Showing papers in "Biological Journal of The Linnean Society in 1998"

Convergent evolution and character correlation in burrowing reptiles: towards a resolution of squamate relationships

Abstract: The affinities of three problematic groups of elongate, burrowing reptiles (amphisbaenians, dibamids and snakes) are reassessed through a phylogenetic analysis of all the major groups of squamates, including the important fossil taxaSineoamphisbaena, mosasauroids andPachyrhachis; 230 phylogenetically informative osteological characters were evaluated in 22 taxa. Snakes (includingPachyrhachis) are anguimorphs, being related firstly to large marine mosasauroids, and secondly to monitor lizards (varanids). Scincids and cordylids are not related to lacertiforms as previously thought, but to anguimorphs. Amphisbaenians and dibamids are closely related, andSineoamphisbaenais the sister group to this clade. The amphisbaenian–dibamid–Sineoamphisbaenaclade, in turn, is related to gekkotans and xantusiids. When the fossil taxa are ignored, snakes, amphisbaenians and dibamids form an apparently well-corroborated clade nested within anguimorphs. However, nearly all of the characters supporting this arrangement are correlated with head-first burrowing (miniaturization, cranial consolidation, body elongation, limb reduction), and invariably co-occur in other tetrapods with similar habits. These characters are potentially very misleading because of their sheer number and because they largely represent reductions or losses. It takes very drastic downweighting of these linked characters to alter tree topology: if fossils are excluded from the analysis, a (probably spurious) clade consisting of elongate, fossorial taxa almost always results. These results underscore the importance of including all relevant taxa in phylogenetic analyses. Inferring squamate phylogeny depends critically on the inclusion of certain (fossil) taxa with combinations of character states that demonstrate convergent evolution of the elongate, fossorial ecomorph in amphisbaenians and dibamids, and in snakes. In the all-taxon analysis, the position of snakes within anguimorphs is more strongly-corroborated than the association of amphisbaenians and dibamids with gekkotans. When the critical fossil taxa are deleted, snakes «attract» the amphisbaenian–dibamid clade on the basis of a suite of correlated characters. While snakes remain anchored in anguimorphs, the amphisbaenian–dibamid clade moves away from gekkotans to join them. Regardless of the varying positions of the three elongate burrowing taxa, the interrelationships between the remaining limbed squamates («lizards») are constant; thus, the heterodox affinities of scincids, cordylids, and xantusiids identified in this analysis appear to be robust. Finally, the position ofPachyrhachisas a basal snake rather than (as recently suggested) a derived snake is supported on both phylogenetic and evolutionary grounds.

Selection for phenotypic plasticity in Rana sylvatica tadpoles

Abstract: The hypothesis that phenotypic plasticity is an adaptation to environmental variation rests on the two assumptions that plasticity improves the performance of individuals that possess it, and that it evolved in response to selection imposed in heterogeneous environments. The first assumption has been upheld by studies showing the beneficial nature of plasticity. The second assumption is difficult to test since it requires knowing about selection acting in the past. However, it can be tested in its general form by asking whether natural selection currently acts to maintain phenotypic plasticity. We adopted this approach in a study of plastic morphological traits in larvae of the wood frog, Raw glvatica. First we reared tadpoles in artificial ponds for 18 days, in either the presence or absence of Anax dragonfly larvae (confined within cages to prevent them from killing the tadpoles). These conditioning treatments produced dramatic differences in size and shape: tadpoles from ponds with predators were smaller and had relatively short bodies and deep tail fins. We estimated selection by Anw on the two kinds of tadpoles by testing for non-random mortality in overnight predation trials. Dragonflies imposed strong selection by preferentially killing individuals with relatively shallow and short tail fins, and narrow tail muscles. The same traits that exhibited the strongest plasticity were under the strongest selection, except that tail muscle width exhibited no plasticity but experienced strong increasing selection. A laboratory competition experiment, testing for selection in the absence of predators, showed that tadpoles with deep tail fins grew relatively slowly. In the cattle tanks, where there were also no free predators, the predator-induced phenotype survived more poorly and developed slowly, but this cost was apparently not associated with particular morphological traits. These results indicate that selection is currently promoting morphological plasticity in R. ylvabica, and support the hypothesis that plasticity represents an adaptation to variable predator environments.

Longterm effects of incubation temperatures on the morphology and locomotor performance of hatchling lizards (Bassiana duperreyi, Scincidae)

Abstract: The phenotypes of hatchling reptiles are known to be aVected by the thermal environments they experience during incubation, but the evolutionary and ecological significance of this phenotypic plasticity remains unclear. Crucial issues include: (i) the magnitude of eVects elicited by thermal regimes in natural nests (as opposed to constant-temperature incubation); (ii) the persistence of these eVects during ontogeny; and (iii) the consistency of these eVects across diVerent test conditions (does the thermal regime during embryogenesis simply shift the hatchling’s thermal optimum for performance, or actually modify overall performance ability regardless of temperature?). We examined these questions by incubating eggs of scincid lizards (Bassiana duperreyi) from montane southeastern Australia, under two fluctuating-temperature regimes that simulated ‘cold’ and ‘hot’ natural nests. These thermal regimes substantially modified hatchling morphology (mass, body length, tail length, and the relationship between these variables), locomotor performance (running speeds over distances of 25cm and 1m), antipredator ‘tactics’ and survival rates. The diVerences in locomotor performance persisted throughout the 20 weeks of our experiment. Lizards that emerged after ‘hot’ incubation were faster runners than their ‘cold’-incubated siblings under all thermal conditions that we tested. Thus, incubation temperatures modified overall locomotor ability, with only a minor eVect on the set-point for optimum performance. The magnitude, persistence and consistency of these incubation-induced phenotypic modifications suggest that they may play an important role in evolutionary and ecological processes within lizard populations.

