Morphological diversity at different spatial scales in a Neotropical bat assemblage

The morphology of species can be used to represent their ecological position and infer potential processes determining the structure of species assemblages. This ecomorphological approach has been widely applied to the study of bat assemblages which mainly focuses on a single spatial scale and particular guilds. We extended such an ecomorphological approach to a multi-scale analysis of a Neotropical bat assemblage and its constituent guilds (aerial and gleaning insectivores, frugivores, and nectarivores) to describe their structure at different spatial scales and determine the relative importance of inter-specific competition, habitat filtering, or stochastic processes shaping such structures. We measured the occupied morphological space (size) defined by wing and skull morphology independently and the nearest-neighbour distance (structure) among species within these spaces at each spatial scale. Observed patterns were compared with random expectations derived from null models for statistical inference. When controlling for species richness and regional sampling effects in the null models, we did not find a significant effect of spatial scale in the morphological structure of the studied bat assemblage and guilds. Morphological structure followed the same patterns across scales as those expected from random drawings of sample size alone. Similar results were obtained regardless of morphological complex (wing and skull) and guilds. At both the assemblage and guild levels, bat morphological structure seems to be determined by regional, abiotic processes (e.g. habitat filtering) shaping the composition and organization of the species pool.     

A community-level evaluation of the impact of prey behavioural and ecological characteristics on predator diet composition

Although predation avoidance is the most commonly invoked explanation for vertebrate social evolution, there is little evidence that individuals in larger groups experience lower predation rates than those in small groups. We compare the morphological and behavioural traits of mammal prey species in the Taï forest, Ivory Coast, with the diet preferences of three of their non-human predators: leopards, chimpanzees and African crowned eagles. Individual predators show marked differences in their predation rates on prey species of different body sizes, but clear patterns with prey behaviour were apparent only when differences in prey habitat use were incorporated into the analyses. Leopard predation rates are highest for terrestrial species living in smaller groups, whereas eagle predation rates are negatively correlated with group size only among arboreal prey. When prey predation rates are summed over all three predators, terrestrial species incur higher predation rates than arboreal species and, within both categories, predation rates decline with increasing prey group size and decreasing density of groups in the habitat. These results reveal that it is necessary to consider anti-predator strategies in the context of a dynamic behavioural interaction between predators and prey.     

The evolution of social behaviour in Blaberid cockroaches with diverse habitats and social systems: phylogenetic analysis of behavioural sequences

The adequacy and utility of behavioural characters in phylogenetics is widely acknowledged, especially for stereotyped behaviours. However, the most common behaviours are not stereotyped, and these are usually seen as inappropriate or more difficult to analyze in a phylogenetic context. A few methods have been proposed to deal with such data, although they have never been tested on samples larger than six species, which limits their evolutionary interest. In the present study, we perform behavioural observations on 13 cockroach species and derive behavioural phylogenetic characters with the successive event‐pairing method. We combine these characters with morphological and molecular data (approximately 6800 bp) in a phylogenetic study of 41 species. We then reconstruct ancestral states of the behavioural data to study evolution of social behaviour in these insects with regard to their social systems (i.e. solitary, gregarious, and subsocial) and diversity of habitat choice. We report for the first time that nonstereotyped behavioural data are adequate for phylogenetic analyses: they are no more homoplastic than traditional data, and support several phylogenetic relationships that we discuss. From an evolutionary perspective, we show that the solitary species Thanatophyllum akinetum does not display original behavioural interactions, suggesting phylogenetic inertia of interactive behaviours despite a radical change in social structure. Conversely, the subsocial species Parasphaeria boleiriana shows original behavioural interactions, which could result from its peculiar social system or habitat. We conclude that phylogenetic approaches in studies of behaviour are useful for deciphering evolution of behaviour and discriminating between its different modalities, even for nonstereotyped characters. © 2013 The Linnean Society of London, Biological Journal of the Linnean Society, 2014, 111 , 58–77.     

Ecomorphological correlates in tropical stream fishes of southern India

Synopsis I studied ecomorphological correlations in 18 stream fish species (belonging to five families) commonly occurring in diversity rich habitats of rivers in the central Western Ghats (Southern India). Univariate and multivariate analyses indicated a clear segregation of species in morphological and ecological (habitat) space. Cluster analyses using morphological features segregated species based mainly on their body shape and feeding parameters while habitat parameters segregated species according to their position along the water column and preference to runs or pool habitats. Principal component analyses showed that body size, head dimensions, mouth position and eye diameter were important characters for species segregation in morphological space while run or pool habitat type and the position of the fish in the water column best explained segregation of species in habitat space. Consistencies in some of the species clusters obtained from analyses on morphological characteristics and habitat preferences warrant closer examination of the relationships between them. These were studied employing multivariate methods like canonical correspondence analysis and the Mantel test. The tests revealed weak correlations indicating that in addition to morphology, other factors like behavioural, physiological and evolutionary constraints together are likely to play an important role in ecosystem structuring of these complex tropical assemblages.     

