The salmonids. Salmonidae. Coregonus: the whitefishes

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1 The salmonids Kingdom Animalia -- Animal Phylum Chordata -- chordates Subphylum Vertebrata -- vertebrates Superclass Osteichthyes -- bony fishes Class Actinopterygii -- ray-finned fishes Subclass Neopterygii -- neopterygians Infraclass Teleostei World record king salmon Oncorhynchus tshawytscha Superorder Protacanthopterygii Order Salmoniformes Family Salmonidae -- salmonids 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 is hotly debated Salmonidae Coregoninae Coregonus Prosopium Stenodus Salmoninae Brachymystax Hucho Oncorhynchus Parahucho Thymallinae What is a species? Thymallus Salmo Salvelinus Salvethymus Coregonus: the whitefishes the whitefish problem Freshwater fish Species concepts Morphology? Genetics? Life history? Distribution Anadromy is common Produce large eggs ( parental care ) homing is often precise A study of Coregonus lavaretus 4 Kvernvika Body length (cm) Gløtfossen Fish sampled during spawning at spawning ground Hallsteinvika 34 Tufsinga 3 Sorkelva Femundsenden Tjønnan 32 Joneset Vestfjorden Hullet Storvika Coregonus albula Prosopium williamsoni Age (years) Within Femunden

2 Genetically distinct populations Grayling A. LAS 28 CA2 5.9% Tjø n n a n 27 Ve s t fjo r d e n 26 SCL F e mu n d se n d e n So rke l v a Gl ø t f o ss e n 25 HEL C. B. PRL UPW SNW Kv e r n vi ka Hu l le t POL ORL Ha l ls t ei n v ika 24 Tu f s i n g a Jo n e s e t 23 St o rv i ka ORH HEH CA SNH 79.5% INB UPL LOG+ UPG LOL D. E. 67 LOG UPG GIL UGL POL 6o Spring spawner - rivers and streams Growth in lakes / rivers Often forms schools 4 species (two common) Sexually dimorphic GIL ULO LGL mm SNH 7.26 ULO F. LOL A grayling example will be given in a later presentation. INL Østbye et al. 25. J evol Biol (in press) The salmon, trout and char Spawning habitat: Rivers Streams Lake beaches Estuaries? Juvenile habitat: All kinds of fresh waters ocean Spawning and rearing habitat Food Age and size dependent Habitat dependent Semelparous or iteroparous Anadromous or freshwater resident General life history: pacific salmon Oncorhynchus Semelparous Sockeye salmon Sockeye salmon Oncorhynchus nerka on spawning migration 2

3 Alternative life histories: jacks and hooknose coho salmon Oncorhynchus kisutch Pacific salmon: variation in fresh water dependence Length of fresh water phase Cutthroat trout (> yr) Rainbow trout (steelhead) (> yr) Chinook ( - multiple yr) Coho ( - multiple yr) Sockeye (> yr; incl lake residence) Chum (days) Pink (days) Soos Creek, Washington, USA Same system with chinook (king) salmon O. tshawytscha Atlantic salmon Importance of marine phase Pink (2 yr) Chum (> 2yr) Sockeye (-multiple yr) Coho ( - multiple yr) Chinook ( - multiple yr) Rainbow trout (steelhead) (weeks - few years) Cutthroat trout (weeks - few years) Yolk sac fry Egg iteroparous Parr Smolt Oceanic distribution of Atlantic salmon: Not well known Long-term variation in Norwegian Atlantic salmon catch Proportion grilse Water flow Summer flow. 5 5 Coastal distance Northern Norway Central Norway. Western Norway Skagerrak Latitude Mean Trend 8 Southern Central Northern Proportion grilse 9 Atlantic salmon in Norway: size distribution (proportion of grilse) Fra L Abée-Lund, Vøllestad & Beldring 24. Year Hirst et al. unpublished 3

4 Arctic char - Salvelinus alpinus Salmo and Salvelinus Note: phenotypic plasticity vs genetically fixed traits Alternative life history strategies Thingvallavatn, Iceland Importance of fresh water phase Char (residents common) Brown trout (residents common) Atlantic salmon (residents rare; usually males) Length of marine phase Atlantic salmon (> year; oceanic) Brown trout ( - several yrs; coastal) Char (weeks; coastal) Philopatry is common Genetic differentiation vs distance If migratory - they tend to return to their place of birth for spawning How they manage is still disputed Olfaction is clearly important Other senses may also be important What is the result of philopatry / homing? Reproductive isolation (separate gene pools / populations) Local adaptation is possible Fst Max distance Anadromous populations What does it mean? Genetic differentiation among populations Isolation by distance Gene flow mainly to nearby locations Dispersal or active migration? If local selection pressures differ: Local adaptation will occur A positive feedback loop Speciation process - if time allows Fst Coregonus Oncorhynchus Salmo Salvelinus Thymallus Genus 4

5 Genetic differentiation among populations - Oncorhynchus spp. Why philopatry or why disperse? Fst chinook chum coho cutthroat pink rainbow sockeye species All Pairs Tukey-Kramer.5 The difference between migration and dispersal Migration: a non-random process with a purpose Reproduction, survival, feeding Dispersal: a diffusion process State-dependent or completely random Why philopatry? - To increase the likelihood of finding a suitable breeding habitat and a mate? Philopatry should increase with decreasing availability of alternative breeding sites Straying among established populations is common (at a low rate) Good evidence for this hypothesis is lacking Why philopatry? - 2 Philopatry increases familiarity with local breeding conditions? should be higher for iteroparous species should be higher for the sex experiencing higher competition Should be lower for species with short fresh water phase (pink, chum) Generally, little direct evidence for this hypothesis. Why philopatry? - 3 Returns locally adapted individuals to 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 habitat What kind of selection pressures? competition predation 5

6 Why philopatry? - 4 Favored by spatial variation in habitat quality? Will increase when spatial variation is large compared to temporal variation May lead to density-dependence No data available to test this Why philopatry? - 5 Improves access to parental resources? Parentals provide resources (energy; highquality sites) But any previously used site would be just as good Why philopatry? - 6 Avoids the cost of movement? Dispersal is costly Less interesting for migratory species Probably not directly relevant as a hypothesis to explain homing in migratory species Remember - scale These arguments are developed mainly for anadromous species Just as valid for species/populations stationary in fresh water Selection pressures may vary across different scales Still: some fish disperse. Just an error or an evolutionary strategy (disperser have higher fitness)? Why disperse? - To buffer against temporal variation in habitat quality? Increase with increasing temporal variability Increase with increasing spatial asynchrony Some but not convincing evidence Why disperse? - 2 To colonize new environments? Should increase with increasing extinction probability Should be higher in new populations Difficult to evaluate because of pervasive anthropogenic influence But colonization events are common Are new environments often available? Is dispersal a heritable trait (and how)? Threshold trait/liability 6

7 Why disperse? - 3 To reduce inbreeding depression? Selection may favor behaviors that avoid breeding with kin Will increase with increasing inbreeding level Few studies in natural systems Effect of inbreeding will be transient Most important in small populations Good evidence is lacking If local adaptation is important - outbreeding may be a problem Why disperse? - 4 To reduce competition among kin? The concept of inclusive fitness Dispersal is probably only small-scale Not necessary to disperse out of the population Evidence is not strong 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 7