How do ecological and evolutionary processes influence the distribution of species?

Multiple processes, such as dispersal limitation, population or evolutionary dynamics, interact to determine species range margins. Understanding the processes constraining species range margins thus underpins our ability to predict responses to climate change. For this, I use observational and experimental approaches along environmental gradients, which represent a space-for-time analogue of future climate conditions. For example elevational and latitudinal gradients provide ideal model systems to study species range limits, because they cover a similar range of climatic conditions, particularly of temperature, but differ greatly in other factors such as spatial scale (Figure 1a).

In a field survey we found that species reach lower temperature limits along the elevational compared to the latitudinal gradient (Figure 1b, Halbritter et al. 2013). Different explanations could be responsible for this pattern and we performed a reciprocal transplant experiment to investigate local adaptation in populations of 2 Plantago species from central locations in their European range and from their latitudinal and elevational range edges (in northern Scandinavia and Swiss Alps, respectively). Range-centre plants of P. major were adapted to conditions at the range centre, but performed similarly to range-edge plants when grown at the range edges. There was no evidence for local adaptation when comparing central and edge populations of P. lanceolata. However, plants of both species from high elevation were locally adapted when compared with plants from high latitude, although the reverse was not true (Halbritter et al. 2015).


Figure 1: (a) Conceptual figure of thedifference in steepness along elevational and latitudinal gradient, which has important implications for ecological and genetic processes affecting range margins, including dispersal and local adaptation. For example, gene flow is expected to be higher along the elevational gradient, which might have contrasting consequences for adaptation at these range margins. (b) Comparison of minimal growing degree days (GDD) along the elevational (minimal GDD elev) and latitudinal (minimal GDD lat) gradients for species that occurred at least five times along each gradient. The dashed line shows the line of equality (y = x). The black solid line shows the major axis (MA) regression line for all 155 species including the confidence interval (grey lines).

How do plant communities respond to current climate change?

Species responses to climate change include among others shifts in phenology. The predicted changes in temperature and precipitation are especially important at high elevation, because they strongly affect date of snowmelt, which is closely linked to phenology. So far, the effects of multiple drivers such as temperature and precipitation have rarely been included. The aim of this project is to study changes in phenology in alpine plant communities exposed to higher summer temperature and annual precipitation and more specifically to assess to what extent these differences are plastic or genetically determined.


Figure 2: Transplant experiment along the climate grid.

This project will exploit the infrastructure of the SEEDCLIM project (Figure 2), which was initiated in 2009 in southwestern Norway to understand the effects of climate change on plants. Twelve experimental sites were established, along a climate grid combining four levels of annual precipitation (600, 1200, 2000 and 2700 mm) with three levels of mean summer temperatures (7.5, 9.5 and 11.5 °C). Vegetation turfs were transplanted to warmer, wetter sites and the combination of both along these gradients to study effects on the plant community. More recently a new project has started to study the role of Functional group interactions in mediating climate change impacts on the Carbon dynamics and Biodiversity of alpine ecosystems (FunCaB).


Figure 3: First flowering in days of the year in control and transplanted turf. The turfs have been transplanted to warmer, wetter and warmer & wetter conditions.

How does climate change affect species interactions?

Pollinators provide an important ecosystem service and it is therefore crucial to understand their response to climate change. Many pollinators dependent on temporal synchrony with their host plants and therefore asynchrony in shifts in phenology of both plants and insects could disrupt such interactions. Recent climate warming is associated with phenologcial advances in plant and animal species and there is now growing evidence that temporal mismatches between plants and animals occur. An important question, therefore, is what are the consequences for disrupted plant-pollinator interactions? Will an increase in mismatch between plants and their pollinators decrease reproductive output and affect population viability?

Possibility for Master projects.