Ecomorphological relationships of a guild of ground-foraging birds in northern California,USA

Summary We studied habitat and morphological relationships of nine species of birds comprising a groundforaging guild within four distinct locations in northern California. Although the nine species overlapped extensively in habitat use, we observed subtle differences among species in specific characteristics of the habitats they used. About 40% of all cases were classified to the correct species based on a discriminant analysis (DA) of habitats across all study areas. Classification success from DAs on habitats within study areas ranged from 42 to 66%. Morphologies of species differed to varying degrees as 91% of all cases were classified to correct species by a DA of morphological variables. This morphological separation suggested that each species used different modes of obtaining resources. We found only weak relationships between habitat use and morphology. Morphology predicted from 13.6 to 19.0% of the variation in habitat use within each study area and only 13.9% of the habitat variation across all study areas. Habitat predicted from 6.2 to 14.6% of the morphological variation within each study area and 6.9% across all study areas. We suggest that complimentary relationships of habitat and morphology enabled species within this guild to use unique sets of resources.     

Population Dynamics of the Polychaetous Annelids of an Intertidal Habitat in Upper Old Tampa Bay,Florida

Following an extensive red-tide induced mass mortality of the benthic macrofauna of a sandy intertidal habitat, the population dynamics of the polychaete species were studied. Detailed studies of the 12 most abundant species are presented. Data concerning total population levels, reproduction, recruitment, distribution within the intertidal zone, and gut content analyses are integrated in order to explain the observed spatial and temporal patterns of distribution and abundance. Potential competive interactions for food are considered to be the most important factor for explaining the observed ecological patterns. The polychaete species studied are divided into three trophic guilds: an omnivorous guild that feeds predaciously and as non-selective deposit feeders, a surface feeding guild consisting of species usually considered to be selective surface deposit feeders, and a subsurface feeding guild usually considered as non-selective infaunal deposit feeders. Within and between guild interactions are discussed.     

Niche segregation in high-altitude Himalayan chats (Aves,Turdidae): does morphology match ecology?

We investigated patterns of habitat segregation and morphological differentiation in syntopic, closely related turdid birds of the alpine zone of the Central Himalayas. Discriminant function analysis of 19 habitat structure parameters and comparisons of additional habitat features revealed that the species were distributed along gradients of vegetation height and vegetation density. In addition, non-vegetational structural habitat features, like microrelief variability or the presence of rocks and boulders, had strong discriminating power. In terms of habitat preferences the species of the guild investigated formed three subsets: shrubbery species (Erithacus pectoralis, E. chrysaeus and Hodgsonius phoenicuroides), species preferring open areas with higher surface roughness (Phoenicurus frontalis, Chaimarrornis leucocephalus) and the high-altitude species Grandala coelicolor. Using discriminant function analysis of 20 characters, morphology was analysed in relation to microhabitat utilization and foraging behaviour. Species inhabiting patches of shrubby thickets and foraging mainly by pedal movements (E. pectoralis, E. chrysaeus and H. phoenicuroides) have in common short rounded wings with high wing loading and strong legs and feet. Species preferably foraging by aerial hawking or perch and pounce techniques in more open areas (P. frontalis, C. chaimarrornis, and to some extent E. cyanurus) have longer wings, shorter tarsi and long rictal bristles. Grandala proved to be well adpated for long-distance flights at high altitudes (long, pointed wings) and for pedal foraging. Overall our results fit the basic assumption of ecomorphological theory that morphological distance reflects ecological distance. The ordination of each species in morphological space closely matched its distribution in ecological space (microhabitat, foraging strategies). Striking associations of morphology with ecology were not only evident for single traits but were also found in multidimensional comparisons: between-species Euclidian distances in ecology calculated from 19 habitat properties were in most cases equivalent to morphological distances calculated from 20 traits. In addition, in one of the two study areas species locations in the plane spanned by DFA axes of habitat use mirrored their positions in the morphological multivariate space. The observed distributions of the species in ecological and morphological space are interpreted as being mainly attributable to individualistic responses to the specific constraints of the alpine environment.     

