Appendix 1 Hypothetical relationships between juvenile densities (y axis) and adult densities (x axis), and the underlying processes that may be responsible for each relationship (assuming overlap in habitat use between age classes occurs). The type of settlement pattern required for each process is described as (i) selective – settling larvae display habitat preferences and are able to choose settlement habitats, (ii) passive – settling larvae are unable to select specific settlement habitats and settle randomly, or (iii) either- the process can occur regardless of whether or not settlement is selective or passive. In addition, the possibility that a particular process could lead to intercohort density dependence (DD) is indicated by a yes (Y) or a no (N). In some cases (marked with an *), density dependence could only occur if (i) settlement is selective and (ii) there is lower survival in the selected habitat. The authors acknowledge that this is not an exhaustive list of potential hypotheses, but rather a list of observed processes in the literature
Expected relationship / Potential processes / Passive or selective settlement / DD / Literature/ No effect of adult conspecifics / Either / N / Levin 1993
Passive (non-selective) settlement of settlers across habitats / Passive / N / Forrester 1999
Sub-lethal effects of adults on settler growth and maturity / Either / N / Jones 1987, Tupper and Boutilier 1995
/ Settlers use resident adults as settlement cues / Selective / N / Hunt 2011, Stamps and Krishnan 2005
Juvenile recruitment success predicts future adult distributions (i.e. densities are correlated within habitat patches from year to year) / Either / N / Gutiérrez 1998
Co-variation of settler habitat quality and adult density / Either / Y
(cryptic DD) /N / Shima and Osenberg 2003
/ Competitive exclusion from habitats by adults / Either / Y / Samhouri 2009, Webster 2004
Cannibalism / Either / Y / Bjørnstad 1999
Settlers shift habitat preferences as adult density increases to avoid settling near adults / Selective / Y*/ N / Ayllón 2012
/ Combination of facilitation by prior residents or co-variation in habitat quality (positive) combined with competition/cannibalism (negative) / Either / Y / Adam 2011
Facilitation by prior residents or co-variation in habitat quality (positive) combined with differential habitat selection by settlers at high adult densities / Selective / Y*/ N / -
References
Adam TC (2011) High-quality habitat and facilitation ameliorate competitive effects of prior residents on new settlers. Oecologia 166:121–130. doi: 10.1007/s00442-010-1826-7
Ayllón D, Nicola GG, Parra I, et al. (2013) Intercohort density dependence drives brown trout habitat selection. Acta Oecologica 46:1–9. doi: 10.1016/j.actao.2012.10.007
Bjørnstad O, Fromentin J, Stenseth N, Gjøsaeter J (1999) Cycles and trends in cod populations. Proc Natl Acad Sci U S A 96:5066–71. doi: 10.1073/pnas.96.9.5066
Forrester GE (1999) The influence of adult density an larval settlement in a coral reef fish, Coryphopterus glaucofraenum. Coral Reefs 18:85–89. doi: 10.1007/s003380050159
Gutiérrez L (1998) Habitat selection by recruits establishes local patterns of adult distribution in two species of damselfishes: Stegastes dorsopunicans and S. planifrons. Oecologia 115:268–277. doi: 10.1007/s004420050516
Hunt T, Ford J, Swearer S (2011) Ecological determinants of recruitment to populations of a temperate reef fish, Trachinops caudimaculatus (Plesiopidae). Mar Freshw Res 62:502–509. doi: http://dx.doi.org/10.1071/MF10262
Jones GP (1987) Competitive interactions among adults and juveniles in a coral reef fish. Ecology 68:1534–1547. doi: 10.2307/1939237
Levin PS (1993) Habitat structure, conspecific presence and spatial variation in the recruitment of a temperate reef fish. Oecologia 94:176–185. doi: 10.1007/BF00341315
Samhouri JF, Steele MA, Forrester GE (2009) Inter-cohort competition drives density dependence and selective mortality in a marine fish. Ecology 90:1009–1020. doi: 10.1890/07-1161.1
Shima JS, Osenberg CW (2003) Cryptic density dependence: effects of covariation between density and site quality in reef fish. Ecology 84:46–52.
Stamps J, Krishnan V (2005) Nonintuitive cue use in habitat selection. Ecology 2860–2867. doi: http://dx.doi.org/10.1890/05-0290
Tupper M, Boutilier RG (1995) Effects of conspecific density on settlement, growth and post-settlement survival of a temperate reef fish. J Exp Mar Bio Ecol 191:209–222. doi: 10.1016/0022-0981(95)00058-Y
Webster M (2004) Density dependence via intercohort competition in a coral-reef fish. Ecology 85:986–994. doi: http://dx.doi.org/10.1890/02-0576