Topic
Acaena
About: Acaena is a research topic. Over the lifetime, 37 publications have been published within this topic receiving 648 citations.
Papers
TL;DR: In this article, the authors used historical and recent vegetation map data as well as recent vegetational point data to reconstruct vegetational changes on the island since the early twentieth century, and used logistic regression models with environmental variables or their surrogates to estimate the potential distributions of the worst invaders.
Abstract: : The Juan Fernandez Archipelago, a Chilean national park and biosphere reserve, is 700 km west of continental Chile. Invasive plant species pose major threats to the native, highly endemic vegetation, especially on Robinson Crusoe Island (Mas a Tierra), where there is a permanent settlement. We used historical and recent vegetation map data as well as recent vegetational point data to reconstruct vegetational changes on the island since the early twentieth century. In addition, we used logistic regression models with environmental variables or their surrogates (elevation, solar radiation, topographic similarity index, slope position) to estimate the potential distributions of the worst invaders. Native vegetation has been affected most severely by Acaena argentea, Aristotelia chilensis, Rubus ulmifolius, and Ugni molinae, leading to a significant decrease of endemic plants in the montane forests and native shrublands. The native forest has decreased by approximately one-third. The area affected by Aristotelia chilensis increased from 6.5% to 14% of the total island area. Ugni molinae, once rare, is now abundant (4.6%), as is Acaena (11.9%). Rubus ulmifolius, not present 80 years ago, now covers about 7% of the island's surface. The distributions of all studied species except Rubus ulmifolius are significantly (p 60%) by these plants. Based on the invasion speed of the past 80 years, this would take another 80 years if conservation measures do not succeed.
Resumen: El Archipielago Juan Fernandez, un parque nacional y reserva de la biosfera chileno, esta 700 km al oeste de Chile continental. Plantas invasoras son la mayor amenaza para la vegetacion nativa, altamente endemica, especialmente en la Isla Robinson Crusoe (Mas a Tierra), donde hay un asentamiento permanente. Utilizamos datos historicos y recientes de mapas de vegetacion asi como datos puntuales recientes de vegetacion para reconstruir los cambios de vegetacion en la isla desde el inicio del siglo veinte. Adicionalmente, utilizamos modelos de regresion logistica con variables ambientales o sus sustitutos (elevacion, radiacion solar, indice de similitud topografica, pendiente) para estimar las distribuciones potenciales de los peores invasores. La vegetacion nativa ha sido afectada mas severamente por Acaena argentea, Aristotelia chilensis, Rubus ulmifolius y Ugni molinae, lo que traido una disminucion significativa de plantas endemicas en los bosques montanos y matorrales nativos. El bosque nativo ha disminuido aproximadamente en un tercio. El area afectada por Aristotelia chilensis aumento de 6.5% a 14% del total de la superficie de la isla. Ugni molinae, antes rara, ahora es abundante (4.6%), como lo es Acaena (11.9%). Rubus ulmifolius, ausente hace 80 anos, ahora cubre aproximadamente 7% de la superficie de la isla. Las distribuciones de todas las especies estudiadas excepto Rubus ulmifolius estan significativamente (p 60%) por estas plantas. En base a la velocidad de invasion en los ultimos 80 anos, esto llevaria otros 80 anos si las medidas de conservacion no son exitosas.
75 citations
TL;DR: Seeds of all five species were more tightly attached to socks than trousers, with some seeds still present on socks at 5,000 m, and seeds from Acaena were more likely to be dispersed longer distances.
Abstract: Dispersal is critical step in plant invasions but there is limited information about human-mediated long distance seed dispersal, including in protected areas. Seed dispersal by hikers was quantified for five invasive species (the native Acaena novae-zelandiae, and the non-native weeds Rumex acetosella
Anthoxanthum odoratum, Dactylis glomerata and Festuca rubra) in part of Australia’s Kosciuszko National Park. The proportion of seeds remaining attached to trousers and socks was quantified for replicated short (150 m) and long (5,000 m) distance walks. Functions were fitted for each dataset, and parameters compared among species and between trousers and socks. Dispersal data were combined with attachment rates and the number of people undertaking walks to estimate the total number of weed seeds that might be dispersed. The power exponential function gave the best fit for the majority of datasets, indicating that detachment probability decreased with distance. Seeds of all five species were more tightly attached to socks than trousers, with some seeds still present on socks at 5,000 m. Anthoxanthum and Acaena seeds were more tightly attached to clothing than the other species. Theoretically 1.9 million seeds could be dispersed on socks or 2.4 million seeds on trousers through a season but the actual numbers are likely to be much lower because of limited weed seed at the start of the walks. Because of differences in attachment and detachment rates, seeds from Acaena were more likely to be dispersed longer distances. Long distance human-mediated seed dispersal is potentially a major cause of spread of invasive weeds into protected areas that favours some invasive species over others.
