Biologue

Article by
Gerald T. Kraft, School of Botany, University of Melbourne, Parkville, Victoria 3052

Rising abruptly and spectacularly out of the south Pacific Ocean between Australia and New Zealand is Lord Howe Island, one of the scenic and biological wonders of the world and the first area in all of Australia to gain World Heritage listing. Unconnected to any land mass since its volcanic birth some 6 to 7 million years ago - a length of time which just coincidently happens to be (so the paleontologists and molecular geneticists tell us) about as long as it's taken for us humans to evolve from our primate ancestors - it has rightly been called Australia's Galapagos due to the wealth and, at times, bizarreness of its endemic plants and animals.

In the early 1970s, as a student of marine algae with Professor Bryan Womersley at the University of Adelaide, I looked at a map with an idea to picking out the most desirable unexplored places in the country for launching studies of seaweed biodiversity. On seeing where Lord Howe lay I exclaimed, much in the manner of Joseph Smith, "This is the place". Lying some 780 km northeast of Sydney and site of the world's southernmost coral reef, it looked like promising a bit of everything: an almost certainly unique mixture of temperate, tropical and endemic floral elements and a made-to-order laboratory for considering taxonomic and biogeographical questions like "What's to be found in such an isolated place, and where did everything that's there come from?"

When I looked to see what was already known of Lord Howe macroalgae, I found that its first seaweeds had been described almost exactly 100 years earlier by an obscure Venetian phycologist (i.e., student of algae) named Zanardini from the collections of two even obscurer Sydney gardeners commissioned for a land-and-sea botanical survey of the island by Baron von Mueller. The 15 or so new species minimally (and unillustratedly) described in 1874 by Zanardini were the sum total of our floristic knowledge of the algae of the island until 60 years later, when the former Sydney headmaster and amateur phycologist A.H.S. Lucas briefly described 93 green, brown and red seaweeds, 15 of them new, from a mid-winter month spent on Lord Howe. So the scope for more detailed work was definitely there, especially now that SCUBA technology was at hand for conducting deep-water explorations and modern transport put the island in reach during every season.

Since 1976, just a year after the famous Flying Boats were replaced by twin-engine commuter planes, I've been surveying the seaweed flora of Lord Howe and finding that it more than matches expectations. For a place just 11 km long and never more than three km wide, it must be one of the richest areas for marine algae, metre-for-metre, of any spot in the world. Not only its lifelong isolation but also its position at the border of tropical and temperate biological provinces (it is said that winter water temperatures there are at the lower limit for sustaining an existing coral reef and below the threshold should you want to start one up) and the huge range of habitat niches (from intertidal flats and tidepools to shallow sandy and coral-paved lagoons to deeply plunging basalt and fringing outer-reef slopes) are probable major contributors to the unique character and richness of its marine flora.

What kind of marine flora does it have? Most of its 350+ species show tropical (Great Barrier Reef and Indo-Pacific) affinities, with relatively few being common to the southern Australian coast and even fewer having New Zealand links. What this means in terms of ABRS priorities for documenting the tropical marine floras of Australia that are currently so poorly known (compared to the temperate regions, now thankfully, comprehensively monographed by Prof. Womersley) is that Lord Howe serves particularly well as an accessible, condensed and pristine habitat displaying a good proportion of the algal elements of our tropical north. This claim is backed up by our own studies of the Great Barrier Reef and those of Norfolk Island by Dr Alan Millar.

How much real endemism is there at Lord Howe? That's an interesting and problematic question to which the answer keeps changing with new discoveries at Lord Howe and better documentation of Pacific floras to the north, including Papua-New Guinea, Fiji, Samoa, Hawaii, the Micronesian islands and the Philippines. Over the years my colleagues and I have described a new genus and 34 new species for which Lord Howe is type locality, but we are finding that many of what appaeared to be endemics later turn up in other areas as better studies are carried out in those regions. A good example is Codium platyclados Jones & Kraft, probably the largest green alga on the island and one that is common from barely subtidal to 30 m depths. It has now been recorded from the Philippines. The golden-brown, translucent Cutleria mollis Allender & Kraft was thought to be endemic until also found at Norfolk Island and later the Kermadec Islands of New Zealand. Although the monotypic red-algal genus Reptataxis Kraft, which grows from low-intertidal to 20 m depths, has not been found so far in any other locality, Meristotheca procumbens Gabrielson & Kraft is now reported from Fiji, where it has long been harvested and eaten by the inhabitants of Rotuma Island.

The Lord Howe studies are continuing and accelerating. A monograph of the greens has recently been completed, one on the browns is in final preparation, and attention has now turned to the largest group, the reds. Two new approaches in addition to that of classical, morphology-based taxonomy now figure in the Lord Howe studies: molecular biology (with Dr Gary Saunders of the University of New Brunswick) is giving us vital clues to the identity and relationships of many of the species, and carbohydrate chemistry (in collaboration with Dr Tony Chiovitti and student Nicole Watt) is assessing the potential commercial value of carrageenophytes such as Meristotheca procumbens and Reptataxis rhizophora (Lucas) Kraft. Lord Howe continues to throw out surprises with each new excursion we make, and to reward its researchers with a wealth of taxonomic riches.