scholarly journals Mechanical stress, fracture risk and beak evolution in Darwin's ground finches ( Geospiza )

2010 ◽  
Vol 365 (1543) ◽  
pp. 1093-1098 ◽  
Author(s):  
Joris Soons ◽  
Anthony Herrel ◽  
Annelies Genbrugge ◽  
Peter Aerts ◽  
Jeffrey Podos ◽  
...  
Keyword(s):  
Common Ancestor ◽  
High Stress ◽  
Natural Populations ◽  
Peak Stress ◽  
Food Type ◽  
Darwin's Finches ◽  
Darwin’S Finches ◽  
Competition For Food ◽  
Selection For ◽  
Beak Size

Darwin's finches have radiated from a common ancestor into 14 descendent species, each specializing on distinct food resources and evolving divergent beak forms. Beak morphology in the ground finches ( Geospiza ) has been shown to evolve via natural selection in response to variation in food type, food availability and interspecific competition for food. From a mechanical perspective, however, beak size and shape are only indirectly related to birds' abilities to crack seeds, and beak form is hypothesized to evolve mainly under selection for fracture avoidance. Here, we test the fracture-avoidance hypothesis using finite-element modelling. We find that across species, mechanical loading is similar and approaches reported values of bone strength, thus suggesting pervasive selection on fracture avoidance. Additionally, deep and wide beaks are better suited for dissipating stress than are more elongate beaks when scaled to common sizes and loadings. Our results illustrate that deep and wide beaks in ground finches enable reduction of areas with high stress and peak stress magnitudes, allowing birds to crack hard seeds while limiting the risk of beak failure. These results may explain strong selection on beak depth and width in natural populations of Darwin's finches.

scholarly journals Role of sexual imprinting in assortative mating and premating isolation in Darwin’s finches

2018 ◽  
Vol 115 (46) ◽  
pp. E10879-E10887 ◽  
Author(s):  
Peter R. Grant ◽  
B. Rosemary Grant
Keyword(s):  
Natural Habitat ◽  
Good Choice ◽  
Premating Isolation ◽  
Sexual Imprinting ◽  
Darwin's Finches ◽  
Darwin’S Finches ◽  
Adaptive Radiations ◽  
Beak Size ◽  
Species Specific

Global biodiversity is being degraded at an unprecedented rate, so it is important to preserve the potential for future speciation. Providing for the future requires understanding speciation as a contemporary ecological process. Phylogenetically young adaptive radiations are a good choice for detailed study because diversification is ongoing. A key question is how incipient species become reproductively isolated from each other. Barriers to gene exchange have been investigated experimentally in the laboratory and in the field, but little information exists from the quantitative study of mating patterns in nature. Although the degree to which genetic variation underlying mate-preference learning is unknown, we provide evidence that two species of Darwin’s finches imprint on morphological cues of their parents and mate assortatively. Statistical evidence of presumed imprinting is stronger for sons than for daughters and is stronger for imprinting on fathers than on mothers. In combination, morphology and species-specific song learned from the father constitute a barrier to interbreeding. The barrier becomes stronger the more the species diverge morphologically and ecologically. It occasionally breaks down, and the species hybridize. Hybridization is most likely to happen when species are similar to each other in adaptive morphological traits, e.g., body size and beak size and shape. Hybridization can lead to the formation of a new species reproductively isolated from the parental species as a result of sexual imprinting. Conservation of sufficiently diverse natural habitat is needed to sustain a large sample of extant biota and preserve the potential for future speciation.

Hybridization fluctuates with rainfall in Darwin’s tree finches

2020 ◽  
Vol 130 (1) ◽  
pp. 79-88
Author(s):  
Sonia Kleindorfer ◽  
Rachael Y Dudaniec
Keyword(s):  
Adaptive Response ◽  
Annual Variation ◽  
Natural Populations ◽  
Critically Endangered ◽  
Annual Rainfall ◽  
Sampling Effort ◽  
Galápagos Islands ◽  
Darwin's Finches ◽  
Darwin’S Finches ◽  
Male Hybrid

Abstract Hybridization in natural populations may be an adaptive response to shifting climatic regimes, but understanding this can be limited by the timing of sampling effort and confident identification of hybrids. On the Galapagos Islands, Darwin’s finches regularly hybridize; the islands also show extreme annual variation in rainfall, but the effect of annual rainfall on the frequency of finch hybridization is little known. Across a 20-year period on Floreana Island, we compare patterns of hybridization in sympatric Darwin’s tree finches (N = 425; Camaryhnchus spp.) and test for an effect of annual rainfall on (1) the frequency of hybrids (C. pauper × C. parvulus) and (2) the percentage of male hybrid birds produced per year (hybrid recruitment). Annual rainfall correlated with recruitment positively for hybrids, negatively for C. parvulus and not at all for C. pauper. Furthermore, the percentage of hybrids (range: 12–56%) and C. parvulus did not change with sampling year, but the critically endangered C. pauper declined. Our findings indicate that hybrid recruitment is recurring and variable according to annual rainfall in Camarhynchus Darwin’s finches.

scholarly journals Video analysis of host–parasite interactions in nests of Darwin’s finches

