Insect rate-temperature relationships: Environmental variation and the metabolic theory of ecology

Much of the recent discussion concerning the form and underlying mechanistic basis of metabolic rate–temperature and development rate–temperature relationships has been recipitated by the development of the metabolic theory of ecology (MTE). Empirical tests of the theory’s fundamental equation are an essential component of establishing its validity. Here, we test the temperature component of the fundamental equation of the MTE as it applies to metabolic rate and development rate, using insects as model organisms. Specifically, we test (i) whether mean activation energies, E, approximate the 0.65 eV value proposed by the proponents of the MTE and whether the range of values is tightly constrained between 0.6 and 0.7 eV, as they have argued; (ii) whether phylogenetic signal is apparent in the rate-temperature relationships; (iii) whether the slopes of the rate-temperature relationships show consistent, directional variation associated with environmental variables; and (iv) whether intra- and interspecific rate-temperature relationships differ significantly. Because the majority of activation energy values fell outside the predicted range and rate-temperature relationships showed consistent directional variation correlated with large-scale climatic variation, we conclude that data from insects provide only limited support for the MTE. In consequence, we consider alternative explanations for variation in rate-temperature relationships

Emerging ornamental plant invaders in Urban Areas – Centranthus ruber in Cape Town, South Africa as a case study

Plant species that receive significant human introduction effort and assistance generally are the most problematic invaders. Despite this, invasive ornamental species in urban settings have received relatively little attention if not invading natural areas. Here we consider Centranthus ruber in an urban setting in South Africa as a case study and explore when emerging invaders are able to cross the urban–wildland interface and what hinders early eradication in urban environments. Centranthus ruber was introduced into Cape Town, South Africa, more than a century ago as a garden ornamental, but until recently was not considered invasive. We determine the current and potential future distribution in South Africa, evaluate current management activities, and provide recommendations for control and legislation. By August 2013, we had found 64 populations, of which 31 were casual, 27 naturalized, and 6 invasive. This increased to more than 530 identified populations by the end of 2015, due to both spread and increased awareness. Centranthus ruber can invade near-pristine areas, with one population found in natural vegetation in the Table Mountain National Park. However, with only one slowly spreading population, the threat might be limited. We found no difference in plant mortality between chemical and mechanical clearing, but with mechanical clearing stimulating the soil seedbank, we recommend chemical methods. Using a species distribution model, we found large parts of South Africa, including the southwestern Cape where we conducted our surveys, to be climatically suitable for this species. Consequently, the category 1b regional listing in NEM:BA in the Western Cape is justified, but a listing in other parts of the country also might be appropriate. Based on our findings, we suggest that the extirpation of C. ruber in South Africa is possible, but without buy-in from residents in urban environments, reinvasion will render this impossible. This study stresses the importance of managing and legislating emerging invaders at the urban–wildland interface and the monitoring of common ornamental species with invasive traits

Aliens in the nursery: assessing the attitudes of nursery managers to invasive species regulations

The horticultural industry is recognised as a major pathway for the introduction and spread of invasive alien plants (IAPs). The Conservation of Agricultural Resources Act (CARA) of 1983 (Act No. 43 of 1983) listed and categorised invasive species with an aim to curb their spread. The more recently enacted Alien and Invasive Species Regulations under South Africa’s National Environmental Management: Biodiversity Act (NEMBA) are intended, in part, to improve controls on the horticultural industry’s role in the spread of IAPs. In order to assess, and enhance, the likely effectiveness of NEMBA, it is important to build an understanding of stakeholders’ awareness and attitudes towards the control of IAPs and associated regulatory policies. A two-pronged approach—involving nursery manager interviews (n = 30) and plant stock audit assessments (n = 41)—was used to gauge the awareness, compliance and attitudes of nursery managers towards both the CARA and NEMBA invasive species regulations. Less than ten percent of audited nurseries were fully compliant with the NEMBA regulations, and over 50% were stocking IAPs that have been regulated for at least 13 years under CARA. This is despite high levels of awareness (70%) about the CARA regulations reported in the interviews. The majority (73.5%) of IAP species stocked in nurseries were NEMBA category 1b invaders such as Nerium oleander and Canna indica. These are widespread and well-established invaders that require compulsory control under NEMBA. Half of the managers were not aware that the NEMBA regulations had been promulgated, but most respondents nevertheless reported being enthusiastic about compliance. Several factors were quoted as constraints on compliance by the industry. These included a perceived lack of enforcement, weak communication from government, and the lack of inclusion of the industry in the regulatory process. Suggested interventions that could enhance the impact of IAP regulations will involve improving the user-friendliness of the regulations, and supplementing the current top-down approach to regulation with an inclusive partner-centred approach

Climate change and alien species in South Africa.

