Tag: invasive species
Prosopis juliflora invasion and rural livelihoods in the Lake Baringo area of Kenya
Global concern about deforestation caused by fuelwood shortages prompted the introduction of Prosopis juliflora to many tropical areas in the 1970s and 1980s. pjuliflora is a hardy nitrogen-fixing tree that is now recognised as one of the world’s most invasive alien species. The introduction and subsequent invasion of pjuliflora in the Lake Baringo area of Kenya has attracted national media attention and contradictory responses from responsible agencies. This paper presents an assessment of the livelihood effects, costs of control and local perceptions on pjuliflora of rural residents in the Lake Baringo area. Unlike some other parts of the world where it had been introduced, few of the potential benefits of pjuliflora have been captured and very few people realise the net benefits in places where the invasion is most advanced. Strong local support for eradication and replacement appears to be well justified. Sustainable utilisation will require considerable investment and institutional innovation.
Biodiversity and Invasive species assessment information dissemination: Workshop Report
Insufficient Evidence of Jatropha curcas L. Invasiveness: Experimental Observations in Burkina Faso, West Africa
Biofuel plants such as Jatropha curcas L. have potential to support the livelihoods of rural communities and contribute to sustainable rural development in Africa, if risks and uncertainties are minimized. Yet, recent papers have warned of the risk of biological invasions in such tropical regions as a consequence of the introduction of exotic biofuel crops. We investigated the seed dispersal risk and invasiveness potential of both J. curcas monoculture plantations and live fences into adjacent cultivated and uncultivated land use systems in Sissili province, Burkina Faso. Invasiveness potential was assessed through (i) detecting evidence of natural regeneration in perimeters around J. curcas plantations and live fences, (ii) assessing seed dispersal mechanisms, and (iii) assessing seedling establishment potential through in situ direct seed sowing. Spontaneous regeneration around the plantation perimeters of the three sites was very low. Individual seedling density around J. curcas live fences was less than 0.01 m-2 in all sites. Seventy percent of the seedlings were found close to the live fence and most of them derived from the same year (96 %), which indicates low seed-bank longevity and seedling survival. J. curcas can be dispersed by small mammals and arthropods, particularly rodents and ants. In some sites, such as in Onliassan, high secondary seed dispersal by animals (up to 98 %) was recorded. There were highly significant differences in germination rates between seeds at the soil surface (11 %) and those buried artificially at 1-2-cm depth (64 %). In conclusion, we failed to find convincing evidence of the spreading of J. curcas or any significant impact on the surrounding environment.
Living With Hyraxes: Biogeography and Comparative Ecology of West African Fornasinius Beetles
Among the flower beetles (Scarabaeidae, Cetoniinae), the Goliathini comprise several genera of medium- and large-sized beetles widely distributed in sub-Saharan Africa. In this tribe, the genus Fornasinius Bertoloni, 1853, includes two species found in West Africa: F. higginsi (Westwood) and F. klingbeili Zöller, Fiebig,and Schulze. In this study, we present new data on the comparative ecology and biogeography of these two species, including sex ratio, population structure by size, monthly activity patterns and habitat features at two different spatial scales. These observations were conducted, mostly opportunistically, over a 20-year period in Cote d’Ivoire, Ghana and Togo. Both species exhibited similar overall population structure and morphometrics. They were characterised by a male-skewed adult sex ratio (with possible bias), male-larger sexual size dimorphism and consistent population structure by size; the two species are seemingly parapatric (with the potential contact zone being separated in eastern Ghana by the Volta River and Volta Lake). Both are primarily found in the vicinity of trees that contained middens of hyraxes, such as Dendrohyrax dorsalis (F. higginsi), Dendrohyrax interfluvialis (F. klingbeili) and Procavia capensis (F. klingbeili). F. higginsi has been primarily observed in forest habitat, while F. klingbeili was found in both forests and Guinea savannahs. Occurrence sites of F. higginsi were predominantly characterised by higher tree cover, less bare areas and built-up zones. Although these beetles may be locally abundant within hyrax middens, they typically occur in only a relatively small number of sites within their preferred habitat. Monthly activity patterns differed between the two species. Although adults of both species were observed throughout the year, sightings of F. higginsi were more common during the wet season, whereas F. klingbeili sightings were more frequent in the dry season. The observed differences in monthly activity patterns between these ecologically and morphologically similar species may help to minimise interspecific competition in potential—yet unknown—sites of syntopy. Although some Fornasinius populations might be locally threatened by deforestation or overhunting of hyraxes, the careful management of hyrax populations should adequately ensure the conservation of these two beetle species.
