Kingdom Animalia -- Animal The salmonids Phylum Chordata -- chordates Subphylum Vertebrata -- vertebrates Superclass Osteichthyes -- bony fishes Class Actinopterygii -- ray-finned fishes Subclass Neopterygii -- neopterygians Infraclass Teleostei World record Superorder Protacanthopterygii king salmon Order Salmoniformes Oncorhynchus Family Salmonidae -- salmonids tshawytscha

Subfamily Coregoninae - whitefishes Subfamily Salmoninae - salmon and trout Subfamily Thymallinae - grayling

One of the most studied groups of fish: still the number of species and their relationship Salmonidae is hotly debated!

Coregoninae Salmoninae Thymallinae • What is a species? • Freshwater fish – Species concepts – Anadromy is common Coregonus Brachymystax Thymallus – Morphology? – Produce large eggs Prosopium Hucho Stenodus Oncorhynchus – Genetics? (“parental care”) Parahucho – Life history? – “homing” is often precise Salmo – Distribution Salvelinus Salvethymus

Coregonus: the whitefishes A study of Coregonus lavaretus 40

“the whitefish problem” Kvernvika 38 ! Gløtfossen ! Fish sampled during 36 spawning at spawning ) Hallsteinvika ground

m

c !

( 34 h Tufsinga t ! Sorkelva g !

n Femundsenden !! Tjønnan

e

l

32

y

d

o B 30 ! Joneset ! Vestfjorden ! Hullet ! Storvika 28

26 Coregonus albula Prosopium williamsoni 0 5 10 15 20 25 30 35 Age (years) Within Femunden

1 Genetically distinct populations! A.

LAS Grayling 28 CA2 5.9% Tjøn n a n

27

F e mu n d se n de n SCL 26 Vest fjorde n Sorke lv a

Gløt fosse n • Spring spawner - rivers 25 HEL Kv e rn vika Hu lle t B. C. POL Ha llst ein v ika and streams 24 ORL Tu fsin ga PRL UPW SNW Jon e se t • Growth in lakes / rivers 23 St orv i ka ORH CA1 HEH SNH 79.5% 22 • Often forms schools 66 67 68 69 70 71 72 73 74 75 76 77

INB UPL LOG+ 28.8 30.1 36.1 43.5 UPG • 4 species (two common) LOL

GIL 5.44 5.90 7.96 9.25 LOG UPG • Sexually dimorphic D. E. UGL POL 30.8 31.7 32.5 60o 31.8

ULO GIL SNH 7.26 7.62 7.21 7.60 7 6 5 4 3 2 1 0 mm LGL

ULO 3.13 2.82 2.43 2.66

F. LOL 22.9 23.4 24.3 24.6

INL A grayling example will be given in a later presentation. Østbye et al. 2005. J evol Biol (in press)

The salmon, trout and char Spawning and rearing habitat

• Spawning habitat: • Food – Rivers – Age and size – Streams dependent – Lake beaches – Habitat dependent – Estuaries? • Semelparous or • Juvenile habitat: iteroparous – All kinds of fresh waters • Anadromous or – ocean freshwater resident

General life history: pacific salmon Oncorhynchus

Sockeye salmon Sockeye Oncorhynchus nerka Semelparous on spawning migration salmon

2 Alternative life histories: jacks and hooknose coho salmon Oncorhynchus kisutch Pacific salmon: variation in fresh water dependence • Length of fresh water • Importance of marine phase phase – Cutthroat trout (>1 yr) – Pink (2 yr) – Rainbow trout (steelhead) – Chum (> 2yr) (> 1 yr) – Sockeye (1-multiple yr) – Chinook (0 - multiple yr) – Coho (0 - multiple yr) – Coho (0 - multiple yr) – Chinook (0 - multiple yr) Soos Creek, Washington, USA – Sockeye (> 1 yr; incl lake – Rainbow trout (steelhead) residence) (weeks - few years) – Chum (days) – Cutthroat trout (weeks - few – Pink (days) years) Same system with chinook (king) salmon O. tshawytscha

Atlantic salmon Yolk sac fry

Egg iteroparous

Parr

Smolt Oceanic distribution of Atlantic salmon: Not well known

Long-term variation in Norwegian Atlantic salmon catch Atlantic salmon in Norway: size distribution (proportion of grilse)

Western Norway 1 Skagerrak 1.0 1.0 9 Southern 0.8 0.8 Central Northern 0.6 0.6 0.5 0.4 0.4

8 0.2 0.2 0 0.0 0.0 1980 1985 1990 1995 2000 1980 1985 1990 1995 2000 0.1 1 10 100 1000 0.0 0.2 0.4 0.6 0.8 1.0 Water flow Summer flow 1 1.0 1.0 Proportion grilse 7 Proportion grilse 0.8 0.8

Mean Trend 0.6 0.6 0.5 0.4 0.4 0.2 0.2 6 Central Norway Northern Norway 0.0 0.0 0 0 50 100 150 200 55 60 65 70 75 1980 1985 1990 1995 2000 1980 1985 1990 1995 2000 Coastal distance Latitude 5

1880 1900 1920 1940 1960 1980 2000 Fra L’Abée-Lund, Vøllestad & Beldring 2004.

