Limited, episodic diversification and contrasting phylogeography in a New Zealand cicada radiation

ABSTRACT: BACKGROUND: The New Zealand (NZ) cicada fauna contains two co-distributed lineages that independently colonized the isolated continental fragment in the Miocene. One extensively studied lineage includes 90% of the extant species (Kikihia + Maoricicada + Rhodopsalta; ca 51 spp.), while the other contains just four extant species (Amphipsalta -- 3 spp. + Notopsalta -- 1 sp.) and has been little studied. We examined mitochondrial and nuclear-gene phylogenies and phylogeography, Bayesian relaxed-clock divergence timing (incorporating literature-based uncertainty of molecular clock estimates) and ecological niche models of the species from the smaller radiation. RESULTS: Mitochondrial and nuclear-gene trees supported the monophyly of Amphipsalta. Most interspecific diversification within Amphipsalta-Notopsalta occurred from the mid-Miocene to the Pliocene. However, interspecific divergence time estimates had large confidence intervals and were highly dependent on the assumed tree prior, and comparisons of uncorrected and patristic distances suggested difficulty in estimation of branch lengths. In contrast, intraspecific divergence times varied little across analyses, and all appear to have occurred during the Pleistocene. Two large-bodied forest taxa (A. cingulata, A. zelandica) showed minimal phylogeographic structure, with intraspecific diversification dating to ca. 0.16 and 0.37 Ma, respectively. Mid-Pleistocene-age phylogeographic structure was found within two smaller-bodied species (A. strepitans -- 1.16 Ma, N. sericea -- 1.36 Ma] inhabiting dry open habitats. Branches separating independently evolving species were long compared to intraspecific branches. Ecological niche models hindcast to the Last Glacial Maximum (LGM) matched expectations from the genetic datasets for A. zelandica and A. strepitans, suggesting that the range of A. zelandica was greatly reduced while A. strepitans refugia were more extensive. However, no LGM habitat could be reconstructed for A. cingulata and N. sericea, suggesting survival in microhabitats not detectable with our downscaled climate data. CONCLUSIONS: Unlike the large and continuous diversification exhibited by the Kikihia-Maoricicada-Rhodopsalta clade, the contemporaneous Amphipsalta-Notopsalta lineage contains four comparatively old (early branching) species that show only recent diversification. This indicates either a long period of stasis with no speciation, or one or more bouts of extinction that have pruned the radiation. Within Amphipsalta-Notopsalta, greater population structure is found in dry-open-habitat species versus forest specialists. We attribute this difference to the fact that NZ lowland forests were repeatedly reduced in extent during glacial periods, while steep, open habitats likely became more available during late Pleistocene uplift.     

Patterns of diversification in New Zealand Stylidiaceae

Phylogenetic analysis of ITS and rbcL sequences show that New Zealand Stylidiaceae fall into two distinct lineages differing in species richness. Each lineage represents a unique dispersal event to New Zealand occurring at different times during the evolutionary history of the family. One lineage comprises seven species of Forstera and Phyllachne, while the other consists solely of Oreostylidium subulatum. The origin of the Forstera/Phyllachne lineage in New Zealand is equivocal; either a South American or a Tasmanian origin is equally parsimonious. Possible sister groups are F. bellidifolia in Tasmania and P. uliginosa in South America. Oreostylidium subulatum has an Australian origin. In our analyses O. subulatum is nested in a clade composed entirely of species of Stylidium, almost all of which are endemic to Australia. Species of Phyllachne share a cushion habit with the outgroup Donatia (Donatiaceae) that may have preadapted them to alpine environments in New Zealand. The New Zealand Stylidiaceae have small, white, actinomorphic flowers that are well adapted to the unspecialized pollinator fauna. Forstera and Phyllachne share this trait with Donatia; however, the small, white flowers of Oreostylidium are a dramatic departure from the colorful, highly specialized flowers of Stylidium.     

