Paul Handford

SOUND DESIGN FOR VOCALIZATIONS: QUALITY IN THE WOODS, CONSISTENCY IN THE FIELDS

Abstract The acoustic adaptation hypothesis (AAH) predicts that vocalizations intended for unambiguous long range communication should possess amplitude modulation (AM) characteristics such that the temporal patterning of amplitude degrades less than alternative patterns during transmission through native habitat. The specific predictions are that open habitat signals should be structured as rapid AM trills, whereas closed habitat signals should be structured as low-rate AM tonal whistles. To investigate the benefit of trill- and whistle-structured signals in open and closed habitats, respectively, a high and low carrier frequency set of four synthetic signals which ranged from rapid AM trills to low rate AM whistles were transmitted 3 hours after sunrise through five different habitat types ranging from closed mature forest to open grassland. Results indicate that, on average, whistles degrade less than trills in both habitats. Trills benefit in open habitats through their tendency to be received with a more consistent quality than whistles. Such differences in transmission consistency among AM patterns are not found in closed habitats. While not degrading less on average, lower frequency signals are received with a more consistent quality than are higher frequency signals of the same AM structure, in both open and closed habitats.

Vegetational correlates of variation in the song of Zonotrichia capensis

Summary1. Geographical variation in the song of Zonotrichia capensis, the Rufous-Collared Sparrow, in northwestern Argentina is discussed. Boundaries between song ‘dialects’ appear to have been stable for at least 10 years. 2. The pattern of song change previously described on a transect across the Aconquija mountains is shown to be duplicated on similar transects elsewhere in these mountains. The association of song types with features of the environment is supported.

Pleistocene climatic cycling and diversification of the Andean treefrog, Hypsiboas andinus

Our understanding of the causes of diversification of Neotropical organisms lags behind that of Northern Hemisphere biota, especially for montane and temperate regions of southern South America. We investigated the mitochondrial DNA genealogical patterns in 262 individuals of the frog Hypsiboas andinus from 26 sites across the eastern ranges of the Andes Mountains in Argentina and Bolivia. Our phylogenetic analyses indicate at least three distinct lineages: one representing H. andinus from Northwestern Argentina and southern Bolivia, at least one H. andinus lineage from northern Bolivia, and one clade containing both H. andinus (from the southern portion of the species range) and its putative sister taxon Hypsiboas riojanus. Hypsiboas andinus samples from northern Bolivia are well differentiated and may represent distinct species. The northern Argentine H. andinus lineage and southern H. andinus /H. riojanus lineage likely diverged between 2 and 6 million years ago; their current sympatry may be the result of secondary contact due to range expansion after isolation during Andean uplift or may reflect cryptic species. Within the geographically extensive northern H. andinus clade, we found significant geographical structuring consistent with historical fragmentation and subsequent range expansion. The timing of this fragmentation and range expansion coincide with the Pleistocene, a time of extensive climatic cycling and vegetational shifts. Average divergence among clades is lower than those found for other Neotropical taxa, highlighting the potential importance of recent climatic history in diversification in the southern Andes.

Morphological variability and enzyme heterozygosity : individual and population level correlations

Negative relationships between the heterozygosity of individual organisms and their deviation from the group mean for morphological traits were first identified in crosses of inbred domestic strains of both plants and animals (Lemer, 1954). Lemer (1954) ascribed these relationships to increased developmental homeostasis among heterozygotes. This hypothesis, however, was based solely on comparisons of morphological variability between highly homozygous inbred lines and highly heterozygous progeny from crosses between lines. More recently, comparisons of morphological variability between groups of individuals from natural populations have also demonstrated lower levels of variability and bilateral asymmetry among more heterozygous individuals (reviewed in Mitton and Grant, 1984; Zouros and Foltz, 1987). These latter results are noteworthy because (1) within natural populations differences among individuals in both heterozygosity and morphology are usually not as great as between inbred and crossed domestic lines, and (2) they suggest that the relationship may be widespread in natural populations and hence of evolutionary importance. Others have sought to explain the phenomenon in terms other than developmental homeostasis: Theoretical models have been formulated that indicate lower phenotypic variation among more heterozygous individuals might be a consequence of the additivity of genic effects for the quantitative character (Chakraborty and Ryman, 1983). Regardless of the mechanism generating the covariation, theoretical studies have implicated increased heterozygosity and decreased morphological variance in heterosis (Turelli and Ginzburg, 1983), and numerous empirical studies of invertebrates have shown higher fitness and/or decreased morphological variance among heterozygotes (reviewed in Mitton and Grant, 1984; Zouros and Foltz, 1987). Far fewer studies have looked for covariation of heterozygosity and morphological variability in vertebrates. Among those that have, many have found no relationship (e.g., 6 of 10 vertebrate

Temporal stability and change in a microgeographical pattern of song variation in the rufous-collared sparrow

We studied the pattern of song variation in the rufous-collared sparrow, Zonotrichia capensis, in the 1987 and 2000 breeding seasons in a 7-km2 area covering open and closed habitats. We measured 14 quantitative song variables over a total of 390 individuals and found consistent differences between habitats in both years. In particular, songs of individuals from closed habitat sites had trills with longer trill intervals and lower frequencies than those of individuals from open habitats. This pattern of variation is interpreted as a song cline that correlates with the environmental gradient. Although this cline was stable in location and shape, it also showed several differences between years. The songs recorded during 2000 had trills with longer trill intervals and lower minimum frequencies than those recorded during 1987. Thus, this study is the first to directly document temporal changes in song variables in a Z. capensis population. This change would be expected if all the habitats studied were more closed in 2000 than in 1987, but we did not find obvious differences in habitat features between seasons. However, this modification of song structure is compatible with alternative explanations, such as subtle differences in habitat characteristics, changes in climatic variables, a delayed effect of a past modification of the environment and neutrality of the change.

