Books for Review

BookReview

Books for Review     

Territory takeover and sexually selected infanticide in tropical house wrens

Summary Tropical house wrens in lowland central Panama are, with rare exception, permanently monogamous. During a 3-year demographic study of 54–56 pairs of these brids, both males and females committed infanticide in association with takeover of breeding territories. New males and new females replaced previously identified (color-banded) parents before the termination of parental care in 13% of 328 breeding attempts. Replacement was accomplished by physical takeover in at least some if not all cases. Total nest failure at the egg, nestling, or fledgling stage occurred in 73% of the male replacements and 70% of the female replacements. Nest predation was excluded as a possible cause of nest failure. 76% of male replacements and 50% of female replacements bred in the same season. Infanticidal replacement males bred sooner than did non-infanticidal males arriving at similar stages of the nesting cycle. Contexts in which infanticide occurred included takeovers by first-year males and females of territories and mates, re-entry into the breeding population by males that had recently lost their mates, acquisition of neighboring females by bigamous males, and the elimination of one female of a bigamous male by the other. Sexually selected infanticide in these birds is promoted by a lengthy breeding season and extremely limited breeding opportunities for individuals not already part of the breeding population. Mate limitation appears to be more important than habitat or nestsite limitation in restricting new breeding opportunities once the breeding season has begun.     

Fish assemblages in seagrass beds are influenced by the proximity of mangrove forests

Mangrove forests and seagrass beds frequently occur as adjacent habitats in the temperate waters of southeastern Australia. At low tide when fish cannot occupy mangroves they might utilise adjacent habitats, including seagrass. We first sampled small fish from seagrass beds close to and far from mangroves in the Pittwater estuary, NSW, Australia. Seagrass beds close to mangroves had a greater density of fish species than beds far from mangroves (close: mean 16.0 species net⁻¹, SE 1.0; far: 13.2, 1.3; P < 0.05). In particular, juvenile fish were in greater densities near to than far from mangroves (close: 5.3, 0.4; far: 3.1, 0.4; P < 0.05). We then sampled the mangrove forests during the high tide and seagrass beds during the low tide, in beds along a continuum of distances from mangroves. Multivariate analysis showed that fish assemblages differed with distance from mangroves, and the differences were attributed to the composition of the fish assemblage (i.e. presence/absence of fish species), not the abundances of individual species. In particular, fish that utilise mangrove forests at high tide were found in greater species densities and species richness in seagrass nearer to mangroves. A negative relationship was found between the density of mangrove-utilising fish species and the distance of the bed from mangroves (R ² = 0.37, P < 0.05). This confirms the important connectivity between mangroves and seagrass for fish in temperate Australian waters.     

Application of a coastal model to simulate present and future inundation and aid coastal management

This paper describes the application of coastal hydro-informatic modelling (using the TELEMAC Modelling System) to address management issues arising from projected hydrodynamical and morphological changes within a shallow, sandy estuarine environment. The model incorporates the complex interaction of ocean, terrestrial and atmospheric processes. The case study of the Dyfi Estuary, on the west coast of Wales, is highlighted here. As sea levels have risen locally and are predicted to rise further, a National Nature Reserve (Borth Bog), which has been reclaimed from tidal waters by embankments, will be at increasing risk from flooding episodes due to overtopping of these embankments at high tide. Present and predicted future tidal-fluvial scenarios have been modelled in the Dyfi Estuary in order to estimate the potential for flooding. In addition, areas of greatest velocity change and potential for sediment erosion/accretion have been identified. A further process that has been investigated is how salt marsh migration is affected by sea-level rise. This case study exemplifies some fundamental and complex physical processes inherent to estuaries, and shows how different management options can be assessed, before their implementation, through a modelling approach.     

