Reproductive Phenology of Woody Species in a North Australian Tropical Savanna1

Interspecific and interannual variation in reproductive phenology was quantified for 50 common species of trees and shrubs from a mesic savanna near Darwin, northern Australia. The presence of buds, flowers, and fruit was noted over a 30-month period, from September 1992 to February 1995. Surveys were undertaken at monthly intervals for the less common species, and at bimonthly intervals for ten of the common trees and tall shrubs. The majority of species flowered each year at about the same time. There was no evidence of sub-annual or continuous regimes of reproductive phenology. There was no supra-annual carryover of seed-bearing fruit in the canopy of any species. The peak flowering periods were the mid to late dry season (July–August) and the transition between the dry season and the wet season (October–November). The two dominant trees–Eucalyptus miniata and E, tetrodonta– flowered during the dry season, thereby providing resources for some elements of the vertebrate fauna. Flowering and fruiting were uncommon at the end of the wet season (February/March), although two species that flower and fruit at this time (E. porrecta and Terminalia ferdinandianas may provide resources to consumers at a time when floral or fruit resources are otherwise scarce. Because the peak of reproductive activity takes place during the late dry season, fruit maturity and seed dispersal have occurred prior to the onset of the rainy season for most species, and germination and seedling establishment potentially may take effect in response to the first rains. Late dry season fires, which tend to be extensive and intense, are a potential threat to the floral and fruit reserves within these savannas.     

Antarctic patterns of shallow subtidal habitat and inhabitants in Wilke’s Land

Studies of east Antarctic marine assemblages on hard substrata are rare. In relation to sea-ice breakout, we assessed benthic patterns of habitat and inhabitants between islands and bays at each of two depths (6 and 12 m) across the Windmill Islands coast. Island sites experience sea-ice breakout in the austral spring, while bay sites typically retain sea-ice cover into the summer and in some places the cover is virtually permanent. Composition of assemblages differed between sheltered bays and exposed islands. Islands were dominated by macroalgae, which also varied with depth. Immediately below the ice–foot zone at 6 m, substratum space were monopolised by foliose red (Palmaria decipiens) and foliose brown (Desmarestia sp.) algae, whereas at 12 m large canopies of Himantothallus grandifolius was abundant. The understorey consisted of a mixture of turfs and encrusting red algae at 6 m, and coralline algae at 12 m. Sheltered bays had large areas of sediment/algal complex and no canopy-forming macroalgae. We found more sponges and hydroids in bays, and more brittle stars around islands. Experiments testing factors that covary with exposure and depth in Antarctica, such as light, sedimentation and ice scour are necessary to determine processes that maintain these striking patterns.     

Approaches to resolving cephalopod movement and migration patterns

Cephalopod movement occurs during all phases of the life history, with the abundance and location of cephalopod populations strongly influenced by the prevalence and scale of their movements. Environmental parameters, such as sea temperature and oceanographic processes, have a large influence on movement at the various life cycle stages, particularly those of oceanic squid. Tag recapture studies are the most common way of directly examining cephalopod movement, particularly in species which are heavily fished. Electronic tags, however, are being more commonly used to track cephalopods, providing detailed small- and large-scale movement information. Chemical tagging of paralarvae through maternal transfer may prove to be a viable technique for tracking this little understood cephalopod life stage, as large numbers of individuals could be tagged at once. Numerous indirect methods can also be used to examine cephalopod movement, such as chemical analyses of the elemental and/or isotopic signatures of cephalopod hard parts, with growing interest in utilising these techniques for elucidating migration pathways, as is commonly done for fish. Geographic differences in parasite fauna have also been used to indirectly provide movement information, however, explicit movement studies require detailed information on parasite-host specificity and parasite geographic distribution, which is yet to be determined for cephalopods. Molecular genetics offers a powerful approach to estimating realised effective migration rates among populations, and continuing developments in markers and analytical techniques hold the promise of more detailed identification of migrants. To date genetic studies indicate that migration in squids is extensive but can be blocked by major oceanographic features, and in cuttlefish and octopus migration is more locally restricted than predictions from life history parameters would suggest. Satellite data showing the location of fishing lights have been increasingly used to examine the movement of squid fishing vessels, as a proxy for monitoring the movement of the squid populations themselves, allowing for the remote monitoring of oceanic species.