| 421. |
- Olsson, M, et al.
(författare)
-
Sperm choice and sperm competition: suggestions for field and laboratory studies
- 1999
-
Ingår i: OIKOS. - : MUNKSGAARD INT PUBL LTD. - 0030-1299. ; 84:1, s. 172-175
-
Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- The recent explosion of research on sperm competition, and the emerging idea that females may control paternity of their offspring via "sperm choice", raise many methodological questions. One central issue is the role of inbreeding-induced mortality of of
|
|
| 422. |
- Olsson, O
(författare)
-
Divorce in king penguins: asynchrony, expensive fat storing and ideal free mate choice
- 1998
-
Ingår i: OIKOS. - : MUNKSGAARD INT PUBL LTD. - 0030-1299. ; 83:3, s. 574-581
-
Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- In long-lived and monogamous species, with partners separated between breeding seasons, the previous mate usually returns and waiting is therefore rewarded, thus contributing to mate retention as an adaptive strategy. However, in the long-lived monogamous
|
|
| 423. |
- PALMER, MW, et al.
(författare)
-
VARIANCE IN SPECIES RICHNESS, SPECIES ASSOCIATION, AND NICHE LIMITATION
- 1995
-
Ingår i: OIKOS. - : MUNKSGAARD INT PUBL LTD. - 0030-1299. ; 73:2, s. 203-213
-
Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- A low variance in species richness, relative to a null model, has been proposed as evidence for niche limitation in ecological communities. We demonstrate that niche limitation does not inevitably lead to low variance in species richness. Furthermore, low
|
|
| 424. |
- Pamilo, P, et al.
(författare)
-
Reproductive skew simplified
- 1996
-
Ingår i: OIKOS. - : MUNKSGAARD INT PUBL LTD. - 0030-1299. ; 75:3, s. 533-535
-
Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)
|
|
| 425. |
- Partel, M, et al.
(författare)
-
The species pool and its relation to species richness: Evidence from Estonian plant communities
- 1996
-
Ingår i: OIKOS. - : MUNKSGAARD INT PUBL LTD. - 0030-1299. ; 75:1, s. 111-117
-
Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- Two types of species pool are distinguished. The regional species pool is defined as the set of species, occurring in a certain region (here: Estonia) which are capable of coexisting in a target community. The actual species pool is defined as the set of
|
|
| 426. |
- Persson, Anders
(författare)
-
Effects of Fish Predation and Excretion on the Configuration of Aquatic Food Webs
- 1997
-
Ingår i: Oikos. - 1600-0706. ; 79:1, s. 137-146
-
Tidskriftsartikel (refereegranskat)abstract
- The relative importance for algae of fish excretion and fish predation on zooplankton was studied in experimental pools. Even- (zoo- and phytoplankton) and odd-link systems (planktivorous fish, zoo- and phytoplankton) were established, in which the standing stock of primary producers was expected to follow the predictions from food chain theory sensu Oksanen. Two intermediate treatments (fish predation and nutrient regeneration by fish alone) were used to determine the relative power of fish in affecting the transition from an even-link system to an odd-link system, i.e. their relative power in the trophic cascade. Algal density and production were found to only be enhanced when both fish predation and fish excretion acted together. A reduction in the grazer biomass alone did not increase the algal biomass. Fish excretion alone increased the algal biomass somewhat, but not significantly so compared with the control. The results suggest that both fish predation on zooplankton and the regeneration of nutrients by fish may be necessary to create the difference in algal biomass between an even- and an odd-link system predicted by food chain models, at least in the absence of an external input of nutrients. In addition, the effects of increased nutrient regeneration due to use of non-zooplankton resources by the fish, nutrient maintenance in living biota, and decreased grazing pressure seem to reinforce the cascading effect of planktivorous fish on algae. Consequently, use of a fixed carrying capacity in simple predatorprey models may lead to loss of important information on the dynamics of aquatic food webs, preventing an adequate understanding of cascading trophic interactions from being achieved.
|
|
| 427. |
- Persson, B. R.R., et al.
(författare)
-
Radiolead (210Pb) and stable lead in the lichen Cladonia alpestris
- 1974
-
Ingår i: Oikos. - : JSTOR. - 0030-1299. ; 25:2, s. 140-147
-
Tidskriftsartikel (refereegranskat)abstract
- Lichens of the genus Cladonia, mainly C. alpestris, collected during 1882-1972 were analyzed for stable lead and 210Pb. The specific activity of 210Pb (210Pb/Pb ratio) indicates a constant value of about 2 mCi/kg up to 1940, and then decreased to 0.6 mCi/kg during 1950-1960. As the average annual 210Pb deposition is relatively constant, the decrease in the 210Pb/Pb ratio after 1940 indicates an increased deposition of stable lead after 1940. A single exponential variation of the 210Pb/Pb ratio, in respect to latitude, was found in lichens collected in 1964. Values for 210Pb and stable lead in C. alpestris, collected in central Sweden during 1961-1972, appear to be relatively constant and the average area content of 210Pb and stable lead in lichen carpets was 15 ± 2 nCi/m2 and 25 ± 5 mg/m2 respectively. The pattern of vertical distribution was converted to a model for the translocation of lead in lichens, which included the diffusion principle. The diffusion coefficient for lead in the top layer of the lichen carpet was estimated to be about (0.2 ± 0.1) x 10-6 cm2 x s-1.
|
|
| 428. |
|
|
| 429. |
- Ripa, Jörgen
(författare)
-
Ecology and macroevolution – evolutionary niche monopolisation as a mechanisms of niche conservatism
- 2018
-
Ingår i: Oikos. - : Wiley. - 0030-1299. ; 128, s. 380-391
-
Tidskriftsartikel (refereegranskat)abstract
- Explaining macroevolution from microevolution is a key issue in contemporary evolutionary theory. A recurrent macroevolutionary pattern is that some niche-related traits consistently evolve slower than others, so called niche conservatism. Despite a growing amount of data, the underlying evolutionary processes are not fully understood. I here analyse adaptive radiations in an individual-based eco-evolutionary model. I find a coevolutionary mechanism – evolutionary niche monopolisation – as a possibly important generator of niche conservatism. A single lineage of a radiating clade can monopolise, and later diversify within, a substantial part of the available niche space – much larger than what can be explained by limiting similarity. This leads to niche conservatism, since no species evolves into or out of the monopolised region. The region can in this sense also be described as an adaptive zone. The model indicates that evolutionary niche monopolisation is operative in a large part of parameter space, underlining its possible importance. The mechanism is driven by competitive interactions and differences in niche widths in alternative niche dimensions. I discuss plausible examples of evolutionary niche monopolisation in well-studied natural systems.
|
|
| 430. |
|
|
