Contributions of growth, stasis, and reproduction to fitness in brooding and broadcast spawning marine bivalves

Abstract

Reproductive modes in marine invertebrates can be generally grouped into two types: those brooding larvae and those broadcast‐spawning gametes into the water. We asked if these different life‐history strategies differ based on how contribution to fitness is partitioned between growth, stasis, and reproduction. To investigate this question, we used published demographic data on ten diverse species of marine bivalves. We parameterized simple matrix‐population models and calculated the sums of elasticities to growth, stasis, and reproduction parameters and plotted the results on triangular axes. We also assessed whether contribution patterns were correlated with reproductive mode and tropical, temperate, or polar environments. We found that some of the broadcast spawners fell in the region of the plot with high elasticities for stasis and that some of the brooders fell in the region of the plot with higher growth and reproduction elasticities than stasis ones. However, instead of a sharp dichotomy, we found a continuum in contributions of stasis parameters with long‐lived brooders and short‐lived broadcast spawners in the same region of the plot. There was no clear pattern of reproductive mode associated with any particular environment, but we think these preliminary results are intriguing and that further work on comparative demography of marine invertebrates is warranted.

Evaluating the importance of demographic connectivity in a marine metapopulation

“…1) and county-wide surveys of adult cover conducted in 2005 . Fecundity (F ) was estimated using the methods of Ripley and Caswell (2008) who estimated fecundity for some bivalve species as follows:…”

New logo and updated editorial board

“…We published eight papers (20.0%) from these research fields in 2008 (i.e., Ando and Ohgushi 2008;Berry et al 2008;Chien et al 2008;Evans et al 2008;Kelly et al 2008a, b;Masaki et al 2008;Yoshimoto and Nishida 2008). The increase in the number of manuscripts on bird and marine/aquatic invertebrate populations is also noteworthy, although their absolute numbers are still not too large (i.e., Duhem et al 2008;Fujisaki et al 2008;Ripley and Caswell 2008;Takada 2008).…”

Cyanobacteria reduce motility of quagga mussel (Dreissena rostriformis bugensis) sperm

“…Because HABs occur more frequently with an earlier seasonal onset, overlap with broadcast spawning events becomes more likely. Broadcast spawners release gametes directly into the water column, resulting in external fertilization (Ripley and Caswell ). This reproductive strategy allows for higher fecundity than brood spawners, but comes at a cost of lower juvenile survival and potentially leaves gametes susceptible to environmental conditions, such as annual phytoplankton blooms (Ripley and Caswell ).…”

“…Broadcast spawners release gametes directly into the water column, resulting in external fertilization (Ripley and Caswell ). This reproductive strategy allows for higher fecundity than brood spawners, but comes at a cost of lower juvenile survival and potentially leaves gametes susceptible to environmental conditions, such as annual phytoplankton blooms (Ripley and Caswell ). Although broadcast spawning is common in marine invertebrates, it is rare in freshwater invertebrates (Misamore and Lynn ).…”