Species co-occurrence, nestedness and guild–environment relationships in stream macroinvertebrates

1. Describing species distribution patterns and the underlying mechanisms is at the heart of ecological research. A number of recent studies have used null model approaches to explore mechanisms behind spatial variation in community structure.
2. However, unexplored questions are the degree to which single guilds of potentially competing stream macroinvertebrate species show: (i) interspecific segregation among-stream sites (i.e. occur together less often than expected by chance), suggesting competitive interactions; (ii) interspecific aggregation (i.e. occur together more often than expected by chance), suggesting similar responses to the environment; (iii) comply with nestedness, suggesting the existence of selective extinctions or colonisations and (iv) show similar environmental relationships.
3. The present analyses showed that guilds of stream macroinvertebrates exhibit non-random co-occurrence patterns that were generally contingent on the weighting of sites by stream size. Despite significant segregation of species, each guild also showed significantly nested patterns. Species richness was correlated with different environmental factors between the guilds, although these correlations were relatively low. By contrast, correlations between the major ordination axes and key environmental variables were slightly stronger in canonical correspondence analysis, and generally the same factors were most strongly correlated with variation in the species composition of each guild.
4. The present findings are the first to show that species within each stream macroinvertebrate guild show significant negative co-occurrence at the among-stream riffle scale. These findings present challenges for future studies that aim to disentangle whether these patterns comply with the habitat checkerboard or the competitive checkerboard explanations.     

Resource partitioning in rhinolophoid bats revisited

We assessed the ecomorphological structure of a guild of rhinolophoid bats in a Malaysian rainforest first described by Heller and von Helversen (1989). These authors found that the distribution of echolocation call frequencies used by 12 syntopic species was more even than expected from allometric relationships or in randomly generated communities, and that the observed minimal ratio was greater than expected by chance alone. In this study we were able to expand their guild to 15 species, but in doing so it became apparent that call frequencies might be less evenly distributed across the total frequency range than previously proposed. We replicated Heller and von Helversen’s (1989) analyses with the full 15-species complement but were unable to support their suggestion that rhinolophoid bats exhibit resource partitioning through differences in frequency bands. We adopted a multivariate approach and incorporated measures of body size and wing morphology into the analysis. We used phylogenetic autocorrelation to ensure that the species were statistically independentand principal component analysis to describe the morphological space occupied by the 15 species in the community and four additional species representing the extremes of phenotypic variation. We derived interspecific Euclidean distances and tested the mean values and SDs of these distances against those of 100 guilds of ”synthetic” species created randomly within the principal component space. The guild of Rhinolophoidea was not distributed randomly in multivariate space. Instead we found evidence of morphological overdispersion of the most similar species, which suggests niche differentiation in response to competition. Less similar species were nearer in morphological space than expected, and we suggest this is a consequence of ecological constraints on parameter combinations. Despite this underdispersion, many of the more distant neighbours were evenly rather than randomly spaced or clumped in morphospace, suggesting that, given the environmental constraints on morphology, species in this guild do experience limits to their similarity. Finally, we tested the influence of the relative abundance of species on morphological displacement, and found no evidence that abundant, spatially correlated species reduce interspecific overlap in morphological space. Received: 10 April 1999 / Accepted: 28 February 2000     

Does variation in morphology correspond with variation in habitat use in freshwater gastropods?

We tested if variations (i.e., breadth) in morphology and habitat use vary predictably among six aquatic gastropod species that were collected across Indiana and Illinois, USA. We predicted that interspecific morphological variation would positively covary with variation in habitat use among species. We used geometric morphometrics (Procrustes technique and relative warp analysis) to quantify morphology and multivariate analyses (PCA) to quantify habitat. Increased morphological breadth did not vary predictably with increased habitat breadth. However, we found that life history traits correspond with patterns in morphological and habitat breadth for these six aquatic gastropods. Pulmonate gastropods (use lungs for respiration) that lack an operculum cover exhibited decreased morphological breadth compared to coenogastropods (use gills for respiration). This pattern may ultimately be a function of behavioral adaptations in freshwater gastropods. Gastropods that are capable of breathing air or using other behavioral modifications such as burrowing to escape predators may not require high morphological breadth. Conversely, selection may favor higher morphological breadth in gastropods with gills that also do not move out of the water column to escape predators.     

