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Overview

Overview

In line with our mission statement, the research currently undertaken by members of the Fitztitute can be broadly placed within the themes of Characterising Biodiversity, Evolutionary Ecology and Maintaining Biodiversity. Several research programmes are co-ordinated by staff members and include the research projects of the Institute's postgraduate students.

Effective conservation of biodiversity depends critically on knowledge of the following:

  • the processes responsible for generating biodiversity,
  • the present composition of biodiversity,
  • how complex relationships between organisms and their environment influence the form and functioning of biological systems,
  • how human activities impact upon these systems,
  • how these impacts can best be assessed, predicted and managed to ensure the long-term maintenance of biodiversity.

Characterising Biodiversity

In this theme the composition and structure of biodiversity, the processes responsible for its generation, and how relationships between organisms and their environments influence the form and functioning of biological systems is investigated.

The research focus provides a theoretical and empirical foundation for biodiversity conservation and management. It comprises three interrelated components which together investigate the relationships and interactions between organisms and their environments across a range of spatial and temporal scales:

  • Inferring process from pattern
  • Investigating the process of speciation
  • Applied population genetics

Inferring process from pattern

We explore large-scale patterns of biodiversity, primarily among birds, to detect overlooked units of biodiversity (‘cryptic’ species), and to test whether there are consistent evolutionary patterns among diverse lineages that might indicate common vicariance or dispersal events. We also generate phylogenetic hypotheses (trees), against which the occurrence of particular phenotypic traits can be compared.

Are there consistent evolutionary patterns across the arid-mesic interface in southern Africa? Within southern Africa, the strong east-west aridity gradient results in many taxa having parapatric forms in the arid west and more mesic east. Taxa in the arid west typically extend from south-western Angola through Namibia and Botswana to western South Africa (their ranges crudely shaped like a ‘6’). Taxa in the more mesic east often extend broadly from central Africa through Zimbabwe and Mozambique to eastern South Africa (with ranges shaped like a ‘9’). We are testing for consistent genetic differences across this ‘69’ arid-mesic divide to gain insights into the evolution of the arid zone fauna (which is characterised by high levels of endemism, and infer what processes (e.g. vicariance, dispersal) might have generated these patterns.

Are common vicariance events evident between the south-western and north-eastern African arid zones? The arid zones of Africa are thought to be ancient, stable regions, with resultant high biodiversity and endemism. The south-western arid zone shares many species or species-pairs with the currently disjunct north-eastern arid zone (Kenya, northern Tanzania, southern Ethiopia and Somalia), suggesting that, historically, the two regions were repeatedly connected by an ‘arid corridor’. We will infer the history of these regions using a suite of birds, insects and plants, and relate the patterns we detect to palaeoclimatic hypotheses and models.

Are there common patterns of phylogeography among taxa in Africa’s montane forests? Afromontane forests comprise a highly fragmented chain of small, threatened habitats extending from near sea level in southern South Africa along the mountain chains of eastern South Africa and Zimbabwe, north through central and east Africa to the highlands of Ethiopia, with outliers in western Angola and southwest Cameroon. There is considerable phylogeographic structure among the bird populations of these forests, resulting in a hypothesis that the latter are species ‘pumps', responsible for generating much diversity among African forest birds.

Can morphometric-cladistic approaches provide robust phylogenetic hypotheses for fossils? There is a pressing need for quantitative approaches to assigning fossils to the correct taxon, and placing them within robust phylogenies, to understand both their age and biogeography. Crowe and Dyke have devised a novel approach to this problem; assuming it works, it should go some way towards settling the apparent conflict between dates assigned to fossils and dating inferred from molecular evidence.

Investigating the process of speciation

Species and speciation continue to be among the most hotly debated subjects in evolutionary biology. Understanding speciation and hybridisation, the processes responsible for the origin and maintenance of species-level diversity, are crucial because climatic change and introduced species constantly alter the spectrum of species that meet and potentially interact. Birds have proved to be pivotal in developing and testing speciation theories.

Our ongoing research into population structure and phylogeny has already identified numerous examples of contact zones between taxa. These zones provide natural laboratories for further testing and developing these ideas. Many contact zones run along steep biophysical gradients. They may be maintained by (1) ecological segregation (habitat choice); (2) a dynamic equilibrium between random dispersal and selection against hybrids because of reduced reproductive fitness, or (3) bounded hybrid superiority, where selection favours hybrid phenotypes along the environmental ecotone between habitats occupied by the two parental phenotypes. Others are less clearly linked to environmental gradients, and may either be maintained by a dynamic tension between random dispersal and selection, or may be unstable.