72 citations
TL;DR: Net photosynthesis-leaf temperature relations showed differences in optimum temperature for photosynthesis (Ao.t.) for both species along the altitudinal gradient for two morphologically contrasting species influenced by soil or air temperatures.
Abstract: The effects of temperature on photosynthesis of a rosette plant growing at ground level, Acaena cylindrostachya R. et P., and an herb that grows 20–50 cm above ground level, Senecio formosus H.B.K., were studied along an altitudinal gradient in the Venezuelan Andes. These species were chosen in order to determine – in the field and in the laboratory – how differences in leaf temperature, determined by plant form and microenvironmental conditions, affect their photosynthetic capacity. CO2 assimilation rates (A) for both species decreased with increasing altitude. For Acaena leaves at 2900 m, A reached maximum values above 9 μmol m−2 s−1, nearly twice as high as maximum A found at 3550 m (5.2) or at 4200 m (3.9). For Senecio leaves, maximum rates of CO2 uptake were 7.5, 5.8 and 3.6 μmol m−2 s−1 for plants at 2900, 3550 and 4200 m, respectively. Net photosynthesis-leaf temperature relations showed differences in optimum temperature for photosynthesis (A
o.t.) for both species along the altitudinal gradient. Acaena showed similar A
o.t. for the two lower altitudes, with 19.1°C at 2900 m and 19.6°C at 3550 m, while it increased to 21.7°C at 4200 m. Maximum A for this species at each altitude was similar, between 5.5 and 6.0 μmol m−2 s−1. For the taller Senecio, A
o.t. was more closely related to air temperatures and decreased from 21.7°C at 2900 m, to 19.7°C at 3550 m and 15.5°C at 4200 m. In this species, maximum A was lower with increasing altitude (from 6.0 at 2900 m to 3.5 μmol m−2 s−1 at 4200 m). High temperature compensation points for Acaena were similar at the three altitudes, c. 35°C, but varied in Senecio from 37°C at 2900 m, to 39°C at 3550 m and 28°C at 4200 m. Our results show how photosynthetic characteristics change along the altitudinal gradient for two morphologically contrasting species influenced by soil or air temperatures.
70 citations
TL;DR: Bands of random amplified polymorphic DNA were used as markers to test the hypothesis that the species xMargyracaena skottsbergii, which is endemic to the island of Masatierra in the Juan Fernandez archipelago, represents an intergeneric hybrid between Acaena argentea and Margyricarpus digynus.
Abstract: Bands of random amplified polymorphic DNA (RAPDs) were used as markers to test the hypothesis that the species xMargyracaena skottsbergii, which is endemic to the island of Masatierra in the Juan Fernandez archipelago, represents an intergeneric hybrid between Acaena argentea and Margyricarpus digynus. Thirteen 1 0-mer primers produced 18 consistent species-specific bands forA. argentea and 27 for M. digynus, with all 45 bands present in the presumed hybrid x Margyracaena. A second species of Acaena on Masatierra, A. ovalifolia, has 23 unique amplified bands in all plants examined, and it shares none of these bands with x Margyracaena. The data from RAPDs are concordant with morphology in implicating Acaena argentea rather than A. ovalifolia as one parent of x Margyracaena. RAPDs can provide numerous genetic markers while requiring minimal quantities of DNA, thereby making them attractive for the study of hybridization, particularly in rare plants where DNA amounts may be limiting.
70 citations
TL;DR: All vascular plants recorded from the Auckland Islands are listed, with an indication of the validity of the records and the status and distribution of each taxon.
Abstract: All vascular plants recorded from the Auckland Islands are listed, with an indication of the validity of the records and the status and distribution of each taxon. Those which need further collection are noted. Recent voucher specimens are cited. New records are: Acaena anserinifolia, Blechnum chambersii, Hymeno-phyllum armslrongii, Triglochin striatum. Juncus articulatus. Ranunculus hirtus, Capsella bursa-pastoris, Epilobium alsinoides subsp. atriplicifolium, Haloragis ag-gregata, Galium propinquum, Abrotanella rosulata, Taraxacum magellanicum, Hebe salicifolia, and Limosella lineata. Species not collected for a long time but now confirmed are: Hymenophyllum bivalve, H. dilatatum, H. minimum, Juncus bufonius, Corybas rivularis, Carex ternaria, Holcus lanatus, Puccinellia antipoda, and Trifolium repens.
67 citations
Related Topics (5)
Performance Metrics
| Year | Papers |
|---|---|
| 2019 | 2 |
| 2017 | 1 |
| 2015 | 1 |
| 2012 | 1 |
| 2011 | 3 |
| 2006 | 1 |