Heat tolerance highly variable among populations and species

14 01 2020

Many ecological studies have examined the tolerance of terrestrial wildlife to high and low air temperatures over global scales (e.g., 1, 2, 3). This topic has been boosted in the last two decades by ongoing and predicted impacts of climate change on biodiversity (see summary of 2019 United Nation’s report here and here).

However, it is unfortunate that for most species, studies have measured thermal tolerance from a single location or population. Researchers interested in global patterns of thermal stress collect those measurements from the literature for hundreds to thousands of species [recently compiled in the GlobTherm database] (4), and are therefore often restricted to analysing one value of thermal tolerance per species.


Three of the 15 species of Iberian lacertids sampled in our study of thermal tolerance (9), including the populations of Algerian psammodromus (Psammodromus algirus), Geniez’s wall lizard (Podarcis virescens) and Western green lizard (Lacerta bilineata) sampled in Navacerrada (Madrid), Fuertescusa (Cuenca) and Moncayo (Soria), respectively. Photos by S. Herrando-Pérez

Using this approach, ecologists have concluded that cold tolerance is far more variable than heat tolerance across species from the tropics to the boreal zone (5-8). Consequently, tolerance to heat stress might be a species trait with limited potential to change in response to global warming compared to cold tolerance (5). Read the rest of this entry »

Offshore Energy & Marine Spatial Planning

22 02 2018


I have the pleasure (and relief) of announcing a new book that’s nearly ready to buy, and I think many readers of CB.com might be interested in what it describes. I know it might be a bit premature to announce it, but given that we’ve just finished the last few details (e.g., and index) and the book is ready to pre-order online, I don’t think it’s too precocious to advertise now.


A little history is in order. The brilliant and hard-working Katherine Yates (now at the University of Salford in Manchester, UK) approached me back in 2014 to assist her with co-editing the volume that she wanted to propose for the Routledge Earthscan Ocean series. I admit that I reluctantly agreed at the time, knowing full well what was in store (anyone who has already edited a book will know what I mean). Being an active researcher in energy and biodiversity (perhaps not so much on the ‘planning’ side per se) certainly helped in my decision.

And yes, there were ups and downs, and sometimes it was a helluva lot of work, but Katherine certainly made my life easier, and she has finally driven the whole thing to completion. She deserves most of the credit.

Read the rest of this entry »

Tiny, symbiotic organisms protect corals from predation and disease

20 12 2017
hydrozoan polyp

Hydrozoan polyps living on the surface of a coral (photo credit: S. Montano)

Corals could have some unexpected allies to cope with the multi-faceted threats posed by climate change.

In a new study published today in Proceedings of the Royal Society B, Montano and colleagues show how tiny hydrozoans smaller than 1 mm and commonly found in dense colonies on the surface of hard corals (see above photo) play an important ecological role.

Visually examining ~ 2500 coral colonies in both Maldivian and Saudi Arabian reefs, the scientists searched for signs of predation, temperature-induced stress, and disease. For each colony, they also recorded the presence of symbiotic hydrozoans. They demonstrated that corals living in association with hydrozoans are much less prone to be eaten by corallivorous (i.e., ‘coral-eating’) fish and gastropods than hydrozoan-free corals.

A likely explanation for this pattern could be the deterring action of hydrozoan nematocysts (cells capable of ejecting a venomous organelle, which are the same kinds found in jellyfish tentacles). An individual hydrozoan polyp of less than 1 mm clearly cannot cope with a corallivorous fish that is a billions of times larger, yet hydrozoans can grow at high densities on the surface of corals (sometimes > 50 individuals per cm2). This creates a sort of a continuous, ‘urticating‘ carpet that can discourage fish from foraging. Read the rest of this entry »

Rich and stable communities most vulnerable to change

16 08 2016

networkI’ve just read an interesting new study that was sent to me by the lead author, Giovanni Strona. Published the other day in Nature Communications, Strona & Lafferty’s article entitled Environmental change makes robust ecological networks fragile describes how ecological communities (≈ networks) become more susceptible to rapid environmental changes depending on how long they’ve had to evolve and develop under stable conditions.

