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Smaller Species (smaller + species)
Selected AbstractsNetworks and dominance hierarchies: does interspecific aggression explain flower partitioning among stingless bees?ECOLOGICAL ENTOMOLOGY, Issue 2 2010KAI DWORSCHAK 1. The distribution of consumers among resources (trophic interaction network) may be shaped by asymmetric competition. Dominance hierarchy models predict that asymmetric interference competition leads to a domination of high quality resources by hierarchically superior species. 2. In order to determine the competitive dominance hierarchy and its effect on flower partitioning in a local stingless bee community in Borneo, interspecific aggressions were tested among eight species in arena experiments. 3. All species tested were strongly mutually aggressive in the arena, and the observed interactions were often lethal for one or both opponents. Aggression significantly increased with body size differences between fighting pairs and was asymmetric: larger aggressors were superior over smaller species. Additional aggression tests involved dummies with surface extracts, and results suggest that species- and colony-specific surface profiles are important in triggering the aggressive behaviour. 4. Sixteen stingless bee species were observed foraging on 41 species of flowering plants. The resulting bee,flower interaction network showed a high degree of generalisation (network-level specialisation H2' = 0.11), corresponding to a random, opportunistic distribution of bee species among available flower species. 5. Aggressions on flowers were rare and only occurred at a low level. The dominance hierarchy obtained in the arena experiments did not correlate significantly with plant quality, estimated as the number of flowers per plant or as total bee visitation rate. 6. Our findings suggest that asymmetries in interference competition do not necessarily translate into actual resource partitioning in the context of complex interacting communities. [source] Body size and invasion success in marine bivalvesECOLOGY LETTERS, Issue 2 2002Kaustuv Roy The role of body size in marine bivalve invasions has been the subject of debate. Roy et al. found that large-bodied species of marine bivalves were more likely to be successful invaders, consistent with patterns seen during Pleistocene climatic change, but Miller et al. argued that such selectivity was largely driven by the inclusion of mariculture species in the analysis and that size-selectivity was absent outside of mariculture introductions. Here we use data on non-mariculture species from the north-eastern Pacific coast and from a global species pool to test the original hypothesis of Roy et al. that range limits of larger bivalves are more fluid than those of smaller species. First, we test the hypothesis that larger bivalve species are more successful than small species in expanding their geographical ranges following introduction into new regions. Second, we compare body sizes of indigenous and non-indigenous species for 299 of the 303 known intertidal and shelf species within the marine bivalve clade that contains the greater number of non-mariculture invaders, the Mytilidae. The results from both tests provide additional support for the view that body size plays an important role in mediating invasion success in marine bivalves, in contrast to Miller et al. Thus range expansions in Recent bivalves are consistent with patterns seen in Pleistocene faunas despite the many differences in the mechanisms. [source] Long-term responses of zooplankton to invasion by a planktivorous fish in a subarctic watercourseFRESHWATER BIOLOGY, Issue 1 2009PER-ARNE AMUNDSEN Summary 1.,Introduced or invading predators may have strong impacts on prey populations of the recipient community mediated by direct and indirect interactions. The long-term progression of predation effects, covering the invasion and establishment phase of alien predators, however, has rarely been documented. 2.,This paper documents the impact of an invasive, specialized planktivorous fish on its prey in a subarctic watercourse. Potential predation effects on the crustacean plankton, at the community, population and individual levels, were explored in a long-term study following the invasion by vendace (Coregonus albula). 3.,Over the 12-year period, the density and species richness of zooplankton decreased, smaller species became more abundant and Daphnia longispina, one of the largest cladocerans, was eliminated from the zooplankton community. 4.,Within the dominant cladocerans, including Daphnia spp., Bosmina longispina and Bosmina longirostris, the body size of ovigerous females and the size at first reproduction decreased after the arrival of the new predator. The clutch sizes of Daphnia spp. and B. longirostris also increased. 