Body Size Of Species Research Articles

Relative importance of meso‐ and microhabitat features in the within‐reach spatial distribution of size‐structured fish assemblages in small streams

AbstractThis study aimed to explore the relative importance of mesohabitat and microhabitat features, as well as the spatial and within‐day temporal covariates, on the body size‐related within‐reach spatial distribution of stream‐dwelling fishes in a highland‐type and a sub‐mountainous‐type stream in Central Europe. During daytime, point abundance sampling was applied to catch the fish, and environmental data were recorded at the sampling points (microhabitat features) and along the transects that crossed the sampling points (mesohabitat features). Variance partitioning revealed similar patterns in the size‐classified fish data for the two streams. Microhabitat features had a greater explained variance than mesohabitat features. The majority of the mesohabitat influence emerged as variance shared with the microhabitat influence. The pure spatially explained variance proportion was lower than the variance explained purely by the environmental features (meso and micro together), and no temporally explained variance was found. Many species showed body size‐related environmental associations. The results suggest that the different‐scale habitat features act in a hierarchical way on the within‐reach fish distribution. Meso‐scale features may determine a great proportion of the micro‐scale habitat variability and micro‐scale conditions may directly affect how fish select places to stay as a function of both species identity and body size. The restoration of meso‐scale environmental diversity can effectively contribute to the protection of size‐structured populations in sub‐mountainous and highland streams.

Future shock: Ocean acidification and seasonal water temperatures alter the physiology of competing temperate and coral reef fishes

Climate change can directly (physiology) and indirectly (novel species interactions) modify species responses to novel environmental conditions during the initial stages of range shifts. Whilst the effects of climate warming on tropical species at their cold-water leading ranges are well-established, it remains unclear how future seasonal temperature changes, ocean acidification, and novel species interactions will alter the physiology of range-shifting tropical and competing temperate fish in recipient ecosystems. Here we used a laboratory experiment to examine how ocean acidification, future summer vs winter temperatures, and novel species interactions could affect the physiology of competing temperate and range-extending coral reef fish to determine potential range extension outcomes. In future winters (20 °C + elevated pCO2) coral reef fish at their cold-water leading edges showed reduced physiological performance (lower body condition and cellular defence, and higher oxidative damage) compared to present-day summer (23 °C + control pCO2) and future summer conditions (26 °C + elevated pCO2). However, they showed a compensatory effect in future winters through increased long-term energy storage. Contrastingly, co-shoaling temperate fish showed higher oxidative damage, and reduced short-term energy storage and cellular defence in future summer than in future winter conditions at their warm-trailing edges. However, temperate fish benefitted from novel shoaling interactions and showed higher body condition and short-term energy storage when shoaling with coral reef fish compared to same-species shoaling. We conclude that whilst during future summers, ocean warming will likely benefit coral reef fishes extending their ranges, future winter conditions may still reduce coral reef fish physiological functioning, and may therefore slow their establishment at higher latitudes. In contrast, temperate fish species benefit from co-shoaling with smaller-sized tropical fishes, but this benefit may dissipate due to their reduced physiological functioning under future summer temperatures and increasing body sizes of co-shoaling tropical species.

Variation in body size drives spatial and temporal variation in lobster-urchin interaction strength.

How strongly predators and prey interact is both notoriously context dependent and difficult to measure. Yet across taxa, interaction strength is strongly related to predator size, prey size and prey density, suggesting that general cross-taxonomic relationships could be used to predict how strongly individual species interact. Here, we ask how accurately do general size-scaling relationships predict variation in interaction strength between specific species that vary in size and density across space and time? To address this question, we quantified the size and density dependence of the functional response of the California spiny lobster Panulirus interruptus, foraging on a key ecosystem engineer, the purple sea urchin Strongylocentrotus purpuratus, in experimental mesocosms. Based on these results, we then estimated variation in lobster-urchin interaction strength across five sites and 9 years of observational data. Finally, we compared our experimental estimates to predictions based on general size-scaling relationships from the literature. Our results reveal that predator and prey body size has the greatest effect on interaction strength when prey abundance is high. Due to consistently high urchin densities in the field, our simulations suggest that body size-relative to density-accounted for up to 87% of the spatio-temporal variation in interaction strength. However, general size-scaling relationships failed to predict the magnitude of interactions between lobster and urchin; even the best prediction from the literature was, on average, an order of magnitude (+18.7×) different than our experimental predictions. Harvest and climate change are driving reductions in the average body size of many marine species. Anticipating how reductions in body size will alter species interactions is critical to managing marine systems in an ecosystem context. Our results highlight the extent to which differences in size-frequency distributions can drive dramatic variation in the strength of interactions across narrow spatial and temporal scales. Furthermore, our work suggests that species-specific estimates for the scaling of interaction strength with body size, rather than general size-scaling relationships, are necessary to quantitatively predict how reductions in body size will alter interaction strengths.