Using the Avida Digital Evolution Platform (a free, open-source scientific software platform for doing virtual experiments with self-replicating and evolving computer programs), they programmed evolving host-parasite pairs in a virtual community to examine how co-extinction rate (i.e., extinctions arising in dependent species — in this case, parasites living off of hosts) varied as a function of the complexity of the interactions between species.

Starting from a single ancestor digital organism, the authors let evolve several artificial life communities for hundred thousands generation under different, stable environmental settings. Such communities included both free-living digital organisms and ‘parasite’ programs capable of stealing their hosts’ memory. Throughout generations, both hosts and parasites diversified, and their interactions became more complex. Read the rest of this entry »

Influential conservation papers of 2015

25 12 2015

most popularAs I did last year and the year before, here’s another arbitrary, retrospective list of the top 20 influential conservation papers of 2015 as assessed via F1000 Prime.

Read the rest of this entry »

It’s all about the variation, stupid

12 01 2015

val-1-3It is one of my long-suffering ecological quests to demonstrate to the buffoons in government and industry that you can’t simply offset deforestation by planting another forest elsewhere. While it sounds attractive, like carbon offsetting or even water neutrality, you can’t recreate a perfectly functioning, resilient native forest no matter how hard you try.

I’m not for a moment suggesting that we shouldn’t reforest much of what we’ve already cut down over the last few centuries; reforestation is an essential element of any semblance of meaningful terrestrial ecological restoration. Indeed, without a major commitment to reforestation worldwide, the extinction crisis will continue to spiral out of control.

What I am concerned about, however, is that administrators continue to push for so-called ‘biodiversity offsets’ – clearing a forest patch here for some such development, while reforesting or even afforesting another degraded patch there. However, I’ve blogged before about studies, including some of my own, showing that one simply cannot replace primary forests in terms of biodiversity and long-term carbon storage. Now we can add resilience to that list.

While I came across this paper a while ago, I’ve only found the time to blog about it now. Published in PLoS One in early December, the paper Does forest continuity enhance the resilience of trees to environmental change?1 by von Oheimb and colleagues shows clearly that German oak forests that had been untouched for over 100 years were more resilient to climate variation than forests planted since that time. I’ll let that little fact sink in for a moment … Read the rest of this entry »

Influential conservation papers of 2014

22 12 2014

splash2Another year, another arbitrary retrospective list – but I’m still going to do it. Based on the popularity of last year’s retrospective list of influential conservation papers as assessed through F1000 Prime, here are 20 conservation papers published in 2014 that impressed the Faculty members.

Once again for copyright reasons, I can’t give the whole text but I’ve given the links to the F1000 assessments (if you’re a subscriber) and of course, to the papers themselves. I did not order these based on any particular criterion.

Read the rest of this entry »

High-altitude ecology

28 08 2014
A constant hazard in the Tibetan Plateau - yakjam

A constant hazard in the Tibetan Plateau – yakjam

I’ve been out of the social-media loop for a few weeks, hence the abnormally long interval since my last post. As you might recall, I’ve been travelling overseas and most recently blogged from Monterey, California where I was attending a symposium on invasion genetics.

The next phase of my travels couldn’t have been more different.

The reason I couldn’t access the blog was because I was well behind the Great Firewall of China. I was, in fact, in the Tibetan region of Gansu and Sichuan Provinces in western China for most of the last 10 days. While I’ve travelled to China many times before, this was by far the most evocative, interesting and unique experience I’ve ever had in this country. Reflecting on the past 10 days while waiting in Hong Kong for my flight back to Australia, I am still reeling a little from what I saw.

Top bloke: Jiajia Liu of Fudan University

Top bloke: Jiajia Liu of Fudan University

What the hell was I doing at 3500-4000 m elevation on the Tibetan Plateau? Good question. I have been most fortunate to be included in a crack team of Chinese ecologists who have designed and implemented a most impressive set of experiments in plant community ecology. The team, led by Professor Shurong Zhou and Dr. Jiajia Lui of Fudan University, has been working relentlessly to put together some of the sexiest plant ecology experiments going in China.