Sound radiation in a cicada: the role of different structures

Sound radiation was studied in males of Tympanistalna gastrica St»l during a spontaneous song with the characteristics of the conspecific calling song, which was elicited as an after effect of brain stimulation. The song contains two different kinds of sound pulses: 1) loud clicks and 2) soft pulses, presenting different spectra.The timbals, abdomen, tympana, folded membranes and opercula were tested as potential radiators of the song. The experiments included: 1) probe microphone measurements of the spectra of loud clicks and soft pulses in several positions around the animal and close to the body surface; 2) measurements of the spectra before and after covering with vaseline different structures that might be relevant to the radiation of the song, and manipulations of the size and shape of the abdominal and thoracic portions of the tracheal air sac; 3) laser vibrometry measurements in different parts of the body, both during singing and external sound stimulation.The data obtained demonstrate that several structures contribute differently to the radiation of clicks and soft pulses: 1) The timbals are the main radiators at frequencies around the dominant spectral peak, 10–11 kHz in clicks and 12–13 kHz in soft pulses; 2) The tympana are important in radiation of frequencies below and above the timbal peak, especially during the generation of soft pulses; 3) The abdomen is more activated during the generation of clicks, and is more important in the radiation of low frequencies around 5 kHz.Manipulations of the body cavities showed that neither the thoracic nor the abdominal portions of the air sac are critical for the song tuning. The large abdominal cavity do not seem to work as a Helmholtz resonator. We found no evidence that resonances inside this cavity should play an important role in enhancing sound radiation in T. gastrica.     

Combined data, Bayesian phylogenetics, and the origin of the New Zealand cicada genera

We have applied Bayesian and maximum likelihood methods of phylogenetic estimation to data from four mitochondrial genes (COI, COII, 12S, and 16S) and a single nuclear gene (EF1alpha) from several genera of New Zealand, Australian, and New Caledonian cicada taxa. We specifically focused on the heterogeneity of phylogenetic signal among the different data partitions and the biogeographic origins of the New Zealand cicada fauna. The Bayesian analyses circumvent many of the problems associated with other statistical tests for comparing data partitions. We took an information-theoretic approach to model selection based on the Akaike Information Criterion (AIC). This approach indicated that there was considerable uncertainty in identifying the best-fit model for some of the partitions. Additionally, a large amount of uncertainty was associated with many parameter estimates from the substitution model. However, a sensitivity analysis on the combined dataset indicated that the model selection uncertainty had little effect on estimates of topology because these estimates were largely insensitive to changes in the assumed model. This outcome suggests strong signal in our data. Our analyses support a New Caledonian affiliation of the New Zealand cicada genera Maoricicada, Kikihia, and Rhodopsalta and Australian affinities for the genera Amphipsalta and Notopsalta. This result was surprising, given that previous cicada biologists suspected a close relationship between Amphipsalta, Notopsalta, and Rhodopsalta based on genitalic characters. Relationships among the closely related genera Maoricicada, Kikihia, and Rhodopsalta were poorly resolved, the mitochondrial data and the EF1alpha data favoring different arrangements within this clade.     

A study of the abundance and patchiness of cicada nymphs (Homoptera: Tibicinidae) in a New Zealand subalpine shrub-grassland

Abstract

Cicada emergence skins in a subalpine shrub grassland have been sampled during 1969–75 to determine the abundance and spatial distributions of nymphs feeding on plant roots. A guild of six cicada species is primarily associated with two forms of vegetation: shrubs (Dracophyllum and Cassinia) and tall tussock (Chionochloa). Skin locations were mapped relative to dominant vegetation species, litter zones, and soil and rock pavements over a range of aspects, altitudes, and vegetation types, and sampling methods were scaled at four levels: the locality, plot, quadrat, and individual plant. There were significant differences in skin counts over four years, and different measures of mean skin densities are given for the four sampling scales. The two primary vegetation types had cumulative 1969–72 mean densities of 5.2 ± 4.0 and 12.9 ± 10.0 skins/quadrat (2.3 m²) , and the 1969–72 mean productivities of the upper 25% of quadrats (adjusted for percent ground cover) were, respectively, 5.5 and 35.5 skins/m². These productivities are believed to be conservative estimates of the maturing nymph numbers per individual host plant over the span of one cicada generation. Over a 17-year span, such productivities lie within the upper range of mean densities recorded for 17-year periodical cicadas in the United States. As the dominant subalpine vegetation species are very slow-growing,it is suggested that high densities of nymphs feeding on root sap may affect plant vitality, although 1971/1987 comparisons of vitality in 52 Chionochloa tussocks could not positively demonstrate a correlation across all data. Skin dispersion analyses indicated significant levels of patchiness, in agreement with other nymphal studies and with known cicada oviposition behaviour. No single dispersion model fitted the data comprehensively, and it is suggested that a gradual shifting of the centres of cicada aggregation may occur over a cumulative period of several generations.     

