Evolutionary Patterns in the tropical plants

1. Evolutionary Patterns in the tropical plants Min Feng Neotropical rainforest ecology seminar French Guiana, Spring 2002

2. Outline: • Introduction • Evolutionary patterns of flowers • Coevolution between plants and animals • Summary • Keys to my questions

3. Outline: • Introduction • Evolutionary patterns of flowers • Coevolution between plants and animals • Summary • Keys to my questions

4. Introduction: evolution • The process responsible for the way organisms look, function and act. • Charles Darwin’s (1859) natural selection theory: struggle for existence; survival of the fittest. • Major explanation of adaptation and speciation • Groups of organisms, as species, may change with passage of time so that descendants differ morphologically and physiologically from their ancestors.

5. Introduction: Factors affect plant evolution • non-biotic factors - environmental conditions (light, water, soil, climate etc.) • biotic factors - interaction between similar or different groups of organisms (competition of resource, mutualism, etc. )

6. Question 1: What are main factors that function in plant evolutionary process? • non-biotic factors such as light, water, soil, climate etc. • biotic factors, interaction between similar or different groups of organisms

7. Outline: • Introduction • Evolutionary patterns of flowers • Coevolution between plants and animals • Summary • Keys to my questions

8. Evolutionary patterns of flowers  

9. Evolutionary patterns of flowers

10. Evolutionary patterns of flowers Perianth • Function: enclose and protect the fertile organs; attract pollinators • Diversity: - size and texture (largest flower --- 1 m in diameter or in length) - protective structure (thick; hair; etc) - aestivation patterns - floral symmetry - attractive structures (colors, mimicry) - union of perianth organs etc.

11. Evolutionary patterns of flowers Perianth Example: aestivation patterns

12. Evolutionary patterns of flowers Androecium • Male function organs: stamens + sterile organs (staminodes) • Relatively uniform: (construction and size) 4 pollen sacs in 2 lateral thecae

13. Evolutionary patterns of flowers Androecium • Diversity - stamen number and arrangement - union of stamens (synandry) - dehiscence patterns - heteranthery - pollen aggregation etc.

14. Evolutionary patterns of flowers Androecium Examples of androecium evolutionary aspects: - stamen numbers fixation of a relatively low number of stamen secondary multiplied stamen primordia - union of stamens Cola acuminata (Sterculiaceae) Stephania japonica (menispermaceae)

15. Evolutionary patterns of flowers Gynoecium • Female organ • Central and most complicated structure of angiosperms • Diversity - carpel number and arrangement - carpel structure - ovary position - stigma - pollen tube transmitting tract - placentation and ovules

16. Evolutionary patterns of flowers Evolutionary aspects of gynoecium: - two major trends: apocarpy to syncarpy; crassinucellar, bitegmic ovules to tenuinucellar, unitegmic ones - other aspects: from superior to inferior ovary from syncarpy to secondary apocarpy from unicarpellate to multicarpellate gynoecia from eusyncarpous to paracarpous gynoecia extreme reduction in gynoecium strucrure

17. Evolutionary patterns of flowers Question 2: What is special in tropical flowers? • only a general answer could be made here • the diversity of tropical flowers encompasses almost the entire range of flower diversity on earth, while the diversity of flowers in other parts of the worlds is much more restricted. • directly related to the greater diversity of pollinators available.

18. Outline: • Introduction • Evolutionary patterns of flowers • Coevolution between plants and animals • Summary • Keys to my questions

19. Coevolution: • The process when one lineage adapts in response to characters in another lineage, and that lineage then adapts in response to the first adaptation. (Janzen, 1980) • Reciprocal evolution as the continuous interaction of evolving lineages which is fundamental to the diversity of organisms. (Thompson, 1994) • When one species has a trait that acts as a selective pressure on another, and the second species in turn possesses a trait that acts as a counterselection pressure back upon the first, the evolutionary fates of both species can become permanently interlocked. This situation is called coevolution.

