3WEDISH#YPRINID )NSIGHTS)NTO0ROCESSES OF$IVERGENCE ! "#"! $ % $$&'#"" ! " # $ # # %$ $&'$ ( ) $& *+& &, -( $. $"/ $/ % # &0 & 122&34 & & 256!6447621!6& $ $$ $ ( ## &- # 8 ( $ $ # $ 9 #&/ $$/ # $ -( $ #$ &0 $$ $$ # $ / $## # 8 # $&0 /# $ : $( # $ $ &'$ # $ : # $ ( : $ / $ ($ ($ $ # $ $ ## $ # ( &; # ( :$## # # <= # (>$ # # &? 6 # $ $ $ ( # ## :&+ ($ $ # # $ ($$## # #&0 #$ $ #$!5 #-( $ ( # $ ( ## 8& '$ # $ $ $ $ # ($ # &@$ #$ # ( ( ($ $/# $#$ $ ($ 6 & ; $# $$/ $:$$ # $8 # # & $ : 8 # $ ($ $-( $ #$. ! " " !# " !$ %&'! !"()*+,- ! A* + /--!14!61!7 /-,256!6447621!6 " """ 6! 51<$ "99 &8&9 B = " """ 6! 51> List of Papers This thesis is based on the following papers, which are referred to in the text by their Roman numerals. I Demandt, M. H., Björklund, M. (2007) Loss of genetic variabil- ity in reintroduced roach populations. Journal of Fish Biology (Supplement B), 70:255-261. II Demandt, M. H., Bergek, S. (2009) Identification of cyprinid hybrids by using geometric morphometrics and microsatellites. Journal of Applied Ichthyology (In Press). III Demandt, M. H. (2009) Stable levels of gene diversity despite low effective population size in isolated perch and roach popu- lations. Accepted manuscript (Conservation Genetics). IV Demandt, M. H. (2009) Phylogenetic relationship in Swedish cyprinid fish: evidence from mitochondrial and nuclear data. Submitted manuscript. V Demandt, M.H., Björklund, M. (2009) Rates of diversification in fishes. Manuscript. Paper I and II are published with kind permission of the publisher. Contents Introduction ..................................................................................................... 7 Biodiversity and Speciation ....................................................................... 7 Study species .............................................................................................. 9 Common bream, white bream and roach - members of the cyprinid family ..................................................................................................... 9 Species identification in common bream and white bream ................... 9 Sampling of fish ................................................................................... 11 Geometric morphometrics ................................................................... 11 Molecular tools .................................................................................... 12 Phylogenetic methods .......................................................................... 13 Aims of the thesis ..................................................................................... 14 Results and discussion .................................................................................. 15 Comparison of genetic variability in natural and reintroduced populations of roach (paper I) ...................................................................................... 15 Interspecific hybridization between common bream and silver bream (paper II) ................................................................................................... 16 Gene diversity in isolated perch and roach populations (paper III) ......... 18 Phylogenetic relationship in Swedish cyprinid fish (paper IV) ................ 19 Rates of diversification in fishes (paper V) .............................................. 21 Concluding remarks ...................................................................................... 23 Sammanfattning på svenska .......................................................................... 25 Zusammenfassung......................................................................................... 27 Acknowledgements ....................................................................................... 30 References ..................................................................................................... 32 Species names Scientific name English/ Swedish/ German Abramis brama Common bream/ braxen/ Brachsen Blicca bjoerkna White bream/ björkna/ Güster Rutilus rutilus Roach/ mört/ Rotauge Leuciscus leuciscus Dace/ stäm/ Hasel Leuciscus idus Ide/ id/ Aland Squalius cephalus Chub/ färna/ Döbel Phoxinus phoxinus Minnow/ elritsa/ Elritze Scardinius erythrophthalmus Rudd/ sarv/ Rotfeder Aspius aspius Asp/ asp/ Asp Leucaspius delineatus Sunbleak/ groplöja/ Moderlieschen Tinca tinca Tench/ sutare/ Schleie Gobio gobio Gudgeon/ sandkrypare/ Gründling Alburnus alburnus Bleak/ benlöja/ Ukelei Ballerus ballerus Zope/ faren/ Zope Vimba vimba Vimba bream/ vimma/ Zährte Pelecus cultratus Sichel/ skärkniv/ Sichelfisch Carassius