5.,Increased predation pressure following the vendace invasion induced many effects on the crustacean zooplankton, and we document comprehensive and strong direct and indirect long-term impacts of an introduced non-native predator on the native prey community. [source] Time budgets of Snow Geese Chen caerulescens and Ross's Geese Chen rossii in mixed flocks: implications of body size, ambient temperature and family associationsIBIS, Issue 1 2009JÓN EINAR JÓNSSON Body size affects foraging and forage intake rates directly via energetic processes and indirectly through interactions with social status and social behaviour. Ambient temperature has a relatively greater effect on the energetics of smaller species, which also generally are more vulnerable to predator attacks than are larger species. We examined variability in an index of intake rates and an index of alertness in Lesser Snow Geese Chen caerulescens caerulescens and Ross's Geese Chen rossii wintering in southwest Louisiana. Specifically we examined variation in these response variables that could be attributed to species, age, family size and ambient temperature. We hypothesized that the smaller Ross's Geese would spend relatively more time feeding, exhibit relatively higher peck rates, spend more time alert or raise their heads up from feeding more frequently, and would respond to declining temperatures by increasing their proportion of time spent feeding. As predicted, we found that Ross's Geese spent more time feeding than did Snow Geese and had slightly higher peck rates than Snow Geese in one of two winters. Ross's Geese spent more time alert than did Snow Geese in one winter, but alert rates differed by family size, independent of species, in contrast to our prediction. In one winter, time spent foraging and walking was inversely related to average daily temperature, but both varied independently of species. Effects of age and family size on time budgets were generally independent of species and in accordance with previous studies. We conclude that body size is a key variable influencing time spent feeding in Ross's Geese, which may require a high time spent feeding at the expense of other activities. [source] Multiple-brooding in birds of prey: South African Black Sparrowhawks Accipiter melanoleucus extend the boundariesIBIS, Issue 1 2005ODETTE CURTIS Multiple-brooding (raising more than one brood of young in quick succession) occurs infrequently in raptors and is generally restricted to either smaller species with shorter nesting periods, co-operative breeders or species capable of capitalizing on conditions of prolonged food abundance whenever they occur. This paper presents the first recorded cases of multiple-brooding in the Black Sparrowhawk Accipiter melanoleucus from two distinct locales in South Africa. In the Western Cape (Cape Peninsula), four attempts to multiple-brood were recorded in four different years, involving three distinct pairs of birds, and in KwaZulu,Natal (Eshowe), three distinct pairs of Sparrowhawks successfully multiple-brooded on several occasions over a 5-year study period. These results establish the Black Sparrowhawk as one of only two relatively large, monogamous raptor species, and the only specialist bird-eating raptor, in which multiple-brooding has been recorded with any frequency. The species' capacity to thrive in human-modified environments (i.e. alien plantations) and particularly to exploit associated foraging opportunities (e.g. high densities of doves and pigeons in suburban areas) may, at least partly, account for the instances of multiple-brooding reported here. We suggest that biologists be more vigilant for cases of multiple-brooding in raptors, as it is possible that this trait is more common than originally thought and has previously been overlooked. [source] Effects of marine reserve age on fish populations: a global meta-analysisJOURNAL OF APPLIED ECOLOGY, Issue 4 2009Philip P. Molloy Summary 1. ,Marine reserves are widely used for conservation and fisheries management. However, there is debate surrounding the speed of population recovery inside reserves and how recovery differs among species. Here, we determine how reserve effectiveness in enhancing fish density changes with reserve age. We also examine how the effects of protection vary between fished and non-fished species and among species of different body sizes, which we use as a proxy for life history and ecology. 2. ,We meta-analysed over 1000 ratios of fish densities (inside : outside reserves) taken from reserves of 1,26 years old from around the world. 3. ,Overall, older reserves were more effective than younger reserves, with fish densities increasing within reserves by ,5% per annum relative to unprotected areas. Reserves older than 15 years consistently harboured more fish compared with unprotected areas; younger reserves were less reliably effective. 4. ,Large, fished species responded strongly and positively to protection in old (>15 years) and, unexpectedly, in new and young (,10 years) reserves. Small, fished species and non-fished species of all sizes showed weaker responses to protection that did not vary predictably with reserve age. 5. ,We expected large fish to respond more slowly to protection than smaller species. We also expected small species to decline after large fish had recovered (i.e. trophic cascades). Neither prediction was supported. 