Competition both drives and impedes diversification in a model adaptive radiation

Competitors are known to be important in governing the outcome of evolutionary diversification during an adaptive radiation, but the precise mechanisms by which they exert their effects remain elusive. Using the model adaptive radiation of Pseudomonas fluorescens, we show experimentally that the effect of competition on diversification of a focal lineage depends on both the strength of competition and the ability of the competitors to diversify. We provide evidence that the extent of diversification in the absence of interspecific competitors depends on the strength of resource competition. We also show that the presence of competitors can actually increase diversity by increasing interspecific resource competition. Competitors that themselves are able to diversify prevent diversification of the focal lineage by removing otherwise available ecological opportunities. These results suggest that the progress of an adaptive radiation depends ultimately on the strength of resource competition, an effect that can be exaggerated or impeded by the presence of competitors.     

Tolerance defects in New Zealand Black and New Zealand Black X New Zealand White F1 mice

The susceptibility of autoimmune NZB and (NZB X NZW)F1 mice to the induction of tolerance by monomeric BSA was compared with several normal mouse strains. Unresponsiveness in T and B lymphocyte compartments was probed by challenging with DNP8BSA and measuring anti-DNP and anti-BSA antibodies separately. Tolerance induced by monomeric BSA was carrier specific, and there was no evidence of epitope-specific suppression. Normal NZW, NFS, and B10.D2 mice were easily rendered tolerant with monomeric BSA and did not produce anti-DNP or anti-BSA antibodies after challenge with DNP8BSA. By contrast, the lack of anti-DNP antibody response in similarly treated NZB mice was dependent on the dose of monomeric BSA, indicating that the helper T cells were partially resistant to tolerance induction. NZB mice treated with a high dose of monomeric BSA produced anti-BSA, but not anti-DNP, antibodies after immunization. Thus, the anti-carrier B cells in NZB mice may have been primed by monomeric BSA. The presence of the xid gene on the NZB background rendered the mice susceptible to induction of tolerance, suggesting that the tolerance defect in NZB mice involves the B cell compartment. This abnormal antibody response was a dominant trait: (NZB X NFS)F1 and (NZB X B10.D2)F1 mice had the same characteristics as NZB mice. These F1 hybrids do not develop autoimmune disease, indicating that resistance to experimental tolerance induction expressed at a B cell level may not be sufficient for disease development. In contrast to NZB and other NZB F1 hybrids, (NZB X NZW)F1 hybrids treated with monomeric BSA and challenged with DNP8BSA responded to both DNP and BSA. The contribution of a B cell defect to the tolerance abnormality of (NZB X NZW)F1 mice was examined by analyzing the effect of the xid gene on the progeny of (NZB.xid X NZW)F1 mice. Unlike the effect of the xid gene on NZB mice, both phenotypically normal heterozygous female and phenotypically xid hemizygous male mice produced anti-DNP and anti-BSA antibodies after tolerance induction and immunization, demonstrating that a major helper T cell abnormality was present in (NZB X NZW)F1 mice. The (NZW X B10.D2)F1 hybrid was rendered tolerant by this procedure, indicating that the helper T cell defect (NZB X NZW)F1 mice may have resulted from gene complementation with the NZB mice contributing partial resistance of T helper cells to tolerance induction.(ABSTRACT TRUNCATED AT 400 WORDS)     

Clade-specific morphological diversification and adaptive radiation in Hawaiian songbirds.

The Hawaiian honeycreepers are a dramatic example of adaptive radiation but contrast with the four other songbird lineages that successfully colonized the Hawaiian archipelago and failed to undergo similar diversification. To explore the processes that produced the diversity dichotomy in this insular fauna, we compared clade age and morphological diversity between the speciose honeycreepers and the comparatively depauperate Hawaiian thrushes. Mitochondrial-DNA-based genetic distances between these Hawaiian clades and their continental sister taxa indicate that the ancestral thrush colonized the Hawaiian Islands as early as the common ancestor of the honeycreepers. This similar timing of colonization indicates that the marked difference in diversity between the Hawaiian honeycreeper and thrush clades is unlikely to result from differences in these clades' tenures within the archipelago. If time cannot explain the contrasting diversities of these taxa, then an intrinsic, clade-specific trait may have fostered the honeycreeper radiation. As the honeycreepers have diversified most dramatically in morphological characters related to resource utilization, we used principal components analyses of bill characters to compare the magnitudes of morphological variation in the ancestral clades from which the Hawaiian honeycreeper and thrush lineages are derived, the Carduelini and Turdinae respectively. Although the Carduelini share a more recent common ancestor and have a lower species diversity than the Turdinae, these finch-like relatives of the honeycreepers exhibit significantly greater variation in bill morphology than do the continental relatives of the Hawaiian thrushes. The higher magnitude of morphological variation in the non-Hawaiian Carduelini suggests that the honeycreepers fall within a clade exhibiting a generally high evolutionary flexibility in bill morphology. Accordingly, although the magnitude of bill variation among the honeycreepers is similar to that of the entire passerine radiation, this dramatic morphological radiation represents an extreme manifestation of a general clade-specific ability to evolve novel morphologies.     

