs, beetles, and odonates) using structural equation modelling. We hypothesised that increased macrophyte richness and, hence, increased vegetation structural complexity, would increase macroinvertebrate richness after accounting for local and landscape conditions.
  3. We found that macrophyte richness, via macrophyte morpho‐group diversity, was an effective surrogate for mollusc, beetle, and odonate richness in ponds after accounting for variation caused by physical variables, water chemistry, and surrounding land use. However, only mollusc richness could be predicted by macrophyte morpho‐group diversity in lakes, with no significant predicted effect on beetles or odonates.
  4. Our results indicate that macrophyte morpho‐group diversity can be viewed as a suitable surrogate of macroinvertebrate biodiversity across diverse landscapes, particularly in ponds and to a lesser extent in lakes. This has important implications for the restoration, conservation, and creation of standing water habitats and for assessing their effectiveness in addressing the decline of global freshwater biodiversity. Management actions prioritising the development of species‐rich and structurally diverse macrophyte assemblages will be likely to benefit wider freshwater biodiversity.

 

New Paper: Connectivity and zebra mussel invasion offer short‐term buffering of eutrophication impacts

Salgado, J., C. D. Sayer, S. J. Brooks, T. A. Davidson, A. G. Baker, N. Willby,  I. R. Patmore, B. Goldsmith,  H. Bennion and B. Okamura (2019) Connectivity and zebra mussel invasion offer short‐term buffering of eutrophication impacts on floodplain lake landscape biodiversity. Diversity and Distribution. https://doi.org/10.1111/ddi.12938

Article first published online: 16 May 2019
Picture credits: N. Willby

New paper: Eutrophication homogenizes shallow lake macrophyte assemblages

Salgado, J., C. D. Sayer, S. J. Brooks, T. A. Davidson, B. Goldsmith, I. R. Patmore, A. G. Baker, and B. Okamura. 2018. Eutrophication homogenizes shallow lake macrophyte assemblages over space and time. Ecosphere 9(9):e02406.10.1002/ecs2.2406

Article first published online: 11 September 2018.

New paper: Agricultural origins on the Anatolian plateau

Baird, D., Fairbairn, A., Jenkins, E., Martin, L, Middleton, C., Pearson, J., Asouti, E., Edwards, Y., Kabukcu, C., Mustafaoğlu, G., Nerissa Russell, N., Bar-Yosef, O., Jacobsen, G., Wu, X, Baker, A., Elliott, S. (2018) Agricultural origins on the Anatolian plateau. Proceedings of the National Academy of Sciences (PNAS).

Article first published online: 19 March 2018.

New paper: Quantification of large herbivore populations… using dung fungal spores

Baker et al. (2016) Quantification of population sizes of large herbivores and their long-term functional role in ecosystems using dung fungal spores. Methods in Ecology and Evolution. http://dx.doi.org/10.1111/2041-210X.12580

Article first published online: 12 MAY 2016

You’ll be interested in our latest paper developing the dung fungal spore method and published in Methods in Ecology and Evolution.

With this paper and our 2013 review (see this post), my co-authors and I open the path for improved quantitative reconstruction of large herbivore population sizes. These quantitative reconstructions will be critical for any future research to contribute to topical themes such as rewilding, megafauna and ecosystem function.

Most of the research examining the relationship between large herbivores and their impact on landscapes has used extant studies. An alternative approach is to estimate the impact of variations in herbivore populations through time using fossil dung fungal spores and pollen in sedimentary sequences. The ponds at Oostvaardersplassen provided the ideal setting  to develop further the dung fungal spore method and determine the relationship between spore abundance in sediments and herbivore biomass densities. Our results indicate that this method provides a robust quantitative measure of herbivore population size over time.

The Oostvaardersplassen, The Netherlands, is a nature reserve established on polder land. Re-wilding was initiated at this site from 1983 with the introduction of free-ranging Heck cattle (Bos taurus Linnaeus) in 1983, Konik horses (Equus ferus caballus Linnaeus) in 1984 and red deer (Cervus elaphus Linnaeus) in 1992. Moreover, 1001 ponds were created throughout the reserve between 1985 and 2000 for avian biodiversity. The site is managed with a policy of minimal intervention, i.e. the population size of freely roaming large herbivores is not controlled by culling, no supplementary feeding is given during winter and no management intervention is implemented to maintain vegetation.

IMG_4755 - Copy.JPG

New paper: Phytolith analysis reveals the intensity of past land use change in the Western Ghats biodiversity hotspot.

Nogué, S., Whicher, K., Baker, A.G., Bhagwat, S.A. & Willis, K.J. (2016) Phytolith analysis reveals the intensity of past land use change in the Western Ghats biodiversity hotspot. Quaternary International.

Article first published online: 8 March 2016.