scholarly journals Patterns of demography for rocky-shore, intertidal invertebrates approaching their geographical range limits: tests of the abundant-centre hypothesis in south-eastern Australia

2010 ◽  
Vol 61 (11) ◽  
pp. 1243 ◽  
Author(s):  
Eszter Z. Hidas ◽  
David J. Ayre ◽  
Todd E. Minchinton
Keyword(s):  
Rocky Shore ◽  
Spatial Scales ◽  
Range Limits ◽  
Range Limit ◽  
Frequency Distributions ◽  
South Eastern ◽  
Size Frequency ◽  
Eastern Australia ◽  
Intertidal Invertebrates ◽  
South Eastern Australia

The abundant-centre hypothesis predicts that species' abundances peak at the centre of their geographical ranges and decline gradually towards their range limits. We tested predictions of this hypothesis for three rocky-shore, intertidal invertebrates with planktonic larvae (the whelk, Morula marginalba, the snail, Afrolittorina pyramidalis, and the barnacle, Tesseropora rosea) by quantifying their patterns of abundance and size, and inferring pulses of recruitment from size-frequency distributions, at multiple spatial scales spanning a 600-km region in south-eastern Australia and encompassing roughly the southern third of their geographical ranges. At the regional scale, abundances for all species were, as predicted, dramatically lower at their range limits. This decline was not gradual, however, because there were large variations in abundance at smaller spatial scales, and abrupt declines at the south-eastern corner of Australia. Size did not change towards the range limit for any species, but size-frequency distributions suggested a decline in the frequency of recruitment events at the range limit for T. rosea. We conclude that the abundant-centre hypothesis is not an appropriate model for abundance distributions of benthic marine invertebrates with planktonic larvae, because of the vagaries of dispersal and recruitment interacting with complex current patterns along non-uniform coastlines.

Age determination of black bream, Acanthopagrus butcheri (Sparidae), from the Gippsland Lakes of south-eastern Australia indicates slow growth and episodic recruitment

1998 ◽  
Vol 49 (6) ◽  
pp. 491 ◽  
Author(s):  
Alexander K. Morison ◽  
Patrick C. Coutin ◽  
Simon G. Robertson
Keyword(s):  
Growth Parameters ◽  
Age Determination ◽  
Correct Identification ◽  
Frequency Distributions ◽  
South Eastern ◽  
Black Bream ◽  
Eastern Australia ◽  
Episodic Recruitment ◽  
Acanthopagrus Butcheri ◽  
South Eastern Australia

The age of black bream (Acanthopagrus butcheri) in the Gippsland Lakes of south-eastern Australia was estimated with high precision from sectioned otoliths of fish sampled from 1993 to 1996. Ageing techniques were validated by following the progression of age classes over 4 years. Correct identification of the first increment was aided by reference to the position of the subcupular meshwork fibre zone, and age assignment was confirmed by linear regression analyses of otolith weight against fish age. The growth of black bream was found to be slower, and their natural life span longer, than previously estimated from length–frequency distributions and scale readings. The maximum age recorded was 29 years, with most black bream 4–9 years old and few fish more than 10 years old. There were significant differences between the growth rates of males and females. The von Bertalanffy growth parameters were: L∞ 54.5 cm FL, t0 –5.21 years, K 0.042 year-1 for females and L∞ 38.2 cm FL, t0 –3.70 years, K 0.077 year-1 for males. The current age structure suggests that recruitment has been episodic since 1981 and low for three recent years in succession.

Fire exclusion and soil texture interact to influence temperate grassland flora in south-eastern Australia

2016 ◽  
Vol 64 (5) ◽  
pp. 417 ◽  
Author(s):  
Claire Moxham ◽  
Josh Dorrough ◽  
Mick Bramwell ◽  
Brad J. Farmilo
Keyword(s):  
Soil Texture ◽  
Spatial Scales ◽  
Temperate Grassland ◽  
Management Tool ◽  
Native Plant ◽  
Temperate Grasslands ◽  
South Eastern ◽  
Eastern Australia ◽  
Fire Exclusion ◽  
South Eastern Australia

Fire has a major influence on the structure and composition of temperate grasslands and woodlands. We investigated whether the impacts of fire exclusion on a temperate grassland plant community varied according to the scale of investigation and soil texture. Ten sites with known fire histories were selected along a soil texture gradient in south-eastern Australia. Floristics and ground layer attributes were investigated at small (0.25 m2) and large (100 m2) spatial scales in regularly burnt and unburnt grasslands. Fire exclusion over a 10 year period led to declines in native species diversity, richness and cover at both spatial scales and in most cases effects were consistent regardless of soil texture. However, the richness of native plant species at small scales and the cover of native plants at large scales were most negatively influenced by fire exclusion on fine textured soils. Conversely, at large scales, exotic plant richness and cover were only weakly increased by fire exclusion. Responses of eight common species were modelled and in seven of these, fire exclusion was a strong predictor of occurrence, although both positive and negative responses were observed. These results reiterate the importance of frequent fire as a management tool in temperate grasslands, but also shed light on how sites may require specific fire management regimes depending on the underlying soil texture.

