scholarly journals Ecological speciation in Darwin’s finches: Parsing the effects of magic traits

2013 ◽  
Vol 59 (1) ◽  
pp. 8-19 ◽  
Author(s):  
Jeffrey Podos ◽  
Rie Dybboe ◽  
Mads Ole Jensen
Keyword(s):  
Assortative Mating ◽  
Mate Recognition ◽  
Ecological Speciation ◽  
Santa Cruz ◽  
Darwin's Finches ◽  
Relative Contribution ◽  
Darwin’S Finches ◽  
Song Divergence ◽  
Recognition Systems ◽  
Geospiza Fortis

Abstract Many recent studies of ecological speciation have focused on “magic trait” scenarios, in which divergent selection on viability traits leads inextricably to corresponding divergence in mechanisms, especially mate recognition systems, that facilitate assortative mating. Speciation however may also proceed via other scenarios, such as when populations experience directly selected or random divergence in mate recognition systems. The relative contributions of magic trait versus other scenarios for speciation remain virtually unexplored. The present study aims to test the relative contribution of the magic trait scenario in the divergence of populations of the medium ground finch Geospiza fortis of Santa Cruz Island, Galapagos. First, we assess differences in G. fortis song between a northern population (Borrero Bay) and a southeastern population (El Garrapatero), differences that we propose (along with other within-island geographic song variations) have arisen via scenarios that do not involve a magic trait scenario. Pairwise comparisons of raw and composite (PC) song parameters, as well as discriminant functions analyses, reveal significant patterns of song divergence between sites. Second, we test the ability of territorial males at Borrero Bay to discriminate songs from the two sites. We find that G. fortis males can discriminate within-island song variants, responding more strongly to local than to “foreign” songs, along 3 raw and 1 composite response measures. Third, we compare these findings to prior data sets on song divergence and discrimination in Santa Cruz G. fortis. These comparisons suggest that song divergence and discrimination are shaped less strongly by geographic sources than by morphological (beak-related) sources. We thus argue that interpopulation song divergence and discrimination, fundamental elements of assortative mating in Darwin’s finches, can be fostered in early stages of divergence under magic trait as well as alternative scenarios for speciation, but with more emphasis on the magic trait scenario, at least for this species on this island.

scholarly journals Isotopic Niche Segregation among Darwin’s Finches on Santa Cruz Island, Galápagos

Diversity ◽  
2021 ◽  
Vol 13 (4) ◽  
pp. 147
Author(s):  
Mariana Villegas ◽  
Catherine Soos ◽  
Gustavo Jiménez-Uzcátegui ◽  
Shukri Matan ◽  
Keith A. Hobson
Keyword(s):  
Three Dimensional ◽  
Sympatric Species ◽  
Isotopic Niche ◽  
Museum Specimens ◽  
Santa Cruz Island ◽  
Santa Cruz ◽  
Δ13c And Δ15n ◽  
Darwin's Finches ◽  
Darwin’S Finches ◽  
Foraging Guilds

Darwin’s finches are a classic example of adaptive radiation involving differential use of dietary resources among sympatric species. Here, we apply stable isotope (δ13C, δ15N, and δ2H) analyses of feathers to examine ecological segregation among eight Darwin’s finch species in Santa Cruz Island, Galápagos collected from live birds and museum specimens (1962–2019). We found that δ13C values were higher for the granivorous and herbivorous foraging guilds, and lower for the insectivorous finches. Values of δ15N were similar among foraging guilds but values of δ2H were higher for insectivores, followed by granivores, and lowest for herbivores. The herbivorous guild generally occupied the largest isotopic standard ellipse areas for all isotopic combinations and the insectivorous guild the smallest. Values of δ2H provided better trophic discrimination than those of δ15N possibly due to confounding influences of agricultural inputs of nitrogen. Segregation among guilds was enhanced by portraying guilds in three-dimensional isotope (δ13C, δ15N, and δ2H) space. Values of δ13C and δ15N were higher for feathers of museum specimens than for live birds. We provide evidence that Darwin’s finches on Santa Cruz Island tend to be generalists with overlapping isotopic niches and suggest that dietary overlap may also be more considerable than previously thought.

scholarly journals Distribution and abundance of Darwin’s finches and other land birds on Santa Cruz Island, Galápagos: evidence for declining populations

Oryx ◽  
2011 ◽  
Vol 46 (1) ◽  
pp. 78-86 ◽  
Author(s):  
Michael Dvorak ◽  
Birgit Fessl ◽  
Erwin Nemeth ◽  
Sonia Kleindorfer ◽  
Sabine Tebbich
Keyword(s):  
Critical Factor ◽  
Population Monitoring ◽  
Temporal Analysis ◽  
Native Forest ◽  
Habitat Alteration ◽  
Santa Cruz Island ◽  
Santa Cruz ◽  
Darwin's Finches ◽  
Darwin’S Finches ◽  
Introduced Predators

