Evaluating the importance of demographic connectivity in a marine metapopulation

Abstract

Recently researchers have gone to great lengths to measure marine metapopulation connectivity via tagging, genetic, and trace-elemental fingerprinting studies. These empirical estimates of larval dispersal are key to assessing the significance of metapopulation connectivity within a demographic context, but the life-history data required to do this are rarely available. To evaluate the demographic consequences of connectivity we constructed seasonal, size-structured metapopulation matrix models for two species of mytilid mussel in San Diego County, California, USA. The self-recruitment and larval exchange terms were produced from a time series of realized connectivities derived from trace-elemental fingerprinting of larval shells during spring and fall from 2003 to 2008. Both species exhibited a strong seasonal pattern of southward movement of recruits in spring and northward movement in fall. Growth and mortality terms were estimated using mark-recapture data from representative sites for each species and subpopulation, and literature estimates of juvenile mortality. Fecundity terms were estimated using county-wide settlement data from 2006-2008; these data reveal peak reproduction and recruitment in fall for Mytilus californianus, and spring for M. galloprovincialis. Elasticity and life-stage simulation analyses were employed to identify the season- and subpopulation-specific vital rates and connectivity terms to which the metapopulation growth rate (lambda) was most sensitive. For both species, metapopulation growth was most sensitive to proportional changes in adult fecundity, survival and growth of juvenile stages, and population connectivity, in order of importance, but relatively insensitive to adult growth or survival. The metapopulation concept was deemed appropriate for both Mytilus species as exchange between the subpopulations was necessary for subpopulation persistence. However, highest metapopulation growth occurred in years when a greater proportion of recruits was retained within the predominant source subpopulation. Despite differences in habitat and planktonic duration, both species exhibited similar overall metapopulation dynamics with respect to key life stages and processes. However, different peak reproductive periods in an environment of seasonal current reversals led to different regional (subpopulation) contributions to metapopulation maintenance; this result emphasizes the importance of connectivity analysis for spatial management of coastal resources.

Beyond connectivity: how empirical methods can quantify population persistence to improve marine protected‐area design

“…This would limit a study to calculating local retention, which can only permit a determination of self-persistence rather than network persistence. Several Christie et al (2010a) tropical, fish parentage analysis self-recruitment 3) Hogan et al (2012) tropical, fish genetic assignment tests self-recruitment, local retention, connectivity matrix 4) Christie et al (2010b) tropical, fish parentage analysis self-recruitment 5) Beldade et al (2012) tropical, fish parentage analysis self-recruitment 6) Jones et al (1999) tropical, fish tag microchemistry self-recruitment 7) Harrison et al (2012) tropical, fish parentage analysis self-recruitment 8) Jones et al (2005) tropical studies did estimate connectivity matrices , Carson et al 2011, Saenz-Agudelo et al 2011, Hogan et al 2012, and one study did link connectivity matrices with demographic processes to understand population persistence of two mussel species between two 30-40 km stretches of coast in southern California (Carson et al 2011). Parameterizing a formal population model with empirical measurements of connectivity and within-patch demographic processes, as in Carson et al (2011), is a particularly informative way to understand population persistence.…”

The application of genetics to marine management and conservation: examples from the Indo-Pacific

“…However, to be effective, it is recognized that networks of MPAs must be connected, either via adult or juvenile migration (Botsford et al 2009). Measuring connectivity using biological data is extremely difficult, but can involve tagging of migratory species or the use of otolith chemistry, trace-elemental fingerprinting, or trans-generational marking (see Levin 1990, Thorrold et al 2006, Cowen and Sponaugle 2009, Carson et al 2011.…”

Connectivity and population repatriation: limitations of climate and input into the larval pool

“…Mar Ecol Prog Ser 495: [175][176][177][178][179][180][181][182][183] 2014 of variation in recruitment (Hughes et al 2000, Reed et al 2009, Burrows et al 2010) and metapopulation growth (Carson et al 2011).…”