Beyond latitude: Temperature, productivity and thermal niche conservatism drive global body size variation in Odonata

AbstractAimSo far, latitudinal body size clines have been discussed primarily in the context of thermoregulation, sensu Bergmann. However, body size patterns are ambiguous in ectotherms, and this heterogeneity remains poorly understood. We tested whether Bergmann's rule and the resource availability rule, which states that energetic requirements determine species body size, apply to damselflies and dragonflies (Odonata). Furthermore, we hypothesized that the contrasting effects of thermoregulation and resource availability (e.g., productivity) can obscure the overall gradient in body size variation.LocationGlobal.Time periodContemporary.Major taxa studiedOdonata.MethodsUsing data for 43% of all odonate species described so far, we tested our hypotheses in phylogenetically and spatially comparative analyses at assemblage and species levels. For the distribution data, we integrated expert range maps and ecoregional ranges based on all available occurrence records. To distinguish between long‐term and evolutionarily recent responses of environmental drivers in body size, we constructed a phylogenetically informed classification of all odonate species and decomposed the body size into its phylogenetic and specific components for our subset of species.ResultsWe documented a weak positive relationship between body length and latitude but found strong and contrasting effects for temperature between dragonflies and damselflies and consistent positive effects for productivity that explained 35–57% of body size variation. Moreover, we showed a strong phylogenetic signal in sized‐based thermoregulation that shaped the distribution of dragonflies, but not of damselflies.Main conclusionsWe concluded that temperature, productivity and conservatism in size‐based thermoregulation synergistically determine the distribution of ectotherms, while the taxon‐specific importance of these factors can lead to contrasting and weak latitude–size relationships. Our results reinforce the importance of body size as a determinant of species distributions and responses to climate change.

Changes in body size in some bird species from the Yucatán peninsula since the Late Pleistocene

AbstractDuring the Pleistocene, the Yucatán Peninsula reached its greatest geographic extension, with 457,650 km2, but the rise of sea level after the Last Glacial Maximum (ca. 20,000–12,000 years ago) reduced its area to 225,182 km2(50.8% reduction). These geographic extension changes likely modified the extension of different habitats throughout the peninsula, which may have also promoted morphological changes in the species that inhabit this region. Here, we tested if the reduction of the geographic size of the Yucatán Peninsula may have promoted changes in the body size of three fossil bird species and two modern bird species. We compared Late Pleistocene bird fossils specimens from Loltún, Yucatán, Mexico (ca. 28,000–11,700 ya), San Josecito Cave and Tlapacoya, and study skins of collected specimens. To assess the area‐scale ratio and to establish if body size changes occurred over time from a large to a small body size, we relied on the “island rule” as a framework; we also relied on Bergmann's rule, which postulates a decreasing in size from north to south in homeothermic species to recognize if these birds show a north to south cline. Based on body mass and measurements of the tarsometatarsi, a reliable proxy for the estimation of body size, we performed statistical analyses to test for differences between fossil and non‐fossil birds, as well as to test a gradient in body mass north to south. We found a statistically significant trend in body size changes through time, from small body sizes in fossil birds to larger body sizes in non‐fossil birds. These results suggest that relatively recent ecological factors related to the environmental carrying capacity may have promoted body size variations in birds from the Yucatán Peninsula. We also found that modern population of bird species follow Bergmann's rule.

