Larval dispersal. Settlement. Larval production Post-settlement. Sources of spatial and temporal variation in recruitment

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1 Sources of sptil nd temporl vrition in recruitment Lrvl dispersl Sources of sptil nd temporl vrition in recruitment Processes ffecting SETTLEMENT of lrve 1) Physicl processes Settlement Lrvl production Post-settlement ) iologicl processes hydroid scidin polychetes rittle str Lrvl ehvior: Pre-settlement Settlement I. Some types of lrvl ehvior II. Erly work on lrvl ehvior (mostly rncles) Golden ge ; received lot of ttention nd gret dvnces (e.g., Crisp, Knight Jones, Rylnd (ryozons), rnes) ) = response to light (e.g., ryozons, corls, fish) ) = swim up or swim down (mny inverts nd fish) c) = orient to currents (mny inverts nd fish) Most of the work ws motivted y field oservtions ut generlly done in l with field collected or cultured lrve d) = orient to surfce texture (inverts, not fish) e) = orient to wter or surfce chemistry (inverts nd fish) 1

2 Exmple 1: Gregrious settlement Knight Jones 193 Pttern: rncle ggregtions on shoreline seemed to e species-specific (like settled next to like) Hypothesis: Gregrious settlement response is species specific (i.e., conspecific fcilittion ) Test: Settlement of: (1) species #1 () species # (3) species #3 1 % settlement Surfce with dults of: I none I none I 3 none 8 8 generl results! Conclusions: Settlement much greter in presence of inducer Inducer is species-specific ( gregrious ehvior) Why settle gregriously? ut, wht is the reltionship etween gregrious settlement nd post-settlement growth nd mortlity? Costs of gregrious ehvior: fertiliztion, reproductive success post-settlement growth, survivorship Distnce etween neighors Distnce etween neighors

3 Exmple : Territorility t settlement - Crisp types of distriutions re possile generted y 3 ehviorl mechnisms: Species: lnus lnoides Pttern: 1) just showed tht. lnoides settle gregriously ) however, t smller sptil scle, individuls seem to e spced out more thn expected y purely gregrious settlement. Dispersion: clumped rndom uniform Hypothesis: pttern of settlement chnges with sptil scle; t smller scles, different from gregrious Mechnism: % frequency of occurrence clumped rndom uniform % frequency of occurrence clumped rndom uniform short distnce to nerest neighor (mm) fr short distnce to nerest neighor (mm) fr Test: smpled settlement distriution of. lnoides to test for these predicted frequency distriutions of distnce Conclusions: Territoril ehvior t settlement - cked up w/oservtions of lrve settling in the l. 3

4 Exmple 3: Fcilittive settlement in corl reef fishes nderson et l. 7 MEPS Results: 1 System: lue dmselfish, Chromis cyne on corl reefs in hms Pttern: highly ggregted distriution, especilly recently settled juveniles Men # settlers /corl hed Present sent Residents Hypothesis: ggregtions creted y ehviorl preference to settle with resident conspecifics Cumultive no. settlers / corl hed 1 1 Test: Men # residents / corl hed III. The evolution of ehviorl cues for settlement Why hve ehviorl cues for settlement? Two kinds of costs (mistkes) 1) Cue occurs in inpproprite hitts leds to settlement in inpproprite conditions ) Not ll pproprite plces hve the cue (e.g. think out corl heds without lue chromis) high Why not lwys hve cues? = deth cost of mistke (not using cue) high Proility of evolving response to cue low low low reliility of cue high 4

5 Given the costs of dpting to inpproprite cues, how mny species exhiit this ehvior to so mny different kinds of cues the implied strength of selection for these ehviorl responses the importnce of settlement s life-long consequence for fitness (especilly for sessile species) cn ll this ehvior t settlement contriute to those ptterns tht drove ecologists to study intertidl ecology (i.e. ptterns of zontion)?? IV. Contriution of lrvl ehvior to verticl zontion ptterns Processes ffecting zontion 4 possiilities 1) Lrve my e strtified in wter column (ehvior or hydrodynmic effects) nd lnd t different tidl heights dult pttern (zontion): Processes ffecting zontion 4 possiilities ) Lrve my (1) e mixed in wter column, () exhiit settlement ehvior (3) settle within pproprite zone dult pttern (zontion): Processes ffecting zontion 4 possiilities 3) lrve my (1) e mixed in wter column, () show no settlement ehvior (3) settle rndomly nd (4) die ck to crete dult zontion pttern dult pttern (zontion):