Habitat selectivity of megalopae and juvenile mud crabs (<Emphasis Type="Italic">Scylla serrata</Emphasis>): implications for recruitment mechanism

Megalopae of several crab species exhibit active habitat selection when settling. These megalopae usually select structurally complex habitats which can provide refuge and food. The portunid mud crab, Scylla serrata, is commonly found within the muddy estuaries of the Indo-West Pacific after attaining a carapace width >40 mm. Despite substantial efforts, the recruitment mechanism of juvenile mud crabs to estuaries is not understood because their megalopae and early stage crablets (carapace width <30 mm) are rarely found. We used laboratory experiments to determine whether megalopae and early stage crablets are selective among three estuarine habitats which commonly occur in Queensland, Australia. These animals were placed in arenas where they had a choice of habitats: seagrass, mud or sand, and arenas where they had no choice. Contrary to the associations exhibited by other portunid crab megalopae, S. serrata megalopae were not selective among these estuarine habitats, suggesting that they tend not to encounter these habitats, or, gain no advantage by selecting one over the others. The crablets, however, strongly selected seagrass, suggesting that residing within seagrass is beneficial to the crablets and likely increases survival. This supports the model that for S. serrata, crablets and not megalopae tend to colonise estuaries, since a selective behaviour has evolved within crablets but not megalopae.     

Spatio-temporal patterns of juvenile marine turtle occurrence in waters of the European continental shelf

We present data spanning approximately 100 years regarding the spatial and temporal occurrence of marine turtle sightings and strandings in the northeast Atlantic from two public recording schemes and demonstrate potential signals of changing population status. Records of loggerhead (n = 317) and Kemp’s ridley (n = 44) turtles occurring on the European continental shelf were most prevalent during the autumn and winter, when waters were coolest. In contrast, endothermic leatherback turtles (n = 1,668) were most common during the summer. Analysis of the spatial distribution of hard-shell marine turtle sightings and strandings highlights a pattern of decreasing records with increasing latitude. The spatial distribution of sighting and stranding records indicates that arrival in waters of the European continental shelf is most likely driven by North Atlantic current systems. Future patterns of spatial-temporal distribution, gathered from the periphery of juvenile marine turtles habitat range, may allow for a broader assessment of the future impacts of global climate change on species range and population size.     

Nutrient budgets: sustainability assessment of rainfed lowland rice-based systems in northeast Thailand

In northeast Thailand, the sustainability of rainfed lowland rice-based systems, the dominant land-use system (LUS) in the region, is a concern for the welfare of the population in this relatively poor region. Poor soil fertility and low inputs are seen as major causes of this lack of sustainability. In this context, the assessment of nutrient budgets is seen as a powerful tool for the assessment of critical components of the sustainability of this particular LUS. Biophysical, socioeconomic, and management-related data on the farming systems were collected for 30 farms in Ubon Ratchathani Province, northeast Thailand. A relational database system (RDBS) was developed to manage and analyze the data. The RDBS includes a calculation procedure for the semi-automatic generation of partial nutrient balances. Partial nutrient balances are good indicators for some critical components of sustainability, and important for decision support on soil fertility management when considered with the additional factors that are required for a full nutrient balance.For the rice-based systems of 30 farms, mean partial balances were 12 kg N ha⁻¹, 8 kg P ha⁻¹, and 7 kg K ha⁻¹ per year. Large variations in partial N, P, and K balances exist among different farms and, even more so, for different land utilization types (LUTs). The LUTs are distinct cropping system–management combinations that occur down to the subfield level. Many of the partial balances assessed were negative.Farmers manage nutrients for similar parcels of land in very different ways. This results in the observed large variation in partial nutrient balances, even for the same type of land use within the same farm. These results confirm the high inter-farm and intra-farm variability for partial balances of N, P, and K of several preliminary studies. Farmer interviews and field surveys revealed that different socioeconomic factors appear to be related with inter- and intra-farm variability in nutrient budgets. In addition, the socioeconomic component of the case study revealed that diversification of income sources, particularly off-farm employment, had a larger impact on household income than rice production. Furthermore, while many less well-off households had a greater reliance on rice production, many farms with high off-farm and non-rice farm income had a higher total production of rice.The nutrient balance approach, starting with partial nutrient balances, may become an important component of a dynamic and site-specific decision support tool (DST) for nutrient management, and a relational database of the form used in this study may become a key element.     

