Seed mass and plant origin interact to determine species germination patterns

Abstract

1Ongoing changes in temperature and precipitation regime may have strong impact on 2 vulnerable life-history stages such as germination. Differences in germination patterns among 3 species and populations may reflect their adaptation to conditions of their origin or may be 4 determined by the phylogenetic constrains. These two effects are, however, rarely separated. 5 All the germination patterns may also be modified by seed mass. 6 We studied 40 populations of 14 species of Impatiens coming from Himalayas. 7 Germination of seeds of different origin was tested in four target temperatures, three simulating 8 original conditions plus a warmer climate change scenario. We also studied effect of shorter 9 stratification and warmer temperature in combination as another possible effect of climate 10 change. 11Original and target climate interacted and had strong impact on total germination, but 12 not on germination speed and seed dormancy. Interaction between seed mass and original 13 climate indicated different germination strategies in light and heavy seeds. Only seed mass was 14 affected by phylogenetic relationships among the species, while germination response (with 15 exception of T50) was driven primarily by climate of origin. 16This study is the first to show that the effect of seed mass interacts with original climate 17 in determining species germination patterns under changing climate. The differences in seed 18 mass are thus likely crucial for species ability to adapt to novel conditions as seed mass, unlike 19 seed germination patterns, is strongly phylogenetically constrained. Further studies exploring 20 how seed mass modifies species germination under changing climate are needed to confirm 21 generality of these findings. 22 23 24 Kew words: phylogeny, seed mass, reproduction characteristics, original environment, target 25 environment 26 27 65 Seed traits including seed mass are strongly associated with phylogeny (Zhang, Du and 66 Chen 2004) (Moles et al. 2005) (Norden et al. 2009) (Barak et al. 2018). Phylogeny explains 67 considerable part of variance in germination among species (Bu et al. 2008) (Wang et al. 2009) 68 (Xu et al. 2014) (Seglias et al. 2018) and strong phylogenetic signal was found also in seed 69 dormancy traits (Dayrell et al. 2017). The likely cause is that phylogeny imposes limits to 70 variability in reproductive attributes within a clade because of similar developmental and design 71 constraints in related species (Ackerly and Donoghue 1995) (Figueroa and Armesto 2001).72However, to our knowledge, there is only one study focusing on the effects of within genus 73 phylogeny on species germination. It is based on seven species and showed that more closely 74 related species had more similar germination behavior and the authors point out that this subject 75 requires further attention (Carta, Hanson and Muller 2016a). Such knowledge is likely to 76 increase our understanding of evolution of species germination requirements. 77In this study, we explored germination response ...

Plant Origin, but Not Phylogeny, Drive Species Ecophysiological Response to Projected Climate

“…Finally, the absence of phylogenetic signal in our study may also be because the traits we studied are easier to modify than traits showing high phylogenetic conservatism in previous studies. For example, many previous studies showed strong phylogenetic conservatism in seed size (e.g., Zhang et al, 2004;Moles et al, 2005;Barak et al, 2018) and seed size was in fact shown to be highly phylogenetically conserved in another study in the same system of the genus Impatiens (Veselá et al, 2019). Further studies on phylogenetic patterns of eco-physiological traits within a single genus are thus needed to assess the generality of our findings.…”

“…As indicated in the methods, our initial sampling has been much more extensive and majority of our material did not germinate and/or survive the initial stages of plant life. The drivers of germination of this seed material have been explored in our previous study (Veselá et al, 2019). Among others, Veselá et al (2019) demonstrated that seeds experiencing warmer temperature, especially leading to shortening of the stratification period, exhibit lower seed germination.…”

“…The drivers of germination of this seed material have been explored in our previous study (Veselá et al, 2019). Among others, Veselá et al (2019) demonstrated that seeds experiencing warmer temperature, especially leading to shortening of the stratification period, exhibit lower seed germination. This suggests that warming can have negative effects on this part of the life-cycle.…”

“…While we initially collected much larger sample (18 species and 106 populations), many of the seeds showed very low germination and/or extreme seedling mortality, resulting the low final sample size. The determinants of species germination in this system have been in detail explored in our previous study (Veselá et al, 2019) and the issue of low germination and poor seedling survival is also discussed in the discussion. Some of the populations out of the 30 populations used in this study could not be used for all the analyses presented in this paper, so the exact sample size for each trait is described below and shown in detail in Supporting Information 1.…”

Plant origin determines seed mass, seed nutrients and germination behavior of a dominant grass species

“…This result could indicate that carbohydrates are 509 more effectively used in warm target conditions. In our previous study, we showed, that seed 510 mass interacted with original conditions with higher and faster germination in seed coming 511 from warm and dry localities (Veselá et al 2019). In the current study, we observed a similar 512 trend but only for the interaction of seed mass with original temperature and not moisture.…”