AbstractPopulation monitoring is a vital tool for conservation management and for testing hypotheses about population trends in changing environments. Darwin’s finches on Santa Cruz Island in the Galápagos archipelago have experienced habitat alteration because of human activity, introduced predators, parasites and disease. We used point counts to conduct systematic quantitative surveys of Darwin’s finches and other land birds between 1997 and 2010. The temporal analysis revealed that six of the nine species investigated declined significantly and that this decline was most pronounced at higher elevations in humid native forest and agricultural areas; the highland areas have been most affected by introduced species or direct human impact. Five of the six declining species are insectivorous, which suggests that changes in insect abundance or insect availability are a critical factor in the declines. Further study is required to test this idea. Other factors including habitat alteration and introduced parasites or pathogens may be contributing to the observed declines.

scholarly journals Adult sex ratio influences mate choice in Darwin’s finches

2019 ◽  
Vol 116 (25) ◽  
pp. 12373-12382 ◽  
Author(s):  
Peter R. Grant ◽  
B. Rosemary Grant
Keyword(s):  
Mate Choice ◽  
Sex Ratio ◽  
Phylogenetic Analyses ◽  
Sex Ratios ◽  
Differential Mortality ◽  
Sexual Imprinting ◽  
Darwin's Finches ◽  
Darwin’S Finches ◽  
Adult Sex Ratio ◽  
Geospiza Fortis

The adult sex ratio (ASR) is an important property of populations. Comparative phylogenetic analyses have shown that unequal sex ratios are associated with the frequency of changing mates, extrapair mating (EPM), mating system and parental care, sex-specific survival, and population dynamics. Comparative demographic analyses are needed to validate the inferences, and to identify the causes and consequences of sex ratio inequalities in changing environments. We tested expected consequences of biased sex ratios in two species of Darwin’s finches in the Galápagos, where annual variation in rainfall, food supply, and survival is pronounced. Environmental perturbations cause sex ratios to become strongly male-biased, and when this happens, females have increased opportunities to choose high-quality males. The choice of a mate is influenced by early experience of parental morphology (sexual imprinting), and since morphological traits are highly heritable, mate choice is expressed as a positive correlation between mates. The expected assortative mating was demonstrated when theGeospiza scandenspopulation was strongly male-biased, and not present in the contemporaryGeospiza fortispopulation with an equal sex ratio. Initial effects of parental imprinting were subsequently overridden by other factors when females changed mates, some repeatedly. Females of both species were more frequently polyandrous in male-biased populations, and fledged more offspring by changing mates. The ASR ratio indirectly affected the frequency of EPM (and hybridization), but this did not lead to social mate choice. The study provides a strong demonstration of how mating patterns change when environmental fluctuations lead to altered sex ratios through differential mortality.

scholarly journals Reproductive isolation of sympatric morphs in a population of Darwin's finches

2007 ◽  
Vol 274 (1619) ◽  
pp. 1709-1714 ◽  
Author(s):  
Sarah K Huber ◽  
Luis Fernando De León ◽  
Andrew P Hendry ◽  
Eldredge Bermingham ◽  
Jeffrey Podos
Keyword(s):  
Strong Support ◽  
Darwin's Finches ◽  
Early Stages ◽  
Darwin’S Finches ◽  
Ecological Resources ◽  
Geospiza Fortis ◽  
Breeding Seasons ◽  
Assortative Pairing ◽  
Sympatric Morphs

Recent research on speciation has identified a central role for ecological divergence, which can initiate speciation when (i) subsets of a species or population evolve to specialize on different ecological resources and (ii) the resulting phenotypic modes become reproductively isolated. Empirical evidence for these two processes working in conjunction, particularly during the early stages of divergence, has been limited. We recently described a population of the medium ground finch, Geospiza fortis , that features large and small beak morphs with relatively few intermediates. As in other Darwin's finches of the Galápagos Islands, these morphs presumably diverged in response to variation in local food availability and inter- or intraspecific competition. We here demonstrate that the two morphs show strong positive assortative pairing, a pattern that holds over three breeding seasons and during both dry and wet conditions. We also document restrictions on gene flow between the morphs, as revealed by genetic variation at 10 microsatellite loci. Our results provide strong support for the central role of ecology during the early stages of adaptive radiation.

scholarly journals Host phylogeny, diet, and habitat differentiate the gut microbiomes of Darwin’s finches on Santa Cruz Island

2019 ◽  
Vol 9 (1) ◽  
Author(s):  
Wesley T. Loo ◽  
Jefferson García-Loor ◽  
Rachael Y. Dudaniec ◽  
Sonia Kleindorfer ◽  
Colleen M. Cavanaugh
Keyword(s):  
Evolutionary History ◽  
Environmental Filtering ◽  
Ecological Niches ◽  
Santa Cruz Island ◽  
Santa Cruz ◽  
Darwin's Finches ◽  
Bacterial Phyla ◽  
Dietary Preferences ◽  
Darwin’S Finches ◽  
Host Phylogeny