carassius Crucian carp/ ruda/ Karausche Cyprinus carpio Common carp/ karp/ Karpfen Perca fluviatilis European perch/ abborre/ Flussbarsch Salvelinus alpinus Arctic charr/ röding/ Seesaibling Species names follow the common names for Europe according to FishBase (Froese & Pauly, 2007) Introduction Biodiversity and Speciation When Darwin published his book ‘The origin of species’ (Darwin 1859) he challenged the traditional way biologists had viewed the origin of biological diversity. Together with Alfred Russell Wallace, Charles Darwin proposed that biological diversity is the result of natural selection acting on heritable variation in populations (Darwin & Wallace 1858, Stern & Orgogozo 2009). However, how variation was inherited from one individual to its offspring was unknown to both of them. At the very end of the 19th century the studies of Mendel were rediscovered and laid the foundation of the discipline of population genetics. Today, one of the principal aims of population genetics is to quantify the amount of heritable variation present in nature. By doing so, biologists attempt to answer what determines the genetic differences between species, populations and individuals. These differences between species are created by forces such as natural and sexual selection, mutations, gene flow and random genetic drift. The advent of molecular tools (such as DNA sequencing or microsatellites) made it possible to gather fine scale information on species differences and also led to the rise of molecular sys- tematics, revealing information about the speciation process. One of the cen- tral problems of speciation is to understand what isolating barriers (prevent- ing gene flow between populations) are important for a given speciation event (Coyne & Orr 2004). Traditionally, allopatric speciation, where popu- lations become physically isolated by a barrier (e.g. mountain range), has been considered the default mode of how species arise. But more and more evidence accumulates that speciation can also occur in sympatry (Barluenga et al. 2006, Mavárez et al. 2006), i.e. populations diverge within the same geographic area. Irrespective of the mode of speciation, most of the concepts describing the process of speciation assume that new species are the result of splitting of old ones (Figure 1a). However, the possibility that new species arise by hy- bridization of older species (Figure 1b) is widely accepted among botanists, but zoologists perceived natural hybridization to be of little long-term evolu- tionary importance (Arnold 1997). 7 Figure 1. Speciation process as the result of lineage splitting (a) or hybridization (b) Hybridization between divergent evolutionary lineages may result in proge- ny with lower levels of fertility and /or viability, but may also create hybrid genotypes with equivalent or higher levels of fitness in certain environments. In the former case, the parental species are not affected as F1 hybrids are removed by natural selection (Arnold & Hodges 1995). However, in the latter case, fertile F1 hybrids can either cross with the initial hybrid genera- tion or backcross with their parental species leading to introgression. During the last two decades, a number of zoologists have concluded that natural hybridization is frequent and evolutionary important in taxa as divergent as birds and fish (Grant & Grant 1992, DeMarais et al. 1992). Despite the fact that the subject of speciation has attracted considerable attention, our understanding of the process of speciation still remains frag- mentary (Coyne & Orr 2004). Ever since Darwin presented his concept of evolution by natural selection it has been debated whether phenotypic evolu- tion takes place gradually or suddenly upon speciation (e.g. the theory of ‘punctuated equilibrium’, Eldredge & Gould 1972). From the fossil record inferences upon the features of evolutionary radiations can be made and reveal the tendency for diversification rates to decline through time. Recent accumulation of phylogenetic information has become increasingly impor- tant in understanding the modes of diversification leading to the present di- versity. Increasing availability of gene sequence data and the development of phylogenetic reconstruction from these data provide tools for analyzing the history of diversification in cyprinid fishes which allow estimates of rates of speciation and extinction (Nee et al. 1992, Rabosky & Lovette 2008). By using cyprinid species that hybridize with each other and thus have not reached the final stage of speciation, important insights into the evolu- tion of