20. Coevolution: • Results from both mutualistic and antagonistic (parasitic or predatory) interactions • Selective pressure on each lineage depends on the severity of the consequences of the interaction on each participant • Range from the wide diffuse, involving many species to the tight specific • Important coevolution systems between plants and animals: - pollination - seed dispersal - grazing vertebrates etc.

21. Pollination: Pollinators: Special for tropical areas Bat Hummingbird

22. Rewards from plants for animal pollinators • Pollen • Nectar • Oil • Resin and wax - Waxes used by bees for nest-building material - Very few plant species - Here is Clusia uvitana (Guttiferae) from C. America

23. Pollination of neotropical Lecythidaceae: • numerous stamens • poricidal anthers • large quatities of pollen • no nectar • Gustavia augusta • actinomorphic • bee-pollination • Grias neuberthii • actinomorphic • beetle-pollination

24. Pollination of neotropical Lecythidaceae:second step of androecial specialization Couroupita guianensis Xylocopa bee - zygomorphic flowers - anthers in bothstaminal ring and hood - two types of pollens - large bees force their way into the hood; pollen dusted on their heads and backs - dimorphic pollen has been a response to the selective pressure of bees

25. Pollination of neotropical Lecythidaceae:next step of androecial specialization • Production of nectar • No anther in the hood but nectar appendages • Hood is tightly appressed to the staminal ring and the summit of the ovary • Bees large and strong enough to open the hood and tongue long enough to reach the nectar (apex of the coiled hood) Couratari Eulaema mocsaryi - euglossine bee with a long tongue

26. Pollination of neotropical Lecythidaceae:next step of androecial specialization • Geographic distribution of the zygomorphic, nectar-producing Lecythidaceae falls within the range of the euglossine bees; both are restricted to the new world. ( also most occur in moist forest) Distribution of euglossine bees Distribution of nectar-producing species of Lecythidoidae

27. Pollination of neotropical Lecythidaceae:next step of androecial specialization • Euglossine bees are well-known important pollinators of Neotropical orchids. • Bees are attracted by odors (mating), but also depend on other plants for nectar, pollen and resins. • Zygomorphic species of Lecythidaceae are one of several groups that provide bees nectar and pollen. • So, neotropical Lecythidaceae are upon the forest orchids and the bees, to some extent, indicating the delicate web of evolutionary interactions.

28. Question 3: What are three main steps of the evolutionary specialization in the androecium of neotropical Lecythidaceae? • actinomorphic staminal ring • zygomorphic staminal ring with the hood and dimorphic pollens • zygomorphic staminal ring with the hood and nectar packed deeply in coiled hood

29. Seed dispersal of Aglaia (Meliaceae) Aglaria erythrosperma - large dehiscent fruits - fruits in infructescences on a sturdy peduncle - aril red-skinned, rich in lipid and odorless - arillate seed (5 x 3.5 x 2 cm) - dispersed by hornbill - black Hornbill about 76cm long

30. Seed dispersal of Aglaia (Meliaceae) Aglaria teysmanniana • Small, dehiscent fruits (2.2 x 2 cm) • Fruits in infructescences close to the branches • Aril red-skinned, rich in lipid and odorless • Green Broadbill about 19 cm long, one of the birds which disperses the seeds of Aglaria teysmanniana

31. Seed dispersal of Aglaia (Meliaceae) Aglaria elliptica • Indehiscent fruits (3.5 x 3 cm) • Large hanging infructescences on slender branch ends • Aril gelatinous, sweet-tasting and odor • White-handed or lar Gibbon (about 46cm long), disperses the seeds

32. Seed dispersal of Aglaia (Meliaceae) • Reveal the adaptations within the groups of related plant species for their dispersers and of the animals for the fruits they eat. • Here coevolution is not one-to-one relationship. • Two major fruit types: dehiscent type for birds (all size) and indehiscent type for primates. • Fruits are eaten by any animal which could access them; fruit-eating animals are unlikely to rely on a single plant species or group of species for all of their nutritional requirements.