Coastal forests of eastern Africa: status, endemism patterns and their potential causes

Abstract: Eastern African coastal forests are located within the Swahili regional centre of endemism and Swahili-Maputaland regional transition zone in eastern Africa, between 1° North and 25° South, and 34–41° East. Approximately 3167 km 2 coastal forest remains: 2 km 2 in Somalia, 660 km 2 in Kenya, 697 km 2 in Tanzania, 16 km 2 in Malawi, 3 km 2 in Zimbabwe and perhaps 1790 km 2 in Mozambique. Most forests are small (≤20 km 2 ), and all but 19 are under 30 km 2 in area. Over 80% of coastal forest is located on government land, principally Forest Reserves; only 8.3 km 2 is found in National Parks (6.2 km 2 in Kenya (Arabuko-Sokoke), 2 km 2 in Tanzania (Mafia Island) and tiny patches in Zimbabwe). Coastal forests are an important and highly threatened centre of endemism for plants ( c 550 endemic species), mammals (6 species), birds (9 species), reptiles (26 species), frogs (2 species), butterflies (79 species), snails (>86 species) and millipedes (>>20 species). Endemic species are concentrated in the forests of the Tana River, between Malindi in Kenya to Tanga in northern Tanzania, and in southern Tanzania. Forests with highest numbers of endemics are: lower Tana River, Arabuko-Sokoke, Shimba Hills (Kenya); lowland East Usambara, Pugu Hills, Matumbi Hills, Rondo and Litipo and other plateaux near Lindi (Tanzania); the Tanzanian offshore island of Pemba; Bazaruto archipelago (Mozambique), and tiny forest remnants of southern Malawi, eastern Zimbabwe and Mozambique. Most coastal forest endemics have a narrow distributional range, often exhibiting single-site endemism or with scattered or disjunct distributional patterns. They are best interpreted as relicts and not the result of recent evolution. Relictualization probably started with the separation of the ancient Pan African rainforest into two parts during the Miocene. The coastal forests are interpreted as a «vanishing refuge» with the endemic species gradually becoming more and more relict (and presumably extinct) due historically to climatic desiccation and more recently to human destruction.

Directional asymmetry and the measurement of developmental instability

Abstract: Three widely used methods of estimating fluctuating asymmetry may yield serious overestimates if directional asymmetry is present. When two sides of a bilateral trait grow at different rates, then the asymmetry variance (Var[ l−r ]) increases with size, even when developmental noise is nil. But the residual variance around a population's mean developmental trajectory is invariant with respect to size. Thus, it can be used as a measure of developmental instability. We introduce a measure of developmental instability, the residual variance ( s 2 δ ), obtainable from either a major axis regression, which is equivalent to a principal component analysis on l and r , or a general structural model. This residual variance can be estimated from directionally asymmetric or even antisymmetric traits. We present examples of developmental instability estimated from directionally asymmetric mandibles (house mouse) and leaves (soybean), and antisymmetric claws (fiddler crab).

Phylogenetics and evolution of a circumarctic species complex (Cladocera: Daphnia pulex)

Abstract: The evolutionary history of freshwater zooplankton is still relatively unknown. However, studies of the microcrustacean Daphnia have revealed interesting patterns; the daphniids that dominate ponds and lakes in the northern hemisphere may have recent origins, likely associated with the glacial advances and retreats during the Pleistocene. Moreover, they form species complexes that actively engage in hybridization and introgression. The present study examines the phylogenetic relationships among circumarctic members of the Daphnia pulex complex, through the analysis of sequence diversity in 498 nt of the ND5 mitochondrial gene. Our results suggest that the complex is composed of three major clades, two of which are subdivided into at least eight different lineages. Clearly, species in the complex show genetic discontinuity. Many lineages originated during the Pleistocene, but at least three lineages diverged during the Pliocene. Two taxa (D. pulex, D. pulicaria), thought to be broadly distributed in the northern hemisphere, are shown to be endemic to single continents. In general, the diversification of the pulex complex is characterized by rapidly dispersed lineages spanning enormous distances and also by endemism in temperate areas. Gene flow among lineages from the temperate region of different continents are restricted to rare intercontinental migrations across a polar bridge followed by convergent morphological evolution.

