Prolonged inundation and ecological changes in an Avicennia mangrove: implications for conservation and management

The mangrove around Sungei Pemburongunan, just west of Tanjong Batu and Istana Darul Aman in the Brunei-Muara District, is unique in that it contains the only pure stand of Avicennia marina in Brunei Darussalam. In mid-October, 1990 the mouth of Sungei Pemburongunan was closed due to a natural build-up of a sandbar across it. The mangrove quickly became flooded and adverse effects on the flora and fauna were observed during the following weeks. In mid-December a channel was dug across the sand bar to reduce the flooding and normalise the ecology. Some of the dying Avicennia and Lumnitzera have since recovered but others such as Acrostichum and Casuarina have not. Avicennia showed some interesting responses to prolonged inundation. Many of the Avicennia that had flowered during the flood produced seedlings which are now well rooted and 40–80 cm in height. The survival of large numbers of these seedlings is attributed to the floor-related decrease in the number of grapsid and sesarmid crabs which predate on them. The crab and mollusc populations have largely recovered. Unlike periodic short-term flooding which does not seem to have any apparent adverse affect on the ecosystem, prolonged inundation can result in the loss of the Avicennia and its associated flora and fauna. Thus, fragile mangrove ecosystems such as this need to be monitored and managed closely.This work demonstrates that contrary to conventional wisdom, human intervention and management can be beneficial to more fragile ecosystems, which could otherwise succumb to natural processes. Furthermore, it highlights the importance of the dynamic nature of the environment which should be considered in management and conservation programmes.     

Threat-sensitive anti-intraguild predation behaviour: maternal strategies to reduce offspring predation risk in mites

Predation is a major selective force for the evolution of behavioural characteristics of prey. Predation among consumers competing for food is termed intraguild predation (IGP). From the perspective of individual prey, IGP differs from classical predation in the likelihood of occurrence because IG prey is usually more rarely encountered and less profitable because it is more difficult to handle than classical prey. It is not known whether IGP is a sufficiently strong force to evolve interspecific threat sensitivity in antipredation behaviours, as is known from classical predation, and if so whether such behaviours are innate or learned. We examined interspecific threat sensitivity in antipredation in a guild of predatory mite species differing in adaptation to the shared spider mite prey (i.e. Phytoseiulus persimilis, Neoseiulus californicus and Amblyseius andersoni). We first ranked the players in this guild according to the IGP risk posed to each other: A. andersoni was the strongest IG predator; P. persimilis was the weakest. Then, we assessed the influence of relative IGP risk and experience on maternal strategies to reduce offspring IGP risk: A. andersoni was insensitive to IGP risk. Threat sensitivity in oviposition site selection was induced by experience in P. persimilis but occurred independently of experience in N. californicus. Irrespective of experience, P. persimilis laid fewer eggs in choice situations with the high- rather than low-risk IG predator. Our study suggests that, similar to classical predation, IGP may select for sophisticated innate and learned interspecific threat-sensitive antipredation responses. We argue that such responses may promote the coexistence of IG predators and prey.     

Home range area in the tortoise Testudo hermanni in relation to habitat complexity: implications for conservation of biodiversity

The tortoise Testudo hermanni is endangered by habitat fragmentation and loss in western Europe, where its high public profile and specific conservation projects make this a flagship species. Studies of movement in the peak reproductive season (June) showed that home ranges were substantially larger in France than in Greece. This difference was due to the intensity of use of the home range, not to the distance moved which was remarkably similar in the two areas. There was no sexual difference in home range area. The home range was therefore not large in France because of movement to nesting sites, but rather for utilization of the greater habitat complexity there. The need for reserves to include different vegetation types makes conservation of T. hermanni in France more difficult. Conversely, the need for large reserves increases its value as an umbrella species for conservation of biodiversity.     

