Foraging mode of the chameleon,Bradypodion pumilum: a challenge to the sit‐and‐wait versus active forager paradigm?

Foraging mode is an important aspect of life history, often associated with traits such as locomotor mode, energy budget, risk of predation and reproductive effort. Because of these life-history associations, classification of foraging mode can be conceptually useful. Lizards figured prominently in the historical development of foraging mode concepts, yet our current understanding is dominated by only two lizard families which are good examples of the two extreme modes, sit-and-wait vs. active foraging. A great deal of lizard phylogenetic diversity remains unrepresented. Chameleons are a highly derived lizard taxon for which we have very little behavioural or ecological data, and no foraging mode data. Because chameleons are so unusual, it is not possible to predict where they will fit within the bimodal paradigm. I studied time budget and foraging mode in the Cape dwarf chameleon, Bradypodion pumilum , in Stellenbosch, South Africa. Several approaches were taken to assess foraging behaviour. First, lag-sequential analysis was applied to compare rates behaviours associated with observed eating events, which did not support a sit-and-wait foraging mode. Second, the number of moves per minute (MPM) and per cent time moving (%TM) were compared with those of other lizard taxa from the literature. Foraging in B. pumilum was found to be most consistent with an active foraging mode, although the MPM is unusually low. Thus I propose classification of B. pumilum as a cruise forager. Sufficient data are available to define a discriminant function for active vs. sit-and-wait modes among lizard speries, which classifys B. pumilum as active and additionally lends statistical support for good separation between foraging modes. These findings are discussed in relation to the evolution of foraging modes in chameleons and other lizard families.  © 2005 The Linnean Society of London, Biological Journal of the Linnean Society , 2005, 84 , 797–808.     

Metabolic rate and endurance capacity in Australian varanid lizards (Squamata: Varanidae: Varanus)

In ecomorphological and ecophysiological studies, locomotor performance is often considered to be an intermediate step between the form of an organism and its environment. We examined this premise by measuring morphology, physiology and circular track endurance in the closely related group of Australian varanid lizards. Body size, body mass and relative body proportions were poor indicators of endurance. Body mass was not correlated with endurance and size-free lower forelimb length had only a weak relationship with endurance. Instead, maximal metabolic rate was positively correlated with endurance capacity in varanids. A comparison of varanids with other groups of lizards supported this result as varanids showed both elevated maximal metabolic rate and elevated endurance scores when compared with similar sized non-varanid lizards. There was support for a strong association between endurance with foraging mode and climate. Varanid species with higher endurance tended to be widely foraging and from xeric climates, while sit-and-wait and mesic species showed reduced endurance.   © 2009 The Linnean Society of London, Biological Journal of the Linnean Society , 2009, 97 , 664–676.     

A new species of Prosansanosmilus: implications for the systematic relationships of the family Barbourofelidae new rank (Carnivora, Mammalia)

A new barbourofelid species, Prosansanosmilus eggeri , is described from the Middle Miocene (MN 5) locality of Sandelzhausen, Germany. It differs from all other European barbourofelid species in being smaller and showing a more plesiomorphic morphology, especially in the relatively less developed sabretooth adaptations, low accessory cusps on the premolars, and the remnant of a very small talonid on the carnassial. The species is, however, stratigraphically later than the more apomorphic P. peregrinus, which is known from MN 4 of Germany and France. A phylogenetic analysis based on dental characters of early nimravids, barbourofelids and felids supports previous results on skull morphology of Barbourofelis that Barbourofelinae is not closely related to the Late Eocene and Oligocene Nimravinae. Instead, both subfamilies should be treated as separate families, with the Barbourofelidae closely related to the Felidae. The Barbourofelidae differ from the Felidae as well as from the Nimravidae s.s ., particularly in the unique morphology of their basicranium. They presumably originated in Africa; P. eggeri sp. nov. is interpreted as part of a Miocene immigration of African faunal elements into Europe that took place at the beginning of MN 5. © 2004 The Linnean Society of London, Zoological Journal of the Linnean Society , 2004, 140 , 43−61.     