Functional and evolutionary aspects of mouthpart structure in parasitoid wasps

Abstract: This paper considers specializations in mouthpart structure among parasitoid wasps. I commence with a brief survey of mouthpart specializations (mostly involving the mandibles only) that serve functions other than feeding: facilitating emergence of the parasitoid adult from its place of pupation; facilitating grasping of the partner in mating (phoretic copulation); facilitating excavation and/or protecting vulnerable mouthpart components during host searching; facilitating handling of the host; and facilitating nest excavation and construction. I then consider in detail mouthpart specializations for feeding (mostly involving the labiomaxillary complex), and place them in an evolutionary context. Whereas the digitate labrum of Perilampidae and Eucharitidae and the stoutly setose labrum of chrysolampine Pteromalidae are purported to be devices for filtering pollen grains from nectar, I conclude that they are not a feeding-related specialization whatsoever. I recognize seven functional types of mouthpart specialization relating to the extraction of floral nectar from long, narrow, tubular corollas (‘concealed nectar extraction apparatus’ [CNEA]) (Braconidae, Ichneumonidae, Leucospidae, Chrysididae), and postulate a transformation series for them. An eighth type of CNEA possibly occurs in Scoliidae. No such specializations occur in either Orussoidea, Trigonalyoidea, Megalyroidea, parasitoid Evanioidea, Stephanoidea, Cynipoidea, Proctotrupoidea, Ceraphonoidea or parasitoid Aculeata other than Chrysididae and Pompilidae. From examination of published cladograms I conclude that the evolution of CNEA has occurred several times independently within the parasitoid Hymenoptera. So far as Ichneumonoidea are concerned, possession of CNEA is an autapomorphy for taxa at least below subfamily level. Possession of CNEA appears to be a synapomorphy for the family Leucospidae (Chalcidoidea) as a whole, and the same applies to the subfamily Parnopinae (Chrysididae). Hitherto not noted in the literature is the strong degree of evolutionary parallelism, with respect to CNEAs, between the Ichneumonoidea (Ichneumonidae, Braconidae) and the Aculeata (Chrysididae, Pompilidae, Vespidae [Vespinae, Masarinae, Eumeminae], Apidae, non-parasitoid Sphecidae). Also, Apocrita and Symphyta have two types of CNEA in common. Functional comparisons are made between the CNEAs of the parasitoids and those of other Hymenoptera. Compared to parasitoid flies, very few parasitoid wasps possess CNEA. Mouthpart specialization for conveying a nuptial gift of nectar or honeydew to the female occurs in the males of thynnine Tiphidae, while in the females of regurgitation feeders there is a trend towards reduction in labiomaxillary components, constituting a specialization for receiving and processing the gift. Mouthpart specialization for pollen feeding occurs in Mutillidae and Scoliidae. No mouthpart specialization for host feeding occurs in any parasitoid wasps, in contrast to parasitoid flies, despite host feeding being more common among the former. Sexual dimorphism in feeding-related mouthpart specializations is rare among parasitoid wasps; where it occurs, both sexes share the same type of CNEA, and the dimorphism is attributable to allometry.

Phylogenetic analyses of primate size evolution: the consequences of sexual selection

Abstract: We have analysed the relationship between primate mating system, size and size dimorphism by utilizing several phylogenetically based methods. An independent contrast analysis of male and female size (log weight) showed that these are tightly correlated and that size dimorphism is not a simple allometric function of size. We found no relationship between mating system and sexual dimorphism in strepsirhines but a strong relationship in haplorhines. By matched-pairs analysis, where sister groups were matched according to whether the mating system predicted higher or lower intrasexual selection for male size, haplorhine species in more polygynous clades (with a predicted higher sexual selection) were significantly more dimorphic, had larger males, and also, but to a lesser degree, larger females. Both independent contrast and matched-pairs analyses are non-directional and correlational. By using a directional test we investigated how a transition in mating system affects size and dimorphism. Here, each observation is the sum of changes in dimorphism or size in a clade that is defined by a common origin of a mating system. Generally, dimorphism, as well as male and female size, increased after an expected increase in sexual selection, and decreased after an expected decrease in sexual selection. The pattern was, however, not significant for all of the alternative character reconstructions. In clades with an expected increase in sexual selection, male size increased more than female size. This pattern was significant for all character reconstructions. The directional investigation indicates that the magnitude of change in haplorhine dimorphism is larger after an increase in sexual selection than after a decrease, and, for some reconstructions, that the magnitude of size increase is larger than the magnitude of size decrease for both sexes. Possible reasons for these patterns are discussed, as well as their implications as being one possible mechanism behind Cope's rule, i.e. general size increase in many phylogenetic lineages.

Molecular phylogeny of elapid snakes and a consideration of their biogeographic history

Abstract: Evolutionary relationships among the major elapid clades, particularly the taxonomic position of the partially aquatic sea kraits (Laticauda) and the fully aquatic true sea snakes have been the subject of much debate. To discriminate among existing phylogenetic and biogeographic hypotheses, portions of both the 16S rRNA and cytochrome b mitochondrial DNA genes were sequenced from 16 genera and 17 species representing all major elapid snake clades from throughout the world and two non-elapid outgroups. This sequence data yielded 181 informative sites under parsimony. Parsimony analyses of the separate data sets produced trees of broad agreement although less well supported than the single most parsimonious tree resulting from the combined analyses. These results support the following hypotheses: (1) the Afro-Asian cobra radiation forms one or more sister groups to other elapids, (2) American and Asian coral snakes form a clade, corroborating morphological studies, (3) Bungarus forms a sister group to the hydrophiines comprised of Laticauda, terrestrial AustraloPapuan elapids and true sea snakes, (4) Laticauda and true sea snakes do not form a monophyletic group but instead each group shares an independent history with terrestrial Australo-Papuan elapids, corroborating previous studies, (5) a lineage of Melanesian elapids forms the sister group to Laticauda, terrestrial Australian species and true sea snakes. In agreement with previous morphologically based studies, the sequence data suggests that Bungarus and Laticauda represent transitional clades between the elapine ‘palatine erectors’ and hydrophiine ‘palatine draggers’. Both intra and inter-clade genetic distances are considerable, implying that each of the major radiations have had long independent histories. I suggest an African, Asian, or Afro-Asian origin for elapids as a group, with independent Asian origins for American coral snakes and the hydrophiines.

