Exploiters and exploited: antagonism, mutualism and mimicry in an ecological community

Interactions between species shape the natural world, and range along a continuum from mutualistic (benefitting all parties) to antagonistic (harming at least one party). Typically, interacting species are studied in a pairwise manner, and such studies have yielded a wealth of insights. However, pairwise interactions usually occur within complex webs of interactions between multiple species. We are now in a strong position to move from more reductionist approaches that focus on a pair of species, to scaling up questions and experiments to complex ecological contexts in the wild. In this thesis, I take two approaches to explore a broader context for the ecology and evolution of antagonism. First, I attempt to synthesise our understanding of analogous antagonistic systems, since exploiters and exploited parties exist from sub-cellular to super organismal levels. Second, I focus empirically on a pairwise interaction between a host and its parasite, while situating these interactions within their shared ecological community. My focal system is brood parasitism, the exploitation of a host into raising a parasite’s offspring. I studied fork-tailed drongos Dicrurus adsimilis and their specialist parasite, the African cuckoo Cuculus gularis. The coevolutionary battle between these bird species plays out amid a species-rich ecological community in the miombo woodlands of sub-Saharan Africa. Together with a field team in Choma, Zambia, I conducted experiments investigating how drongos are exploited by cuckoos and nest predators, while simultaneously exploiting other heterospecifics into aiding them to defend their nest. Chapter 1 introduces the rationale of studying antagonism in a broader context. Chapter 2 integrates evidence from diverse antagonistic interactions to argue that a trade off between the quality and vulnerability of victims underpins the decisions of their antagonists. Chapter 3 asks how multiple species in an ecological community shape the use of vocal mimicry in nest defence. I find that drongos use vocal mimicry in response to cuckoos and nest predators, and that this is likely an adaptation to (sometimes deceptively) recruit heterospecifics to assist in nest defence. Chapter 4 asks how species nesting near one another may interact as both mutualists and antagonists. Chapter 5 explores how an ecological community shapes the costs and benefits of cuckoos’ visual mimicry of hawks. I find that hawk-like barring elicits more mobbing from heterospecifics, incurring additional costs of hawk mimicry to the African cuckoo. Chapter 6 asks how victims’ recognition of antagonists changes across life stages, given that cuckoo chicks are suddenly attacked on fledging. These chapters are structured chronologically through the stages of avian brood parasitism, beginning with a parasite choosing its host, followed by front-line defences of hosts to prevent parasitic egg-laying, counter-adaptations by the parasite to bypass these front-line defences, and ending with the parasitic chick fledging from the host nest. I bring my findings together in a final synthesis in Chapter 7, illuminating how a coevolving species pair can both influence and be influenced by its wider ecological community.

Name dc:type.qualificationname

Doctor of Philosophy (PhD)

Level dc:type.qualificationlevel

Doctoral

Grantor dc:publisher.institution

University of Cambridge

Year dc:date.issued

2025

Author dc:creator

• Collins Attwood, Mairenn

Advisor dc:contributor.advisor

• Spottiswoode, Claire

• brood parasitism
• cuckoo
• ecology
• evolution
• fledgling
• mimicry
• multi-species
• vocal mimicry

Licence

• https://www.repository.cam.ac.uk/bitstreams/d773e425-22c8-4b17-9452-03d670d6c626/download
• http://purl.org/NET/rdflicense/allrightsreserved

Language dc:language

eng

Author Identifier

0000-0001-5386-1291

OAI identifier oai:identifier

oai:www.repository.cam.ac.uk:1810/393732