Ambroise

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.

First records of Mentha cervina (hart’s pennyroyal) in Britain

Baker, A. 2020. Mentha cervina (Lamiaceae), an emergent aquatic alien species naturalising at South Gare, North-East Yorkshire. Vol. 2 No. 1 British & Irish Botany.

https://britishandirishbotany.org/index.php/bib/article/view/37

Published and open access since Feb 26 2020.

Abstract: There is an increasing interest in recording early colonisation of organisms when studying changes in distribution ranges induced by climate change. Here, I describe one population of Mentha cervina L. (Hart’s pennyroyal), naturalising in the wild at South Gare, v.c.62 North-east Yorkshire. Two other populations have been reported in Britain and none are known from Ireland. Of the three populations ever reported from the wild in Britain, two are still extant. It is unclear what vectors disperse M. cervina in Britain and whether the species is becoming increasingly naturalised or not. Diagnostic characters: digitate bracteoles and four calyx teeth, are provided to facilitate the recording of this mint species by field botanists.

Mentha cervina, growing in situ in South Gare

A suspected introgressive population of Ilex aquifolium and Ilex x altaclerensis, Satlburn, Yorkshire, UK

This post introduces to a well-established and complex population of self-sown Ilex x altaclerensis (Highclere holly) observed in Saltburn Valley Gardens, Yorkshire, UK.

Ilex aquifolium - Ilex x altaclerensis hybrid in Saltburn Valley Gardens — Self-sown holly with definite hybrid characteristics, including large, broad and flat leaves.

We are familiar with the native holly, Ilex aquifolium, a small tree whose spiny evergreen foliage and small red berries are associated with end-of-year festivities. Ilex x altaclerensis was born of a marriage only possible as a result of human agency, when it took the Vicorian’s fancy to grow Ilex perado (Madeira holly) in glasshouses and allowed it to cross pollinate with the native I. aquifolium accidentally growing in the wild near that greenhouse. The resulting hybrids remain popular planted hollies.

Self sown Ilex x altaclerensis (right) and Ilex aquifolium (left) growing side by side.

In most cases, when growing side by side Ilex aquifolium and Ilex x altaclerensis are relatively distinct (See picture above). However, looking more closely among trees in Saltburn Valley Garden, I also found a series of specimens with confusing morphologies suggesting a full-range gradient of intermediates between typical Ilex x altaclerensis and typical Ilex aquifolium (See picture below). This variety in the hybrid population may be a sign of introgressive hybridisation, or introgression.

A range of leaf size and shapes found in Saltburn Valley Gardens: each leaf is a representative leaf for an individual tree.

Introgression is a biological term used to describe the process leading hybrids to re-hybridise with one of their parents. Such population tend to include specimens with the full spectrum of intermediates between typical hybrid and ‘pure’ species, blurring boundary between species.

Introgression is under the spotlight in nature conservation because it is claimed to threaten the integrity of some native species. For example, there are concerns that the charismatic English bluebell could be outcompeted by garden escape hybrids (between the English bluebell and Spanish bluebell). However this threat proved unfounded in recent research, despite the potential for introgresssion.

More controversially, I would happily argue that introgression is an opportunity for native species to become more global-change adapted. For example, a species may assimilate additional genes and characteristics that will render it more resilient to environmental change over time. Following this logic, the introgressive population of hollies from Saltburn Valley Garden may represent novel biodiversity fit to face human-induced environmental change.

Such cases of introgression are interesting case studies to better understand what lays ahead. In fact introgression between natives and non-native is expected to become increasingly common with the rise of the Anthorpocene, a period of earth history where we are seeing a big reshuffle in species distribution as well as changing environmental conditions such as increase CO2 in the atmosphere, climate warming and disruption of nutrient cycles.

In the absence of DNA studies, my suspicion of intr0gression between Ilex aquifolium and Ilex x altaclerensis are based on morphological observation. In Saltburn Valley Gardens, the best vegetative identification criteria between the two taxa can be summarised with the three-choices key as follows:

Leaves flat/plane, with small forward-pointing spines more or less adpressed to leaf margin, length:width ratio <2, often dull. __________________________Ilex x altaclerensis
Leaves showing one or more of the following characteristics: irregularly undulated, mixture of forward-adpressed and other types of spines, leaves unusually large (>12cm in length), hybrid vigor in terms of yearly growth _________________________ Ilex x altaclerensis
Leaves strongly undulated (wavy margin, significantly more three-dimensional than blade thickness, forming folds when pressed flat), spines patent or backward pointing (spines nearer apex often forward pointing but not small and adpressed to leaf margin), length:width ratio >2. ____________________________Ilex aquifolium

Natives and hybrids can often show individual leaves, branches or whole trees with spineless leaves.

Guest blog by Laura Waistell: Relating habitat age to species richness

Laura writes: “I am currently entering my second year of study of Environmental Science BSc at Teesside University. During my first year, I carried out a Student as researcher position with Ambroise, which was a fantastic opportunity to develop my skills as a researcher. Below is a description of my project as presented at the Tees Valley Nature Partnership annual conference in June 2019 hosted by Teesside University’s Ecology and Environment group.”

“This project sought to determine whether there was a link between the age of freshwater habitats and the diversity of resident molluscs. Data was collected across Cumbria, Norfolk and Glasgow to analyse biodiversity while a variety of historical mapping software was used to determine the approximate age of said sites.”