Altitudinal gradients and body size variation among Chinese lizards in different terrains

AbstractSpatial patterns of body size are associated with environmental factors like temperature, seasonality, precipitation, resources, and altitude, among the most relevant. Latitudinal size patterns have been extensively studied. Studies on altitudinal gradients of body size, however, are relatively few. Besides, it is still unclear whether there is variation in the relationship between environmental factors and body size of species, or correlations within different altitudes. China provides a good opportunity to assess the altitudinal gradients of body size, because the entire terrain of China changes from high altitude in the west to low altitude in the east, with three natural terrain stages (low: less than 660 m.a.s.l.; medium: 660–2600 m.a.s.l.; and high: more than 2600 m.a.s.l.). Similarly, lizards are distributed across a wide altitudinal range (from −154.31 m to ~6000 m above sea level). We examined 211 lizard species in China and assessed the altitudinal gradients of Chinese lizard body sizes at assemblage and interspecific levels. Piecewise structural equation models (pSEM) were used to investigate the direct and indirect relationships between body size and environmental factors within different terrains (low, medium, and high altitudes). Overall, we found that body size in Chinese lizards decreases with increasing altitude. However, there were variations in the altitudinal gradients and drivers within the three terrain stages. Altitude has both direct (medium and low stages) and indirect (high stages) effects in shaping lizard size. We established that body size increased with increasing altitudes in the low and medium terrain stages. Seasonality had different effects on body size in medium (positively) and low (negatively) stages. However, among the three terrain stages, temperature was consistently negatively correlated with lizard size. Overall, we identified complex patterns and drivers of altitudinal gradients of body size within the three terrain stages, probably due to the different environmental conditions across altitudes.

A case report of an Eurasian jay (Garrulus glandarius) attacking an incubating adult and depredating the eggs of the Japanese tit (Parus minor).

In May 2021, we opportunistically observed one Eurasian jay (Garrulus glandarius) attacking an adult incubating Japanese tit (Parus minor) and depredating nine tit eggs at a nest box where a woodpecker had greatly enlarged the entrance. After the predation event, the Japanese tits abandoned the nest. We recommend that when using artificial nest boxes to protect hole-nesting birds, the appropriate entrance size should be proportional to the body size of the target species. This observation gives us a better understanding of the potential predators of secondary hole-nesting birds.

TimeFISH: Long-term assessment of reef fish assemblages in a transition zone in the Southwestern Atlantic.

The TimeFISH database provides the first public time-series dataset on reef fish assemblages in the southwestern Atlantic (SWA), comprising 15 years of data (2007-2022) based on standardized Underwater Visual Censuses (UVCs). The rocky reefs covered by our dataset are influenced by pronounced seasonal cycles of ocean temperatures with warm tropical waters from the Brazil Current in the summer (~27°C) and colder waters from the La Plata River Plume discharge and upwelling from the South Atlantic Central Water in the winter (~18°C). These oceanographic conditions characterize this area as the southernmost tropical-subtropical climatic transition zone in the Atlantic Ocean. As a result, reef fish assemblages are comprised of both tropical and subtropical species. All records included in TimeFISH were collected using UVCs, a nondestructive method that allows the estimation of fish species richness, abundance, and body size distributions. UVCs were performed through 40 m2 belt transects by scuba diving in nine locations along the southern Brazilian coast (25-29°S). Four of these locations lie within the boundaries of the no-entry Arvoredo Marine Biological Reserve, where fishing and recreational activities are forbidden, and the remaining locations are unprotected from these activities. During each belt transect, a diver swam at a constant depth above and parallel to the reef, identifying fish species, counting the number of individuals, and estimating the total body length (Lt in cm) of all detected individuals. All fish individuals in the water column (up to 2 m above the substratum) and at the bottom were targeted. In total, 202,965 individuals belonging to 163 reef fish species and 53 families were recorded across 1857 UVCs. All survey campaigns were funded by either public or mixed capital (private-public) sources, including seven grants from the Brazilian federal and Santa Catarina state governments. Part of the data has already been used in multiple MS.c. and Ph.D. theses and scientific articles. TimeFISH represents an important contribution for future studies aiming to examine temporal and spatial variations of reef fish assemblages in transition zones. No copyright restrictions apply to the use of this data set, other than citing this publication.

A matter of size: Does habitat use depend on body size in Amazonian small-stream shrimp species?

