Polydomy in ants: what we know, what we think we know, and what remains to be done

The correct identification of colony boundaries is an essential prerequisite for empirical studies of ant behaviour and evolution. Ant colonies function at various organizational levels, and these boundaries may be difficult to assess. Moreover, new complexity can be generated through the presence of spatially discrete subgroups within a more or less genetically homogeneous colony, a situation called polydomy. A colony is polydomous only if individuals (workers and brood) of its constituent nests function as a social and cooperative unit and are regularly interchanged among nests. This condition was previously called polycalic, and the term polydomy was used in a broader sense for a group of daughter nests of the same mother colony (implying limited female dispersal), without regard to whether these different nests continued to exchange individuals. We think that this distinction between ‘polycaly’ and ‘polydomy’ concerns two disparate concepts. We thus prefer the narrower definition of polydomy, which groups individuals that interact socially. Does this new level of organization affect the way in which natural selection acts on social traits? Here, after examining the history of terms, we review all ant species that have been described as expressing polydomous structures. We show that there is no particular syndrome of traits predictably associated with polydomy. We detail the existing theoretical predictions and empirical results on the ecology of polydomy, and the impact of polydomy on social evolution and investment strategies, while carefully distinguishing monogynous from polygynous species. Finally, we propose a methodology for future studies and offer ideas about what remains to be done. © 2007 The Linnean Society of London, Biological Journal of the Linnean Society, 2007, 90 , 319–348.     

A PRELIMINARY REPORT ON THE ACOUSTIC COMMUNICATION IN URUGUAYAN CTENOMYS (RODENTIA,OCTODONTIDAE): BASIC SOUND TYPES

ABSTRACT

Subterranean rodents are interesting organisms for communication studies because of their fossorial way of life. Acoustic communication in the South American genus Ctenomys has not yet been studied even though this species is geographically widespread. This paper represents a preliminary survey of Ctenomys vocalizations. Three types of vocal signals were identified: S-, C- and G-signals. Using field, laboratory and literature data, we provide interpretations on the possible functions of these signals. S-signals are harsh and low-pitched putative spatial localization signals that may also encode for sexual identification. C-signals are relatively high-pitched and narrow-banded FM vocalizations that are sexual signals used by females in a copulatory context. Finally, G-signals are harsh and patternless sounds that are aggressive signals used in direct encounters with con- or hetero- specific individuals.     

Plastid terminal oxidase (PTOX) has the potential to act as a safety valve for excess excitation energy in the alpine plant species Ranunculus glacialis L.

Ranunculus glacialis leaves were tested for their plastid terminal oxidase (PTOX) content and electron flow to photorespiration and to alternative acceptors. In shade‐leaves, the PTOX and NAD(P)H dehydrogenase (NDH) content were markedly lower than in sun‐leaves. Carbon assimilation/light and C_i response curves were not different in sun‐ and shade‐leaves, but photosynthetic capacity was the highest in sun‐leaves. Based on calculation of the apparent specificity factor of ribulose 1·5‐bisphosphate carboxylase/oxygenase (Rubisco), the magnitude of alternative electron flow unrelated to carboxylation and oxygenation of Rubisco correlated to the PTOX content in sun‐, shade‐ and growth chamber‐leaves. Similarly, fluorescence induction kinetics indicated more complete and more rapid reoxidation of the plastoquinone (PQ) pool in sun‐ than in shade‐leaves. Blocking electron flow to assimilation, photorespiration and the Mehler reaction with appropriate inhibitors showed that sun‐leaves were able to maintain higher electron flow and PQ oxidation. The results suggest that PTOX can act as a safety valve in R. glacialis leaves under conditions where incident photon flux density (PFD) exceeds the growth PFD and under conditions where the plastoquinone pool is highly reduced. Such conditions can occur frequently in alpine climates due to rapid light and temperature changes.     

Cladoceran birth and death rates estimates: experimental comparisons of egg-ratio methods

I. Birth and death rates of natural cladoceran populations cannot be measured directly. Estimates of these population parameters must be calculated using methods that make assumptions about the form of population growth. These methods generally assume that the population has a stable age distribution.
2. To assess the effect of variable age distributions, we tested six egg ratio methods for estimating birth and death rates with data from thirty-seven laboratory populations of Daphnia pulicaria. The populations were grown under constant conditions, but the initial age distributions and egg ratios of the populations varied. Actual death rates were virtually zero, so the difference between the estimated and actual death rates measured the error in both birth and death rate estimates.
3. The results demonstrate that unstable population structures may produce large errors in the birth and death rates estimated by any of these methods. Among the methods tested, Taylor and Slatkin's formula and Paloheimo's formula were most reliable for the experimental data.
4. Further analyses of three of the methods were made using computer simulations of growth of age-structured populations with initially unstable age distributions. These analyses show that the time interval between sampling strongly influences the reliability of birth and death rate estimates. At a sampling interval of 2.5 days (equal to the duration of the egg stage), Paloheimo's formula was most accurate. At longer intervals (7.5–10 days), Taylor and Slatkin's formula which includes information on population structure was most accurate.     

