Morphology and microhabitat preferences of benthic foraminifera from the northwest Atlantic Ocean

The distribution of Rose Bengal stained calcareous benthic foraminifera was determined in six ☐ cores raised from water depths between 200 and 3000 m on the Nova Scotian continental margin and Gulf of Maine. The taxa can be separated into four microhabitats within the surficial sediments. Epifaunal taxa are generally found in the top cm, intermediate infaunal taxa are found from about 1 to 4 cm and deep infaunal taxa are found at > 4 cm sediment depth in at least one ☐ core. A fourth group, shallow infaunal taxa, is found in the top 2 cm and is inferred to be infaunal based on wall porosity characteristics and test shapes similar to infaunal taxa. The epifaunal, shallow infaunal and intermediate infaunal taxa maintain their positions within the sediments from core to core, whereas the deep infaunal taxa are found at progressively shallower sediment depths in cores within increasing organic carbon contents from shallower water depths.Each microhabitat category has distinct morphological characteristics. Epifaunal taxa have plano-covex or biconvex cross sections, trochospiral coiling and large pores absent or found on only one side. Shallow infaunal taxa have uniserial, triserial, or planispiral coiling, with surface ornamentation present on a number of taxa. The intermediate infaunal taxa have rounded peripheries, pores over the entire test and planispiral coiling, with the exception ofCibicidoides bradyi which has trochospiral coiling. The deep infaunal taxa have, in general, planispiral or triserial coiling with cylindrical or ovate shaped tests.     

The development of foraging microhabitat preferences in meerkats

Animals of many species tend to target their foraging attemptstoward particular microhabitats within their habitat. Althoughthese preferences are critical determinants of the foragingniche and have important ecological and evolutionary implications,we know little about how they develop. Here, we use detailedlongitudinal data from meerkats (Suricata suricatta) to examinehow individual learning and the use of social information affectthe development of foraging microhabitat preferences. Despiteliving in an open, arid environment, adult meerkats frequentlyforaged at the base of vegetation. Young pups seldom did so,but their foraging microhabitat choices became increasinglyadult-like as they grew older. Learning about profitable microhabitatsmay have been promoted in part by positive reinforcement fromprey capture. Foraging may also have become increasingly targetedtoward suitable locations as pups grew older because they spentmore time searching before embarking on foraging bouts. Thedevelopment of microhabitat preferences might also have beeninfluenced by social cues. Foraging in close proximity to adultsmay increase the probability that pups would dig in similarmicrohabitats. Also, pups often dug in holes created by olderindividuals, whereas adults never dug in existing holes. Foragingin existing holes was no more profitable to pups than creatingtheir own foraging hole but could provide pups with importantinformational benefits. The integration of personal and socialinformation is likely to be a common feature in the developmentof the foraging niche in generalist species.     

Habitat preferences of sub-montane spiders in northem England

Thirteen study sites were selected to cover the dominant vegetation types on the plateaux of three summits in the North Pennines, England The spider community of these sites were sampled by pitfall trapping between April and October 1991 Several environmental variables were collected for each site, including local topography, soil characteristics and vegetation structure Multivariate methods were used to classify the sites based on their spider species composition Canonical correspondence analysis was used to assess the influence of the external factors on the distribution of the species The results suggest that vegetation density is the major factor influencing spider distribution on the summit plateaux with slope and soil depth also contributing to the variation Three spider associations for the plateaux are proposed based on their common species composition Two short Festuca grassland assemblages and a Nardus/ Ertophorum spp assemblage associated with higher vegetation density The habitat preferences of some species common to the plateaux are discussed in light of the results, and compatisons are made with studies from other upland areas     