Diel activity of adult pikeperch <Emphasis Type="Italic">Sander lucioperca</Emphasis> (L.) in a drainage canal in the Mediterranean basin during spring

Pikeperch (Sander lucioperca L.) is a broadly distributed fish species in Europe but little is known about its ecology in the southern part of its distribution area in warm climatic conditions. The aim of this study was to analyse pikeperch rate of movement and to assess whether it displayed a diel pattern related to temperature. Thus acoustic telemetry was used to track adult pikeperch in a drainage canal located in south of France. The survey was carried out in spring, during the spawning period. The results showed that females were more active than males. This is in accordance with previous data on the nest guardian behaviour of the males. For both genders, the activity rates increased during the study period as water temperature rose. Males and females displayed the same diel activity with a maximum at dusk, thereby confirming many indirect observations. Nevertheless, inter-individuals variations were observed. Thus, these results on diel activity are rather a general trend than a strict rule and suggest the involvement of other factors than light intensity in the control of diel activity. This diel rhythm is positively correlated to water temperature for females. Pikeperch activity may be the result of a trade-off between physiological requirements of temperature and light, satisfaction of energy needs and avoidance of predators.     

Allozyme variability in central, peripheral and isolated populations of the scarce heath (Coenonympha hero: Lepidoptera, Nymphalidae); implications for conservation

Genetic drift tends to lower geneticvariability in peripheral and isolatedpopulations. These populations also tend todiverge from more central populations if thedegree of isolation is high enough. Theseprocesses could have opposite effects on thevalue of the respective populations in thespecies conservation context. On the basis ofallozyme polymorphism data, we compare geneticvariability and differentiation between core,peripheral and isolated populations of thescarce heath, a butterfly endangered inNorthern and Central Europe. Genetic variationwas lowest in populations that were bothperipheral and isolated(P = 16.5%, Hobs = 0.017),and highest in the central populations(P = 35%,Hobs = 0.052). However, overall variability waslow also in the core area compared to that ofclosely related butterfly species. Theperipheral region was more differentiated fromthe other regions than the isolated region(F_PC = 0.118, F_PI = 0.257,F_IC = 0.068). This study indicated thatisolation in combination with marginality havecaused an erosion of the gene pool. Theobserved patterns may be caused both by thecontemporary population structure of thespecies, as well as by the colonisationhistory. Both genetic and ecological evidencesuggests that the species is likely to followthe stepping-stone model of dispersal.     

Population dynamics, reproduction, and diet of the lesser long-nosed bat (Leptonycteris curasoae) in Jalisco, Mexico: implications for conservation

We estimate fluctuations in population size and sex ratio, documentbreeding behavior and reproduction, and determine the diet of a population ofthe lesser long-nosed bat, Leptonycteris curasoae, in anisland cave in Chamela Bay, Jalisco, Mexico, with monthly sampling during anannual cycle (October 1999–October 2000). Based on the area of thecave's ceiling and wall covered with L. curasoae inrelation to the potential roost area without them, in 1999 the abundanceincreased from 80% in October to 100% in November and December. In 2000 thepopulation decreased to 80% in January, 50% in February, 30% in March, 20% inApril, 10% in May, 5% in June and July, and less than 1% in August. Thepopulation rapidly increased to 60% in September and to 80% in October.Throughout the year there were significantly more males than females; however,there was significant heterogeneity over months. In September–Novemberthere were more females, but in December–August there were more malespresent. The majority of pregnant and lactating females were observed fromDecember to March and in July, while males were reproductive fromSeptember–January and in May–June. Breeding activity was observed inthe cave in November–December. Twenty-six species of plants were consumedduring the year, based on pollen identification from fecal samples. Bombacaceousspecies were the most important component of the diet from January to May andCactaceae were most important in June–September. Peak abundance and reproductive activitycoincided with peak flower resource availability, which occurred between Octoberand January and in June–July. The year-round presence and reproductiveactivity of L. curasoae at this site throughout the yeardemonstrate that many individuals are annual residents in this area and indicatethe importance of this roosting site. In order to develop a successfulconservation program for L. curasoae, in addition toprotecting migratory corridors and northern maternity roosts, it is equallyimportant to identify and protect areas that function as breeding colonies andyear-round sanctuaries for resident populations in the south.     

