Johan Ehrlén

Courses

I am co-ordinating the master course "Interactions in ecological communities" (https://sisu.it.su.se/info/index/BL7042/en) that is given the second part of the spring semester.

Master student projects

I am happy supervise master student projects within the fields of phenology and plant-insect interactions. Check my research projects to perhaps get some ideas.

I am currently primarily working with four research projects:

(1) Natural selection underlying counter-gradient patterns of environmental and genetic effects of geothermal soil heating on timing of reproduction

In this project, we are examining how small-scale differences in temperature caused by geothermal soil heating influence plastic responses of flowering phenology of perennial plant species, and how this response influences natural selection and genetic responses. We are testing the predictions that: (1) Natural selection is acting to compensate for maladaptive plastic responses, (2) This selection will partly be mediated by interactions with pollinators, insect prey and herbivores, and (3) Higher soil temperatures are associated with small-scale spatial genetic differentiation and local adaptation exhibiting a counter-gradient pattern.

We use four main approaches to test these hypotheses; observational field studies to examine phenotypic trait selection, field experiments to assess the role of pollinators and prey availability as selective agents, climate chamber experiments with offspring from controlled crosses to examine genetically based differences in flowering time, and reciprocal transplantations of offspring from controlled crosses into field sites representing the full gradient of soil heating to assess phenotypic selection, genotypic selection and local adaptation.

This project is funded by the Swedish Research Council, VR.

(2) Selection on timing of reproduction in plants

The aim of this project is to move beyond the simple recognition that selection is spatially and temporally variable and understand what ultimately drives variation in selection. The project strives to not only explore how abiotic factors and mutualistic and antagonistic interactions influence selection on timing of reproduction in plants, but also to examine how these selective agents are influenced by variation in climatic conditions. Another key objective is to investigate how selection acts on reaction norms of flowering phenology to climatic factors. To study these questions, we use long-term data sets to link selection on timing of reproduction and climate and field experiments to identify selective agents and to study quantitative genetic variation in flowering time.

(3) Modelling effects of environmental and climate change on the abundance and distribution of plants

The aim of this project is to develop a modelling framework that links vital rates and population growth rates to key environmental variables and is able to forecast effects of climate change, environmental change and management actions on the abundance and distribution of species. The project deals with both general, theoretical aspects and applications to a number of plant systems in different ecosystems. One key objective is to find accurate and efficient ways to assess relationships between environmental drivers and vital rates. Another important objective is to quantify the effects of intra-specific density. The primary method of investigation is comparative demography, but also field experiments play an important role.

This project is a collaboration with Johan Dahlgren and Owen Jones, University of Southern Denmark and Kristoffer Hylander, Stockholm University, and is funded by the research council FORMAS.

(4) Developing a cost-efficient control program for the invasive plant Lupinus polyphyllus

In this project we will develop a cost-efficient program to control the invasive species Lupinus polyphyllus in Sweden. To reach this aim, we will use a two-fold approach. First, we will examine in what geographic regions and under what environmental conditions that Lupinus constitute a potential problem, and thus identify in what situations actions to control the species are at all needed. Second, we will assess how cost-efficient different management practices are to reduce long-term population growth rates in areas where the species constitute a potential problem. We will both explore the situation under current conditions, and future scenarios under different assumptions about climate change. Taken together, these results provide a solid basis for a cost-efficient control program, that is not only possible to implement episodically and at small spatial scales, but that is feasible to maintain over large areas and long time periods.

This project is a collaboration with Kristoffer Hylander, Stockholm University, and is funded by the Swedish Transport Administration and the research council FORMAS.