Measey J

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Now showing 1 - 5 of 36
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    Toad-kill: Prey diversity and preference of invasive guttural toads (Sclerophrys gutturalis) in Mauritius
    (2021) Baxter-Gilbert, J.; Florens, F.B.V.; Baider, C.; Perianen, Y.D.; Citta, D.S.; Appadoo, C.; Measey, J.
    The invertebrate communities of Mauritius host a high degree of endemism, but are also imperilled by an array of factors, including invasive predators. Since their introduction in 1922, guttural toads (Sclerophrys gutturalis) have spread across the island and have been implicated in the decline of a number of endemic invertebrate species. In this study, we examined the feeding habits of the invasive population of guttural toads from three naturally forested locations in Mauritius across multiple years by analysing their stomach content. We also measured the relative abundance of prey items on the landscape using pitfall traps and applied these data to determine prey preference using a Relativised Electivity Index. Insects, malacostracans and gastropods constituted the bulk of the toads' diet (48.7%, 33.4% and 11.8%, respectively), which also included several rare and endemic species. We further determined that insects and malacostracans were also the two most favoured prey taxa, relative to what was available on the landscape. Our investigation has generated several recommendations for future research and provides a fundamental understanding of the diet of guttural toads in the native forests of Mauritius.
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    Sex chromosome degeneration, turnover, and sex-biased expression of sex-linked transcripts in African clawed frogs (Xenopus)
    (2021) Song, X.-Y.; Furman, B.L.S.; Premachandra, T.; Knytl, M.; Cauret, C.M.S.; Wasonga, D.V.; Measey, J.; Dworkin, I.; Evans, B.J.
    The tempo of sex chromosome evolution—how quickly, in what order, why and how their particular characteristics emerge during evolution—remains poorly understood. To understand this further, we studied three closely related species of African clawed frog (genus Xenopus), that each has independently evolved sex chromosomes. We identified population polymorphism in the extent of sex chromosome differentiation in wild-caught Xenopus borealis that corresponds to a large, previously identified region of recombination suppression. This large sex-linked region of X. borealis has an extreme concentration of genes that encode transcripts with sex-biased expression, and we recovered similar findings in the smaller sex-linked regions of Xenopus laevis and Xenopus tropicalis. In two of these species, strong skews in expression (mostly female-biased in X. borealis, mostly male-biased in X. tropicalis) are consistent with expectations associated with recombination suppression, and in X. borealis, we hypothesize that a degenerate ancestral Y-chromosome transitioned into its contemporary Z-chromosome. These findings indicate that Xenopus species are tolerant of differences between the sexes in dosage of the products of multiple genes, and offer insights into how evolutionary transformations of ancestral sex chromosomes carry forward to affect the function of new sex chromosomes.
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    Motivations and contributions of volunteer groups in the management of invasive alien plants in South Africa’s Western Cape province
    (2021) Jubase, N.; Shackleton, R.T.; Measey, J.
    Background: Research and management of biological invasions traditionally focuses on state operated large scale control initiatives, with little emphasis on volunteers. Volunteering can, however, contribute to detection, eradication and containment of invasive alien plant species (IAPS). Understanding the extent of involvement of volunteers in invasive alien species management is important. Similarly, understanding volunteers’ motivations to volunteering is important to improve the success of invasive alien species management. Objective: In this study we aimed to: 1) identify volunteer groups controlling IAPS in the Western Cape province of South Africa, 2) understand their practices and contributions towards detecting and controlling IAPS, 3) examine volunteer’s motivations for controlling IAPS, and, 4) identify the challenges individual volunteers and groups face. Methods: The data were collected using online questionnaires. Results: In total, we identified 52 volunteer groups. We broadly estimate that these groups clear nearly 8000 ha of land with estimated labour costs of ZAR 6.5 million annually (equivalent to USD 0.38 million) when aligned with formal state management cost estimates. Most volunteer groups raise their own funds to facilitate their work, however, many suggest support from government entities, landowners and Non-Government Organisations would help. Most volunteers (82%) detect and report invasive species to their team leaders, citizen science platforms and relevant authorities. Volunteers themselves gain physical and psychological fulfilment and build their social capital by meeting new people. Conclusion: Our findings point to the valuable contribution of these groups, but also the need for better co-ordination and engagement between volunteer groups and mandated authorities on science, policy and management
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    After the fire: assessing the microhabitat of Capensibufo rosei (Hewitt, 1926)
    (2021) Measey, J.; Becker, F.; Tolley, K.A.
    Rose’s dwarf mountain toadlet, Capensibufo rosei (Hewitt, 1926), is endemic to fire-dependent, montane fynbos vegetation on South Africa’s Cape Peninsula. The area undergoes natural fire cycles that are disrupted due to increasing urban pressure from the City of Cape Town. In this natural history observation, we report on C. rosei microhabitats used and their distribution immediately after a wildfire that swept through the area in March 2015. We found that a substantial number of adult toadlets had survived the fire, and that they were located within 160 m of a known breeding site. Animals were consistently found inside burrows, presumed to have been excavated by small rodents. Our observations have important consequences on the conservation of this IUCN Critically Endangered species, especially with relation to compaction of areas in the immediate vicinity of breeding sites. We emphasise the importance of making natural history observations following extreme events, such as fire, to provide important insights into conservation of cryptic threatened species.
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    Challenges of a novel range: water balance, stress, and immunity in an invasive toad
    (2021) Barsotti, A.M.G.; Madelaire, C.B.; Wagener, C.; Titon Jr, B.; Measey, J.; Gomesa, F.R.
    Species introduced by human activities can alter the normal functioning of ecosystems promoting negative impacts on native biodiversity, as they can rapidly expand their population size, demonstrating phenotypic plasticity and possible adaptive capacity to novel environments. Twenty years ago, the guttural toad, Sclerophrys gutturalis, was introduced to a peri-urban area of Cape Town, with cooler and drier climatic characteristics than its native source population, Durban, South Africa. Our goal was to understand the phenotypic changes, in terms of physiology and immunity, of populations in native and novel environments. We evaluated body index (BI), field hydration level, plasma corticosterone levels (CORT), proportion of neutrophils: lymphocytes (N: L), plasma bacterial killing ability (BKA), and hematocrit (HTC) in the field, and after standardized stressors (dehydration and movement restriction) in males from the native and invasive populations. Toads from the invasive population presented lower BI and tended to show a lower field hydration state, which is consistent with living in the drier environmental conditions of Cape Town. Additionally, invasive toads also showed higher BKA and N:L ratio under field conditions. After exposure to stressors, invasive animals presented higher BKA than the natives. Individuals from both populations showed increased CORT after dehydration, an intense stressor for these animals. The highest BKA and N:L ratio in the field and after submission to stressors in the laboratory shows that the invasive population has a phenotype that might increase their fitness, leading to adaptive responses in the novel environment and, thus, favoring successful dispersion and population increase.