Ecological and Phylogenetic Correlates to Body Size in the Indriidae

I investigated ecological and phylogenetic correlates to body size variations in 10 taxa of extant Indriidae (Indri, Avahi, and Propithecus). I also tested for phylogenetic niche conservatism as a model for the evolution of indriid body size. Phylogenetic niche conservatism refers to the shared attributes that related taxa have acquired because they tend to have occupied similar niches during their evolutionary history. I collected species-specific data on body mass, climate, density, and chemical properties of food items from the literature. I used 2 phylogenies in independent contrasts methods to control for phylogenetic relationships (Indri and Propithecus as sister taxa vs. Indri basal taxa to all indriids). Multivariate models indicated that lemur density and resource quality are the strongest ecological correlates to indriid body size variations. Partitioning methods revealed that 52.4–67% of indriid body size variation is explained by phylogenetic niche conservation. Thus, indriid body size variations may be the result of stabilizing selection. Though it is possible to identify constraints on lower than average body size, there are few data on selection against larger than average body size in indriids. Large body size in subfossil lemurs further complicates identification of constraints on larger than average body size in extant indriids. Researchers using independent contrast methods to control for phylogeny should be aware that some ecology-phenotype relationships are best explained as the result of the synergistic effects of ecology and phylogeny.     

Neocortex Size Predicts Group Size in Carnivores and Some Insectivores

Neocortex size has been shown to correlate with group size in primates. Data for carnivores and insectivores are used to test the generality of this relationship. The data suggest that carnivores lie on the same grade as the primates, but that insectivores lie on a separate grade to the left of these two orders. Among the insectivores, there appears to be a distinction between the ‘advanced’ genera (which show a relationship between group size and neocortex size) and the ‘basal’ genera (which do not).     

Body Size Correlates with Fertilization Success but not Gonad Size in Grass Goby Territorial Males

In fish species with alternative male mating tactics, sperm competition typically occurs when small males that are unsuccessful in direct contests steal fertilization opportunities from large dominant males. In the grass goby Zosterisessor ophiocephalus, large territorial males defend and court females from nest sites, while small sneaker males obtain matings by sneaking into nests. Parentage assignment of 688 eggs from 8 different nests sampled in the 2003–2004 breeding season revealed a high level of sperm competition. Fertilization success of territorial males was very high but in all nests sneakers also contributed to the progeny. In territorial males, fertilization success correlated positively with male body size. Gonadal investment was explored in a sample of 126 grass gobies collected during the period 1995–1996 in the same area (61 territorial males and 65 sneakers). Correlation between body weight and testis weight was positive and significant for sneaker males, while correlation was virtually equal to zero in territorial males. That body size in territorial males is correlated with fertilization success but not gonad size suggests that males allocate much more energy into growth and relatively little into sperm production once the needed size to become territorial is attained. The increased paternity of larger territorial males might be due to a more effective defense of the nest in comparison with smaller territorial males.     

Body Size,Growth and Life Span: Implications for the Polewards Range Shift of Octopus tetricus in South-Eastern Australia

Understanding the response of any species to climate change can be challenging. However, in short-lived species the faster turnover of generations may facilitate the examination of responses associated with longer-term environmental change. Octopus tetricus, a commercially important species, has undergone a recent polewards range shift in the coastal waters of south-eastern Australia, thought to be associated with the southerly extension of the warm East Australian Current. At the cooler temperatures of a polewards distribution limit, growth of a species could be slower, potentially leading to a bigger body size and resulting in a slower population turnover, affecting population viability at the extreme of the distribution. Growth rates, body size, and life span of O. tetricus were examined at the leading edge of a polewards range shift in Tasmanian waters (40°S and 147°E) throughout 2011. Octopus tetricus had a relatively small body size and short lifespan of approximately 11 months that, despite cooler temperatures, would allow a high rate of population turnover and may facilitate the population increase necessary for successful establishment in the new extended area of the range. Temperature, food availability and gender appear to influence growth rate. Individuals that hatched during cooler and more productive conditions, but grew during warming conditions, exhibited faster growth rates and reached smaller body sizes than individuals that hatched into warmer waters but grew during cooling conditions. This study suggests that fast growth, small body size and associated rapid population turnover may facilitate the range shift of O. tetricus into Tasmanian waters.     

