中新世中晚期干旱气候的建立对龙树科物种分化的潜在影响

doi:10.17521/cjpe.2025.0024

摘要/Abstract

摘要：

气候变化在很大程度上影响着生物类群的演化历史, 多肉植物是适应干旱气候条件的特殊植物类群。龙树科含3亚科6属约20种, 均为多肉植物, 分布于非洲大陆南部至东部以及马达加斯加西南部的干旱地区, 然而该科类群物种多样化历程是否与其分布区干旱气候的建立有关, 到目前为止尚不清楚。该研究基于6个叶绿体序列片段(rps16、rpl16、trnL-F、trnT-trnL、trnG-S、trnQ-rps16)构建了该科系统发生关系, 并对该科类群进行了分化时间估算和物种多样化分析。结果表明: 龙树科是一个获得很高支持的单系类群, 该科类群在古新世中期约62.3百万年前(Ma)开始分化, 但物种多样性相对较高的马齿苋树亚科与龙树亚科分别在约14.9 Ma和11.1 Ma才开始分化, 该科类群在约11 Ma出现过分化速率明显增加的情况, 这与其地理分布区在中新世15‒10 Ma期间的干旱气候建立在时间尺度上高度吻合。该研究认为龙树科地理分布区在中新世中晚期干旱气候的建立可能是促进其物种快速分化的潜在环境因子。该研究不仅深化了对龙树科物种多样性演化的认识, 同样增进了对多肉植物类群在时间尺度上进化历史的理解。

关键词: 多肉植物, 龙树科, 分化时间, 系统发育, 物种分化

Abstract:

Aims Climate change has significantly influenced the evolutionary history of various biological groups. Among these, succulents represent special plant groups adapted to arid conditions. Didiereaceae, a small family within Caryophyllales, consist of about 20 species representing 6 genera and 3 subfamilies. Members of this family are succulent plants found in the arid regions across southern to eastern African as well as Madagascar. However, the link between the family’s evolution and the establishment of arid climates in its habitats remains unclear.

Methods In this study, we reconstructed the phylogenetic relationships among Didiereaceae species based on analyses of six plastid DNA markers (rps16, rpl16, trnL-F, trnT-trnL, trnG-S, trnQ-rps16). Additionally, molecular dating and diversification analyses of the family were also conducted.

Important findings The monophyly of Didiereaceae was strongly supported, and a robust phylogenetic framework for the family was established. The crown age of the family was estimated at about 62.3 million years ago (Ma) in the middle Paleocene. However, the two subfamilies (Didiereoideae and Portulacarioideae) with multiple species began to diverge about 11.1 Ma and 14.9 Ma, respectively, during the mid-late Miocene. Results from diversification analysis further revealed an increased diversification rate shift about 11 Ma. These findings align closely with the timing of the establishment of arid climates (15-10 Ma) in the family’s distribution range. Thus, we suggest that the onset of aridity in southern and eastern Africa and Madagascar during the mid-late Miocene likely played a key role in driving species diversification within Didiereaceae. This study enhances our understanding of the evolutionary history of Didiereaceae and contributes to broader knowledge of species diversification patterns in succulent plants.

Key words: succulents, Didiereaceae, divergence time, phylogeny, species diversification

刘子晨, 陈文娜, 黄久香, 李玉玲, 姚纲. 中新世中晚期干旱气候的建立对龙树科物种分化的潜在影响. 植物生态学报, 2026, 50(1): 123-133. DOI: 10.17521/cjpe.2025.0024

LIU Zi-Chen, CHEN Wen-Na, HUANG Jiu-Xiang, LI Yu-Ling, YAO Gang. Potential impact of the establishment of drought climate during the mid-late Miocene on promoting species diversification of Didiereaceae. Chinese Journal of Plant Ecology, 2026, 50(1): 123-133. DOI: 10.17521/cjpe.2025.0024

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链接本文: https://www.plant-ecology.com/CN/10.17521/cjpe.2025.0024