Testing population-level mechanisms of invasion by a mobile vertebrate: a simple conceptual framework for salmonids in streams

Invasion biology suffers from a lack of the ability to predict the outcome of particular invasions because of reliance on verbal models and lack of rigorous experimental data at the appropriate scale. More progress is likely to be made by considering invasions as population-level phenomena and initially focusing on specific taxa or particular categories of invasions. To this end, we propose a simple conceptual framework to motivate studies of invasion by salmonids (salmon, trout, grayling, and whitefish) in streams that emphasizes population-level mechanisms affecting native species and promoting spread by the invader. Specifically, the only direct mechanisms by which the abundance of the native species can decline are through biotic interactions which cause decreased reproductive rates or survival at specific life stages, net emigration, debilitating or fatal diseases introduced by the invader, or a combination of these factors. Conversely, abundance of the invader must increase by local reproduction, high survival, net immigration, or a combination of these factors. Review of existing salmonid invasion literature suggests that future studies could be improved by using manipulative field experiments at a spatial and temporal scale appropriate to address population-level processes, characterizing how movement affects the establishment and spread of an invader, and including abiotic context in experimental designs. Using the example of brook trout (Salvelinus fontinalis) invasion into streams containing native Colorado River cutthroat trout (Oncorhynchus clarki pleuriticus) in the central Rocky Mountains (USA), we demonstrate how the framework can be used to design a manipulative field experiment to test for population-level mechanisms causing ecological effects and promoting invasion success. Experiments of this type will give invasion ecologists a useful example of how a taxon-specific invasion framework can improve the ability to predict ecological effects, and provide fishery biologists with the quantitative foundation necessary to better manage stream salmonid invasions.     

Fecal pellet production between molts in a cyclopoid copepod: patterns, individual variability and implications for growth and development

We measured the fecal pellet production rate (FPR) of a cyclopoid copepod (Cyclops cf. sibiricus) individually through the copepodite 5th stage in order to describe the molt-cycle dependent variations in the FPR and the relationship between the FPR and growth and development. Even though individuals of C.cf. sibirucus were kept in the same environmental condition (food quantity, etc.) throughout the development, the FPR was not constant. In general, the FPR was low just after molting into C5, but increased with time and reached the maximum a few days after the molt, and then decreased toward the next molt. More fecal pellets were produced during the earlier part of stage duration time, irrespective of variations in the stage duration time. The total volume of fecal pellets voided through C5 (tCFP) also varied individually with females tending to void more than males. However, neither the weight-specific FPR nor the weight-specific tCFP were different between the sexes. The weight-specific FPR was positively correlated with the individual stage-specific growth rate, suggesting that better growers had a higher ingestion rate, given that the FPR is proportional to the ingestion rate as suggested by other studies.     

Habitat Selection by the Spur-thighed Tortoise Testudo graeca in a Multisuccessional Landscape: Implications for Habitat Management

As a result of human activities, natural Mediterranean landscapes (including agro-ecosystems) are characterised by a mosaic-like structure with habitat-patches at different successional stages. These systems have high biodiversity levels and are home to a large number of species protected by European laws whose habitats should be adequately managed. In the present work, we study habitat use from an applied point of view in the spur-thighed tortoise Testudo graeca, an endangered reptile present in semi-arid Mediterranean agro-ecosystems. Results show that, at a landscape scale, the species selects simplified vegetation structures and includes in its home range re-colonisation shrubland and small non-irrigated fields. Within the home range, habitat selection patterns vary and areas with higher vegetation cover and complexity are selected. Detected patterns are discussed in terms of the ecological requirements of the species and with a hierarchical view of resources and conditions. The implications of our findings for habitat management aimed at the conservation of the species are also discussed.     

