Biology subjects

Cadena, C. D.

Publications and source records attributed to Cadena, C. D..

5 recordsLinked to original sources

bioRxiv2018

Songs in the understory and colors in the canopy: habitat structure leads to different avian communication strategies in a tropical montane forest

Birds inhabit a variety of habitats and they communicate using primarily visual and acoustic signals; two central hypotheses have been postulated to study the evolution of such a signals. The sensory drive hypothesis posits that variation in the physical properties of habitats leads to variation in natural selection pressures by affecting the ease with which different types of signals are perceived. Assuming that resources are limited for animals, the transfer hypothesis predicts a negative relationship between the investments in different types of signals. We evaluated these two hypotheses in a tropical montane forest bird assemblage. We also postulate a possible interaction between these two hypotheses: we predicted that the negative relationships between signals should be observed only when jointly considering birds from different environments (e.g. understory and canopy) due to the expected differences in communication strategies between habitats. The sensory drive hypothesis was supported by the differences we found between strata in vocal output, patch contrast to background and color conspicuousness, but not for the variables associated to song elaboration and hue disparity. We found support for the transfer hypothesis: birds with colors contrasting less against the background sing more frequently and birds with lower diversity of colors produce longer songs, understory birds showed also a negative relationship between signals, but only when accounting for phylogeny. We found partial support for the interaction between the sensory drive and the transfer hypotheses: hue disparity and vocal output were negatively related only when analyzing together birds from the canopy and the understory, but not when analyzing them separately. We conclude that the study of the evolution of communication signals needs to consider more than one channel and the functional interactions between them. The results of the interaction of optimal signaling strategies in two communication channels in the local habitats where animals signaling, are the patterns of colors and songs we revealed in a tropical montane forest bird assemblage.

evolutionary biology↗

bioRxiv2018

Shallow evolutionary divergence between two Andean hummingbirds: Speciation with gene flow?

Ecological speciation can proceed despite genetic interchange when selection counteracts homogeneizing effects of migration. We tested predictions of this divergence-with-gene-flow model in Coeligena helianthea and C. bonapartei, two parapatric Andean hummigbirds with marked plumage divergence. We sequenced neutral markers (mtDNA and nuclear ultra conserved elements) to examine genetic structure and gene flow, and a candidate gene (MC1R) to assess its role underlying divergence in coloration. We also tested the prediction of Glogers rule that darker forms occur in more humid environments, and compared ecomorphological variables to assess adaptive mechanisms potentially promoting divergence. Genetic differentiation between species was very low and coalescent estimates of migration were consistent with divergence with gene flow. MC1R variation was unrelated to phenotypic differences. Species did not differ in macroclimatic niches but were distinct in ecomorphology. Although we reject adaptation to variation in humidity as the cause of divergence, we hypothesize that speciation likely occurred in the face of gene flow, driven by other ecological pressures or by sexual selection. Marked phenotypic divergence with no neutral genetic differentiation is remarkable for Neotropical birds, and makes C. helianthea and C. bonapartei an appropriate system in which to search for the genetic basis of species differences employing genomics.

evolutionary biology↗

bioRxiv2017

Bird songs on the shelf: assessing vocal activity and output using data hidden in sound archives

Understanding how often do animals emit communication signals is of critical importance to address a variety of research questions in behavioral ecology and sexual selection. However, information on vocal output, a central component of investment in signaling, is lacking for most species employing acoustic communication. Because this lack of information is partly due to logistical and methodological difficulties in monitoring animal signaling over time, developing new approaches to quantify vocal output is of special importance. We asked whether the number of recordings of avian vocalizations in sound archives and the times when such recordings were obtained reflect estimates of vocal output and temporal patterns of vocal activity obtained through systematic monitoring of wild bird populations in tropical forest sites. Based on a sample of 43 montane forest species, we found significant relationships between the number of recordings of species detected through continuous monitoring over several months and the number of recordings archived in sound collections, especially when accounting for the area of distribution of each species. In addition, daily activity patterns based on data collected through continuous monitoring over several days did not differ from those based on recordings archived in sound collections in 12 of 15 species of lowland forest birds. Annual patterns in vocal activity of two species estimated based on recordings in collections closely resembled previously published patterns. We conclude that recordings in sound collections contain valuable yet previously unappreciated information about the vocal output and temporal patterns in vocal activity of birds. This opens the possibility of using sound collections to assess vocal output and to consider it as a variable of interest in studies on the ecology and evolution of birds and other animals that use acoustic signals for communication. We encourage field workers to keep the ears wide open, and the recorders wide ready to record.

zoology↗

bioRxiv2017

An extinct hummingbird species that never was: a cautionary tale about sampling issues in molecular phylogenetics

The Bogota Sunangel (Heliangelus zusii) was described based on a historical specimen lacking locality data as a striking-and potentially extinct- new species of hummingbird more than two decades ago. However, it was considered a dubious taxon by some researchers until a molecular study with strong species-level taxon sampling revealed its phylogenetic affinities and validated its status as a distinct species. We reanalysed existing mitochondrial DNA data together with a new data set sampling multiple populations of the Long-tailed Sylph (Aglaiocercus kingii), a species broadly distributed in the Andes of South America. In contrast to previous work, we found that H. zusii shares a haplotype with specimens of A. kingii from the Eastern Cordillera of Colombia, which is phylogenetically nested within a clade formed by populations of A. kingii from the Colombian Andes. These results suggest that H. zusii is not a distinct species, but is most likely the result of hybridization between a female A. kingii and a male of another hummingbird species. These findings highlight the importance of thorough taxonomic and geographic sampling when assessing the likelihood of hybrid origin of an organism, particularly in cases potentially involving wide-ranging species in areas where deep phylogeographic structure is likely.

evolutionary biology↗

bioRxiv2017

Atlantean Evolution in Darwin’s Finches—Issues and Perspectives in Species Delimitation using Phenotypic Data

Progress in the development and use of methods for species delimitation employing phenotypic data lags behind conceptual and practical advances in molecular genetic approaches. The basic evolutionary model underlying the use of phenotypic data to delimit species assumes random mating and quantitative polygenic traits, so that phenotypic distributions within a species should be approximately normal for individuals of the same sex and age. Accordingly, two or more distinct normal distributions of phenotypic traits suggest the existence of multiple species. In light of this model, we show that analytical approaches employed in taxonomic studies using phenotypic data are often compromised by three issues: (1) reliance on graphical analyses of phenotypic space that do not consider the frequency of phenotypes; (2)exclusion of characters potentially important for species delimitation following reduction of data dimensionality; and (3) use of measures of central tendencies to evaluate phenotypic distinctiveness. We outline approaches to overcome these issues based on statistical developments related to normal mixture models and illustrate them empirically with a reanalysis of morphological data recently used to claim that there are no morphologically distinct species of Darwins ground-finches (Geospiza). We found negligible support for this claim relative to taxonomic hypotheses recognizing multiple species. Although species limits among ground-finches merit further assessments using additional sources of information, our results bear implications for other areas of inquiry including speciation research: because ground-finches have likely speciated and are not trapped in a process of \"Sisyphean\" evolution as recently argued, they remain useful models to understand the evolutionary forces involved in speciation. Our work underscores the importance of statistical approaches grounded on appropriate evolutionary models for species delimitation. Approaches allowing one to fit normal mixture models without a priori information about species limits offer new perspectives in the kind of inferences available to systematists, with significant repercusions on ideas about the structure of biological biodiversity. [morphology; normal mixture model; phenotype; principal components analysis; species limits; variable selection.]

evolutionary biology↗