Having now so far published two papers from the some of the experiments (see here and here), my Chinese colleagues thought it was high time I visited the famous site. Situated at 3500 m in the Tibetan region of Gansu Province in western China, the Lanzhou University research station Azi Shi Yan Zhan is about a 20-hectare area of meadow fenced off from the grazing of the ubiquitous domestic yaks herded by the local Tibetans. If that sounds pretty exotic, let me assure you that it is. Read the rest of this entry »

Tropical forest resilience depends on past disturbance frequency

16 07 2014

I’ve recently come across an interesting study that perfectly marries palaeo-ecological data with modern conservation philosophy. It’s not often that such a prehistorical perspective dating at least to the Last Glacial Maximum has been used so effectively to inform future conservation outlooks. I’m particularly interested in this sort of approach considering my own palaeo dabblings of late.

Published in Nature Communications this May, Lydia Cole and colleagues’ paper Recovery and resilience of tropical forests after disturbance is a meta-analysis of 71 studies covering nearly 300 disturbance events in tropical forests over the last 20,000 years or so. Using fossil pollen records as an index of vegetation change, they demonstrated the (somewhat intuitive) main result that the time to recovery following a disturbance generally decreases as the past disturbance frequency increased.

This appears to be a vindication of the idea that a system’s adaptive strategies evolve as a product of the local disturbance regime. More importantly, they found that recovery was faster following ‘large infrequent events’, which are natural perturbations such as cyclones and major fires. While most past disturbances were caused by humans clearing forest, the fact that tropical forest systems were most resilient to ‘natural’ events means that if we can’t stop human disturbances, at least we can attempt to emulate natural processes to maximise the rebound potential. Much like many modern forestry operations try to emulate natural disturbances to limit their damage, we should at least manage our impacts by understanding so-called ‘natural’ regimes as much as possible. Read the rest of this entry »

More species = more resilience

8 01 2014

reef fishWhile still ostensibly ‘on leave’ (side note: Does any scientist really ever take a proper holiday? Perhaps a subject for a future blog post), I cannot resist the temptation to blog about our lab’s latest paper that just came online today. In particular, I am particularly proud of Dr Camille Mellin, lead author of the study and all-round kick-arse quantitative ecologist, who has outdone herself on this one.

Today’s subject is one I’ve touched on before, but to my knowledge, the relationship between ‘diversity’ (simply put, ‘more species’) and ecosystem resilience (i.e., resisting extinction) has never been demonstrated so elegantly. Not only is the study elegant (admission: I am a co-author and therefore my opinion is likely to be biased toward the positive), it demonstrates the biodiversity-stability hypothesis in a natural setting (not experimental) over a range of thousands of kilometres. Finally, there’s an interesting little twist at the end demonstrating yet again that ecology is more complex than rocket science.

Despite a legacy of debate, the so-called diversity-stability hypothesis is now a widely used rule of thumb, and its even implicit in most conservation planning tools (i.e., set aside areas with more species because we assume more is better). Why should ‘more’ be ‘better’? Well, when a lot of species are interacting and competing in an ecosystem, the ‘average’ interactions that any one species experiences are likely to be weaker than in a simpler, less diverse system. When there are a lot of different niches occupied by different species, we also expect different responses to environmental fluctuations among the community, meaning that some species inherently do better than others depending on the specific disturbance. Species-rich systems also tend to have more of what we call ‘functional redundancy‘, meaning that if one species providing an essential ecosystem function (e.g., like predation) goes extinct, there’s another, similar species ready to take its place. Read the rest of this entry »

Essential predators

21 11 2012

© C. Hilton

Here at ConservationBytes.com, My contributors and I have highlighted the important regulating role of predators in myriad systems. We have written extensively on the mesopredator release concept applied to dingos, sharks and coyotes, but we haven’t really expanded on the broader role of predators in more complex systems.

This week comes an elegant experimental study (and how I love good experimental evidence of complex ecological processes and how they affect population persistence and ecosystem stability, resilience and productivity) demonstrating, once again, just how important predators are for healthy ecosystems. Long story short – if your predators are not doing well, chances are the rest of the ecosystem is performing poorly.