33. Pollination again Passionflowers: Passiflora  Neotropical  on OU campus • Pentamerous with two perianths whorls and one stamen whorl • Trimerous gynoecium • Stamens and ovary raised on an androgynophore • Corona between perianth and stamens (multiplied staminodes)

34. Pollination again --- passionflowers: • Blue and white flowers • Both small and large flowers • Xylocopa ( bees )

35. Pollination again --- passionflowers: • Bright red or scarlet flowers • Only large flowers • Birds: hummingbirds and other birds, such as Andean swordbill (Ensifera)

36. Pollination again --- passionflowers: Passiflora vitifolia - red flowers borne on bare stems close to ground level in the tropical jungle of Costa Rica - leaves high up in the forest canopy - pollinated by hermit hummingbirds feeding at lower levels 

37. Pollination again --- passionflowers: Passiflora Who is the pollinator of this species?

38. Pollination again --- fungus mimicry:pollination by mushroom-gnats • Pollinating gnats lay eggs that are bound to perish • Most plants are forest-dwellers: plants close to ground; flowers are dark purple or brown, with pale or translucent patterns • Here: orchid Masdevallia bella, a gill-like blade and a fleshy claw on its lip petal

39. Question 4: Name the two sorts of coevolutionary interactions. • antagonistic (parasitic or predatory) relationships - one species benefits at the expense of another • Mutualistic relationships - both species benefit

40. Outline: • Introduction • Evolutionary patterns of flowers • Coevolution between plants and animals • Summary • Keys to my questions

41. Summary: - The diversity of tropical flowers encompasses almost the entire range of flower diversity on earth, while the diversity of flowers in other parts of the worlds is much more restricted. - Therefore, tropical flowers provide a basis of the study of flower evolution in general. - The greater diversity of tropical flowers is directly related to the greater diversity of pollinators available. - The seed dispersal mechanism is also related to the variations of flower and fruit construction patterns.

42. Outline: • Introduction • Evolutionary patterns of flowers • Coevolution between plants and animals • Summary • Keys to my questions

43. Question 1: What are main factors that function in plant evolutionary process? • non-biotic factors such as light, water, soil, climate etc. • biotic factors, interaction between similar or different groups of organisms

44. Question 2: What is special in tropical flowers? • only a general answer could be made here • the diversity of tropical flowers encompasses almost the entire range of flower diversity on earth • directly related to the greater diversity of pollinators available.

45. Question 3: What are three main steps of the evolutionary specialization in the androecium of neotropical Lecythidaceae? • actinomorphic staminal ring • zygomorphic staminal ring with the hood and dimorphic pollens • zygomorphic staminal ring with the hood and nectar packed deeply in coiled hood

46. Question 4: Name the two sorts of coevolutionary interactions. • antagonistic (parasitic or predatory) relationships - one species benefits at the expense of another • Mutualistic relationships - both species benefit

47. Selected references: • Endress, P.K., 1994. Diversity and evolutionary biology of tropical plants. Cambridge University Press. • Kricher, J., 1997. A neotropical companion. Princeton University Press. • Prance, G.T., & Mori, S.A., 1998. Pollination and dispersal of Neotropical Lecythidaceae. In: The biological monograph: the importance of field studies and functional syndromes for taxonomy and evolution of tropical plants. The Royal Botanical Gardens, Kew. • Meeuse, B., & Morris, S., 1984. The sex life of flowers. Oxford Scientific Film Ltd. • Pannell, C.M., 1998. Taxonomy, ecology and reproductive biology of Aglaia (Meliaceae). In: The biological monograph: the importance of field studies and functional syndromes for taxonomy and evolution of tropical plants. The Royal Botanical Gardens, Kew. • Schatz, G.E., 1990. Some aspects of pollination biology in central American forests. In: Bawa K.S. & Hadley M., (eds) Reproductive ecology of topical forest plants. Unesco, Paris.

48. Thanks