Spatial variability in the nutrient composition of Populus tremuloides: clone-to-clone differences and implications for cervids

Summary Populus tremuloides, a clonal angiosperm, is a major food item for many temperate-region herbivores. Clonal variation in chemical composition has potentially important implications for vertebrate herbivores because a single clone may be areally large and hence, may comprise a large part of available forage. The objectives of this study were: (1) to examine spatial variability in nutrient concentrations and quality within and among 24 clones of trembling aspen, and (2) to evaluate these differences with respect to cervid nutritional requirements; notably Cervus elaphus and Odocoileus hemionus. Between-clone concentrations of all chemical components were significantly different. In terms of cervid nutrition, most clones provided adequate concentrations of Ca, Mg, Mn, and Zn. Crude protein was limiting in some clones and P in most. Additionally, P metabolism may be impaired by the high Ca:P ratios typical of some clones. Of the structural constituents, neutral detergent fiber showed the greatest intraclonal variability. Dry-matter digestibility varied sufficiently to conjecture that cervid energy balances may be affected. Overall, although clone-to-clone differences were not so substantial to conclude that selective browsing would be nutritionally cost-effective, it is proposed that cervids stand to benefit by fortuitously browsing on nutritionally superior clones owing to the multiplier effect.     

Temporal and spatial variability in stable isotope compositions of a freshwater mussel: implications for biomonitoring and ecological studies

Stable isotopes can be used to elucidate ecological relationships in community and trophic studies. Findings are calibrated against baselines, e.g. from a producer or primary consumer, assumed to act as a reference to the isotopic context created by spatio-temporal attributes such as geography, climate, nutrient, and energy sources. The ability of an organism to accurately represent a community base depends on how, and over what time-scale, it assimilates ambient materials. Freshwater mussels have served as references for trophic studies of freshwater communities and as indicators of change in nutrient pollution load or source. Their suitability as reference animals has not yet been fully explored, however. We conducted a series of studies examining the suitability of freshwater mussels as isotopic baselines, using their ability to reflect variation in ambient nutrient loads as a case scenario. (1) We analyzed bivalve foot tissue δ¹⁵N and δ¹³C from 22 stream reaches in the Piedmont region of North Carolina, USA to show that compositions varied substantially among locations. Site mean bivalve δ¹³C values correlated with site ambient particulate organic matter (POM) δ¹³C values, and site mean bivalve δ¹⁵N values correlated with site ambient water dissolved δ¹⁵N-NO₃ values. (2) Similarity of results among sample types demonstrated that the minimally invasive hemolymph sample is a suitable substitute for foot tissue in δ¹⁵N analyses, and that small sample sizes generate means representative of a larger population. Both findings can help minimize the impact of sampling on imperiled freshwater mussel populations. (3) In a bivalve transplantation study we showed that hemolymph δ¹⁵N compositions responded to a shift in ambient dissolved δ¹⁵N-NO₃, although slowly. The tissue turnover time for bivalve hemolymph was 113 days. We conclude that bivalves serve best as biomonitors of chronic, rather than acute, fluctuations in stream nutrient loads, and provide initial evidence of their suitability as time-integrated isotopic baselines for community studies.     

The population dynamics of Cheilosia fasciata (Diptera,Syrphidae): significance of environmental factors and behavioural adaptations in a phytophagous insect