Evolution of pedal digit orientation and morphology in relation to acquisition and secondary loss of the adhesive system in geckos

Among geckos, the acquisition of the adhesive system is associated with several morphological changes of the feet that are involved in the operation of the adhesive apparatus. However, analyses using a comparative framework are lacking. We applied traditional morphometrics and geometric morphometric analysis with phylogenetic comparative methods to morphological data, collected from X-ray scans, to examine patterns of morphological evolution of the pes in association with the gain and loss of adhesive capabilities, and with habitat occupancy among 102 species of gecko. Padbearing gecko lineages tend to have shorter digits and greater inter-digital angles than padless ones. Arboreal and saxicolous species have shorter digits than terrestrial species. Our results suggest repeated shifts that converge upon a similar padbearing morphology, with some modifications being associated with the habitat occupied. We demonstrate that functional innovation and habitat can operate on, and influence, different components of foot morphology.     

Spatial dynamics and expanded vertical niche of blue sharks in oceanographic fronts reveal habitat targets for conservation

Dramatic population declines among species of pelagic shark as a result of overfishing have been reported, with some species now at a fraction of their historical biomass. Advanced telemetry techniques enable tracking of spatial dynamics and behaviour, providing fundamental information on habitat preferences of threatened species to aid conservation. We tracked movements of the highest pelagic fisheries by-catch species, the blue shark Prionace glauca, in the North-east Atlantic using pop-off satellite-linked archival tags to determine the degree of space use linked to habitat and to examine vertical niche. Overall, blue sharks moved south-west of tagging sites (English Channel; southern Portugal), exhibiting pronounced site fidelity correlated with localized productive frontal areas, with estimated space-use patterns being significantly different from that of random walks. Tracked female sharks displayed behavioural variability in diel depth preferences, both within and between individuals. Diel depth use ranged from normal DVM (nDVM; dawn descent, dusk ascent), to reverse DVM (rDVM; dawn ascent, dusk descent), to behavioural patterns where no diel differences were apparent. Results showed that blue sharks occupy some of the most productive marine zones for extended periods and structure diel activity patterns across multiple spatio-temporal scales in response to particular habitat types. In so doing, sharks occupied an extraordinarily broad vertical depth range for their size (1.0-2.0 m fork length), from the surface into the bathypelagic realm (max. dive depth, 1160 m). The space-use patterns of blue sharks indicated they spend much of the time in areas where pelagic longlining activities are often highest, and in depth zones where these fisheries particularly target other species, which could account for the rapid declines recently reported for blue sharks in many parts of the world's oceans. Our results provide habitat targets for blue shark conservation that may also be relevant to other pelagic species.     

Mechanistic Approach to the Structure of Animal Communities: Anolis Lizards and Birds

The role of competition in structuring animal communities iscurrently hotly debated. One of the crucial assumptions underlyingthe concept of resource partitioning as a function of competitionis the jack-of-all-trades, master of none principle: differencesin morphology and behavior results in the different abilitiesto use different resources and hence results in the potentialto partition those resources. Examination of the manner by whichhabitat structure constrains resource use offers a mechanisticapproach to study community structure. Anolis lizards providea useful example to illustrate the approach since in the WestIndies they show consistent assemblages of ecomorphs from islandto island. The bases for a strong influence of habitat structureon the resource use pattern of anoles are reviewed as a preambleto a new analysis of the 2-species Anolis assemblages in theLesser Antilles. The two species on the island of Grenada showa strong morphological segregation associated with differentuse patterns of similar microhabitats. The two species on St.Kitts in a richer habitat show strong microhabitat segregationbut little morphological difference apart from size. A relatedpair of species on Antigua in a habitat similar to that on Grenadaappear to be constrained in the degree of habitat segregationand, perhaps as a consequence, show morphological segregationsimilar to that documented for the species on Grenada. Thesecomparisons provide further evidence of the strong influenceof habitat structure on the morphology and habitat partitioningpatterns of coexisting species. Field and experimental studiesof coexisting bird assemblages suggest that details of habitatstructure also have a strong influence on their morphology andresource use patterns. Studies focusing on the manner by whichanimals use different microhabitats provide a useful, mechanisticapproach to study the influence of competition on communitystructure     

The relationship between morphology, escape behaviour and microhabitat occupation in the lizard clade Liolaemus (Iguanidae: Tropidurinae: Liolaemini)

Phenotypic differences among species are known to have functional consequences that in turn allow species to use different habitats. However, the role of behaviour in this ecomorphological paradigm is not well defined. We investigated the relationship between morphology, ecology and escape behaviour among 25 species of the lizard clade Liolaemus in a phylogenetic framework. We demonstrate that the relationship between morphology and characteristics of habitat structure shows little or no association, consistent with a previous study on this group. However, a significant relationship was found between morphology and escape behaviour with the distance a lizard moved from a potential predator correlated with body width, axilla-groin length, and pelvis width. A significant relationship between escape behaviour and habitat structure occupation was found; lizards that occupied tree trunks and open ground ran longer distances from predators and were found greater distances from shelter. Behavioural strategies used by these lizards in open habitats appear to have made unnecessary the evolution of limb morphology that has occurred in other lizards from other clades that are found in open settings. Understanding differences in patterns of ecomorphological relationships among clades is an important component for studying adaptive diversification.     

