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A second species of Cylindropuntia (Engelm.) F.M.Knuth (Cactaceae), C. imbricata (Haw.) F.M.Knuth, naturalised in Zimbabwe
Abstract
Cylindropuntia imbricata (Haw.) F.M.Knuth (Cactaceae) is recorded as having become naturalised in south-central region of Zimbabwe. A description and illustrations of the species in Zimbabwe are provided. A key, based on vegetative characters which distinguish C. imbricata, C. fulgida (Engelm.) F.M.Knuth, C. leptocaulis (DC.) F.M.Knuth, C. pallida (Rose) F.M.Knuth and C. spinosior (Engelm.) F.M.Knuth, the five commonly grown or naturalised species in southern Africa, is included.
... Biological sciences, biodiversity Specific subject area Botany, conservation, alien plants, invasive species Type of data Tables, figures, database, map How data were acquired Data set was generated from herbarium specimens, field work and alien plant surveys conducted throughout the country aimed at establishing the spatial distribution of alien species in Zimbabwe, their distributional range, habitats and abundance [1][2][3][4][5][6][7][8][9] Data format Raw data in Excel file, analyzed Description of data collection This dataset has a list of alien species occurring in Zimbabwe was compiled based on herbarium records, field work and alien plant surveys conducted throughout the country [1][2][3][4][5][6][7][8][9] . All alien plant species ever recorded in Zimbabwe, whether the introduction was accidental or intentional, as escapes from cultivation or naturalized at least once in the wild were included in this study. ...
... Biological sciences, biodiversity Specific subject area Botany, conservation, alien plants, invasive species Type of data Tables, figures, database, map How data were acquired Data set was generated from herbarium specimens, field work and alien plant surveys conducted throughout the country aimed at establishing the spatial distribution of alien species in Zimbabwe, their distributional range, habitats and abundance [1][2][3][4][5][6][7][8][9] Data format Raw data in Excel file, analyzed Description of data collection This dataset has a list of alien species occurring in Zimbabwe was compiled based on herbarium records, field work and alien plant surveys conducted throughout the country [1][2][3][4][5][6][7][8][9] . All alien plant species ever recorded in Zimbabwe, whether the introduction was accidental or intentional, as escapes from cultivation or naturalized at least once in the wild were included in this study. ...
... Similarly, the same authors defined a naturalized species as an alien species that reproduce consistently without direct human intervention. Each species was assessed to ascertain its current residential status in the country through herbarium studies, field work and alien plant surveys conducted throughout the country aimed at establishing the spatial distribution of alien species in Zimbabwe, their distributional range, habitats and abundance [1][2][3][4][5][6][7][8][9] . The processed data divided alien species recorded in Zimbabwe into three main categories following methodologies to generate the level of naturalization [10] : ...
This data is based on herbarium specimens housed by the National Herbarium (SRGH) in Harare, Zimbabwe. Comprehensive data is provided for 1487 alien plant taxa growing in Zimbabwe. This checklist has 1027 taxa that were confined to cultivation, while 63 and 397 taxa were recorded as casuals and naturalized, respectively. The alien flora is rich in Fabaceae sensu lato (13.7%), Asteraceae and Poaceae (7.3% each) plant families. The dataset presented in this article provide important baseline information on alien plant species in Zimbabwe required to monitor status of such species within the country, particularly in protected areas. Therefore, this dataset has potential to serve as a foundation for future research on plant invasions in Zimbabwe.
There is lack of historical information on dates and modes of introduction as well as colonization and invasion processes of exotic plants in Zimbabwe. Cylindropuntia fulgida (Engelm.) F.M.Knuth var. fulgida (chain-fruit cholla, family Cactaceae), a native of arid desert of the Guaymas region of Sonora in northwestern Mexico is here recorded as having become naturalised and invasive in south-western areas of Zimbabwe. Notes on residence status, ecology and habitat of C. fulgida var. fulgida in south-western Zimbabwe are provided. A description and dichotomous key that can be used to distinguish it from the closely related C. imbricata (Haw.) F.M.Knuth is provided. The latter species is commonly grown in Zimbabwe while C. fulgida var. fulgida is spreading and has become firmly established as part of the introduced flora of Zimbabwe.
