Climate niches of milkweeds with plesiomorphic traits (Secamonoideae; Apocynaceae) and the milkweed sister group link ancient African climates and floral evolution

Livshultz, Tatyana; Mead, Jerry; Goyder, D. J.; Brannin, Michelle

doi:10.3732/ajb.1100202

Cited by 18 publications

(15 citation statements)

References 106 publications

(156 reference statements)

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“…The origin center of the subfamily seems to be in Africa (Rapini et al., ), as suggested by the African distribution of genera representing basal taxa in the molecular phylogeny (Rapini et al., ; Nazar et al., ). A split between Secamonoideae and Asclepiadoideae with subsequent radiations and dispersions from Africa has been inferred to have taken place during the Eocene, Oligocene, and Neogene (Goyder, ; Rapini et al., ; Livshultz et al., ). However, the ages inferred in those studies need to be reinvestigated (Fishbein et al., ).…”

Section: Discussionmentioning

confidence: 99%

Asclepiadospermumgen. nov., the earliest fossil record of Asclepiadoideae (Apocynaceae) from the early Eocene of central Qinghai‐Tibetan Plateau, and its biogeographic implications

Rio

Wang

Liu

et al. 2020

American J of Botany

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Premise Apocynaceae is common in the fossil record, especially as seed remains from the Neogene of Europe and North America, but rare in Asia. Intrafamilial assignment is difficult due to the lack of diagnostic characters, and new fossil and modern data are needed to understand the paleobiogeography of this group. Methods We studied three Apocynaceae seed impressions from the Lower Eocene Niubao Formation, Jianglang village, Bangor County, central Qinghai‐Tibetan Plateau. Morphological data from living and fossil species were phylogenetically mapped to enable systematic assignment. Results We describe a new genus, Asclepiadospermum gen. nov., and two new species, A. marginatum sp. nov. and A. ellipticum sp. nov. These species are characterized by an elliptical seed, a margin surrounding the central part of the seed, and polygonal, irregular, and small epidermal cells, and differ mainly in terms of the size of the margin and the shape of the apex. All these characters indicate that this new genus belongs to the subfamily Asclepiadoideae (Apocynaceae). Conclusions These fossils represent the earliest fossil seed records of Asclepiadoideae. Asclepiadospermum indicates a humid tropical to subtropical flora during the early Eocene in central Tibet. Moreover, our discoveries indicate a close floristic connection between Eurasia and Africa during the early Eocene, which expands our knowledge of the floristic linkage between Tibet and other regions at that time.

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Section: Discussionmentioning

confidence: 99%

Asclepiadospermumgen. nov., the earliest fossil record of Asclepiadoideae (Apocynaceae) from the early Eocene of central Qinghai‐Tibetan Plateau, and its biogeographic implications

Rio

Wang

Liu

et al. 2020

American J of Botany

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“…Thus, we suggest that the outstanding diversification of core Pachycereeae, Hylocereeae and Trichocereeae is related to the evolution of derived pollination syndromes, with a possible trend towards a specialization for bats in North America and moths in South America, both facilitated by an arborescent, shrubby or columnar growth form. In the context of an arid environment where plant populations have low densities, the evolution of a pollination mechanism that increases pollen‐transfer efficiency can be helpful to overcome mate‐finding Allee effects and to continue to reproduce successfully (Ghazoul, ; Gascoigne et al ., ; Livshultz et al ., ), particularly in long‐lived and slow‐growing species such as many cacti.…”

Section: Discussionmentioning

confidence: 99%

Beyond aridification: multiple explanations for the elevated diversification of cacti in the New World Succulent Biome

et al. 2014

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SummarySucculent plants are widely distributed, reaching their highest diversity in arid and semi-arid regions. Their origin and diversification is thought to be associated with a global expansion of aridity. We test this hypothesis by investigating the tempo and pattern of Cactaceae diversification. Our results contribute to the understanding of the evolution of New World Succulent Biomes.We use the most taxonomically complete dataset currently available for Cactaceae. We estimate divergence times and utilize Bayesian and maximum likelihood methods that account for nonrandom taxonomic sampling, possible extinction scenarios and phylogenetic uncertainty to analyze diversification rates, and evolution of growth form and pollination syndrome.Cactaceae originated shortly after the Eocene-Oligocene global drop in CO 2 , and radiation of its richest genera coincided with the expansion of aridity in North America during the late Miocene. A significant correlation between growth form and pollination syndrome was found, as well as a clear state dependence between diversification rate, and pollination and growthform evolution.This study suggests a complex picture underlying the diversification of Cactaceae. It not only responded to the availability of new niches resulting from aridification, but also to the correlated evolution of novel growth forms and reproductive strategies.