Aspects of comparative cranial mechanics in the theropod dinosaurs Coelophysis, Allosaurus and Tyrannosaurus

The engineering analysis technique finite element analysis (FEA) is used here to investigate cranial stress and strain during biting and feeding in three phylogenetically disparate theropod taxa: Coelophysis bauri , Allosaurus fragilis and Tyrannosaurus rex . Stress patterns are generally similar in all taxa with the ventral region of the skull tensed whilst the dorsal aspect is compressed, although the skull is not purely behaving as a cantilever beam as there is no discernible neutral region of bending. Despite similarities, stress patterns are not wholly comparable: there are key differences in how certain regions of the skull contain stress, and it is possible to link such differences to cranial morphology. In particular, nasal morphology can be explained by the stress patterns revealed here. Tyrannosaurus models shear and compress mainly in the nasal region, in keeping with the indistinguishably fused and expanded morphology of the nasal bones. Conversely Allosaurus and Coelophysis models experience peak shear and compression in the fronto-parietal region (which is tightly interdigitated and thickened in the case of Allosaurus ) yet in contrast the nasal region is lightly stressed, corresponding to relatively gracile nasals and a frequently patent internasal suture evident in Allosaurus . Such differences represent alternate mechanical specializations between taxa that may be controlled by functional, phylogenetic or mechanical constraints. Creation of finite element models placed in a phylogenetic context permits the investigation of the role of such mechanical character complexes in the cranium of nonavian theropods and the lineage leading towards modern birds.  © 2005 The Linnean Society of London, Zoological Journal of the Linnean Society , 2005, 144 , 309–316.     

Carnivores, biases and Bergmann's rule

Studies of Bergmann's rule may encompass a non-random subsample of extant homeotherms. We examined patterns of correlation between skull length and geographical latitude in 44 species of carnivores in order to test the validity of Bergmann's rule in the Carnivora. Results were then compared to those of other studies. Significant positive correlation between skull length and latitude was found in 50% of carnivore species, while significant negative correlation was found in only 11% of species. These results indicate that the occurrence of Bergmann's rule in the Carnivora is less frequent than earlier published data suggest. Publication bias is not detected in published data. Therefore, previous studies of geographical size variation might be biased in favour of species known to follow Bergmann's rule.  © 2004 The Linnean Society of London, Biological Journal of the Linnean Society , 2004, 81 , 579–588.     

Climatic change and body size in two species of Japanese rodents

Using museum specimens, we studied temporal changes in skull size in two species of Japanese rodents, the large Japanese field mouse ( Apodemus speciosus ) and Pratt's vole ( Eothenomys smithii  =  E. kageus ) during the 20th century. We used the greatest length of the skull (GTL), zygomatic breadth (ZB), narrowest width of the skull across the interorbital region (IC) and the length of the upper cheek teeth row (M) as indicators to such changes. We found that GTL and ZB (but not IC and M) increased during the study period in mice, and that IC and M (but not GTL and ZB) increased marginally in voles. We attribute these changes to elevated ambient minimal temperatures, which increased food availability and energy savings for the mice, and required diet change in the voles.  © 2004 The Linnean Society of London, Biological Journal of the Linnean Society , 2004, 82 , 263–267.     

Predator-prey relationships and the evolution of colour polymorphism: a comparative analysis in diurnal raptors

Genetically based variation in coloration occurs in populations of many organisms belonging to various taxa, including birds, mammals, frogs, molluscs, insects and plants. Colour polymorphism has evolved in raptors more often than in any other group of birds, suggesting that predator–prey relationships was a driving evolutionary force. Individuals displaying a new invading colour morph may enjoy an initial foraging advantage because prey have difficulties in learning the colour of a rare morph (apostatic selection), or because morphs provide alternative foraging benefits allowing differently coloured individuals to exploit distinct food niches (disruptive selection). Plumage polymorphism should therefore have evolved in species that prey upon animals having the physiological ability to distinguish between differently coloured predators but also to flee once a predator has been detected. From this assumption, we can predict that closely related polymorphic and monomorphic species prey upon different animals. They may also differ in morphology, because foraging upon different prey may require different foraging modes, and in turn different morphological structures. We tested these two predictions in a comparative study of raptors. As expected, polymorphic and monomorphic species had a different diet, and there was a difference in wing length between polymorphic and monomorphic species within two genera ( Buteo and Accipiter ). Across all raptors for which phylogenetic relationships are known, polymorphic species preyed more often upon mammals than did monomorphic ones. These two types of raptor did not differ in the frequency of birds, insects and reptiles in their diets. We discuss these results in the light of the hypothesis that predator–prey relationships played a role in the evolution of colour polymorphism. © 2004 The Linnean Society of London, Biological Journal of the Linnean Society , 2004, 81 , 565–578.     

