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:
- 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
- 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 »