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“…In Apocynaceae, Asclepiadoideae has been shown to form a monophyletic group, sister to Secamonoideae, from which it differs by the possession of two instead of four pollinia per pollinarium (Livshultz et al ., ). The tribal and subtribal structure of Asclepiadoideae is generally well understood (e.g.…”

Section: Introductionmentioning

confidence: 97%

On the systematic position of some Asian enigmatic genera of Asclepiadoideae (Apocynaceae)

et al. 2014

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The phylogenetic structure of Asclepiadoideae (Apocynaceae) has been elucidated at the tribal and subtribal levels in the last two decades. However, to date, the systematic positions of seven Asian genera, Cosmostigma, Graphistemma, Holostemma, Pentasachme, Raphistemma, Seshagiria and Treutlera, have not been investigated. In this study, we examine the evolutionary relationships among these seven small enigmatic Asian genera and clarify their positions in Asclepiadoideae, using a combination of plastid sequences of rbcL, rps16, trnL and trnL-F regions. Cosmostigma and Treutlera are resolved as members of the non-Hoya clade of Marsdenieae with strong support (maximum parsimony bootstrap support value BSMP = 96, maximum likelihood bootstrap support value BSML = 98, Bayesian-inferred posterior probability PP = 1.0). Pentasachme is resolved as sister of Stapeliinae to Ceropegieae with moderate support (BSMP = 64, BSML = 66, PP = 0.94). Graphistemma, Holostemma, Raphistemma and Seshagiria are all nested in the Asclepiadeae-Cynanchinae clade (BSMP = 97, BSML = 100, PP = 1.0). The study confirms the generally accepted tribal and subtribal structure of the subfamily. One exception is Eustegia minuta, which is placed here as sister to all Asclepiadeae (BSMP = 58, BSML = 76, PP = 0.99) and not as sister to the Marsdenieae + Ceropegieae clade. The weak support and conflicting position indicate the need for a placement of Eustegia as an independent tribe. In Asclepiadeae, a sister group position of Cynanchinae to the Asclepiadinae + Tylophorinae clade is favoured (BSMP = 84, BSML = 88, PP = 1.0), whereas Schizostephanus is retrieved as unresolved. Oxystelma appears as an early-branching member of Asclepiadinae with weak support (BSMP = 52, BSML = 74, PP = 0.69). Calciphila and Solenostemma are also associated with Asclepiadinae with weak support (BSMP = 37, BSML = 45, PP = 0.79), but all alternative positions are essentially without support. The position of Indian Asclepiadoideae in the family phylogeny is discussed.

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Climate niches of milkweeds with plesiomorphic traits (Secamonoideae; Apocynaceae) and the milkweed sister group link ancient African climates and floral evolution

Abstract: Secamonoideae in continental Africa inhabit drier, cooler sites than do the milkweed sister group, consistent with a shift from rainforests to dry forests in a cooling climate.

Cited by 18 publications

References 106 publications

Asclepiadospermumgen. nov., the earliest fossil record of Asclepiadoideae (Apocynaceae) from the early Eocene of central Qinghai‐Tibetan Plateau, and its biogeographic implications

Asclepiadospermumgen. nov., the earliest fossil record of Asclepiadoideae (Apocynaceae) from the early Eocene of central Qinghai‐Tibetan Plateau, and its biogeographic implications

Beyond aridification: multiple explanations for the elevated diversification of cacti in the New World Succulent Biome

On the systematic position of some Asian enigmatic genera of Asclepiadoideae (Apocynaceae)

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