[Please note that ponds and lakes of natural origin with no discernible age (those marked 0) have been removed from the data presentation as they provide no further information and could not be plotted accurately]

“Sources used were: Oldmaps.co.uk, GoogleEarth and GIS. National grid references (NGR) were used to access historical maps of the area, which were compared in a GIS to determine the appearance of the water body. The times in which the water body first appeared in historical mapping were compared to that of previous maps to determine approximate age. Man-made water bodies had specific build dates, which were found by contacting various land managers and local bodies. Any water bodies that existed without change from the oldest available maps were recorded as 0 and they were assumed to be of natural origin.”

“I found that younger ponds have a higher species richness on average. The opposite result was found for lakes as there is a apparent decrease in species richness with younger lakes. The oldest lakes show some of the highest species richness throughout the sample group, suggesting that more mature lakes yield the highest mollusc species richness.”

“There are many potential reasons for this trend in mollusc diversity in relation to age. For example, eutrophication and accumulation of sediments may be the reason for the trend in pond mollusc species richness. As sediments build up over time, there may be less available habitat.
Over time ponds may also experience encroachment from vegetation, particularly trees which may lead to eutrophication; building up over time and leading to a poorer water quality of which some mollusc species may be unable to tolerate.”

“Whereas, it may be that the lakes that have been established for a longer period have accumulated more mollusc species over time. This could be for a number of reasons such as: colonisation, establishment of plant species (food source and habitat) as well as the quality of the water and the maturity of natural water purification systems. Younger lakes may not have developed these yet and so cannot support the same number of species; particularly those more delicate and vulnerable to sudden change.”

“These data suggest that there is a correlation between the age of a water body and the species richness of molluscs. While older ponds decrease in biodiversity with age, lakes behave in an opposing manner.
The implications of this is a call for increased protection of older lakes as these harbour the highest diversity. Findings also suggest a reduction in richness with age in ponds may be down to accumulation of pollutants as well as sediments. This, too, may call for increased management to regenerate ponds, maintaining diversity.”

“Further research will be carried out on other organisms such as aquatic plants, beetles and dragonflies to determine any wider correlations.”

“Thank you to LTE for funding this research project and to Dr Ambroise Baker, Dr Alan Law and Dr Carl Sayer for help with research. Thank you also to NERC Hydroscape research project for providing biodiversity data.”

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

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.
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.
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.
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

BES2018 Thematic Session: Advancing our understanding of long-term ecology

In addition to my talk at the BES annual meeting, Althea Davies from the University of St Andrews and I had organised a session for which we invited keynote speakers on the theme: “Advancing our understanding of long-term ecology”

The Line up:

Maria Dornelas, University of St Andrews, UK: Temporal change in biodiversity change in the Anthropocene

Lizzy Jeffers, University of Oxford, UK: Plant controls on Late Quaternary whole ecosystem structure and function

Will Gosling, University of Amsterdam, Netherlands: Advancing palaeo-fire ecology

Helen Bennion, University College London, UK: Assessing the potential for aquatic plant recolonisation after local extirpation

Alistair Seddon, University of Bergen, Norway: Assessing ecological resilience using long-term ecological data: perspectives and prospects

Sandra Nogué, University of Southampton, UK: Comparative ecology of the Laurel forest pollen rain from Tenerife and La Gomera

Jack Williams, University of Wisconsin-Madison, USA: Ecological and Environmental Novelty

Pollen production review (in prep.) presented at the British Ecological Society Annual Meeting 2018

I was so excited when I received an email from the British Ecological Society (BES) saying that the abstract submitted with Sandra Nogue (University of Southampton) had been accepted for an oral presentation at the 2018 BES Annual Meeting!

And here I am presenting our review paper in preparation – thank you Sandra for taking this picture and many thanks also to the PollerGEN project for providing the illustration for the slide captured here.

Abstract: Modification of pollen production in response to global change: a review

How pollen abundance and quality impacts human–environment system is a significant focal point in: i) public health, with pollen-born allergies and asthma, ii) ecosystem services with crop pollination and nutrient cycling in nutrient-poor wetlands iii) global change ecology and conservation with reproductive limitation and vegetation regeneration. Atmospheric dispersal and pollinators are key dispersal mechanism currently investigated to quantify and forecast pollen impacts. However, pollen production by plants from natural, semi-natural and urban vegetation can be extremely sensitive to environmental conditions, while being at the same time the ultimate driver of these pollen impacts. Despite this crucial role, it is currently un-clear how pollen production will be modified by global change in the future. As a result, longer-term forecast of pollen impact may be associated with extremely large uncertainty.

As a first step towards addressing this key knowledge gap, we reviewed the environmental factors governing pollen production, in terms of pollen quantity and quality. We focussed on factors directly modifying pollen production, given existing vegetation cover and composition; and therefore excluded factors such as habitat loss. Studies tended to focus on the response of a single, or a small set of species, to a single factor. There appears to be a dearth of research studying pollen response at the vegetation plot or ecosystem level. The principal factors driving pollen production in the species studied were nutrient enrichment, increased atmospheric CO2 levels, changes in UV levels, and climatic factors modifying water availability, seasonality and temperatures. Other factors, including biological interaction such as grazing were extremely under-researched. The studied factors often had effects in opposite directions but the outcome of interaction between factors was rarely quantified. In addition, we found a body of literature that concerned flowering response. However, there was only limited quantitative data linking flowering response to pollen production.

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.