Mitochondrial DNA hyperdiversity and vocal dialects in a subspecies transition of the Rufous-collared Sparrow

The Rufous-collared Sparrow, Zonotrichia capensis, is widely distributed in neotropical America and shows extensive variation in its learned song. In northwestern Argentina it exhibits song dialects which map closely onto the distribution of natural vegetation assemblages. To date, there is no evidence ofa correlation between genetic (allozyme) variation and dialects. However, recent genetic structuring produced through philopatry and assortative mating by dialect is difficult to demonstrate statistically with such proteinencoding nuclear genes. Therefore, we assayed variation in more rapidly evolving mitochondrial DNA along a 50 km transect, which spans three dialect boundaries between four adjacent habitat-types (from ~ 1,800 m to ~-3,000 m), using restriction fragment length polymorphism analysis. This revealed exceptional diversity (41 clones from 42 individuals), a level comparable with DNA-fingerprinting, and higher than reported in any passerine over such a small area to date. The degree of nucleotide divergence between the two main clusters of mtDNA haplotypes implies a separation time in excess of one million years. The mtDNA variability is not related to song dialects; rather it is interpreted as a reflection of secondary introgression between two well-differentiated subspecies whose ranges abut in this region.

Continental phylogeography of an ecologically and morphologically diverse Neotropical songbird, Zonotrichia capensis

BackgroundThe Neotropics are exceptionally diverse, containing roughly one third of all extant bird species on Earth. This remarkable species richness is thought to be a consequence of processes associated with both Andean orogenesis throughout the Tertiary, and climatic fluctuations during the Quaternary. Phylogeographic studies allow insights into how such events might have influenced evolutionary trajectories of species and ultimately contribute to a better understanding of speciation. Studies on continentally distributed species are of particular interest because different populations of such taxa may show genetic signatures of events that impacted the continent-wide biota. Here we evaluate the genealogical history of one of the world’s most broadly-distributed and polytypic passerines, the rufous-collared sparrow (Zonotrichia capensis).ResultsWe obtained control region DNA sequences from 92 Zonotrichia capensis individuals sampled across the species’ range (Central and South America). Six additional molecular markers, both nuclear and mitochondrial, were sequenced for a subset of individuals with divergent control region haplotypes. Median-joining network analysis, and Bayesian and maximum parsimony phylogenetic analyses all recovered three lineages: one spanning Middle America, the Dominican Republic, and north-western South America; one encompassing the Dominican Republic, Roraima (Venezuela) and La Paz (Bolivia) south to Tierra del Fuego, Argentina; and a third, including eastern Argentina and Brazil. Phylogenetic analyses suggest that the Middle American/north-western South American clade is sister to the remaining two. Bayesian and maximum likelihood coalescent simulations used to study lineage demographic history, diversification times, migration rates and population expansion together suggested that diversification of the three lineages occurred rapidly during the Pleistocene, with negligible gene flow, leaving genetic signatures of population expansions.ConclusionsThe Pleistocene history of the rufous-collared sparrow involved extensive range expansion from a probable Central American origin. Its remarkable morphological and behavioral diversity probably represents recent responses to local conditions overlying deeper patterns of lineage diversity, which are themselves produced by isolation and the history of colonization of South America.

A molecular phylogeny of the Sierra-Finches (Phrygilus, Passeriformes): extreme polyphyly in a group of Andean specialists.

The unparalleled avian diversity of the Neotropics has long been argued to be in large part the evolutionary consequence of the incredible habitat diversity and rugged topography of the Andes mountains. Various scenarios have been proposed to explain how the Andean context could have generated lineage diversification (e.g. vicariant speciation or parapatric speciation across vertical ecological gradients), yet further study on Andean taxa is needed to reveal the relative importance of the different processes. Here we use mitochondrial and nuclear DNA sequences to derive the first phylogenetic hypothesis for Phrygilus (Sierra-Finches), one of the most species-rich genera of mainly Andean passerines. We find strong evidence that the genus is polyphyletic, comprising four distantly related clades with at least nine other genera interspersed between them (Acanthidops, Catamenia, Diglossa, Haplospiza, Idiopsar, Melanodera, Rowettia, Sicalis and Xenodacnis). These four Phrygilus clades coincide with groups previously established mainly on the basis of plumage characters, suggesting single evolutionary origins for each of these. We consider the history of diversification of each clade, analyzing the timing of splitting events, ancestral reconstruction of altitudinal ranges and current geographical distributions. Phrygilus species origins date mainly to the Pleistocene, with representatives diversifying within, out of, and into the Andes. Finally, we explored whether Phrygilus species, especially those with broad altitudinal and latitudinal Andean distributions, showed phylogeographic structure. Our best-sampled taxon (Phrygilus fruticeti) exhibited no clear pattern; however, we found deep genetic splits within other surveyed species, with Phrygilus unicolor being the most extreme case and deserving of further research.

Systematics of Andean gladiator frogs of the Hypsiboas pulchellus species group (Anura, Hylidae)

Köhler, J., Koscinski, D., Padial, J. M., Chaparro, J. C., Handford, P., Lougheed, S. C. & De la Riva, I. (2010). Systematics of Andean gladiator frogs of the Hypsiboas pulchellus species group (Anura, Hylidae). —Zoologica Scripta, 39, 572–590.

Night songs in the Rufous-collared sparrow

Description sonographique des chants nocturnes chez Zonotrichia capensis hypoleuca et comparaison de ces chants a ceux emis le jour dans les memes endroits