Trophic ecology of parabiotic ants: Do the partners have similar food niches?

Organisms associated with another species may experience both costs and benefits from their partner. One of these costs is competition, which is the more likely if the two species are ecologically similar. Parabioses are associations between two ant species that share a nest and often attend the same food sources. Albeit parabioses are probably mutualistic, parabiotic partners may compete for food. We therefore investigated feeding niches and dietary overlap of two parabiotically associated ants in Borneo using cafeteria experiments and stable isotope analyses. The two species strongly differed in their food choices. While Crematogaster modiglianii mostly foraged at carbohydrate‐rich baits, Camponotus rufifemur preferred urea‐rich sources. Both species also consumed animal protein. The ¹⁵N concentration in Ca. rufifemur workers was consistently lower than in Cr. modiglianii. Camponotus rufifemur but not Cr. modiglianii possesses microbial endosymbionts, which can metabolize urea and synthesize essential amino acids. Its lower ¹⁵N signature may result from a relatively higher intake of plant‐based or otherwise ¹⁵N‐depleted nitrogen. Isotopic signatures of the two partners in the same parabiosis showed strongly parallel variation across nests. As we did not find evidence for spatial autocorrelation, this correlation suggests an overlap of food sources between the two ant species. Based on model simulations, we estimated a diet overlap of 22–66% for nitrogen sources and 45–74% for carbon sources. The overlap may arise from either joint exploitation of the same food sources or trophallactic exchange of food. This suggests an intense trophic interaction and potential for competition between the parabiotic partners.     

Molecular phylogeny of Anomalodesmata (Mollusca: Bivalvia) inferred from 18S rRNA sequences

The origin of the anomalodesmatan bivalves and the relationships of the constituent families are far from being settled. Phylogenetic uncertainties result from the morphological heterogeneity of the Anomalodesmata and from parallel/convergent evolution of several character complexes due to similar life habits. Here, we assess these problems with 26 near-complete anomalodesmatan 18S rRNA sequences from 12 out of 15 families and a selection of heteroconch outgroup taxa. The robustly monophyletic Anomalodesmata share insertions in the V2 and V4 expansion regions. Both parsimony and maximum-likelihood analyses confirm their position among the basal heterodonts rooting between Carditidae and Lucinidae or, together with the latter, between Carditidae and the remaining Heterodonta. There is no support for monophyletic Myoida, nor for a close relationship of Anomalodesmata with any myoid taxon. At the base of the Anomalodesmata is an unstable cluster of long-branch species belonging to the Poromyidae, Verticordiidae, Lyonsiellidae and Thraciidae. The remaining Anomalodesmata split consistently but with varying branch support into three major clades: the Cuspidariidae excluding Myonera ; a 'thraciid' clade consisting of (Euciroidae, ( Myonera ( Thracia, Cleidothaerus , Myochamidae))); and a 'lyonsiid' clade with Laternulidae, Pandoridae, diphyletic Lyonsiidae due to a robust clade of Lyonsia norwegica and the clavagellid Brechites vaginiferus . Tests of various alternative topologies showed that all are significantly longer but optimal likelihood trees with monophyletic carnivorous taxa and/or Thraciidae are not significantly less likely. These results differ greatly from previous morphological studies. Palaeontological data and homology decisions for selected characters are evaluated in the light of the molecular trees.  © 2003 The Linnean Society of London, Zoological Journal of the Linnean Society , 2003, 139 , 229–246.     

Phylogenetic analysis of the Pinnotheridae (Crustacea, Brachyura) based on larval morphology, with emphasis on the Dissodactylus species complex

Comparative larval morphology was used to elucidate phylogenetic relationships within the Pinnotheridae and the Dissodactylus species complex. Within the family, seven zoeal and six megalopal characters suggested two equally parsimonious phylogenetic hypotheses for pinnotherid larvae, both with Ostracotheres tridacnae representing the sister group for the Dissodactylus complex. Results indicated that the genus Pinnotheres is a polyphyletic taxon, and that the traditional subfamilial arrangement comprises paraphyletic taxa within the subfamilies Pinnotherinae and Pinnothereliinae. Certain evidence has suggested that Fabia and Juxtafubia should be excluded from the Pinnotherinae and placed into the Pinnothereliinae. Larval and adult morphology suggested that Pinnotheres politus should be included within Tumidotheres. The phylogenetic analysis within the Dissodactylus complex involved one zoeal and 16 megalopal characters. Results suggested a single phylogenetic hypothesis based on larval morphology. Combining adult morphology with larval evidence resulted in two equally parsimonious phylogenetic hypotheses, one of which agreed with a previously suggested hypothesis based only on adult characters.     

