A new look at phenotypic disparity and diversification rates in island plant radiations

Baldwin, Bruce G.

doi:10.1111/nph.15961

Cited by 4 publications

(5 citation statements)

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“…Our observation that some insular woody lineages do not diversify, whereas others undergo spectacular radiations [e.g., Cyrtandra with 245 species ( 27 )], shows that other traits than IW must play an important role in their diversification. Identifying traits that promote diversification remains a challenge in evolutionary biology ( 23 , 50 ), but there is growing evidence that hybridization—which can be regarded as the most extreme form of outcrossing and may overcome loss of genetic variation via founder effects in the colonizing population—is a promising candidate ( 51 , 52 ).…”

Section: Discussionmentioning

confidence: 99%

The evolution of insular woodiness

Zizka

Onstein

Rozzi

et al. 2022

Proc. Natl. Acad. Sci. U.S.A.

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Insular woodiness (IW)—the evolutionary transition from herbaceousness toward woodiness on islands—is one of the most iconic features of island floras. Since pioneering work by Darwin and Wallace, a number of drivers of IW have been proposed, such as 1) competition for sunlight requiring plants with taller and stronger woody stems and 2) drought favoring woodiness to safeguard root-to-shoot water transport. Alternatively, IW may be the indirect result of increased lifespan related to 3) a favorable aseasonal climate and/or 4) a lack of large native herbivores. However, information on the occurrence of IW is fragmented, hampering tests of these potential drivers. Here, we identify 1,097 insular woody species on 375 islands and infer at least 175 evolutionary transitions on 31 archipelagos, concentrated in six angiosperm families. Structural equation models reveal that the insular woody species richness on oceanic islands correlates with a favorable aseasonal climate, followed by increased drought and island isolation (approximating competition). When continental islands are also included, reduced herbivory pressure by large native mammals, increased drought, and island isolation are most relevant. Our results illustrate different trajectories leading to rampant convergent evolution toward IW and further emphasize archipelagos as natural laboratories of evolution, where similar abiotic or biotic conditions replicated evolution of similar traits.

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Section: Discussionmentioning

confidence: 99%

The evolution of insular woodiness

Zizka

Onstein

Rozzi

et al. 2022

Proc. Natl. Acad. Sci. U.S.A.

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“…In addition to the environmental conditions potentially favouring the evolution to IW on a specific archipelago, intrinsic aspects of the herbaceous colonizing population are important to determine whether this lineage has the potential to develop IW 36 . For instance, monocots never produce wood 37,38 , implying that IW is per definition not possible.…”

Section: Discussionmentioning

confidence: 99%

“…Our observation that some insular woody lineages do not diversify whereas others undergo spectacular radiations (e.g., Cyrtandra with 245 species 27 ) show that other traits than IW must play an important role in island diversification. Identifying traits that promote diversification remains one of the unresolved key questions in evolutionary biology 25,39 , but there is growing evidence that hybridization-which can be regarded as the most extreme form of outcrossing and may overcome loss of genetic variation via founder effects in the colonizing population-is a promising candidate 36,40 .…”

Section: Discussionmentioning

confidence: 99%

Plant longevity, drought and island isolation favoured rampant evolutionary transitions towards insular woodiness

Zizka

Onstein

Rozzi

et al. 2022

Preprint

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Insular woodiness (IW)-the evolutionary transition from herbaceousness towards woodiness on islands-is one of the most iconic features of island floras. Since pioneering work by Darwin and Wallace, five IW drivers have been proposed: (i) favourable aseasonal climate and (ii) lack of large native herbivores promote plant longevity that (iii) results in prolonged flowering favouring outcrossing. Alternatively, (iv) competition for sunlight requires taller and stronger stems, and (v) drought favours woodiness to safeguard root-to-shoot water transport. However, information on the occurrence of IW is fragmented, hampering tests of these potential drivers. Here, we identify 1,097 insular woody species (IWS) on 375 islands, and infer at least 175 evolutionary transitions on 31 archipelagos, concentrated in six angiosperm families. Structural equation models reveal that the IWS richness on oceanic islands correlates with aseasonal favourable climate, followed by increased drought and island isolation (approximating competition). When continental islands are included, reduced herbivory pressure by large native mammals, increased drought and island isolation are most relevant. The repeated evolution of IW opens promising avenues to disentangle the variation in gene regulatory networks triggering wood formation, and emphasize individual archipelagos as laboratories of evolution, where similar environmental conditions replicate convergent evolution of similar traits.

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“…However, deposits were recorded over almost the whole island, indicating that longer lasting or more intense eruptions would severely affect an even larger area. Such events have been hitherto ignored in the intensely discussed "island woodiness" debate 21,[23][24][25][26][27] . We found surviving populations of endemic woody taxa heavily impacted by tephra deposits close to lava flows, across a wide range of genera such as Rumex (R. lunaria), Echium (E. brevirame), Euphorbia (E. lamarckii, E. canariensis and E. balsamifera), Aeonium (A. davidbramwellii), Rubia (R. fruticosa), Schizogyne (S. sericea), Carlina (C. falcata) or Sonchus (S. hierrensis) (Table S2), which coincide with the general list of woody Canary plants 20 .…”

Section: Discussionmentioning

confidence: 99%

The fate of terrestrial biodiversity during an oceanic island volcanic eruption

Nogales

Guerrero-Campos

Boulesteix

et al. 2022

Sci Rep

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Volcanic activity provides a unique opportunity to study the ecological responses of organisms to catastrophic environmental destruction as an essential driver of biodiversity change on islands. However, despite this great scientific interest, no study of the biodiversity at an erupting volcano has yet been undertaken. On La Palma (Canary archipelago), we quantified the main species affected and their fate during the 85-day eruption (September–December 2021). Our main objective consisted of monitoring the biodiversity subjected to critical stress during this volcanic eruption. We found that all biodiversity within a 2.5 km radius was severely affected after the first two weeks. It is challenging to assess whether volcanism can drive evolutionary traits of insular organisms. Examples are the adaptation of an endemic conifer to high temperatures, selection of functional plant types—secondary woodiness—, effects of the disappearance of invertebrates and their influence in trophic nets and vertebrate trophic plasticity. However, our data suggest that such previous evolutionary changes might continue to favour their resilience during this eruption. Lastly, it is a very good opportunity to assess the extent to which these periodic volcanic catastrophes may constitute temporary windows of repeated opportunities for the evolution and speciation of oceanic island biota.

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A new look at phenotypic disparity and diversification rates in island plant radiations

Abstract: This article is a Commentary on Nürk et al. 224: 518–531.

Cited by 4 publications

References 35 publications

The evolution of insular woodiness

The evolution of insular woodiness

Plant longevity, drought and island isolation favoured rampant evolutionary transitions towards insular woodiness

The fate of terrestrial biodiversity during an oceanic island volcanic eruption

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