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Hybrid genes

Hybridisation in damselflies
A major challenge in evolutionary biology is to understand how genetic variation is created and maintained. Recent studies confirm the old idea introduced by Anderson in the 1940’s in his monograph “introgressive hybridisation”, namely that hybridisation can provide a bridge for the genetic exchange of adaptations (genes that increase fitness). In general, it is thought that adaptive genes have a greater chance to cross species boundaries than key “speciation genes” or “genomics islands of divergence” which are should be more resistant to introgression.

An exciting opportunity to tackle this question is to study novel genetic combinations in recently originated hybrid zones, because they allow to study the creation and maintenance of unique genetic combinations within ecological time frames. In the last five years, the rapid development of next generation sequencing (NGS) technologies and the computational advancements of new techniques to analyse big data (such as large sub-sections of the genome) allows testing these ideas for the first time in unprecedented detail.

Researcher collecting damsel flies

Temperature induced range expansion can cause novel range overlap between formerly allopatric species and can lead to extensive hybridisation in these new sympatric areas. In my Marie Curie project, I will work with two closely related damselfly species Ischnura elegans and I. graellsii which show extensive and recent population overlap in southern Europe with strong and on-going hybridisation. The main hypothesis of this proposal is that adaptive genes have a greater chance to cross species boundaries than key speciation genes. To test this hypothesis, this proposal has three main objectives that address key challenges in the field: i) detailed quantification of introgression levels across the genome; ii) repeatability of the genetic architecture of speciation; and iii) repeatability of the genetic architecture of adaptation via introgressive hybridisation.

Species distribution of damsel flies

Species distribution of I. elegans (light gray) and I. graellsii (dark gray) (A and B). Individual admixture proportions inferred with STRUCTURE for K = 2 clusters for 22 populations of I. elegans and four I. graellsii populations (C). Individuals are represented by thin vertical lines, which are partitioned into segments representing each individual’s estimated membership fraction to each cluster (Sánchez-Guillén et al. 2011). Black circles denote sampled localities.

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Centre for Animal Movement Research
Evolutionary Ecology, Department of Biology
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