A comparative analysis of island floras challenges taxonomy‐based biogeographical models of speciation

Igea, Javier; Bogarín, Diego; Papadopulos, Alexander S. T.; Savolainen, Vincent

doi:10.1111/evo.12587

Cited by 30 publications

(22 citation statements)

References 44 publications

(71 reference statements)

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“…However, the phylogenetic placement of C. alfonsiana and C. weatherbyana was ambiguous (Trusty et al 2012). Using the same data set (but analyzed independently), Igea et al (2014) confirmed Trusty's (2012) results, including the ambiguous placement of C. alfonsiana and C. weatherbyana.…”

Section: Introductionsupporting

confidence: 55%

“…The origin of species endemic to islands has long fascinated scientists (Wallace 1880;Keeley and Funk 2011;Tye and Francisco-Ortega 2011;Igea et al 2014). Recent phylogenetic studies have demonstrated that the closest relatives of some island endemics are not always from the mainland but rather from neighboring islands (Sato et al 1999;Motley et al 2005;Harbaugh and Baldwin 2007;Andrus et al 2009;Namoff et al 2010), emphasizing the contributions of both continents and islands to insular biodiversity.…”

Section: Introductionmentioning

confidence: 99%

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Origins of the Endemic Scaly Tree Ferns on the Galápagos and Cocos Islands

Kao

Pryer

Turner

et al. 2015

International Journal of Plant Sciences

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JSTOR is a not-for-profit service that helps scholars, researchers, and students discover, use, and build upon a wide range of content in a trusted digital archive. We use information technology and tools to increase productivity and facilitate new forms of scholarship. For more information about JSTOR, please contact support@jstor.org.. The University of Chicago Press is collaborating with JSTOR to digitize, preserve and extend access to International Journal of Plant Sciences.Editor: Alan W. Meerow Premise of research. Successful long-distance dispersal is rarely observed in scaly tree ferns (Cyatheaceae). Nevertheless, recent molecular evidence has suggested that the four endemic scaly tree ferns on the Galápagos Archipelago (Cyathea weatherbyana) and Cocos Island (Cyathea alfonsiana, Cyathea nesiotica, and Cyathea notabilis), two oceanic island groups west of Central and northern South America, probably each originated from different mainland America ancestors. However, the phylogenetic relationships inferred among these endemics and their mainland relatives have been unclear. This study is aimed at better resolving the relationships and tracing the origins of these island endemics.Methodology. Five plastid regions from 35 Cyathea species were analyzed to reconstruct phylogenetic relationships using parsimony, likelihood, and Bayesian approaches. We also estimated divergence times of these species, and our chronogram was used to reconstruct their biogeographical range history.Pivotal results. Our well-resolved phylogenetic tree of Cyathea, which is in agreement with previous studies, shows that when the four Galápagos and Cocos endemics are included, they each belong to separate subclades. Our biogeographical study suggests that the four endemics originated from independent colonization events from mainland America and that there was no dispersal of Cyathea between the island groups. We reveal more detailed relationships among the endemics and their respective close mainland relatives; some of these relationships differ from previous studies. Our findings are corroborated by new morphological data from ongoing stem anatomy studies.Conclusions. The four scaly tree ferns endemic to the Galápagos and Cocos Islands each did indeed originate as independent colonization events from separate sources in mainland America, and their closest relatives are identified here.

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Section: Introductionsupporting

confidence: 55%

Section: Introductionmentioning

confidence: 99%

Origins of the Endemic Scaly Tree Ferns on the Galápagos and Cocos Islands

Kao

Pryer

Turner

et al. 2015

International Journal of Plant Sciences

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“…Despite intense searches, very few case studies have been able to meet the rigorous criteria for demonstrating sympatric speciation in nature (Coyne and Orr 2004;Bolnick and Fitzpatrick 2007). Even in some of the more convincing examples that do meet these criteria, genomic data have revealed more complex evolutionary histories of multiple colonization and repeated gene flow than previously assumed (Papadopolus et al 2011;The Heliconius Genome Consortium et al 2012;Geiger et al 2013;Alcaide et al 2014;Igea et al 2015;Malinsky et al 2015;Martin et al 2015a;Kautt et al 2016;Poelstra et al 2018).…”

