The ecology, evolution, and genetics of the Hawaiian Silversword Alliance

1. The ecology, evolution, and genetics of the Hawaiian Silversword Alliance Kurt Hartman

2. Silversword researchers Gerald Carr Bruce Baldwin Robert Robichaux

3. Silversword researchers Leslie Bohm Bruce Bohm Donald W. Kyhos Bill Crins

4. Adaptive Radiation on Hawaii Bidens menziesii Geranium cuneatum Delissea undulataCampanulaceae

5. Adaptive Radiation on Hawaii honeycreeper Drosophilidae

6. What is the Silversword Alliance? • 28 species endemic to Hawaii • 3 genera • Argyroxiphium (5 spp.) • Dubautia (21 spp.) • Wilkesia (2 spp.)

7. Genus #1 - Argyroxiphium = the “silverswords” & “greenswords” • Most recognized genus of silversword alliance • Capitulum with ray flowers (contrast with Wilkesia & Dubautia which only have disk flowers) • Hybrid between Argyroxiphium, Wilkesia, and Dubautia species • Found on Maui and Hawaii

8. Silversword species (3) A. caliginis Bog silversword A. kauense A. sandwicense

9. 2 subspecies of A. sandwicence ssp. sandwicense ssp. macrocephalum

10. Argyroxiphium

11. Argyroxiphium sandwicense habitat • Habitat on cinder cone • 7000 to 10000 feet – intense sunlight • Hot in summer day & below freezing in winter night • Snowfall, zero humidity, low ppt = alpine desert

12. Silversword trichomes

13. (Melcher et. al 1994)

14. Unusual features • Pectic warts • Secondary growth

15. Greenswords (2) Argyroxiphium virescens hybrid Argyroxiphium grayanum

16. Changes in soil characteristics below Argyroxiphium • Soil below silversword increased in water and nutrient retention, lower temperature (18C), greater nutrient concentration for up to 7-9 yrs post mortum. • Therefore good for current survival and future offspring who may be close in proximity to parent. (Perez 2001)

17. Genus #2 - Wilkesia • 2 species: Wilkesia gymnoxiphium & Wilkesia hobdyi W. gymnoxiphium • grows on pockets in eastern Kaua’i (oldest high island) and may prefer certain soil types • Dry, shrubby forest

18. Wilkesia gymnoxiphium • Seldom branching stems (branch if injured), ≳ 10 ft • Flat, fibrous leaves in whorls that are strictly parallel with few crosscutting veinlets • Monocarpic

19. Wilkesia gymnoxiphium Wilkesia gymnoxiphium • Inflorescence with whorls of heads, all discoid flowers

20. Wilkesia hobdyi Freely branching, decumbent to erect, endangered, grows only on Kaua’i, restricted to very dry ridges (75 - 100cm ppt / yr, elevation 275 - 400m)

21. Wilkesia hobdyi

22. Genus #3 - Dubautia • Most “recent” genus • 21 species with differential spatial and habitat distribution • Found on Kaua’i, O’ahu, Moloka’i, Lana’i, Maui, Hawai’i • 2 other mainland islands have no Dubautia • 17 out of 21 species of Dubautia are single- island endemics

23. D. ciliolata D. plantaginea D. latifolia D. scabra

24. Movie Part IDubautia species

25. D. latifolia (vine) – “reticulate vein pattern with polygonal areoles containing numerous free-terminating veins” Veination patterns in Dubautia and Wilkesia D. microcephala (left) D. linearis (right) W. gymnoxiphium (Carlquist 1959)

26. Dubatia herbstobatae

27. Dubatia arborea

28. Dubautia menziesii - kupaoa

29. Dubautia waialealae

30. Dubatia latifolia (vine)

32. D. laevigata Dubautia laevigata

33. Dubautia pauciflorula

34. 2 studies in conservationFriar et. al 2000A. sandwicense in bad shape Friar et. al 2001A. kauense in good shape

35. Habitat divergence • Elevation from 75 to 3750m • Habitats of dry shrublands, dry forests, subalpine shrublands, subalpine forests, alpine deserts, mesic forests, wet forests, bogs, young lava flows (Carr 1985)

36. Physiological and morphological divergences • Different tissue and elastic properties to maintain turgor at low water potentials (Robichaux 1985) • Different cell structures - especially Dubautia, • Wet environments – Thin cuticle, thin leaves, loose mesophyll • Dry environments – Thick cuticle, thick leaves, compact mesophyll, extracellular mesophyll, and white hairs (Carlquist 1958) • Veination –Dubautia latifolia – highly reticulate; Wilkesia – monocot-like veination with few crosscutting veinlets; Others – subparallel or longitudinally directed veins (Givnish & Sytsma 1997)

37. Who are the ancestors of silversword alliance? • Tarweeds found in California “floristic province” = CA and Mex. • Shrubby, sprawling plants • Similar in floral morphology and anatomy to silverswords • Sticky substance on flowers and fruits • Arrived in Hawaii on bird feathers (most likely) roughly 5 mya (Baldwin & Robichaux 1995)

38. What’s in a name? – “Tarweeds” Tarweed Raillardiopsis muirrii A. sandwicense

39. The original silversword was a polyploid… what kind of polyploid?

40. Hypothesis for polypolidy (n = 14)

41. Hypothesis for polypolidy (n = 14) Best explanation

42. In what way did the silverswords move around Hawaii in terms of biogeography and habitats?

43. Biogeography & phylogeny • Minimum inter-island dispersal and large ecological divergence • Generally westward to eastward movement • Kaua’i, Oahu, Maui Nui – once contiguous islands facilitated this movement

49. How do we investigate these evolutionary relationships?

50. Laboratory methods of investigation • Cytogenetic & hybridization analysis • Nuclear DNA (nDNA) • Chloroplast DNA (cpDNA) • Mitochondrial DNA (mDNA) • Ribosomal DNA (rDNA) • Isozymic analysis