Vertical stratification of the termite assemblage in a neotropical rainforest

The importance of termites as decomposers in tropical forests has long been recognized. Studies on the richness and diversity of termite species and their ecological function have flourished in more recent times, but these have been mostly conducted in a thin stratum within a standing man’s reach. Our aims were to evaluate the specific richness and composition of the termite assemblage in the canopy of a tropical rainforest and to determine its originality with respect to the sympatric ground-level fauna. We conducted systematic searches for canopy termites, together with conventional sampling of the sympatric ground-level fauna, in the San Lorenzo forest, Panama. We hypothesized that (1) the canopy accommodates two categories of wood-feeding termites (long-distance foragers and small-colony “one-piece” species) and possibly soil-feeders in suspended soil-like habitats; (2) due to the abundance of soil-feeders, the overall diversity of the ground fauna is higher than that of the canopy; (3) differences in microclimate and resource accessibility favour vertical stratification among wood-feeders. Sixty-three canopy samples yielded ten species of termites, all wood-feeders. Five of these were not found at ground level, although a total of 243 ground samples were collected, representing 29 species. In addition to long-distance foragers (Microcerotermes and Nasutitermes spp.) and small-colony termites (mostly Kalotermitidae), the canopy fauna included Termes hispaniolae, a wood-feeding Termitidae from an allegedly soil-feeding genus, living in large dead branches. Soil-feeders were absent from the canopy, probably because large epiphytes were scarce. As predicted, the ground fauna was much richer than that of the canopy, but the species richness of both habitats was similar when only wood-feeders were considered. Vertical stratification was strongly marked among wood-feeders, as all common species, apart from the arboreal-nesting Microcerotermes arboreus, could unequivocally be assigned to either a ground or a canopy group. The canopy, therefore, contributes significantly to the total species richness of the termite assemblage, and the diversity, abundance and ecological importance of canopy termites in tropical rainforests may be higher than previously recognized.Electronic Supplementary Material Supplementary material is available to authorized users in the online version of this article at .     

The reproductive flight phenology of a neotropical ant assemblage

1. Alate flights reflect an ant colony's investment in sexual reproduction and dispersal yet little is known about community‐wide patterns of alate phenology. Two Malaise traps (for 2 years) and two light traps (for 1 year) were used to explore the flight phenologies of 22 common neotropical species from Barro Colorado Island, Panama. 2. The traps caught 23 182 individuals and 286 species/morphospecies. The two trap methods shared only 18 species. Samples also differed in sexual composition: light trap samples were 80% female, Malaise trap samples were 2.6% female. 3. Of 22 common species, all but one flew over half the year, with about half flying every month of the year. These data, combined with a literature review, suggest a latitudinal gradient in alate flight season: one north temperate assemblage (42°N) averaged 1.6 lunar months per species. The ever‐warm tropical year provides a larger flight window that allows a diversity of phenologies, from continuous to strongly pulsed. 4. Rainfall was correlated with alate flights in one‐third of the species. Quantile regression suggested that high weekly rainfall was necessary but not sufficient to produce alate flights in about a quarter of the species. 5. By decreasing the number of nests releasing alates on a given day, long flight seasons may lower the probability of finding a mate. At the same time, long flight seasons may increase the opportunity of finding vacant nest sites. High population densities and high incidence of nest disturbance in this community may ameliorate the first cost while enhancing the second benefit.     

Diet preference reflects the ontogenetic shift in microhabitat use in Lipophrys pholis

Based on the heterogenous nature of Lipophrys pholis diet, the stage of the species' ontogenetic development when major niche shifts occurred was identified, and the causes that force this blennid to change its feeding behaviour, vertical distribution and shelter occupation were considered. The diet analysis of the different size classes consistently showed two clusters, grouping individuals < or >8 cm total length. This shift occurred simultaneously with the onset of reproduction; it seemed to be independent of inter‐ and intraspecific competition and reflected a quantitative and qualitative alteration of the dietary constituents. The analysis of the diet of other sympatric intertidal blennids, Lipophrys trigloides and Coryphoblennius galerita , showed that, apart from the first developmental stages, there seemed to be no important dietary overlap. The inevitability of this niche alteration could be explained by the combination of at least two different factors: the development of the scraping capability that enabled the fish to feed on large benthic prey, together with the limited number of suitable shelters that were available in rock pools.     

Morphological traits as predictors of diet and microhabitat use in a diverse beetle assemblage

We explored how morphological traits can complement phylogenetic information to extend our predictions of the ecology of a diverse beetle assemblage. We analysed ten morphological traits from an assemblage of 239 species from 35 families, and identified three axes of morphological variation that were independent of body length: (1) relative robustness; (2) relative appendage length; and (3) relative abdomen length. The trait associations defining these axes of morphological variation did not change after adjusting for family‐level phylogeny. We detected significant differences in morphological variation across the beetle assemblage according to diet and microhabitat use, and these patterns were only partially influenced by family membership. Further analysis within dominant families showed that species of Carabidae, Curculionidae, Scarabaeidae and Staphylinidae had greater body length in open versus tree litter microhabitat, and species of Carabidae and Curculionidae had greater relative robustness, but shorter relative appendage length, in open versus tree litter microhabitat. Although it is clear that family‐level phylogeny and morphology share some explanatory power for predicting the diet and microhabitat use by beetles, we demonstrate that body length, robustness and appendage length are correlated significantly with microhabitat use when comparing members of the same family. © 2011 The Linnean Society of London, Biological Journal of the Linnean Society, 2011, 102 , 301–310.     