ABSTRACT Natural selection is a key driver of organism size and shape, so resource use often depends on individual size. Among populations and assemblages there is overwhelming evidence that size- or stage-specific effects on niche occur mainly in habitat and food dimensions. A 2019 study by E. P. Silva and others, “Habitat segregation among freshwater shrimp species in an Amazonian rainforest stream system,” showed that Amazonian small-stream shrimp species show only slight habitat segregation at the scale of 50 m stream reaches, but that study did not take into account possible effects of intraspecific and interspecific differences in body size on habitat selection. We investigated through nighttime observations if conspecific shrimp of different sizes overlap in habitat use and whether heterospecific individuals of similar sizes differ in habitat use. Generalized linear mixed models were used to test possible relationships between body size and habitat features, and multivariate linear analysis and latent-variable model-based ordination were used to test for intraspecific and interspecific differences in habitat use. Mean frequency of use of habitat features differed among shrimp of different sizes and species, but use of habitat components strongly overlapped. Interspecific habitat overlap was greater among small individuals than large individuals. Our results indicate that size is not a major driver of habitat segregation in shrimp populations and assemblages, although it provides evidence of subtle ontogenetic shifts in habitat use by conspecifics of different sizes as well as differences between individuals of different species with similar sizes.

Marine conservation palaeobiology: What does the late Quaternary fossil record tell us about modern-day extinctions and biodiversity threats?

Abstract Near-time conservation palaeobiology uses palaeontological, archaeological and other geohistorical records to study the late Quaternary transition of the biosphere from its pristine past to its present-day, human-altered state. Given the scarcity of data on recent extinctions in the oceans, geohistorical records are critical for documenting human-driven extinctions and extinction threats in the marine realm. The historical perspective can provide two key insights. First, geohistorical records archive the state of pre-industrial oceans at local, regional and global scales, thus enabling the detection of recent extinctions and extirpations as well as shifts in species distribution, abundance, body size and ecosystem function. Second, we can untangle the contributions of natural and anthropogenic processes by documenting centennial-to-millennial changes in the composition and diversity of marine ecosystems before and after the onset of major human impacts. This long-term perspective identifies recently emerging patterns and processes that are unprecedented, thus allowing us to better assess human threats to marine biodiversity. Although global-scale extinctions are not well documented for brackish and marine invertebrates, geohistorical studies point to numerous extirpations, declines in ecosystem functions, increases in range fragmentation and dwindling abundance of previously widespread species, indicating that marine ecosystems are accumulating a human-driven extinction debt.

Robustness of Bergmann’s and Rapoport’s rules to different geographical range estimates in New World pit vipers

AbstractAimBergmann's and Rapoport's rules are two ecogeographical patterns that predict an increase in species body size and range size, respectively, with increasing latitudes. Here, we evaluated whether using different geographical range estimates affects the assessment of Bergmann's and Rapoport's rules at the cross‐species and assemblage levels in New World pit vipers.LocationNew World.TaxonNew World pit vipers (Crotalinae).MethodsWe estimated geographical ranges for 135 (i.e. ≈93%) Crotalinae species using ecological niche modelling (ENM) and expert maps and assessed alternative hypotheses that could account for Bergmann's and Rapoport's rules. We evaluated both rules using ‘cross‐species’ (i.e. species as units of observation) and ‘assemblage’ (i.e. sites/grid cells as units of observation) approaches. We used phylogenetic generalized least squares (PGLS) analyses and generalized least squares (GLS) analyses to account for phylogenetic and spatial autocorrelation that could affect the evaluation of these rules at the cross‐species and assemblage levels, respectively.ResultsExpert maps differed significantly from ENM ranges. The cross‐species approach was robust to these different range estimates when Bergmann's and Rapoport's rules were evaluated. The assemblage analyses were more vulnerable to different range estimates, where contrasting results were observed in the assessment of Bergmann's rule but not in the evaluation of Rapoport's rule.Main ConclusionsDifferent geographical range estimates affected mainly the assessment of ecogeographical rules at the assemblage level, whereas the cross‐species analyses were more robust. However, this increased susceptibility of the assemblage approach to different range estimates was only observed when evaluating Bergmann's rule. Thus, our findings suggest that ecogeographical rules can have different levels of sensitivity to different range estimates, which can especially affect the assemblage‐level assessment of these ecogeographical patterns.

Spatial variation of parrotfish assemblages at oceanic islands in the western Caribbean: evidence of indirect effects of fishing?

