| 1. |
- Baskin, CC, et al.
(författare)
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Seed dormancy-breaking and germination requirements of Drosera anglica, an insectivorous species of the Northern Hemisphere
- 2001
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Ingår i: Acta Oecologica. - 1146-609X .- 1873-6238. ; 22:1
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Tidskriftsartikel (refereegranskat)abstract
- Seeds of Drosera anglica collected in Sweden were dormant at maturity in late summer, and dormancy break occurred during cold stratification. Stratified seeds required light for germination, but light had to be given after temperatures were high enough to be favorable for germination. Seeds stratified in darkness at 5/1 ░C and incubated in light at 12/12 h daily temperature regimes of 15/6, 20/10 and 25/15 ░C germinated slower and to a significantly lower percentage at each temperature regime than those stratified in light and incubated in light. Length of the stratification period required before seeds would germinate to high percentages depended on (1) whether seeds were in light or in darkness during stratification and during the subsequent incubation period, and (2) the temperature regime during incubation. Seeds collected in 1999 germinated to 4, 24 and 92 % in light at 15/6, 20/10 and 25/15 ░C, respectively, after 2 weeks of stratification in light. Seeds stratified in light for 18 weeks and incubated in light at 15/6, 20/10 and 25/15 ░C germinated to 87, 95 and 100 %, respectively, while those stratified in darkness for 18 weeks and incubated in light germinated to 6, 82 and 91 %, respectively. Seeds collected from the same site in 1998 and 1999, stratified in light at 5/1 ░C and incubated in light at 15/6 ░C germinated to 22 and 87 %, respectively, indicating year-to-year variation in degree of dormancy. As dormancy break occurred, the minimum temperature for germination decreased. Thus, seed dormancy is broken in nature by cold stratification during winter, and by spring, seeds are capable of germinating at low habitat temperatures, if they are exposed to light. ⌐ 2001 ╔ditions scientifiques et mΘdicales Elsevier SAS.
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| 2. |
- Berg, Henrik
(författare)
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Differential seed dispersal in Oxalis acetosella, a cleistogamous perennial herb
- 2000
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Ingår i: Acta Oecologica. - 1146-609X .- 1873-6238. ; 21:2, s. 109-118
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Tidskriftsartikel (refereegranskat)abstract
- Explosive seed dispersal in the cleistogamous perennial forest herb Oxalis acetosella was studied during two growing seasons, to determine whether seeds derived from chasmogamous (CH) and cleistogamous (CL) flowers differ in dispersal distance. Seed dispersal distance, seed weight, and height of fruits were measured for both flower types, and the effects of phenology and year were also taken into account. The dispersal experiment was performed indoors, using plants transplanted from natural populations to pots. CL seeds were thrown significantly further than were CH seeds, though there was a considerable overlap in dispersal distances. There was also a significant positive relationship between seed weight and dispersal distance. No relationship was found between fruit height and dispersal distance. The results of this study contradict the common view that CL progeny should always be dispersed closer to the mother plant than CH progeny. The ecological implications of the dispersal difference are unclear, especially since it is uncertain whether CH seeds are generally outcrossed or not. Variation in dispersal distance in O. acetosella seems to be mainly dependent on a combination of reproductive mode and variation in seed weight.
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| 3. |
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| 4. |
- Acharya, Kamal Prasad, et al.