Visual Diet versus Associative Learning as Mechanisms of Change in Body Size Preferences

Systematic differences between populations in their preferences for body size may arise as a result of an adaptive ‘prepared learning’ mechanism, whereby cues to health or status in the local population are internalized and affect body preferences. Alternatively, differences between populations may reflect their ‘visual diet’ as a cognitive byproduct of mere exposure. Here we test the relative importance of these two explanations for variation in body preferences. Two studies were conducted where female observers were exposed to pictures of high or low BMI women which were either aspirational (healthy, attractive models in high status clothes) or non-aspirational (eating disordered patients in grey leotards), or to combinations thereof, in order to manipulate their body-weight preferences which were tested at baseline and at post–test. Overall, results showed good support for visual diet effects (seeing a string of small or large bodies resulted in a change from pre- to post-test whether the bodies were aspirational or not) and also some support for the associative learning explanation (exposure to aspirational images of overweight women induced a towards preferring larger bodies, even when accompanied by equal exposure to lower weight bodies in the non-aspirational category). Thus, both influences may act in parallel.     

Endoparasite Species Richness of Iberian Carnivores: Influences of Host Density and Range Distribution

We investigate the determinants of macroparasite species richness of Iberian carnivores. For this, we used the parasitological data collected on 14 species of carnivores over a 10-year period. These previously unpublished data permitted to estimate parasite species richness using estimators of species richness, i.e. Jackknife first order and Chao 2. Most of the parasite species were rare, with low prevalence. Potential determinants were investigated as possible factors explaining the variability of parasites species richness among carnivores host body mass, host geographical range, host longevity and host density. Using independent contrasts, we found positive relationships between residuals of estimates of parasite species richness and residuals in host density, and between residuals of estimates of parasite species richness and residuals in host range. These results are discussed in terms of risk of extinction and invasion abilities related to a possible investment in immune defences correlated with parasite diversity.     

Herbivory and Body Size: Allometries of Diet Quality and Gastrointestinal Physiology,and Implications for Herbivore Ecology and Dinosaur Gigantism

Digestive physiology has played a prominent role in explanations for terrestrial herbivore body size evolution and size-driven diversification and niche differentiation. This is based on the association of increasing body mass (BM) with diets of lower quality, and with putative mechanisms by which a higher BM could translate into a higher digestive efficiency. Such concepts, however, often do not match empirical data. Here, we review concepts and data on terrestrial herbivore BM, diet quality, digestive physiology and metabolism, and in doing so give examples for problems in using allometric analyses and extrapolations. A digestive advantage of larger BM is not corroborated by conceptual or empirical approaches. We suggest that explanatory models should shift from physiological to ecological scenarios based on the association of forage quality and biomass availability, and the association between BM and feeding selectivity. These associations mostly (but not exclusively) allow large herbivores to use low quality forage only, whereas they allow small herbivores the use of any forage they can physically manage. Examples of small herbivores able to subsist on lower quality diets are rare but exist. We speculate that this could be explained by evolutionary adaptations to the ecological opportunity of selective feeding in smaller animals, rather than by a physiologic or metabolic necessity linked to BM. For gigantic herbivores such as sauropod dinosaurs, other factors than digestive physiology appear more promising candidates to explain evolutionary drives towards extreme BM.     

Group Composition, Home Range Size, and Diet of Three Sympatric Bamboo Lemur Species (Genus Hapalemur) in Ranomafana National Park, Madagascar

This is the first long-term, simultaneous, comparative study of three bamboo lemur species (Hapalemur griseus, H. aureus, and H. simus) at a site in southeastern-central Madagascar where they occur in sympatry. At Talatakely, Ranomafana National Park, the three Hapalemur spp. share overlapping home ranges. Hapalemur griseus has flexible group sizes, varying from three to nine individuals (n = 6). The home range of Hapalemur griseus averages 15 ha (n = 2). Hapalemur aureus forms family groups of 4 individuals (n = 3); they have a home range on average of 26 ha (n = 2). The single group of Hapalemur simus is composed of one or three adult males, two adult females, and their offspring; they occupy a home range of 62 ha. The three species of Hapalemur are year-round bamboo specialists: >88% of their diets consist of bamboo and grass in the Family Poaceae. Contrary to earlier findings, all three Hapalemur spp. consume the cynogenic parts—young leaf bases, young pseudopetioles, and young shoots—of the giant bamboo, Cathariostachys madagascariensis. They rely heavily on this plant, which comprises 72–95% of their diets. Hapalemur griseus and H. aureus consume similar proportions of bamboo vs. nonbamboo plants, though they differ in the species of bamboo they prefer. Hapalemur simus has the most distinct diet of the three bamboo lemurs. They exploit the young shoots of Cathariostachys madagascariensis during the austral summer rainy season, between November and April. From June to November, Hapalemur simus shifts its diet to eating the mature culm pith of Cathariostachys madagascariensis; the proportion of pith represented in their diet reaches a maximum of 89% in October. Seasonal availability of food resources, feeding competition, and factors related to body size may provide clues to the understanding of diet selection among the three sympatric Hapalemur spp.     