Mobility, growth patterns and substrate in some fossil and Recent corals

The article analyses the relationships between mobile corals, the associated benthic fauna and the physical character of their substrates. Different types of coral mobility are here classified under three headings: (1) Passive rotation by water movement or by intervention of infaunal, benthic or nektic organisms. (2) Lifelong towing by a symbiotic sipunculid worm. (3) Auto-mobility, defined as self-induced movement which allows unburial, righting and lateral migration. In each case the morphology of the skeleton reflects the type of mobility, which can therefore be traced in the fossil record. Two examples of auto-mobile corals, Cycloseris (Recent) and Chomatoseris (= Anabacia) (Jurassic) are reviewed in detail; their main common architectural features are concentric growth and lack of epitheca. Both genera prefer loose, muddy sands. Mobility in corals allows them to flourish under circumstances unfavourable for sedentary forms. They are good indicators of loose, soft, sand substrates ranging from lagoonal through peri-reefal to deeper water environments. Though relatively few in species at any given time, mobile corals are geographically widespread and may be locally extremely abundant (>1500 per m²). World distribution maps are given for the Recent Cycloseris cyclolites, Diaseris distorta, Heteropsammia, Heterocyathus and Manicina areolata and for the Jurassic Chomatoseris. Cet article analyse Ies relations entre les coraux mobiles, la faune benthique associée et les propriétés physiques de leur substrat. On peut classer les différents types de mobilité chez les coraux selon trois catégories: (1) Rotation passive due aux mouvements de l'eau, à l'intervention de l'endofaune, d'organismes benthoniques ou nectoniques. (2) Remorquage par un ver Sipunculide symbiotique. (3) Auto-mobilité, définie comme mouvements propres, permettant au polypier de s'extraire du sédiment, de se retourner et de se déplacer latéralement. Dans tous les cas la morphologie du squelette est liée au type de mobilité qui peut done être reconnu chez les fossiles. Deux exemples de coraux auto-mobiles sont ici revus en détail: Cycloseris (actuel) et Chomatoseris (=Anabacia) (Jurassique); les traits communs entre ces deux formes sont la croissance concentrique et l'absence d'épithèque. Les deux genres préfèrent les sables boueux meubles. La mobilité chez les coraux permet leur épanouissement dans des circonstances défavorables aux formes sédentaires. Ce sont de bons indicateurs de fond meuble (sable ou sable vaseux). On les trouve dans les lagons, les zones péri-récifales et jusque dans des eaux plus profondes. Les genres mobiles, dont le nombre connu est encore faible, ont cependant une large distribution géographique et peuvent localement être représentés par de nombreux individus (>1500 par m²). Des cartes de répartition mondiale sont établies pour les coraux actuels Cycloseris cyclolites, Diaseris distorta, Heteropsammia, Heterocyathus, Manicina areolata et pour le genre jurassique Chomatoseris.     

Two approaches for the selection of Relevant Genetic Units for Conservation in the narrow European endemic steppe plant Boleum asperum (Brassicaceae)

Several methods based on population biology, biogeography, ecology, and genetics have been traditionally used for the identification of units for conservation below the species level. We use a combination of two methods based on population genetic structure estimators and on probabilities of loss of rare alleles to identify the Relevant Genetic Units for Conservation (RGUCs). The aims were to assess the genetic diversity and population structure of the endemic steppe plant Boleum asperum (Brassicaceae), and to determine how many and which populations significantly represent the total genetic diversity and the rarest allelic variation. Despite the high amplified fragment length polymorphism genetic diversity values detected in B. asperum ( h _T = 0.744), caused probably by its hexaploidy and allogamy, moderate spatial genetic differentiation was detected among populations (< 20%) and geographical ranges (> 13%), suggesting the existence of an ancestral continuous distribution range that was fragmented into separate 'islands' in more recent historical times. Five RGUCs, accounting for the 85.10% of the total genetic variation and representative of the entire geographical distribution of the species, were selected for in situ conservation. Ex situ conservation is proposed to complement the preservation of B. asperum . This method of objective selection of populations may be applied to other candidate taxa for conservation with prior adjustment of the threshold values of diversity required for effective protection of each particular species.  © 2008 The Linnean Society of London, Biological Journal of the Linnean Society , 2008, 94 , 341–354.     

Estimating the uncertainty in annual net ecosystem carbon exchange: spatial variation in turbulent fluxes and sampling errors in eddy-covariance measurements