In search of historical biogeographic patterns in the western Mediterranean terrestrial fauna

Abstract: A cladistic biogeographic study of the western Mediterranean terrestrial fauna is made using taxon-area cladograms of ten groups of animals showing high levels of endemicity in the area. The groups analysed are theNephrotoma flavescensgroup, theTipula(Acutipula)maximagroup, theT. (Lunatipula)bullataandfalcatagroup, the subgenusT. (Mediotipula), theT. (Savtshenkia)goriziensisgroup, theT. (S.)signatagroup (Insecta, Diptera, Tipulidae), theProtonemura corsicanagroup (Insecta, Plecoptera, Nemouridae), the genusSpeonemadus(Insecta, Coleoptera, Cholevidae), and the subgeneraTriturus(Palaeotriton) andTriturus(Triturus) (Urodela, Salamandridae). The groups contain a total of 123 species and subspecies. Detailed distribution maps of 94 species and subspecies of Tipulidae included in the study are given. Based on the distributions of 74 endemic species and subspecies, 13 areas of endemism in the Mediterranean are recognized. The geology of the western Mediterranean since the late Oligocene is discussed with reference to a number of maps showing kinematic reconstructions of the area. Five methods for cladistic biogeographic purposes were employed, viz. Brooks Parsimony Analysis, Component Compatibility Analysis, Component Analysis, Three-Area Statements Analysis, and Paralogy-free Subtree Analysis. General area cladograms produced by computer implementations of the five methods show low levels of congruence. Geological area cladograms are fully compatible with some of the results of Brooks Parsimony Analysis only.

Sympatric cryptic species in New Zealand Onychophora

Abstract: AUozyme electrophoresis was used to examine genetic diversity within live-bearing Penpatopsid Onychophora from the North Island of New Zealand. Specimens of two previously described morpho-species that differ in leg number (Pnipatoides sub' and l? novaezeakmdke) were found to be genetically diverse. l? sub' showed little intraspecific genetic variation but were very distinct from specimens assignable to l? nomzealandiae. Within l? novaeZealandke five genetically differentiated species were identified although none showed any consistent morphological differentiation, thus l? novuezeulundke (Hutton) is a species complex. AU of these species occur in sympatry or parapatry (in one instance) with other cryptic species of the l? novaeZealundke group or with l? suteri. Four new species are described on the basis of this genetic evidence, they are I? morgani, I? aurorbis, I? kawekasnsis and I? sympah.ica. Other genotypes encountered indicate further cryptic species remain unrecognized. Among the North Island species, l? sub' and I? aurorbis sp. nov. are both more closely related to undescribed species from the South Island than to others examined from the North Island. I? sympatrica sp. nov. exists in sympatry with at least three other species in different parts of its range. The complexity of relationships and distributions probably arose through the interaction of low vagility in peripatus and the active geophysical history of the region. How these cryptic species persist in sympatry is not known but may be linked to differences in ecology not evident in their morphology, and/or may indicate recent dispersal from allopatry.

Factors affecting food comminution during chewing in ruminants: a review

Abstract: A review is presented of the chewing effectiveness of herbivorous mammals dealing with the relationship between food comminution (ie reduction of particle size), morphological features of teeth, chewing behaviour (ie time spent chewing and chewing rate), and the chemical and physical properties of plant tissues Chewing is the main food processing mechanism in herbivores, increasing the surface/volume ratio of the food, which is a key factor affecting the efficiency of digestion and, therefore, body condition, reproductive success and life history Chewing effectiveness (CE) is defined as the reduction of a pre-determined amount and particle size of a given food after a known, but not necessarily determined, number of chews The two main animal-centred factors influencing CE are tooth effectiveness and chewing behaviour The most frequently used predictors of tooth effectiveness are molar occlusal surface area, molar occlusal contact area (defined as any surface of the upper and lower teeth in or near contact during occlusion) and the length of the enamel cutting edges of the occlusal surface There is expected to be a direct positive relationship between the predictors of tooth effectiveness and chewing effectiveness Chewing behaviour has particular importance to food particle reduction in ruminants, because they spend long periods chewing during both initial ingestion and ruminating The majority of studies find significant unexplained variance when CE is predicted using tooth features or chewing behaviour parameters There is also little agreement as to what is the key morphological factor determining tooth effectiveness, or what is the relationship between tooth effectiveness and chewing behaviour The type, maturity stage and physical presentation of the food also contribute to the final particle size after food has been chewed, because of the involvement of the concentration of chemical components of the cell walls (acid detergent and neutral detergent fibres, lignin) and the architectural structure of the plant tissues in particle breakdown The relationships between body mass and tooth effectiveness, chewing behaviour and CE are also discussed

The timing of insect/plant diversification: might Tetraopes (Coleoptera: Cerambycidae) and Asclepias (Asclepiadaceae) have co-evolved?

Abstract: Ehrlich and Raven's essay on coevolution has stimulated voluminous work on the mechanisms of insect/plant interaction, but few explicit tests of their model's prediction that the evolutionary success of entire insect and plant clades is governed by their putative reciprocal adaptations. This paper begins an inquiry into possible coevolutionary diversification for North American milkweeds of the genusAsclepiasand one of their few major herbivores, the longhorn beetle genusTetraopes, focusing first on the historical duration and continuity of the interaction. A phylogeny forTetraopesand relatives, estimated from morphology and allozymes, shows evident similarity to a morphology based hostplant cladogram synthesized from the literature, though the significance of the correspondence under heuristic statistical tests depends on the treatment of one beetle species reported (without certainty) from multiple host species. Fossils and biogeography support the interpretation that cladogram correspondence reflects synchronous diversification of these two clades, hence opportunity for coevolution, rather than beetle «host-tracking» of previously-diversified plants. Cladogram correspondence is more evident at higher than at lower levels, as expected under Ehrlich and Raven's model. An apparent phylogenetic progression in the potency and location of milkweed cardenolides, seemingly related to species diversity of bothAsclepiasandTetraopessubclades, provides further suggestive evidence for that model. The phylogeography of theTetraopes/Asclepiasassemblage suggests that extant species evolved largely in their current, often quite localized biomes, facilitating potential experimental tests for hypotheses of adaptation and counteradaptation and their importance to diversification.