Water relations and carbon gain are closely related to cushion size in the moss Grimmia pulvinata

The present study of structural and physiological changes during the development of the cushion moss, Grimmia pulvinata , quantifies the size-dependence of various parameters of water relations such as changes in surface: volume ratio ( S/V ) or water loss rates, and also measures net CO₂ gas exchange in the light and the dark. Larger cushions had lower S/V values than smaller ones and featured lower rates of area-based evapotranspiration, owing to higher boundary-layer resistance, but did not differ in relative water storage capacity (expressed as a percentage of d. wt). In combination, this leads to considerably longer hydration periods in larger cushions. By contrast, CO₂ gas-exchange parameters were negatively correlated with size : larger cushions showed significantly lower (mass-based) rates of net photosynthesis and dark respiration. Using these data, we estimated carbon budgets during a drying cycle as a function of cushion size. When including alternations of dark and light periods, the relationship proved to be rather complicated. Depending on the time of hydration, net carbon budgets not only varied quantitatively with size but sometimes took on both positive and negative values depending on cushion size. We conclude that neglecting plant size can lead to unrepeatable or even misleading results in comparative ecophysiological studies, and therefore urge for adequate attention to be paid to size in these studies.     

Ecological adaptations of grassland‐inhabiting flightless Orthoptera: Fulvoscirtes and Acanthoscirtes,two new genera of African Karniellina (Orthoptera,Tettigoniidae, Conocephalinae,Conocephalini)

Two new genera, Fulvoscirtes n.gen. and Acanthoscirtes n.gen. , are established within the subtribe Karniellina of Conocephalini. Fulvoscirtes is based on Xiphidion kilimandjaricum Sjöstedt, 1909 and Acanthoscirtes on Phlesirtes kevani Chopard from northern Kenya. The majority of Fulvoscirtes spp. are confined to open grasslands in the submontane zone of mountains. Fulvoscirtes contains eight species, seven of which are newly described in this paper. Three species and one subspecies occur on Mt Kilimanjaro. These are F. kilimandjaricum (Sjöstedt) constricted to the southern slopes, F. legumishera n.sp. confined to the northern side and F. sylvaticus n.sp. occurring on the western side of Kilimanjaro and on the eastern slopes of Mt Meru. Fulvoscirtes fulvus n.sp. is divided into two subspecies, F. fulvus fulvus n.ssp. found in the submontane zone of east Kilimanjaro and F. fulvus parensis n.ssp. in submontane to montane localities of the North and South Pare mountains. Fulvoscirtes fulvotaitensis n.sp. occurs in the Taita Hills of southern Kenya. Fulvoscirtes viridis n.sp. is described from savannah habitats between Mts Longido and Meru. Fulvoscirtes laticercus n.sp. is found in the Kenyan highlands, while the most southerly occurring species, Fulvoscirtes manyara n.sp. , is found on Mt Hanang and the Mbulu highlands of northwestern Tanzania. Acanthoscirtes contains three species, of which A. albostriatus n.sp. is described newly from savannah habitas of eastern Kilimanjaro. Information is given on the ecology and the acoustic behaviour of some of the species together with keys to the genera of the Karniellina and the species of Fulvoscirtes and Acanthoscirtes. The genera of Karniellina probably evolved at a time when grasslands spread in East Africa due to an increasing aridification of the climate. The earliest lineage, the genus Karniella, is adapted to more forested habitats while the majority of the genera of Karniellina prefer open grasslands. Major splits within Karniellina probably occurred with the emergence of savannah grasslands due to the ongoing fragmentation of forest habitats several millions years ago, but most species within the genera are geologically young, their radiation being boosted by climatic fluctuations of the past 1–2 Ma.     

A new genus of African Karniellina (Orthoptera,Tettigoniidae, Conocephalinae,Conocephalini): integrating morphological,molecular and bioacoustical data

Melanoscirtes gen.n. is established within Karniellina. The members of this subtribe are small conocephaline bush crickets, confined to Africa. Melanoscirtes is erected on Phlesirtes kibonotensis, a species restricted to forest clearings and forest edge in the submontane and montane zones of Mt. Kilimanjaro. A subspecies, M. kibonotensis uguenoensis, is described from the North Pare mountains, a mountain range of the Eastern Arc adjacent to Mt. Kilimanjaro. Further species of Melanoscirtes occur on other mountain ranges of the northern branch of the Eastern Arc mountains of northern Tanzania and southern Kenya. The South Pare mountains harbour M. shengenae; the West Usambaras, M. usambarensis, and the Taita Hills, M. taitensis. All species and subspecies of Melanoscirtes exhibit a similar morphology and occupy analogous habitats on the respective mountains. The song patterns for all species found within this genus are very similar, and this, together with evidence from molecular data, suggests that allopatric speciation is the reason for the biogeographic pattern found in this genus. A key for the subspecies and species of Melanoscirtes is provided.     

