Evolution of growth and life forms in Piperales Country and continent relation: France (Europe), Fr. Guiana, Mexico, Costa Rica (America), China (Asia)
Zusammenfassung der Projektergebnisse
A striking feature of early angiosperm lineages is the variety of life and growth forms, which ranges from terrestrial and aquatic herbs, climbers, and epiphytes to woody shrubs and trees. This morphological diversity is arguably one of the factors explaining how angiosperms dominate many ecosystems worldwide. However, how such a wide spectrum of growth forms has evolved in angiosperms remains under discussion. We investigated patterns of growth form diversification in the Black-Pepper relatives (Piperales). Asaroideae and Saururaceae are terrestrial as well as semiaquatic to aquatic herbaceous perennials bearing rhizomes. The Aristolochioideae and Piperaceae show higher levels of growth form diversity and biomechanical organization, with complex patterns of increasing or decreasing woodiness and architectural organization. The climbing habit has evolved independently in the Aristolochiaceae and Piperaceae. The same applies to mechanically unstable shrubs and, less frequently, treelets. Patterns of growth form evolution within Piperales potentially mirror some of the overall trends observed among early-diverging angiosperms as a whole, as well as angiosperms in general. These include profound changes in life form and growth form linked to large-scale transitions in woodiness, diversity of mechanical organization, and shifts in architectural development. Aristolochia, as an example, contains herbs, as well as climbers and shrub-like growth forms. Ancestral character state reconstruction revealed that climbers evolved with the diversification of the genus Aristolochia, and might have been a key feature for its radiation. Several functional traits linked to the climbing habit have been detected, such as the large proportion of parenchymatous tissues in the stem, as well as particular biomechanical properties. Furthermore, a trend towards increased cambial activity could be detected, involving the development of larger plant individuals. Investigations reveal that the establishment of functional traits linked to lianescence might limit the ability to evolve structurally diverse growth forms, particularly selfsupporting forms. It is thus suggested that while shrub-like species might have partly escaped from the constraints of life as lianas, their height size and stability are not typical of self-supporting shrubs and trees. Shrubs retained lianoid stem characters that are known to promote flexibility such as ray parenchyma. The transitions to a shrub-like form likely involved relatively simple, developmental changes that may be attributed to heterochronic processes. With respect to the holoparasitic Hydnoraceae, we were able to demonstrate that the highly modified subterranean structures of Hydnora (Hydnoraceae) are very likely modifications of the plant stem, therewith confirming the hypothesis of Tennakoon et al. (2007).
Projektbezogene Publikationen (Auswahl)
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(2011) Implications from molecular phylogenetic data for systematics, biogeography and growth form evolution of Thottea (Aristolochiaceae). The Gardens’ Bulletin Singapore. 63: 259-275
Oelschlägel B., Wagner S., Salomo K., Pradeep N.S., Yao Z.L., Isnard S., Rowe N., Neinhuis C., Wanke S.
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(2012) Escaping the lianoid habit: Evolution of shrub-like growth forms in Aristolochia subgenus Isotrema (Aristolochiaceae). American Journal of Botany 99:1609-1629.
Wagner S.T., Isnard S., Rowe N.P., Samain M.-S., Neinhuis C., Wanke S.
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(2012) Growth form evolution in Piperales and its relevance for understanding angiosperm diversification: An integrative approach combining plant architecture, anatomy and biomechanics. In: Special Issue: Major transitions in angiosperm ecology and functional biology (eds. Field T., Edwards E.). International Journal of Plant Sciences 173: 610-639
Isnard S., Prosperi J., Wanke S., Wagner S., Trueba S., Frenzke L., Samain M-S., Neinhuis C., Rowe N.P.
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(2013) Present trans-Pacific disjunct distribution of Aristolochia subgenus Isotrema (Aristolochiaceae) was shaped by dispersal, vicariance and extinction. Journal of Biogeography
González F., Wagner S.T., Salomo K., Symmank L., Samain M.-S., Isnard S., Rowe N., Neinhuis C., Wanke S.
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(2013) Single-copy nuclear genes place haustorial Hydnoraceae within Piperales and reveal a Cretaceous origin of multiple parasitic angiosperm lineages. PLoS ONE 8(11): e79204
Naumann J., Salomo K., Der J., Wafula E., Bolin J., Maass E., Frenzke L., Samain M.S., Neinhuis C., dePamphilis C.W., Wanke S.