Local spatial autocorrelation in biological variables

Abstract: Spatial autocorrelation (SA) methods have recently been extended to include the detection of local spatial autocorrelation at individual sampling stations. We review the formulas for these statistics and report on the results of an extensive population-genetic simulation study we have published elsewhere to test the applicability of these methods in spatially distributed biological data. We find that most biological variables exhibit global SA, and that in such cases the methods proposed for testing the significance of local SA coefficients reject the null hypothesis excessively. When global SA is absent, permutational methods for testing significance yield reliable results. Although standard errors have been published for the local SA coefficients, their employment using an asymptotically normal approach leads to unreliable results; permutational methods are preferred. In addition to significance tests of suspected non-stationary localities, we can use these methods in an exploratory manner to find and identify hotspots (places with positive local SA) and coldspots (negative local SA) in a dataset. We illustrate the application of these methods in three biological examples from plant population biology, ecology and population genetics. The examples range from the study of single variables to the joint analysis of several variables and can lead to successful demographic and evolutionary inferences about the populations studied.

Origin of hummingbird faunas

Abstract: Ecological studies of hummingbird communities have emphasized the importance of local conditions and contemporary interactions in the development of these varied faunas. A time-calibrated, DNA hybridization-based phylogeny of the principal hummingbird lineages was used to examine historical aspects of hummingbird faunas in the species-rich tropical lowlands and Andes, and the relatively depauperate West Indies and temperate regions of Central and North America. Parsimony reconstructions of ancestral distributions indicate that these faunas are polyphyletic in origin, comprising several to many independent lineages. Based on the timing of geologic and cladogenic events, hummingbird faunas appear to have arisen more often by colonization than by large-scale vicariance, with multiple dispersals across water gaps, elevational gradients, and latitude. The extent to which particular lineages colonized different regions depended, however, on lineage ecology as well as on the habitat and age of the fauna. In general, the oldest extant trochilofauna, which today occupies the tropical lowlands, was the principal source of colonizing taxa. However, all regions except possibly the West Indies contributed taxa now found elsewhere, including in the tropical lowlands. The Andean fauna comprises several lineages with lowland origin (hermits, Mangoes, Brilliants, Coquettes, Emeralds) as well as at least one that arose in temperate regions outside South America (Bees). At least two lineages that colonized the West Indies gave rise to endemic genera (Mangoes to Eulampis , and Emeralds to Orthorhyncus ). Even groups that diversified in the highlands (Brilliants and Bees) gave rise to taxa that subsequently reinvaded the tropical lowlands. As the result of these varied histories, hummingbird communities cannot be arranged easily with respect to organizational complexity and coevolution with nectar sources. Although the physically insular faunas in the Andes and West Indies differ markedly in diversity, both were more strongly affected by colonization than the other faunas. A high potential for coevolution between hummingbirds and plants probably facilitated the successful establishment and radiation of the several Andean-associated lineages. However, coexistence between the two most diverse Andean clades may have been favoured initially through different habitat preferences by their extra-Andean ancestors. In the tropical lowlands, by comparison, the basic separation between the forest-dwelling hermits and canopy and edge-dwelling nonhermits appears to have evolved in situ. The low species and morphologic diversity of hummingbirds breeding north of Mexico reflects the predominance there of a single relatively recent lineage. The regional coexistence of numerous unrelated lineages implies that patterns of ancestry, colonization, and extinction contribute to the make-up of contemporary species-rich hummingbird faunas and serves to qualify the view that hummingbird communities are coadapted assemblages that resist change.

Crustacean disparity through the Phanerozoic: comparing morphological and stratigraphic data

Abstract: Crustaceans have been an important component of marine diversity and biomass since the earliest Phanerozoic. With a relatively well-documented fossil record, they provide an excellent subject for a continuous study of disparity (approxiamtely bodyplan variety) from the Cambrian to the Recent. A data base of 135 morphological characters forms the basis for cladistic and morphospace studies at the ordinal and sub-ordinal level. Gross cladistic topology is: (Eumalacostraca+Hoplocarida vs Maxillopoda) vs Phyllopoda (paraphyletic). Each of these groups is of approximately equal disparity, and occupies a distinct region of the morphospace plot. A few problematical fossils (e.g. Waptia and Odaraia ) fall close to the base of the tree. Comparison of the cladogram with stratigraphic range data indicates the location of probable ghost lineages, and randomization procedures provide a statistical test of the goodness of fit of a given set of stratigraphic ranges to a given tree topology. Disparity indices are calculated at series and stage intervals. Observed range data indicate that Cambrian disparity was approximately one third its present level. The Earliest Ordovician saw a marked decrease, with an increase and subsequent plateau through rest of the period. Increases through the Silurian and Devonian corresponded to the radiation of branchiopods, cephalocarids, and latterly the Eumalacostraca and Hoplocarida. By the end of the Carboniferous, observed disparity had reached over four fifths of Recent levels, and the remaining history of the group saw a gradual but slightly irregular increase up until the end of the Tertiary. Indices of disparity incorporating ghost lineages exhibit less marked peaks and troughs, with fewer perturbations overall. Cladistically-implied disparity in the Lower Cambrian is estimated at three quarters of that in the Recent. Rarefaction is used to compare actual levels of disparity at each time interval with the mean for a similar number of taxa selected randomly from the list of all realized bodyplans. Most intervals preserved a range of forms more disparate than the mean of random samples drawn from the pool of all the taxa considered. From the Triassic to the Recent this difference was intermittently significant. Once occupied, extremes of morphospace tend not to fall vacant again.