Ambush or active life: foraging mode influences haematocrit levels in snakes

The rate at which organisms acquire resources is a critical trait and foraging mode can vary from sit‐and‐wait tactics to being highly mobile and active. Snakes provide a robust opportunity to examine the physiological correlates of contrasted foraging strategies. In this context, haematocrit (Hct), a proxy of blood oxygen carrying capacity, should be a reliable indicator of aerobic activity levels. We used phylogenetically informed models to examine the relationship between foraging mode and Hct in 80 snake species. After accounting for clade and habitat effects, we found a significant relationship of Hct with foraging mode; Hct is lower in snakes that ambush prey compared to active foragers across habitats. Species using both foraging tactics had marginally lower Hct than active foragers. Ambush foraging tactics are widespread in snakes, notably among low‐energy specialists that usually display low feeding frequency, as well as limited activity and daily movements. Because Hct influences blood viscosity, low levels may thus be advantageous by reducing maintenance and locomotory costs. Further studies are required to better understand the implication of foraging mode on blood characteristics and other aspects of snake physiology. © 2014 The Linnean Society of London, Biological Journal of the Linnean Society, 2014, 111 , 636–645.     

Morphological and ecological convergence in two natricine snakes

Similar morphologies between species may be due to shared ancestry or convergent evolution . Understanding instances of morphological and ecological convergence is central to evolutionary ecology because they help us understand the fit between organism and environment. Two species of stream-dwelling natricine snakes, Thamnophis rufipunctatus and Nerodia harteri present a model system for studying ecological and morphological convergence and adaptation. The species are allopatric and both live in shallow riffles in streams and forage visually for fish. We studied morphological similarity, trait evolution and functional significance of ecologically relevant traits in these and related species, and used mitochondrial DNA sequences for the ND4 gene to estimate their phylogenetic relationships. Character mapping of head length and head width supported the hypothesis of independent evolution of head shape in T .  rufipunctatus and N .  harteri . The elongate snout is a derived trait in these two taxa that is associated with reduced hydrodynamic drag on the snakes' heads when in a swift current, compared to other species with the ancestral blunt snout. We hypothesize that lower hydrodynamic drag facilitates prey capture success in these species that are known to forage by holding their position in currents and striking at fish prey. The elongate snout morphology has also resulted in a diminished binocular vision field in these snakes, contrary to the hypothesis that visually orientated snakes should exhibit relatively greater binocular vision. Convergent evolution of the long snout and reduced hydrodynamic drag in T. rufipunctatus and N. harteri are consistent with the hypothesis that the long snout is an adaptation to foraging in a swift current.  © 2005 The Linnean Society of London, Biological Journal of the Linnean Society , 2005, 85 , 363–371.     

Ecological and evolutionary factors in the morphological diversification of South American spiny rats

Understanding the processes underlying morphological diversification is a central goal in ecology and evolutionary biology and requires the integration of information about phylogenetic divergence and ecological niche diversity. In the present study, we use geometric morphometrics and comparative methods to investigate morphological diversification in Neotropical spiny rats of the family Echimyidae. Morphological diversification is studied as shape variation in the skull, comprising a structure composed of four distinct units: vault, base, orognathofacial complex, and mandible. We demonstrate association among patterns of variation in shape in different cranial units, levels of phylogenetic divergence, and ecological niche diversification. At the lower level of phylogenetic divergence, there is significant and positive concordance between patterns of phylogenetic divergence and cranial shape variation in all cranial units. This concordance may be attributable to the phylogenetic and shape distances being calculated between species that occupy the same niche. At higher phylogenetic levels of divergence and with ecological niche diversity, there is significant concordance between shape variation in all four cranial units and the ecological niches. In particular, the orognathofacial complex revealed the most significant association between shape variation and ecological niche diversity. This association may be explained by the great functional importance of the orognathofacial complex.  © 2009 The Linnean Society of London, Biological Journal of the Linnean Society , 2009, 98 , 646–660.     

