Australia's marine biogeography revisited: Back to the future?

The recognition of broad biogeographic provinces provides an important framework for ecological and conservation biological research. Marine biologists have long recognized distinct biogeographic provinces in southern Australia, primarily on the basis of qualitative differences in intertidal species assemblages. Here we provide an a priori test for these traditional eastern (Peronian), western (Flindersian) and south‐eastern (Maugean) provinces. Specifically, we analyse distributional data for approximately 1500 algal species using the newly available Australian Virtual Herbarium, an online database of herbarium specimens. Our quantitative algal analyses across southern Australia identify three distinct biogeographic assemblages, consistent with traditional qualitative provinces. We argue that these broad provinces provide a highly effective framework for understanding and managing Australia's marine biodiversity. In particular, biogeographic provinces provide a regional framework for integrating the ongoing discovery of biological variation at finer scales. More broadly therefore we recommend that biologists undertake quantitative analyses to test provincial biogeographic boundaries around the globe.     

THE INFLUENCE OF BAT DETECTOR BRAND ON THE QUANTITATIVE ESTIMATION OF BAT ACTIVITY

ABSTRACT

Bat detectors are commonly used to monitor bat behaviour. Earlier research has suggested that there may be systematic differences in the response of different detectors to bat calls. Such differences would have important implications for the comparability of quantitative surveys conducted with bat detectors. The present study examines variability within and between brands of bat detector in accuracy of tuning, directionality and sensitivity to different types of bat echolocation call in bat detectors from three manufacturers. The consistency of results from a field survey incorporating the three brands in a standardised methodology are also examined. Significant differences were found within and between brands in directionality and sensitivity which would lead to bias in bat surveys. The implications of these findings for bat surveys are discussed, as are the design features of importance for species identification.     

The development and persistence of alternative ecosystem states in a large,shallow lake

1. Palaeolimnological data were used to investigate drivers of the community of primary producers in Lake Mattamuskeet, North Carolina, U.S.A. This is a large, shallow lake with two basins currently dominated by phytoplankton and macrophytes. The two basins were divided in 1940 by the building of a roadway across the lake, which also corresponded with the divergence in their ecosystem state. 2. Photosynthetic pigments, organic matter and nutrients (P, N, C, S) were analysed in sediment cores from each basin to reconstruct the primary producer community over the past c. 100 years. We sought to answer two questions. First, what changes to the ecosystem resulting from the building of the roadway caused the development of different primary producer communities in the two basins? Second, why have the alternative ecosystem states persisted despite a variety of human perturbations since 1940? 3. K‐means cluster analysis and principal component analysis were applied to identify three sediment types based on photosynthetic pigment data: sediments indicating low productivity (low pigment concentrations), sediments associated with macrophytes (chlorophyll a and b) and with phytoplankton (alloxanthin and aphanizophyll). In addition, other palaeolimnological proxies measured, such as loss on ignition, total phosphorus, total organic carbon/total nitrogen and other nutrients, were different in post‐1940 sediments within the two basins. 4. These differences suggest characteristics, such as nutrient cycling, water depth and other physical changes resulting from roadway construction, combined to establish and maintain the differing communities of primary producers in the two basins. Furthermore, Fe/S dynamics and waterfowl herbivory probably contributed to the development of the two ecosystem states.     

Image analysis of aerial photography to quantify changes in channel morphology and instream habitat following placer mining in interior Alaska

1. ‘Placer’ mining for alluvial deposits of gold in a number of stream systems in interior Alaska represents a major disturbance to the stream bed and affects habitat for biotic communities. 2. The potential of analysing aerial photographs to map changes in channel habitat and morphology within gravel-bed rivers is outlined with reference to the impact and recovery of Faith Creek, a second-order stream with a history of placer mining. 3. A strong correlation between the reflectance of the channel bed and water depth is necessary to use the technique succesfully, together with a knowledge of the effects of ‘broken’water on the spectral characteristics of rivers. 4. Image analysis demonstrated that a wide range of water depths and instream mesoscale habitats existed prior to mining. During mining, the stream was confined to a channellized reach with negligible deep water or habitat diversity. 5. Since mining ceased the stream has abandoned its channellized course and formed a new channel with few deep pools. It is suggested that geomorphological recovery and associated habitat recovery takes a number of large flood events and is likely to require more than 10 years.     

Village Drift and Riverine Settlement: Modeling Akimel O'odham Land Use

Regular unscheduled movements of rancherías within a confined area or settlement district result in the phenomenon described as "village drift," a process whereby a settlement may change its location gradually by several kilometers over a period of years. This article presents a model of village drift based on data acquired from recent archaeological and geomorphological field studies and archival research on the Akimel O'odham, the Gila River Pima of south-central Arizona. The model provides an excellent example of human ecodynamics---an emerging landscape perspective that emphasizes the coevolution of humans and their ecosystem---with implications for understanding prehistoric and historic settlement in desert riverine environments.     