Functional, evolutionary and ecological aspects of feeding-related mouthpart specializations in parasitoid flies

Abstract: This paper considers mouthpart specializations for feeding among dipteran parasitoids, and places them in both an evolutionary and an ecological context. Parasitoid flies display specializations in relation to feeding on solidified honeydew, removing floral nectar from long, narrow, tubular corollas, and feeding on host materials. No species have as yet been identified which display particular specializations for pollen-feeding, but we consider it likely that they exist. Marked sexual dimorphism in mouthpart structure appears to occur only in the Phoridae. Mapping the occurrence of apparatus for removing floral nectar from long, narrow, tubular corollas (‘concealed nectar extraction apparatus’ or CNEA) onto published cladograms for Diptera shows that the evolution of such feeding apparatus has occurred many times independently. In contrast to parasitoid Hymenoptera, possession of CNEA is more often an autapomorphy for taxa above subfamily level in apparently two cases for superfamilies (Acroceroidea and Nemestrinoidea). We conclude that whereas in parasitoid wasps the pattern of occurrence of CNEA is mainly attributable to ecological expediency, in parasitoid flies phylogenetic history has also played a major role. We discuss the fitness advantages of the diVerent feeding specializations among parasitoids generally (i.e. both Diptera and Hymenoptera) in relation to various ecophysiological factors.

Biogeography of seeder and resprouter Erica species in the Cape Floristic Region—Where are the resprouters?

Abstract: The genus Erica L., with more than 600 species, and a high number of endemics, represents the most remarkable example of floristic diversity in the Cape Floristic Region (CFR). It is largely confined to nutrient-poor, acidic, sandy soils, being one of the most characteristic element of fynbos. The ability to survive fires, resprouting from a lignotuber, is a common trait among Euro-mediterranean Erica species. In contrast, resprouting is fairly uncommon among ericas in the CFR (less than 10%). Most of them are killed by fire, regenerating only but readily by seed germination. An extensive survey on the resprouting ability of South African Erica species was carried out and the pattern of geographical distribution of resprouters and seeders in the CFR was determined. The geographical distribution of these two regeneration classes was related to a climatic gradient of seasonality along the CFR. A pattern of higher proportions of resprouter species towards the mediterranean, strongly seasonal northwestern CFR and the non-seasonal eastern CFR and summer rainfall area outside the CFR was identified. The number of resprouter species reaches a maximum in the eastern CFR and is lower in the southwestern CFR despite the overall higher concentration of species in this subregion. Summer drought strongly influences the effectiveness of post-fire regeneration and growth (i.e. new recruits plus survivors) of Erica species, and is the major selective force accounting for the pattern of distribution of seeders and resprouters in the CFR. A mild mediterranean climate with reliable autumn-winter rains and a short summer drought, typical of the mountain areas of the southwestern CFR, favours recruitment of seeders but hampers recruitment of resprouters. Resprouter species persist and become dominant under harsh conditions for recruitment (severe summer drought) and would coexist with seeders under situations of no summer stress. Diversification is associated with seeder lineages. Hence, number of seeder species will be higher than number of resprouters, especially in the southwestern CFR, where favourable conditions for recruitment allow a massive concentration of seeder species, many of them narrow endemics.

Optimal outgroup analysis

Abstract: We present and critically examine a statistical criterion for the selection of outgroup taxa for rooting evolutionary trees. The criterion is the amount of phylogenetic signal for the ingroup when the states of the candidate outgroup taxa are assumed to be plesiomorphic relative to the ingroup for the purpose of measuring plesiomorphy content of the outgroup taxon. A statistical measure of rooted, ingroup signal was subjected to a suite of critical tests which indicate that it provides a proxy measure of plesiomorphy content. As the evolutionary distance between the ingroup ancestral node and outgroup taxa increases, the tree-independent measure of signal decreases, tracking the decay in plesiomorphy content and the increase in convergence to the ingroup states. We show thata priorigeneralizations about optimal outgroup taxon sampling strategies are likely to be misleading, and that testing for the suitability of available outgroup taxon sampling in specific instances is warranted. Software for optimal outgroup analysis is available.