Phylogeny and biogeography Eupholidoptera Mařan (Orthoptera,Tettigoniidae): morphological speciation in correlation with the geographical evolution of the eastern Mediterranean

Recently, the systematics and biogeography of the Mediterranean biota have received much attention. This paper deals with Eupholidoptera Ma?an, a Mediterranean lineage of Tettigoniidae. The genus is restricted to the northern and eastern basin of the Mediterranean, with a significant number of species found on the Aegean islands. To produce a phylogeny and use it to make assumptions about the historical biogeography of Eupholidoptera, material of 46 species from several collections was studied. A phylogenetic analysis based mainly on morphological characters suggested two lineages in the genus: the E. chabrieri and the E. prasina groups. Based on the consistency between historical geographical events and branching events on the phylogenetic tree, Eupholidoptera is assumed to have evolved from an ancestor present in the Aegeid plate in the Mid‐Miocene. The division of the Aegeid plate into Anatolia and Greece in the Tortonian, the reoccurrence of terrestrial corridors between these mainlands in the Messinian, the regression of the Aegean area in the Pliocene and sea level changes in the Pleistocene are assumed to have been the main palaeogeographical events directing speciation in Eupholidoptera. As most of the species are allopatric, vicariance is suggested to be the main pattern. By combining the nature of the characters used in the phylogenetic analysis, the phylogenetic tree produced and the biogeographical assumptions, four tentative conclusions can be made: (i) radiation in the genus is a result of divergence in morphology; (ii) because the main character source is male genitalia, there has possibly been intensive sexual selection, which leads to morphological speciation; (iii) as the difference in temporal parameters of the song is prominent in sympatric/parapatric species pairs only, co‐occurrence is suggested to be the main reason driving divergence in the song; (iv) there seems to be a negative correlation between the size of the distribution range and the evolutionary rate in speciation; this may be the reason why the E. prasina group (restricted to a small part of the range of the genus) is more diverse than the E. chabrieri group, which is distributed over the entire range.     

Growth and phenology of mature temperate forest trees in elevated CO2

Are mature forest trees carbon limited at current CO₂ concentrations? Will ‘mid‐life’, 35 m tall deciduous trees grow faster in a CO₂‐enriched atmosphere? To answer these questions we exposed ca. 100‐year‐old temperate forest trees at the Swiss Canopy Crane site near Basel, Switzerland to a ca. 540 ppm CO₂ atmosphere using web‐FACE technology. Here, we report growth responses to elevated CO₂ for 11 tall trees (compared with 32 controls) of five species during the initial four treatment years. Tested across all trees, there was no CO₂ effect on stem basal area (BA) increment (neither when tested per year nor cumulatively for 4 years). In fact, the 4th year means were almost identical for the two groups. Stem growth data were standardized by pretreatment growth (5 years) in order to account for a priori individual differences in vigor. Although this experiment was not designed to test species specific effects, one species, the common European beech, Fagus sylvatica, showed a significant growth enhancement in the first year, which reoccurred during a centennial drought in the third year. None of the other dominant species (Quercus petraea, Carpinus betulus) showed a growth response to CO₂ in any of the 4 years or for all years together. The inclusion or exclusion of single individuals of Prunus avium and Tilia platyphyllos did not change the picture. In elevated CO₂, lateral branching in terminal shoots was higher in Fagus in 2002, when shoots developed from buds that were formed during the first season of CO₂ enrichment (2001), but there was no effect in later years and no change in lateral branching in any of the other species. In Quercus, there was a steady stimulation of leading shoot length in high‐CO₂ trees. Phenological variables (bud break, leaf fall, leaf duration) were highly species specific and were not affected by elevated CO₂ in any consistent way. Our 4‐year data set reflects a very dynamic and species‐specific response of tree growth to a step change in CO₂ supply. Stem growth after 4 years of exposure does not support the notion that mature forest trees will accrete wood biomass at faster rates in a future CO₂‐enriched atmosphere.