Summary A population of Cheilosia fasciata Schin. & Egg., 1853 was studied in a beech forest (Melico-Fagetum allietosum) near Göttingen (FRG). This syrphid species is closely associated with ramson (Allium ursinum L.), as the larvae mine the plant's leaves. Adult abundance was determined using emergence traps (1981–1986); egg and larval abundance was determined by examining ramson leaves: puparia were extracted from soil samples (1984 and 1986). Cheilosia fasciata is a univoltine species; the imagines emerge in late April/early May. Larval development took five (1986) to six (1984) weeks. In late June/early July the larvae enter the soil for pupariation. A linear relationship was found between the area of the mines and larval biomass (dry wt.). It was concluded that one larva had to mine 51.90 cm² of leaf area in order to gain the mean maximum dry weight (11.15 mg). Furthermore, it was shown that ovipositing females, laying just one egg per leaf, tended to select large leaves providing this minimum amount of food. It is hypothesized that females probably follow straight-lined routes on their oviposition flights, rather than ovipositing on leaves chosen at random. By applying such a strategy, females can almost completely avoid competition for food among their own offspring. Furthermore, competition among the progeny of the whole population is also reduced, particularly in years when adult abundance is very low. The significance of certain factors influencing the population dynamics of Cheilosia fasciata was evaluated by applying a rank correlation analysis. It was shown that high precipitation rates in April reduced the time available for mating and oviposition resulting in low emergence abundance in the next spring. Larval survivorship was enhanced by high precipitation rates in May and June, indicating that drought may be unfavourable to larvae and reduce food availability. Predation by a parasitoid Phygadeuon ursini Horstmann, 1986 (Hymenoptera, Ichneumonidae), appears to be just an imperfect (Milne 1984) density-dependent control mechanism; in fact, it was shown that food limitation is the only significant mechanism of density-dependent population control.     

Molecular evidence for a species complex in the patagonian lizard Liolaemus bibronii and phylogeography of the closely related Liolaemus gracilis (Squamata: Liolaemini)

The lizard genus Liolaemus is endemic to temperate South America and includes 190 species. Liolaemus bibronii has a large geographic distribution and inhabits a great diversity of habitats, including the Monte, Steppe, and high Andean grassland environments. Liolaemus gracilis has a similar body size and shape to L. bibronii; the two are parapatrically distributed, and L. gracilis is also widely distributed. Here we use the mtDNA cytb sequence data of these two species to investigate lizard phylogeographic patterns in southern South America. L. bibronii is paraphyletic with respect to L. gracilis, Liolaemus ramirezae, Liolaemus robertmertensi and Liolaemus saxatilis; it is composed of many genetically different allopatric haploclades, some of which are reciprocally monophyletic. We also found evidence for introgression between L. bibronii and L. gracilis in the same area that introgression was hypothesized in the Liolaemus darwinii complex. We discuss the distribution of the major haploclades with inferences of their population histories, the concordance of these clades' distributions and histories with other lizard complexes studied with the same markers and methods, and taxonomic implications of these results.     

Molecular and immunochemical demonstration of a novel member of Bf/C2 homolog in amphioxus Branchiostoma belcheri: implications for involvement of hepatic cecum in acute phase response

A complement system operating via the alternative pathway (AP) similar to that of vertebrates has been demonstrated in the primitive chordate amphioxus. However, the factor B (Bf), a key specific protease in the AP, remains elusive in amphioxus to date. We demonstrate in this study the presence of a factor B-like protein in amphioxus Branchiostoma belcheri by both immunoblotting and molecular cloning. The factor B-like protein was immunohistochemically localized in the hepatic cecum. The B. belcheri factor B-like gene, BbBf/C2, encoded a mosaic protein with three complement control protein (CCP) domains, a von Willebrand factor A (vWFA) domain and a serine protease (SP) domain. Peculiarly, BbBf/C2 had an epidermal growth factor-like domain (EGF_CA) located between CCP1 and CCP2, therefore BbBf/C2 had a modular structure of CCP-EGF_CA-CCP-CCP-vWFA-SP, making it a novel member of Bf/C2 family proteins. Real-time PCR assay revealed that lipopolysaccharide (LPS) challenge resulted in a quick and continuously significant up-regulation of BbBf/C2 expression in the hepatic cecum, while BbBf/C2 was only expressed for a short time in the hind-gut following LPS challenge though the expression level was temporarily higher than that in the hepatic cecum. Similarly, immuno-dot blotting showed that challenge with LPS triggered a significant elevation of BbBf/C2 synthesis in the hepatic cecum and hind-gut, with a higher rise in the former tissue. These results indicate that both hepatic cecum and hind-gut may be involved in the immune response induced by LPS, but the hepatic cecum, like the vertebrate liver, is the primary tissue synthesizing BbBf/C2 in response to LPS challenge, thereby playing a major role in the acute phase response.