To identify whether there are consistent, predictable patterns of gene flow (and hence hybrid zone stability) linked to particular types of contact zones, we are exploring the individual-level interactions that take place between taxa within contact zones, in relation to the spread of genes (tracked using nuclear and mitochondrial markers) into adjacent populations. Studies of speciation and hybrid zones will focus on documenting the extent of overlap (using both morphological and molecular evidence of hybridisation, as well as investigating the processes mediating the dynamics of the hybrid zone (e.g. mate recognition systems, assortative mating, fitness of hybrids, physiological tolerance, etc.). In this arena, the team’s biodiversity scientists will interact closely with behavioural ecologists and physiologists to address the following key questions:

  • how stable are the contact zones?
  • how closely do morphological and genetic markers of hybridisation across contact zones concur?
  • what are the key biological attributes (e.g. vocalisations, plumage, displays) that help to maintain barriers between, or promote intergradation of species?
  • to what extent has anthropogenic habitat transformation (including climate change and introduced species) influenced the dynamics of hybrid zones?

Four focal studies have been identified. We propose to test the hybrid superiority hypothesis in at least one of these cases by evaluating the physiological performance of hybrids and parental species.

Applied population genetics

Population genetics provides valuable insight into population structure and, at least in theory, provides estimates of effective dispersal across populations. Effective dispersal distances and frequencies remain perhaps the greatest unknown in avian ecology. Knowledge of dispersal is crucial for conservation management, because of the need, firstly, to understand the extent to which dispersal connects populations, and subsequently, to predict how this is likely to change in response to habitat loss and fragmentation.

Phylogeography and landscape-level genetics provide powerful tools with which to investigate this issue. We intend to capitalise on extensive studies of bird movements that currently lack a genetic component. For example, our studies of Cape Gannets and African Black Oystercatchers allow comparisons of genetic evidence for movements versus known movement patterns obtained from band recoveries/resightings. Other applications of population genetics at the landscape level include assessing impacts of ‘sustainable’ hunting on phylogeographic structures and population level processes within, e.g. gamebirds, and to test hypotheses about factors driving differential dispersal patterns in species, such as oystercatchers.

The study of geographical variation in genetic diversity within species (phylogeography) can also have direct forensic applications in conservation management. If regional or local differences in combinations of genes are distinctive, they can be used to trace the origin of individual organisms. For example, in South Africa enforcement agencies struggled to prosecute poachers of Perlemoen (abalone) Haliotis midae, a valuable marine mollusc poached heavily for export to East Asian markets. Once the shell is removed, it is no longer possible to assign it correctly even to species, creating a loophole that allowed accused poachers to claim that the abalone in their possession originated from another species. The development of a molecular DNA identification technique provided the necessary tool to close this loophole. Similarly, highly variable genes can be used to confirm parentage if there is dispute about the origin of particular individuals (e.g. challenging claims that birds were bred in captivity). This research seeks to facilitate the interaction between biodiversity scientists and law enforcement agencies through genetic studies of a series of plants and animals collected for illegal trade.

Evolutionary ecology

  • Ecological and evolutionary physiology
  • Life history strategies
  • Breeding strategies
  • Migration and dispersal strategies
  • Population biology and rarity

Ecological and evolutionary physiology

By bridging the gaps between physics, chemistry, ecology and evolution, the fields of ecological and evolutionary physiology reveal how internal and external environments affect the interactions between an organism’s genotype, phenotype, short-term performance and long-term performance, which in turn determine its evolutionary fitness.

Physiological research within the CoE currently falls into two areas:

  • Physiology and life-history: patterns and processes
  • Avian responses to climate change: physiological mechanisms

Life history strategies

A major challenge in evolutionary biology is to explain why life-history traits vary among species along a slow-fast continuum. Species at the slow end of the spectrum are characterised by slow metabolism and development, delayed reproduction, low reproductive investment, long life, and long-term pair bonds, with the opposite expression at the fast end. The South African south-temperate avifauna comprises species with life-history strategies that span much of the slow-fast continuum, making it an ideal region in which to study environmental influences on life-history strategies.

Our research focus in life-history evolution uses four broad approaches:

  • Using the Roberts VII database to conduct broad-scale comparisons of life-history traits of southern African birds with published data for north temperate taxa to clarify patterns of differences, while controlling for phylogeny.
  • Intensive studies of individual species at single sites to examine the proximate influences of environmental factors and the degree of phenotypic plasticity.
  • Studies of breeding bird communities at single sites to compare life-history traits across taxa, using paired comparisons in experimental tests.
  • Studies of individual species or closely related species pairs across multiple sites along environmental gradients.

Breeding strategies

Within this sub-theme, we focus on developing a better understanding of how environmental factors have shaped the evolution of different reproductive strategies, with a particular emphasis on sociality, cooperative breeding, and adaptive responses to habitat saturation. Cooperative breeding is a social system in which more than two individuals combine to rear a single brood of young, generating the paradox that ‘extra’ individuals, called helpers, care for young that are not their own. Studies of cooperative breeding are guided by a two-question framework: (1) why do birds remain philopatric instead of dispersing to breed independently, and (2) why do philopatric birds provide care to offspring raised on the territory? The incidence of group living and cooperative breeding is greatest in south-temperate regions, particularly southern Africa and Australia. High adult survival, and extended post-fledging care (result in retention of juveniles on the natal territory for periods exceeding a year), have together been implicated as a major proximate cause of cooperative breeding. A further correlation is the higher incidence of obligate siblicide among long-lived, southern hemisphere species, which may arise from the need for high quality offspring under conditions of habitat saturation.

