Temperate Western Australia Research Articles

Pattern and process in southern Western Australian seagrasses

Posidonia and other seagrass genera cover vast areas along the coast of temperate Western Australia, where it seems that disturbance and recolonisation are the dynamic forces which govern the pattern of seagrass beds. Some species of Posidonia may take 60–100 years to cover cleared substratum while species of other genera may come and go within a year. Three case studies of spatially widely separated seagrass beds are given. They illustrate that depth, weather and location make great differences to the extent and diversity of seagrasses. Comments on reproductive ability and observations on seedling growth and vegetative propagation are given with emphasis on the “ Posidonia ostenfeldii” complex.

Comparisons between the roles played by estuaries in the life cycles of fishes in temperate Western Australia and Southern Africa

The rivers of south-western Australia and south-eastern Africa lie at similar latitudes, open into the Indian Ocean and frequently have estuaries that are periodically closed off from the sea by sand bars at their mouths. The present study has compared the species, genera and families represented in the fish assemblages of estuaries in south-western Australia and temperate southern Africa, i.e. below 31°S, and the way in which these estuaries are used by fish. The Clupeidae, Mugilidae, Atherinidae and Gobiidae were important families in both regions. However, the Terapontidae and Tetraodontidae, and the tropical families Apogonidae and Gerreidae, were represented by large numbers of individuals only in the estuaries of south-western Australia. Although 45 out of a total of 112 families and 32 of 233 genera occurred in both south-western Australia and temperate southern Africa, only 15 of the 326 species were found in both regions. The contributions made by the number of marine species which regularly enter estuaries in large numbers (marine estuarine-opportunists) to the total number of species recorded in the estuaries of south-western Australia and temperate southern Africa were similar (13.4 and 12.2% respectively) and the same was also true of species capable of completing their life cycles in estuaries (8.8 and 8.2%). The number of fresh water and diadromous species recorded in both regions was small. By contrast, the species of marine stragglers contributed approximately 70% to the total number of species in both regions. The adaptations of marine estuarine-opportunists and estuarine spawners to life in estuaries, and particularly to the effects of the closure of estuary mouths, is discussed. Although only one marine species was restricted to estuaries at any particular interval of its life cycle in south-western Australia, the juveniles of a number of marine species were confined to estuaries in temperate southern Africa. It is suggested that this difference can be attributed to the presence of a greater area and quality of alternative nursery habitats in the inshore marine environments in south-western Australia than in southern Africa.

Contribution of Estuaries to Commercial Fisheries in Temperate Western Australia and the Concept of Estuarine Dependence

Fisheries catch statistics for temperate Western Australia are considered in conjunction with life cycle data to elucidate the importance of estuaries to the commercial and recreational fisheries in this region. The data are used to discuss whether the term estuarine-dependent is strictly applicable to all species of finfish found in abundance in estuaries. Between 1976 and 1984, 96 species of finfish, 7 species of crustaceans and 12 species of mollusks contributed to the large commercial fishery in estuaries, protected coastal areas and open marine waters of temperate Western Australia. The mean annual weight and monetary value (in 1984 terms) of this fishery was 21,355 t and $A151.3×106. The contribution of the weight (4,340 t) and value ($A3.7×106) of the estuarine-dependent species to the total fishery was 20.3 and 2.4%, respectively. Estuarine-dependent marine species frequently use protected inshore waters in temperate Western Australia, and have to do so when they occur in subtropical regions in Western Australia where there are no permanent estuaries. Even the semi-anadromous Perth herring and some species which are estuarinesensu stricto in south-western Australia complete their life cycle within the marine waters of this latter more northern region. Since virtually none of the commercially important marine species in temperate Western Australia can be considered to be entirely dependent on estuaries, and a similar conclusion is valid for many species of marine teleosts found in abundance in estuaries in temperate waters elsewhere in the world, these marine species would be best regarded as estuarine opportunists rather than estuarine dependents.

The Johnsonieae (Liliaceae); Biology and Classification

Summary The Johnsonieae, an endemic Australasian tribe of Liliaceae is considered to be highly artificial. The Johnsonieae s.s. is restricted to the genera Arnocrinum, Hensmania, Hodgsoniola, Johnsonia and Stawellia , and is only found in temperate Western Australia. The tribes Boryeae ( Alania and Borya ) and Sowerbaeeae ( Laxmannia and Sowerbaea ) are resurrected. Tricoryne is recommended to be returned to the Asphodeleae, pending further studies.

The Role of Phytophthora Cinnamomi in Australian and New Zealand Forests

In 1922, while R. D. Rands reflected on the rather narrowly limited host relationships of the cinnamon Phytophthora he had just discovered in the mountains of tropical Western Sumatra (124), his fungus was already established some 3,000 miles to the south-east on a wide range of native plants in temperate Western Australia. Had he been able then to visit the native forests near Perth, Rands could have seen in its infancy an epidemic disease that causes wreckage in more than 100 species of the native flora and converts tall forests to virtual barrens. Yet almost half a century passed be­ fore Phytophthora cinnamomi Rands was recognized as the cause of this dis­ ease known as jarrah dieback (Figure 1) . Today Rands would find his fun­ gus unquestionably the most destructive plant pathogen ever recorded in na­ tive vegetation of this and possibly any region. It is unmatched in the variety of plants and the range of communities it affects. In marked contrast with the chestnut blight, dutch elm disease, and white pine blister rust pathogens, each epidemic on only one or two genera, P. cinnamomi kills plants in 48 families. Already it has devastated complex forest, woodland, and heath communities on more than 100,000 hectares in Western Australia (W.A.) and Victoria (Vic.) and is the cause of grave fears for the future of much of the indige­ nous vegetation of southern Australia. By contrast, in New Zealand (N.Z.) and in eastern Australia the role of the fungus i n native vegetation is less clearly understood. Although P. cinnamomi also causes serious loss in nursery crops, in coni­ fer shelterbelts, and in avocado and pineapple plantations its importance in indigenous communities dictates that the emphasis of this review should be on its role in forestry and conservation. Because this importance has been recognized only recently and research findings are yet largely unpublished we have drawn extensively on personal communication from generous colleagues who share our interest in the present distribution of P. cinnamomi, its varia­ bility, its role in a number of diseases of uncertain cause, the factors that determine the variety of its effects in the flora of our region, its indigenous or exotic origin, its potential to cause further damage, and the prospects for its control.