Trait relationships across common garden palms and other monocots.

<p>(a) Area-based maximum photosynthetic rate (<i>A</i>_area) versus dark respiration rate (<i>R</i>_area), (b) area-based phosphorus concentration (<i>P</i>_area) versus leaf mass per area (LMA), (c) and <i>R</i>_area versus LMA. Standardized major axis (SMA) regression lines are only shown for significant trends. The differences in SMA regression slope and intercept between common garden palms and other monocots are indicated. ns, <i>P</i> > 0.05, *** <i>P</i> < 0.001.</p

Convergent Evolution towards High Net Carbon Gain Efficiency Contributes to the Shade Tolerance of Palms (Arecaceae)

<div><p>Most palm species occur in the shaded lower strata of tropical rain forests, but how their traits relate to shade adaptation is poorly understood. We hypothesized that palms are adapted to the shade of their native habitats by convergent evolution towards high net carbon gain efficiency (CGE_n), which is given by the maximum photosynthetic rate to dark respiration rate ratio. Leaf mass per area, maximum photosynthetic rate, dark respiration and N and P concentrations were measured in 80 palm species grown in a common garden, and combined with data of 30 palm species growing in their native habitats. Compared to other species from the global leaf economics data, dicotyledonous broad-leaved trees in tropical rainforest or other monocots in the global leaf economics data, palms possessed consistently higher CGE_n, achieved by lowered dark respiration and fairly high foliar P concentration. Combined phylogenetic analyses of evolutionary signal and trait evolution revealed convergent evolution towards high CGE_n in palms. We conclude that high CGE_n is an evolutionary strategy that enables palms to better adapt to shady environments than coexisting dicot tree species, and may convey advantages in competing with them in the tropical forest understory. These findings provide important insights for understanding the evolution and ecology of palms, and for understanding plant shade adaptations of lower rainforest strata. Moreover, given the dominant role of palms in tropical forests, these findings are important for modelling carbon and nutrient cycling in tropical forest ecosystems.</p></div

The dependency of photosynthesis and dark respiration on foliar area-based N (<i>N</i>_area) and P (<i>P</i>_area) across common garden palms, field palms, species from a global dataset and dicotyledonous broad-leaved trees in tropical rain forests (dicot TRF trees).

<p>(a, b) Area-based maximum photosynthetic rate (<i>A</i>_area), (c,d) area-based dark respiration rate (<i>R</i>_area). Relationships in each dataset are significant and their standardized major axis (SMA) regression lines are shown. The differences in SMA regression slope and intercept between common garden palms and two other non-palm datasets are indicated (see <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0140384#pone.0140384.s010" target="_blank">S4 Table</a> for the differences between field palms and two other non-palm datasets). ns, <i>P</i> > 0.05, * <i>P</i> < 0.05, ** <i>P</i> < 0.01, *** <i>P</i> < 0.001.</p

Trait relationships with leaf mass per area (LMA) as a variable across common garden palms, field palms, species from a global dataset and dicotyledonous broad-leaved trees in tropical rain forests (dicot TRF trees).

<p>(a) Area-based nitrogen concentration (<i>N</i>_area), (b) area-based phosphorus concentration (<i>P</i>_area), (c) area-based maximum photosynthetic rate (<i>A</i>_area), (d) area-based dark respiration (<i>R</i>_area), (e) net carbon gain efficiency (CGE_n). Standardized major axis (SMA) regression lines are only shown for significant relationships. The differences in SMA regression slope and intercept between common garden palms and two other non-palm datasets are indicated (see <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0140384#pone.0140384.s010" target="_blank">S4 Table</a> for the differences between field palms and two other non-palm datasets). ns, <i>P</i> > 0.05, ** <i>P</i> < 0.01, *** <i>P</i> < 0.001.</p

Results of a SURFACE analysis of the palm family.