6 Exmple: Strtifiction of lrve in wter column Processes ffecting zontion 4 possiilities Groserg 198, senior thesis! 4) Individuls my move fter settlement dult pttern (zontion): System: Snt Cruz hror, species of rncle on pier pilings lnus glndul nd lnus crentus 1.8 Pttern:. glndul Tide height (m). crentus dult Density (#/1 cm ) Question: Wht cuses verticl zontion? Results: Generl hypotheses: H 1 : erly post-settlement mortlity limits species distriution (sensu Connell) H : strtifiction of lrve limits distriution vi ehvior Test: 1 x 1 cm pltes Smpled weekly during period of high settlement - llows detection of 1 7 dy old individuls Tidl height.1-1. dult pttern 1.8 Settlement pttern Tidl. glndul height crentus Settler density (#/1cm ) dult Density (#/1 cm ) 1.8. glndul. crentus Settler density (#/1cm ) 6

7 Conclusions: 1) settlement ws sme distriution s dults ) not post-settlement processes cusing dult distriution H : strtifiction of lrve limits distriution vi ehvior Test: Used plnkton pulls to smple the wter colume on 3 dys: new, full, hlf moon smpled hourly for 4 hour periods on ech dy smpled from floting dock t 4 depths: 1.8 Tidl rnge smpled surfce,. m, 1. m, nd 3 m smpling rnge: -4 m to 1.8 m 3m surfce 3m depth -4. Time of dy Results differ etween species: 1) 94% of glndul lrve tken in surfce wters (irrespective of tidl sequence) ) 98% of crentus lrve were collected < m mllw, (mening their distriution in wter column chnged s function of tide!) Lrvl undnce 1.8 Tidl rnge smpled -4.. glndul. crentus Time of dy surfce. glndul. crentus Conclusions: 1) Distriution of dults determined y position of lrve in wter column ) Lrvl distriution set y two different ehviors:. glndul stys in surfce wter, which over tidl sequences trvels from out -1. to 1.8 m (undnces correspond to time t tidl height). crentus stys elow prticulr tidl level (how might it do tht?) 7

8 V. Role of physicl structure (e.g. kelp, segrss, corl heds ) s cue for settlement Exmple: Crr 1994 Ecology within reefs Density of kelp ss recruits (No. per 6 m 3 ) 3 1 P <.1 Pttern: mong reefs nd yers kelp ss recruit density Mcrocystis density (Stipes per 3 m ) sent Present Mcrocystis Density of kelp ss settlers increses with incresing density of gint kelp ut it is not liner! Generl hypothesis: kelp cts to promote recruitment of kelp ss Specific Hypothesis: Locl kelp ss recruitment should correlte to mnipulted density of gint kelp kelp ss recruit density: (Numer / 1 m ) lde iomss per reef re: (grms / 1 m ) 1, Mcrocystis density (stipes / 3 m ) kelp ss recruit density: (Numer per 1 m ) 6 4 1, 1, lde iomss (gm per m 3 ) Conclusions: Locl nd regionl ptterns of kelp ss recruitment re influenced y dynmics of gint kelp undnce The reltionship is not sed strictly on plnt density, ut on iomss (shelter!). ecuse kelp iomss chnges with plnt density, recruitment reltionship is symptotic. Gint kelp fcilittes recruitment of kelp ss y providing hitt tht they encounter s they pss over reefs 8

9 Lots of exmples of role of hitt structure Sources of sptil nd temporl vrition in recruitment In ddition to Mcrocystis nd kelp ss e.g., Crr 1994, Ecology Mcrocystis nd kelp surfperch e.g., nderson 1994, MEPS Se urchins nd luended goy e.g., Hrtney nd Grorud, Oecologi Segrss nd Cllinectes (lue crs) Post-settlement: - survivl - growth - movement V. (Erly) post-settlement processes s sources of vrition in recruitment Density-independent Density-dependent Recruitment estimtes occur t some point susequent to settlement, so survivorship: # dults: recruits! survivorship: # dults: recruits! 1% --Do post-settlement processes lter ptterns of settlement? --Cn post-settlement processes cuse densitydependent mortlity tht would de-couple ptterns of settlement nd recruitment? --How importnt re competition nd predtion s sources of vrition in recruitment ND densitydependent mortlity? % % % #settlers #settlers #settlers #settlers density independence: sme proility of surviving regrdless of density direct reltionship etween settler # nd recruit # density dependence: no reltionship etween settler # nd recruit # 1 9

10 Sources of sptil nd temporl vrition in recruitment Generl pproch: 1) To test for predtor effects, mnipulte presence nd sence of predtors Post-settlement: - survivl - growth - movement predtion competition ) To test for density-dependence, mnipulte density of settlers 3) To test for density dependence cused y predtion, mnipulte OTH orthogonlly Erly post-settlement mortlity: predtion Conclusions 1. per-cpit mortlity lck eyed goy.4.. kelp 1 1 perch Initil density nderson Ecology predtors present predtors sent 1. Steele 1997 Oecologi kelp rockfish Johnson 6 Ecology (1) Post-settlement mortlity is source of vrition in recruitment () Predtion is n importnt source of postsettlement mortlity (3) Predtion is lso source of density-dependent mortlity, which cn decouple estimtes of settlement nd recruitment