Fish populations that bear considerable pressure levels tend to show a decline in the average size of individuals, with the small and unexploited species replacing the large and exploited ones. It is important to carry on with their characterization in areas where they are becoming an important source of food for local human populations. An example of such species are parrotfishes, whose responses to external factors such as fishing need to be understood and predicted. In this study, we used a diver-operated stereo-video to examine individual body size, sex ratios and proportion of species of the parrotfish assemblage and analyze them on a qualitative fishing pressure gradient at four oceanic islands in the Colombian Caribbean. We reported over 10,000 occurrences of eleven parrotfish species, of which we estimated the total length of over 90%, grouping them into three size categories (large, medium, and small). Our data showed a spatial variation of parrotfishes' abundances, biomass, and individual body size. Observed differences are size-category-dependent throughout the qualitative fishing pressure. In general, the medium-bodied species had smaller sizes, lower abundances, and thus lower contribution to the total parrotfish biomass at the most heavily fished island. Unexpectedly, we found evidence of possible indirect effects over the small-bodied species Scarus iseri and Scarus taeniopterus with significantly greater abundances, and larger sizes of males of S. iseri, at the higher fishing pressure sites. Overall, our data highlights the extent of the spatial variation in the parrotfish communities at relatively short distances, and present new insights into the responses of parrotfish species on a spectrum of body sizes along a gradient of human pressure.

Biogeochemical shifts and zooplankton responses in post-CAAA northeastern lakes: The success of acid recovery, complexity of biological recovery, and value of long-term monitoring

Lakes in the northeastern U.S., as in other regions, experienced significant declines in water quality and ecosystem health in the mid to late 20th century as atmospheric deposition from industrial emissions caused surface waters to acidify. After the Clean Air Act Amendments of 1990 enhanced regulations to limit emissions of sulfur and nitrogen, many lakes in the Northeast recovered from acidification. The organisms that inhabit lakes are susceptible to these shifts, and zooplankton can serve as valuable indicators of lake ecosystem responses to shifts due to their position as primary consumers in the food web. We evaluated a large historical dataset from the U.S. Environmental Protection Agency (EPA) Eastern Lake Survey (ELS) of 143 lakes throughout the northeastern U.S. to understand how recovery from acidification and subsequent chemical changes influenced zooplankton body size and community composition. We observed significant changes in chemistry; surface water sulfate concentrations decreased by 22% in the ELS lakes between the two sample years of 1986 and 2004. Increasing concentrations of DOC are common from the combined influence of deacidification and climate change, and the ELS lakes experienced a 26% increase in DOC. Notably, in the more developed regions of our study area, chloride concentration in lakes tripled, likely due to increased use of road deicers, and this is related to a subsequent increase in calcium and magnesium base cations. Zooplankton body size increased significantly between 1986 and 2004 across all taxa, and body size of Daphnia species, which require higher amounts of calcium than other zooplankton taxa, was positively associated with high calcium lakes. Shifts in zooplankton community structure, however, were most strongly influenced by variation in ANC, sulfate, and DOC. Our findings indicate that, while surface water acidity has a strong influence on zooplankton community structure, zooplankton populations are likely on a different trajectory than a simple recovery due to multiple chemical changes, such as increased chloride, occurring in lakes undergoing acid recovery. These, along with changes in climate and land-use, elicit multiple simultaneous responses in zooplankton communities.

Variations in Patch Use by Ruminant and Non-Ruminant Herbivores in a Tropical Wildlife Reserve, Ghana

Food processing and consumption by herbivores are affected differently by the availability of forage quality and quantity per unit of time. This demonstrates the “Allometric response concept”, and it is considered a significant determinant in habitat use for foraging by grazers. The relevance of this approach has comprehensively been applied to herbivores of different body sizes, but little is known about its demonstration to explain patch use in herbivores with different digestive physiology and body size. We explain the use of patches by grazing herbivores of different digestive physiology and body sizes, Hippopotamus amphibius (hippopotamus, mega non-ruminant) and cattle (ruminant), by integrating foraging relationship herbivores. We analysed the significant relationships between species dropping densities and environmental variables across forty-eight 100 m×100 m plots in Bui National Park, Ghana, during the wet and dry seasons. We found that both species utilised areas closer to the river in the wet season, but the H. amphibius foraged further away from the river during the dry season. Sward height also determined patch use by both species, with the H. amphibius utilising shorter swards than the cattle. Considering the quality of food resources, the study revealed that patch selection of ruminants (cattle) was significantly influenced by nitrogen content. In contrast, acidic detergent fibre content was positively related to non-ruminant species (H. amphibius). The high seasonal effect of sward height and food quality on patch use is primarily due to the species digestive physiology and body size of hippopotamus and cattle at the Bui National Park.