Patterns of sex ratio, virginity and developmental mortality in gregarious parasitoids☆

Abstract: Theory considering sex ratio optima under ‘strict local mate competition with offspring groups produced by a single foundress’ makes a suite of predictions, one of which is a mean female bias. Treating individual offspring as discrete units, theory further predicts sex ratios to have low variance (precise sex ratio) and to equal the reciprocal of clutch size (one male per clutch). The maternal decision may be complicated by imperfect control of sex allocation, limited insemination capacity of sons and offspring developmental mortality: each can lead to virgin daughters (with zero fitness) and consequently select for less biased sex ratios. When clutches are small and/or developmental mortality is common, appreciable proportions of virgins are expected, even when control of sex allocation is perfect and the mating capacity of males is unlimited. This suite of predictions has been only partially tested. We provide further tests by examining sex ratios and developmental mortalities within and across species of locally mating parasitoids. We find a wide range of mean developmental mortalities (6–67%), but mortality distributions are consistendy overdispersed (have greater than binomial variance) and sexually differential mortality appears to be absent. Sex ratios are female biased and have low variance, but are not perfectly precise and variance is increased by mortality within species and (equivocally) across species. Sex ratios less biased than the reciprocal of clutch size are observed; probably due to a maternal response to developmental mortality in one species, and to limited insemination capacity in others. Cross species comparisons indicate that mean proportions of mortality and virginity are positively correlated. Virginity is more prevalent than predicted among species with higher mortalities but not among lower mortality species. Predicted relationships between virginity and clutch size are supported in species with lower mortalities but only partially supported when mortality rates are higher.

Supraspecific taxa as terminals in cladistic analysis: implicit assumptions of monophyly and a comparison of methods

Abstract: The use of supraspecific terminal taxa to represent groups of species in phylogenetic analyses can result in changes to inferred relationships as compared to a complete species level analysis. These changes in topology result from interactions among (1) the cladistic status of the supraspecific taxa; (2) the method used to represent the taxa as single terminals, and (3) incongruence in the data set. We examine the effects of using supraspecific terminal taxa using a parallel analysis of hypothetical examples and an actual data matrix for the true seals (Mammalia: Phocidae). Incongruence among characters can produce changes in topology by shifting the «balance of power» among groups of characters when supraspecific taxa are represented as single terminals. In the absence of homoplasy, the correct topology is maintained. Of the three methods for representing supraspecific taxa, the «ancestral» method, which explicitly infers the common ancestor of the group corresponding to the taxon, performed the best, always maintaining the correct topology when monophyletic taxa were represented. This agrees with theoretical predictions. The «democratic» and «exemplar» methods, which represent the higher level taxon through a survey of all or one of its extant constituent species, respectively, were not as effective in maintaining the correct topology. Although both occasionally provided correct answers, their occurrences were largely unpredictable. The success of the exemplar method varies with the species selected. The simultaneous representation of two or more higher level taxa produced interactive effects where the resultant topology included different clades than when the taxa were collapsed individually. Interactive effects occurred with all three methods, albeit to a lesser degree for the ancestral method. Changes in topology were observed regardless of whether the higher group was monophyletic or not, but were more prevalent when it was paraphyletic. Unfortunately, there does not seem to be a reliable way to determine when a paraphyletic group has been included in the analysis (e.g. through bootstrap values or indices measuring homoplasy). The implications of these findings for phylogenetic analyses of molecular data are also discussed.

Variation in morphology, gait characteristics and speed of locomotion in two populations of lizards

Abstract: Locomotor behaviour varies between two subspecies of the Spanish wall lizard Podarcis hispanica. One subspecies inhabits the Columbretes islands, the other lives on the Spanish mainland. Size standardized voluntary speeds (as measured in unrestrained laboratory conditions) are lower in the island population (P. h. atrata) than in the mainland population (P. h. hispanica). Maximal running performance (when chased) is much higher in the mainland population than in the island population. High speed video recordings show that subspecies diVer in gait characteristics: individuals from the mainland modulate running velocity primarily by modifying stride length, individuals from the island primarily by altering stride frequency. P. h. hispanica’s strategy for modulating speed probably allows this mainland subspecies to attain higher maximal speeds than the island subspecies P. h. atrata. Theoretical considerations suggest that at high speeds, P. h. hispanica’s running style is energetically more favourable, but this hypothesis awaits experimental verification. We suggest that the diVerences in locomotion eYciency between the subspecies result from diVerences in predation pressure between the mainland and the island. The mainland study site has a higher predator diversity and oVers less hiding opportunities to the lizards.

Geographic variation in lizard phenotypes: importance of the incubation environment

Abstract: Geographic variation in phenotypes can result from proximate environmental eVects as well as from underlying genetic factors. Reciprocal transplant experiments, in which organisms are moved from one area to another, oVer a powerful technique to partition the eVects of these two factors. However, many studies that have utilized this technique have focused on the post-hatching organism only and ignored potential eVects of environmental influences acting during embryonic development. We examined the phenotypic responses of hatchling scincid lizards (Lampropholis guichenoti) incubated in the laboratory under thermal regimes characteristic of natural nests in two study areas in southeastern Australia. Although the sites were less than 120 km apart, lizards from these two areas diVered in thermal regimes of natural nests, and in hatchling phenotypes (morphology, locomotor performance). We incubated eggs from each area under the thermal regimes typical of both sites. Some of the traits we measured (e.g. hatchling mass and snout-vent length) showed little or no phenotypic plasticity in response to diVerences in incubation conditions, whereas other traits (e.g. incubation period, tail length, inter-limb length, body shape, locomotor performance) were strongly influenced by the thermal regime experienced by the embryo. Thus, a significant proportion of the geographic variation in morphology and locomotor performance of hatchling lizards may be directly induced by diVerences in nest temperatures rather than by genetic divergence. We suggest that future studies using the reciprocal transplant design should consider environmental influences on all stages of the life-history, including embryonic development as well as post-hatching life.

