- Cape Town, Western Cape, South Africa
- Dr. John Measey is a Chief Researcher at the Centre for Invasion Biology (C·I·B) based in the Department of Botany an... moreDr. John Measey is a Chief Researcher at the Centre for Invasion Biology (C·I·B) based in the Department of Botany and Zoology at Stellenbosch University. His research centres on biological invasions and other ecological investigations incorporating a wide range of techniques to address hypotheses in evolution, conservation and population biology.edit
Angola has experienced an incredible increase of the knowledge of its herpetofauna over the past decade. However, accurate biodiversity inventories remain deficient for certain regions of particular conservation interest. We therefore... more
Angola has experienced an incredible increase of the knowledge of its herpetofauna over the past decade. However, accurate biodiversity inventories remain deficient for certain regions of particular conservation interest. We therefore provide an updated checklist of Iona National Park’s herpetofauna, with 75 recorded species, including five amphibians and 70 reptiles, 40 of these recorded for the first time in Iona National Park. These species comprise ~80% of the reptile diversity of Namibe Province. Therefore, this work recognises Iona National Park as the most reptile-diverse protected area in Angola and is potentially one of the richest in southern Africa. Consequently, this work enhances the importance of specific conservation plans in the area and the need for further investigation into the hidden biodiversity of this region.
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Invasive alien species (IAS) are a growing threat globally and cause a variety of ecological, economic, and social impacts. People can introduce IAS and facilitate their spread, and can also implement, support, or oppose their management.... more
Invasive alien species (IAS) are a growing threat globally and cause a variety of ecological, economic, and social impacts. People can introduce IAS and facilitate their spread, and can also implement, support, or oppose their management. Understanding local knowledge, awareness, and perceptions are therefore crucial if management and policy are to be effective. We administered questionnaires to members of the public in eight small towns along the Berg River Catchment in the biodiverse fynbos biome of South Africa. We aimed to assess: (1) awareness of IAS by the general public, (2) local perceptions of the impacts associated with IAS, (3) whether awareness of IAS is correlated with demographic covariates and IAS density, and (4) people’s willingness to detect, report, and support IAS management. Overall, 262 respondents participated in the survey. Most respondents (65%) did not know what IAS are, and 10% were unsure. Many respondents also perceived IAS as beneficial. Using a logisti...
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Allotetraploid genomes have two distinct genomic components called subgenomes that are derived from separate diploid ancestral species. Many genomic characteristics such as gene function, expression, recombination, and transposable... more
Allotetraploid genomes have two distinct genomic components called subgenomes that are derived from separate diploid ancestral species. Many genomic characteristics such as gene function, expression, recombination, and transposable element mobility may differ significantly between subgenomes. To explore the possibility that subgenome population structure and gene flow may differ as well, we examined genetic variation in an allotetraploid frog—the African clawed frog (Xenopus laevis)—over the dynamic and varied habitat of its native range in southern Africa. Using reduced representation genome sequences from 91 samples from 12 localities, we found no strong evidence that population structure and gene flow differed substantially by subgenome. We then compared patterns of population structure in the nuclear genome to the mitochondrial genome using Sanger sequences from 455 samples from 183 localities. Our results provide further resolution to the geographic distribution of mitochondria...
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<p>A) Topology for the prior used in the coalescent analysis for dating {Hey, 2010 #1301} of <i>K. boehmei</i> from the Taita Hills. Confidence in this topology prior was estimated by Bayesian posterior probabilities (to... more
<p>A) Topology for the prior used in the coalescent analysis for dating {Hey, 2010 #1301} of <i>K. boehmei</i> from the Taita Hills. Confidence in this topology prior was estimated by Bayesian posterior probabilities (to the left of each branch), and maximum likelihood boostrap (to the right). Divergence times from IMa2 (scale on left in Mya) are given as 95% highest posterior density (HPD) and their high points (horizontal red, green and blue bars with respective HPD distributions). Horizontal blue bars represent two wet periods in the Pleistocene proposed by Trauth et al <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0026606#pone.0026606-Rucina1" target="_blank">[24]</a>. Arrows show time timing of a demographic expansion in Dawida (above), and the relative position of Kilimanjaro to the Taita complex (below: D Dawida; M Mbololo; S Sagalla; K Kasigau). B) A male <i>Kinyongia boehmei</i> in life with C) topology for the genus <i>Kinyongia</i> showing the relative position of to the outgroup (<i>K. tavetana</i>) and other members of the genus from Tolley et al <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0026606#pone.0026606-Tolley6" target="_blank">[47]</a>.</p
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FIGURE 4. A—Adult female Hyperolius cinereus from plateau above Estacao Zootecnica, near Humpata, B—Adult male H. cinereus from Lagoa Carumbo, C—habitat of H. cinereus, D to F—habitat of H. chelaensis sp. nov.