Male agility in relation to mating success in two non‐territorial damselflies

AbstractMale body size is usually correlated with mating success in insects. For non‐territorial species, the small male advantage hypothesis predicts that smaller males may be favoured in sexual selection because small body size may predict agility and manoeuvrability. Consequently, selection for male size may drive the evolution of female‐biased sexual size dimorphism (SSD). Nevertheless, recent evidence shows that non‐territorial male damselflies that actively search for females may be larger and more agile than those that perch and wait for females to appear. Thus, here we addressed whether the male size is an indicator of male agility and if it may be used to predict male reproductive success in two non‐territorial damselflies. To this end, we conducted a field study with Acanthagrion truncatum Selys, 1876 and A. lancea Selys, 1876 (Zygoptera, Coenagrionidae). Males of A. truncatum adopt a sit‐and‐wait mating strategy, while the males actively search for females in A. lancea. Hence, we expected different selective forces acting on male body size and agility in these species. We compared the body size and wing length of mated and unmated males, and between sexes, to describe their patterns of SSD. Our results suggest that wing length can be used as a proxy for male body size and agility in both species. However, we have found no evidence for the small male advantage that could explain wing dimorphism in A. truncatum, nor selection for larger males in A. lancea. In conclusion, this study corroborates other studies that suggest agility cannot explain SSD in non‐territorial damselflies and fail to support the small male advantage hypothesis.

Algal Density Controls the Spatial Variations in Hg Bioconcentration and Bioaccumulation at the Base of the Pelagic Food Web of Lake Taihu, China.

Algal density can significantly impact mercury (Hg) bioaccumulation and biomagnification in aquatic food webs, but the underlying mechanisms remain controversial especially in subtropical and tropical regions. We conducted a comprehensive field study on Hg bioconcentration in phytoplankton and bioaccumulation in size-fractionated zooplankton across 17 sampling sites in Lake Taihu, a large shallow lake in eastern China with large spatial differences in algal density. The higher algal density in the northern sites is highly associated with the lower THg bioconcentration factor (BCF) in phytoplankton and lower THg bioaccumulation factor (BAF) in zooplankton. The low Hg BCFs or BAFs at productive sites could not be explained by algal bloom dilution but attributed to the low Hg bioavailability, which is highly associated with the elevated pH levels at productive sites. The smaller body size of the dominant zooplankton species at higher algal density sites also contributed to their lower Hg bioaccumulation. Importantly, we provide evidence that high algal density is associated with a low proportion of methylmercury (MeHg) in total Hg (% MeHg) in phytoplankton, which is further transferred to zooplankton. Such a low THg BCF or BAF and low % MeHg in plankton at high algal density sites hamper the entry of Hg into the pelagic food webs, which are important but yet underestimated driving forces for the low Hg contents in pelagic fish that are commonly observed in anthropogenic-impacted eutrophic lakes in subtropical regions.

New Material of Schizotheriine Chalicothere (Perissodactyla, Chalicotheriidae) from the Xianshuihe Formation (Early Miocene) of Lanzhou Basin, Northwest China

A new schizotheriine mandible from the early Miocene Xianshuihe Formation in Lanzhou Basin, Northwest China is described here. Compared with other contemporaneous taxa, the lower jaw is most similar to Borissiakia betpakdalensis from Kazakhstan based on mandibular morphology and dental features, except for a much smaller body size which is hardly explained by intraspecific variation and suggests it represents a smaller body-sized species of Borissiakia. The type specimen of Phyllotillon huangheensis, from the same strata of the Lanzhou Basin, shares characters with the new specimen in the lower cheek teeth and the tapered morphology of the anterior horizontal ramus. Differences between both are reflected in the height of the ramus, especially the level of the symphysis, which may be an expression of sexual dimorphism. Therefore, schizotheriine mandibles from the early Miocene of Lanzhou Basin are regarded as the same taxon, and both are recognized as Borissiakia huangheensis. The occurrence of a chalicothere and other large perissodactyls may suggest that a certain amount of open woodland was distributed across the basin and that the paleoclimate might have been more humid during the early Miocene.