https://www.plant-ecology.com/CN/Y2026/V50/I1/123

图/表 5

表1 取样类群的名称及DNA序列信息

Table 1 Information on taxa name and DNA sequences used

类群 Taxon	trnL-trnF	trnT-trnL	trnG-trnS	trnQ-rps16	rps16	rpl16
直立亚龙木 Alluaudia ascendens	KM261932	KM262007	KM261984	KM261959	KM261907	KM261883
多叶亚龙木1 Alluaudia comosa 1	KM261934	KM262008	KM261986	KM261961	KM261909	KM261885
多叶亚龙木2 Alluaudia comosa 2	KM261933	-	KM261985	KM261960	KM261908	KM261884
丛生亚龙木 Alluaudia dumosa	KM261935	KM262009	KM261987	KM261962	KM261910	KM261886
木竹桃 Alluaudia humbertii	KM261936	-	KM261988	KM261963	KM261911	KM261887
苍岩亚龙木 Alluaudia montagnacii	KM261937	KM262010	KM261989	KM261964	KM261912	KM261888
亚龙木 Alluaudia procera	KM261938	KM262011	KM261990	KM261965	KM261913	KM261889
枝龙木 Alluaudiopsis fiherenensis	KM261939	KM262012	KM261991	KM261966	KM261914	KM261890
双刺枝龙木 Alluaudiopsis marnieriana	KM261940	KM262013	KM261992	KM261967	KM261915	KM261891
缨苋树 Calyptrotheca somalensis	AF094845	AF095914	-	-	-	AF101139
曲龙木 Decarya madagascariensis	KM261941	-	KM261993	KM261968	KM261916	KM261892
刺戟木1 Didierea madagascariensis 1	KM261943	KM262015	KM261995	KM261970	KM261918	KM261894
刺戟木2 Didierea madagascariensis 2	KM261942	KM262014	KM261994	KM261969	KM261917	KM261893
平枝刺戟木 Didierea trollii	KM261944	KM262016	KM261996	KM261971	KM261919	KM261895
马齿苋树 Portulacaria afra	KM261950	KM262022	KM262002	KM261977	KM261925	KM261901
高序苋树 Portulacaria armiana	KM261951	KM262023	KM262003	KM261978	KM261926	KM261902
大叶蜡苋树 Portulacaria carrissoana	KM261945	KM262017	KM261997	KM261972	KM261920	KM261896
灌状蜡苋树 Portulacaria fruticulosa	KM261946	KM262018	KM261998	KM261973	KM261921	KM261897
狭叶蜡苋树 Portulacaria longipedunculata	KM261947	KM262019	KM261999	KM261974	KM261922	KM261898
蜡苋树 Portulacaria namaquensis	KM261948	KM262020	KM262000	KM261975	KM261923	KM261899
矮蜡苋树 Portulacaria pygmaea	KM261949	KM262021	KM262001	KM261976	KM261924	KM261900
落葵薯 Anredera cordifolia	NC_041274	NC_041274	NC_041274	NC_041274	NC_041274	NC_041274
落葵 Basella alba	NC_041293	NC_041293	NC_041293	NC_041293	NC_041293	NC_041293
南荒蓬 Halophytum ameghinoi	NC_040949	NC_040949	NC_040949	NC_040949	NC_040949	NC_040949

表1 取样类群的名称及DNA序列信息

Table 1 Information on taxa name and DNA sequences used

类群 Taxon	trnL-trnF	trnT-trnL	trnG-trnS	trnQ-rps16	rps16	rpl16
直立亚龙木 Alluaudia ascendens	KM261932	KM262007	KM261984	KM261959	KM261907	KM261883
多叶亚龙木1 Alluaudia comosa 1	KM261934	KM262008	KM261986	KM261961	KM261909	KM261885
多叶亚龙木2 Alluaudia comosa 2	KM261933	-	KM261985	KM261960	KM261908	KM261884
丛生亚龙木 Alluaudia dumosa	KM261935	KM262009	KM261987	KM261962	KM261910	KM261886
木竹桃 Alluaudia humbertii	KM261936	-	KM261988	KM261963	KM261911	KM261887
苍岩亚龙木 Alluaudia montagnacii	KM261937	KM262010	KM261989	KM261964	KM261912	KM261888
亚龙木 Alluaudia procera	KM261938	KM262011	KM261990	KM261965	KM261913	KM261889
枝龙木 Alluaudiopsis fiherenensis	KM261939	KM262012	KM261991	KM261966	KM261914	KM261890
双刺枝龙木 Alluaudiopsis marnieriana	KM261940	KM262013	KM261992	KM261967	KM261915	KM261891
缨苋树 Calyptrotheca somalensis	AF094845	AF095914	-	-	-	AF101139
曲龙木 Decarya madagascariensis	KM261941	-	KM261993	KM261968	KM261916	KM261892
刺戟木1 Didierea madagascariensis 1	KM261943	KM262015	KM261995	KM261970	KM261918	KM261894
刺戟木2 Didierea madagascariensis 2	KM261942	KM262014	KM261994	KM261969	KM261917	KM261893
平枝刺戟木 Didierea trollii	KM261944	KM262016	KM261996	KM261971	KM261919	KM261895
马齿苋树 Portulacaria afra	KM261950	KM262022	KM262002	KM261977	KM261925	KM261901
高序苋树 Portulacaria armiana	KM261951	KM262023	KM262003	KM261978	KM261926	KM261902
大叶蜡苋树 Portulacaria carrissoana	KM261945	KM262017	KM261997	KM261972	KM261920	KM261896
灌状蜡苋树 Portulacaria fruticulosa	KM261946	KM262018	KM261998	KM261973	KM261921	KM261897
狭叶蜡苋树 Portulacaria longipedunculata	KM261947	KM262019	KM261999	KM261974	KM261922	KM261898
蜡苋树 Portulacaria namaquensis	KM261948	KM262020	KM262000	KM261975	KM261923	KM261899
矮蜡苋树 Portulacaria pygmaea	KM261949	KM262021	KM262001	KM261976	KM261924	KM261900
落葵薯 Anredera cordifolia	NC_041274	NC_041274	NC_041274	NC_041274	NC_041274	NC_041274
落葵 Basella alba	NC_041293	NC_041293	NC_041293	NC_041293	NC_041293	NC_041293
南荒蓬 Halophytum ameghinoi	NC_040949	NC_040949	NC_040949	NC_040949	NC_040949	NC_040949