(författare)
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Latitudinal variation of life-history traits of an exotic and a native impatiens species in Europe
- 2017
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Ingår i: Acta Oecologica. - : Elsevier BV. - 1146-609X .- 1873-6238. ; 81, s. 40-47
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Tidskriftsartikel (refereegranskat)abstract
- Understanding the responses of invasive and native populations to environmental change is crucial for reliable predictions of invasions in the face of global change. While comparisons of responses across invasive species with different life histories have been performed before, comparing functional traits of congeneric native and invasive species may help to reveal driving factors associated with invasion. Here we compared morphological functional trait patterns of an invasive species (Impatiens parviflora) with its congeneric native species (I. noli-tangere) along an approximately 1600 km European latitudinal gradient from France (49 degrees 34'N) to Norway (63 degrees 40'N). Soil nitrogen was recorded during six weeks of the growing season, and light, soil moisture, and nutrient availability were estimated for each sampled population using community weighted means of indicator values for co-occurring species. Temperature data were gathered from nearby weather stations. Both the native and invasive species are taller at higher latitudes and this response is strongest in the invasive species. Seed mass and number of seeds per capsule increase in I. noli-tangere but decrease in I. parviflora towards higher latitudes. Surprisingly, plant height in the invasive I. parviflora decreases with increasing soil nitrogen availability. The latitudinal pattern in seed mass is positively related to temperature in I. noli-tangere and negatively in I. parviflora. Leaf area of both species decreases with increasing Ellenberg indicator values for nitrogen and light but increases with increasing soil moisture. Soil nitrogen concentrations and Ellenberg indicator values for nitrogen have significant positive (I. nolitangere) and negative (I. parviflora) effects on the number of seeds per capsule. Our results show that the native I. noli-tangere has efficient reproduction at its range edge while the invasive I. parviflora shows a marked decrease in seed size and seed number per capsule. These patterns are unrelated to the growth and obtained size of the plants: even low soil nitrogen availability in the north seemed not to limit plant growth and size. Our results suggest that the invasive I. parviflora tends to become more invasive at lower latitudes by producing heavier seeds and more seeds per capsule.
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| 5. |
- Bienau, Miriam J., et al.
(författare)
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Synchronous flowering despite differences in snowmelt timing among habitats of Empetrum hermaphroditum
- 2015
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Ingår i: Acta Oecologica. - : Elsevier BV. - 1146-609X .- 1873-6238. ; 69, s. 129-136
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Tidskriftsartikel (refereegranskat)abstract
- The topography within arctic-alpine landscapes is very heterogeneous, resulting in diverse snow distribution patterns, with different snowmelt timing in spring. This may influence the phenological development of arctic and alpine plant species and asynchronous flowering may promote adaptation of plants to their local environments. We studied how flowering phenology of the dominant dwarf shrub Empetrum hermaphroditum varied among three habitats (exposed ridges, sheltered depressions and birch forest) differing in winter snow depth and thus snowmelt timing in spring, and whether the observed patterns were consistent across three different study areas. Despite significant differences in snowmelt timing between habitats, full flowering of E. hermaphroditum was nearly synchronous between the habitats, and implies a high flowering overlap. Our data show that exposed ridges, which had a long lag phase between snowmelt and flowering, experienced different temperature and light conditions than the two late melting habitats between snowmelt and flowering. Our study demonstrates that small scale variation seems matter less to flowering of Empetrum than interannual differences in snowmelt timing.
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| 6. |
- Blixt, Torbjörn, et al.
(författare)
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Clear-cuts in production forests: From matrix to neo-habitat forbutterflies
- 2015
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Ingår i: Acta Oecologica. - : Elsevier. - 1146-609X .- 1873-6238. ; 69, s. 71-77
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Tidskriftsartikel (refereegranskat)abstract
- Butterfly conservation in Europe is mainly focused on well-defined grassland habitat patches. Such anapproach ignores the impact of the surrounding landscape, which may contain complementary resourcesand facilitate dispersal. Here, we investigated butterfly species richness and abundance in a habitatnormally regarded as unsuitable matrix: production forestry clear-cuts. Butterflies were recorded in 48clear-cuts in southern Sweden differing with regards to the time since clear-cutting and land-use history(meadow or forest based on historical maps from the 1870s). All clear-cuts had been managed as productionforests for at least 80e120 years. A total of 39 species were found in clear-cuts of both land-usehistories, but clear-cuts with a history as meadow had on average 34% higher species richness and 19%higher abundance than did clear-cuts with a history as forest. No effect of the time since clear-cuttingwas found, irrespective of land-use history, which was likely due to the narrow timespan sampled (<8years). The absence of temporal effect suggests that clear-cuts may provide butterflies with valuableresources for 10e15 years. Assuming a 100 year forest rotational cycle, this means that 10e15% of thetotal forested area are made up by clear-cuts valuable to butterflies, which corresponds to an area aboutfour times as large as that of species-rich semi-natural grasslands. The study illustrates the importance ofconsidering land-use legacies in ecological research and question the landscape-ecological view thatclear-cuts make up an unsuitable matrix for butterflies. Moreover, forest conservation management withspecial attention to land-use history may increase the quality of the landscape, thus facilitating butterflymetapopulation persistence. Given their large area and assets of nectar and host plant resources, clearcutsmust be considered as a butterfly habitat in its own right. Being a man-made environment withshort history, we might call it a neo-habitat.
