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When David beats Goliath: the advantage of large size in interspecific aggressive contests declines over evolutionary time.

ABSTRACT: Body size has long been recognized to play a key role in shaping species interactions. For example, while small species thrive in a diversity of environments, they typically lose aggressive contests for resources with larger species. However, numerous examples exist of smaller species dominating larger species during aggressive interactions, suggesting that the evolution of traits can allow species to overcome the competitive disadvantage of small size. If these traits accumulate as lineages diverge, then the advantage of large size in interspecific aggressive interactions should decline with increased evolutionary distance. We tested this hypothesis using data on the outcomes of 23,362 aggressive interactions among 246 bird species pairs involving vultures at carcasses, hummingbirds at nectar sources, and antbirds and woodcreepers at army ant swarms. We found the advantage of large size declined as species became more evolutionarily divergent, and smaller species were more likely to dominate aggressive contests when interacting with more distantly-related species. These results appear to be caused by both the evolution of traits in smaller species that enhanced their abilities in aggressive contests, and the evolution of traits in larger species that were adaptive for other functions, but compromised their abilities to compete aggressively. Specific traits that may provide advantages to small species in aggressive interactions included well-developed leg musculature and talons, enhanced flight acceleration and maneuverability, novel fighting behaviors, and traits associated with aggression, such as testosterone and muscle development. Traits that may have hindered larger species in aggressive interactions included the evolution of morphologies for tree trunk foraging that compromised performance in aggressive contests away from trunks, and the evolution of migration. Overall, our results suggest that fundamental trade-offs, such as those associated with body size, are more likely to break down over evolutionary time, changing the rules that govern species interactions and structure ecological communities.

SUBMITTER: Martin PR

PROVIDER: S-EPMC4177554 | biostudies-literature | 2014

REPOSITORIES: biostudies-literature

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When David beats Goliath: the advantage of large size in interspecific aggressive contests declines over evolutionary time.

Martin Paul R PR Ghalambor Cameron K CK

PloS one 20140924 9

Body size has long been recognized to play a key role in shaping species interactions. For example, while small species thrive in a diversity of environments, they typically lose aggressive contests for resources with larger species. However, numerous examples exist of smaller species dominating larger species during aggressive interactions, suggesting that the evolution of traits can allow species to overcome the competitive disadvantage of small size. If these traits accumulate as lineages div ...[more]

PMID: 25250781

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Project description:BackgroundTo combat the global challenge of cancer, priority has been placed on the research and development of new cancer medicines (NCMs). NCMs are often approved for marketing in accelerated processes. Despite significant advances in treating cancer, the overall added value and high prices of NCMs has been questioned. While market authorisations for NCMs are granted at the EU level, the assessment of added value, price negotiations and purchase or reimbursement decisions are made by member states. This article explores the practices in Finland for assessing and deciding on purchasing or reimbursing NCMs.MethodsSemi-structured interviews were conducted with 26 civil servants, hospital employees, scientists, and representatives of cancer NGOs and of the pharmaceutical industry in 2019 and 2020. The transcribed interviews were coded inductively using Atlas.ti software and analysed thematically under 3 major themes and 11 sub-themes.ResultsThe clinical value of NCMs is considered to be high, especially regarding NCMs for certain types of cancer. Proper patient selection is important but difficult and not all NCMs can be considered as adding value. The prices are considered to often be very high, leading to concerns about the sustainability and equity of health systems. Equity concerns among cancer patients are raised concerning differences in the availability of NCMs between hospital districts and cost differences for patients between those receiving outpatient and inpatient treatment. The systems and processes in Finland for deciding on the introduction of NCMs are fragmentary, involving separate approaches for outpatient care and hospital medicines by under-resourced evaluation bodies. The scientific evidence available is often limited for evidence-based decisions on introduction. Individual hospital districts sometimes introduce NCMs without assessment by national bodies. This can hamper the proper assessment of some NCMs before their uptake and lead to unequal access to NCMs by hospitals. There is an increasing lack of transparency about pricing, due to the rapid increase of market entry agreements. Lack of transparency on information on prices poses a challenge for authorities responsible for equitable access to cost-effective care within the available resources.ConclusionsRobust reform of the national introductory systems is needed. Internationally, efforts are needed to increase price transparency, to revise incentives within the system of market approval and to accumulate and assess evidence of comparable value and cost-effectiveness after the market approval of NCMs.

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When David beats Goliath: the advantage of large size in interspecific aggressive contests declines over evolutionary time.

Publications

When David beats Goliath: the advantage of large size in interspecific aggressive contests declines over evolutionary time.

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