South Africa has a long history of human-mediated introductions of species from all major taxonomic groups. Close to 9000 alien terrestrial plant species have been introduced, and all of the country’s biomes have already been invaded. Invasive species are threatening the country’s ecosystems in numerous ways, but the effect of climate change on these invasions is predicted to be complex and cascading and remains poorly understood. The relationship between climate and invasive species biology is well established, and there is no question that climate change will influence the ecology of invasive species significantly. If left un - managed, these effects are expected to increase substantially. Besides terrestrial plants, numerous animals have also invaded the country’s landscapes. South Africa’s freshwater ecosystems have been invaded by both alien as well as extralimital introductions (indigenous species outside their historical extent of occurrence). The status of invasion in the marine environment remains poorly studied, and knowledge of the status of invasions and predictions regarding the impacts of climate change remain largely speculative. This chapter highlights the current status of invasions in South Africa and discusses some of the direct and indirect effects climate change is likely to have on these invasions

How do invasive species travel to and through urban environments?

Globalisation has resulted in the movement of organisms outside their natural range, often with negative ecological and economic consequences. As cities are hubs of anthropogenic activities, with both highly transformed and disturbed environments, these areas are often the first point of entry for alien species. We compiled a global database of cities with more than one million inhabitants that data had on alien species occurrence. We then identified the most prominent pathways of introduction and vectors of spread of alien species in these cities. Most species were intentionally introduced to cities and were released or escaped from confinement. The majority of alien species then spread within cities through natural means (primarily unaided dispersal). Pathway prominence varied across the taxonomic groups of alien species: the most prominent pathway for plants and vertebrates was the escape pathway; for invertebrates the stowaway and contaminant pathways were most likely to facilitate introductions. For some organisms, pathway prominence varied with the geographical and climatic characteristics of the city. The characteristics of the cities also influenced the prominence of vectors of spread for alien species. Preventing the natural spread of alien species within cities, and into adjacent natural environments will be, at best, difficult. To prevent invasions, both the intentional and unintentional introduction of potentially harmful alien species to cities must be prevented. The pathways of introduction and vectors of spread identified here should be prioritised for management

How do invasive species travel to and through urban environments?

Globalisation has resulted in the movement of organisms outside their natural range, often with negative ecological and economic consequences. As cities are hubs of anthropogenic activities, with both highly transformed and disturbed environments, these areas are often the first point of entry for alien species. We compiled a global database of cities with more than one million inhabitants that data had on alien species occurrence. We then identified the most prominent pathways of introduction and vectors of spread of alien species in these cities. Most species were intentionally introduced to cities and were released or escaped from confinement. The majority of alien species then spread within cities through natural means (primarily unaided dispersal). Pathway prominence varied across the taxonomic groups of alien species: the most prominent pathway for plants and vertebrates was the escape pathway; for invertebrates the stowaway and contaminant pathways were most likely to facilitate introductions. For some organisms, pathway prominence varied with the geographical and climatic characteristics of the city. The characteristics of the cities also influenced the prominence of vectors of spread for alien species. Preventing the natural spread of alien species within cities, and into adjacent natural environments will be, at best, difficult. To prevent invasions, both the intentional and unintentional introduction of potentially harmful alien species to cities must be prevented. The pathways of introduction and vectors of spread identified here should be prioritised for management

How do invasive species travel to and through urban environments?

Globalisation has resulted in the movement of organisms outside their natural range, often with negative ecological and economic consequences. As cities are hubs of anthropogenic activities, with both highly transformed and disturbed environments, these areas are often the first point of entry for alien species. We compiled a global database of cities with more than one million inhabitants that data had on alien species occurrence. We then identified the most prominent pathways of introduction and vectors of spread of alien species in these cities. Most species were intentionally introduced to cities and were released or escaped from confinement. The majority of alien species then spread within cities through natural means (primarily unaided dispersal). Pathway prominence varied across the taxonomic groups of alien species: the most prominent pathway for plants and vertebrates was the escape pathway; for invertebrates the stowaway and contaminant pathways were most likely to facilitate introductions. For some organisms, pathway prominence varied with the geographical and climatic characteristics of the city. The characteristics of the cities also influenced the prominence of vectors of spread for alien species. Preventing the natural spread of alien species within cities, and into adjacent natural environments will be, at best, difficult. To prevent invasions, both the intentional and unintentional introduction of potentially harmful alien species to cities must be prevented. The pathways of introduction and vectors of spread identified here should be prioritised for management