Barnacle demography:evidence for an existing model and spatial scales of variation

Abstract

A demographic model for an open population with space-limited recruitment has been previously proposed and tested using the barnacle Balanus glandula on a single shore in California. The model makes a number of qualitative predictions about population structure. At small scales, areas of high settlement should have on average less free space and fewer cohorts. At a larger unspecified scale (>34.6 cm2) cohort structure should be more variable in areas of high settlement. We attempted to test these quahtative predictions on a number of different spatial scales using the barnacle Semibalanus balanoides. A recruitment grad~ent was defined for S balanoides around the coast of Anglesey, Wales, with the north having lower recruitment than the south regardless of year. Given this recruitment gradient, a nested ANOVA was used to examine the qualitative predictions of the demographic model at different scales. The qualitative predictions of the demographic model were not generally supported by an analysis of data from Anglesey. Free space and small-scale population variance did not vary between areas of different recruitment density. Barnacle size variation was greater on high recruitment shores at an intermediate scale (100 m) as predicted by the model. However, this difference was not staUstically significant. Even at the scale of individual 5 X 5 cm photographs there was no evidence of a positive relationship between barnacle size variance and free space. Possible reasons for the mismatch of the demographic model predictions and empirical observations are discussed. There may be insufficient spatial sampling, insufficient recruitment difference, large-scale variation in mortality and growth rates, or the model assumptions may be incorrect. One important difference between the 2 levels of recruitment is that low recruitment sites had a constant patch size below 25 cmZ, whereas the high recruitment sites did not. If patch scale is variable, the predictions of the demographic model wlll be irrelevant as there is no single scale at which they can be observed. Use of the nested ANOVA technique with logarithmic spatial scales also allows hypotheses to be made about the important spatial sca1.e~ for future demographic studies using manipulative expenments. For population variance, free space and opercular length the important scales were small ( < l m), meso-(100 m), and large scales (>l0 km).

Spatially heterogeneous, synchronous settlement of Chthamalus spp. larvae in northern Baja California

“…Spatial heterogeneity in settlement numbers, on the other hand, has been interpreted as a result of the interaction between small-scale variability of transport mechanisms and larval behavior. Behavior and the local availability of suitable substrate might explain differing settlement numbers at the within-site scale in this study (see Raimondi & Keough 1990, Pineda 1994b, Hyder et al 1998). Among-site differences could be explained in terms of varying wave action (Caffey 1985) and onshore winds at a scale of 10s of kilometers (Hawkins & Hartnoll 1982), differing shoreline configuration at scales of 100s of meters (Archambault & Bourget 1999), varying mesoscale physical processes over scales of 100s to 1000s of kilometers (Connolly et al 2001), and differences in water column stratification (Pineda & López 2002).…”

“…Many studies published to date have focused on the larger-scale variability of larval settlement and/or recruitment using long sampling intervals (Hawkins & Hartnoll 1982, Hyder et al 1998, Archambault & Bourget 1999, Jenkins et al 2000, Connolly et al 2001, which have been correlated with physical mechanisms occurring at similar spatial and temporal scales. Studies conducted at smaller scales suggest that temporal variability in settlement rate might be related to larval pool and physical transport processes, while spatial variability might be associated with behavioral responses and substrate availability (Pineda 1994b).…”

Patterns of distribution of marine assemblages from rocky shores: evidence of relevant scales of variation

“…Only a few papers quantified the relative contribution of newly settled, juvenile, or adult organisms to the distributional patterns of the same species, also distinguishing brooders from free-spawners (Åberg & Pavia 1997, Hyder et al 1998, Hughes et al 1999, Benedetti-Cecchi et al 2000, Jenkins et al 2000. There are 3 papers (Fowler-Walker & Connell 2002, Irving et al 2004, Kelaher et al 2004) that have examined spatial patterns over very broad spatial scales (1000s of kilometers), at the expense of detailed middle and/or small-scale analyses.…”

“…Apparently, this was the only scale at which a pattern common to most organisms emerged. Patterns became idiosyncratic Azovsky et al (2004) both for modular and individual organisms when moving above the scale of meters (Farnsworth & Ellison 1996, Hyder et al 1998, Hughes et al 1999, Hull 1999, Jenkins et al 2001, Olabarria & Chapman 2001). Finally, very few studies examined simultaneously spatial and temporal variation, so that tests of space × time interactions are uncommon in the literature (Kennelly & Underwood 1992, Åberg & Pavia 1997, Underwood & Chapman 1998b, Menconi et al 1999, Jenkins et al 2000, Chapman 2002, Ysebaert & Herman 2002, De Biasi et al 2003.…”

Marine community ecology: importance of trait-mediated effects propagating through complex life cycles

“…Some evidence has been provided by observations (Connolly & Roughgarden 1998, Connolly et al 2001) and experiments (Fairweather 1988, Robles 1997. However, other tests did not give unambiguous support to the model (Hyder et al 1998, Menge 2000. Settlement and post-settlement factors may interact; if recruitment reflects settlement, that interaction explains why recruitment is necessary -but sometimes insufficient -for explaining adult population density (Menge 2000).…”