Evolution of Craniodental Correlates of Diet in African Bovidae

Establishing the relationship between craniodental morphology and dietary ecology in extant species permits inferences to be made about the ecology and biology of fossil species and the habitats they inhabited. Previous work linking diet and craniodental morphology has historically relied upon categorical classifications of diet and has not considered the phylogenetic signal (i.e., non-independence) of morphology due to shared evolutionary history. Here we use phylogenetic comparative methods to analyze the relationship between diet and eight craniodental indices for 40 species of African Bovidae using both categorical and continuous (stable carbon isotopes of enamel, δ¹³C) classifications of diet. In addition, we examine three modes of evolution that best explain interspecific variation in each of these indices, including: Brownian Motion (BM), Early Burst (EB), and Ornstein-Uhlenbeck (OU). Our results show that the hypsodonty index (HI), the length of the masseteric fossa relative to facial depth (MAS-F), and the length of the diastema relative to the total toothrow length (DIAS-TR) are the best predictors of diet among African bovids. These indices are best explained by either a BM or OU mode of evolution. Our findings have important implications for understanding the evolution of craniodental traits and reconstructing the diet of fossil mammals, especially bovids.     

Evolution, Ecology, and Multimodal Distributions of Body Size

The sizes of organisms are determined by their interactions with their environment and related ecological and evolutionary processes. Recent studies of body size distributions across communities show evidence for multimodality. The multiple modes were originally explained as a consequence of textural discontinuities in habitat structure. Because communities consist of species that are drawn from lineages, body size patterns within lineages will affect those that are expressed in communities. We used a cellular automation model to argue that multimodality in body sizes within lineages can arise from a few fundamental evolutionary mechanisms alone. We tested the hypothesis using body size data for 138 fish genera and found strong support for the idea that evolution structures body size distributions. The results suggest, first, that we should expect the distribution of body sizes within lineages to be multimodal and second, that a coherent theory of community body size distributions will need to combine both evolutionary and ecological perspectives. Received 28 January 2002; accepted 21 March 2002     

Sampling Effort in Neotropical Primate Diet Studies: Collective Gains and Underlying Geographic and Taxonomic Biases

Primates are among the most observable and best studied mammalian orders, yet the distribution of sampling effort by primatologists has inevitably concentrated on a few genera and a limited number of study sites. We present the first systematic review of sampling effort and associated biases in wild primate field research, focusing on dietary studies across the Neotropics. Our literature review of all 24 neotropical primate ecospecies spans 42 years (1969–2011) and covers 290 dietary studies at 164 study sites across 17 countries. We use a standardized measure of sampling effort to assimilate data sets derived from multiple methodologies and attempt to understand the distribution of effort (total equivalent to 193,804 h) using geographic variables and primate species traits. Results indicate that there are both geographic and taxonomic biases, with sampling effort generally skewed towards large-bodied species occupying large geographic ranges, and concentrated at a select few primatology research hubs. We also note that full primate assemblages at any given study site are rarely investigated. Our assessment thus reveals severely undersampled primate taxa and geographic regions that must be considered in future research. Current biases could be ameliorated by deliberately targeting poorly studied genera anywhere in their geographic distribution, well-studied genera in poorly studied regions, and striving to study multiple sympatric taxa within a single site. Although continued inequalities in sampling effort are probably inevitable, this study shows that this need not inhibit successful compilations and meta-analyses, provided that adequate data on feeding records and sampling effort can be made available.     

Hemodynamic and Metabolic Correlates of Perinatal White Matter Injury Severity

Background and Purpose

Although the spectrum of perinatal white matter injury (WMI) in preterm infants is shifting from cystic encephalomalacia to milder forms of WMI, the factors that contribute to this changing spectrum are unclear. We hypothesized that the variability in WMI quantified by immunohistochemical markers of inflammation could be correlated with the severity of impaired blood oxygen, glucose and lactate.

Methods

We employed a preterm fetal sheep model of in utero moderate hypoxemia and global severe but not complete cerebral ischemia that reproduces the spectrum of human WMI. Since there is small but measurable residual brain blood flow during occlusion, we sought to determine if the metabolic state of the residual arterial blood was associated with severity of WMI. Near the conclusion of hypoxia-ischemia, we recorded cephalic arterial blood pressure, blood oxygen, glucose and lactate levels. To define the spectrum of WMI, an ordinal WMI rating scale was compared against an unbiased quantitative image analysis protocol that provided continuous histo-pathological outcome measures for astrogliosis and microgliosis derived from the entire white matter.