Glacial oceanographic contrasts explain phylogeography of Australian bull kelp

The evolutionary effects of Southern Hemisphere Pleistocene oceanographic conditions — marked by fluctuations in sea levels and water temperatures, and redirected currents — are poorly understood. The southeastern tip of Australia presents an intriguing model system for studying the biological impacts of palaeoceanography. In particular, contrasting oceanographic conditions that existed on eastern vs. western sides of the Bassian Isthmus during Pleistocene glacial periods allow for natural comparisons between putative refugial vs. re-invading populations. Whereas many western Tasmanian marine taxa were likely eliminated by cold subantarctic water during the last glacial period, eastern Tasmanian populations would have persisted in relatively warm temperatures mediated by the ongoing influence of the East Australian Current (EAC). Here we test for the effects of contrasting palaeoceanographic conditions on endemic bull kelp, Durvillaea potatorum , using DNA sequence analysis (COI; rbc L) of more than 100 individuals from 14 localities in southeastern Australia. Phylogenetic reconstructions reveal a deep (maximum divergence 4.7%) genetic split within D. potatorum , corresponding to the 'eastern' and 'western' geographical regions delimited by the Bassian Isthmus, a vicariant barrier during low Pleistocene sea levels. Concordant with the western region's cold glacial conditions, samples from western Tasmania and western Victoria are genetically monomorphic, suggesting postglacial expansion from a mainland refugium. Eastern samples, in contrast, comprise distinct regional haplogroups, suggesting the species persisted in eastern Tasmania throughout recent glacial periods. The deep east–west divergence seems consistent with earlier reports of morphological differences between 'western' and 'eastern' D. potatorum , and it seems likely that these forms represent reproductively isolated species.     

Effects of Anoxia on Wheat Seedlings: II. INFLUENCE OF O2 SUPPLY PRIOR TO ANOXIA ON TOLERANCE TO ANOXIA, ALCOHOLIC FERMENTATION, AND SUGAR LEVELS

Prior exposure of roots of intact wheat seedlings for 15–30h to hypoxia (0016-006 mol m 02) greatly increased their toleranceto subsequent anoxia, as assessed by the ability of the rootsto elongate upon return to air. Such hypoxically pretreatedroots had 2–4-fold higher activities of pyruvate decarboxylase(PDC) and 35–l7-fold higher activities of alcohol dehydrogenase(ADH) in their 0–1 mm apices and 0–5 mm root tipsthan in apices and tips of roots pretreated in air (026–031mol m3 02). The ADH/ PDC ratio increased I 3–5-fold duringhypoxic pretreatment. Furthermore, the rate of alcoholic fermentationby 0–5 mm tips of the hypoxically pretreated roots was14-4-fold faster than in tips from aerobically pretreated roots.No consistent difference between 02 pretreatment was found foralcoholic fermentation by tissues taken between 10 and 20 mmfrom the root tip. The observed activities of PDC and rates of alcoholic fermentationindicate that alcoholic fermentation is usually rate-limitedby PDC in 0–1 mm apices and 0–5 mm tips of wheatroots. Comparisons with data in the literature indicate thatwheat has at most a small Pasteur effect, which may explainwhy wheat is more intolerant to anoxia than rice. Exogenous glucose delayed the loss of elongation potential inboth aerobically and hypoxically pretreated roots. In the absenceof glucose, more than 85% of aerobically pretreated roots hadlost their elongation potential after 9 h anoxia, compared with30% in the presence of glucose. After 21 h anoxia nearly allaerobically pretreated roots had lost their elongation potential,compared with 10% and 0% of hypoxically pretreated roots inthe absence and presence, of glucose, respectively. The protective effect of glucose was presumably not due to anendogenous sugar deficiency; at the start of anoxia, 0–1mm apices of aerobically pretreated roots contained sufficientsugar for 23 h of their measured rate of ethanol synthesis yet,85% of these apices had lost their elongation potential afteronly 9 h of anoxia. It is suggested that in wheat roots, lowrates of synthesis of ethanol and hence of ATP, lead to injuryof cells, in turn generating a requirement for exogenous glucose,despite high endogenous sugar concentrations. Key words: Wheat seedlings, anoxia, glucose, O₂ pretreatment, alcoholic fermentation     

A Cretaceous crane-fly (Diptera: Tipulidae): 93 million years of stasis

A new fossil species of crane-fly, Helius botswanensis :Diptera: Tipulidaey is described. The specimen was discovered recently in reliably dated. Cretaceous sediments from Botswana. Ii is extremely well preserved, has a distinctive morphology, and is identified as belonging to the extant genus Helius. The single specimen puts the origin of the subfamily Limoniinae and the genus well into the Cretaceous Period, and provides data on the southern African Cretaceous palaeoenvironment. The conservative nature of a dipteran of such antiquity, assignable to an extant genus which has an association with flowers, has implications for evolutionary theory.