Stratification in a New Zealand rain forest

An undisturbed podocarp-broadleaved rain forest was sampled in eight strata (synusiae): canopy, small tree, shrub, low shrub, herb, ground, epiphyte and liane. Independent classifications of the quadrats were performed using the eight strata, and the classifications were correlated. Relations between strata were significant, but weak. Using records of plants of all ages, the relations largely reflected the presence of seedlings of woody species in the ground and herb strata. Using only records of species present as adults, the relations were quite different, and at least some seemed to reflect sociological interactions. Relations between a tree and a herb stratum was lower than in McCune & Antos' (1981) investigation, probably because of the narrow ecological range of the present study area.     

Nitrification in a New Zealand grassland soil

Summary The nitrifying population of a low-fertility New Zealand grassland soil was found to be very small and the soil did not accumulate NO₃-N when perfused in the laboratory with (NH₄)₂SO₄. The population of nitrifying bacteria, and the ability of the soil to nitrify on incubation, could be increased by field treatment with urea. The increased population developed in the presence of urea appeared to persist longer if lime was also applied to the soil. The limiting effect of substrate concentration on the population of nitrifying bacteria, which was observed in this soil, may help to explain the failure of some other grassland soils to accumulate NO₃-N.     

Trace elements in a New Zealand serpenting flora

Summary The trace element content of ashed specimens of a New Zealand serpentine flora and the associated soils was investigated. Six species (Myosotis monroi Cheesem.,Notothlaspi australe Hook. f.,Pimelea suteri Kirk,Cassinia vauvilliersii (Homb. et Jacq.) Hook. f. varserpentina Ckn. et Allan,Hebe odora (Hook. f.) Ckn. andLeptospermum scoparium J. R. et G. Forst.) were analysed for cobalt, chromium, copper and nickel by emission spectroscopy. The significance of the experimental data was evaluated by calculation of the correlation coefficients by a computer.C. vauvilliersii showed highly significant correlation between plant ash and soil concentration for chromium, cobalt and nickel.H. odora andL. scoparium showed similar but less pronounced correlations. Relative concentrations varied considerably among the species studied.P. suteri is a strong accumulator of nickel and cobalt andL. scoparium of chromium. Good correlations were observed for certain pairs of elements in the plant ash of individual species and in the soils alone. Data for uptake by plants were compared with soil extractabilities. Calcium-magnesium ratios were also determined, and were found to be much lower than in the same species growing on non-serpentinized soils. It was concluded that the above species, particularlyC. vauvilliersii will be useful in biogeochemical prospecting.     

The role of ecological opportunity in shaping disparate diversification trajectories in a bicontinental primate radiation

Exceptional species and phenotypic diversity commonly are attributed to ecological opportunity (EO). The conventional EO model predicts that rates of lineage diversification and phenotypic evolution are elevated early in a radiation only to decline later in response to niche availability. Foregut fermentation is hypothesized to be a key innovation that allowed colobine monkeys (subfamily Colobinae), the only primates with this trait, to successfully colonize folivore adaptive zones unavailable to other herbivorous species. Therefore, diversification rates also are expected to be strongly linked with the evolution of traits related to folivory in these monkeys. Using dated molecular phylogenies and a dataset of feeding morphology, I test predictions of the EO model to evaluate the role of EO conferred by foregut fermentation in shaping the African and Asian colobine radiations. Findings from diversification methods coupled with colobine biogeographic history provide compelling evidence that decreasing availability of new adaptive zones during colonization of Asia together with constraints presented by dietary specialization underlie temporal changes in diversification in the Asian but not African clade. Additionally, departures from the EO model likely reflect iterative diversification events in Asia.     

