What we know we don’t know about animal tolerances to high temperatures

30 01 2023

Each organism has a limit of tolerance to cold and hot temperatures. So, the closer it lives to those limits, the higher the chances of experiencing thermal stress and potentially dying. In our recent paper, we revise gaps in the knowledge of tolerance to high temperatures in cold-blooded animals (ectotherms), a diverse group mostly including amphibians and reptiles (> 16,000 species), fish (> 34,000 species), and invertebrates (> 1,200,000 species).

As a scientist, little is more self-realising than to write and publish a conceptual paper that frames the findings of your own previous applied-research papers. This is the case with an opinion piece we have just published in Basic and Applied Ecology1 — 10 years, 4 research papers2-5 [see related blog posts here, here, here and here], and 1 popular-science article6 after I joined the Department of Biogeography and Global Change (Spanish National Research Council) to study the thermal physiology of Iberian lizards under the supervision of Miguel Araújo and David Vieites.

Iberian lizards for which heat tolerance is known (varying from 40 to 45 °C)
[left, top to bottom] Iberian emerald lizard (Lacerta schreiberi, from Alameda del Valle/Madrid) and Geniez’s wall lizard (Podarcis virescens, Fuertescusa/Cuenca), and [right, top to bottom] Algerian sand racer (Psammodromus algirus, Navacerrada/Madrid), Andalusian wall lizard (Podarcis vaucheri, La Barrosa/Cádiz), Valverde’s lizard (Algyroides marchi, Riópar/Albacete), and Cyren’s rock lizard (Iberolacerta cyreni, Valdesquí/Madrid). Heat-tolerance data deposited here and used to evaluate instraspecific variation of heat tolerance3,4. Photos: Salvador Herrando-Pérez.

In our new paper, we examine how much we know and what areas of research require further development to advance our understanding of how and why the tolerance of ectotherm fauna to high environmental temperature (‘heat tolerance’ hereafter) varies within and across the Earth’s biomes. We focus on data gaps using the global database GlobTherm as a reference template (see Box 1 below).

Our three main tenets

1. Population versus species data: Most large-scale ecophysiological research is based on modelling one measurement of heat tolerance per species (typically representing one population and/or physiological assay) over hundreds to thousands of species covering broad geographical, phylogenetic, and climatic gradients.

But there is ample evidence that heat tolerance changes a lot among populations occupying different areas of the distribution of a species, and such variation must be taken into account to improve our predictions of how species might respond to environmental change and face extinction.

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Tenure-Track Professorship in Conservation and Development

26 01 2023

The Faculty for Mathematics and Natural Sciences of Humboldt-Universität zu Berlin (HU Berlin), Geography Department, has an open position for a tenure-track professorship in Conservation and Development.

Starting as soon as possible. This is a Junior Professorship (W1 level, 100%) with a tenure track to a permanent professorship (W2 level, 100%). To verify whether the individual performance meets the requirements for permanent employment, an evaluation process will be opened not later than four years of the Junior Professorship. Tenure track professors at the HU Berlin are expected to do research and teaching, as well as to be active in university administration, in the promotion of young scientists, and in acquiring leadership and management skills. The concrete requirements out of the framework catalogue will be specified in the course of the appointment process.

We seek candidates with an outstanding research record in biodiversity conservation and sustainable development, with experience in working in the Global South. Successful candidates are rooted in conservation science and must have a doctoral degree in conservation science, development geography, environmental science, political ecology or related fields. We expect a demonstrated ability to work interdisciplinary, across the social and natural sciences to understand conservation challenges and and develop solutions.

We seek individuals with the vision, leadership and enthusiasm to build an internationally recognised research program. We expect collaboration with other research groups at the department, at HU Berlin and beyond, and a commitment to promoting a positive, diverse, and inclusive institutional culture. Experience in translating conservation science into action and/or work at the science/policy interface are beneficial.

We offer a tenure-track position in an international, young and vibrant department with an excellent scientific and education track record. The successful candidate will join an interdisciplinary group of faculty focused on human-environment relations, global change, and sustainability.

The salary will be according to W1 level, and after successful tenure evaluation W2 level. Employment at HU Berlin offers all benefits of the German public service system, including health insurance, an attractive pension plan, and social benefits.

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Interrupted flows in the Murray River endanger frogs

17 01 2023

Flooding in the Murray-Darling Basin is creating ideal breeding conditions for many native species that have evolved to take advantage of temporary flood conditions. Led by PhD candidate Rupert Mathwin, our team developed virtual models of the Murray River to reveal a crucial link between natural flooding and the extinction risk of endangered southern bell frogs (Litoria raniformis; also known as growling grass frogs).

Southern bell frogs are one of Australia’s 100 Priority Threatened Species. This endangered frog breeds during spring and summer when water levels increase in their wetlands. However, the natural flooding patterns in Australia’s largest river system have been negatively impacted by expansive river regulation that some years, sees up to 60% of river water extracted for human use.

Our latest paper describes how we built computer simulations of Murray-Darling Basin wetlands filled with simulated southern bell frogs. By changing the simulation from natural to regulated conditions, we showed that modern conditions dramatically increase the extinction risk of these beloved frogs.

The data clearly indicate that successive dry years raise the probability of local extinction, and these effects are strongest in smaller wetlands. Larger wetlands and those with more frequent inundation are less prone to these effects, although they are not immune to them entirely. The models present a warning — we have greatly modified the way the river behaves, and the modern river cannot support the long-term survival of southern bell frogs.’

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Influential conservation papers of 2022

3 01 2023

Following my annual tradition, I present the retrospective list of the ‘top’ 20 influential papers of 2022 as assessed by experts in Faculty Opinions (formerly known as F1000). These are in no particular order. See previous years’ lists here: 2021, 2020, 201920182017201620152014, and 2013.

Genetic variance in fitness indicates rapid contemporary adaptive evolution in wild animals — “… this paper adds a much-needed perspective to the status of genetic diversity and adaptive potential in contemporary populations.

Habitat, geophysical, and eco-social connectivity: benefits of resilient socio-ecological landscapes — “… distinguishes four distinct but interrelated types of connectivity: landscape, habitat, geophysical, and eco-social connectivity, of which the fourth type is new. The authors discuss how these different types of connectivity are related to ecosystem services and disservices, and how they interact with each other to influence landscape sustainability issues.

Glyphosate impairs collective thermoregulation in bumblebees — “… low-dose glyphosate, combined with global increases in temperature, converge to disrupt homeostatic regulation in bee colonies. This is a crucial revelation for understanding the loss of bees across the globe, as they serve as major pollinators in nature and agriculture.

Human disturbances affect the topology of food webs — “… provides great opportunities for the study of food web structures, their dynamics and stability under different human influences.

A comprehensive database of amphibian heat tolerance — “provides estimates of amphibian upper thermal limits – a relevant trait for assessing the vulnerability of this highly-threatened group of ectotherms to rising temperatures – derived from thousands of experimental studies.”

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