6. , Synthesis and applications. Our meta-analyses demonstrate that, globally, old reserves are more effective than young reserves at increasing fish densities. Our results imply that reserves should be maintained for up to 15 years following establishment, even if they initially appear ineffective. If protection is maintained for long enough, fish densities within reserves will recover and such benefits will be particularly pronounced for large, locally fished species. [source] The role of water abundance, thermoregulation, perceived predation risk and interference competition in water access by African herbivoresAFRICAN JOURNAL OF ECOLOGY, Issue 3 2008Marion Valeix Abstract In African savannas, surface water can become limiting and an understanding of how animals address the trade-offs between different constraints to access this resource is needed. Here, we describe water access by ten African herbivore species in Hwange National Park, Zimbabwe, and we explore four possible determinants of the observed behaviours: water abundance, thermoregulation, perceived predation risk and interference competition. On average, herbivores were observed to drink in 80% of visits to a waterhole. The probability of drinking was higher in 2003 (474 mm) than in 2004 (770 mm), and at the end of the dry season than at its beginning. For larger species, this probability may also be related to risks of interference competition with elephants or other herbivores. For smaller species, this probability may also be related to the perceived risk of predation. We also investigate the time spent accessing water to drink. The influence of herd size and the presence of young on the time spent accessing water for most species suggests that perceived predation risk plays a role. Thermoregulation also affects this time: during the hottest periods, herbivores spend less time in open areas, unless when wind is strong, probably owing to evapotranspired heat loss. Résumé Dans les savanes africaines, l'eau de surface disponible peut devenir un facteur limitant et il est nécessaire de comprendre comment les animaux agissent face aux différentes contraintes que pose l'accès à cette ressource. Nous décrivons ici l'accès à l'eau de dix herbivores africains du Parc National de Hwange, au Zimbabwe, et nous explorons quatre facteurs qui sont peut-être déterminants dans les comportements observés: l'abondance de l'eau, la thermorégulation, le risque de prédation ressenti et la compétition/ interférence. En moyenne, on a observé que les herbivores buvaient lors de 80% de leurs visites au point d'eau. La probabilité qu'ils boivent étai plus forte en 2003 (474 mm) qu'en 2004 (770 mm), et à la fin de la saison sèche qu'au début. Pour les plus grandes espèces, cette probabilité pourrait aussi être liée aux risques de compétition par interférence avec les éléphants ou d'autres herbivores. Pour les plus petites espèces, cette probabilité pourrait aussi être liée au risque de prédation ressenti. Nous avons aussi étudié le temps passéà se rendre au point d'eau pour y boire. L'influence de la taille du groupe et de la présence de jeunes sur le temps pris par la plupart des espèces pour se rendre au point d'eau laisse penser que la perception du risque de prédation joue un rôle. La thermorégulation affecte aussi cette durée: pendant les périodes les plus chaudes, les herbivores passent moins de temps dans les espaces ouverts, sauf si le vent est fort, probablement à cause de la perte de chaleur par évapotranspiration. [source] Mix and match , hybridization reveals hidden complexity in seal breeding behaviourMOLECULAR ECOLOGY, Issue 15 2007WILLIAM AMOS Not so long ago, mammalian breeding systems were seen as dominated by males fighting each other for the right to mate with passive females. Genetic parentage analysis has been instrumental in changing this view and exposing the key role of female choice. Some of the most interesting discoveries have emerged from work on seals, where extreme polygyny is common but females often seem to have a bigger say than was previously thought. A remarkable case in question involves Macquarie Island, where three species of fur seal recently formed a mixed breeding colony (Goldsworthy et al. 1999). Here, the true colours of both sexes lie unusually exposed, because classical models predict that males of the biggest species will dominate the beach and force females of smaller species to conceive mainly hybrid pups. In a fascinating paper in this issue of Molecular Ecology, Lancaster and colleagues (Lancaster et al. 2007) show that females are not this naïve. Although happy to gain protection for most of the season by sitting in the territory of one of the largest males, regardless of whether he is the same species, females almost always conceive to one of their own kind. The females do this, not because any hybrid male offspring they conceive will be sickly and fail to hold good territories, but because females who pup in their hybrid son's territories will be disproportionately likely to mate elsewhere. Hybrid males seem physically fit but sexually unattractive! [source] Is the productivity of vegetation plots higher or lower when there are more species?OIKOS, Issue 2 2003Variable predictions from interaction of the, competitive dominance effect' on the habitat templet, sampling effect' Using a habitat templet model, we predict that the productivity (total biomass) of plots within a plant community may be positively, negatively or not at all