Body size of raccoons (Procyon lotor) introduced in west-central Hokkaido, Japan: evaluation using two spatial scales

Evaluating body size as an indicator of life history traits is essential for the proper management of invasive species. The body size of alien species may change due to differing climates at the latitudinal scale and presence of anthropogenic food at a regional scale; however, only few studies have examined spatial variation in body size of alien carnivores at two spatial scales. In this study, we evaluated the body size of adult raccoons ( Procyon lotor (Linnaeus, 1758)) inhabiting Hokkaido, Japan, by comparing populations from different latitudes. Second, we examined the contribution of anthropogenic food (i.e., residential areas, crop field areas, and livestock farm density) to variations in body size in our study area in west-central Hokkaido. Using body mass as an index of body size, we found that body size did not change along latitudinal clines. Thus, the body mass of omnivorous carnivores may be unaffected by climatic variations. On a regional scale, anthropogenic food did not affect the body mass of raccoons. Thus, anthropogenic food is only supplemental for raccoons in our study area, if at all. We conclude that implementing culling programs are essential for effectively managing invasive species, rather than preventing their consumption of anthropogenic food.

Insular nestling growth and its relationship to parental care effort in Silvereyes, Zosterops lateralis

ABSTRACT The rate at which avian offspring grow can have consequences for survival and reproductive output as an adult and is known to vary widely among and within species. This variation is thought to be an adaptive response to cope with environmental variation. The principal environmental factors affecting growth are food availability and predation risk, predominantly acting as constraints on parental care. Islands pose an interesting system to explore growth rate dynamics, because the characteristic insular features of high population densities and depauperate predator diversity translate into a potentially food limited environment with low predation risk. Insular environments typically produce populations with slower life history strategies and larger body size in small-bodied species, features that are likely to be mediated by growth rate. We describe the nestling growth of an insular population of Silvereyes and how it relates to parental size and parental care. Neither parental size nor parental care explained insular nestling growth rate, even though food acquisition is thought to underpin avian growth rates. This could be due to a mismatch between acquisition and allocation of resources by nestlings. Compared to a small number of mainland nestlings, the island growth curve asymptotes were significantly larger and inflection points much later, but insular growth rates were only marginally slower. This is in line with proposed insular adaptations required to produce larger body size on islands, however understanding the mechanism underlying this pattern will require data on the relationship between food quality and acquisition, and physiological allocation of resources within individuals.

Symmetries and asymmetries in the topological roles of piscivorous fishes between occurrence networks and food webs.

Ecological networks represent the architecture over which diversity is assembled. The compartmentalization of trophic links and the spatial aggregation of species determine ecosystem dynamics and stability. Species traits such as body size or those related to dispersal ability or environmental and trophic niche may determine the role of a species in different ecological networks such as food webs and occurrence networks. However, the empirical analysis of these connections and their determinants were seldom considered. Our study focused on 16 species of piscivorous fishes from 27 water bodies of the Paraná River floodplain, which were surveyed between 4 and 20 times over 5 years. Occurrence networks and food webs were built from abundance of species by site and preys by gut content. Using null models and methods for weighted bipartite networks, we evaluated the compartmentalization in both kinds of networks. The topological roles of species in each network along four hydro-climatic conditions were calculated, based on their membership in a module standardized within module connectivity 'z' and between module connectivity 'c' and related to species body size and 30 eco-morphological variables. A significant modular organization in feeding links and species occurrences was detected. While species of larger body size seem to have a main role connecting modules in food webs, the smaller size species foster the connection among spatial aggregations. However, body size was not the main determinant of intra module connectivity. Morphologies associated with linear races (fusiform body) and manoeuvrability (orbicular body) and predation behaviours were consistently related to intra and inter-module connectivity in food webs and occurrence networks. Our results support the modular organization of food webs and occurrence networks of the main consumers of the Paraná River floodplain and the trait-related interrelationship among these networks. Furthermore, the dynamic nature of the trait-role association may foster the stable modular structure observed at higher levels. The recognition of the connecting role of the species in the different networks will improve the understanding of their importance in the functioning of ecosystems, thus enhancing the knowledge of the mechanisms shaping biodiversity.