Search

Divergent natural selection should lead to adaptive radiation-that is, the rapid evolution of phenotypic and ecological diversity originating from a single clade. The drivers of adaptive radiation have often been conceptualized through the concept of "adaptive landscapes," yet formal empirical estimates of adaptive landscapes for natural adaptive radiations have proven elusive. Here, we use a 17-year dataset of Darwin's ground finches (Geospiza spp.) at an intensively studied site on Santa Cruz (Galápagos) to estimate individual apparent lifespan in relation to beak traits. We use these estimates to model a multi-species fitness landscape, which we also convert to a formal adaptive landscape. We then assess the correspondence between estimated fitness peaks and observed phenotypes for each of five phenotypic modes (G. fuliginosa, G. fortis [small and large morphotypes], G. magnirostris, and G. scandens). The fitness and adaptive landscapes show 5 and 4 peaks, respectively, and, as expected, the adaptive landscape was smoother than the fitness landscape. Each of the five phenotypic modes appeared reasonably close to the corresponding fitness peak, yet interesting deviations were also documented and examined. By estimating adaptive landscapes in an ongoing adaptive radiation, our study demonstrates their utility as a quantitative tool for exploring and predicting adaptive radiation., (© The Author(s) 2023. Published by Oxford University Press on behalf of The Society for the Study of Evolution (SSE).)

Birds are among nature's most social animals. They are renowned for their group migrations, their cooperative foraging, their communal roosting, their synchronous breeding aggregations, their precise parent-offspring interactions, their coordinated group defenses and their intricate territorial and courtship rituals. In these and other contexts, and indeed in most moments of their lives, birds' capacities to navigate complex social demands and relationships can tip the balance between health or sickness, between reproductive success or failure, between life or death. It is thus no surprise that birds have evolved sophisticated systems for mediating social interactions. Foremost among these are communication signals, most evident in birds as songs, calls, color patterns and postural displays. These and other communication signals can transmit information about a signalers' status, motivations and possible future actions, for sensory and cognitive processing by signal receivers. In general, signals provide benefits for both signal senders and receivers. Consider the bright spring plumage of a male wood warbler who has established a breeding territory. The male's plumage pattern benefits him by signaling his 'ownership' of his territory, which can help him attract potential mates and preempt conflict with potential rivals. His plumage pattern also benefits his intended audiences: it informs females about the signaler's potential as a mate, and it informs other males about the degree of threat they might face were they to attempt a territory take-over. Communication signals are, in essence, a glue that maintains the cohesion of bird societies, and a currency that mediates sophisticated relationships within., Competing Interests: Declaration of interests The authors declare no competing interests., (Copyright © 2022 Elsevier Inc. All rights reserved.)

Mate choice is a primary mechanism driving the evolution of sexually selected traits such as elaborate displays and ornaments. In a majority of taxa studied to date, females are seen to actively sample and evaluate multiple males, presumably to optimize mating opportunities. During this process females may encounter males both familiar and novel, a distinction that might influence how mate choice proceeds. Using a socially monogamous passerine, the blue-black grassquit (Volatinia jacarina), we studied how females respond to novel versus familiar ("paired") males, and how encounters with novel males influence subsequent interactions with their paired males. Additionally, we measured the hormonal response of males after visualizing their paired females interacting with novel males. We found that females were attentive to novel males irrespective of these males' phenotypic attributes, suggesting that in these interactions novelty is highly relevant. After exposure to novel males, females tended to respond aggressively towards their paired males; by contrast, the behaviour of males towards their paired females did not change. Moreover, we did not detect any hormonal responses of males to viewing their paired females interacting with novel males. Together these results suggest that the distinction between familiarity and novelty may hold special relevance for females in mate choice, a finding that bears upon our understanding of the evolution of extra-pair paternity and reproductive behaviour., (Copyright © 2014 Elsevier B.V. All rights reserved.)

1. Previous studies of the Medium Ground Finch,Geospiza fortis, have documented that selection is most severe under drought conditions, which generally favour beaks that are comparatively deep and narrow. Deep beaks are presumed to enhance a bird's ability to crack hard seeds, and narrow beaks have been proposed to enhance a bird's efficiency in manipulating seeds.2. In the present study, we make the first direct measurements of bite force in Darwin's finches. We used 147G. fortisfrom Isla Santa Cruz, Galápagos, to document the influence of beak, head and body dimensions on bite force.3. Among the various beak dimensions, depth, width and shape were all significant predictors of bite force. Among the various head dimensions, width was the best predictor of bite force. Generally low predictive values of multiple regression models including all morphological variables, as well as positive allometric scaling of bite force on head width, suggest an important additional role for variation in muscle architecture or jaw biomechanics in bite force generation.Functional Ecology(2005)19, 43 –48 [ABSTRACT FROM AUTHOR]