Colonization and diversification in the African ‘sky islands’: insights from fossil‐calibrated molecular dating of <i>Lychnis</i> (Caryophyllaceae)

Gizaw, Abel; Brochmann, Christian; Nemomissa, Sileshi; Wondimu, Tigist; Masao, Catherine Aloyce; Tusiime, Felly Mugizi; Abdi, Ahmed Abdikadir; Oxelman, Bengt; Popp, Magnus; Dimitrov, Dimitar

doi:10.1111/nph.13937

Cited by 41 publications

(45 citation statements)

References 71 publications

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“…Hence, in such a tree line ascent scenario, the total area, and thus also population sizes of alpine and heathland Table S5) species, would shrink, potentially leading to local species extinction as tree lines advance toward isolated mountain tops (cf. Dirnb€ ock, Essl, & Rabitsch, 2011;Gizaw et al, 2016). Studies in the Alps have shown that it is the abandonment of traditional pasture management, rather than increasing temperatures, that is driving the observed tree line ascent there (Braunisch et al, 2016;Carlson, Renaud, Biron, & Choler, 2014).…”

Section: Discussionmentioning

confidence: 99%

Disturbance from traditional fire management in subalpine heathlands increases Afro‐alpine plant resilience to climate change

Johansson

Frisk

Nemomissa

et al. 2018

Global Change Biology

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Species are often controlled by biotic factors such as competition at the warm edge of their distribution range. Disturbances at the treeline, disrupting competitive dominance, may thus enable alpine species to utilize lower altitudes. We searched for evidence for range expansion in grazed, fire-managed Ethiopian subalpine Erica heathlands across a 25-year chronosequence. We examined vascular plant composition in 48 plots (5 × 5 m) across an altitudinal range of 3,465-3,711 m.a.s.l. and analyzed how community composition changed in relation to increasing competition over time (using a Shade index based on Erica shrub height and cover) and altitude. Species' habitats and altitudinal ranges were derived from literature. Time since fire explained more variation (r = .41) in species composition than altitude did (r = .32) in an NMDS analysis. Community-weighted altitudinal optima for species in a plot decreased strongly with increasing shade (GLM, Standardized Regression Coefficient SRC = -.41, p = .003), but increased only weakly with altitude (SRC = .26, p = .054). In other words, young stands were dominated by species with higher altitudinal optima than old stands. Forest species richness increased with Log Shade index (SRC = .12, p = .008), but was unaffected by altitude (SRC = -.07, p = .13). However, richness of alpine and heathland species was not highest in plots with lowest Shade index, but displayed a unimodal pattern with an initial increase, followed by a decrease when shading increased (altitude was not significant). Our results indicate that disturbance from the traditional patch burning increases the available habitat for less competitive high-altitude plants and prevents tree line ascent. Therefore, maintaining, but regulating, the traditional land use increases the Afro-alpine flora's resilience to global warming. However, this system is threatened by a new REDD+ program attempting to increase carbon storage via fire suppression. This study highlights the importance of understanding traditional management regimes for biodiversity conservation in cultural landscapes in an era of global change.

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Section: Discussionmentioning

confidence: 99%

Disturbance from traditional fire management in subalpine heathlands increases Afro‐alpine plant resilience to climate change

Johansson

Frisk

Nemomissa

et al. 2018

Global Change Biology

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“…Second, origins of some species endemic to sky islands can be attributed to environmental and climatic changes (Robin et al, ). In addition, most available studies, based on sequence variations of cytoplasmic DNA and/or internal transcribed spacers, suggested that the radiative diversifications of these sky island species were dated to have occurred during the Pleistocene (Cox et al, ; Salerno et al, ; Gizaw et al, ; Diazgranados & Barber, ) or earlier when the local mountains arose or experienced radical geological oscillations (He & Jiang, ; Mastretta‐Yanes et al, ). However, none of these previous studies used statistical tests to examine how the sky island species diverged or originated, based on genomic data from next‐generation sequencing and the recently developed coalescent approaches.…”

Section: Introductionmentioning

confidence: 99%

Genomic insight into “sky island” species diversification in a mountainous biodiversity hotspot