Above forest canopies, eddy covariance (EC) measurements of mass (CO₂, H₂O vapor) and energy exchange, assumed to represent ecosystem fluxes, are commonly made at one point in the roughness sublayer (RSL). A spatial variability experiment, in which EC measurements were made from six towers within the RSL in a uniform pine plantation, quantified large and dynamic spatial variation in fluxes. The spatial coefficient of variation (CV) of the scalar fluxes decreased with increasing integration time, stabilizing at a minimum that was independent of further lengthening the averaging period (hereafter a ‘stable minimum’). For all three fluxes, the stable minimum (CV=9–11%) was reached at averaging times (τ_p) of 6–7 h during daytime, but higher stable minima (CV=46–158%) were reached at longer τ_p (>12 h) during nighttime. To the extent that decreasing CV of EC fluxes reflects reduction in micrometeorological sampling errors, half of the observed variability at τ_p=30 min is attributed to sampling errors. The remaining half (indicated by the stable minimum CV) is attributed to underlying variability in ecosystem structural properties, as determined by leaf area index, and perhaps associated ecosystem activity attributes. We further assessed the spatial variability estimates in the context of uncertainty in annual net ecosystem exchange (NEE). First, we adjusted annual NEE values obtained at our long‐term observation tower to account for the difference between this tower and the mean of all towers from this experiment; this increased NEE by up to 55 g C m^?2 yr^?1. Second, we combined uncertainty from gap filling and instrument error with uncertainty because of spatial variability, producing an estimate of variability in annual NEE ranging from 79 to 127 g C m^?2 yr^?1. This analysis demonstrated that even in such a uniform pine plantation, in some years spatial variability can contribute ～50% of the uncertainty in annual NEE estimates.     

Photosynthetic Carbon Reduction and Carbon Oxidation Cycles are the Main Electron Sinks for Photosystem II Activity During a Mild Drought

Stomatal closure can explain the inhibition of net CO₂ uptakeby a leaf subjected to a mild drought: the photosynthetic apparatusappears resistant to lack of water. Changes in both the watercontent of leaves maintained in a constant environment and theambient CO₂ molar fraction during measurements on well-hydratedleaves lead to similar effects on net CO₂ uptake and whole chainelectron transport as estimated by leaf chlorophyll fluorescencemeasurements. In particular, it is shown that photosystem II(PSII) functioning and its regulation are not qualitativelychanged during desiccation and that the variations in PSII photochemistrycan simply be understood by changes in substrate availabilityin this condition. Moreover, an analysis of the literature showsthat when inhibition of net CO₂ uptake by C₃ leaves under drought(Phaseolus vulgaris L., Helianthus annus L. and Solanum tuberosumL.) was lower than 80 %, elevated CO₂ completely restored thephotosynthetic capacity. The CO₂ molar fraction in the chloroplastsdeclines as stomata close in drying leaves. As a consequence,in C₃ plants, ribulose-1,5-bisphosphate oxygenation increasesand becomes the main sink for photosynthetic electrons. Dependingon the prevailing photon flux density, the O₂ uptake throughphotorespiratory activity can entirely replace carbon dioxideas an electron acceptor, or not. The rate of the Mehler reactionremains low and unchanged during desiccation. However, droughtcould also involve CO₂-sensitive modification of the photosyntheticmetabolism depending on plant growth conditions and possiblyalso on plant species.     

Groundwater rise,soil salinization and the decline of Casuarina in southeastern Australia during the late Quaternary

Abstract The decline in interglacial importance of Casuarina over the late Quaternary across southeastern Australia is documented. Three previously proposed causes for the decline (change in fire regime, change to a wetter climate and competitive exclusion by eucalypts) are shown to be inadequate for explaining the majority of cases. Re-examination of the evidence shows the decline at most sites occurred synchronously with a rise in groundwater or soil salinization, or both. From a review of biological literature, it is established that Casuarina stricta, the main species considered to have been affected by the decline, is likely to be disadvantaged by high water tables and saline soils. A link is demonstrated between groundwater salinity and the nodulation status of Casuarina in Victoria. It is concluded that the late Quaternary Casuarina decline was caused by a combination of rising groundwater levels and soil salinization. Soil salinization and groundwater level must therefore be considered as major factors determining vegetation patterns in southeastern Australia through the Quaternary up to the present day.     

Taxonomic revision, phylogenetic analysis, and biogeography of the bee genus Tropidopedia (Hymenoptera, Apidae, Tapinotaspidini)

The species of the bee genus Tropidopedia stat. nov. are revised. Thirteen new species are proposed: T. carinata sp. nov. , T. caracicola sp. nov. , T. danunciae sp. nov. , T. duckeana sp. nov. , T. eliasi sp. nov. , T. flavolineata sp. nov. , T. friesei sp. nov. , T. japuraensis sp. nov. , T. nigrita sp. nov. , T. nigrocarinata sp. nov. , T. ornata sp. nov. , T. peruana sp. nov. and T. venezuelana sp. nov. Taxonomic notes are provided for another four species: Tropidopedia punctifrons (Smith, 1879) comb. nov. , T. pallidipennis (Friese, 1899) comb. nov. , T. seabrai (Michener & Moure, 1957) and T. arcuatilis (Vachal, 1909) comb. nov. , including designation of a lectotype for Tetrapedia arcuatilis Vachal. An identification key, illustrations for main diagnostic characters, and distributions maps for all species are provided. A phylogenetic analysis was carried out to evaluate the monophyly of Tropidopedia and its main species groups, as well as to position it among the related genera. Biogeographical patterns are discussed.  © 2007 The Linnean Society of London, Zoological Journal of the Linnean Society , 2007, 151 , 511–554.