Oryx ◽  
2010 ◽  
Vol 44 (4) ◽  
pp. 588-594 ◽  
Author(s):  
Jody A. O’Connor ◽  
Jeremy Robertson ◽  
Sonia Kleindorfer
Keyword(s):  
Camera System ◽  
New Host ◽  
Darwin's Finches ◽  
Darwin’S Finches ◽  
In The Wild ◽  
Selection For ◽  
Nest Camera ◽  
Host Parasite ◽  
High Parasite ◽  
Shed Light

AbstractParasites place their hosts under strong selection for adaptive traits that increase parasite resistance. The initial impact of invasive parasites has rarely been observed and can be particularly strong on naïve hosts with limited prior exposure to parasites.Philornis downsiis an introduced fly to the Galapagos Islands whose parasitic larvae cause high mortality in nestlings of Darwin's finches. We used a within-nest camera system and nest monitoring data to examine this new host–parasite interaction in the wild. ManyP. downsiflies entered finch nests with incubated eggs or nestlings but only when parent finches were not present. ParasiticP. downsilarvae were observed to emerge from the nest base at night to feed both internally and externally on nestlings. Adult and nestling Darwin’s finches exhibit grooming and avoidance behaviours in the presence ofP. downsiparasites. Specifically, in nests with high parasite intensity, nestlings increased self-preening behaviour, ate larvae and stood on top of one another. Female finches probed into their nestling’s nares (first instar larvae reside in the nares) and probed into the nest base (second and third larvae reside in the nest base during the day). These findings shed light on the emergence of anti-parasite behaviour as well as host–parasite relationships after recent parasitism in a naïve host.

scholarly journals Darwin's finches - an adaptive radiation constructed from ancestral genetic modules

2021 ◽  
Author(s):  
Carl-Johan Rubin ◽  
Erik D Enbody ◽  
Mariya P Dobreva ◽  
Arkhat Abzhanov ◽  
Brian W Davis ◽  
...  
Keyword(s):  
Environmental Variability ◽  
Phenotypic Diversity ◽  
Introgressive Hybridization ◽  
Ancestral Haplotype ◽  
Darwin's Finches ◽  
Haplotype Blocks ◽  
Darwin’S Finches ◽  
Adaptive Radiations ◽  
Beak Size ◽  
Genomic Regions

Recent adaptive radiations are models for investigating mechanisms contributing to the evolution of biodiversity. An unresolved question is the relative importance of new mutations, ancestral variants, and introgressive hybridization for phenotypic evolution and speciation. Here we address this issue using Darwin's finches, which vary in size from an 8g warbler finch with a pointed beak to a 40g large ground finch with a massive blunt beak. We present a highly contiguous genome assembly for one of the species and investigate the genomic architecture underlying phenotypic diversity in the entire radiation. Admixture mapping for beak and body size in the small, medium and large ground finches revealed 28 loci showing strong genetic differentiation. These loci represent ancestral haplotype blocks with origins as old as the Darwin's finch phylogeny (1-2 million years). Genes expressed in the developing beak are overrepresented in these genomic regions. Frequencies of allelic variants at the 28 loci covary with phenotypic similarities in body and beak size across the Darwin's finch phylogeny. These ancestral haplotypes constitute genetic modules for selection, and act as key determinants of the exceptional phenotypic diversity of Darwin's finches. Such ancestral haplotype blocks can be critical for how species adapt to environmental variability and change.

scholarly journals Divergence with gene flow as facilitated by ecological differences: within-island variation in Darwin's finches

2010 ◽  
Vol 365 (1543) ◽  
pp. 1041-1052 ◽  
Author(s):  
Luis Fernando de León ◽  
Eldredge Bermingham ◽  
Jeffrey Podos ◽  
Andrew P. Hendry
Keyword(s):  
Gene Flow ◽  
Allelic Variation ◽  
Genetic Differences ◽  
Darwin's Finches ◽  
Darwin’S Finches ◽  
The Face ◽  
Beak Size ◽  
Additional Support ◽  
Divergence With Gene Flow ◽  
Ecological Differences

Divergence and speciation can sometimes proceed in the face of, and even be enhanced by, ongoing gene flow. We here study divergence with gene flow in Darwin's finches, focusing on the role of ecological/adaptive differences in maintaining/promoting divergence and reproductive isolation. To this end, we survey allelic variation at 10 microsatellite loci for 989 medium ground finches ( Geospiza fortis ) on Santa Cruz Island, Galápagos. We find only small genetic differences among G. fortis from different sites. We instead find noteworthy genetic differences associated with beak. Moreover, G. fortis at the site with the greatest divergence in beak size also showed the greatest divergence at neutral markers; i.e. the lowest gene flow. Finally, morphological and genetic differentiation between the G. fortis beak-size morphs was intermediate to that between G. fortis and its smaller ( Geospiza fuliginosa ) and larger ( Geospiza magnirostris ) congeners. We conclude that ecological differences associated with beak size (i.e. foraging) influence patterns of gene flow within G. fortis on a single island, providing additional support for ecological speciation in the face of gene flow. Patterns of genetic similarity within and between species also suggest that interspecific hybridization might contribute to the formation of beak-size morphs within G. fortis .

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