Zhang

Hao

Guo

et al. 2019

J of Sytematics Evolution

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“Sky island” species diversification contributes greatly to mountainous biodiversity. However, the underlying genomic divergence and the inferred drivers remain largely unknown. In this study, we examined the diversification history of five diploid species with three exclusively endemic to the sky islands (mountains) of the Himalaya–Hengduan Mountains biodiversity hotspot. All of them together comprise a clade of the genus Eutrema (Brassicaceae). We resequenced genomes of multiple individuals of the found populations for each species. We recovered the inconsistent phylogenetic relationships between plastome and nuclear‐genome trees for one species. Based on nuclear population genomic data, we detected high genetic divergence between five species with limited gene flow. Four species seemed to diverge mainly through geographical isolation, whereas one arose through hybrid origin. The origins of the sampled five species were dated to within the late Miocene when mountains were uplifted and climates oscillated. All species decreased their population sizes since the inferred origin of each species initially, but only two of them expanded after the Last Glacial Maximum. Together, these findings suggest that geographic isolation plays an important role in driving the sky island species diversification of the sampled species in addition to the occasional gene flow that might have led to the hybrid origin of some sky island species, similar to the species diversification of sea islands.

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“…The afro-montane forest vegetation alone is more species rich than the ericaceous and afro-alpine vegetation taken together (Hedberg, 1957;Smith & Cleef, 1988;Fjeldså & Lovett, 1997;Gehrke & Linder, 2014). However, except for some mostly afro-alpine plant lineages such as giant senecios (Knox & Palmer, 1995) and giant lobelias (Knox & Palmer, 1998) that became popular examples of sky island radiations, and for some genera showing conspicuously disjunct distributions (e.g., Lychnis L. [Caryophyllaceae]: Popp & al., 2008;Ranunculus L. [Ranunculaceae], Carex L. [Cyperaceae] and Alchemilla L. [Rosaceae]: Gehrke & Linder, 2009;Gehrke & al., 2015), the mountainous floras of tropical Africa remain little studied from a biogeographic and phylogeographical point of view (but see Kebede & al., 2007;Dimitrov & al., 2012;Gizaw & al., 2016a).…”

Section: Introductionmentioning

confidence: 99%

The evolution of afro‐montaneDelphinium(Ranunculaceae): Morphospecies, phylogenetics and biogeography

Chartier

Dreßler

Schönenberger

et al. 2016

TAXON

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The genus Delphinium (Ranunculaceae) consists of ca. 300 species and has a mainly holarctic distribution. Few species have been described from high‐altitude areas in West and East Tropical Africa, where the environmental conditions are mostly temperate‐like. We aim to clarify the taxonomy of these afro‐montane Delphinium species and to understand their evolutionary history in terms of their floral morphology and their phylogenetic and biogeographic relationships. Based on herbarium specimens, we analyze flower shape variation, map the geographic distribution of the morphologically defined taxa and reconstruct the molecular phylogeny of the group. Our quantitative analyses of flower shapes indicate that three species can be defined based on floral morphological traits, hence confirming the latest taxonomic treatment of the group where D. dasycaulon, D. leroyi and D. macrocentrum were described. The examination of herbarium specimens indicates that these three species are almost parapatric. However, their respective monophyly is not supported by molecular data. Considering their relatively young age, the non‐monophyly of each of the three morphospecies could be due to incomplete lineage sorting and/or hybridization events. Alternatively, the transition to the D. leroyi floral morph could be the result of evolutionary convergence in the two main groups of afro‐montane Delphinium driven by similar pollinators in different sky islands of the East African Rift System. We hypothesize that the main branches of the East African Rift System, as physical barriers to dispersal, may have prevented genetic exchange among geographic clusters.

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Colonization and diversification in the African ‘sky islands’: insights from fossil‐calibrated molecular dating of Lychnis (Caryophyllaceae)

Cited by 41 publications

References 71 publications

Disturbance from traditional fire management in subalpine heathlands increases Afro‐alpine plant resilience to climate change

Disturbance from traditional fire management in subalpine heathlands increases Afro‐alpine plant resilience to climate change

Genomic insight into “sky island” species diversification in a mountainous biodiversity hotspot

The evolution of afro‐montaneDelphinium(Ranunculaceae): Morphospecies, phylogenetics and biogeography

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