Migration and dispersal strategies

Migrations of birds are repeated seasonal movements, predictable in time and space, usually on an annual cycle, but sometimes deferred by juveniles of taxa with delayed sexual maturity. Nomadic movements, by contrast, are responses to unpredictable resource peaks and troughs. Dispersive movements, undertaken primarily by juvenile birds moving away from their natal site, are short-distance and exploratory, with little directional predictability.

Migration: Bird migration is a global phenomenon, but a global research perspective on migration is conspicuously lacking. Southern Hemisphere migration patterns mirror those of the north (from tropical to temperate areas to breed), but occur over shorter distances and between sites that are more climatically and structurally similar. In an evolutionary sense, therefore, these movements are closer to the putative ancestral condition of partial or short-distance migration. Our research on migration focuses on the relative importance of evolutionary history (ultimate factors) and environmental pressures (proximate factors) in shaping migration patterns, and addresses the following key questions:

  • Do the functional attributes (diet, foraging mode, etc.) of short-distance, low-latitude migrants differ across the three major flyways?
  • How do the functional attributes of short-distance migrants (ancestral) compare with those of longer-distance migrants (derived)?
  • Can the similarities or differences detected in 1 & 2 above be explained by seasonal variations in resource availability?
  • What is the most parsimonious functional classification of migrants and, given that migration has undoubtedly evolved independently on many occasions, does this provide insight into these evolutionary processes?
  • Can density-dependence drive the evolution of migratory behaviour?

Dispersal: Dispersal of individuals between sites or habitable patches is a major, but relatively neglected component of life-history. The proximate and ultimate factors influencing natal dispersal strategies, and how these might differ between north-temperate birds on the one hand, and tropical or south-temperate birds on the other hand, are particularly poorly known. We study proximate and ultimate factors influencing both natal and breeding dispersal as a component of life-history variation in two other research programmes:

Population biology and rarity

Population biology strives to understand the processes that regulate the distribution and abundance of organisms as a consequence of environmental heterogeneity or change. Within this theme, we use a strong focus on understanding the causes and consequences of spatial and temporal variation in fecundity and survival to diagnose the causes of population-level problems. Our expertise in linking life-history studies with remedial action for threatened taxa has been applied in locations as disparate as sub-Antarctic Islands, tropical islands in central America and the Indian Ocean, forests of the Albertine Rift, and highland wetlands of Ethiopia. We are also developing strong theoretical frameworks for understanding the causes and consequences of rarity, and the relative importance of life-history variables for population growth rate among species.

Maintaining biodiversity

This theme builds on the strong theoretical and empirical foundation provided by the first two themes to assess, predict and manage human impact, with emphasis on understanding the dynamic links that lead to biodiversity loss, developing effective strategies to stem that loss, and discovering ways to use components of biodiversity sustainably to the benefit of South Africa.

Maintaining Biodiversity

The maintaining biodiversity theme involves applied research which includes:

  • spatial resilience of protected areas,
  • birds as disease vectors
  • island conservation,
  • seabird research,
  • climate change vulnerability and adaptation, and
  • rarity and the conservation of African birds.

Using birds to conserve biodiversity is the central vision of the CoE. Mainland Africa is the only continent with an intact megafauna. Despite having more than 20% of the world’s birds, it is the only continent apart from Antarctica not to have lost a single bird species in the past 400 years. Despite this apparent state of wellbeing, however, much of Africa’s biodiversity is now under threat.

A key challenge of the 21st Century is to balance human needs and aspirations with the conservation of biodiversity and the maintenance of robust, functioning ecosystems. Our mission is to promote and undertake scientific studies involving birds, and contribute to the theory and practice of maintaining biological diversity and the sustained use of biological resources.

Birds are arguably the best known group of organisms. Studies of birds have been pivotal in developing much biological theory, and it is scientific research and its publication that form the Institute’s core business. Because of their mobility and conspicuousness, birds have been used successfully as indicators of environmental change. Their high public profile makes them excellent vehicles for increasing awareness among politicians, decision makers and the public on environmental issues.

Much of our field research is carried out in southern Africa, but we also work on islands in the Indian and Atlantic Oceans and the Subantarctic, and elsewhere in sub-Saharan Africa, from rain forests to deserts. Our study species have been equally diverse. A cross-section of recent southern African study species include the Black Harrier, African Black Oystercatcher, Southern Ground-Hornbill, Blue Swallow, Ludwig’s Bustard, Cape Parrot, Southern Pied Babbler and Bearded Vulture. Study species from elsewhere in Africa include Crab Plover, Aldabra Rail, Souimanga Sunbird, Chaplin’s Barbet, Papyrus Gonolek and Sharpe’s Longclaw. Many species have also been studied on southern ocean islands, including several albatross and penguin species, Spectacled Petrel, Inaccessible Island Flightless Rail and the buntings of the Tristan Group.

If you would like to know more or would like to participate in any of the research programmes or projects, please contact the Coordinator of the research programme in question. For general enquiries please contact the Departmental Administrator.