The Cape platanna, Xenopus gilli, an endangered frog, hybridizes with the African clawed frog, X. laevis, in South Africa. Estimates of the extent of gene flow between these species range from pervasive to rare. Efforts have been made in... more
The Cape platanna, Xenopus gilli, an endangered frog, hybridizes with the African clawed frog, X. laevis, in South Africa. Estimates of the extent of gene flow between these species range from pervasive to rare. Efforts have been made in the last 30 years to minimize hybridization between these two species in the west population of X. gilli, but not the east populations. To further explore the impact of hybridization and the efforts to minimize it, we examined molecular variation in one mitochondrial and 13 nuclear genes in genetic samples collected recently (2013) and also over two decades ago (1994). Despite the presence of F1 hybrids, none of the genomic regions we surveyed had evidence of gene flow between these species, indicating a lack of extensive introgression. Additionally we found no significant effect of sampling time on genetic diversity of populations of each species. Thus, we speculate that F1 hybrids have low fitness and are not backcrossing with the parental species to an appreciable degree. Within X. gilli, evidence for gene flow was recovered between eastern and western populations, a finding that has implications for conservation management of this species and its threatened habitat
The excel file contains the PC scores of the geometric morphometric analysis upon which further analyses were performed. Sheets present data for males, females and both sexes together
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Detecting occupied sites of rare species, and estimating the probability that all occupied sites are known within a given area, are desired outcomes for many ecological or conservation projects. Examples include managing all occupied... more
Detecting occupied sites of rare species, and estimating the probability that all occupied sites are known within a given area, are desired outcomes for many ecological or conservation projects. Examples include managing all occupied sites of a threatened species or eradicating an emerging invader. Occupied sites may remain undetected because (1) sites where the species potentially occurs had not been searched, and (2) the species could have been overlooked in the searched sites. For rare species, available data are typically scant, making it difficult to predict sites where the species probably occurs or to estimate detection probability in the searched sites. Using the critically endangered Rose's mountain toadlet (Capensibufo rosei), known from only two localities, we outline an iterative process aimed at estimating the probability that any unknown occupied sites remain and maximizing the chance of finding them. This includes fitting a species distribution model to guide samp...
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Analysis of stomach contents can provide insights into foraging mode, habitat use, and dietary specialization of animals. In this paper, we make observations on the poorly known diet of four southern African agamid species, Agama aculeata... more
Analysis of stomach contents can provide insights into foraging mode, habitat use, and dietary specialization of animals. In this paper, we make observations on the poorly known diet of four southern African agamid species, Agama aculeata distanti (Eastern Ground Agama), Agama armata (Peter's Ground Agama), Agama atra (Southern Rock Agama), and Acanthocercus atricollis (Southern Tree Agama). We examined the diet of 67 individuals by identifying and weighing prey items after stomach flushing lizards in the field. We found that these agama species fed on a broad spectrum of arthropods (11 orders). A high relative importance of ants was present for all agama species examined here, which suggests that ants are a major food source in the arid ecosystem. We found that active prey such as ants, beetles, and highly mobile flying insects like wasps and flies to be major components of the diet, indicating that these lizards are ambush predators. We also found that 43% of the stomachs cont...
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The environmental and socio-economic impacts of invasive species have long been recognised to be unequal, with some species being benign while others are disastrous. Until recently there was no recognised standard impact scoring framework... more
The environmental and socio-economic impacts of invasive species have long been recognised to be unequal, with some species being benign while others are disastrous. Until recently there was no recognised standard impact scoring framework with which to compare impacts of species from very different taxa. The advent of the Environmental Impact Classification for Alien Taxa (EICAT) and Socio‐Economic Impact Classification of Alien Taxa (SEICAT) schemes allows for the possibility of assessing impact through a standard approach. However, both these schemes are still in their infancy and the associated costs of the research that informs them is unknown. We aimed to determine the study costs and complexity associated with assessing invasive species’ socio-economic and environmental impacts. We used amphibians as a model group to investigate papers from which EICAT and SEICAT scores could be drawn up to 2019. Our analysis shows that studies that resulted in higher impact scores were more c...