Biogeographic disjunction along the Alpine fault, New Zealand

Abstract: Eighty taxa (subspecies, species, species groups, genera and families) showing disjunction along the New Zealand Alpine fault (Australian/Pacific plate boundary) are documented and mapped. Four plant divisions, including 14 seed plant families, and four animal phyla, including 13 orders of insects, are represented. The disjunction has usually been explained by glaciers having wiped out central populations. However, the gap is often occupied by a related taxon and many alpine taxa are involved, and so extinction by glaciation seems unlikely as an explanation. It is proposed that the disjunction has been caused by the 480 km of lateral displacement on the fault.

Variability in mammalian dentitions: size-related bias in the coefficient of variation

Abstract: The coefficient of variation has been used in many evolutionary studies. However, a strong negative correlation between this index and size may artificially inflate the apparent variability of small traits. This is most pronounced when variables whose size differs by more than an order of magnitude are compared or when the index is applied to variables whose size is within an order of magnitude of their measurement error. When this is likely to affect conclusions, other indexes of variability should be considered. One alternative is to use the standard deviation of log-transformed data; however, this index is sometimes still correlated with variable size so care should be exercised in its use. Another alternative is to regress the standard deviation onto mean variable size; however, this method may also be misleading if variables are not randomly distributed about the regression line. As an example of the effect of bias in the coefficient of variation, previous studies of mammalian dental variability profiles were re-evaluated. It was found that variation among teeth is relatively homogenous, both within and among species. The exception is that the canines of some mammalian species have variability that is considerably higher than would be expected from tooth size. Previous explanations of variability patterns that invoked developmental fields are incompatible with the new data.

Multiple paternity in the common frog (Rana temporaria): genetic evidence from tadpole kin groups

Abstract: Very few studies have investigated the occurrence of multiple paternity and sperm competition in amphibians. We studied genetic relatedness within kin groups of tadpoles of an aquatically breeding anuranRana temporariausing allozymes. We collected samples from 52 naturally fertilized spawn clumps produced by single females at three breeding sites in two populations. We estimated relatedness (r) within kin groups, and compared the observed genotype distributions of the tadpoles (on average 23 individuals in each group) with the expected distributions based on single mating. Average relatedness over five polymorphic loci was 0.44 and 0.43 in the two populations, the latter being significantly smaller than that expected by single mating (0.5). The number of patrilines, calculated from relatedness estimates, was 1.3 in one population and 1.4 in the other. Genotype distributions deviated significantly from the expected in half of the kin groups and at all breeding sites. The results show that egg clutches ofR. temporariacommonly contain multiply sired offspring. We suggest that communal breeding may affect paternity patterns inR. temporariaas well as in anurans in general.

Trophic polymorphism, habitat and diet segregation in Percichthys trucha (Pisces: Percichthyidae) in the Andes

Abstract: Divergent natural selection affecting specific trait combinations that lead to greater efficiency in resource exploitation is believed to be a major mechanism leading to trophic polymorphism and adaptive radiation. We present evidence of trophic polymorphism involving two benthic morphs within Percichthys trucha , a fish endemic to temperate South America. In a series of lakes located in the southern Andes, we found two morphs of P. trucha that could be distinguished on the basis of gill raker length and five other morphological measures, most of which are likely associated with the use of food resources. The differences were consistent across all lakes examined, and were correlated with habitat use and diet. Individuals with longer gill rakers were more abundant in the littoral zone (littoral morph) while the short gill-raker morph was more abundant at 10 m depth and deeper (deep benthic morph). Both morphs fed primarily on benthic invertebrates, but the littoral morph fed more on larval Anisoptera than did the deep benthic morph. Phenotypic correlations among traits were high for the littoral morph, but low and non-significant for the deep-benthic morph. We suggest that gill raker length may influence the relative efficiency of suction feeding for the two morphs. This is the first evidence of trophic polymorphism in fishes from temperate South America.

An intraspecific analysis of trade-offs in sprinting performance in a West Indian lizard species (Anolis lineatopus)

Abstract: We examined whether a trade-off exists in sprinting ability among individuals within the Caribbean lizardAnolis lineatopus. Specifically, we made the following predictions: Longer-legged (relative to body size) individual lizards should sprint faster than shorter-legged lizards on a broad (5.1 cm diameter) rod. However, longer-legged lizards should also decline in sprinting performance to a greater extent than shorter-legged lizards when sprinting on rods of different diameters. To test these predictions, we examined morphology and sprinting performance in adult male, adult female and juvenileA. lineatopus. As predicted, longer-legged lizards are faster sprinters than shorter-legged lizards on the broad substrate, but they also decline more in speed between the broad and narrow (0.7 cm diameter) dowel. However, despite statistically significant morphological differences among intraspecific classes, differences in morphology did not result in differences in sprinting performance among intraspecific classes, with the exception that larger lizards run faster than smaller lizards on each dowel size.

Pollen-size comparisons among animal-pollinated angiosperms with different pollination characteristics

Abstract: Pollen volume varies among angiosperm species over five orders of magnitude, presumably because the functional advantages of pollen size depend on each species» particular pollination and fertilization conditions. This paper reports two studies that assess whether animal-pollinated species with different pollination systems differ correspondingly in pollen size, as would be expected if pollen size affected pollen transport. Analysis of ninePedicularisspecies detected significant interspecific variation in pollen size; however, the overall mean pollen volume of species pollinated primarily by nectar-collecting bees did not differ significantly from that of species pollinated by pollen-collecting bees. Similarly, comparison of bee- and bird-pollinated congeners in 16 genera (nine families) from Australia and North America found considerable variation in pollen diameter within and between genera, but this variation was not associated consistently with differences in primary pollinator type (bee>bird for three genera, bee≈bird for five genera, bee