Rosea cactus (Opuntia rosea DC.) is a name that has long been used for a densely spiny cactus invading dry savanna in South Africa. Recent efforts to improve biological control of this invasive species using cochineal (Dactylopius tomentosus (Lamarck)) led to the discovery that the plant species had been misidentified. A biotype of cochineal collected from rosea cactus in Mexico failed to develop on ‘rosea cactus’ in South Africa. This pointed to the incorrect identification of rosea cactus in South Africa and led to an investigation of other similar cacti in Mexico. O. fulgida (chainfruit cholla) is similar in appearance to rosea cactus but has characteristic chains of fruits that persist for years. In South Africa these chains of fruits had not been observed because chemical and mechanical control since the 1960's had prevented the plants from developing to maturity.-In an isolated infestation bordering on Zimbabwe the characteristic chains of fruit were seen for the first time. A comparison of the morphological characteristics of both species led to the conclusion that in South Africa, O. rosea had been misidentified and is in fact O. fulgida.
The number of studies dealing with plant invasions is increasing rapidly, but the accumulating body of knowledge has unfortunately also spawned increasing confusion about terminology. Invasions are a global phenomenon and comparison of geographically distant regions and their introduced biota is a crucially important methodological approach for elucidation of the determinants of invasiveness and invasibility. Comparative studies of alien floras provide substantial new insights to our understanding of general patterns of plant invasions. Such studies, using information in previously published floras and checklists, are fundamentally dependent on the quality of the assessment of particular species with respect to their taxonomic identity, time of immigration and invasion status. Three crucial decisions should be made when defining the status of a plant species in a given region: (1) whether the taxon is native or alien to that region (origin status); (2) what is its position in the invasion process, i.e., when was it introduced (residence status); and (3) what is the degree of its naturalization and possible invasion (invasion status). Standard floras differ hugely in their treatment of non-native species and those with appropriate categorization of alien species according to their status are rather rare. The present paper suggests definitions of terms associated with plant invasions and places these into the context of floras. Recommendations are outlined on how to deal with the issue of plant invasions in standard floras with the aim of contributing to a better understanding between taxonomists and ecologists and allowing more detailed comparative analyses of alien floras of various regions of the world.
Much confusion exists in the English-language literature on plant invasions concerning the terms ‘naturalized’ and ‘invasive’ and their associated concepts. Several authors have used these terms in proposing schemes for conceptualizing the sequence of events from introduction to invasion, but often imprecisely, erroneously or in contradictory ways. This greatly complicates the formulation of robust generalizations in invasion ecology.
Based on an extensive and critical survey of the literature we defined a minimum set of key terms related to a graphic scheme which conceptualizes the naturalization/invasion process. Introduction means that the plant (or its propagule) has been transported by humans across a major geographical barrier. Naturalization starts when abiotic and biotic barriers to survival are surmounted and when various barriers to regular reproduction are overcome. Invasion further requires that introduced plants produce reproductive offspring in areas distant from sites of introduction (approximate scales: > 100 m over < 50 years for taxa spreading by seeds and other propagules; > 6 m/3 years for taxa spreading by roots, rhizomes, stolons or creeping stems). Taxa that can cope with the abiotic environment and biota in the general area may invade disturbed, seminatural communities. Invasion of successionally mature, undisturbed communities usually requires that the alien taxon overcomes a different category of barriers.
We propose that the term ‘invasive’ should be used without any inference to environmental or economic impact. Terms like ‘pests’ and ‘weeds’ are suitable labels for the 50–80% of invaders that have harmful effects. About 10% of invasive plants that change the character, condition, form, or nature of ecosystems over substantial areas may be termed ‘transformers’.
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