Incipient speciation driven by phenotypic plasticity? Evidence from sympatric populations of Arctic charr

Recent models suggest that the existence of environmentally induced polymorphisms within a single population (especially those related to foraging) facilitates the process of evolutionary divergence within a single gene pool by generating distinct phenotypic modes that are exposed to differential selection. In order to test a prediction of the phenotypic plasticity model of divergence, we used a well-documented polymorphism to disentangle the relative effects of morph and rearing environment in generating phenotypic variance. We reared first-generation offspring of two sympatric morphs of Arctic charr Salvelinus alpinus in the laboratory and compared their head morphology with that of their wild parents. Morphological characters with a known functional role in foraging were highly plastic. Rearing environment accounted for the largest component of the variation in expressed phenotype, but this environmental effect overlaid a clear (but small) genetic effect. We conclude that phenotypic plasticity has played a significant role in the evolution of this trophic polymorphism, but that the evolutionary process has progressed to the point that the gene pool is now segregated.  © 2004 The Linnean Society of London, Biological Journal of the Linnean Society , 2004, 81 , 611–618.     

Polyploidy in fishes: patterns and processes

Fishes are the most speciose group of vertebrates, with more than 24 000 species. They are characterized by great diversity in ecology, morphology, life history, behaviour and physiology. Here, the phylogenetic patterns of orders in which polyploidy has been recorded are considered, with special reference to patterns of species richness and hybridization: these orders include such phylogenetically diverse taxa as the Lepidosireniformes (lungfish) and the Perciformes (perch). Examples, predominantly drawn from the Cyprinidae and Salmonidae, are used to illustrate attributes of polyploidy in fishes. It is concluded (i) that polyploidy may have been of considerable importance in the evolution of fishes, and (ii) that fishes, with their diverse life histories, represent a useful model system with which to test theories relating to the origin and consequences of polyploidy that have been derived from work on plants.  © 2004 The Linnean Society of London, Biological Journal of the Linnean Society , 2004, 82 , 431–442.     

Canine morphology in the larger Felidae: implications for feeding ecology

Canine morphology is analysed at seven intervals along the crown in both anteroposterior and lateromedial perspective in seven species of large felids. The puma and the snow leopard have stout, rather conical canines, whereas those of lions, jaguars, and tigers bear substantial resemblance to each other, reflecting their phylogenetic relationships, and are less conical and large. The canines of the leopard are intermediate in morphology between those of the other species, probably reflecting its more generalized diet. The clouded leopard has very large and blade-like canines, which are different from the other analysed species. Canine bending strengths to estimated bite forces appear to differs less among the species than morphology, indicating that the evolution of canines has been constricted with respect to their strength in failure, probably owing to their being equally important for species fitness. However, the clouded leopard again stands out, having a high estimated bite force and rather weak canines in bending about the anteroposterior as well as lateromedial planes compared to the other species. Canine morphology to some extent reflects differences in killing mode, but also appears to be related to the phylogeny. The marked divergence of the clouded leopard is presently not understood.  © 2007 The Linnean Society of London, Biological Journal of the Linnean Society , 2007, 91 , 573–592.     

How phylogeny and foraging ecology drive the level of chemosensory exploration in lizards and snakes

The chemical senses are crucial for squamates (lizards and snakes). The extent to which squamates utilize their chemosensory system, however, varies greatly among taxa and species’ foraging strategies, and played an influential role in squamate evolution. In lizards, ‘Scleroglossa’ evolved a state where species use chemical cues to search for food (active foragers), whereas ‘Iguania’ retained the use of vision to hunt prey (ambush foragers). However, such strict dichotomy is flawed as shifts in foraging modes have occurred in all clades. Here, we attempted to disentangle effects of foraging ecology from phylogenetic trait conservatism as leading cause of the disparity in chemosensory investment among squamates. To do so, we used species’ tongue‐flick rate (TFR) in the absence of ecological relevant chemical stimuli as a proxy for its fundamental level of chemosensory investigation, that is baseline TFR. Based on literature data of nearly 100 species and using phylogenetic comparative methods, we tested whether and how foraging mode and diet affect baseline TFR. Our results show that baseline TFR is higher in active than ambush foragers. Although baseline TFRs appear phylogenetically stable in some lizard taxa, that is a consequence of concordant stability of foraging mode: when foraging mode shifts within taxa, so does baseline TFR. Also, baseline TFR is a good predictor of prey chemical discriminatory ability, as we established a strong positive relationship between baseline TFR and TFR in response to prey. Baseline TFR is unrelated to diet. Essentially, foraging mode, not phylogenetic relatedness, drives convergent evolution of similar levels of squamate chemosensory investigation.     