Biogeographic position and body size jointly set lower thermal limits of wandering spiders

Most species encounter large variations in abiotic conditions along their distribution range. The physiological responses of most terrestrial ectotherms (such as insects and spiders) to clinal gradients of climate, and in particular gradients of temperature, can be the product of both phenotypic plasticity and local adaptation. This study aimed to determine how the biogeographic position of populations and the body size of individuals set the limits of cold (freezing) resistance of Dolomedes fimbriatus. We compared D. fimbriatus to its sister species Dolomedes plantarius under harsher climatic conditions in their distribution range. Using an ad hoc design, we sampled individuals from four populations of Dolomedes fimbriatus originating from contrasting climatic areas (temperate and continental climate) and one population of the sister species D. plantarius from continental climate, and compared their supercooling ability as an indicator of cold resistance. Results for D. fimbriatus indicated that spiders from northern (continental) populations had higher cold resistance than spiders from southern (temperate) populations. Larger spiders had a lower supercooling ability in northern populations. The red‐listed and rarest D. plantarius was slightly less cold tolerant than the more common D. fimbriatus, and this might be of importance in a context of climate change that could imply colder overwintering habitats in the north due to reduced snow cover protection. The lowest cold resistance might put D. plantarius at risk of extinction in the future, and this should be considered in conservation plan.     

Effects of microhabitat preferences on kelp gull Larus dominicanus breeding performance

We examined microhabitat preferences and their adaptiveness for the kelp gull Larus dominicanus in one of its largest colonies in Patagonia. We quantified 13 habitat variables at 104 and 92 nest-sites and at 70 and 60 random points in 1998 and 1999, respectively. We recorded egg laying dates, hatching success, number of chicks fledged and breeding success at 92 of these nests in each of the study seasons. Compared to random points, nest sites had more vegetation cover and were closer to the nearest available bush, but they were located further from the nearest clearing for flight take-off, all variables included in the "vegetation" principal component. Nests were built on substrates with lower slopes and higher percentages of silt-clay, but with lower percentages of rock. In both years, hatching success, number of chicks fledged and breeding success were related positively to the vegetation principal component. Substrate slope and composition contributed to explain the variation in hatching and breeding success in 1998 and 1999, respectively. Our study shows that some kelp gull breeding parameters are affected by nest-site habitat characteristics. These associations were in most cases influenced by the timing of breeding, with earlier breeders being more successful. Vegetation effects and substrate characteristics were important variables in distinguishing random sites from nest sites, and in explaining variation in breeding performance, showing that their habitat preferences are adaptive and allowing us to detect both the pattern and process in kelp gull habitat selection.     

Teratocytes growth pattern reflects host suitability in a host–parasitoid assemblage

Abstract.  In some parasitoid species, the serosa membrane breaks apart at hatching and produces teratocyte cells that assume various functions (immunossupression, secretion and nutrition) mediating host–parasitoid relationships. Teratocyte growth pattern may thus reflect the host suitability for a parasitoid. The teratocyte growth pattern (increase in size and number of teratocytes as a function of time) is studied and used as an indirect measure of fitness to compare the development of the endoparasitoid Dinocampus coccinellae in a marginal host, the coccinellid Harmonia axyridis , and in a suitable host, Coleomegilla maculata . Indirect measures of fitness recorded in both host species confirm that C. maculata is a suitable host for D. coccinellae contrary to the marginal host H. axyridis. According to regression analysis, teratocyte numbers decrease linearly whereas teratocyte size increases linearly with time in the suitable host C. maculata (larvae or adults). In the marginal host, parasitism occurs only in the larval stage where a delay in the parasitoid larval development is observed. Increase in teratocyte size is also highly variable. The teratocyte growth pattern of the parasitoid in the marginal host does not follow the linear model found in the suitable host. Teratocyte growth pattern may be a useful criterion to evaluate host-suitability and host range of parasitoids.     

Tests of aggregative preferences of wandering salamanders (Aneides vagrans)

Plethodontid salamanders usually exhibit territorial spacing patterns and behaviors. Previous works suggest that plethodontids from Vancouver Island, Canada lack strong territoriality. In one Vancouver Island species, Aneides vagrans, salamanders may even be found in the field in small aggregations. We investigated preferences of A. vagrans for occupied vs unoccupied cover objects and for cover objects occupied by conspecifics of different age/size classes. We also tested A. vagrans preferences for conspecific vs heterospecific salamanders in an attempt to determine if the lack of territoriality by A. vagrans is species-specific and perhaps related to habitat segregation. A. vagrans did not avoid occupied cover objects or exhibit a preference for occupied vs unoccupied sites. Age class did not affect cover object choice. A. vagrans did not avoid heterospecifics that exhibit the highest degree of resource overlap (Plethodon vehiculum), which we believe might be attributable to a benign and resource-rich habitat, although alternative explanations exist. A. vagrans did avoid syntopic newts (Taricha granulosa), though this is probably due to toxic newt skin secretions.     

