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Adaptive radiation is facilitated by a rugged adaptive landscape, where fitness peaks correspond to trait values that enhance the use of distinct resources. Different species are thought to occupy the different peaks, with hybrids falling into low-fitness valleys between them. We hypothesize that human activities can smooth adaptive landscapes, increase hybrid fitness and hamper evolutionary diversification. We investigated this possibility by analysing beak size data for 1755 Geospiza fortis measured between 1964 and 2005 on the island of Santa Cruz, Galápagos. Some populations of this species can display a resourcebased bimodality in beak size, which mirrors the greater beak size differences among species. We first show that an historically bimodal population at one site, Academy Bay, has lost this property in concert with a marked increase in local human population density. We next show that a nearby site with lower human impacts, El Garrapatero, currently manifests strong bimodality. This comparison suggests that bimodality can persist when human densities are low (Academy Bay in the past, El Garrapatero in the present), but not when they are high (Academy Bay in the present). Human activities may negatively impact diversification in 'young' adaptive radiations, perhaps by altering adaptive landscapes.

Summary1. Expert knowledge is used routinely to inform listing decisions under the IUCN Red List criteria. Differences in opinion arise between experts in the presence of epistemic uncertainty, as a result of different interpretations of incomplete information and differences in individual beliefs, values and experiences. Structured expert elicitation aims to anticipate and account for such differences to increase the accuracy of final estimates. 2. A diverse panel of 16 experts independently evaluated up to 125 parameters per taxon to assess the IUCN Red List category of extinction risk for nine Australian bird taxa. Each panellist was provided with the same baseline data. Additional judgments and advice were sought from taxon specialists outside the panel. One question set elicited lowest and highest plausible estimates, best estimates and probabilities that the true values were contained within the upper and lower bounds. A second question set elicited yes ⁄ no answers and a degree of credibility in the answer provided. 3. Once initial estimates were obtained, all panellists were shown each others' values. They discussed differences and reassessed their original values. Most communication was carried out by email. 4. The process took nearly 6 months overall to complete, and required an average of 1 h and up to 13 h per taxon for a panellist to complete the initial assessment. 5. Panellists were mostly in agreement with one another about IUCN categorisations for each taxon. Where they differed, there was some evidence of convergence in the second round of assessments, although there was persistent non-overlap for about 2% of estimates. The method exposed evidence of common subjective biases including overconfidence, anchoring to available data, definitional ambiguity and the conceptual difficulty of estimating percentages rather than natural numbers. 6. This study demonstrates the value of structured elicitation techniques to identify and to reduce potential sources of bias and error among experts. The formal nature of the process meant that the consensus position reached carried greater weight in subsequent deliberations on status. The structured process is worthwhile for high profile or contentious taxa, but may be too time intensive for less divisive cases.

Over one hundred species of birds have been seen visiting the flowers of some 250 species of plants in Australia. Honeyeaters and lorikeets are the most persistent flowerfeeders and some species depend almost entirely on nectar as a source of energy. Silvereyes, parrots, woodswallows, pardalotes, thornbills, and a few other species of passerines occasionally visit flowers. The genera most frequently visited are Eucalyptus, and Eremophila. Some flowers, e.g., those of Eucalyptus, are very generalised in structure and are visited and pollinated by insects as well as birds. Other plants have shown a range of adaptations to attract birds to their flowers or deter insects. Birds require significant rewards so that flowers must produce copious nectar. Flowers are often clumped into inflorescences (e.g., Banksia) or individual flowers become large and tubular or gullet-shaped (Eremophila). Flowers visited by birds are often red, though yellow (Adenanthos) and green (e.g., Amyema, Correa) are common. Hairs in tubular flowers, and lack of attractive smell may deter insects without affecting birds (e.g., Astroloma). In Australia the relationships between birds and plants are not as specific as those shown for hummingbirds and some of their flowers in tropical America. Most species of birds visit a wide range of plants, and most plants are visited by a wide range of birds.Pollen is usually placed on the forehead, face, and chin feathers of the bird oron its beak. Birds have been proved to be effective pollinators of many plants in temperate Australia. Little work has so far been carried out in tropical Australia.Bird-pollinated flowers have mostly originated from insect-pollinated flowers though it is possible that some (e.g., Banksia) were, or still are, pollinated by mammals.It is not clear why so many of the dominant plant genera in temperate Australia are pollinated by birds. Birds may be more reliable pollinators than insects when the climate and flowering season are unpredictable, or during winter when many of the specifically birdpollinated plants flower. Birds may also increase the chance of outcrossing as they fly further between plants than insects. Nutrients are often limiting in Australian ecosystems, whereas energy rarely is. Therefore, massive nectar production is unlikely to place a strain on plants, unless water is scarce. Finally, it is possible that birds may provide a service in addition to pollination, they may protect the plant from herbivorous insects.