Results

A spectrum of WMI was observed that ranged from diffuse non-necrotic lesions to more severe injury that comprised discrete foci of microscopic or macroscopic necrosis. Residual arterial pressure, oxygen content and blood glucose displayed a significant inverse association with WMI and lactate concentrations were directly related. Elevated glucose levels were the most significantly associated with less severe WMI.

Conclusions

Our results suggest that under conditions of hypoxemia and severe cephalic hypotension, WMI severity measured using unbiased immunohistochemical measurements correlated with several physiologic parameters, including glucose, which may be a useful marker of fetal response to hypoxia or provide protection against energy failure and more severe WMI.     

Diversity and Evolution of Body Size in Fishes

The diversity of body sizes observed among species of a clade is a combined result of microevolutionary processes (i.e. natural selection and genetic drift) that cause size changes within phylogenetic lineages, and macroevolutionary processes (i.e. speciation and extinction) that affect net rates of diversification among lineages. Here we assess trends of size diversity and evolution in fishes (non-tetrapod craniates), employing paleontological, macroecological, and phylogenetic information. Fishes are well suited to studies of size diversity and evolution, as they are highly diverse, representing more than 50% of all living vertebrate species, and many fish taxa are well represented in the fossil record from throughout the Phanerozoic. Further, the frequency distributions of sizes among fish lineages resemble those of most other animal taxa, in being right-skewed, even on a log scale. Using an approach that measures rates of size evolution (in darwins) within a formal phylogenetic framework, we interpret the shape of size distributions as a balance between the competing forces of diversification, pushing taxa away from ancestral values, and of conservation, drawing taxa closer to a central tendency. Within this context we show how non-directional mechanisms of evolution (i.e. passive diffusion processes) can produce an hitherto unperceived bias to larger size, when size is measured on the conventional log scale. These results demonstrate how the interpretation of macroecological datasets can be enriched from an historical perspective, and document the ways in which macroevolutionary and microevolutionary processes may be decoupled in the production of size diversity.     

Comparison Enhances Size Sensitivity: Neural Correlates of Outcome Magnitude Processing

Magnitude is a critical feature of outcomes. In the present study, two event-related potential (ERP) experiments were implemented to explore the neural substrates of outcome magnitude processing. In Experiment 1, we used an adapted gambling paradigm where physical area symbols were set to represent potential relative outcome magnitudes in order to exclude the possibility that the participants would be ignorant of the magnitudes. The context was manipulated as total monetary amount: ¥4 and ¥40. In these two contexts, the relative outcome magnitudes were ¥1 versus ¥3, and ¥10 versus ¥30, respectively. Experiment 2, which provided two area symbols with similar outcome magnitudes, was conducted to exclude the possible interpretation of physical area symbol for magnitude effect of feedback–related negativity (FRN) in Experiment 1. Our results showed that FRN responded to the relative outcome magnitude but not to the context or area symbol, with larger amplitudes for relatively small outcomes. A larger FRN effect (the difference between losses and wins) was found for relatively large outcomes than relatively small outcomes. Relatively large outcomes evoked greater positive ERP waves (P300) than relatively small outcomes. Furthermore, relatively large outcomes in a high amount context elicited a larger P300 than those in a low amount context. The current study indicated that FRN is sensitive to variations in magnitude. Moreover, relative magnitude was integrated in both the early and late stages of feedback processing, while the monetary amount context was processed only in the late stage of feedback processing.     

Ecological and Evolutionary Aspects of Integumentary Respiration: Body Size, Diffusion, and the Invertebrata

SYNOPSIS. Most animal phyla lack specialized respiratory surfacesand all phyla contain groups that, for some part of their lifehistory, depend entirely upon integumental diffusion of respiratorygases. Animals that are diffusion-limited, yet function aerobicallyare generally small with large surface areas and there has beenconvergence for this among all phyla including the coelomateinvertebrates. Acoelomates lack specialized respiratory structuresbut have highly modified integuments, functional specializations,and features ranging from symbioses to air gulping that compensatefor diffusion limitation. The diversity of structures functioningfor integumentary respiration is much greater among invertebratesthan vertebrates. Among the higher invertebrates with respiratorysurfaces, accessory integumentary O₂ uptake is usually 20 to50% of total respiration. The high diffusion constant of O₂in air minimizes boundary effects on gas transfer and permitslarger body size, although this is limited by dry conditions.Terrestrial annelids and flatworms, both confined to moist habitats,are larger than aquatic forms which often have accessory gills.Size differences between terrestrial forms in these two phylareflect the presence of a circulation in the annelids. Ontogenetictransitions from skin breathing to other respiratory structuresoccur among marine invertebrates and vertebrates. Vertebratesapparently exercise greater integratory control over integumentalrespiration through adjustment of ventilation and perfusion;however, it is not known if these processes occur in some invertebrates.     