A mark-recapture study of male<Emphasis Type="Italic"> Colletes cunicularius</Emphasis> bees: implications for pollination by sexual deception

An unusual pollination strategy is pollination by sexual deception in which orchids sexually attract male insects as pollinators. One gap in knowledge concerns the pattern and extent of pollinator movement among these sexually deceptive flowers and how this translates to pollen and gene flow. Our aim was to use mark and recapture techniques to investigate the behavior and movement of male Colletes cunicularius, an important bee pollinator of Ophrys. Our study site was located in northern Switzerland where a large population of the bees was nesting. Within two plots, (10×40 m), we marked bees with different colors and numbered tags. Seventeen percent of the 577 marked bees were recaptured over a period of 1 to a maximum of 11 days. However, the number of recaptures dropped dramatically after 3–5 days, suggesting an average lifetime of less than 10 days. Mark-recapture distances varied from 0 to 50 m, with a mean of 5 m. Our findings show that individual male bees patrol a specific and restricted region of the nesting area in search of mates. This mark-recapture study provides the first clues about the potential movement of pollen within populations of Ophrys orchids. We predict that orchid-pollen movements mediated by bees will be similar to the mark-recapture distances in this study. Parallel studies within orchid populations, including direct studies of pollen movement, are now required to better understand how pollinator mate-searching behavior translates to pollination success and pollen movement within sexually deceptive orchid populations.Communicated by R.F.A. Moritz     

Food webs supporting fish over subtropical mudflats are based on transported organic matter not in situ microalgae

We present here a morpho-functional and behavioural study of the feeding adaptations developed by a deep-sea invertebrate, the caprellid amphipod Parvipalpus major, in an environment temporarily deprived of external food supply. The animals were taken intact from bathyal muddy sediments using a classic Barnett multi-tub corer at depths ranging from 424 to 761 m. They were transferred to the laboratory, kept in tanks with their native sediment at a constant temperature (10°C) and their behaviour was studied by video analysis. Their morphology consists of elongated somites, with pereopods 5–7 ending in elongated curved dactyls, which are longer than those of more coastal species. Analysis of the literature shows that the largest caprellids inhabit the deepest and muddiest zones. This particular morpho-functional adaptation enables the species to adopt an originally erect and steady stance by fixing onto soft muddy sediment, thus improving its ability to prospect for food in its surrounding environment. For the most part, P. major balances its body at its anchorage point as it searches for food in the water column, but occasionally it bends down to the substrate, and tosses some sediment into the water column. Food is then selected from the particles that float down. Presumably, after exhausting the food supply in one area, the animal jumps into the water column and moves about a body length further on. This would appear to be an original strategy for foraging larger areas of organic matter from fixed, but temporary, positions. Finally, we show that caprellids are able to practise coprophagy. To conclude, we suggest that there is a positive correlation between body elongation and depth, with improved anchoring and coprophagy being an optimal way to conserve energy in conditions of limited diet and improve adaptation to life on deep-sea muddy bottoms.Communicated by S.A. Poulet, Roscoff     

Evaporation of solutes from water

A model is developed to define the evaporation rates of solutes from water. The rate equation, similar in form to the Knudsen equation, takes into consideration the effect of air and subwater turbulences on the evaporation loss. At given system conditions, the factor accounting for the air turbulence appears to be essentially constant and independent of temperature (3.5–25°C) for various organic chemicals and water. These characteristics allow one to study the rate of evaporation from water and the relative enhancement by subwater mixing for different solutes. This report shows that the volatilization loss of pure substances and solutes with low Henry's law constants is enhanced by air turbulence, not by subwater mixing. However, the loss of volatile solutes (high Henry's law constants) may be promoted both by air turbulence and by subwater mixing, in which the extent of enhancement by liquid mixing is determined primarily by the Henry's law constant. The present model provides a theoretical basis to explain these effects and others, which appear to be important for assessment of pollutant evaporative transport in the environment.