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Trade-offs are thought to be important in constraining evolutionary divergence as they may limit phenotypic diversification. The cranial system plays a vital role in many functions including defensive, territorial, predatory and feeding... more
Trade-offs are thought to be important in constraining evolutionary divergence as they may limit phenotypic diversification. The cranial system plays a vital role in many functions including defensive, territorial, predatory and feeding behaviours in addition to housing the brain and sensory systems. Consequently, the morphology of the cranial system is affected by a combination of selective pressures that may induce functional trade-offs. Limbless, head-first burrowers are thought to be constrained in their cranial morphology as narrow heads may provide a functional advantage for burrowing. However, having a wide and large head is likely beneficial in terms of bite performance. We used 15 skink species to test for the existence of trade-offs between maximal push and bite forces, and explored the patterns of covariation between external head and body morphology and performance. Our data show that there is no evidence of a trade-off between bite and burrowing in terms of maximal forc...
Research Interests: Biology, Ecology, Morphology, Biological Sciences, Divergence, and 3 moreFossorial, Covariation, and Biting
Temperature and water availability are two of the most important variables affecting all aspects of an anuran’s key physiological processes such as body temperature (Tb), evaporative water loss (EWL) and standard metabolic rate (SMR).... more
Temperature and water availability are two of the most important variables affecting all aspects of an anuran’s key physiological processes such as body temperature (Tb), evaporative water loss (EWL) and standard metabolic rate (SMR). Since anurans display pronounced sexual dimorphism, evidence suggests that these processes are further influenced by other factors such as vapour pressure deficit (VPD), sex and body mass (Mb). However, a limited number of studies have tested the generality of these results across a wide range of ecologically relevant ambient temperatures (Ta), while taking habitat use into account. Thus, the aim of this study was to investigate the role of Ta on Tb, whole-animal EWL and whole-animal SMR in three wild caught African anuran species with different ecological specialisations: the principally aquatic African clawed frog (Xenopus laevis), stream-breeding common river frog (Amietia delalandii), and the largely terrestrial raucous toad (Sclerophrys capensis)....
Research Interests: Zoology, Biology, Ecology, Medicine, Sexual dimorphism, and 8 moreHabitat, Temperature, FROGS, Amphibian, Body Mass, Toad, Ectotherm, and Evaporative Water Loss
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Background: Conservation relies on the strategic use of resources because monies for conservation action are limited, especially in developing countries. South Africa’s Frog Atlas project established a baseline for the country’s amphibian... more
Background: Conservation relies on the strategic use of resources because monies for conservation action are limited, especially in developing countries. South Africa’s Frog Atlas project established a baseline for the country’s amphibian data and threat levels in 2004, and in 2009 a prioritisation exercise developed a strategy for conservation research.Objectives: In this article, we assess this strategy for conservation research.Method: We conducted a quantitative and qualitative assessment of research undertaken since the strategy was developed.Results: The strategy has produced a lasting impact on taxonomy, ecological studies, monitoring and capacity building. Publications in all areas have increased, but particularly in conservation ecology. Other indicators are increases in the numbers of locality records for target taxa, species descriptions and postgraduate degrees with amphibians as the principal topic. We document important milestones for South African amphibian conservati...
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A new species Callulina dawida is described from the Taita Hills, Kenya. It is distinguished from other members of the genus on the basis of the degree of digital expansion. The species further differs from other members of the genus... more
A new species Callulina dawida is described from the Taita Hills, Kenya. It is distinguished from other members of the genus on the basis of the degree of digital expansion. The species further differs from other members of the genus based on molecular sequence comparisons and on its call. The morphological variation in the new species is described, including a comparison of internal and external characters and sexual dimorphism with other species of Callulina. The conservation status of the species, on the basis of its restricted distribution and land use changes in the area, is considered to be of high concern. An updated key of the species of Callulina is provided.