Parallel evolution in molar outline of murine rodents: the case of the extinct Malpaisomys insularis (Eastern Canary Islands)

The lava mouse Malpaisomys was part of Pleistocene and Holocene faunas of the eastern Canary Islands; it became extinct during historical times. In order to evaluate the evolutionary processes of this endemic species, we set out to identify its relationships with possible mainland relatives. Its dental morphology was compared to a set of fossil and modern murine rodents from various phylogenetic groups, characterized by different diets and dental patterns, using a quantitative method based on a Fourier analysis of the outline of the first upper and lower molars. This morphometric analysis identified different evolutionary grades that are independent of the phylogenetic group. The first cluster is associated with primitive, asymmetric dental outlines, the second with intermediate forms linked to a more herbivorous diet. Highly differentiated forms diverge not only from the second cluster but also from each other. Our investigations reveal Malpaisomys to have had an intermediate dental pattern, a result which confirms previous palaeoecological interpretations of this taxon. However, conclusions about its closest mainland relative remain tentative. Based on a comparison of dental size and shape, as well as geographical considerations, a possible mainland ancestor could be either Paraethomys (North-African Pliocene) or Occitanomys (South-western European Pliocene). Such results support the hypothesis of a Pliocene colonization event, in which case Malpaisomys would display a normal evolutionary rate in dental size and shape, in spite of the insular context. In contrast, a late colonization by a modern representative of the African fauna would imply exceptionally high evolutionary rates compared to the background morphological evolution and a decrease in size that is unlikely under insular conditions.  © 2004 The Linnean Society of London, Zoological Journal of the Linnean Society , 2004, 142 , 555–572.     

Predator–prey interactions in anurans of the tropical dry forests of the Colombian Caribbean: A functional approach

Anuran–prey selection might be mediated by traits, either by mismatches in predator and prey traits (preventing interactions) or by predator selection of prey traits (encouraging interactions). These effect traits could be summarized in two contrasting foraging strategies: “active” and “sit-and-wait” foragers. We evaluated whether anurans could be classified into groups of species sharing traits associated with their diet, and what is the relation between particular effect traits of anurans and their prey. We collected anurans and identified their stomach contents once during dry, minor, and major rain seasons in six dry forest sites in the Colombian Caribbean. For each of the 19 anuran species and 436 prey items, we registered six effect traits. We applied RLQ and fourth-corner methodologies to relate predator and prey traits through their interaction matrix. Predators were assigned to five groups according to their differences in locomotion, body shape, proportion of the jaw width, mode of tongue protrusion, and strata preferred. Regarding preys, species were assigned to four groups according to their gregariousness, body shape and hardness, defensive traits, and mobility. Body size of both, predators and prey, had a minor contribution in the group assignment. We found that predators using active search target low-mobility preys, whereas species using sit-and-wait strategy target highly nutritive prey that are difficult to manipulate. By linking amphibian diet with foraging strategies, we hope to contribute to the understanding of mechanisms behind anuran–prey food web patterns and to build more realistic models of functional response to changing environments.     

Relationships, classification and evolution of Scleranthus (Caryophyllaceae) as inferred from analysis of morphological characters

Study of floral anatomy, micromorphology, palynology and onotogeny has revealed new characters for phylogenetic analysis in the genus Scleranthus . Cladistic analysis of these characters, along with those previously available, suggests that the genus consists of Eurasian/Mediterranean and Australasian sister clades. Gynoecial morphology and development are closely similar in all species, suggesting the genus is monophyletic despite its disjunct northern and southern hemisphere distribution. Variation in pollen:ovule ratios and their implications for the evolution of Scleranthus species are also discussed and it is concluded that a range of breeding strategies intermediate between autogamy and xenogamy exists in the genus. Single-stamened species of Scleranthus are likely to be obligate autogams, despite their comparatively high pollen:ovule ratios in relation to autogamic species of other genera.  © 2002 The Linnean Society of London, Botanical Journal of the Linnean Society , 2002, 140 , 15–29.