Today’s latest evidence comes from on an inshore marine system in Ireland involving crabs (Carcinus maenas), whelks (Nucella lapillus), gastropd grazers (Patella vulgata, Littorina littorea and Gibbula umbilicalis), mussels (Mytilus edulis) and macroalgae. Published in Journal of Animal Ecology, O’Connor and colleagues’ paper (Distinguishing between direct and indirect effects of predators in complex ecosystems) explains how their controlled experimental removals of different combinations of predators (crabs & whelks) and their herbivore prey (mussels & gastropods) affected primary producer (macroalgae) diversity and cover (see Figure below and caption from O’Connor et al.). Read the rest of this entry »

Different is better

6 03 2012

I found a nice complement to my More is Better post from January where I reported the results of a new meta-analysis demonstrating how higher species evenness and diversity engendered greater forest productivity – great empirical evidence for the so-called diversity-productivity relationship.

The latest paper adding convincing evidence regarding the important role of species diversity in maintaining ecosystem function comes from Marc Cadotte and colleagues published online early in Ecology. The paper, Phylogenetic diversity promotes ecosystem stability, looks at the problem from a slightly different angle.

If you recall from Zhang and colleagues, forest plots composed of many different species were more productive than single-species stands, and more ‘even’ (i.e., a metric which includes relative abundance of each species in system) stands were more productive, and better at explaining the variance in productivity than species richness alone.

Of course, species richness is considered only a blunt instrument to measure ‘biodiversity’, with evenness providing only a slight improvement. Ideally, we should be talking about genetic diversity considering this is the fundamental unit on which most of evolutionary processes operate (i.e., genes and gene complexes).

So Cadotte and colleagues measured genetic diversity within experimental plots of grassland savanna species established in Minnesota, USA (i.e., consisting of C3 grasses, C4 grasses, legumes, non-legume herbaceous forbs and two woody species) and compared this to ecosystem ‘stability’ (i.e., above-ground biomass divided by inter-annual standard deviation). They measured genetic diversity using four different metrics:

  1. the sum of the phylogenetic branch lengths represented by a set of co-occurring species
  2. the mean nearest taxon distance = the average of the shortest phylogenetic distance for each species to its closest relative
  3. the mean pairwise distance = the average of all phylogenetic distances connecting species in the sample; and
  4. an entropic measure based on the relative distribution of evolutionary distinctiveness, measured as the amount of a species’ evolutionary history that is not shared with other species Read the rest of this entry »

More is better

18 01 2012

In one of those rare moments of perusing the latest ecological literature, I stumbled across an absolute gem, and one that has huge conservation implications. Now, I’m really no expert in this particular area of ecology, but I dare say the paper I’m about to introduce should have been published in Nature or Science (I suspect it was submitted to at least one of these journals first). It was still published in an extremely high-impact journal in ecology though – the Journal of Ecology produced by the British Ecological Society (and one in which I too have had the honour of publishing an article).

Before I get into specifics, I have to say that one thing we conservation biologists tend to bang on about is that MORE SPECIES = BETTER, regardless of the ecosystem in question. We tend to value species richness as the gold standard of ecosystem ‘health’ and ‘resilience’, whether or not there is strong empirical evidence in support. It’s as if the more-is-better mantra strikes an intuitive chord and must, by all that’s ecologically right in the world, be true.

Of course, measuring what is ‘better’ is a difficult task, especially when we are talking about complex ecosystems comprising thousands, if not millions, of species. Does ‘better’ refer to the most temporally stable, the most genetically diverse, the most resilient to perturbation, or the provider of the greatest number of functions and hence, ecosystem services?

It’s up to you, but all these things tend to be difficult to measure for a large number of species and over time scales of sufficient duration to measure change. So the default for plants (i.e., the structural framework of almost all ecosystems) I guess has come down to a simpler measure of success – ‘productivity’. This essentially means how much biomass is produced per unit area/volume per time step. It’s not a great metric, but it’s probably one of the more readily quantifiable indices.

Enter the so-called ‘diversity-productivity relationship’, or ‘DPR’, which predicts that higher plant species diversity should engender higher net productivity (otherwise known as the ‘net biodiversity effect’). Read the rest of this entry »