表2 龙树科属级物种取样比例

Table 2 Information regarding the taxon sampling fraction for each genus of Didiereaceae

属 Genus	属级物种取样比例 Sampling fraction in genus	属级所有物种数目 Species number accepted in genus
亚龙木属 Alluaudia	1	6
龙树属 Didierea	1	2
曲龙木属 Decarya	1	1
枝龙木属 Alluaudiopsis	1	2
缨苋树属 Calyptrotheca	0.5	2
马齿苋树属 Portulacaria	1	7

图1 基于6个叶绿体序列片段(trnL-trnF、trnT-trnL、trnG-trnS、trnQ-rps16、rps16、rpl16)联合矩阵采用贝叶斯分析所得龙树科系统发生关系。分支节点数据代表“最大似然法自展支持率/贝叶斯后验概率”; -, 该节点关系在最大似然法分析中未获得支持或支持率不足50%。

Fig. 1 Bayesian consensus tree inferred from a combined dataset (including trnL-trnF, trnT-trnL, trnG-trnS, trnQ-rps16, rps16, rpl16). Bootstrap (BS) support value in maximum likelihood (ML) analysis/Posterior probability (PP) in Bayesian inference (BI) are indicated near each phylogenetic node. - indicates the topology was not present in ML analysis or BS value in ML analysis was less than 50%.

图2 龙树科物种直立亚龙木、马齿苋树枝条(示叶片肉质化)以及基于6个叶绿体序列片段联合矩阵与3个时间校准点采用BEAST分析所得龙树科物种水平分化时间图。i-iii为3个时间校准点, 其中i为南荒蓬科干群节点, ii为落葵科干群节点, iii为龙树科冠群节点。橙色条块示中新世中晚期15‒10百万年前(Ma)期间全球性干旱化事件发生的时间区间; 绿色横杠示关键节点分化时间的95%置信区间(95%最大后验密度)。

Fig. 2 Branchlets of Alluaudia ascendens and Portulacaria afra (all have succulent leaves), and the chronogram of Didiereaceae inferred from BEAST analysis of combined dataset (including trnL-trnF, trnT-trnL, trnG-trnS, trnQ-rps16, rps16, rpl16) and three calibrations. Calibration points i‒iii indicate: (i) stem node of Halophytaceae, (ii) stem node of Basellaceae, and (iii) crown node of Didiereaceae. The orange band marks the 15‒10 million years ago (Ma) period of widespread arid climate establishment. Green bars represent 95% highest posterior density (HPD) intervals for divergence ages at key nodes.

图3 基于时间树对龙树科进行物种多样化过程推测的基于宏观进化混合软件的贝叶斯分析(BAMM)分析结果。A, 龙树科Phylorate图, 分支颜色根据物种分化速率变化过程进行标记; 红点暗示该分支存在分化速率明显增加的转变波动。B, 龙树科物种形成速率、物种灭绝速率以及物种分化速率随时间波动的具体过程。

Fig. 3 Diversification history of Didiereaceae inferred from Bayesian Analysis of Macroevolutionary Mixtures (BAMM) analysis. A, Phylorate plot showing net diversification rate (branch colors). The red dot indicates an increased diversification rate shift. B, Rate-through-time plots for speciation, extinction and net diversification. Ma, million years ago.

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