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A new species of African reed frog (genus Hyperolius Rapp, 1842) is described from a high altitude, forested gorge in theSerra da Chela mountain range near the village of Humpata, Lubango area, Huila Province, south-western Angola. It... more
A new species of African reed frog (genus Hyperolius Rapp, 1842) is described from a high altitude, forested gorge in theSerra da Chela mountain range near the village of Humpata, Lubango area, Huila Province, south-western Angola. It iscurrently only known from its type locality. Phylogenetic reconstruction using the mitochondrial 16S marker reveals thatit is the sister taxon of the poorly known Hyperolius cinereus (>4% sequence divergence) also described from Angola, andforms part of a larger clade comprising H. platyceps. The new species is distinguished from other closely related Hyperolius species by genetic divergence, vocalisation, an unusual torrent stream habitat, and colouration.
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Predators can play an important role in regulating prey abundance and diversity, determining food web structure and function, and contributing to important ecosystem services, including the regulation of agricultural pests and disease... more
Predators can play an important role in regulating prey abundance and diversity, determining food web structure and function, and contributing to important ecosystem services, including the regulation of agricultural pests and disease vectors. Thus, the ability to predict predator impact on prey is an important goal in ecology. Often, predators of the same species are assumed to be functionally equivalent, despite considerable individual variation in predator traits known to be important for shaping predator–prey interactions, like body size. This assumption may greatly oversimplify our understanding of within-species functional diversity and undermine our ability to predict predator effects on prey. Here, we examine the degree to which predator–prey interactions are functionally homogenous across a natural range of predator body sizes. Specifically, we quantify the size-dependence of the functional response of African clawed frogs (Xenopus laevis) preying on mosquito larvae (Culex ...
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Research Interests: Zoology, Cannibalism, Biology, Ecology, Vulnerability, and 9 moreXenopus, Predation, Tadpole, CAPE, Larva, Size, Cannabalism, Predator Prey, and African ecology
Invasive species frequently cope with ecological conditions that are different from those to which they adapted, presenting an opportunity to investigate how phenotypes change across short time scales. In 2000, the guttural toad was first... more
Invasive species frequently cope with ecological conditions that are different from those to which they adapted, presenting an opportunity to investigate how phenotypes change across short time scales. In 2000, the guttural toad was first detected in a peri-urban area of Cape Town, where it is now invasive. The ability of the species to invade Cape Town is surprising since the area is characterised by a mediterranean climate significantly drier and colder than that of the native source area. We measured field hydration state of guttural toads from the invasive Cape Town population and a presumed native source population from Durban. We also obtained from laboratory trials: rates of evaporative water loss and water uptake, sensitivity of locomotor endurance to hydration state, critical thermal minimum (CT) and sensitivity of CT to hydration state. Field hydration state of invasive toads was significantly lower than that of native toads. Although the two populations had similar rates ...
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Age-specific survival and reproduction are closely linked to fitness and therefore subject to strong selection that typically limits their variability within species. Furthermore, adult survival rate in vertebrate populations is typically... more
Age-specific survival and reproduction are closely linked to fitness and therefore subject to strong selection that typically limits their variability within species. Furthermore, adult survival rate in vertebrate populations is typically less variable over time than other life-history traits, such as fecundity or recruitment. Hence, adult survival is often conserved within a population over time, compared to the variation in survival found across taxa. In stark contrast to this general pattern, we report evidence of extreme short-term variation of adult survival in Rose's mountain toadlet (Capensibufo rosei), which is apparently climate induced. Over 7 years, annual survival rate varied between 0.04 and 0.92, and 94% of this variation was explained by variation in breeding-season rainfall. Preliminary results suggest that this variation reflects adaptive life-history plasticity to a degree thus far unrecorded for any vertebrate, rather than direct rainfall-induced mortality. In...
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Alien species can have major ecological and socioeconomic impacts in their novel ranges and so effective management actions are needed. However, management can be contentious and create conflicts, especially when stakeholders who benefit... more
Alien species can have major ecological and socioeconomic impacts in their novel ranges and so effective management actions are needed. However, management can be contentious and create conflicts, especially when stakeholders who benefit from alien species are different from those who incur costs. Such conflicts of interests mean that management strategies can often not be implemented. There is, therefore, increasing interest in engaging stakeholders affected by alien species or by their management. Through a facilitated workshop and consultation process including academics and managers working on a variety of organisms and in different areas (urban and rural) and ecosystems (terrestrial and aquatic), we developed a framework for engaging stakeholders in the management of alien species. The proposed framework for stakeholder engagement consists of 12 steps: (1) identify stakeholders; (2) select key stakeholders for engagement; (3) explore key stakeholders' perceptions and develo...