Shrub succession and invasibility in a New Zealand montane grassland

Abstract Two successive shrub invasions of a short tussock grassland induced by grazing and burning were examined in montane South Island, New Zealand. The first invasion was by a native shrub, matagouri (Discaria toumatou Raoul). The second invasion was by an exotic shrub, Scotch broom (Cytisus scoparius (L.) Link), which invaded the matagouri shrubland that had developed over the grassland. The invasions were investigated using analysis of spatial patterns of both shrubs and tussocks, and age, growth rates and size structure of the shrubs. Competition between the two shrub species was examined using spatial patterns and comparing allometric relationships. After initial invasion by matagouri of the grasslands, stand density increased by consolidation about its initial colonization points. Current matagouri distribution is often negatively associated with tussocks. Scotch broom occurs most frequently in a dense sward of introduced grasses and occasionally in tussocks in interstices among matagouri shrubs. Despite the palatability of Scotch broom to sheep that graze the site, there was no evidence that the spiny matagouri facilitates invasion by protecting Scotch broom seedlings; rather there was negative association between the shrub species. The two species probably compete for above-ground space. However, diameter and height growth rates of Scotch broom far exceed those of matagouri so Scotch broom is likely to increase in biomass rapidly at the site. The autogenic organization and disturbance history of the resident plant communities have rendered each vulnerable to successive invasions.     

Ecological opportunity and diversification in a continental radiation of birds: climbing adaptations and cladogenesis in the Furnariidae

Ecological theories of adaptive radiation predict that ecological opportunity stimulates cladogenesis through its effects on competitive release and niche expansion. Given that key innovations may confer ecological opportunity, we investigated the effect of the acquisition of climbing adaptations on rates of cladogenesis in a major avian radiation, the Neotropical bird family Furnariidae, using a species-level phylogeny. Morphological specializations for vertical climbing originated in the woodcreepers ～23 million years ago, well before that adaptation occurred in woodpeckers (Picidae) or in other potential competitors in South America. This suggests that the acquisition of climbing adaptations conferred ample ecological opportunity to early woodcreepers. Nonetheless, we found that increases in speciation rates in Furnariidae did not coincide with the acquisition of climbing adaptations and that the relationship between the accumulation of climbing adaptations and rates of speciation was negative. In addition, we did not detect a diversity-dependent decline in woodcreeper diversification rates consistent with saturation of the trunk-climbing niche. These findings do not support the hypothesis that ecological opportunity related to trunk foraging stimulated cladogenesis in this radiation. The negative effect of climbing on diversification may be mediated by an indirect positive effect of climbing on dispersal ability, which may reduce speciation rates over evolutionary timescales.     

Bryophyte ecology of a dune area in New Zealand

Summary and conclusions Bryophyte ecology has been little investigated in New Zealand. In the present study a northern dune area (under a dune reclamation and afforestation scheme) on the west coast, is divided into five community zones. Two of these are phases in the artificial sere leading from bare sand to exotic pine plantations. The others are seral stages in the development of the coastal forest climax.The bryophyte flora is investigated both quantitatively and qualitatively for the terrestrial, epixylic and corticolous habitat in each of these communities.It was found that mosses are not pioneers in the psammosere as is frequently the case in the northern hemisphere. They were secondary invaders at a late stage in the Lupinus-Psamma phase when the lupin bushes play an important part. The first bryophytes occupied epixylic stations (on logs and fallen branches). The bryophytic flora showed developmental changes in relation to the nature of the cover communities. Life form and drought tolerance of the bryophyte species are important factors. Long distance migration is by spores, but local dispersal by vegetative growth and the transportation of detached tufts is of great importance.The size and shape of quadrat for terrestrial communities is fully investigated. It was found that shape was of no essential importance in bryocoenological methods The heavy needle litter of the pine plantations had no retarding effect on the moss carpet. Succession within the bryophyte community is from hepatics to acrocarpic and then to pleurocarpic mosses.Corticolous mosses form a group apart and are affected by such factors as drainage patterns, nature of bark and exposure.The bryophyte union is worked out for each cover community and three terrestrial unions and one corticolous union are recognised. It is suggested that one of the terrestrial unions is dynamic and that basically there are two distinct terrestrial unions as a climax to the bryophyte microsere; one for the Leptospermum scrub and the other for coastal forest.My thanks are due to Prof. V. J. Chapman (Auckland University College N.Z.) for his advice and encouragement during the course of this investigation.

