Less snow from climate change pushes evolution of browner birds

7 09 2017
© Bill Doherty

© Bill Doherty

Climate changes exert selective pressures on the reproduction and survival of species. A study of tawny owls from Finland finds that the proportion of two colour morphs varies in response to the gradual decline of snowfall occurring in the boreal region.

Someone born in the tropics who travels to the Antarctic or the Himalaya can, of course, stand the cold (with a little engineering help from clothing, however). The physiology of our body is flexible enough to tolerate temperatures alien to those of our home. We can acclimate and, if we are healthy, we can virtually reside anywhere in the world.

However, modern climate change is steadily altering the thermal conditions of the native habitats of many species. Like us, some can live up to as much heat or cold as their genetic heritage permits, because each species can express a range of morphological, physiological, and behavioural variation (plasticity). Others can modify their genetic make-up, giving way to novel species-specific features or genotypes (evolution).

When genetic changes are speedy, that is, within a few generations, we are witnessing ‘microevolution’ — in contrast to ‘macroevolution’ across geological time scales as originally reported by Darwin and Wallace (1). To date, the detection of microevolution in response to modern climate change remains elusive, and many studies claiming so seem to lack the appropriate data to differentiate microevolution from phenotypic plasticity (i.e., the capacity of a single genotype to exhibit variable phenotypes in different environments) (2, 3). Read the rest of this entry »

Cartoon guide to biodiversity loss XXXIII

18 11 2015

Six more biodiversity cartoons to hold you over until I get back from Germany next week (see full stock of previous ‘Cartoon guide to biodiversity loss’ compendia here).

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Cartoon guide to biodiversity loss XXV

8 09 2014

Here are 6 more biodiversity cartoons for your conservation-humour fix (see full stock of previous ‘Cartoon guide to biodiversity loss’ compendia here).

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World Heritage Species

17 08 2014

horseshoe crabHaving just attended the Baker & Stebbins Legacy Symposium on Invasion Genetics in Pacific Grove, California, I have had a rare bit of leisure time between my book-writing commitments and operating in conference mode. It’s summer here in California, so I’ve taken the opportunity to read a bit of The New Yorker in my accommodation. It is indeed a pleasure to have these micro-moments of ‘leisure’ reading. As it turns out though, work subjects are never far from my mind as I do this.

So it interested me greatly when I read another fantastic article in the ‘Yorker about horseshoe crabs, and their precarious state despite having survived half a billion years on this planet. While I was generally interested in the science, biomedical applications, conservation and systematics of the species, what really caught my eye was the proposal to list them as a ‘World Heritage Species’.

A what? Never heard of that classification, you say? Neither had I. Not to worry though – it doesn’t exist yet. Read the rest of this entry »

Cartoon guide to biodiversity loss XXIV

17 06 2014

Another 6 biodiversity cartoons for your conservation giggle & groan (see full stock of previous ‘Cartoon guide to biodiversity loss’ compendia here).

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All that glitters is not gold – ecological traps

27 09 2011

Another corker from Salvador Herrando-Pérez:

Cinema fans know that choosing a movie by the newspaper’s commentary or the promotional poster might be a lottery. In the movie of nature, to confuse ‘the attractive’ with ‘the appropriate’ can compromise the life of an individual and its offspring, even to the extent of anticipating the extinction of an entire population or species.

Animals make daily choices about when, where or with whom to engage in basic activities like eating, hibernating, mating, migrating or resting. Those choices are often strongly tied to highly specific cues – e.g., air temperature, tree density, location of water, or smell of other individuals. And it happens to hair lice jumping from head to head among school kids, or to caribou forming their winter herds prior to the seasonal migration. All species, without exception, persist in nature because those ‘choices’ translate into survival or successful reproduction more often than do not. They are a kind of evolutionary memory imprinted in an organism’s genes and behaviour. However, sometimes the right choice (‘right’ meaning perceiving a cue for the role it actually has in the life cycle) places an individual in the worst of all possible situations. The environment cheats, ‘the attractive’ merely mimics ‘the appropriate’, and the individual fails to reproduce, starves, sickens, or even dies.

Figure 1. Water reservoirs tainted with fuel (see dark contours) in Kuwait following the Gulf War in the early 1990s. Overlaid pictures show the silhouettes of trapped odonates (right), vertebrates (top left) and invertebrates (bottom left) (Photos courtesy of Jochen Zeil).

At the mercy of mirages

During the Gulf War, the destruction of infrastructure for crude exploitation spilled large amounts of fuel in many water reservoirs over the desert landscape of Kuwait. A little later, Horváth and Zeil1 found agglomerations of dead insects (and a range of vertebrates) along the shores of these polluted reservoirs, and observed dragonflies drowning in their kamikaze attempt to spawn on the oily surface (Figure 1). This work stimulated further research whereby Horváth and his team in Budapest showed that odonates are attracted by light polarization at the surface of oiled water2 – hence ‘polarized light pollution’3. Not only that, they recorded insects struggling to spawn on or mate with riveting surfaces such as solar panels, asphalted roads, plastic bags or (creepy enough!) cemetery crypts4. It goes without saying: these insects are victims of a mirage.

Those habitats or features of the habitat that mislead an animal’s choice, often hampering the completion of its life cycle, are known as ‘ecological traps’ – in other words, the environmental cue is decoupled from the quality of the habitat it is meant to signal. Ecological traps were first described in the 1970s by Dwernychuk and Boag5. They found that ducks on the islands of Miquelon lake located their nests among those of seagulls despite the latter happily devoured their ducklings and eggs. When these islands emerged in the middle of last century, they were first colonized by common terns (Sterna hirundo). By defending their own nests ferociously from predators (mainly crows and magpies), the terns inadvertently shielded the nests of their ducky comrades. The Canadians hypothesized that when seagulls subsequently replace terns, the ducks continued to sense their new neighbours as a (now misleading) sign of protection. Read the rest of this entry »

Evolution here and now

17 02 2011

Here’s a guest post from one of my PhD students, Salvador Herrando-Peréz. Salva is working on theoretical aspects of density feedback mechanisms among different species, and is especially eclectic with his interests in biology. Salva regularly contributes to lay natural history magazines, especially in his native tongue Castellano (Spanish), and he is an active member of the Spanish organisation Bioestudios Saganta, a non-profit national organisation fully devoted to scientific research and its popularisation with a focus on biodiversity conservation.

I’ve asked my students to start contributing to ConservationBytes.com, and Salva is leading the charge.

Evolution evokes ideas such as fossils, geological eras and time scales of hundreds of thousands to millions of years. Only recently have we started to appreciate that such ‘macro-evolution’ is the result of accumulated changes in the morphology and genes of species from one generation to the next: days for HIV strands, months for a planktonic rotifer, or years for a poplar.

The Britons Peter and Rose Mary Grant published in 2002 a 30-year study on Darwin’s finches from Daphne Major (Galapagos, Ecuador) – a popular study organism since Charles Darwin’s Origin of species (Grant & Grant 2002). In such a short period of time, covering only six generations of these granivorous birds, several extreme droughts altered the type and abundance of seeds, and potentially triggered the evolution of body size, and beak shape and size, up to three times (Figure 1). The two biologists from Princeton reveal that:

  1. evolution is reversible – generations of finches experiencing overall increase in body and beak sizes can lead to future generations with smaller sizes (of course within limits; a finch will never develop the beak of a stork or a hummingbird), and
  2. phenological shifts across generations are unpredictable in so far as they respond to random climatic fluctuations – should droughts of contrasting intensity have occurred in different years over the study period, beaks and bodies might have evolved in other particular fashions. Read the rest of this entry »