related to variation in the number of species per plot, depending on successional stage (time since major disturbance) and habitat carrying capacity (reflecting the total resource supplying power of the habitat). For plots of a given size, a positive relationship between productivity and species richness is predicted in recently disturbed habitats because local neighbourhoods here will have been assembled largely stochastically, usually from a pool of available species with a right-skewed size frequency distribution. Hence, in the earliest stages of succession, plots will have relatively high total biomass only if they contain at least some of the relatively uncommon larger species which will, in turn, be more likely in those neighbourhoods that contain more species (the sampling effect). Among these will also be some of the more common smaller species; hence, these high biomass, species-rich plots should have relatively low species evenness, in contrast to what is predicted under effects involving species complementarity. In late succession, the plots with high total biomass will still be those that contain relatively large species but these plots will now contain relatively few species owing to increased competitive exclusion over time (the competitive dominance effect). In intermediate stages of succession, no relationship between plot productivity and species richness is predicted because the opposing sampling and competitive dominance effects cancel each other out. We predict that the intensity of both the sampling and competitive dominance effects on the productivity/species richness relationship will decrease with decreasing habitat carrying capacity (e.g. decreasing substrate fertility) owing to the inherently lower variance in between-plot productivity that is predicted for more resource-impoverished habitats. [source] Body size and joint posture in primatesAMERICAN JOURNAL OF PHYSICAL ANTHROPOLOGY, Issue 2 2009John D. Polk Abstract Body mass has been shown in experimental and comparative morphological studies to have a significant effect on joint posture in major limb joints. The generalizability of experimental studies is limited by their use of small sample sizes and limited size ranges. In contrast, while comparative morphological studies often have increased sample sizes, the connection between joint posture and morphological variables is often indirect. The current study infers joint postures for a large sample of primates using an experimentally validated method, and tests whether larger primates use more extended joint postures than smaller species. Postures are inferred through the analysis of patterns of subchondral bone apparent density on the medial femoral condyle. Femora from 94 adult wild-shot individuals of 28 species were included. Apparent density measurements were obtained from CT scans using AMIRA software, and the angular position of the anterior-most extent of the region of maximum apparent density on the medial femoral condyle was recorded. In general, the hypothesis that larger-bodied primates use more extended knee posture was supported, but it should be noted that considerable variation exists, particularly at small body sizes. This indicates that smaller species are less constrained by their body size, and their patterns of apparent density are consistent with a wide range of knee postures. The size-related increase in inferred joint posture was observed in most major groups of primates, and this observation attests to the generalizability of Biewener's model that relates body size and joint posture. Am J Phys Anthropol, 2009. © 2009 Wiley-Liss, Inc. [source] Allometry of facial mobility in anthropoid primates: Implications for the evolution of facial expressionAMERICAN JOURNAL OF PHYSICAL ANTHROPOLOGY, Issue 1 2009Seth D. Dobson Abstract Body size may be an important factor influencing the evolution of facial expression in anthropoid primates due to allometric constraints on the perception of facial movements. Given this hypothesis, I tested the prediction that observed facial mobility is positively correlated with body size in a comparative sample of nonhuman anthropoids. Facial mobility, or the variety of facial movements a species can produce, was estimated using a novel application of the Facial Action Coding System (FACS). I used FACS to estimate facial mobility in 12 nonhuman anthropoid species, based on video recordings of facial activity in zoo animals. Body mass data were taken from the literature. I used phylogenetic generalized least squares (PGLS) to perform a multiple regression analysis with facial mobility as the dependent variable and two independent variables: log body mass and dummy-coded infraorder. Together, body mass and infraorder explain 92% of the variance in facial mobility. However, the partial effect of body mass is much stronger than for infraorder. The results of my study suggest that allometry is an important constraint on the evolution of facial mobility, which may limit the complexity of facial expression in smaller species. More work is needed to clarify the perceptual bases of this allometric pattern. Am J Phys Anthropol, 2009. © 2008 Wiley-Liss, Inc. [source] Scaling of the first ethmoturbinal in nocturnal