Available online
Description
Adaptive radiation is the evolutionary process by which organisms adapt to a wide diversity of habitats. The silversword, found only on the island of Maui in Hawaii, is one of the world's best exam...ples of adaptive radiation in plants. This programme describes many plants belonging to the silverwood alliance and also shows how they as a species originated in the islands.
Adaptive radiation is the evolutionary process by which organisms adapt to a wide diversity of habitats. The silversword, found only on the island of Maui in Hawaii, is one of the world's best exam...ples of adaptive radiation in plants. This programme describes many plants belonging to the silverwood alliance and also shows how they as a species originated in the islands.
| Module code and title: | S364, Evolution |
|---|---|
| Item code: | S364; 09 |
| First transmission date: | 23-07-1981 |
| Published: | 1981 |
| Rights Statement: | |
| Restrictions on use: | |
| Duration: | 00:24:25 |
| + Show more... | |
| Producer: | Roger Jones |
| Contributors: | Gerald Carr; Irene Ridge |
| Publisher: | BBC Open University |
| Keyword(s): | Adaptive radiation; Colonisation; Deserts; Evolution; Haleakala; Hawaii; Hybridisation; Silversword; Volcanic desert |
| Subject terms: | Botany--Hawaii; Compositae |
| Footage description: | Shots of a Haleakala silversword. Aerial shots of Hawaii. Commentary introduces the programme with a look at the immensely varied habitats of the different islands and even within islands. Shots of swamps, rain forest, desert, volcanoes, etc., including active volcanoes. Shots of Haleakala, a volcanic desert. Shots of several plants found there. Shots of Hawaiian geese and shots of the Haleakala silversword, Argyroxiphium macrocephalum. Commentary points out the adaptive characteristics of each of the above species. Shots of a silversword in flower including close ups of the blooms. The programme next looks at the second genera of the silversword alliance, the Dubautia. Shots of Dubautia menziesii, a relative of the silversword and adapted to much the same habitat. Also shots of Dubautia knudsenii which is adapted to a wet habitat and looks very different. Shots of Dubautia latifolia which lives in a drier forest habitat and has taken on a vining habit. Shots of yet another relative, Dubautia plantaginea, adapted to a still drier forest habitat. All look very different. Shots of an intergeneric hybrid growing between Dubautia menziesii and the Haleakala silversword, Argyroxiphium macrocephalum. Commentary, discussing both the parents and the hybrid, points out their habits and then explains why the hybrid is evidence for a common ancestor for both plants several million years ago. Shots of volcanic activity. Commentary explains how such sudden changes of habitat encourage intergeneric hybrids to diversify and form new species. Shots of several different hybrids. Gerald Carr looks at two species of Dubautia; Dubautias ciliolata and scabra. The two plants live next to each other on different types of soil. Between them are found several hybrids Close up shots of these hybrids and their parent Shots of the landscape near the plants. Commentary discusses the features of the habitat which encourage radiation into different species. Shots of hybrid chromosomes. Carr speculates on how the new species would have formed in view of what is known of hybridisation. Shots of Dubautias sherfiana, platyphyla, reticulata, laxa, railliardiodes and microcephala all living in different habitats. The programme next looks at an example of the third genus of the silversword alliance, Wilkesia. Shots of Wilkesia gymnoxiphium. Commentary describes the plant and its habitat. Shots of the greensword Argyroxiphium virenscen which is found in bog conditions. Next, shots of all the leaves of the various plants examine so far in the programme. These show clearly the vast diversity of the alliance which has developed to suit particular habitats. Commentary points out the correlation between leaf size and thickness and wetness of habitat. Over shots of several Hawaiian islands and of a map of the islands, commentary traces the origins of the silversword alliance in the islands. In this way the chromosome count of the earliest species to colonise Hawaii can be determined. Over shots of several Hawaiian islands and of a map of the islands, commentary traces the origins of the silversword alliance in the islands. In this way the chromosome count of the earliest species to colonise Hawaii can be determined. Shots of Adenothammus validus, a Baja California plant with the same chromosome count as the earliest of the silversward alliance on Hawaii. Commentary points out that this plant is thought to be ancestral to those on Hawaii and that the vast radiation on the islands may all have begun with a single seed carried there from California. |
| Master spool number: | HOU3599 |
| Production number: | FOUS120J |
| Videofinder number: | 2060 |
| Available to public: | no |
