Browsing by Subject "Passerines"

Now showing 1 - 3 of 3
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    Open Access
    Departures from the energy-biodiversity relationship in south african passerines: are the legacies of past climates mediated by behavioral constraints on dispersal?
    (Public Library of Science, 2015) Péron, Guillaume; Altwegg, Res
    Legacies of paleoclimates in contemporary biodiversity patterns have mostly been investigated with global datasets, or with weakly dispersive organisms, and as a consequence been interpreted in terms of geographical or physical constraints. If paleoclimatic legacies also occurred at the regional scale in the distributions of vagile organisms within biomes, they would rather suggest behavioral constraints on dispersal, i.e., philopatric syndromes. We examined 1) the residuals of the regression between contemporary energy and passerine species richness in South African biomes and 2) phylogenetic dispersion of passerine assemblages, using occupancy models and quarter-degree resolution citizen science data. We found a northeast to southwest gradient within mesic biomes congruent with the location of Quaternary mesic refugia, overall suggesting that as distance from refugia increased, more clades were lacking from local assemblages. A similar but weaker pattern was detected in the arid Karoo Biomes. In mobile organisms such as birds, behavioral constraints on dispersal appear strong enough to influence species distributions thousands of years after historical range contractions.
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    Open Access
    Host specificity and co-speciation in avian haemosporidia in the Western Cape, South Africa
    (Public Library of Science, 2014) Okanga, Sharon; Cumming, Graeme S; Hockey, Philip A R; Nupen, Lisa; Peters, Jeffrey L
    Host and pathogen ecology are often closely linked, with evolutionary processes often leading to the development of host specificity traits in some pathogens. Host specificity may range from ‘generalist’, where pathogens infect any available competent host; to ‘specialist’, where pathogens repeatedly infect specific host species or families. Avian malaria ecology in the region remains largely unexplored, despite the presence of vulnerable endemic avian species. We analysed the expression of host specificity in avian haemosporidia, by applying a previously developed host specificity index to lineages isolated from wetland passerines in the Western Cape, South Africa. Parasite lineages were isolated using PCR and identified when possible using matching lineages deposited in GenBank and in MalAvi. Parasitic clades were constructed from phylogenetic trees consisting of Plasmodium and Haemoproteus lineages. Isolated lineages matched some strains of Plasmodium relictum , P. elongatum , Haemoproteus sylvae and H. lanii . Plasmodium lineages infected a wide range of hosts from several avian families in a generalist pattern of infection. Plasmodium spp. also exhibited an infection trend according to host abundance rather than host species. By contrast, Haemoproteus lineages were typically restricted to one or two host species or families, and displayed higher host fidelity than Plasmodium spp. The findings confirm that a range of host specificity traits are exhibited by avian haemosporidia in the region. The traits show the potential to not only impact infection prevalence within specific host species, but also to affect patterns of infection at the community level.
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    Temperatures in Excess of Critical Thresholds Threaten Nestling Growth and Survival in A Rapidly-Warming Arid Savanna: A Study of Common Fiscals
    (Public Library of Science, 2013) Cunningham, Susan J; Martin, Rowan O; Hojem, Carryn L; Hockey, Philip A R
    Frequency, duration, and intensity of hot-weather events are all predicted to increase with climate warming. Despite this, mechanisms by which temperature increases affect individual fitness and drive population-level changes are poorly understood. We investigated the link between daily maximum air temperature (t max ) and breeding success of Kalahari common fiscals ( Lanius collaris ) in terms of the daily effect on nestling body-mass gain, and the cumulative effect on size and age of fledglings. High t max reduced mass gain of younger, but not older nestlings and average nestling-period t max did not affect fledgling size. Instead, the frequency with which t max exceeded critical thresholds (t crit s) significantly reduced fledging body mass (t crit  = 33°C) and tarsus length (t crit  = 37°C), as well as delaying fledging (t crit  = 35°C). Nest failure risk was 4.2% per day therefore delays reduced fledging probability. Smaller size at fledging often correlates with reduced lifetime fitness and might also underlie documented adult body-size reductions in desert birds in relation to climate warming. Temperature thresholds above which organisms incur fitness costs are probably common, as physiological responses to temperature are non-linear. Understanding the shape of the relationship between temperature and fitness has implications for our ability to predict species’ responses to climate change.