Temporal and spatial variation in the abundance of fish associated with the seagrass Posidonia australis in South-eastern Australia

1993 ◽  
Vol 44 (6) ◽  
pp. 881 ◽  
Author(s):  
DJ Ferrell ◽  
SE McNeill ◽  
DG Worthington ◽  
JD Bell
Keyword(s):  
Spatial Variation ◽  
Spatial Scales ◽  
Seagrass Beds ◽  
Beam Trawl ◽  
Management Decisions ◽  
Temporal And Spatial Variation ◽  
South Eastern ◽  
Eastern Australia ◽  
Temporal And Spatial ◽  
South Eastern Australia

A beam trawl was used to sample fish associated with the seagrass Posidonia australis between September 1988 and June 1990. We describe variation in abundance of fish at two spatial scales: among three seagrass beds 1-10 km apart within each of three estuaries, and among the estuaries separated by at least 100 km. Most species had significant differences in abundance among sites and estuaries that changed through time. However, many species also had consistent patterns in abundance among sites and among estuaries. For example, there were large and consistent differences in the abundance of many species among the three estuaries. Widespread changes in abundance (ie: changes that took place at all sites within an estuary or in most estuaries) were not common. The two spatial scales used in this study are also logical scales for management of seagrass habitats. The consistent differences in abundance of some fish found at both spatial scales will complicate management decisions.

Modelling the abundance of wildlife using field surveys and GIS: non-native sambar deer (Cervus unicolor) in the Yarra Ranges, south-eastern Australia

2009 ◽  
Vol 36 (3) ◽  
pp. 231 ◽  
Author(s):  
David M. Forsyth ◽  
Steve R. McLeod ◽  
Michael P. Scroggie ◽  
Matthew D. White
Keyword(s):  
Predictive Model ◽  
Spatial Scales ◽  
Strong Support ◽  
Geographic Information ◽  
Field Surveys ◽  
Faecal Pellets ◽  
South Eastern ◽  
Eastern Australia ◽  
Sambar Deer ◽  
South Eastern Australia

Combining abundance data collected in designed field surveys with biophysical data derived from geographic information systems is a powerful way to investigate predictors of spatial variation in the abundance of wildlife. We used such an approach to evaluate hypotheses about factors influencing the abundance of sambar deer (Cervus unicolour Kerr, 1792), a large non-native herbivore, in south-eastern Australia. We developed a spatial model for the abundance of sambar deer faecal pellets in a 3650-ha area in the Upper Yarra Ranges, Victoria. We counted the number of sambar deer faecal pellets along 100 randomly located transects and used a geographic information system to estimate biophysical variables around each transect. We formulated our hypotheses about how those variables might affect the abundance of sambar deer pellets into 22 candidate models and used the deviance information criterion to identify the ‘best’ model(s). Because five models had strong support we used model averaging to generate a predictive model. The three variables included in the predictive model were aspect (abundance of pellets declined with increasing ‘northerliness’ and increased with increasing ‘easterliness’), distance to water and elevation; the latter two variables were positively correlated and had a negative effect on the abundance of pellets. In contrast to previous models of sambar deer abundance in south-eastern Australia, our spatial predictions of the abundance of faecal pellets can be easily tested and updated. Our approach would be useful for modelling the abundances of other wildlife species at a range of spatial scales.

scholarly journals Linking population size structure, heat stress and bleaching responses in a subtropical endemic coral

Coral Reefs ◽  
2021 ◽  
Author(s):  
Liam Lachs ◽  
Brigitte Sommer ◽  
James Cant ◽  
Jessica M. Hodge ◽  
Hamish A. Malcolm ◽  
...  
Keyword(s):  
Heat Stress ◽  
Size Structure ◽  
Temporal Trends ◽  
Early Recovery ◽  
Size Frequency Distribution ◽  
Frequency Distributions ◽  
Community Organisation ◽  
Size Frequency ◽  
Eastern Australia

AbstractAnthropocene coral reefs are faced with increasingly severe marine heatwaves and mass coral bleaching mortality events. The ensuing demographic changes to coral assemblages can have long-term impacts on reef community organisation. Thus, understanding the dynamics of subtropical scleractinian coral populations is essential to predict their recovery or extinction post-disturbance. Here we present a 10-yr demographic assessment of a subtropical endemic coral, Pocillopora aliciae (Schmidt-Roach et al. in Zootaxa 3626:576–582, 2013) from the Solitary Islands Marine Park, eastern Australia, paired with long-term temperature records. These coral populations are regularly affected by storms, undergo seasonal thermal variability, and are increasingly impacted by severe marine heatwaves. We examined the demographic processes governing the persistence of these populations using inference from size-frequency distributions based on log-transformed planar area measurements of 7196 coral colonies. Specifically, the size-frequency distribution mean, coefficient of variation, skewness, kurtosis, and coral density were applied to describe population dynamics. Generalised Linear Mixed Effects Models were used to determine temporal trends and test demographic responses to heat stress. Temporal variation in size-frequency distributions revealed various population processes, from recruitment pulses and cohort growth, to bleaching impacts and temperature dependencies. Sporadic recruitment pulses likely support population persistence, illustrated in 2010 by strong positively skewed size-frequency distributions and the highest density of juvenile corals measured during the study. Increasing mean colony size over the following 6 yr indicates further cohort growth of these recruits. Severe heat stress in 2016 resulted in mass bleaching mortality and a 51% decline in coral density. Moderate heat stress in the following years was associated with suppressed P. aliciae recruitment and a lack of early recovery, marked by an exponential decrease of juvenile density (i.e. recruitment) with increasing heat stress. Here, population reliance on sporadic recruitment and susceptibility to heat stress underpin the vulnerability of subtropical coral assemblages to climate change.

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