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Résumé Les dunes de sable très élevées sur la côte occidentale de la Nouvelle Zelande ont été fixées avec Psamma arenaria et Lupinus et plantées de Pins exotiques (Pinus radiata).Le versant Nord d'une dune a été étudié au point de vue du développement de la végétation. Ce versant comprend une partie plantée de Pinus et une autre abandonnée à l'évolution naturelle de la végétation.La flore bryophytique est divisée en trois catégories selon la station: Mousses vivant sur la terre nue, sur les arbres (Mousses corticoles) et sur le bois mort. Sur cette dune les Mousses n'apparaissent pas comme pionniers; elles s'installent après l'établissement de Lupinus d'abord sur des branches tombées (mortes).Les formes biologiques des différentes Bryophytes et leur résistance contre le desséchement ont été étudiées en rapport avec les types de végétation.Les spores des Mousses sont parfois apportées de très loin, mais dans le territoire même qui a été etudié la dispersion végétative par accroissement et par des parties détachées des touffes joue un grand rôle.Quelques expériments avec des carrés de différente surface montrent que la forme des surfaces étudiées est de peu d'importance pour l'étude bryosociologique.Même la litière épaisse sous le couvert du Pin ne retarde pas le développement des Mousses. Les Hépatiques apparaissent les premiers, suivies des Mousses acrocarpes et ensuite des Mousses pleurocarpes.Les Bryophytes corticoles forment une unité à part. On a discerné en tout quatre groupements, trois groupements terrestres et un groupement corticole. Un des trois groupements terrestres constitue probablement un stage de développement tandis que deux autres semblent être des groupements terminaux permanents: stades terminaux l'un pour la brousse à Leptospermum, l'autre pour la forêt littorale.

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This work was carried out by the author while staying at the Auckland University College, New Zealand.     

Superficial mycoses in a southern New Zealand district.

A total of 2,709 pathogenic fungi were isolated from 8,762 patients suspected as having mycotic disease, over an 8 year period in Christchurch, New Zealand. The district is climatically designated as temperate with average mean temperatures of 17 degrees C in summer and 8 degrees C in winter. The predominant species of fungi were relatively small in number with Trichophyton mentagrophytes var. interdigitals as the major pathogen. Fungi other than true dermatophytes, particularly Candida spp. and Malassezia furfur, were included to demonstrate the full spectrum of superficial mycoses presenting for diagnosis at the mycology clinic.     

Species interactions during diversification and community assembly in an island radiation of shrews

Background

Closely related, ecologically similar species often have adjacent distributions, suggesting competitive exclusion may contribute to the structure of some natural communities. In systems such as island archipelagos, where speciation is often tightly associated with dispersal over oceanic barriers, competitive exclusion may prevent population establishment following inter-island dispersal and subsequent cladogenesis.

Methodology/Principal Findings

Using a combination of tools, we test the hypothesis that the distributions of shrew (Crocidura) species in the Philippines are the result of competitive exclusion preventing secondary invasion of occupied islands. We first compare ecological niche models between two widespread, allopatric species and find statistical support for their ecological similarity, implying that competition for habitat between these species is possible. We then examine dispersion patterns among sympatric species and find some signal for overdispersion of body size, but not for phylogenetic branch length. Finally, we simulate the process of inter-island colonization under a stochastic model of dispersal lacking ecological forces. Results are dependent on the geographic scope and colonization probability employed. However, some combinations suggest that the number of inter-island dispersal events necessary to populate the archipelago may be much higher than the minimum number of colonization events necessary to explain current estimates of species richness and phylogenetic relationships. If our model is appropriate, these results imply that alternative factors, such as competitive exclusion, may have influenced the process of inter-island colonization and subsequent cladogenesis.

Conclusions/Significance

We interpret the combined results as providing tenuous evidence that similarity in body size may prevent co-occurrence in Philippine shrews and that competitive exclusion among ecologically similar species, rather than an inability to disperse among islands, may have limited diversification in this group, and, possibly other clades endemic to island archipelagos.     

Status and foraging in New Zealand honeyeaters

Abstract

Aggression is a common feature of sociality among nectar-feeding birds, and these have been used to consider many aspects of ecological theory, for example community structure, foraging patterns, social organisation and plant-pollinator systems.

Knowledge of aggression among and within New Zealand's honeyeater species is reviewed. Additional information on the importance of various asymmetric cues as learned predictors of status is considered. High-status individuals appear to gain access to nectar in all situations.

Honeyeaters are monogamous and the relationship between the sexes is examined. Even when mates are not formally associated, both appear to benefit from the presence of the other. Examples of the effect of status on pollination efficiency are also considered.

Workers are urged to consider status and individual differences if we are to increase our understanding of community structure, foraging and plant-pollinator interaction.