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 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 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 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.

Hybridization of Darwin’s finches on Isla Daphne Major, Galápagos

1993 ◽  
Vol 340 (1291) ◽  
pp. 127-139 ◽  
Keyword(s):  
Common Species ◽  
Biological Species ◽  
Natural Hybridization ◽  
Biological Species Concept ◽  
Darwin's Finches ◽  
The Past ◽  
Breeding Populations ◽  
Darwin’S Finches ◽  
Morphological Criteria ◽  
Geospiza Fortis

There has been much debate in the past about whether Darwin’s finches hybridize in nature, and if they do whether hybridization could account for the intermediate appearance of certain forms. To resolve these issues the breeding of all finches on the small Galápagos island of Daphne Major was studied in every year from 1976 to 1992. The island supported breeding populations of Geospiza fortis (harmonic mean of 198 breeding individuals), G. scandens ( H = 80), G. fuliginosa ( H = 3) and, in the past 10 years, G. magnirostris ( H = 6). Morphological criteria for defining species were developed in a study of the finches on the neighboring large island of Santa Cruz. These were then used with modification on Daphne to classify members of the first few generations to species. Observations of breeding birds showed that in a few cases species interbred. G. fortis hybridized with G. fuliginosa in 11 out of the 13 years in which both species bred. G. fortis and G. scandens hybridized in six of the years. Hybridization was always rare. Hybridizing individuals constituted 1.8% of breeding G. fortis , on average, 0.8% of G. scandens , but 73.0% of the much rarer G. fuliginosa . F 1 hybrids were viable and fertile. They rarely bred with each other to produce an F 2 generation. Much more frequently they backcrossed to the common species, G. fortis and G. scandens . In all these cases hatching and fledging success were high, giving scarcely any indication of genetic incompatibilities in the F 1 , F 2 or backcross generations. The demonstration of natural hybridization answers some questions and raises others. It shows that introgression of genes could be a small factor contributing to the interm ediate appearance of G. fortis on Daphne Major: that is between typically larger forms of this species elsewhere in the archipelago and the smaller G. fuliginosa . However hybridization with the larger G. scandens has the opposite directional effect on G. fortis . Hybridization and introgression sometimes complement the effects of natural selection, sometimes they are opposed by it. Introgression also contributes to the large morphological variation displayed by this and several other populations in the archipelago. Hybridization raises questions about how species of Darwin’s finches (and other organisms) should be defined and recognized. In terms of the broad biological species concept there are four species of finches on Daphne Major, neither completely independent evolutionarily on the one hand (except for G. magnirostris , nor approaching panmixia on the other hand.

scholarly journals Persistence of song types in Darwin's finches, Geospiza fortis , over four decades

2010 ◽  
Vol 6 (5) ◽  
pp. 589-592 ◽  
Author(s):  
Eben Goodale ◽  
Jeffrey Podos
Keyword(s):  
Cultural Evolution ◽  
Sampling Period ◽  
Time Frame ◽  
Bird Songs ◽  
Song Structure ◽  
Darwin's Finches ◽  
Darwin’S Finches ◽  
The Face ◽  
Geospiza Fortis ◽  
Song Types

Learned bird songs evolve via cultural evolution, with song patterns transmitted across generations by imitative learning. In Darwin's finches of the Galápagos Islands, males learn songs from their fathers, and song types can be maintained across multiple generations. However, little is known about the time frame over which specific song types are preserved, in the face of copy errors and corresponding modifications to song structure. Here we investigate cultural evolution in songs of male Geospiza fortis , at Academy Bay, Santa Cruz Island, comparing songs recorded in 1961 by R. Bowman (20 individuals) to those recorded in 1999 by J. Podos (16 individuals). For each individual, we characterized four timing and six frequency parameters, and assessed inter-individual variation in song structure using multivariate analysis. Several 1961 song types persisted into 1999, some with remarkable fidelity. Variation among song types was extensive during both years, and we detected no changes in 10 vocal parameters across the sampling period. These results illustrate temporal continuity in a culturally acquired trait, and raise questions about mechanisms that promote stability in song structure.

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