Section: Introductionmentioning

confidence: 99%

Don't throw out the sympatric speciation with the crater lake water: fine-scale investigation of introgression provides equivocal support for causal role of secondary gene flow in one of the clearest examples of sympatric speciation

2018

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Genomic data has revealed complex histories of colonization and repeated gene flow previously unrecognized in some of the most celebrated examples of sympatric speciation and radiation. However, much of the evidence for secondary gene flow into these radiations comes from summary statistics calculated from sparse genomic sampling without knowledge of which specific genomic regions introgressed. This tells us little about how gene flow potentially influenced sympatric diversification. Here, we investigated whole genomes of Barombi Mbo crater lake cichlids for fine‐scale patterns of introgression with neighboring riverine cichlid populations. We found evidence of secondary gene flow into the radiation scattered across <0.24% of the genome; however, from our analyses, it is not clear if the functional diversity in these regions contributed to the ecological, sexual, and morphological diversity found in the lake. Unlike similar studies, we found no obvious candidate genes for adaptive introgression and we cannot rule out that secondary gene flow was predominantly neutral with respect to the diversification process. We also found evidence for differential assortment of ancestral polymorphisms found in riverine populations between sympatric sister species, suggesting the presence of an ancestral hybrid swarm. Although the history of gene flow and colonization is more complicated than previously assumed, the lack of compelling evidence for secondary gene flow's role in species diversification suggests that we should not yet rule out one of the most celebrated examples of sympatric speciation in nature without a more thorough investigation of the timing and functional role of each introgressed region.

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“…Therefore, while knowledge about speciation on islands is constantly improving (e.g. Igea et al , 2015), future simulation studies could investigate to what extent radiation-proneness is lineage-specific (e.g. mediated by common traits).…”

Section: Discussionmentioning

confidence: 99%

Effects of time and isolation on plant diversity: testing island biogeography theory with an eco-evolutionary model

Cabral

Whittaker

Wiegand

et al. 2017

Preprint

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1Aims: The General Dynamic Model of oceanic island biogeography (GDM) predicts how 2 2 biogeographical rates, species richness, and endemism vary depending on island age, area, and 2 3 isolation, based on the interplay of colonization, extinction, and speciation. Here, we used a 2 4 simulation model to test whether GDM predictions may arise from individual-and population-2 5 level processes. 6Location: Hypothetical hotspot islands. 2 7 Methods: Our model (i) considers an idealized island ontogeny, (ii) metabolic constraints, and 2 8 (iii) stochastic, spatially-explicit, and niche-based processes at the level of individuals and 2 9 populations (plant demography, dispersal, competition, mutation, and speciation). Isolation 3 0 scenarios involved varying dispersal ability and distances to mainland. 3 1 Results: Humped temporal trends were obtained for species richness, endemic richness, 3 2 proportion of cladogenetic endemic species, number of radiating lineages, number of species per 3 3 radiating lineage, and biogeographical rates. The proportion of anagenetic endemics and of all 3 4 endemics steadily increased over time. Extinction rates of endemic species peaked later than for 3 5 non-endemic species. Species richness and the number of anagenetic endemics decreased with 3 6 isolation as did rates of colonization, anagenesis, and extinction. The proportion of all endemics 3 7 and of cladogenetic endemics, the number of cladogenetic endemics, of radiating lineages, and of 3 8 species per radiating lineage, and the cladogenesis rate all increased with isolation.3 9 Main conclusions: The results confirm most GDM predictions related to island ontogeny and 4 0 isolation, but predict an increasing proportion of endemics throughout the experiment: a difference 4 1 3 attributable to diverging assumptions on late island ontogeny. New insights regarding the 4 2 extinction trends of endemics further demonstrate how simulation models focusing on low 4 3 ecological levels provide tools to test biogeographical-scale predictions and to develop more 4 4 detailed predictions for further empirical tests.4 5

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A comparative analysis of island floras challenges taxonomy‐based biogeographical models of speciation

Cited by 30 publications

References 44 publications

Origins of the Endemic Scaly Tree Ferns on the Galápagos and Cocos Islands

Origins of the Endemic Scaly Tree Ferns on the Galápagos and Cocos Islands

Don't throw out the sympatric speciation with the crater lake water: fine-scale investigation of introgression provides equivocal support for causal role of secondary gene flow in one of the clearest examples of sympatric speciation

Effects of time and isolation on plant diversity: testing island biogeography theory with an eco-evolutionary model

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