Grey Matter Correlates of Three Language Tests in Non-demented Older Adults

Language has been extensively investigated by functional neuroimaging studies. However, only a limited number of structural neuroimaging studies have examined the relationship between language performance and brain structure in healthy adults, and the number is even less in older adults. The present study sought to investigate correlations between grey matter volumes and three standardized language tests in late life. The participants were 344 non-demented, community-dwelling adults aged 70-90 years, who were drawn from the population-based Sydney Memory and Ageing Study. The three language tests included the Controlled Oral Word Association Task (COWAT), Category Fluency (CF), and Boston Naming Test (BNT). Correlation analyses between voxel-wise GM volumes and language tests showed distinctive GM correlation patterns for each language test. The GM correlates were located in the right frontal and left temporal lobes for COWAT, in the left frontal and temporal lobes for CF, and in bilateral temporal lobes for BNT. Our findings largely corresponded to the neural substrates of language tasks revealed in fMRI studies, and we also observed a less hemispheric asymmetry in the GM correlates of the language tests. Furthermore, we divided the participants into two age groups (70-79 and 80-90 years old), and then examined the correlations between structural laterality indices and language performance for each group. A trend toward significant difference in the correlations was found between the two age groups, with stronger correlations in the group of 70-79 years old than those in the group of 80-90 years old. This difference might suggest a further decline of language lateralization in different stages of late life.     

Group Size, Home Range Use, and Seasonal Variation in the Ecology of Eulemur mongoz

We collected data during a 10-month study carried out on the mongoose lemur, Eulemur mongoz, at Anjamena in northwestern Madagascar, which provide baseline information on seasonal variation in the ecology, home range use and some aspects of the behavior of two neighboring groups. We monitored group size of nine groups in the study area and assessed them for seasonal variation. We present additional information collected during short-term surveys in other areas before and during the study for comparison. The study groups were small family units, and changes in group size were limited to births and emigrations of sexually mature progeny. In spite of clear seasonal changes in climate and vegetation, there is no variation in grouping patterns, so it is not possible to correlate variation in group size with seasonal variation of ecological variables. Comparison with ecological data from other field studies on lemurids reveals differences in food resource distribution in western forests versus other types of Malagasy forest. This distribution of food resources may predict home range size in mixed frugivorous–folivorous lemurs. Small home ranges, mainly in the West, could be correlated with a uniform distribution of food resources. Finally, we suggest that the dry season in the West may not present frugivorous–folivorous lemurs with major problems in finding an adequate food supply. This is supported by the lack of seasonal differences in ranging behavior of mongoose lemurs.     

Species,Diaspore Volume and Body Mass Matter in Gastropod Seed Feeding Behavior

Background

Seed dispersal of ant-dispersed plants (myrmecochores) is a well studied ecosystem function. Recently, slugs have been found to act as seed dispersers of myrmecochores. The aim of our study was to (1) further generalize the finding that gastropods feed on seeds of myrmecochores and hence may act as seed dispersers, (2) to test whether gastropod body mass and the volume of diaspores have an influence on the seed dispersal potential.

Methodology and Principal Findings

We assessed the seed dispersal potential of four slug and snail species with a set of seven myrmecochorous plant species from seven different plant families common to Central European beech forests. Diaspores differed in shape and size. Gastropods differed in their readiness to feed on diaspores and in the proportion of seeds that were swallowed as a whole, and this readiness generally decreased with increasing diaspore size. Smaller Arionid slugs (58 mm body length; mean) mostly fed on the elaiosome but also swallowed small diaspores and therefore not only act as elaiosome consumers, a nutrient rich appendage on myrmecochorous diaspores, but may also disperse seeds. Large Arionid slugs (>100 mm body length) swallowed diaspores of all sizes. Diaspores swallowed by gastropods were defecated without damage. Within-species variability in body size also affect seed dispersal potential, as larger individuals of the red slug (Arion rufus) swallowed more diaspores of wood anemone (Anemone nemorosa) than smaller ones.

Conclusions and Significance

Our results help to generalize the finding that gastropods consume and potentially disperse seeds of myrmecochores. The dispersal potential of gastropods is strongly influenced by diaspore size in relation to gastropod size.