Year Hirst et al. unpublished

3 Arctic char - Salvelinus alpinus Salmo and Salvelinus

Thingvallavatn, Iceland • Importance of fresh • Length of marine water phase phase – Char (residents – Atlantic salmon (> 1 common) year; oceanic) – Brown trout (residents – Brown trout (0 - common) several yrs; coastal) – Atlantic salmon – Char (weeks; coastal) (residents rare; usually males) Note: phenotypic plasticity vs genetically fixed traits Alternative life history strategies

Genetic differentiation vs distance Philopatry is common

• If migratory - they tend to return to their place of 0.2

birth for spawning 0.15 – How they manage is still disputed 0.1 – Olfaction is clearly important Fst

– Other senses may also be important 0.05 • What is the result of philopatry / homing? 0 – Reproductive isolation (separate gene pools / 0 1000 2000 3000 4000 5000 6000 7000 populations) Max distance – Local adaptation is possible

Anadromous populations

Genetic differentiation among populations What does it mean?

0.6

• “Isolation by distance” 0.5

• Gene flow mainly to nearby locations 0.4

0.3 – Dispersal or active migration? Fst

• If local selection pressures differ: 0.2

– Local adaptation will occur 0.1

– A positive feedback loop 0

– Speciation process - if time allows Coregonus Oncorhynchus Salmo Salvelinus Thymallus

Genus

4 Genetic differentiation among populations - Oncorhynchus spp. Why philopatry or why disperse?

0.6 • The difference between migration and 0.5 dispersal 0.4 – Migration: a non-random process with a

0.3

Fst purpose 0.2 • Reproduction, survival, feeding 0.1 – Dispersal: a diffusion process 0 • State-dependent or completely random

chinook chum coho cutthroat pink rainbow sockeye All Pairs Tukey-Kramer 0.05 species

Why philopatry? - 1 Why philopatry? - 2

• To increase the likelihood of finding a • Philopatry increases familiarity with local suitable breeding habitat and a mate? breeding conditions? – Philopatry should increase with decreasing – should be higher for iteroparous species availability of alternative breeding sites – should be higher for the sex experiencing higher competition • Straying among established populations is – Should be lower for species with short fresh water common (at a low rate) phase (pink, chum) • Good evidence for this hypothesis is • Generally, little direct evidence for this lacking hypothesis.

What kind of selection Why philopatry? - 3 pressures? • Returns locally adapted individuals to habitat predation appropriate habitats? – Divergent selection between environments – Reduced individual fitness at non-natal sites • Large body of evidence to support this – Selection against strays – Adaptation and homing will reinforce each other in a positive feedback loop competition

5 Why philopatry? - 4 Why philopatry? - 5

• Favored by spatial variation in habitat • Improves access to parental resources? quality? – Parentals provide resources (energy; high- – Will increase when spatial variation is large quality sites) compared to temporal variation • But any previously used site would be just – May lead to density-dependence as good! • No data available to test this

Why philopatry? - 6 Remember - scale

• Avoids the cost of movement? • These arguments are developed mainly for anadromous species – Dispersal is costly • Just as valid for species/populations stationary in – Less interesting for migratory species fresh water • Probably not directly relevant as a • Selection pressures may vary across different hypothesis to explain homing in migratory scales species • Still: some fish disperse. Just an error or an evolutionary strategy (disperser have higher fitness)?

Why disperse? - 1 Why disperse? - 2

• To buffer against temporal variation in • To colonize new environments? habitat quality? – Should increase with increasing extinction probability – Should be higher in new populations – Increase with increasing temporal variability • Difficult to evaluate because of pervasive – Increase with increasing spatial asynchrony anthropogenic influence • Some but not convincing evidence • But colonization events are common – Are new environments often available? – Is dispersal a heritable trait (and how)?

Threshold trait/liability

6 Why disperse? - 3 Why disperse? - 4

• To reduce inbreeding depression? • To reduce competition among kin? – Selection may favor behaviors that avoid breeding with kin – The concept of inclusive fitness – Will increase with increasing inbreeding level • Dispersal is probably only small-scale • Few studies in natural systems – Not necessary to disperse out of the population – Effect of inbreeding will be transient – Most important in small populations • Evidence is not strong – Good evidence is lacking – If local adaptation is important - outbreeding may be a problem

Some concluding remarks

• Philopatry, breeding at the same place as your parents, has probably evolved to return locally adapted individuals to an appropriate habitat – It worked for my parents - it will probably work for me – To try something else is risky – Is there suitable habitat? Are the mates? • Why migrate? – Will be discussed next week

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