Management-driven evolution in a domesticated ecosystem

Abstract

Millennia of human land-use have resulted in the widespread occurrence of what have been coined 'domesticated ecosystems'. The anthropogenic imprints on diversity, composition, structure and functioning of such systems are well documented. However, evolutionary consequences of human activities in these ecosystems are enigmatic. Calluna vulgaris (L.) is a keystone species of coastal heathlands in northwest Europe, an ancient semi-natural landscape of considerable conservation interest. Like many species from naturally fire-prone ecosystems, Calluna shows smoke-adapted germination, but it is unclear whether this trait arose prior to the development of these semi-natural landscapes or is an evolutionary response to the anthropogenic fire regime. We show that smoke-induced germination in Calluna is found in populations from traditionally burnt coastal heathlands but is lacking in naturally occurring populations from other habitats with infrequent natural fires. Our study thus demonstrates evolutionary imprints of human land-use in semi-natural ecosystems. Evolutionary consequences of historic anthropogenic impacts on wildlife have been understudied, but understanding these consequences is necessary for informed conservation and ecosystem management.

Keywords: coastal heathland; cultural landscape; fire; germination cues; smoke-induced germination.

Figure 1.

Fire frequencies, study sites and distribution of anthropogenic coastal heathlands (purple shade) in Norway. Purple arrows indicate sites with frequent fires documented back to the Late Bronze or Iron Age (selected from 70 palaeoecological records [,,–15]). White arrows indicate boreal heaths or forests with low-frequency natural fire regimes, with years since last fire given next to each arrow (from [–25]). Black circles and white squares indicate seed-sampling sites along the latitudinal and elevational gradient, respectively. Inset shows a microfossil record from site B over the past 6000 years (reprinted with permission from [17]). See the electronic supplementary material, table S1 for site information. (Online version in colour.)

Figure 2.

Calluna vulgaris germination probabilities over time in response to smoke treatment along the latitudinal and elevational gradients. Lines give model predictions (posterior distributions from GLMM) and shaded areas delimit 2.5–97.5 percentile credibility of smoke-treated (red) and control (black) samples. m.a.s.l., metres above sea level.