strepsirrhines: Olfactory and respiratory surfacesTHE ANATOMICAL RECORD : ADVANCES IN INTEGRATIVE ANATOMY AND EVOLUTIONARY BIOLOGY, Issue 3 2007Timothy D. Smith Abstract Turbinals (scroll bones, turbinates) are projections from the lateral wall of the nasal fossa. These bones vary from simple folds to branching scrolls. Conventionally, maxilloturbinals comprise the respiratory turbinals, whereas nasoturbinals and ethmoturbinals comprise olfactory turbinals, denoting the primary type of mucosa that lines these conchae. However, the first ethmoturbinal (ETI) appears exceptional in the variability of it mucosal covering. Recently, it was suggested that the distribution of respiratory versus olfactory mucosae varies based on body size or age in strepsirrhine primates (lemurs and lorises). The present study was undertaken to determine how the rostrocaudal distribution of olfactory epithelium (OE) versus non-OE scales relative to palatal length in strepsirrhines. Serially sectioned heads of 20 strepsirrhines (10 neonates, 10 adults) were examined for presence of OE on ETI, rostral to its attachment to the nasal fossa wall (lateral root). Based on known distances between sections of ETI, the rostrocaudal length of OE was measured and compared to the length lined solely by non-OE (primarily respiratory epithelium). In 13 specimens, the total surface area of OE versus non-OE was calculated. Results show that the length of non-OE scales nearly isometrically with cranial length, while OE is more negatively allometric. In surface area, a lesser percentage of non-OE exists in smaller species than larger species and between neonates and adults. Such results are consistent with recent suggestions that the olfactory structures do not scale closely with body size, whereas respiratory structures (e.g., maxilloturbinals) may scale close to isometry. In primates and perhaps other mammals, variation in ETI morphology may reflect dual adaptations for olfaction and endothermy. Anat Rec, 2007. © 2007 Wiley-Liss, Inc. [source] Comparative spermatogenesis, spermatocytogenesis, and spermatozeugmata formation in males of viviparous species of clinid fishes (Teleostei: Clinidae, Blennioidei)THE ANATOMICAL RECORD : ADVANCES IN INTEGRATIVE ANATOMY AND EVOLUTIONARY BIOLOGY, Issue 3 2007Lev Fishelson Abstract Spermatogenesis and spermatocytogenesis in 16 species of viviparous clinid fishes (Clinidae, Blennioidei) from various localities were followed for the first time by means of light and electron microscopy. The testes of the studied species are of the lobular type, with germinal stem cells situated at the apical ends of the lobules and a vas efferens along the internal margin. Maturation of the spermatides takes place in spermatocysts formed by Sertoli cells around the B-spermatogonia. The gradual condensation and relocation of the chromosomes along the nuclei membranes are highly prominent in this process, which can be divided into several stages. Anisodiametric and slightly flattened sperm heads are eventually formed, 0.4,0.5 ,m in diameter and 7.5 ± 1 ,m long, bearing 80 ± 15 ,m long flagella. The sperms are packed into spermatozeugmata within the spermatocysts, enveloped and penetrated by the mucotic material of the Sertoli cells. With division of the germ cells and maturation of the spermatids, the spermatocyst dimensions increase, attaining 40 ± 8 ,m in diameter in the smaller species of Heteroclinus, and up to 90 ± 10 ,m in the larger males of Clinus superciliosus and C. cottoides. Accordingly, the volume of the maturing spermatocysts attains ca. 1,300 ± 100 ,m3 in the smaller species, and ca. 6,500 ± 300 ,m3 in the larger ones. As sperm head volume is ca. 2.24 ,m3, the number of sperm in the smallest mature spermatocysts reaches ca. 440 and in the largest over 2,900. Upon release from the cysts, the spermatozeugmata are transported along the sperm ducts to the posterior ampullae where they are stored in the epididymis. During copulation, the sperms are transported from there to the female via the intromittent organ. The sperm formation parameters and their structure and numbers are discussed. Anat Rec Part A, 2007. © 2007 Wiley-Liss, Inc. [source] Growth, filtration and ingestion rate of the rotifer Brachionus plicatilis fed with large (Asteromonas gracilis) and small (Chlorella sp.) celled algal speciesAQUACULTURE RESEARCH, Issue 10 2003George N. Hotos Abstract The rotifer Brachionus plicatilis was fed in experimental conditions with a small celled (2,5 ,m) Chlorella sp. and a large celled (16,22 ,m) Asteromonas gracilis algae. The specific growth rate (SGR) of rotifers fed Asteromonas (maximum 0.79) was statistically higher than that for rotifers fed Chlorella (maximium 0.61). The filtration and ingestion rates using different rotifer and algal densities exhibited certain maxima depending on the species, the cell density and the condition of the rotifers. The filtration rate was higher with Asteromonas and, although ingestion rate was lower than with Chlorella, the ingestion in terms of cell volume was 10-fold higher. It seems that B. plicatilis ingests the larger cell diameter algal species more efficiently than the smaller species that is usually used for its mass culture. [source] | ||||||||||