The significance of predation in nest site selection of turtles: an experimental consideration of macro- and microhabitat preferences

Conceptual models predict counteractive effects of herbivores and nutrient enrichment on plant diversity and reversed effects of grazers under different nutrient regimes. I tested these hypotheses in 11 field experiments with periphyton communities in three different aquatic habitats (a highly eutrophic lake, an meso-eutrophic lake, and an meso-eutrophic part of the Baltic Sea coast) and in different seasons. Grazer access and nutrient supply were manipulated in a factorial design. Species richness and evenness were chosen as response variables. Both manipulated factors had significant and contrasting effects on diversity, with variable effect strength between sites and seasons. From the two aspects of diversity, evenness well reflected the changes in community composition. Fertilization tended to increase the dominance of few species and thus to decrease evenness, whereas grazers counteracted these effects by removing dominant life forms. The response of species richness was not as expected, since grazers decreased richness throughout, whereas nutrients had weaker effects but tended to increase richness. Species richness rather reflected changes in periphyton architecture. Grazers reduced algal richness presumably by co-consumption of rare species in the tightly connected periphyton assemblages, whereas enrichment may increase richness by providing more structure via increased dominance of filamentous species. Although grazer and nutrient effects on richness and evenness were opposing, there was no change in the effect of one factor by manipulation of the other.     

Feeding guild structure of beetles on Australian tropical rainforest trees reflects microhabitat resource availability

1.?We tested the hypotheses that feeding guild structure of beetle assemblages changed with different arboreal microhabitats and that these differences were consistent across rainforest tree species. 2.?Hand collection and beating techniques were used from the gondola of the Australian Canopy Crane to collect beetles from five microhabitats (mature leaves, flush leaves, flowers, fruit and suspended dead wood) within the rainforest canopy. A simple randomization procedure was implemented to test whether the abundances of each feeding guild on each microhabitat were different from that expected based on a null hypothesis of random distribution of individuals across microhabitats. 3.?Beetles from different feeding guilds were not randomly distributed, but congregated on those microhabitats that are likely to provide the highest concentrations of their preferred food sources. Herbivorous beetles, in particular, were over-represented on flowers and flush foliage and under-represented on mature leaves and dead wood. Proportional numbers of species within each feeding guild were remarkably uniform across tree species for each microhabitat, but proportional abundances of feeding guilds were all significantly non-uniformly distributed between host tree species, regardless of microhabitat, confirming patterns previously found for arthropods in trees in temperate and tropical forests. 4.?These results show that the canopy beetle community is partitioned into discrete assemblages between microhabitats and that this partitioning arises because of differences in feeding guild structure as a function of the diversity and the temporal and spatial availability of resources found on each microhabitat.     

Microhabitat preferences drive phylogeographic disparities in two Australian funnel web spiders

Comparative phylogeography is underpinned by the assumption that sympatrically‐distributed taxa will have experienced similar environmental histories, resulting in broadly congruent spatial structuring of phylogenetic lineages, particularly if they inhabit similar niches. However, divergent local conditions, specifically those related to microhabitat, may produce significantly divergent systematic signatures of demographic histories. In the present study, we compare the phylogenetic and population genetic spatial patterns displayed by two species of niche‐separated (but sympatrically distributed) Australian funnel web spiders (Mygalomorphae: Hexathelidae). We demonstrate that an apparently minor disparity in habitat niche has led to divergent experiences of a common environmental history in the saproxylic Hadronyche cerberea and the ground‐burrowing Atrax sutherlandi. Furthermore, we take a crucial first step in documenting the molecular systematics of a group that has traditionally suffered from a dearth of research interest. © 2011 The Linnean Society of London, Biological Journal of the Linnean Society, 2011, 104 , 805–819.     

Long‐term changes in the fish assemblage of a neotropical hydroelectric reservoir

The changes in the fish assemblage of the Capivara Reservoir, Brazil, were assessed over a 20 year period. Of 50 native fishes present in the initial samples, 27 were no longer present in the final samples, but there had been an addition of 11 invasive fishes, suggesting the occurrence of substantial shifts in fish diversity and abundance.