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| 9. |
- Haussmann, Natalie, et al.
(författare)
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Contrasting nurse plants and nurse rocks The spatial distribution of seedlings of two sub-Antarctic species : The spatial distribution of seedlings of two sub-Antarctic species
- 2010
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Ingår i: Acta Oecologica. - : Elsevier BV. - 1146-609X .- 1873-6238. ; 36:3, s. 299-305
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Tidskriftsartikel (refereegranskat)abstract
- Positive plant interactions, such as those associated with nurse plants, have been suggested to dominate over negative interactions in environments with high abiotic stress. Here we demonstrate that the sub-Antarctic cushion plant species, Azorella selago (Apiaceae), positively affects the distribution of both its own seedlings and those of the perennial grass, Agrostis magellanica (Poaceae). As a result of the light weight and small size of seeds of both species, coupled with strong winds experienced in the study area, we consider it unlikely that these patterns are the result of very localized seed dispersal from the study cushions themselves. Instead, we suggest that both cushions and rocks act as seed traps, trapping seeds dispersed by wind, runoff and/or downslope sediment transport through frost creep. In addition, increased A. selago seedling numbers around cushions, but not around rocks, suggest that cushions provide a biological nurse effect, such as improving soil nutrient status or providing mychorrizae, to seedlings of their own kind.
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| 10. |
- Hedberg, H. Roberta, et al.
(författare)
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A new player in the Panamanian fig tree – fig wasp mutualism : a study on the effect of gall midges on Ficus citrifolia
- 2024
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Ingår i: Acta Oecologica. - : Elsevier. - 1146-609X .- 1873-6238. ; 122
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Tidskriftsartikel (refereegranskat)abstract
- The mutualism between the fig tree and the pollinating fig wasps is a keystone interaction in tropical forests. However, many antagonistic interactions also occur in the system, taking advantage of the fig trees and the pollinator. One such example is an antagonistic gall midge (Cecidomyiidae) that develops inside figs. Gall midges inside figs have been documented in a few Ficus species around the world, but to our knowledge they have not previously been observed in Panama. In this study the newly observed Panamanian fig gall midge is documented, together with its parasitoid wasp. The fig gall midge was only found in Ficus citrifolia figs. We investigated the effect of fig gall midge presence on the number of seeds and the number of pollinating wasps (Pegoscapus tonduzi) in a fig and aimed to identify the species based on morphology and barcoding of the COI region. We found that the fig gall midge had no, or a negligible effect, on the reproduction of the fig tree - fig wasp mutualism. The fig gall midge most likely belongs to the genus Ficiomyia, close to Ficiomyia perarticulata. The parasitoid belongs to the genus Physothorax, close to Physothorax russelli. This study suggests that the potentially newly arrived fig gall midge currently has no major effect on the fig tree - fig wasp mutualism. However, should infestation rates increase, it is likely that the fig gall midge would affect the mutualism negatively as it has in other parts of the world. More studies on the fig gall midge species distributions in this region would be valuable and would connect these newly observed species to a larger community, adding yet another species to this complex but classic example of a mutualism.
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