Native diversity buffers against severity of non-native tree invasions
Determining the drivers of non-native plant invasions is critical for managing native ecosystems and limiting the spread of invasive species. Tree invasions in particular have been relatively overlooked, even though they have the potential to transform ecosystems and economies. Here, leveraging global tree databases, we explore how the phylogenetic and functional diversity of native tree communities, human pressure and the environment influence the establishment of non-native tree species and the subsequent invasion severity. We find that anthropogenic factors are key to predicting whether a location is invaded, but that invasion severity is underpinned by native diversity, with higher diversity predicting lower invasion severity. Temperature and precipitation emerge as strong predictors of invasion strategy, with non-native species invading successfully when they are similar to the native community in cold or dry extremes. Yet, despite the influence of these ecological forces in determining invasion strategy, we find evidence that these patterns can be obscured by human activity, with lower ecological signal in areas with higher proximity to shipping ports. Our global perspective of non-native tree invasion highlights that human drivers influence non-native tree presence, and that native phylogenetic and functional diversity have a critical role in the establishment and spread of subsequent invasions.
Negative impacts of dominance on bee communities: Does the influence of invasive honey bees differ from native bees?
Invasive species can reach high abundances and dominate native environments. One of the most impressive examples of ecological invasions is the spread of the African subspecies of the honey bee throughout the Americas, starting from its introduction in a single locality in Brazil. The invasive honey bee is expected to more negatively impact bee community abundance and diversity than native dominant species, but this has not been tested previously. We developed a comprehensive and systematic bee sampling scheme, using a protocol deploying 11,520 pan traps across regions and crops for three years in Brazil. We found that invasive honey bees are now the single most dominant bee species. Such dominance has not only negative consequences for abundance and species richness of native bees but also for overall bee abundance (i.e., strong “numerical” effects of honey bees). Contrary to expectations, honey bees did not have stronger negative impacts than other native bees achieving similar levels of dominance (i.e., lack of negative “identity” effects of honey bees). These effects were markedly consistent across crop species, seasons and years, and were independent from land-use effects. Dominance could be a proxy of bee community degradation and more generally of the severity of ecological invasions.
Phenotypic variability and genetic diversity of phragmites Australis in Quebec and Kashmir reveal contrasting population structure
The origin of differences in traits influencing competitive success between invasive and native wild populations of alien species is subject of debate. Herbarium-based information sources from 2005 onwards about nativity and distributional range of Phragmites australis were used to survey putative native populations of the species in Quebec, and chloroplast DNA (cpDNA) PCRRFLP analyses identified only one native population, whereas the same analyses revealed that the Kashmir populations are invasive. We compared the native population of P. australis in Quebec (QN), ten populations invasive to Quebec (QE), and five populations invasive in Kashmir, India (KE) using morphometric traits. Using nine cpDNA microsatellite loci, we also compared nine KE populations, ten QE populations, and the QN population. Phenotypic variation was observed among and within populations. Only dry mass of flowers varied across regions. Characterization of morphotypes defined three distinct haplotypes. A bimodal distribution of stem diameter (SD), internode length (IL), leaf length (LL), and leaf width (LW) suggests that a major gene may control growth traits or occurrence of co-selection. High genetic differentiation was observed between populations (RST = 0.353) and haplotypes (RST = 0.133 to 0.418), indicating limited gene flow and probable local adaptation. Principal coordinates analysis and the neighbor-joining phylogenetic tree clearly distinguished the three haplotypes. Among-populations phenotypic difference (PST) was lower than overall RST for plant height, SD, and fresh and dry mass of flowers and seeds, whereas PST estimates for LL and LW exceeded among-populations RST, suggesting divergent selection, while local adaptation might have occurred in IL, LL, and flower masses. Genetic drift probably influenced among-populations IL differences. © 2020 by the authors. Licensee MDPI, Basel, Switzerland.
Relationship between Prosopis juliflora invasion and livelihood diversification in the South Afar region, Northeast Ethiopia
Phenology of the Alien Invasive Plant Species Prosopis juliflora in Arid and Semi-Arid Areas in Response to Climate Variability and Some Perspectives for Its Control in Ethiopia
This study aims to (i) evaluate the phenology of Prosopis juliflora (Prosopis), (ii) investigate the effects of climate variability (temperature and precipitation) on the phenology of Prosopis, and (iii) assess the critical months of seed dispersal for the species management. Monthly data for phenology events: leafing, flowering, green and mature pods were collected from 8 stems of Prosopis trees at each of two localities in Ethiopia during 2016/2017. In Amibara district we found that relative abundances of green leaves, flowering, green pods, and mature pods were 91, 15, 9, and 2% in order. However, these were less than by 8, 53, 91, and 90%, respectively in Awash Fenatle district. The lowest proportions of mature and green pods were recorded in the dry season and the highest in the spring season. We recorded the highest and lowest relative abundances of flowering between November and December, and January and February, respectively. In this study, both temperature (F = 2.01, P = 0.04) and precipitation (F = 2.85, P = 0.01) had shown significant effects on the relative abundances of green leaves but insignificant effects on other phenology stages. Higher green leaf abundances were recorded during high rainfall, whereas lower abundances of leaves were recorded in high temperatures. But, the relative abundances of Prosopis leaves showed inconsistent with the variations of precipitation. Thus, awareness creation for stake holders about the phenology calendar of Prosopis should be given to abandon the invasiveness of the species towards the prime grazing lands in the region. © 2020 BioOne. All rights reserved.