<p>(a) Phylogenetic tree (MCC obtained in BEAST), with surfaceTreePlot painting to highlight convergent (colored) and non-convergent (black/grey) regimes onto branches. Numbers on branches indicate the order in which regime shifts were added during the forward phase. (b) AIC_c plot showing Δk and AIC-changes during forward and backward phases of the SURFACE analysis. (c) and (d) Comparison of convergence between area-based and mass based convergence (<i>A</i>_area vs. <i>R</i>_area, and <i>A</i>_mass vs. <i>R</i>_mass respectively). (e) Results obtained using the null expectation under a non-convergent Hansen model. Note for (c-e) Plots showing trait values for species (small circles) and estimated trait optima (large circles). Regime colors match those used in (a). Palm illustrations from Phylopic.org.</p

Dated Phylogenies of the Sister Genera <i>Macaranga</i> and <i>Mallotus</i> (Euphorbiaceae): Congruence in Historical Biogeographic Patterns?

<div><p>Molecular phylogenies and estimates of divergence times within the sister genera <i>Macaranga</i> and <i>Mallotus</i> were estimated using Bayesian relaxed clock analyses of two generic data sets, one per genus. Both data sets were based on different molecular markers and largely different samples. Per genus three calibration points were utilised. The basal calibration point (crown node of all taxa used) was taken from literature and used for both taxa. The other three calibrations were based on fossils of which two were used per genus. We compared patterns of dispersal and diversification in <i>Macaranga</i> and <i>Mallotus</i> using ancestral area reconstruction in RASP (S-DIVA option) and contrasted our results with biogeographical and geological records to assess accuracy of inferred age estimates. A check of the fossil calibration point showed that the Japanese fossil, used for dating the divergence of <i>Mallotus</i>, probably had to be attached to a lower node, the stem node of all pioneer species, but even then the divergence time was still younger than the estimated age of the fossil. The African (only used in the <i>Macaranga</i> data set) and New Zealand fossils (used for both genera) seemed reliably placed. Our results are in line with existing geological data and the presence of stepping stones that provided dispersal pathways from Borneo to New Guinea-Australia, from Borneo to mainland Asia and additionally at least once to Africa and Madagascar via land and back to India via Indian Ocean island chains. The two genera show congruence in dispersal patterns, which corroborate divergence time estimates, although the overall mode and tempo of dispersal and diversification differ significantly as shown by distribution patterns of extant species.</p></div

Relationships between area-based maximum photosynthetic rate (<i>A</i>_area) and dark respiration rate (<i>R</i>_area) across common garden palms, field palms, species from a global dataset and dicotyledonous broad-leaved trees in tropical rain forests (dicot TRF trees).

<p>Relationships in each dataset are significant and their standardized major axis (SMA) regression lines are shown. The differences in SMA regression slope and intercept between common garden palms and two other non-palm datasets are indicated (see <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0140384#pone.0140384.s010" target="_blank">S4 Table</a> for the differences between field palms and two other non-palm datasets). ns, <i>P</i> > 0.05, *** <i>P</i> < 0.001.</p

Simultaneous dispersal events in the genera <i>Macaranga</i> and <i>Mallotus</i>.

<p>Simultaneous dispersal events in the genera <i>Macaranga</i> and <i>Mallotus</i>.</p

Nodes in the <i>Mallotus</i> phylogeny with their estimated mean ages, their variation (95% highest posterior density interval, HPD) and S-DIVA area optimisations with marginal probabilities (MP), in bold selected ones when various area combinations had the same MP.

<p>Nodes in the <i>Mallotus</i> phylogeny with their estimated mean ages, their variation (95% highest posterior density interval, HPD) and S-DIVA area optimisations with marginal probabilities (MP), in bold selected ones when various area combinations had the same MP.</p

Chronogram resulting from analysis of data set 2 (a large sample of <i>Mallotus</i>) using BEAST.

<p>The three calibration points are indicated with their estimated mean age (circles with numbers). Node bars show the 95% Height of the Posterior Density interval. <i>Hancea</i> and <i>Blumeodendron</i> were used as outgroups.</p