Biology subjects

Walter Salzburger

Publications and source records attributed to Walter Salzburger.

4 recordsLinked to original sources

bioRxiv2016

Social selection maintains honesty of a dynamic visual signal in cichlid fish

How honest signals evolve is a question that has been hotly debated by animal communication theoreticians and for which empirical evidence has been difficult to obtain. Theory predicts that, due to strong conflicts of interest, communication in aggressive contexts should be under strong selection for clear and reliable signaling. On the other hand, context-dependent signaling increases cheating opportunities, depending on how senders and receivers use, acquire and process signal information. Using animal signaling theory, theoretical visual models and behavioral experimentation, we characterize and determine proximate honesty mechanisms of the facial coloration in the Princess of Burundi cichlid, Neolamprologus brichardi, a species with complex social interactions. We show that this facial color pattern evolved stable chromatic conspicuousness for efficient transmission in the aquatic environment, while context-dependent plasticity in luminance of the horizontal black stripe element is used to signal switches in aggressive intent. Importantly, using experimental signal manipulation we demonstrate that social selection by receiver retaliation is the mechanism responsible for maintaining signal honesty. We suggest that by affecting the evolution of pigmentation patterns in sexually monochromatic cichlid species, social selection can have potential impacts on diversification dynamics.

Evolutionary Biology↗

bioRxiv2016

Disentangling incomplete lineage sorting and introgression to refine species-tree estimates for Lake Tanganyika cichlid fishes

Adaptive radiation is thought to be responsible for the evolution of a great portion of the past and present diversity of life. Instances of adaptive radiation, characterized by the rapid emergence of an array of species as a consequence to their adaptation to distinct ecological niches, are important study systems in evolutionary biology. However, because of the rapid lineage formation in these groups, and the occurrence of hybridization between the participating species, it is often difficult to reconstruct the phylogenetic history of species that underwent an adaptive radiation. In this study, we present a novel approach for species-tree estimation in rapidly diversifying lineages, where introgression is known to occur, and apply it to a multimarker dataset containing up to 16 specimens per species for a set of 45 species of East African cichlid fishes (522 individuals in total), with a main focus on the cichlid species flock of Lake Tanganyika. We first identified, using age distributions of most recent common ancestors in individual gene trees, those lineages in our dataset that show strong signatures of past introgression. This led us to formulate three hypotheses of introgression between different lineages of Tanganyika cichlids: the ancestor of Boulengerochromini (or of Boulengerochromini and Bathybatini) received genomic material from the derived H-lineage; the common ancestor of Cyprichromini and Perissodini experienced, in turn, introgression from Boulengerochromini and/or Bathybatini; and the Lake Tanganyika Haplochromini and closely related riverine lineages received genetic material from Cyphotilapiini. We then applied the multispecies coalescent model to estimate the species tree of Lake Tanganyika cichlids, but excluded the lineages involved in these introgression events, as the multispecies coalescent model does not incorporate introgression. This resulted in a robust species tree, in which the Lamprologini were placed as sister lineage to the H-lineage (including the Eretmodini), and we identify a series of rapid splitting events at the base of the H-lineage. Divergence ages estimated with the multispecies coalescent model were substantially younger than age estimates based on concatenation, and agree with the geological history of the Great Lakes of East Africa. Finally, we formally tested the three hypotheses of introgression using a likelihood framework, and find strong support for introgression between some of the cichlid tribes of Lake Tanganyika.

Evolutionary Biology↗

bioRxiv2016

Singing above the chorus: cooperative Princess cichlid fish (Neolamprologus pulcher) has high pitch

Teleost fishes not only communicate with well-known visual cues, but also olfactory and acoustic signals. Communicating with sound has advantages, as signals propagate fast, omnidirectionally, around obstacles, and over long distances. Heterogeneous environments might favour multimodal communication, especially in socially complex species, as combination of modalities strengths helps overcome their individual limitations. Cichlid fishes are known to be vocal, but a recent report suggests that this is not the case for the socially complex Princess cichlid Neolamprologus pulcher from Lake Tanganyika. Here we further investigated acoustic communication in this species. Wild and captive N. pulcher produced high frequency sounds (mean: 12 kHz), when stimulated by mirror images. In laboratory experiments, N. pulcher produced distinct two-pulsed calls mostly, but not exclusively, associated with agonistic displays. Our results suggest that male N. pulcher produce more sounds at greater durations than females. Thus, we confirm that the Princess cichlid does not produce low frequency sounds, but does produce high frequency sounds, both in combination with and independent from visual displays, suggesting that sounds are not a by-product of displays. Further studies on the hearing abilities of N. pulcher are needed to clarify if the high-frequency sounds are used in intra-or inter-specific communication.

Animal Behavior and Cognition↗

bioRxiv2016

Bayesian Node Dating based on Probabilities of Fossil Sampling Supports Trans-Atlantic Dispersal of Cichlid Fishes

Divergence-time estimation based on molecular phylogenies and the fossil record has provided insights into fundamental questions of evolutionary biology. In Bayesian node dating, phylogenies are commonly time calibrated through the specification of calibration densities on nodes representing clades with known fossil occurrences. Unfortunately, the optimal shape of these calibration densities is usually unknown and they are therefore often chosen arbitrarily, which directly impacts the reliability of the resulting age estimates. As possible solutions to this problem, two non-exclusive alternative approaches have recently been developed, the \"fossilized birth-death\" model and \"total-evidence dating\". While these approaches have been shown to perform well under certain conditions, they require including all (or a random subset) of the fossils of each clade in the analysis, rather than just relying on the oldest fossils of clades. In addition, both approaches assume that fossil records of different clades in the phylogeny are all the product of the same underlying fossil sampling rate, even though this rate has been shown to differ strongly between higher-level taxa. We here develop a flexible new approach to Bayesian node dating that combines advantages of traditional node dating and the fossilized birth-death model. In our new approach, calibration densities are defined on the basis of first fossil occurrences and sampling rate estimates that can be specified separately for all clades. We verify our approach with a large number of simulated datasets, and compare its performance to that of the fossilized birth-death model. We find that our approach produces reliable age estimates that are robust to model violation, on par with the fossilized birth-death model. By applying our approach to a large dataset including sequence data from over 1000 species of teleost fishes as well as 147 carefully selected fossil constraints, we recover a timeline of teleost diversification that is incompatible with previously assumed vicariant divergences of freshwater fishes. Our results instead provide strong evidence for trans-oceanic dispersal of cichlids and other groups of teleost fishes. (Keywords: node dating; calibration density; relaxed molecular clock; fossil record; Cichlidae; marine dispersal)

Evolutionary Biology↗