AbstractDarwin’s finches are an iconic example of an adaptive radiation with well-characterized evolutionary history, dietary preferences, and biogeography, offering an unparalleled opportunity to disentangle effects of evolutionary history on host microbiome from other factors like diet and habitat. Here, we characterize the gut microbiome in Darwin’s finches, comparing nine species that occupy diverse ecological niches on Santa Cruz island. The finch phylogeny showed moderate congruence with the microbiome, which was comprised mostly of the bacterial phyla Firmicutes, Actinobacteria, and Proteobacteria. Diet, as measured with stable isotope values and foraging observations, also correlated with microbiome differentiation. Additionally, each gut microbial community could easily be classified by the habitat of origin independent of host species. Altogether, these findings are consistent with a model of microbiome assembly in which environmental filtering via diet and habitat are primary determinants of the bacterial taxa present with lesser influence from the evolutionary history between finch species.

scholarly journals Ecoimmunity in Darwin's Finches: Invasive Parasites Trigger Acquired Immunity in the Medium Ground Finch (Geospiza fortis)

PLoS ONE ◽  
2010 ◽  
Vol 5 (1) ◽  
pp. e8605 ◽  
Author(s):  
Sarah K. Huber ◽  
Jeb P. Owen ◽  
Jennifer A. H. Koop ◽  
Marisa O. King ◽  
Peter R. Grant ◽  
...  
Keyword(s):  
Acquired Immunity ◽  
Darwin's Finches ◽  
Darwin’S Finches ◽  
Geospiza Fortis

scholarly journals The relationship between intraspecific assortative mating and reproductive isolation between divergent populations

2012 ◽  
Vol 58 (3) ◽  
pp. 484-492 ◽  
Author(s):  
Daniel I. Bolnick ◽  
Mark Kirkpatrick
Keyword(s):  
Mate Choice ◽  
Reproductive Isolation ◽  
Assortative Mating ◽  
Empirical Data ◽  
Gasterosteus Aculeatus ◽  
Threespine Stickleback ◽  
Darwin's Finches ◽  
Phenotypic Divergence ◽  
Darwin’S Finches ◽  
The Relationship

Abstract The term ‘assortative mating’ has been applied to describe two very different phenomena: (1) the tendency for individuals to choose phenotypically similar mates from among conspecifics; or (2) the tendency to prefer conspecific over hete-rospecific mates (behavioral reproductive isolation). Both forms of assortative mating are widespread in nature, but the relationship between these behaviors remains unclear. Namely, it is plausible that a preference for phenotypically similar conspecifics incidentally reduces the probability of mating with phenotypically divergent heterospecifics. We present a model to calculate how the level of reproductive isolation depends on intraspecific assortative mating and the phenotypic divergence between species. For empirically reasonable levels of intraspecific assortment on a single trait axis, we show that strong reproductive isolation requires very substantial phenotypic divergence. We illustrate this point by applying our model to empirical data from threespine stickleback Gasterosteus aculeatus and Darwin’s Finches (Geospiza spp). We conclude that typical levels of intraspecific assortment cannot generally be extrapolated to explain levels of interspecific reproductive isolation. Instead, reproductive isolation between species likely arises from different mate choice behaviors, or multivariate assortative mating.

scholarly journals Conspecific versus heterospecific gene exchange between populations of Darwin's finches

2010 ◽  
Vol 365 (1543) ◽  
pp. 1065-1076 ◽  
Author(s):  
Peter R. Grant ◽  
B. Rosemary Grant
Keyword(s):  
Gene Flow ◽  
Introgressive Hybridization ◽  
Small Island ◽  
Gene Exchange ◽  
Darwin's Finches ◽  
Galapagos Archipelago ◽  
Darwin’S Finches ◽  
Large Populations ◽  
Geospiza Fortis ◽  
Neighbouring Island

This study addresses the extent and consequences of gene exchange between populations of Darwin's finches. Four species of ground finches ( Geospiza ) inhabit the small island of Daphne Major in the centre of the Galápagos archipelago. We undertook a study of microsatellite DNA variation at 16 loci in order to quantify gene flow within species owing to immigration and between species owing to hybridization. A combination of pedigrees of observed breeders and assignments of individuals to populations by the program S tructure enabled us to determine the frequency of gene exchange and the island of origin of immigrants in some cases. The relatively large populations of Geospiza fortis and G. scandens receive conspecific immigrants at a rate of less than one per generation. They exchange genes more frequently by rare but repeated hybridization. Effects of heterospecific gene flow from hybridization are not counteracted by lower fitness of the offspring. As a result, the standing genetic variation of the two main resident populations on Daphne Major is enhanced to a greater extent by introgressive hybridization than through breeding with conspecific immigrants. Immigrant G. fuliginosa also breeds with G. fortis . Conspecific immigration was highest in the fourth species, G. magnirostris . This species is much larger than the other three and perhaps for this reason it has not bred with any of them. The source island of most immigrants is probably the neighbouring island of Santa Cruz. Evolutionary change may be inhibited in G. magnirostris by continuing gene flow, but enhanced in G. fortis and G. scandens by introgressive hybridization.

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