Density-dependent variation in reproductive success in a terrestrial orchid

2001 ◽  
Vol 227 (1-2) ◽  
pp. 27-36 ◽  
Author(s):  
E. J. Meléndez-Ackerman ◽  
J. D. Ackerman
Keyword(s):  
Reproductive Success ◽  
Terrestrial Orchid ◽  
Density Dependent

Regimes and stock-recruitment relationships in Japanese sardine (Sardinops melanostictus), 1951-1995

1998 ◽  
Vol 55 (11) ◽  
pp. 2455-2463 ◽  
Author(s):  
Tokio Wada ◽  
Larry D Jacobson
Keyword(s):  
Reproductive Success ◽  
Large Scale ◽  
Environmental Changes ◽  
Environmental Variability ◽  
Population Analysis ◽  
Search Time ◽  
Data Sets ◽  
Japanese Sardine ◽  
Density Dependent ◽  
Peak Abundance

We used reproductive success, rather than abundance or catch, to identify regimes because reproductive success responds faster to environmental changes. Peak abundance of Japanese sardine during 1951-1995 was about 1000 times higher than minimum abundance. A regime shift occurred in the early 1970s when carrying capacity (measured using spawner-recruit models) increased by about 75 times. We hypothesize that this was due to large-scale changes in the Kuroshio and Oyashio Current systems. Long-term environmental variation (regimes), interannual variability in recruitment success, and density-dependent recruitment and growth rates affected dynamics of Japanese sardine. We hypothesize that density-dependent effects on recruitment of Sardinops spp. are common but usually obscured in short data sets by environmental variability and measurement error. Virtual population analysis and forward-simulation modeling approaches gave similar biomass and recruitment estimates. The relationship between sardine biomass and catch per unit search time was nonlinear. Mass-at-age and biomass were correlated, and it may be possible to use mass-at-age as an abundance index. Current abundance is low, and we believe that the environment has shifted to a regime that is unfavorable for Japanese sardine.

Density-dependent hoarding by rodents contributes to large variation in seed mass of the woodland herb Symplocarpus renifolius

2007 ◽  
Vol 37 (9) ◽  
pp. 1675-1680
Author(s):  
Shigeru Uemura ◽  
Yasuhiro Sugiura
Keyword(s):  
Reproductive Success ◽  
Seed Mass ◽  
Maternal Plant ◽  
Density Dependent ◽  
Woodland Herb ◽  
Northern Japan

We analyzed effects of seed-hoarding by rodents on the variation in seed mass and seed success for a perennial forest undergrowth plant — Symplocarpus renifolius Schott ex Miquel — in Hokkaido, northern Japan. Although density of rodents differed greatly between seasons, more rodents were always captured in mesic Sasa sp. patches with dense foliage than in wet Lysichiton sp. patches. In the season with fewer rodents, they cached seeds close to the original places irrespective of vegetation, while in the season with abundant rodents, they transported seeds further and cached seeds disproportionately in Lysichiton patches. Seeds missed by rodents were larger than seeds that were eaten or that survived. Sasa patches are more suitable for seedlings to establish and a size advantage was observed there, but even small seeds could establish in Lysichiton patches, although seedling success was lower. We concluded that maternal plants of Symplocarpus renifolius increase their reproductive success by having small to middle-sized seeds transported to suitable sites while offering larger seeds as rewards to the transporters. Since the variation in seed mass was not correlated with the biomass per seed of the maternal plant, the large variation in seed mass is considered to have evolved through the density-dependent hoarding by rodents.

Mass‐ and Density‐Dependent Reproductive Success and Reproductive Costs in a Capital Breeder

1998 ◽  
Vol 152 (3) ◽  
pp. 367-379 ◽  
Author(s):  
Marco Festa‐Bianchet ◽  
Jean‐Michel Gaillard ◽  
Jon T. Jorgenson
Keyword(s):  
Reproductive Success ◽  
Reproductive Costs ◽  
Density Dependent ◽  
Capital Breeder
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