Community structure, abundance, and morphology

The role of interspecific competition in structuring communities has been a highly debated issue for the last two decades. The nonrandom nature of morphological patterns within communities has been at the center of this controversy. Null models addressing community-wide dispersions in morphology have produced equivocal results and may be based on assumptions that are too restrictive (e.g., competitive exclusion or displacement). If morphological distinctiveness allows species to escape competitive pressures and exhibit higher densities, then a positive relationship should exist between morphological dissimilarity and abundance. We develop a suite of models that evaluates patterns in abundance that are associated with the morphological proximity of a species to other competitors. We evaluated the relationship between morphological distance and abundance from a variety of morphological perspectives, from those representing strictly diffuse interactions to those representing only interactions between a species and its nearest neighbor in morphological space. These models were sufficiently powerful to detect positive associations between abundance and morphological differences in a nocturnal desert rodent guild for which the effects of competition on structure are well established. Models such as these may be more useful than traditional models evaluating morphological dispersions for many reasons. They do not require that communities reach equilibrium before competitive interactions give rise to deterministic structure. They do not suffer from limitations of potentially inaccurate faunal pools or from phylogenetic constraints. Lastly, they may be used as a diagnostic tool in comparative studies to determine the degree to which competitive interactions structure communities.     

Relationships among habitat,ecomorphology and diets of cichlids in the Bladen River,Belize

The Neotropical Cichlidae is among the most species-rich and ecologically diverse groups of freshwater fishes. This study investigated interspecific morphological and ecological relationships within an assemblage of six cichlids in the Upper Bladen River, Belize. This portion of the river drains a nearly pristine watershed within a nature reserve, and thus should provide a natural ecological context for interpretation of ecological patterns. Species distributions within morphological, habitat and dietary space yielded patterns consistent with a hypothesis of niche partitioning. Statistical analyses of the species assemblage revealed relationships between two principal morphological gradients from multivariate analysis with several diet and habitat variables, and these patterns were consistent with prior functional morphological interpretations. Given that this local cichlid assemblage contains no congeneric species, it is apparent that morphological divergence resulting in niche segregation reflects selective establishment of species from a more species-rich regional species pool rather than in situ adaptive evolution.     

Decoupled evolution of display morphology and display behaviour in phrynosomatid lizards

A widespread trend in animals is the evolution of morphological ornaments and behaviours that are involved in aggressive and courtship displays. These display traits are important from the standpoint of communication, sexual selection, and speciation. Previous authors have suggested that the evolution of display morphology and display behaviour should be closely linked. In this study, I tested for this association with behavioural and morphological data for 59 taxa of phrynosomatid lizards using phylogenetic comparative methods (Mad-dison's concentrated changes test and Felsenstein's independent contrasts). The results showed little significant association between features of display morphology and behaviour, suggesting that the evolution of these traits is not tightly coupled. This decoupling is particularly evident in the genus Sceloporus , in which several species have lost the display coloration but retain unmodified display behaviour. The results also suggest that display morphology is more evolutionarily labile than display behaviour in this group.     

Does foraging mode mould morphology in lacertid lizards?

Evolutionary changes in foraging style are often believed to require concurrent changes in a complex suite of morphological, physiological, behavioural and life-history traits. In lizards, species from families with a predominantly sit-and-wait foraging style tend to be more stocky and robust, with larger heads and mouths than species belonging to actively foraging families. Here, we test whether morphology and foraging behaviour show similar patterns of association within the family Lacertidae. We also examine the association of bite force abilities with morphology and foraging behaviour. Lacertid lizards exhibit considerable interspecific variation in foraging indices, and we found some evidence for a covariation between foraging style and body shape. However, the observed relationships are not always in line with the predictions. Also, the significance of the relationships varies with the evolutionary model used. Our results challenge the idea that foraging style is evolutionarily conservative and invariably associated with particular morphologies. It appears that the flexibility of foraging mode and its morphological correlates varies among lizard taxa.