Research Interests: Business, Environmental Management, Ecology, Biological invasions, Medicine, and 11 moreMultidisciplinary, Stakeholder Engagement, Perceptions, Introduced species, Ecosystem, Invasive Species Management, Stakeholder, Gestion Des Ressources Naturelles, Biodiversité, Conflicts of Interests, and utilisation des terres
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The widespread African clawed frog (Xenopus laevis) occurs in sympatry with the IUCN Endangered Cape platanna (Xenopus gilli) throughout its entire range in the south-western Cape, South Africa. In order to investigate aspects of the... more
The widespread African clawed frog (Xenopus laevis) occurs in sympatry with the IUCN Endangered Cape platanna (Xenopus gilli) throughout its entire range in the south-western Cape, South Africa. In order to investigate aspects of the interspecific competition between populations of X. laevis and X. gilli, an assessment of their niche differentiation was conducted through a comprehensive study on food composition and trophic niche structure at two study sites: the Cape of Good Hope (CoGH) and Kleinmond. A total of 399 stomach contents of X. laevis (n = 183) and X. gilli (n = 216) were obtained together with samples of available prey to determine food preferences using the Electivity index (E*), the Simpson's index of diversity (1 - D), the Shannon index (H'), and the Pianka index (Ojk ). Xenopus gilli diet was more diverse than X. laevis, particularly in Kleimond where the Shannon index was nearly double. Both species were found to consume large amounts of tadpoles belonging ...
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Invasive species are among the most significant threats to biodiversity. The diet of invasive animal populations is a crucial factor that must be considered in the context of biological invasions. A broad dietary spectrum is a frequently... more
Invasive species are among the most significant threats to biodiversity. The diet of invasive animal populations is a crucial factor that must be considered in the context of biological invasions. A broad dietary spectrum is a frequently cited characteristic of invasive species, allowing them to thrive in a wide range of environments. Therefore, empirical studies comparing diet in invasive and native populations are necessary to understand dietary requirements, dietary flexibility, and the associated impacts of invasive species. In this study, we compared the diet of populations of the African clawed frog, Xenopus laevis in its native range, with several areas where it has become invasive. Each prey category detected in stomach contents was assigned to an ecological category, allowing a comparison of the diversity of ecological traits among the prey items in the diet of native and introduced populations. The comparison of diets was also performed using evenness as a niche breadth in...
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The Cape platanna, Xenopus gilli, an endangered frog, hybridizes with the African clawed frog, X. laevis, in South Africa. Estimates of the extent of gene flow between these species range from pervasive to rare. Efforts have been made in... more
The Cape platanna, Xenopus gilli, an endangered frog, hybridizes with the African clawed frog, X. laevis, in South Africa. Estimates of the extent of gene flow between these species range from pervasive to rare. Efforts have been made in the last 30 years to minimize hybridization between these two species in the west population of X. gilli, but not the east populations. To further explore the impact of hybridization and the efforts to minimize it, we examined molecular variation in one mitochondrial and 13 nuclear genes in genetic samples collected recently (2013) and also over two decades ago (1994). Despite the presence of F 1 hybrids, none of the genomic regions we surveyed had evidence of gene flow between these species, indicating a lack of extensive introgression. Additionally we found no significant effect of sampling time on genetic diversity of populations of each species. Thus, we speculate that F 1 hybrids have low fitness and are not backcrossing with the parental speci...
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Background: Globally, invasive amphibians are known for their environmental and social impacts that range from poisoning of local fauna and human populations to direct predation on other amphibians. Although several countries on most... more
Background: Globally, invasive amphibians are known for their environmental and social impacts that range from poisoning of local fauna and human populations to direct predation on other amphibians. Although several countries on most continents have had multiple introductions of many species, southern Africa appears to have escaped allochthonous introductions. Instead, it has a small number of domestic exotic species that have rapidly expanded their ranges and established invasive populations within South Africa. Objectives methods: We used the literature to provide a historical overview of dispersal by some of the world’s major invasive amphibians, give examples of species that are commonly moved as stowaways and discuss historical and current amphibian trade in the region. In addition, we give an overview of new South African legislation and how this is applied to amphibian invasions, as well as providing updates on the introduced populations of three domestic exotics: Hyperolius ...