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 ◽  
...  

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.

2018 ◽  
Vol 115 (46) ◽  
pp. E10879-E10887 ◽  
Author(s):  
Peter R. Grant ◽  
B. Rosemary Grant

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.


Evolution ◽  
2004 ◽  
Vol 58 (7) ◽  
pp. 1588 ◽  
Author(s):  
Peter R. Grant ◽  
B. Rosemary Grant ◽  
Jeffrey A. Markert ◽  
Lukas F. Keller ◽  
K. Petren

2010 ◽  
Vol 365 (1543) ◽  
pp. 1093-1098 ◽  
Author(s):  
Joris Soons ◽  
Anthony Herrel ◽  
Annelies Genbrugge ◽  
Peter Aerts ◽  
Jeffrey Podos ◽  
...  

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.


2017 ◽  
Vol 372 (1713) ◽  
pp. 20150481 ◽  
Author(s):  
Masayoshi Tokita ◽  
Wataru Yano ◽  
Helen F. James ◽  
Arhat Abzhanov

Adaptive radiation is the rapid evolution of morphologically and ecologically diverse species from a single ancestor. The two classic examples of adaptive radiation are Darwin's finches and the Hawaiian honeycreepers, which evolved remarkable levels of adaptive cranial morphological variation. To gain new insights into the nature of their diversification, we performed comparative three-dimensional geometric morphometric analyses based on X-ray microcomputed tomography (µCT) scanning of dried cranial skeletons. We show that cranial shapes in both Hawaiian honeycreepers and Coerebinae (Darwin's finches and their close relatives) are much more diverse than in their respective outgroups, but Hawaiian honeycreepers as a group display the highest diversity and disparity of all other bird groups studied. We also report a significant contribution of allometry to skull shape variation, and distinct patterns of evolutionary change in skull morphology in the two lineages of songbirds that underwent adaptive radiation on oceanic islands. These findings help to better understand the nature of adaptive radiations in general and provide a foundation for future investigations on the developmental and molecular mechanisms underlying diversification of these morphologically distinguished groups of birds. This article is part of the themed issue ‘Evo-devo in the genomics era, and the origins of morphological diversity’.


2020 ◽  
Vol 4 (2) ◽  
pp. 270-278 ◽  
Author(s):  
Guillermo Navalón ◽  
Jesús Marugán-Lobón ◽  
Jen A. Bright ◽  
Christopher R. Cooney ◽  
Emily J. Rayfield

2010 ◽  
Vol 365 (1543) ◽  
pp. 1065-1076 ◽  
Author(s):  
Peter R. Grant ◽  
B. Rosemary Grant

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.


2016 ◽  
Vol 371 (1690) ◽  
pp. 20150188 ◽  
Author(s):  
Louis Lefebvre ◽  
Simon Ducatez ◽  
Jean-Nicolas Audet

Several studies on cognition, molecular phylogenetics and taxonomic diversity independently suggest that Darwin's finches are part of a larger clade of speciose, flexible birds, the family Thraupidae , a member of the New World nine-primaried oscine superfamily Emberizoidea . Here, we first present a new, previously unpublished, dataset of feeding innovations covering the Neotropical region and compare the stem clades of Darwin's finches to other neotropical clades at the levels of the subfamily, family and superfamily/order. Both in terms of raw frequency as well as rates corrected for research effort and phylogeny, the family Thraupidae and superfamily Emberizoidea show high levels of innovation, supporting the idea that adaptive radiations are favoured when the ancestral stem species were flexible. Second, we discuss examples of innovation and problem-solving in two opportunistic and tame Emberizoid species, the Barbados bullfinch Loxigilla barbadensis and the Carib grackle Quiscalus lugubris fortirostris in Barbados. We review studies on these two species and argue that a comparison of L. barbadensis with its closest, but very shy and conservative local relative, the black-faced grassquit Tiaris bicolor , might provide key insights into the evolutionary divergence of cognition.


Evolution ◽  
2004 ◽  
Vol 58 (7) ◽  
pp. 1588-1599 ◽  
Author(s):  
Peter R. Grant ◽  
B. Rosemary Grant ◽  
Jeffrey A. Markert ◽  
Lukas F. Keller ◽  
K. Petren

2010 ◽  
Vol 365 (1543) ◽  
pp. 1041-1052 ◽  
Author(s):  
Luis Fernando de León ◽  
Eldredge Bermingham ◽  
Jeffrey Podos ◽  
Andrew P. Hendry

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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